Search

Subnival habitats of the Central Caucasus represent typical rocky environments with very sparse soil cover and patchy vegetation. We studied how spatial distribution of plant species in a subnival habitat (alpine-nival ecotone) depends on the size of rock particles. We described the distribution patterns of plants and rock particles of various sizes, and examined the possible links between these patterns using correlation analysis and multivariate tests. We found that the largest size class (20-60 cm) was in a strong negative correlation with smaller classes (0.2-0.6 cm, 0.6-2 cm and 2-6 cm), but correlation was insignificant among the largest fragments (6-20 cm) and the soil patches. The CCA included 31 species (frequency >10) and the goodness-of-fit of the obtained ordination was assessed by permutation test. The CCA ordination revealed several species with a clear preference for soils (Carex tristis and Sibbaldia parviflora), while other species preferred mid-sized (20-60 cm) rock particles (Tephroseris karjaginii, Ziziphora puschkinii, Festuca supina, Minuartia inamoena and Saxifraga juniperifolia). Further, Senecio sosnowskyi and Ziziphora subnivalis tended to colonize large (6-20 cm) rock fragments. Overall, our results show a clear differential preference of species for certain sizes of rock particles that conforms well to the patchy pattern of vegetation typical for subnival habitats: many species that prefer a fine grained substratum might clump together at such fine-grained spots and form the patches of associated plants provided there are facilitative interactions among them; the species that prefer coarser-grained substrata might establish as solitary plants outside of the patches.

Background: Cyrtanthus nutans R.A.Dyer is a range-restricted species occurring in northwestern KwaZulu-Natal, South Africa and in Eswatini, and is currently classified as Vulnerable in accordance with the IUCN criteria. Land transformation and disturbance of natural habitats have resulted in an ever-increasing fragmentation of the species’ range. Objectives: This manuscript provides a description of some of the abiotic and biotic factors associated with the remaining natural populations of C. nutans in the Sour Sandveld and Moist Tall Grassland Bioresource Groups of northwestern KwaZulu-Natal. Methods: An investigation was conducted in the northwestern KwaZulu-Natal region to determine the effect that key ecological and anthropological determinants have in influencing the distribution and survival of the species. Data collected included sites of occurrence, estimated population numbers, elevation, ecological factors (soils/geology, climate, veld composition), and human/animal activities. Results: The northwestern KwaZulu-Natal C. nutans populations were found to occur primarily in untransformed veld within the Moist Tall Grassveld, Dry Highland Sourveld and Sour Sandveld Bioresource Groups. It occurs largely on gradients of < 10% on mid- to lower terrain slopes and predominantly within an altitude range of between 1 100 and 1 300 m a.m.s.l. Conclusion: C. nutans occurs in a narrow altitudinal range and has a preference for soils with high nitrogen and organic carbon and low phosphorus and acidity levels. [ABSTRACT FROM AUTHOR]

Elevational range size patterns reflect ecological and evolutionary processes, but they are also affected by geometric constraints. The confounding effect of these constraints led to an ongoing controversy about the elevational Rapoport's rule, which postulates a positive association between the range size and elevation, and about the plausibility of the climate variability hypotheses as its causal explanation.Here we used an advanced null modelling approach to disentangle the interacting effects of geometric constraints and species richness gradients on the elevational range size of vascular plants. We collected extensive field data on elevational distribution for 728 vascular plant species occurring in the Ladakh region, Western Himalaya. We supplied these regional data with subcontinental elevational ranges extracted from the literature. Moreover, we used in situ measured temperatures to quantify temperature variability along an elevational gradient to test the climate variability hypothesis.Observed range size patterns were sensitive to methods used to quantify the average range size. Range truncation disproportionately affected regional ranges of low‐elevation species and resulted in spurious support of elevational Rapoport's rule. However, when the confounding effects of domain boundaries and richness gradient were controlled, our null models revealed only slight deviations from the random expectations of elevational range size patterns, contrasting with the prediction of the Rapoport's rule. In line with these findings, seasonal and diurnal temperature variability did not change with elevation.Synthesis. Geometric constraints combined with underlying species richness gradient create range size patterns seemingly supporting Rapoport's elevational rule. However, null models accounting for these effects indicate that the range size of vascular plants in the Himalayas does not increase with elevation. Given the universality of the geometric constraints and species richness gradient, our results suggest that these confounding factors must be controlled when testing Rapoport's rule. The null model approach described here provides an efficient tool to do that. [ABSTRACT FROM AUTHOR]

Human activities have shaped large-scale distributions of many species, driving both range contractions and expansions. Species differ naturally in range size, with small-range species concentrated in particular geographic areas and potentially deviating ecologically from widespread species. Hence, species' responses to human activities may be influenced by their geographic range sizes, but if and how this happens are poorly understood. Here, we use a comprehensive distribution database and species distribution modeling to examine if and how human activities have affected the extent to which 9,701 vascular plants fill their climatic potential ranges in China. We find that narrow-ranged species have lower range filling and widespread species have higher range filling in the human-dominated southeastern part of China, compared with their counterparts distributed in the less humaninfluenced northwestern part. Variations in range filling across species and space are strongly associated with indicators of human activities (human population density, human footprint, and proportion of cropland) even after controlling for alternative drivers. Importantly, narrow-ranged and widespread species show negative and positive range-filling relationships to these human indicators, respectively. Our results illustrate that floras risk biotic homogenization as a consequence of anthropogenic activities, with narrowranged species becoming replaced by widespread species. Because narrow-ranged species are more numerous than widespread species in nature, negative impacts of human activities will be prevalent. Our findings highlight the importance of establishing more protected areas and zones of reduced human activities to safeguard the rich flora of China. [ABSTRACT FROM AUTHOR]

Northern Zagros forests are one of the most important ecosystems in Iran from ecological and socio-economic points of view. This study was done to determine the most important gradients affecting on plant species distribution by using ordination methods. Environmental variables including inclination, slope aspect, elevation, litter depth, bare soil percentage, soil organic carbon, available P, K, N, soil texture, pH and EC were measured in 60 plots along with vegetation data and canopy cover. Redundancy detrended analysis (RDA) was performed to identify the main environmental gradients. 90 plant species belonging to 75 genus and 32 families were determined. Species belonging to Asteraceae, Apiaceae, Poaceae, and Fabacea families had the most contribution in floristic composition. RDA results showed that with considering spatial autocorrelation of sample plots as covariate, slope aspect, litter depth, canopy cover, C/N, elevation and outcrop explained 30% of the total variations in floristic composition. The results of this study can be used to do more efficient management of these fragile ecosystems.

Zaraninge is a former forest reserve which is now included as part of the Saadani National Park in Bagamoyo District Coast Region. The influence of soil mineral nutrients (N, P, K, Mg and Na) on the pattern of plant species distributions was determined, and transect method was used for data collection. Plant species composition and abundance followed variation in soil nutrient gradients within Zaraninge Forest. Canonical correspondence analysis of soil and plant data showed that calcium, magnesium and phosphorus were the mineral nutrients that significantly influenced the distribution plant species ( P < 0.05) while other nutrients had no significant effects. Data from this study provide evidence of the existing variation in soil nutrient saturation gradients to which plant species distribution responds within the forest. A successful conservation of Zaraninge Forest biodiversity requires protecting the soil which is the necessary habitat for the plant species. [ABSTRACT FROM AUTHOR]

Aim Many studies have forecasted the possible impact of climate change on plant distributions using models based on ecological niche theory, but most of them have ignored dispersal-limitations, assuming dispersal to be either unlimited or null. Depending on the rate of climatic change, the landscape fragmentation and the dispersal capabilities of individual species, these assumptions are likely to prove inaccurate, leading to under- or overestimation of future species distributions and yielding large uncertainty between these two extremes. As a result, the concepts of ‘potentially suitable’ and ‘potentially colonizable’ habitat are expected to differ significantly. To quantify to what extent these two concepts can differ, we developed MigClim, a model simulating plant dispersal under climate change and landscape fragmentation scenarios. MigClim implements various parameters, such as dispersal distance, increase in reproductive potential over time, landscape fragmentation or long-distance dispersal. Location Western Swiss Alps. Methods Using our MigClim model, several simulations were run for two virtual species by varying dispersal distance and other parameters. Each simulation covered the 100-year period 2001–2100 and three different IPCC-based temperature warming scenarios were considered. Results of dispersal-limited projections were compared with unlimited and no-dispersal projections. Results Our simulations indicate that: (1) using realistic parameter values, the future potential distributions generated using MigClim can differ significantly (up to more than 95% difference in colonized surface) from those that ignore dispersal; (2) this divergence increases under more extreme climate warming scenarios and over longer time periods; and (3) the uncertainty associated with the warming scenario can be as large as the one related to dispersal parameters. Main conclusions Accounting for dispersal, even roughly, can importantly reduce uncertainty in projections of species distribution under climate change scenarios. [ABSTRACT FROM AUTHOR]

Flooding affects the abundance and distribution of plant species worldwide. Many plants are damaged or even killed by flooding events due to the associated oxygen deprivation in cells. Stimulated shoot elongation is an important adaptive mode that can restore contact of leaves with the atmosphere above the water surface. This strongly improves inward diffusion of oxygen and the rate of photosynthesis. Fast elongation of sub-merged petioles of the model plant Rumex palustris involves the integrated action of the plant hormones ethylene, auxin, gibberellin, and abscisic acid. The closely related Rumex acetosa is usable to switch on petiole elongation when submerged. In a comparative study of these two Rumex species, we found that the response to the gaseous phytohormone ethylene, which accumulates in plant tissues during submergence, explains their contrasting elongation behavior. In order to study the importance of this shoot elongation response in the distributional patterns of plants in natural floodplains, we quantified the ethylene- induced elongation response of 22 plant species occurring in the Rhine River floodplain. These results were compared with the results of a multivariate analysis based on 84 vegetation surveys performed in the same area. The species compositions of the surveys were grouped along two environmental gradients: flooding duration and soil dehydration after the floodwater subsided. If we superimpose the ethylene-induced elongation capacity on these vegetation data, it becomes clear that the capacity to elongate upon exposure to ethylene positively correlates with flooding duration and negatively with soil dehydration. Based on this analysis, we conclude that the capacity to elongate is an important selective trait in field distribution patterns of plants in flood-prone environments. [ABSTRACT FROM AUTHOR]

Local and regional distributions of Thymus serpyllum, in the southeastern part of Sweden, were examined by combining experimental studiesof recruitment limitation and germination, and descriptive studies of distribution range in relation to habitat and management history. The spatial pattern at a regional scale in the county of Sodermanland was examined in relation to semi-natural pastures and graves from theIron Age. The distribution of T. serpyllum was also examined in two parishes. Thymus serpyllum was exclusively found in managed, unfertilized areas, mainly semi-natural pastures and to some extent in road verges, and almost always in dry parts. Populations of T. serpyllum were found in 32 of the 42 pastures that contained Iron Age graves, butonly in 5 of 42 pastures without graves. The distribution of T. serpyllum was also more or less congruent with the distribution of Iron Age graves, in both parishes. The seed sowing experiment showed that the germination rate, winter survival and recruitment were significantly higher in disturbed (removal of ground cover) plots, for both dry and mesic vegetation. Since the establishment of T. serpyllum occurred both in dry and mesic parts of semi-natural pastures, whereas T. serpyllum is confined to dry parts, the local limitation of distribution may be due to poor dispersal or due to effects acting on later lifecycle stages. The results showed that the regional distribution of T. serpyllum is likely to be dispersal limited -- recruitment after seed sowing was equally good at sites with or without established populations. Seeds survived and germinated after heat treatment. with temperatures at 60 deg.C. 80 deg.C and 100 deg.C, but germination rates were not higher than in the control. The results of this study indicate that the distribution of T. serpyllum is dependent on human activities, both for dispersal and for the maintenance of established populations. Long, continuous management by grazing is obviously important for [ABSTRACT FROM AUTHOR]

A Geographic Information System (GIS) is used to model plant distributions. The model is based on annual mean temperature, humidity, and a georeferenced specimen data base and predicts potential and probable distribution for each taxa in the data base. Potential distributionrange is suitable area determined by climatic constraints. Probable distribution range is here defined as the part of the potential rangewhere a taxon is most likely to be found based on distance to existing collections. Gridded estimates of climatic parameters were calculated based on a Digital Elevation Model and data from ca 100 weather stations. The palm family in Ecuador was used to demonstrate the model. Potential and probable distribution ranges were calculated for eachof the 127 Ecuadorian palm species. Maps of potential and probable species richness were calculated by overlaying and accumulating individual distribution maps. Potential species richness was highest in theAmazon lowland where it reached 60 species and lowest in the higher parts of the Andes and drier parts of the coastal plain. The probablespecies richness followed a similar pattern but was nowhere higher than 47 species. The ratio between potential species richness and probable species richness was used to find areas that are insufficiently sampled. [ABSTRACT FROM AUTHOR]

Geographic plant distribution is often assumed to be predominantly limited directly by the climatic tolerances of species. However, the role of climate is now known to be mainly an indirect one mostly mediating dispersal and establishment, species interactions, or habitat characteristics, which all are often modified by human land use. In these complex systems, negative biotic interactions are predicted to increase in relative importance toward benign climatic conditions. We tested this hypothesis experimentally by exposing plant species with different geographic distribution ranges to different climates, biotic interactions, and land use. Thereby, species predominantly distributed in regions with benign climatic conditions were expected to be better able to cope with negative biotic interactions than species from regions with environmentally stressful climatic conditions. We present results of a fully crossed two‐year transplantation field experiment replicated in 45 plots in three study regions along a precipitation gradient across Germany. We manipulated biotic interactions (presence/absence of competition and mollusk herbivory) in grasslands of different management regimes (meadows, mown pastures, pastures). The transplanted phytometers consisted of six congeneric species pairs, each representing one oceanic and one distinctly more continental range type. The oceanic range type is predominantly distributed in benign climatic conditions in Western Europe, while the more continental type is distributed in regions with more stressful climatic conditions in Eastern Europe. This experimental setting allowed us to study the impact of negative biotic interactions along an abiotic stress gradient under realistic land‐use conditions. Under competition and mollusk herbivory, growth performance was more strongly reduced in continental compared to oceanic species. Range types also differed in their responses to grassland management. Differences in survival between the congeneric species were found to be region‐specific and largely unaffected by biotic interactions and land use. In consequence, our results suggest that local responses to biotic interactions and land‐use practices of otherwise very similar plant species can differ strongly depending on species' large‐scale geographical distribution. Regionally differing responses to biotic interactions also show that local conditions can drastically change responses expected from macroecological theory. [ABSTRACT FROM AUTHOR]

Human activities have shaped large-scale distributions of many species, driving both range contractions and expansions. Species differ naturally in range size, with small-range species concentrated in particular geographic areas and potentially deviating ecologically from widespread species. Hence, species' responses to human activities may be influenced by their geographic range sizes, but if and how this happens are poorly understood. Here, we use a comprehensive distribution database and species distribution modeling to examine if and how human activities have affected the extent to which 9,701 vascular plants fill their climatic potential ranges in China. We find that narrow-ranged species have lower range filling and widespread species have higher range filling in the human-dominated southeastern part of China, compared with their counterparts distributed in the less human-influenced northwestern part. Variations in range filling across species and space are strongly associated with indicators of human activities (human population density, human footprint, and proportion of cropland) even after controlling for alternative drivers. Importantly, narrow-ranged and widespread species show negative and positive range-filling relationships to these human indicators, respectively. Our results illustrate that floras risk biotic homogenization as a consequence of anthropogenic activities, with narrow-ranged species becoming replaced by widespread species. Because narrow-ranged species are more numerous than widespread species in nature, negative impacts of human activities will be prevalent. Our findings highlight the importance of establishing more protected areas and zones of reduced human activities to safeguard the rich flora of China.

The relationships between the distribution of alpine species and selected environmental variables are investigated by using two types of generalized linear models (GLMs) in a limited study area in the Valais region (Switzerland). The empirical relationships are used in a predictive sense to mimic the potential abundances of alpine species over a regular grid. Here, we present the results for the alpine sedge Carex curvula ssp. curvula. The modelling approach consists of (1) a binomial GLM, including only the mean annual temperature as explanatory variable, which is adjusted to species presence/absence data in theentire study area; (2) a logistic model restricted to stands occurring within the a priori defined temperature range for the species -- which allows ordinal abundance data to be adjusted; (3) the two species-response functions combined in a GIS to generate a map of the species' potential abundance in the study area; (4) model predictions filtered by the classes of the qualitative variables under which the species never occur. Such a stratified approach used to better fit the variability within the optimal altitudinal zone for the species. Removing stand descriptions from altitudes too high or too low, where the species is unlikely to occur, enhances the global modelling performance by allowing the identification of important environmental variablesonly retained in the second model. The model evaluation is finally carried out with the gamma-measure of association in an ordinal contingency table. It shows that abundance is satisfactorily predicted for C. curvula. [ABSTRACT FROM AUTHOR]