Altitudinal gradient Research Papers - Academia.edu (original) (raw)

Current study focuses on quantitative description of forest vegetation and associated environmental variables of Gohar Abad Valley, District Diamer. Different sizes of quadrats were used to sample the herbs, shrubs and trees. Forest being... more

Current study focuses on quantitative description of forest vegetation and associated environmental variables of Gohar Abad Valley, District Diamer. Different sizes of quadrats were used to sample the herbs, shrubs and trees. Forest being heterogeneous in vegetation was consisting of conifers and herbaceous angiosperm plant species. Conifers were recorded abundantly from high elevation, i.e. 2600 m to 3200 m. The soil of the forest was sandy loam with pH ranging from highly acidic (4.4) to slightly alkaline (7.13). Angiospermic herbaceous vegetation commonly existed at low elevation in slightly alkaline soil while the pine tree species were present at high elevation in soil having low pH. The organic matter was normal, i.e. 1.1 to 2.23% with 26 to 45% saturation. The potassium contents were 240 to 910 ppm while phosphorous 5-15 ppm. Among the different correlations elevation/saturation was found to be highly significant (p<0.01) while the others non significant. In this study elevation, soil saturation and pH proved to be an important role in the distribution of vegetation. Deforestation, over grazing, human influence and soil erosion were found influencing the distribution and composition of vegetation.

Floristic composition and vegetation structure were described for the woodland vegetation around Dello Menna, Bale zone, southeast Ethiopia. A total 50 (20 m × 20 m) quadrats were sampled to identify and describe plant community types,... more

Floristic composition and vegetation structure were described for the woodland vegetation around Dello Menna, Bale zone, southeast Ethiopia. A total 50 (20 m × 20 m) quadrats were sampled to identify and describe plant community types, species diversity, richness and evenness and to relate the identified plant community types with some environmental factors and describe the population structure of woody plant species. In each quadrat, data on species identity, abundance, height and Diameter at Breast Height (DBH) of woody plant species, altitude and slope were recorded. Vegetation classification was performed using PC — ORD software package. Sorensen’s similarity coefficient was used to detect dissimilarities among communities. Shannon — Wiener diversity index, species richness and Shannon’s evenness were computed to describe species diversity of the plant community types. Results show that a total of 171 vascular plant species representing 53 families were recorded. Fabaceae is the dominant family represented by 13 genera and 26 species (15%) followed by Asteraceae, Lamiaceae and Anacardiaceae with eight species each (4.6%). Based on the results of vegetation classification, three plant communities (Dalbergia microphylla community, Grewia bicolar- Acacia brevispica community, and Combretum molle-Combretum collinum community) are recognized and described. Species richness, diversity and evenness varied among the plant communities. Species richness and diversity exhibit a bell — shaped pattern along altitude. Species turn over among communities more or less follow altitudinal gradients. Tukey’s pairwise comparison of means among the plant community types shows significant variations in altitude, implying that altitude is one of the most important factors determining the distribution of plant communities. The community Dalbergia microphylla type exhibits the highest species richness and diversity. Analysis of population structure of the dominant species reveals various patterns. Future research directions and recommendations are suggested for the sustainable utilization of the vegetation.

Landscape-scale patterns of freshwater fish diversity and assemblage structure remain poorly documented in many areas of Central America, while aquatic ecosystems throughout the region have been impacted by habitat degradation and... more

Landscape-scale patterns of freshwater fish diversity and assemblage structure remain poorly documented in many areas of Central America, while aquatic ecosystems throughout the region have been impacted by habitat degradation and hydrologic alterations. Diadromous fishes may be especially vulnerable to these changes, but there is currently very little information available regarding their distribution and abundance in Central American river systems. We sampled small streams at 20 sites in the Sixaola River basin in southeastern Costa Rica to examine altitudinal variation in the diversity and species composition of stream fish assemblages, with a particular focus on diadromous species. A set of environmental variables was also measured in the study sites to evaluate how changes in fish assemblage structure were related to gradients in stream habitat. Overall, fish diversity and abundance declined steeply with increasing elevation, with very limited species turnover. The contribution of diadromous fishes to local species richness and abundance increased significantly with elevation, and diadromous species dominated assemblages at the highest elevation sites. Ordination of the sampling sites based on fish species composition generally arranged sites by elevation, but also showed some clustering based on geographic proximity. The dominant gradient in fish community structure was strongly correlated with an altitudinal habitat gradient identified through ordination of the environmental variables. The variation we observed in stream fish assemblages over relatively small spatial scales has significant conservation implications and highlights the ecological importance of longitudinal connectivity in Central American river systems.

Climate change is threatening species and habitats. Altitudinal shifts uphill and negative population trends are commonly observed in altitude-related taxa. The bumblebee Bombus alpinus (Linnaeus, 1758) has a disjoint distribution... more

Climate change is threatening species and habitats. Altitudinal shifts uphill and negative population trends are commonly observed in altitude-related taxa. The bumblebee Bombus alpinus (Linnaeus, 1758) has a disjoint distribution restricted to Fennoscandia and the Alps, and is considered threatened. We studied the ecology and distribution of B. alpinus in the Alps, where the endemic subspecies Bombus alpinus helleri Dalla Torre 1882 is found, as a case-model because of its rarity, habitat, and mutual dependence with the ecosystem for pollination and resources. We developed species distribution models including both climatic and habitat variables to obtain the surface suitable for this subspecies and quantified its protected portion. Our analyses indicate that this bumblebee is restricted to the upper altitudes and has a narrow niche mainly related to the presence of glaciers, the cool temperature, a low temperature variation, and a specific range of precipitation. A strong altitudinal shift is also taking place probably due to climate change. After years of no changes in altitudinal distribution, its lowest altitudinal limit has moved up 479 m since the year 1984, while its upper altitudinal limit has remained unchanged. Over half of the suitable area in the Alps is included within protected areas, but conservation has not been planned yet. However, rare species with narrow niche, such as B. alpinus, are highly threatened by climate change. Potential short-term mitigation actions are discussed, including exchange of males between locations and integral protection of prairies in the vicinity of glaciers.

Using pitfall traps, wandering spiders (Arachnida: Araneae) were sampled in a nested design from three different localities in the mountainous arid ecosystem of South Sinai at low, middle, and high altitudes. Habitat type and altitude... more

Using pitfall traps, wandering spiders (Arachnida: Araneae) were sampled in a nested design from three different localities in the mountainous arid ecosystem of South Sinai at low, middle, and high altitudes. Habitat type and altitude were clearly different among the three localities. Spider diversity per trap varied spatially and temporally among and sometimes within localities. Altitude, relative humidity, and temperature had different effects, either positive or negative with the abundance of different families. Habitat heterogeneity within a locality may also affect spider diversity. The different localities had distinct and characteristic groups of spiders responding to altitude and habitat characteristics.

The study of diversity gradients is a frequent approach to understand evolutionary processes that structure communities. Altitudinal gradients allow the analysis of community spatial responses to environmental fluctuations. One... more

The study of diversity gradients is a frequent approach to understand evolutionary processes that structure communities. Altitudinal gradients allow the analysis of community spatial responses to environmental fluctuations. One interesting place to study altitudinal gradients is the Andes system because of the coexistence of isolated and continuous mountain ranges. We investigated the altitudinal turnover of species in peripheral mountainous systems by analyzing the structure of dung beetle assemblages along a complete gradient in the Sierra Nevada de Santa Marta, Colombia. Seven sites ranging from 480 to 2,890 m were evaluated, using linear transects of pitfall traps. A total of 2,992 individuals and 46 species were collected. Abundance, richness, and diversity diminished with altitude, revealing significant differences among sites. Some genera appeared at certain altitudes and most species appeared at unique sites, indicating a marked altitudinal turnover. A similarity analysis demonstrated the existence of separate lowland and high mountain groups with a turnover at 1,200–1,600 m asl. We registered for the first time a species replacement between Scarabaeinae (low-lands) and Aphodiinae (highlands) in the Neotropical region. Our results largely agree with the species pattern described for Mesoamerica, although, in this case the altitudinal turnover is more evident, unveiling a transition zone between lowland and high mountain fauna elements. This result suggests an equilibrium between a weak horizontal colonization and a strong vertical turnover, that appears to be higher in isolated mountains. Future investigations with other insect groups are necessary to corroborate this altitudinal pattern in isolated mountains.

Landforms with steep environmental gradients provide natural laboratories for studying regional dynamics of diversity. The Soutpansberg range in South Africa presents contrasting habitats and climatic conditions on its northern and... more

Landforms with steep environmental gradients provide natural laboratories for studying regional dynamics
of diversity. The Soutpansberg range in South Africa presents contrasting habitats and climatic
conditions on its northern and southern slopes. Scorpions are well adapted to arid environments, with
greatest diversity in temperate deserts, but few studies have investigated the effects of aspect and
altitude on scorpion diversity. We surveyed scorpion diversity along an altitudinal transect across the
Soutpansberg by actively searching for scorpions during the night and day. Patterns of scorpion diversity
along the transect were compared to those of ants and woody plants. Unlike these taxa, scorpions
exhibited a significant difference in species richness between slopes; higher on the arid northern slope,
and greater at lower than higher altitudes. Endemic taxa were restricted to mid-to higher altitudes of the
northern slope. Species turnover decreased at higher altitudes and assemblage structure was influenced
by slope, altitude and rock cover. The Soutpansberg appears to be a hotspot of scorpion richness and
mimics patterns of diversity in southern Africa. The richness and endemism of the scorpion fauna of the
arid northern slopes and foothills of the Soutpansberg emphasizes the need to prioritize the conservation of these areas

Aim: Components of scale, such as grain, focus and extent, influence the spatial patterns of alpha and gamma diversity and the relationships between them. We explored these scale relations by testing whether the gamma diversity and alpha... more

Aim: Components of scale, such as grain, focus and extent, influence the spatial patterns of alpha and gamma diversity and the relationships between them. We explored these scale relations by testing whether the gamma diversity and alpha diversity along an elevation gradient were related independent of scale and whether the elevational patterns of herbaceous and woody species richness were dependent on scale. Location: Langtang National Park, Nepal. Methods: We estimated alpha diversity (plot richness) for woody and herbaceous plant species along an alpine elevation gradient (3,900–5,000 m a.s.l.) in nested plots of 1 m 2 , 16 m 2 and 100 m 2 and gamma diversity (regional richness) from published sources. Generalized linear modelling was used to analyse alpha and gamma diversity and their correspondence at different grain sizes. Results: Elevational trends of gamma and alpha diversity were significantly correlated for both woody and herbaceous species at all grain sizes. The concordance increased with increasing grain size and area for gamma diversity estimation, particularly for the monotonously decreasing elevational gamma and alpha diversity patterns of woody species. The hump-shaped patterns of elevational gamma and alpha diversity for herbaceous species were also significantly correlated, but the concordance between the alpha diversity of herbaceous species and local gamma diversity was stronger. Elevational patterns of alpha diversity were coarsely consistent across grain sizes, although the patterns became more pronounced at larger grain sizes. Main conclusions: The correspondence of elevational gamma and alpha diversity was largely scale invariant, implying that elevational and possibly other geographical diversity patterns can reliably be studied at different spatial scales. Nonetheless, the alpha diversity pattern was the least pronounced at fine grain size, particularly for woody life-forms. This finding suggests that for large-scale patterns such as eleva-tional gradients at regional or continental scales, coarse grain sizes and large areas for gamma estimation are more appropriate.

We assess Holocene environmental change at alpine Lake Njulla (68° 22'N, 18° 42'E, 999 m asl) innorthernmost Sweden using sedimentary remains of chironomid head capsules anddiatoms. We apply regional calibration sets to... more

We assess Holocene environmental change at alpine Lake Njulla (68° 22'N, 18° 42'E, 999 m asl) innorthernmost Sweden using sedimentary remains of chironomid head capsules anddiatoms. We apply regional calibration sets to quantitatively reconstruct meanJuly air temperature (using chironomids and diatoms) and lake-water pH (using diatoms). Both chironomids and diatoms infer highest temperatures (1.7–2.3° C above present-day estimates, includinga correction for glacio-isostatic land up-lift by0. 6° C) during the early ...

Aim: To test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters. Location: A 2,000-m long... more

Aim: To test if tree species richness and forest structure drive spatial variation in avian communities along a tropical elevation gradient and to present information about the role of detailed forest parameters. Location: A 2,000-m long elevational gradient of tropical forest on Mt. Cameroon, west-central Africa. Taxon: Birds and trees. Methods: We performed bird censuses and vegetation mapping at the same plots across six forested sites at elevations of 350, 650, 1,100, 1,500, 1,850, and 2,200 m a.s.l., with 16 plots per elevation. We tested the effects of elevation, forest structure and tree diversity on the species richness, functional diversity and β-diversity of birds (Bray-Curtis dissimilarity). We used conditional inference trees based on random forests (RF) to investigate these relationships across all elevation sites as well as within elevations. Results: Both tree and bird species richness declined monotonically with elevation. Vegetation structure correlated with elevation, and all vegetation attributes

The work deals with the confrontation of two approaches in vegetation science, which already had their origins at the beginning of the past century: gradient analysis and classification of communities. We tested whether samples are... more

The work deals with the confrontation of two approaches in vegetation science, which already had their origins at the beginning of the past century: gradient analysis and classification of communities. We tested whether samples are arranged along gradients according to the individualistic or the integrative concept. We studied gradients in several case studies – successional, altitudinal, gradient of human impact, phenological, macroecological, (phyto)geographical – and tried to detect the main gradient (by direct or indirect ordination methods) and arrange the plant assemblages along the gradient. We then applied different classification methods to test whether it is possible to detect discrete plant communities. We analyzed the secondary succession of birch forests in Slovenia, the process of autosuccession of Pinus brutia in Turkey, the altitudinal distribution of communities in rock crevices on silicate bedrock in Slovenia, the gradient of spruce planting in beech forest, the influence of the introduction of non-native tree species into forests, the macroecological and phenological development of weed vegetation in Europe, and the circum-Adriatic pattern of broadleaved ravine forests. The results show that, in most cases, the turnover of species composition along the gradient, according to the integrative concept, is due to species interactions. This enables us to detect and describe discrete plant communities in terms of the central European Braun-Blanquet method.