Biased-corrected richness estimates for the Amazonian tree flora (original) (raw)
Related papers
Rarity of monodominance in hyperdiverse Amazonian forests
Scientific Reports, 2019
Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors.
towards a dynamic list of Amazonian tree species
Scientific Reports, 2019
To provide an empirical foundation for estimates of the Amazonian tree diversity, we recently published a checklist of 11,675 tree species recorded to date in the region (ter Steege H, et al. (2016) The discovery of the Amazonian tree flora with an updated checklist of all known tree taxa. Scientific Reports 6:29549). From this total of plant records compiled from public databases and literature, widely used in studies on the Amazonian plant diversity, only 6,727 tree species belong to the first taxonomicallyvetted checklist published for the region (Cardoso D, et al. (2017) Amazon plant diversity revealed by a taxonomically verified species list. PNAS 114:10695-10700). The striking difference in these two numbers spurred us to evaluate both lists, in order to release an improved Amazonian tree list; to discuss species inclusion criteria; and to highlight the ecological importance of verifying the occurrence of “non-Amazonian” trees in the region through the localization and identification of specimens. A number of species in the 2016 checklist that are not trees, non-native, synonyms, or misspellings were removed and corresponded to about 23% of the names. Species not included in the taxonomicallyvetted checklist but verified by taxonomists to occur in Amazonia as trees were retained. Further, the inclusion of recently recorded/new species (after 2016), and recent taxonomic changes added up to an updated checklist including 10,071 species recorded for the Amazon region and shows the dynamic nature of establishing an authoritative checklist of Amazonian tree species. Completing and improving this list is a long-term, high-value commitment that will require a collaborative approach involving ecologists, taxonomists, and practitioners.
Tropical forest loss and fragmentation are due to increase in coming decades. Understanding how matrix dynamics, especially secondary forest regrowth, can lessen fragmentation impacts is key to understanding species persistence in modified landscapes. Here, we use a whole-ecosystem fragmentation experiment to investigate how bat assemblages are influenced by the regeneration of the secondary forest matrix. We surveyed bats in continuous forest, forest fragments and secondary forest matrix habitats, ~15 and ~30 years after forest clearance, to investigate temporal changes in the occupancy and abundance of old-growth specialist and habitat generalist species. The regeneration of the second growth matrix had overall positive effects on the occupancy and abundance of specialists across all sampled habitats. Conversely, effects on generalist species were negligible for forest fragments and negative for secondary forest. Our results show that the conservation potential of secondary forests for reverting faunal declines in fragmented tropical landscapes increases with secondary forest age and that old-growth specialists, which are often of most conservation concern, are the greatest beneficiaries of secondary forest maturation. Our findings emphasize that the transposition of patterns of biodiversity persistence in island ecosystems to fragmented terrestrial settings can be hampered by the dynamic nature of human-dominated landscapes. Humanity's global footprint is so ubiquitous and far-reaching that many argue that we now live in a new geological epoch, the Anthropocene 1. Habitat loss and fragmentation are pervasive and conspicuous features of this new historical context, which, in combination with other human-related threats, are compelling the planet into a " sixth wave of extinction " 2,3. The scars of the Anthropocene defaunation are being carved deep into the planet's biodiversity strongholds, the tropical forests 4. As large swaths of old-growth forest give way to expanding humanized landscapes, species persisting in forest remnants are left to endure the pervasive consequences of increased isolation and decreased area 5. Landscape-wide assemblage dynamics in fragments created in the aftermath of deforestation are dependent , to a large extent, on the nature of the matrix within which forest patches are embedded 6. Conservation science has traditionally conceived the modified matrix as a " sea " of hostile habitat, in which fragments act as " islands " and this analogy has guided much of the theory and practice of the field 6,7. However, equating forest fragments with island ecosystems, while appropriate in some situations, fails to accommodate the heterogeneous and dynamic nature of most present-day modified landscapes 8,9. Vertebrate assemblage dynamics in tropical land-bridge islands have painted a dire portrait of the consequences of forest fragmentation in true island systems 10–12. Mainland studies that also construed fragments as
Evolution of nitrogen cycling in regrowing Amazonian rainforest
2019
Extensive regions of tropical forests are subjected to high rates of deforestation and forest regrowth and both are strongly affect soil nutrient cycling. Nitrogen (N) dynamics changes during forest regrowth and the recovery of forests and functioning similar to pristine conditions depends on sufficient N availability. We show that, in a chronosequence of Amazonian forests, gross nitrification and, as a result, nitrate-to-ammonium (NO 3 − : NH 4 +) ratio were lower in all stages of regrowing forests (10 to 40 years) compared to pristine forest. This indicates the evolution of a more conservative and closed N cycle with reduced risk for N leaking out of the ecosystem in regrowing forests. Furthermore, our results indicate that mineralization and nitrification are decoupled in young regrowing forests (10 years), such as that high gross mineralization is accompanied by low gross nitrification, demonstrating a closed N cycle that at the same time maintains N supply for forest regrowth. We conclude that the status of gross nitrification in disturbed soil is a key process to understand the mechanisms of and time needed for tropical forest recovery. In the Brazilian Amazon region, almost 800 000 km 2 of land has been deforested, mainly for soya bean cultivation , logging and cattle ranching 1. The high rate of tropical deforestation led to global concern since these areas are a hot spot of biodiversity and have direct influence on the global climate through hydrology and exchange of greenhouse gases 2-5. However, a large area of approximately 167 000 km 2 previously deforested land has been abandoned after exploitation 6 and secondary forests have established on that land 7. The regrowth area in the Amazon is increasing 6 , but our current knowledge about nutrient availability, biogeochemical processes, and how the post-disturbance regeneration influences these processes is poorly understood 8. Likewise, nutrient shortage in deforested areas is expected 9 , but the influence and magnitude of limitation, which can drive the recovery tra-jectory, on regrowth forest are still uncertain 10. Early secondary forests have high growth rates with rapidly increasing forest biomass 11 , even when N is apparently limited 12. This indicates that feedback mechanisms on soil N availability exist, providing sufficient plant available N to maintain forest regrowth. Microbial processes, such as mineralization and nitrification, drive the soil N cycle and thereby control the amount of organic and inorganic N forms in soil 13,14. Mineralization of soil organic matter (SOM) is responsible for inorganic N production in terrestrial ecosystems, which is important for plant N uptake that occurs mainly in inorganic form. The NH 4 + released by mineralization also supports nitrification 15 , the oxidation of NH 4 + to NO 3 −. These two inorganic N forms may have different fates in soils, as immobilization in biomass, leaching and gas losses 16 , and the occurrence and magnitude of these pathways might influence the forest growth 17. Davidson et al. 8 investigated the N cycling recovery in secondary forest age chronosequences after agricultural abandonment in the Amazon region. These authors found indications for a conservative N cycling in soils of young successional tropical forests based on N and phosphorus (P) contents in leaves, litterfall and soils, low NO 3 − : NH 4 + ratios as well as low nitrous oxide (N 2 O) emissions. However, the mechanistic changes in the soil N cycle during forest regrowth have not been studied in the Amazon Region. The actual dynamic of labile N in soils is best represented by gross soil N cycle dynamics, such as gross N mineralization and nitrification, since the gross transformations directly control the inorganic N availability for plants growth. Therefore, quantifying the gross N transformations in tropical regrowth forest soils is an important step in managing and enhancing abandoned managed areas, which also provides valuable information for model implementation.
Scientific report, 2019
Soil C and N turnover rates and contents are strongly influenced by climates (e.g., mean annual temperature MAT, and mean annual precipitation MAP) as well as human activities. However, the effects of converting natural forests to intensively human-managed plantations on soil carbon (C), nitrogen (N) dynamics across various climatic zones are not well known. In this study, we evaluated C, N pool and natural abundances of δ 13 C and δ 15 N in forest floor layer and 1-meter depth mineral soils under natural forests (NF) and plantation forest (PF) at six sites in eastern China. Our results showed that forest floor had higher C contents and lower N contents in PF compared to NF, resulting in high forest floor C/N ratios and a decrease in the quality of organic materials in forest floor under plantations. In general, soil C, N contents and their isotope changed significantly in the forest floor and mineral soil after land use change (LUC). Soil δ 13 C was significantly enriched in forest floor after LUC while both δ 13 C and δ 15 N values were enriched in mineral soils. Linear and non-linear regressions were observed for MAP and MAT in soil C/N ratios and soil δ 13 C, in their changes with NF conversion to PF while soil δ 15 N values were positively correlated with MAT. Our findings implied that LUC alters soil C turnover and contents and MAP drive soil δ 13 C dynamic.
Scientific Reports, 2019
Species extinctions undermine ecosystem functioning, with the loss of a small subset of functionally important species having a disproportionate impact. However, little is known about the effects of species loss on plant-pollinator interactions. We addressed this issue in a field experiment by removing the plant species with the highest visitation frequency, then measuring the impact of plant removal on flower visitation, pollinator effectiveness and insect foraging in several sites. Our results show that total visitation decreased exponentially after removing 1-4 most visited plants, suggesting that these plants could benefit co-occurring ones by maintaining high flower visitor abundances. Although we found large variation among plant species, the redistribution of the pollinator guild affected mostly the other plants with high visitor richness. Also, the plant traits mediated the effect of removal on flower visitation; while visitation of plants which had smaller inflorescences and more sugar per flower increased after removal, flower visitors did not switch between flower shapes and visitation decreased mostly in plants visited by many morpho-species of flower visitors. Together, these results suggest that the potential adaptive foraging was constrained by flower traits. Moreover, pollinator effectiveness fluctuated but was not directly linked to changes of flower visitation. In conclusion, it seems that the loss of generalist plants alters plant-pollinator interactions by decreasing pollinator abundance with implications for pollination and insect foraging. Therefore, generalist plants have high conservation value because they sustain the complex pattern of plant-pollinator interactions. Overall community-level dynamics and ecosystem services are often disproportionately affected by a subset of the local species pool 1,2. This core of functionally important species contains, among others, generalists, which play a dominant ecological role within the community as they are often among the most abundant species 3,4 and interact with a majority of other species 5 , mostly by complex facilitation-competition interactions 6. Generalist plants offer floral resources, mostly sugars from nectar and proteins from pollens, to a wide spectrum of pollinators and thus help to sustain those pollinators' populations 7. A generalist plant is typically visited by both generalist pollinators and specialist ones, which provides multiple advantages. Indeed, visitation by a large number of different pollinators increases the chances of having the pollen dispersed 8. In turn, when gener-alist pollinators are foraging in a patch, they can collect resources from a wide range of plants. This strategy could provide nutritional benefits from multiple sources 9,10 , but may also lead to pollination of several plant species because it is believed that generalist pollinators are visiting only a few plant species during each foraging bout 8. Therefore, conservation of abundant generalists may be important, because their persistence can sustain most of the complexity of interactions taking place in a community 11 .
Forest edge disturbance increases rattan abundance in tropical rain forest fragments OPEN
Human-induced forest fragmentation poses one of the largest threats to global diversity yet its impact on rattans (climbing palms) has remained virtually unexplored. Rattan is arguably the world's most valuable non-timber forest product though current levels of harvesting and land-use change place wild populations at risk. To assess rattan response to fragmentation exclusive of harvesting impacts we examined rattan abundance, demography and ecology within the forests of northeastern, Australia. We assessed the community abundance of rattans, and component adult (>3 m) and juvenile (≤3 m) abundance in five intact forests and five fragments (23–58 ha) to determine their response to a range of environmental and ecological parameters. Fragmented forests supported higher abundances of rattans than intact forests. Fragment size and edge degradation significantly increased adult rattan abundance, with more in smaller fragments and near edges. Our findings suggest that rattan increase within fragments is due to canopy disturbance of forest edges resulting in preferential, highlight habitat. However, adult and juvenile rattans may respond inconsistently to fragmentation. In managed forest fragments, a rattan abundance increase may provide economic benefits through sustainable harvesting practices. However, rattan increases in protected area forest fragments could negatively impact conservation outcomes. Deforestation of tropical rainforests rarely removes all pre-existing vegetation in a given area 1 , but leaves isolated fragments of the original vegetation surrounded by new habitat types 2. Fragmentation of tropical forests is globally pervasive and increasing in extent 3–5 , with forest fragments now representing 46% of the remaining forested area 6. Forest fragments support less species than comparable intact forest 7, 8. The estimated 13–75% lost diversity 7 that occurs in fragments has been associated with habitat alteration due to the degradation of a variety of biological and physical processes e.g. see reviews by: refs 8–11. For instance, one by-product of forest fragmentation is that it greatly increases the area of forest edge habitat 12. In fact, current estimates suggest 70% of the world's remaining forest is within 1 km from a forest edge 7. Proximity to a newly-created forest edge exposes the surviving biota to numerous environmental changes associated with edges, such as: increased light levels, increased desiccation, and greater temperature variability 11, 13, 14. These environmental changes are a consequence of increased disturbance found on forest edges due to mechanisms such as an increase in the rate of large tree loss and tree-turnover 10, 15–17. In addition, forest fragmentation threatens species' long-term persistence through the degradation of beneficial ecological interactions such as pollination and seed dispersal, between the remnant biota 11, 18–21. Despite their degraded state, forest fragments are often the sole means of preservation for many rare and endangered species and threatened ecosystems within heavily deforested regions 22–24. Consequently, retention of forest fragments is of high importance for species and community conservation at regional spatial scales 22–24. If the conservation values of forest fragments are to be preserved, fragments must not only be retained but effectively managed. This necessitates an understanding of their internal biota and ecology. The majority of work on fragmentation has involved the study of trees. Indeed, the response of forest trees to fragmentation has received considerable focus e.g. refs 10, 11, 17, 25 and 26. However, despite the high diversity of non-tree life forms in tropical forests 27 the potential impact of forest fragmentation on this forest component is less well known. For instance, even though rattans are one of the World's most valuable non-timber forest
Evolutionary diversity is associated with wood productivity in Amazonian forests
Nature Ecology & Evolution, 2019
Higher levels of taxonomic and phylogenetic diversity play important and independent roles in determining ecosystem function 1-3. In experimental studies of temperate grasslands , higher levels of taxonomic and evolutionary diversity were associated with greater biomass and productivity and variability in the amount of evolutionary history shared within a group of species was often a better predictor of productivity than the number of species 2-4 , consistent with the hypothesis that evolutionary dissimi-larity is related to niche complementarity 1-5. However, although the results of a range of biodiversity experiments 2-7 suggest that communities with distantly related lineages have greater carbon stocks and productivity, the effect of phylogenetic diversity on measures of ecosystem function remains controversial. Positive relationships are common, but not a rule, and negligible effects of evolutionary diversity on productivity and biomass have been reported in some cases 8,9. Therefore, it is still unclear whether these relationships can be generalized, and the extent to which evolutionarily diverse communities maximize function is unknown, particularly at large scales relevant to conservation planning. The total amount of phylogenetic diversity represented by species within a community may be valuable for understanding how diversity affects ecosystem function, because these properties Higher levels of taxonomic and evolutionary diversity are expected to maximize ecosystem function, yet their relative impor tance in driving variation in ecosystem function at large scales in diverse forests is unknown. Using 90 inventory plots across intact, lowland, terra firme, Amazonian forests and a new phylogeny including 526 angiosperm genera, we investigated the association between taxonomic and evolutionary metrics of diversity and two key measures of ecosystem function: above ground wood productivity and biomass storage. While taxonomic and phylogenetic diversity were not important predictors of variation in biomass, both emerged as independent predictors of wood productivity. Amazon forests that contain greater evolutionary diversity and a higher proportion of rare species have higher productivity. While climatic and edaphic variables are together the strongest predictors of productivity, our results show that the evolutionary diversity of tree species in diverse forest stands also influences productivity. As our models accounted for wood density and tree size, they also suggest that addi tional, unstudied, evolutionarily correlated traits have significant effects on ecosystem function in tropical forests. Overall, our panAmazonian analysis shows that greater phylogenetic diversity translates into higher levels of ecosystem function: tropical forest communities with more distantly related taxa have greater wood productivity.