Land Use History Research Papers (original) (raw)

A 9000 cal. year record of geochemistry was analysed in a sediment core obtained from a Swiss alpine hard-water lake (1937 m a.s.l.) that is located at the present-day tree-line. Geochemical stratigraphies are compared to changes in... more

A 9000 cal. year record of geochemistry was analysed in a sediment core obtained from a Swiss alpine hard-water lake (1937 m a.s.l.) that is located at the present-day tree-line. Geochemical stratigraphies are compared to changes in mineralogy, grain-size, pollen, and macrofossil records. This allows the reconstruction of the effects of changes in vegetation and of 3500 years of land-use in the catchment area on sediment geochemistry. Using principal component analysis, two major geochemical groups are distinguished: (i) Changes in concentrations of Rb, Ti, Zr, Fe, As, and Pb are closely related to corresponding changes in the concentrations of quartz and clay. They are thus considered to represent the silicate fraction which shows an increase from the oldest to the youngest core section. (ii) In contrast, Ca and Sr concentrations are positively correlated with changes in silt, sand, and calcite. They are therefore considered to represent the carbonate fraction which gradually decreased. Based on constrained cluster analysis, the core is divided into two major zones. The oldest zone (A; 9000-6400 cal. BP) is characterised by high concentrations of detrital carbonates. The more open catchment vegetation at that time promoted the physical weathering of these carbonates. The second major zone (B, 6400 cal. BP-1996 AD) is divided into four subsections with boundaries at ca. 3500, 2400, and 160 cal. BP. The lower part of this zone, B1, is characterized by a gradual decrease in the carbonate-silt fraction and a pronounced increase in the silicate-clay fraction. This is concurrent with the expansion of Picea in the catchment area, which probably stabilized the soil. The middle part, B2 and B3 (3500-160 cal. BP), comprises pronounced fluctuations in all elements, especially Ca, Sr, Mn, and Rb, but also in clay and silt. These changes are related to varying intensities of alpine farming. In the same section, Mn/Fe ratios are highly variable, suggesting changes in the mixing regime of the lake with phases of anoxic bottom water. The uppermost section, B4 (since 160 cal. BP), is characterized by a steep decline in the silicate fraction and an increase in Ca and Sr. Despite the decrease in the silicate fraction, Pb increases, due to elevated atmospheric input resulting from early metal pollution, are masked by the high natural variability. Generally, changes in vegetation, which correspond to climate changes in the early Holocene and to human activities since ca. 3700 cal. BP, are the controlling factor for variations in the geochemical composition of the sediment of Sägistalsee. This is the sixth in a series of eight papers published in this special issue dedicated to the palaeolimnology of Sägistalsee. Drs. André F. Lotter and H. John B. Birks were the guest editors of this issue.

Past regeneration patterns of Quercus robur L. and Fagus sylvatica L. and their relationship to canopy structure, disturbances and forest-use history were investigated in an old-growth, lowland forest in Cantabria, Northern Spain.... more

Past regeneration patterns of Quercus robur L. and Fagus sylvatica L. and their relationship to canopy structure, disturbances and forest-use history were investigated in an old-growth, lowland forest in Cantabria, Northern Spain. Dendroecological techniques were used to estimate tree ages and reconstruct disturbance histories in four representative stands which differed in composition and structure. Age estimates and tree locations were used to reconstruct patterns of tree establishment. Documentary sources were also used to report on changes in land-use during the past 250 years. Age structures of both species were discontinuous in time and space, and revealed two main cohorts distributed in even-aged, spatially segregated patches. Juveniles showed a clumped spatial pattern at varying distances, indicating an establishment in more or less extensive patches. Establishment site analyses revealed that Q. robur regenerated in canopy gaps, while F. sylvatica recruited throughout the forest floor, but it displayed inhibition near mature conspecifics. A lack of tree establishment from the 1840s to the 1920s coincided with an intense grazing pressure from domestic animals. F. sylvatica exhibited continuous recruitment in periods of forest protection against grazing, such as from the 1740s to the 1830s and from the 1920s. By contrast, Q. robur recruitment was dependent on both low grazing intensities and disturbances that resulted in the expansion of existing canopy openings, as occurred in 1943, 1956 and 1967. Past selective cuttings, canopy closure and forest protection could be responsible for the increasing decline of oak dominance. Planting Q. robur and controlling F. sylvatica regeneration are therefore advisable to prevent the complete domination of beech in the future forest canopy.

Land use change Forest regeneration pattern Spatially-explicit model a b s t r a c t In addition to the effects of climate change, land use change is expected to trigger dynamic processes that may shift alpine tree lines upwards. To gain... more

Land use change Forest regeneration pattern Spatially-explicit model a b s t r a c t In addition to the effects of climate change, land use change is expected to trigger dynamic processes that may shift alpine tree lines upwards. To gain a conceptual understanding of the spatio-temporal processes shaping tree line patterns, we developed an individual-based and spatially-explicit model of spontaneous forest regeneration at the alpine tree line. Remote sensing data were integrated with the succession processes for individual trees in an object based image analysis approach. The model presented here predicts patterns of natural forest regeneration on a summer pasture in the Austrian Central Alps between 1954 and 2006. Different model scenarios are compared to the actual forest regeneration during the study period to validate the model's structure and its sensitivity to changing input parameters. The model's main process parameters are tested in four scenarios: A baseline scenario with the most likely input parameters derived from empirical studies in the literature; and three scenarios with differing parameters for seed production, seed dispersal kernel, and seedling competition with the ground vegetation. The tests largely confirm the model's formulation. The baseline scenario correctly predicts a significant upwards shift of the tree line elevation. Moreover it is demonstrated that (1) fecundity is a crucial factor in the expansion of forest into open land, (2) land cover and land use history have a significant impact on the emergence of forest regeneration patterns and (3) the dispersal kernel of Norway spruce has a long-distance component. We thus identified the key processes operating under environmental change from the characteristics of spatial changes in tree line patterns over the last 50 years.

The isolated Easter Island (Rapa Nui) is an outstanding example of land degradation caused by land use in a sensitive ecosystem. The focus of the investigation was placed on Poike peninsula, the most eastern part of Rapa Nui. While Poike... more

The isolated Easter Island (Rapa Nui) is an outstanding example of land degradation caused by land use in a sensitive ecosystem. The focus of the investigation was placed on Poike peninsula, the most eastern part of Rapa Nui. While Poike peninsula was once supplied with fertile soils, in large areas desertification takes place today. Detailed analysis of soil profiles allowed the reconstruction of the history and of causes and effects of soil erosion and gullying in the context of land use history and cultural evolution. The results of the stratigraphic analysis prove that from the beginning of human settlement around AD 300/600 until AD 1280 the agriculture on Poike peninsula was characterised by sustainable land use and a traditional type of agro-forestry. Soil erosion was not significant. At around AD 1280 the woodland on Poike, dominated by the endemic palm Jubaea sp., was cleared by slashing and burning. Intensive farming on the upper slopes of the volcanic peninsula resulted in sheet erosion lasting until the 20th century. Settlements and ceremonial places which were built around AD 1300 on downslope areas were buried soon by sediments. Agriculture ceased around AD 1400 on downslope areas as the fertile soils were completely eroded. From AD 1400 until the late 19th century sheet erosion and the accumulation of fine-layered sediments migrated upslope. On average 8.6 Mg of soil per hectare and per year were reworked by erosion (eroded and accumulated within the catchment). Gullying began on Rapa Nui with the sudden increase in the number of sheep during the early 20th century. Gullies are still developing on the island and their ongoing enlargement created extended badlands on Poike which pose a significant problem for ecological and archaeological conservation strategies. Gullying rates exceed 190 Mg ha À 1 y À 1 .

In tropical Latin America, pasture land for extensive grazing continues to expand, mostly at the expense of forest cover. Until now, scientists and policy makers tackling this issue had no geographically exhaustive information at the... more

In tropical Latin America, pasture land for extensive grazing continues to expand, mostly at the expense of forest cover. Until now, scientists and policy makers tackling this issue had no geographically exhaustive information at the continental level about the spatial dynamics of this process. On the basis of a land use change-modeling framework we made a projection of potential land use changes for the year 2010.

Peatlands act as CO 2 sinks that store more soil carbon per unit area than any other ecosystem. Increased aeration and subsequent oxidation following drainage causes peatlands to lose carbon and leads to a relative increase in the... more

Peatlands act as CO 2 sinks that store more soil carbon per unit area than any other ecosystem. Increased aeration and subsequent oxidation following drainage causes peatlands to lose carbon and leads to a relative increase in the concentration of inorganic compounds. To infer carbon losses as a result of drainage, we studied four sites in Central Europe with different drainage states and land-use histories. We used differences in ash content of both catotelm peat and near-surface layers as well as the results of soil carbon inventories. The method yielded reasonable results, at least for two drained sites, where the mean loss rates varied between 0.14 and 0.49 kgC m −2 a −1 .

We present a regional land-use history of the Palouse bioregion of southeastern Washington and west-central Idaho. Our objectives were to develop a history of European-American settlement and biological diversity in the region and use... more

We present a regional land-use history of the Palouse bioregion of southeastern Washington and west-central Idaho. Our objectives were to develop a history of European-American settlement and biological diversity in the region and use this history to understand how human activities have altered the land cover and ecological integrity of the Palouse bioregion. We compiled and interpreted available information on

Given the extent of land use and land cover change by humans on a global scale, conservation efforts have increasingly focused on restoring degraded ecosystems to provide ecosystem services and biodiversity. Many examples in the tropics... more

Given the extent of land use and land cover change by humans on a global scale, conservation efforts have increasingly focused on restoring degraded ecosystems to provide ecosystem services and biodiversity. Many examples in the tropics and elsewhere, however, show that some ecosystems recover rapidly without human intervention which begs the question of in which cases and to what extent humans should actively work to facilitate ecosystem recovery. We recommend that all land managers consider a suite of ecological and human factors before selecting a restoration approach. Land managers should first consider what the likely outcome of a passive restoration (natural regeneration) approach would be based on the natural ecosystem resilience, past land-use history, and the surrounding landscape matrix. They should also identify the specific goals of the project and assess the resources available. Conducting these analyses prior to selecting restoration approaches should result in a more efficient use of restoration resources both within and among projects and should maximize the success of restoration efforts.

Historical, meteorological, archaeological, and geological evidence support detailed reconstructions of how Spanish land-use practices affected the environment around the inland Chumash village of Talepop in the Santa Monica Mountains of... more

Historical, meteorological, archaeological, and geological evidence support detailed reconstructions of how Spanish land-use practices affected the environment around the inland Chumash village of Talepop in the Santa Monica Mountains of southern California. Initiation of Spanish farming and grazing around Talepop in 1801 followed by droughts between 1807 and 1810 defoliated the hillsides and triggered dustbowl-like conditions. Heavy rains in 1811 eroded the barren hills leading to massive floods in the valleys below. Chumash at Talepop adjusted to Spanish occupation by incorporating non-native plants and animals into their diet, but ultimately the changes overwhelmed them, and they abandoned the village.

During the last few decades, many case studies focused on the dynamics of fluvial systems in response to hillslope erosion, land-use impact, and climate changes. This paper will review the current state of knowledge of the dynamics of... more

During the last few decades, many case studies focused on the dynamics of fluvial systems in response to hillslope erosion, land-use impact, and climate changes. This paper will review the current state of knowledge of the dynamics of past soil erosion and gullying in small catchments (< 1 km2), the effects to adjacent fluvial systems and possible feedback mechanisms to land-use changes for the last 7000 years in central Europe. The discussed studies were made on hillslopes and gully systems in low mountain range areas. They are characterised by coupled slope–channel systems as well as uncoupled systems like closed depressions in Pleistocene lowlands, maars, lakes, and sunken areas. The studies show that sediment fluxes in small catchments are highly sensitive to local land-use changes while river sediments show regional trends in land-use and climate changes. Peaks of soil erosion and gullying took place during phases of rapid climate change. Particularly, extreme precipitation events caused intensive runoff on slopes used for agriculture. The most remarkable phases occurred in the first half of 14th and in the mid-18th to the early 19th century. Most of the gully systems in Europe today are a result of these catastrophic occurrences. These punctuated events triggered land abandonment and influenced the ecosystem and the socio-economic situation. The results imply that a future increase in land-use intensity and extreme precipitation events during climatic change might have severe consequences regarding soil erosion, flood risk, and ecological aspects.

The study of charcoal produced by five burning episodes that occurred in a rapid succession within a ritual pit dating to the late Iron Age at Raffin Fort, Co. Meath, Ireland, reveals considerable variation in the charcoal assemblages... more

The study of charcoal produced by five burning episodes that occurred in a rapid succession within a ritual pit dating to the late Iron Age at Raffin Fort, Co. Meath, Ireland, reveals considerable variation in the charcoal assemblages resulting from each burning episode. Wood selection processes are considered against the background of information on woodland composition and land-use history provided by a detailed pollen diagram from nearby Emlagh Bog, the chronology of which is based on both AMS 14 C dates and tephra analysis. A human skull fragment lay on top of the charcoal layers but the radiocarbon evidence indicates that the skull predated the burnings by at least a century. This and other evidence indicate a ritual pit with the skull as a human relic. It is suggested that, in this instance, wood selection was neither random nor determined solely by availability or combustibility, but instead may have been informed by socio-religious belief systems pertaining to trees and wood. Early Irish documentary sources, which reveal a complex ethnography of wood and trees in later prehistoric and early historic Ireland, are reviewed. The results shed fresh light on aspects of late Iron Age archaeology in a part of Europe that was outside the direct influence of the Roman world. New information is provided on a distinctive feature in late Holocene Irish pollen records namely the Late Iron Age Lull (ca. a.d. 1-500). During this time, widespread regeneration of woody vegetation took place. In the subsequent early Medieval period renewed farming activity resulted in substantial decline in woodland, a pattern also seen at many other locations in Ireland.

We assessed earthworm species composition and abundance during secondary succession at the Smithsonian Environmental Research Center, Maryland, USA. Land use history is well known at this site. Adjacent forest stands of different ages and... more

We assessed earthworm species composition and abundance during secondary succession at the Smithsonian Environmental Research Center, Maryland, USA. Land use history is well known at this site. Adjacent forest stands of different ages and other vegetation patches were sampled in 1998e99 and in 2006. Out of the 12 species three (Eisenoides loennbergi, Bimastos palustris, Diplocardia caroliniana) were native, the rest were European peregrine earthworms. Native species were mainly found in mature forests, otherwise the species composition of mature and successional stands was similar. Earthworm density and biomass was significantly higher in the successional forests, than in the mature forests, and this pattern appears to be stable at a decadal time scale. Two smaller stands that have never been clearcut did not harbor any earthworms. The forest floor on these sites had a thick organic layer, moder humus and low pH. Bulk density was highest in the youngest (50e70 years) forests. It appears that as the forests enter to a late successional stage (150 years), they no longer can support high abundance of litter feeding earthworms.

Landscape change occurs through the interaction of a multitude of natural and human driving forces at a range of organisational levels, with humans playing an increasingly dominant role in many regions of the world. Building on the... more

Landscape change occurs through the interaction of a multitude of natural and human driving forces at a range of organisational levels, with humans playing an increasingly dominant role in many regions of the world. Building on the current knowledge of the underlying drivers of landscape change, a conceptual framework of regional landscape change was developed which integrated population, economic and cultural values, policy and science/technology. Using the Southern Brigalow Belt biogeographic region of Queensland as a case study, the role of natural and human drivers in landscape change was investigated in four phases of settlement since 1840. The Brigalow Belt has experienced comparable rates of vegetation clearance over the past 50 years to areas of tropical deforestation. Economic factors were important during all phases of development, but the five regional drivers often acted in synergy. Environmental constraints played a significant role in slowing rates of change. Temporal trends of deforestation followed a sigmoidal curve, with initial slow change accelerating though the middle phases then slowing in recent times. Future landscape management needs to take account of the influence of all the components of the conceptual framework, at a range of organisational levels, if more ecologically sustainable outcomes are to be achieved.

While population growth is widely acknowledged as an important driver of land cover change, the role of unplanned human settlements is not adequately recognised. Many such settlements occur in the semi-arid lands of Kenya, which in the... more

While population growth is widely acknowledged as an important driver of land cover change, the role of unplanned human settlements is not adequately recognised. Many such settlements occur in the semi-arid lands of Kenya, which in the past had relatively lower human populations, but significant wildlife populations. Over the last four decades, the Chyulu Hills, adjacent to the Tsavo and Chyulu National Parks, have experienced rapid land cover changes associated with migrant squatter settlements. We used the Chyulu Hills to advance our understanding of the nature of land cover change under squatter settlements. We evaluated land cover change from aerial photographs and satellite images within a Geographic Information System (GIS) and combined it with landscape metrics and community surveys. Community perceptions of land cover change revealed comparable trajectories in major land cover types derived from the GIS analysis. Landscape metrics showed fragmentation of native vegetation followed by coalescence to contiguous patches of cultivation as settlements increased. Land cover trajectories under squatter settlements were influenced by historical land policies, protected area management as well as regional power structures. Our findings emphasize the importance of land use histories and community involvement in evaluating and understanding land cover change. Resolution of squatter conflicts should take cognisance of community perceptions, as well as the historical and political land use antecedents. We recommend human and social capacity building of squatters towards non-land-intensive micro-enterprises, and research and investment in ecotourism.▶ Rural landscapes under unplanned and/or squatter settlements may experience unprecedented rates and patterns of change in land cover. ▶ Combining empirical spatial analyses with community surveys can reveal important details in the process of land cover change, and can bridge an important knowledge gap in longitudinal studies where spatial and temporal gaps in remote sensing products are a constraint. ▶ Engaging squatters and illegal immigrants in land use planning may hold the potential for reduced conflicts in resource use where such settlements are in competition with conservation goals.

Lead arsenate (PbHAsO 4 ) was used as an insecticide in Washington fruit orchards from 1905 to 1947. We examined exposure potential for children living in an agricultural community with historic PbHAsO 4 use. Soil and housedust samples... more

Lead arsenate (PbHAsO 4 ) was used as an insecticide in Washington fruit orchards from 1905 to 1947. We examined exposure potential for children living in an agricultural community with historic PbHAsO 4 use. Soil and housedust samples were collected from 58 residences. Families were asked about land use history, age of home, and remodeling activities. Median concentrations of arsenic were higher in housedust than in soil (9.0 and 4.2 mg/g, respectively; P ¼ 0:05), as were lead concentrations (129 and 46 mg/g, respectively; P ¼ 0:0001). Significant associations were observed between indoor and outdoor levels of each metal, indicating trackin as an important exposure pathway. Homes on or near land use for pear or apple production between 1905 and 1947 had significantly higher soil (P ¼ 0:005) and housedust (P ¼ 0:004) lead, and soil arsenic (P ¼ 0:04) than did the other homes. Homes more than 30 years old had significantly higher soil and housedust lead than did newer homes (P ¼ 0:01). Homes remodeled within the past two years had significantly higher soil (P ¼ 0:01) and housedust (P ¼ 0:04) lead. Child doses extrapolated from these data indicate that 36% of homes had soil or dust arsenic levels above the minimum risk level estimated by the Agency for Toxic Substances and Disease Registry. None of the measured lead levels exceeded current US Environmental Protection Agency guidelines. Public health education programs focused on residential hygiene would be of value in areas of historic PbHAsO 4 use. r

Under the United Nations Framework Convention on Climate Change (UNFCCC), Non-Annex 1 countries such as Kenya are obliged to report green house gas (GHG) emissions from all sources where possible, including those from soils as a result of... more

Under the United Nations Framework Convention on Climate Change (UNFCCC), Non-Annex 1 countries such as Kenya are obliged to report green house gas (GHG) emissions from all sources where possible, including those from soils as a result of changes in land use or land management. At present, the convention encourages countries to estimate emissions using the most advanced methods possible, given the country circumstances and resources. Estimates of soil organic carbon (SOC) stocks and changes were made for Kenya using the Global Environment Facility Soil Organic Carbon (GEFSOC) Modelling System. The tool conducts analysis using three methods: (1) the Century general ecosystem model; (2) the RothC soil C decomposition model; and (3) the Intergovernmental Panel on Climate Change (IPCC) method for assessing soil C at regional scales. The required datasets included: land use history, monthly mean precipitation, monthly mean minimum and maximum temperatures for all the agro-climatic zones of Kenya and historical vegetation cover. Soil C stocks of 1.4-2.0 Pg (0-20 cm), compared well with a Soil and Terrain (SOTER) based approach that estimated $1.8-2.0 Pg (0-30 cm). In 1990 48% of the country had SOC stocks of <18 t C ha À1 and 20% of the country had SOC stocks of 18-30 t C ha À1 , whereas in 2000 56% of the country had SOC stocks of <18 t C ha À1 and 31% of the country had SOC stocks of 18-30 t C ha À1 . Conversion of natural vegetation to annual crops led to the greatest soil C losses. Simulations suggest that soil C losses remain substantial throughout the modelling period of 1990-2030. All three methods involved in the GEFSOC System estimated that there would be a net loss of soil C between 2000 and 2030 in Kenya. The decline was more marked with RothC than with Century or the IPCC method. In non-hydric soils the SOC change rates were more pronounced in high sandy soils compared to high clay soils in most land use systems. #

Aim of this thesis is the qualitative and quantitative investigation of land use and climatic impact on Holocene ecosystem development in northern Bavaria. Holocene relief and soil formation processes were analysed in six small catchments... more

Aim of this thesis is the qualitative and quantitative investigation of land use and climatic impact on Holocene ecosystem development in northern Bavaria. Holocene relief and soil formation processes were analysed in six small catchments (less than 45 hectares).The investigation areas are situated in Franconia, northern Bavaria. The region is delimited in the south by the undulating Steigerwald region and the flood plain of the river Regnitz and in the north by the hilly Obermainische Bruchschollenlandschaft. The geology of the region consists of sand and clay stones that are partly topped by a loamy solifluction layer. The chosen investigation areas of several hectares in size are characterised by well-preserved geoarchives: deposition areas on concave hill slopes, in gullies and small valleys. To investigate the Holocene ecosystem development stratigraphic, sedimentologic and pedologic parameters were determined from large pits dug in the geoarchives. The sediments and soil formations were dated by physical and archaeological methods. The analysis of contemporary written documents gave information about the regional land use, settlement and climate history to complete the reconstruction of the ecosystem development. Archaeological investigations were carried out in two catchments by the Bavarian State Office for Heritage Protection. From the beginning of the Neolithic Revolution until the Early Medieval Times the ecosystem development was determined by several phases of shifting/altering/changing and use intensity and duration. Woodland clearings for agriculture included only small plots over a limited time span. For large areas soil formation under wood was the dominant process still. During the Roman Times (30 BC until 450 AD) more land was used agriculturally. Extreme rainfall events caused soil loss of more than one meter. Until the end of the High Medieval Times all investigated catchments were almost completely deforested and used for agriculture or as settlement places. Sheet erosion was low during this time. Gullying took place in two of the catchments caused by concentrated flow along pathways. During the Late Medieval Times, a period of extreme rainfall events, the extended land use led to high soil erosion intensities. Gullies, up to 100 meter in length and six meter deep developed. Single erosion events led to sheet erosion that lowered the slopes up to 12 centimetres. The fertile soil was eroded, the underlying stones exposed. Land use was abandoned and the investigation areas reforested. Only plots for wine or hop growing were still in use. From the 16th until the 18th centuries land use increased again. The gullies that developed during the late medieval soil erosion period lengthened. The lower parts of the gullies filled with sediments. From the 19th century until today the land use intensity and subsequently the soil erosion intensity decreased continuously. Gully erosion occurred only along pathways. Since the middle of the 20th century almost all investigation areas were reforested or used as pasture. Comparing medieval and modern soil erosion rates for various catchments in Germanythe soil erosion rates in Franconia are similar to the young moranic areas of Northern Germany, but up to 10 times lower than in the loess areas.

Oak woodlands in the Mediterranean basin have been traditionally converted into agro-silvo-pastoral systems and exemplified sustainable land use in Europe. In Portugal, in line with the trend of other European countries, profound changes... more

Oak woodlands in the Mediterranean basin have been traditionally converted into agro-silvo-pastoral systems and exemplified sustainable land use in Europe. In Portugal, in line with the trend of other European countries, profound changes in management options during the twentieth century have led to landscape simplification. Landscapes are dynamic and the knowledge of future management planning combining biological conservation and soil productivity is needed, especially under the actual scenarios of drought and increasing evidence of heavy oak mortality. We examined the ectomycorrhizal (ECM) fungal community associated with cork oak in managed oak woodlands (called montado) under different land use practices, during summer. ECM fungal richness and abundance were assessed in 15 stands established in nine montados located in the Alentejo region (southern Portugal), using morphotyping and ITS rDNA analysis. Parameters related to the montados landscape characteristics, land use history over the last 25 years, climatic and edaphic conditions were taken into account. Fifty-five ECM fungal taxa corresponding to the most abundant fungal symbionts were distinguished on cork oak roots. Cenococcum geophilum and the families Russulaceae and Thelephoraceae explained 56% of the whole ECM fungal community; other groups were represented among the community: Cortinariaceae, Boletaceae, Amanita, Genea, Pisolithus, Scleroderma, and Tuber. There were pronounced differences in ECM fungal community structure among the 15 montados stands: C. geophilum was the only species common to all stands, tomentelloid and russuloid species were detected in 87–93% of the stands, Cortinariaceae was detected in 60% of the stands, and the other groups were more unequally distributed. Ordination analysis revealed that ECM fungal richness was positively correlated with the silvo-pastoral exploitation regime and low mortality of cork oak, while ECM fungal abundance was positively correlated with extensive agro-silvo-pastoral exploitation under a traditional 9-year rotation cultivation system and recent soil tillage. The effects of land use on the ECM fungal community and its implications in different scenarios of landscape management options, oak mortality, and global warming are discussed.

In der obermainischen Bruchschollenlandschaft konnten wenige Kilometer nördlich von Kronach in Oberfranken, die holozäne bzw. prähistorische und historische Siedlungsentwicklung, Landnutzungsgeschichte, Bodenbildung und Bodenerosion... more

In der obermainischen Bruchschollenlandschaft konnten wenige Kilometer nördlich von Kronach in Oberfranken, die holozäne bzw. prähistorische und historische Siedlungsentwicklung, Landnutzungsgeschichte, Bodenbildung und Bodenerosion umfassend rekonstruiert und erstmals für einen süddeutschen Standort die Dynamik der Boden- und Reliefentwicklung bis hin zu einzelnen Bodenerosionsereignissen quantifiziert werden. Hierfür wurden an einem etwa 80 m langen Hang unterhalb einer mittelalterlichen Ortswüstung mehrere bis zu 25 m lange Aufschlüsse angelegt und bodenkundlichstratigraphisch untersucht. Eine zeitliche Einordnung der einzelnen Böden und Sedimente erfolgte anhand archäologischer und physikalischer Datierungsverfahren. Anschließend konnte unter Einbeziehung archäologischer Grabungsergebnisse sowie der Auswertung zeitgenössischer Schriftquellen zur Landnutzungs-, Siedlungs- und Witterungsgeschichte die holozäne Landschaftsentwicklung rekonstruiert werden. Die im Untersuchungsgebiet Friesen bis zur Völkerwanderungszeit nachweisliche Bildung einer Braun- bzw. Parabraunerde erfolgte nicht kontinuierlich. So führten in den letzten 4000 Jahren neun Bodenerosionsphasen am Ober- und Mittelhang zu einer teilweisen Zerstörung des Bodens, der heute nur noch am Unterhang unter Kolluvien erhalten ist oder unter Kulturschichten konserviert wurde. Dementsprechend fanden im Endneolithikum/Frühbronzezeit, der Spätbronzezeit, der Hallstattzeit und der Römischen Kaiserzeit auf kurzlebigen Rodungsinseln Unterbrechungen der Bodenbildung statt, und Starkniederschläge führten zum Abtrag von Boden am Hang sowie zu Einschneidungen und Wiederverfüllungen einer Rinne quer zum Hangfuß. Für das Mittelalter lassen sich einzelne Phasen intensiver Bodenerosion mit den drei archäologisch ermittelten Siedlungsphasen korrelieren. Insbesondere im Hochmittelalter und Spätmittelalter wurde während Starkregenereignissen der überwiegende Teil der Braunerde bzw. der Parabraunerde hangabwärts transportiert und am Unterhang sowie im Tal abgelagert. Für die erste Hälfte des 14. Jahrhunderts konnten zwei extreme Bodenerosionsereignisse identifiziert werden, bei denen etwa 29 % der gesamten Kolluvien abgelagert wurden. In der Mitte des 14. Jahrhunderts lagen im Bereich des Oberhangs nur noch die nährstoffarme jungpleistozäne Solifluktionsdecke bzw. die anstehenden Gesteine des Buntsandsteins an der Oberfläche. In der Neuzeit fanden die höchsten Bodenabträge statt, jedoch lassen sich keine eindeutigen Aussagen über ein phasenhaftes Auftreten von Bodenerosionsereignissen machen, da die Kolluvien durch Pflugtätigkeit zusätzlich verlagert und ho-mogenisiert wurden. Für sieben geomorphodynamisch aktive Phasen in den letzten 2800 Jahren konnten die Abtragsraten bilanziert werden. Die Werte variieren von 0,5 t • ha-1 • a-1 in der Hallstatt-Zeit bis 1925 t • ha-1 • a-1 im Spätmittelalter. Durch die Bodenerosion wurde die Form des untersuchten Hanges stark verändert. Das Gefälle des konvexen Oberhangs verflachte sich von der Völkerwanderungszeit bis heute von über 30 % auf nunmehr ca. 16 %. Die Ergebnisse deuten darauf hin, dass die starken Bodenerosionsereignisse in der ersten Hälfte des 14. Jahrhunderts in einem kausalen Zusammenhang mit dem Auftreten der spätmittelalterlichen Wüstungsperiode in der Kronacher Region stehen.

Soil properties were compared in adjacent 50-year-old Norway spruce, Scots pine and silver birch stands growing on similar soils in south-west Sweden. The effects of tree species were most apparent in the humus layer and decreased with... more

Soil properties were compared in adjacent 50-year-old Norway spruce, Scots pine and silver birch stands growing on similar soils in south-west Sweden. The effects of tree species were most apparent in the humus layer and decreased with soil depth. At 20–30cm depth in the mineral soil, species differences in soil properties were small and mostly not significant. Soil C, N,

e siècle et finissant au XIV e siècle, surmonté de deux mètres de tourbe organique. L'analyse palynologique révèle 4 zones succes- sives. La base du diagramme est caractérisée par un couvert de chênaie-charmaie dense avec des taux de... more

e siècle et finissant au XIV e siècle, surmonté de deux mètres de tourbe organique. L'analyse palynologique révèle 4 zones succes- sives. La base du diagramme est caractérisée par un couvert de chênaie-charmaie dense avec des taux de pollen arbo- réens avoisinant les 85 %. Très rapidement, on note une augmentation des indices polliniques d'anthropisation (Plantago lanceolata, Rumex, Artemisia, Urticacées).

Agricultural dynamics and associated changes in the structure of habitat patches affect species composition and distribution in the landscape. Land-use, landscape changes and vegetation changes of weeds were analysed in a 4 km 2 area in... more

Agricultural dynamics and associated changes in the structure of habitat patches affect species composition and distribution in the landscape. Land-use, landscape changes and vegetation changes of weeds were analysed in a 4 km 2 area in Central Germany (Saxony-Anhalt) from 1953 to 2000. This period includes the collectivisation (1952)(1953)(1954)(1955)(1956)(1957)(1958)(1959)(1960)(1961)(1962)(1963)(1964)(1965)(1966)(1967)(1968), the agricultural industrialisation and the privatisation of agricultural land following the political changes in East Germany in 1990. For the analyses, historic and current aerial photographs and vegetation data were used. Landscape indices and the average amount of mineral fertilizers were used as indicators for landscape structure and land-use intensity. Intensification of agriculture and the collectivisation in East Germany in the fifties and sixties led to a decline of the spatial heterogeneity of the landscape matrix (arable fields). The average number and cover of weed species, especially archaeophytes, decreased significantly since 1957. However, the total number of weed species increased. There was a remarkably high number of species with an average cover below 0.05%, called ''chance'' species in 2000. Out of 17 tested landscape indices only mean patch size and mean patch fractal dimension were significantly correlated with the average number of weed species. The average amount of the mineral fertilizer potash used as land-use intensity indicator was significantly negatively correlated with the total number of weed species. However, there was an increase in the number of farms after 1990 without changes in landscape structure and arable weed vegetation. The results suggest that structural variability of the landscape and habitat quality are the principal correlates of plant species diversity. # 2005 Published by Elsevier B.V.

In order to study landscape changes, an interdisciplinary approach that integrates landscape ecology and history is vital. This paper presents two methods to facilitate this integration. The "rst method aims at improving communication... more

In order to study landscape changes, an interdisciplinary approach that integrates landscape ecology and history is vital. This paper presents two methods to facilitate this integration. The "rst method aims at improving communication between the two disciplines by de"ning`interface categoriesa to talk more speci"cally about human impact on ecosystems. This procedure is illustrated with an example of forest changes in the Swiss lowlands. In the second method patterns of change in environmental features across regions are compared with regional di!erences in the importance of human activities with potential impact on the environmental feature under study. This method, referred to as double comparative study, is illustrated with an example of changes in forest composition in the northeastern United States.

Dendroecology and land-use history were used to investigate the ecological history of a 326-year-old Quercus prinus L. forest. Quercus prinus, Castanea dentata (Marsh.) Borkh., and Pinus rigida Mill. dominated this talus slope prior to... more

Dendroecology and land-use history were used to investigate the ecological history of a 326-year-old Quercus prinus L. forest. Quercus prinus, Castanea dentata (Marsh.) Borkh., and Pinus rigida Mill. dominated this talus slope prior to European settlement based on witness tree records. Oak species have exhibited continuous recruitment over three centuries probably in response to periodic fire and wind disturbances. While the stand escaped the direct impacts of timber cutting and the charcoal iron industry, the indirect effects of these land-use practices increased growth and recruitment. Different criteria were used for understory versus overstory trees to improve our detection of growth releases. Overall, major disturbances occurred approximately every 40 and 31 years before and after European settlement, respectively. This century, old-growth Q. prinus experienced marked growth increases coupled with high recruitment following the introduction of the chestnut blight (Cryphonectria parasitica (Murr.) Barr.) to the stand in 1909. Tree growth was also highly correlated with temperature and Palmer drought severity indices between 1895 and 1995. Climatic fluctuations in the 1820s-1830s and 1920s reduced radial growth and recruitment resulting in stem exclusion stages following regeneration pulses. Relating land-use history and climatic data to the dendroecology of this forest improved our understanding of its historical development.

Acari Agroecosystems Disturbances Land management Argentina a b s t r a c t

The study of charcoal produced by five burning episodes that occurred in a rapid succession within a ritual pit dating to the late Iron Age at Raffin Fort, Co. Meath, Ireland, reveals considerable variation in the charcoal assemblages... more

The study of charcoal produced by five burning episodes that occurred in a rapid succession within a ritual pit dating to the late Iron Age at Raffin Fort, Co. Meath, Ireland, reveals considerable variation in the charcoal assemblages resulting from each burning episode. Wood selection processes are considered against the background of information on woodland composition and land-use history provided by a detailed pollen diagram from nearby Emlagh Bog, the chronology of which is based on both AMS 14 C dates and tephra analysis. A human skull fragment lay on top of the charcoal layers but the radiocarbon evidence indicates that the skull predated the burnings by at least a century. This and other evidence indicate a ritual pit with the skull as a human relic. It is suggested that, in this instance, wood selection was neither random nor determined solely by availability or combustibility, but instead may have been informed by socio-religious belief systems pertaining to trees and wood. Early Irish documentary sources, which reveal a complex ethnography of wood and trees in later prehistoric and early historic Ireland, are reviewed. The results shed fresh light on aspects of late Iron Age archaeology in a part of Europe that was outside the direct influence of the Roman world. New information is provided on a distinctive feature in late Holocene Irish pollen records namely the Late Iron Age Lull (ca. a.d. 1-500). During this time, widespread regeneration of woody vegetation took place. In the subsequent early Medieval period renewed farming activity resulted in substantial decline in woodland, a pattern also seen at many other locations in Ireland.

Information from horizontal quantum sensor arrays and data on forest structure was used to measure photosynthetically active radiation (PAR). Forest sites with stands of similar age and land-use history were blocked into three valley,... more

Information from horizontal quantum sensor arrays and data on forest structure was used to measure photosynthetically active radiation (PAR). Forest sites with stands of similar age and land-use history were blocked into three valley, three mid-slope, and three ridge topographic positions. Analysis of forest structure and light measurements demonstrate: (1) canopy height and leaf area index decreased on progressing from valley to ridge; (2) total understory radiation increases on progressing from the valley to ridge; (3) sunflecks contribute a disproportionate amount of photosynthetic photon flux (PPF) on sunny days (40-80%) with number and duration of sunfleck periods increasing from valley to ridge.

Secondary successional vegetation represents one-third of the 7% of the original area covered with tropical dry forest that remains in central Veracruz, Mexico. In this region, fallow periods are short, in general, no longer than... more

Secondary successional vegetation represents one-third of the 7% of the original area covered with tropical dry forest that remains in central Veracruz, Mexico. In this region, fallow periods are short, in general, no longer than 7–10 years, and old secondary successional sites are not available. Therefore we evaluated the potential of very early successional stages of tropical dry forest with different land use histories for recovering the structure and composition of regional forest. We compared five early successional sites (7–72 months) with five nearby forest remnants. Successional sites had reached 38 and 30%, respectively, of the average basal area and density recorded for the forest understories, but only 5 and 10%, respectively, of the basal area and density of forest overstories. A total of 132 tree species were recorded, 45 at successional and 107 at forest sites. Individuals of tree species with animal-dispersed seeds (57%) were significantly better represented than wind-dispersed (22%) and self-dispersing (21%) species in both successional and forest sites. Successional sites had already recruited 10% of the intermediate and shade-tolerant species that grow in forest remnants. However, only 20 species occurred in both early successional and forest sites, several showing resprouting ability. We conclude that the entry of forest species to the successional process at very early stages and the recruitment of individuals from resprouting may facilitate the recovery of the dry forest in Veracruz.

The complex interactions between human activity and natural processes determine non-linear dynamics in ecosystems that can difficult their management. Human settlements in arid lands contribute to the modification of disturbance regimes,... more

The complex interactions between human activity and natural processes determine non-linear dynamics in ecosystems that can difficult their management. Human settlements in arid lands contribute to the modification of disturbance regimes, including the introduction of new disturbances and the elimination of others. In consequence, they can alter the functional mechanisms that allow systems to overcome limiting factors, leading to desertification. In this revision, we evaluated the effects of the changes on disturbance regimes produced by the different forms of land transformation on the structure and function of ecosystems of the Monte Biogeographical Province, in Argentinean arid west. Two approaches were used: the analysis of land use history and the analysis of the effects of the main disturbances on the dynamics of different communities. We concluded that throughout the history of the Monte Desert, the joint action of natural and anthropic agents has resulted in complex dynamics that lead most area of the Monte to a moderate to severe status of desertification. The modification of the disturbance regime had strong consequences for several aspects of the dynamics of communities, such as species composition and diversity, water dynamics, soil conditions, trophic structure and productivity of Monte Desert ecosystems. However, disturbance regimes could be managed to promote favorable transitions in ecosystems and, therefore, could be a tool for optimizing productivity of agro-ecosystems, and recovering and conserving natural ecosystems.

Research on tropical forest cover change processes identifies myriad driving forces and demonstrates how change dynamics are non-linear and complex. Despite appreciation in the academic literature for the historical patterns and processes... more

Research on tropical forest cover change processes identifies myriad driving forces and demonstrates how change dynamics are non-linear and complex. Despite appreciation in the academic literature for the historical patterns and processes of deforestation, however, a simplistic, linear ʻdeforestation narra-tiveʼ persists in the popular imagination. Concern arises when this narrative influences environmental policy and effective response to the tropical deforestation problem. Our main goals here are twofold: (1) to contribute to a nuanced history of forest change in southeastern Mexico; and (2) to explore the role of institutional development in reducing deforestation rates. Drawing on forest transition theory, we analyse the twentieth century forest histories of the eastern Yucatán Peninsula, the southern Yucatán Peninsula, and the Lacandón Rainforest. A deforestation narrative rightly dominates characterisations of the 1960-85 period in southeastern Mexico, but it falls short of accurately representing the complex processes of deforestation, forest recovery, and the development of sustainability-oriented grassroots institutions in the 1985-2003 period.

We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire... more

We explored variations in inorganic soil nitrogen (N) concentrations across metropolitan Phoenix, Arizona, and the surrounding desert using a probability-based synoptic survey. Data were examined using spatial statistics on the entire region, as well as for the desert and urban sites separately. Concentrations of both NO 3-N and NH 4-N were markedly higher and more heterogeneous amongst urban compared to desert soils. Regional variation in soil NO 3-N concentration was best explained by latitude, land use history, population density, along with percent cover of impervious surfaces and lawn, whereas soil NH 4-N concentrations were related to only latitude and population density. Within the urban area, patterns in both soil NO 3-N and NH 4-N were best predicted by elevation, population density and type of irrigation in the surrounding neighborhood. Spatial autocorrelation of soil NO 3-N concentrations explained 49% of variation among desert sites but was absent between urban sites. We suggest that inorganic soil N concentrations are controlled by a number of 'local' or 'neighborhood' human-related drivers in the city, rather than factors related to an urban-rural gradient.

Land-use history interacts with natural forces to influence the severity of disturbance events and the rate and nature of recovery processes in tropical forests. Although we are far from an integrated view of forest recovery processes,... more

Land-use history interacts with natural forces to influence the severity of disturbance events and the rate and nature of recovery processes in tropical forests. Although we are far from an integrated view of forest recovery processes, some generalizations can be made. Recovery of forest structure and composition is relatively rapid following disturbances that primarily impact forest canopies, such as hurricanes. Recovery is considerably slower following disturbances that heavily impact soils as well as aboveground vegetation, such as bulldozing, heavy or long-term grazing, and severe fires, often with long-lasting effects on species composition. The landscape matrix plays a critical role in local recovery processes. Proximity of disturbed areas to remnant forest patches promotes more rapid recovery, which depends heavily on seed dispersal. Recovery of aboveground biomass is constrained by soil fertility and texture across regions as well as across soil types within a region. Restoration of soil fertility may be a prerequisite for forest recovery on sites with severely degraded soils. Despite evidence of rapid forest recovery following large-scale deforestation, many degraded areas of today's tropics will require human assistance to recover forest structure, species composition, and species interactions typical of mature tropical forests.

Zusammenfassung: Die vorliegende Studie beschreibt die flussbegleitende Vegetetation der Salza (Steiermark) zwischen Gusswerk und der Mündung in die Enns. Sie liefert einerseists eine syntaxonomische Gliederung samt standörtlicher und... more

Zusammenfassung: Die vorliegende Studie beschreibt die flussbegleitende Vegetetation der Salza (Steiermark) zwischen Gusswerk und der Mündung in die Enns. Sie liefert einerseists eine syntaxonomische Gliederung samt standörtlicher und floristischer Charakterisierung der gesamten flussnahen Vegetation und andererseits eine Beschreibung der räumlichen Anordnung der einzelnen Gesellschaften in Abhängigkeit von Mittelwasserlinie und Überflutungsregime des Flusses. Die Abhängigkeit dieser Zonation von den geomorphologischen Bedingungen und der menschlichen Nutzungsgeschichte wird anhand von sieben repräsentativen Querschnittprofilen demonstriert. Eine abschließende Diskussion stellt die Auenvegetation der Salza in einen überregionalen Kontext und weist auf ihre naturschutzfachliche Bedeutung im nationalen und EUweiten Rahmen hin.

Unusually high SOC levels have been reported for sandy cropland soils in North-Western Europe. A potential link with their general heathland land-use history was investigated by comparing two soil pairs of relict heathland and cultivated... more

Unusually high SOC levels have been reported for sandy cropland soils in North-Western Europe. A potential link with their general heathland land-use history was investigated by comparing two soil pairs of relict heathland and cultivated former heathland in the Belgian sandy region. A sequential chemical fractionation yielded similar sizes in corresponding SOM fractions between the heathland and cropland soils (i.e. NaOCl resistant: 12.3-15.0 g C kg -1 and NaO-Cl + HF resistant: 2.6-5.3 g C kg -1 ). Higher amounts of clay sized N in the cropland plots can be attributed to N additions from mineral fertilizers and animal manure. Temperature resolved Pyrolysis Field Ionization Mass Spectroscopy analysis showed that the composition of both relict heathland and cultivated soils was surprisingly similar, in spite of over 60 years of intense cropland management. The mass spectra of SOM in both heathland-cropland soil pairs investigated was dominated by signals from lipids, alkylaromatics and sterols. The accumulation of this SOM rich in aliphatics was logically linked to the high input of lipids, longchain aliphatics and sterols from heathland vegetation and the low soil pH and microbial activity. Based on the relatively high OC surface loadings of HF-extractable OM (13-44 mg C m -2 Fe and 1.2-2.3 mg C m -2 clay), direct organo-mineral bonds between OM and Feoxides or clay minerals seem to be only partly involved as a stabilization mechanism in these soils. The distinct bimodal shape of the thermograms indicates that OMcrosslinking could furthermore contribute substantially to SOM stabilization in these soils. This study therefore corroborates the previously proposed view that lipids may be bound in networks of alkylaromatics, the structural building blocks of OM macromolecules. We hypothesize that such binding is able to explain the measured retention of these OM components, even under several decades of cropland management.

As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring... more

As regional and continental carbon balances of terrestrial ecosystems become available, it becomes clear that the soils are the largest source of uncertainty. Repeated inventories of soil organic carbon (SOC) organized in soil monitoring networks (SMN) are being implemented in a number of countries. This paper reviews the concepts and design of SMNs in ten countries, and discusses the contri-Plant Soil (2011) 338:247-259 from the USA and Belgium show that uncertainties in SOC change range from 1.6-6.5 Mg C ha −1 for the prediction of SOC stock changes on individual sites to 11.72 Mg C ha −1 or 34% of the median SOC change for soil/land use/climate units. For national SOC monitoring, stratified sampling sites appears to be the most straightforward attribution of SOC values to units with similar soil/land use/climate conditions (i.e. a spatially implicit upscaling approach).

Landschaftsentwicklung seit der Römerzeit im westlichen Segbachtal bei Mayen (Lkr. Mayen-Koblenz) in der Osteifel. Erste Teilprojektergebnisse des DFG-Projekts »Zur Landnutzung im Umfeld eines römischen Industriereviers« ***... more

Landschaftsentwicklung seit der Römerzeit im westlichen Segbachtal bei Mayen (Lkr. Mayen-Koblenz) in der Osteifel. Erste Teilprojektergebnisse des DFG-Projekts »Zur Landnutzung im Umfeld eines römischen Industriereviers« *** Bodenkundlich-sedimentologische Untersuchungen an Hangkolluvien, Auensedimenten und Altflurrelikten im westlichen Segbachtal (Osteifel) zeigen, dass in den letzten 2500 jahren deutliche Eingriffe in den Wasser- und Stoffhaushalt vorgenommen wurden. Die bildung von auensedimenten lässt sich ab der Frühlatènezeit belegen. Besonders mächtige Schichten stammen aus der Spätlatènezeit bis frühen Römischen Kaiserzeit (feiner Auenlehm) und aus dem Mittelalter (von den Hängen herabgespültes kieshaltiges Sediment). Für die Römische Kaiserzeit konnte die Anlage eines quer zum Tal liegenden Mauersystems nachgewiesen werden, das in Verbindung mit einem vermuteten Wasserbecken steht. ungewöhnlich sind ein spätantikes Drainagesystem sowie eine möglicherweise römerzeitliche Rek...

Species composition in successional dry forests in the tropics varies widely, but the effect of this variation on biogeochemical processes is not well known. We examined fluxes of N oxides (nitrous and nitric oxide), soil N cycling, and... more

Species composition in successional dry forests in the tropics varies widely, but the effect of this variation on biogeochemical processes is not well known. We examined fluxes of N oxides (nitrous and nitric oxide), soil N cycling, and litter chemistry (C/N ratio) in four successional dry forests on similar soils in western Puerto Rico with differing species compositions and land-use histories. Forests patch-cut for charcoal 60 years ago had few legumes, high litter C/N ratios, low soil nitrate and low N oxide fluxes. In contrast, successional forests from pastures abandoned several decades ago had high legume densities, low litter C/N ratios, high mean soil nitrate concentrations and high N oxide fluxes. These post-pasture forests were dominated by the naturalized legume Leuceana leucocephala, which was likely responsible for the rapid N cycling in those forests. We conclude that agriculturally induced successional pathways leading to dominance by a legume serve as a mechanism for increasing N oxide emissions from tropical regions. As expected for dry regions, nitric oxide dominated total N oxide emissions. Nitric oxide emissions increased with increasing soil moisture up to about 30% water-filled pore space then stabilized, while nitrous oxide emissions, albeit low, continued to increase with increasing soil wetness. Inorganic N pools and net N mineralization were greatest during peak rainfalls and at the post-agricultural site with the highest fluxes. Soil nitrate and the nitrate/ammonium ratio correlated positively with average N oxide fluxes. N oxide fluxes were nega-tively and exponentially related to litter C/N ratio for these dry forests and the relationship was upheld with the addition of data from seven wet forests in northeastern Puerto Rico. This finding suggests that species determination of litter C/N ratio may partly determine N oxide fluxes across widely differing tropical environments.

Land-use history – the number, type, and duration of previous land uses – is relevant to many questions regarding land-use effects on soil carbon, but is infrequently reported. We examine the importance of land-use history variables, as... more

Land-use history – the number, type, and duration of previous land uses – is relevant to many questions regarding land-use effects on soil carbon, but is infrequently reported. We examine the importance of land-use history variables, as well as topographic and edaphic variables, on soil C in a range of forest types – native forest, pine plantations, secondary forest and