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Questions: What will happen to species diversity in a forest when exploitation of the canopy foliage terminates? The foliage of the main canopy tree of a mountain evergreen oak forest was harvested at different intensities prior to a forest survey in 1993 and resampled in 2013 after the harvest of canopy foliage ceased (1995). We predict a decrease in herbaceous species richness with increasing canopy cover, and an opposite trend for vines and woody species. We hypothesise that plant species' alpha and beta diversity will change most in the plots where foliage was most intensively harvested while showing less change in the plots that underwent almost no harvesting. Location: Temperate evergreen laurel–oak forest in the Himalaya, Nepal. Methods: We resampled all non‐epiphytic vascular plants in 64 plots of 10 m × 10 m in 2013, following the same protocol used in 1993. Plant species were categorised into three life forms; woody (except woody vines), herbaceous, and vines. Uni‐ and multivariate numerical methods were used to assess the significance of the changes in species diversity for different life forms. Results: Vines and woody species increased, whereas herbaceous species decreased, but overall gamma diversity remained unchanged. The overall alpha richness for herbaceous species decreased, while the opposite is true for woody and vine richness. Herbaceous richness decreased and woody richness increased in the areas with low and intermediate disturbance (in 1993), whereas vines remained unchanged. Only vine richness increased in the area that was very disturbed in 1993. Total species richness as well as herbaceous and vine richness decreased with increasing tree canopy cover. Conclusions: Plots that were intensively harvested in 1993 did not recover their richness because vines dominated the forest floor. Management should prevent overexploitation, and only allow low‐intensity canopy disturbance, which may facilitate habitat diversity and thereby enhance species richness. [ABSTRACT FROM AUTHOR]

Aim: Existing phytogeographical frameworks for tropical Africa lack either spatial completeness, unit definitions smaller than the regional scale or a quantitative approach. We investigate whether physical environmental variables can be used to interpolate floristically defined vegetation units, presenting an interpolated, hierarchical, quantitative phytogeographical framework for tropical Africa, which is compared to previously defined regions. Location: Tropical mainland Africa 24°N to 24°S. Taxon: 31,046 vascular plant species and infraspecific taxa. Methods: We calculate a betasim dissimilarity matrix from a comprehensive whole‐flora database of plant species distributions. We investigate environmental correlates of floristic turnover with local non‐metric multidimensional scaling. We derive a hierarchical biogeographical framework by clustering the dissimilarity matrix. The framework is modelled using a classification decision tree method and 12 physical environmental variables to interpolate and increase the resolution of the framework across the study region. Results: Floristic turnover is related strongly to water availability and temperature, with smaller contributions from land cover, topographic ruggedness and lithology. Region can be predicted with 90% accuracy by the model. We define 19 regions and 99 districts. We find a novel arrangement of the arid regions. Regional subdivision within the savanna biome is supported with minor variation to borders. Within the forests of west and central Africa, our whole‐flora gridded regionalization supports the divisions identified by a previous analysis of trees only. Main conclusions: Physical environmental variables can be used to predict floristically defined vegetation units with very high accuracy, and the approach could be pursued for other incompletely sampled taxa and areas outside of tropical Africa. Geographical coherence is higher than in previous quantitative phytoregional definitions. For most tropical African vascular plant species, we provide predictions of which species will occur within each mapped district and region of tropical Africa. The framework should be useful for future studies in ecology, evolution and conservation. [ABSTRACT FROM AUTHOR]

This study explores the relationship between the species composition of lichen and vascular plant species with microtopography at fine scale. We conducted our study in Hardengervidda National Park, Norway. Specifically, we aim to test whether the species richness of different plant life-forms peaks at middle of the microtopography gradient, and then explain the observed patterns with an aid of snow cover gradient along microtopography and snow cover. We sampled 69 species of vascular plants and lichens in 151 plots of 4 m2 along 23 transects during summer on Tronsbu, Sandhaug and Besso. Detrended correspondence analysis (DCA) was performed to explore how microtopographical gradient was related to the variation in the species composition. One-way ANOVA was performed to test the microtopographic variability in species richness. Afterwards, generalized linear model (GLM) was used to reveal species richness patterns along the snow cover gradient. The first axis in DCA represents the complex gradient from snow free ridge to wet snowbed habitats and the second axis represents a gradient from acidic to calcareous sites. Lichens species richness is greater in ridge than in snowbeds, while all other life forms follow the opposite trend. Species richness for total plant species, vascular plant species and herbaceous plant species increased with increase in weighted average snow indicator value (WASI), whilst species richness for lichen species declined substantially towards the maximum WASI value. In contrast, species richness for dwarf shrub species showed a unimodal relationship with WASI. This study shows that liquid water availability provides a good potential explanation for species composition and richness in mountains, which is controlled by snow cover and prevalent wind direction. [ABSTRACT FROM AUTHOR]

Aim Climate change is expected to modify growth trends of forests around the world. However, this modification may vary in strength and intensity across a species' biogeographical range. Here, we study European populations of silver fir ( Abies alba) across its southern distribution limits in Spain, Italy and Romania. We hypothesized that growth trends of silver fir will differ across its distribution range, with a marked decline in growth in drought-prone regions near the species' southernmost biogeographical limits. Location Europe (Spain, Italy, Romania). Methods We collected tree-ring data from at least 1300 silver fir trees located in 111 sites. The dataset was used to assess and model growth trends, quantified as changes in basal area increment, and to determine how growth responds to climate. Results We found contrasting patterns of basal area increments among countries and sites. Populations of silver fir located outside the Mediterranean area (e.g. northern Italy, Romania) have shown a clear increase in growth over the last two decades, whereas most populations in Spain and southern Italy have displayed a marked decline in growth since the 1980s. The growth of silver fir forests at the south-western distribution limit is severely constrained by low spring-summer water availability, whereas growth of silver fir forests in non-Mediterranean areas is limited by cold conditions in late winter to early spring. Main conclusions Climate warming is distinctly modifying growth patterns and responses to climate in silver fir across most of the species' European distribution area. In south-western Europe the reduction in growth of many populations is related to an observed increase in aridity, whereas in more temperate areas warming is enhancing growth. Our results confirm a decline in the growth of silver fir at its south-western distribution limits as a consequence of climate warming. [ABSTRACT FROM AUTHOR]

Distribution patterns of plant species are believed to be impacted by small-scale habitat heterogeneity. However, there have been few comparative studies examining how woody vegetation composition and diversity varies with aspects of different orientations in the Trans-Himalayan region at a local scale. Here, we examined the effects of incoming solar radiation on variation in woody species composition and compared the diversity between the northeast- and southwest-facing slopes in a Trans-Himalayan valley of Nepal. We also examined the implicit interactions between slope orientation and land use in determining the compositional variations between the slopes. We selected two pairs of northeast- and southwest-facing slopes where the first pair has a similar land use and differs in exposure only (Pisang site) while the other pair has clear differences in land use in addition to slope exposure (Braka site). In each site, we sampled 72 plots (36 on each slope) in which the presence and absence of woody species, environmental variables, and disturbance were recorded. Correspondence Analysis (CA) results suggested that the woody species composition significantly varied between northeast- and southwest-facing slopes at both sites, and was significantly correlated with measured environmental variables such as radiation index, altitude, and canopy openness. In the Braka site, mean alpha diversity was significantly higher on southwest-facing slopes. In contrast, beta diversity and gamma diversity were greater on northeast-facing slopes at both sites. Our results suggest that topographic variables (e.g., radiation index) affect species composition between the slopes, likely due to their influence on small scale abiotic environmental variables. However, the effects of land use, such as livestock browsing/grazing may interact with the effects of slope exposure, effectively reducing differences in species composition within slopes but enhancing the differences in beta diversity between contrasting slopes in the Braka. We conclude that slope orientation and land use are important factors in structuring the woody species composition and diversity in the arid Trans-Himalayan region. We suggest that both environmental and land use variables should be taken into consideration in future studies on plant community structure along the cultural landscapes. [ABSTRACT FROM AUTHOR]

Background:Changes in land use and climate during recent decades have initiated plant succession in the Sahel zone, but few sites have historic records for comparison. One exception is the conjunction of the Sahel and the Red Sea Hills, where north-easterly winds carry sea-mist during winter and create a moisture–temperature-gradient in a limited area, Erkowit, known for its Abyssinian evergreen Afromontane vegetation, 10 km away from desert shrub. Aims:Our aim was to study the effects of land-use changes and climate change on vegetation development in Erkowit. Methods:An identical method was used to record perennial plants on 44 small hills in 1953, 1989, and 2009. Detrended Correspondence Analysis was used to identify the spatial gradient from desert to hill summits, and the temporal gradient, based on time of sampling. Changes in perennial plants were related to species traits (e.g. toxic) and temperature optima which were derived from the elevation ranges of the species as given in the Flora of Ethiopia and Eritrea. Results:The floristic/vegetation gradient from hot-desert shrub to a cool summit with Afromontane vegetation persists, but there were significant temporal trends in vegetation, correlated with species temperature ranges and toxicity. Afromontane plants have decreased, whereas browsing-tolerant Sahelian species have increased on the hills. Conclusions:Browsing may be an important driver of the observed vegetation change. Climate change has also played a role and affected mostly the species on the cool and moist summits. [ABSTRACT FROM PUBLISHER]

Changes in species composition and richness across the sub-alpine forest ecotone are well known phenomena. The total number of species at a regional scale drops substantially above the forest-line in the central Himalayas of Nepal. This study tests the effect of a forest border ecotone on a local scale using a grain size of 100 m2. We sampled a set of vertical transects across a sloping sub-alpine forest line where canopy and temperature covary, and a set of horizontal transects across a forest ecotone where there was no altitudinal difference to eliminate the influence of temperature. Detrended correspondence analysis revealed a continuous change in species composition across the forest border ecotone. Species turnover was, in general, low, and species richness did not vary very much between the forest and open landscapes. We attribute this to the grazing and browsing pressure in the area, which may have lowered the tree line. A reduced tree line compared to the climatic limit may facilitate enhanced species richness above the forest line. There was no significant difference in species richness between forest and open landscapes along horizontal transects where temperature variations were minimized. This study exemplifies the difficulties encountered on a local scale when one aims to test diversity hypotheses deduced from general models on forest-ecotone effect and mass effect. The low species turnover and minor differences in alpha diversity may be because the area is a cultural landscape and the homogenizing effect of domestic animals overrides some of the edge effects of the ecotone. [ABSTRACT FROM AUTHOR]

The hump-shaped relationship between plant species richness and biomass is commonly observed at fine scale for herbaceous vegetation in temperate climates. This relationship predicts that herbaceous species richness is highest at an intermediate level of biomass that corresponds to moderate competition or disturbance. However, this relationship has not previously been investigated in high arid sub-alpine mountain grasslands. We tested the humped-back prediction in the arid Trans-Himalayan mountain grassland with a seasonal grazing system. The study area is located in the bottom of a U-shaped valley, in the Manang district (3500 m a.s.l.). We sampled two hundred plots (1m x 1m) in two different types of pastures: common pasture and old field, which both have similar grazing practices. There was a significant unimodal relationship between species richness and biomass only in the common pasture, and when the two sites were analyzed together. The species turnover is estimated by DCA in standard deviation unit. The turnover was lower in the old field than in the common pasture. The unimodal relationship between plant species richness and biomass did not disappear after accounting for unknown environmental gradients expressed as DCA (detrended correspondence analysis) axes and spatial variables. The species richness is highest at 120 ± 40 g/m2 . The results indicate that a hump-shaped relationship is also found in arid Trans-Himalayan grasslands. [ABSTRACT FROM AUTHOR]

Abstract Aim Species richness and endemic richness vary along elevation gradients, but not necessarily in the same way. This study tests if the maxima in gamma diversity for flowering plants and the endemic subset of these plants are coherent or not. Location The study was conducted in Nepal, between 1000 and 5000 m a.s.l. Methods We used published data on distribution and elevational ranges of the Nepalese flora to interpolate presence between maximum and minimum elevations. Correlation, regression and graphical analyses were used to evaluate the diversity pattern between 1000 and 5000 m a.s.l. Results The interval of maximum species endemic to Nepal or the Himalayas (3800–4200 m) is above the interval of maximum richness (1500–2500 m). The exact location of maximum species density is uncertain and its accuracy depends on ecologically sound estimates of area in the elevation zones. There is no positive statistically significant correlation between log-area and richness (total or endemic). Total richness is positively correlated with log-area-adjusted, i.e. estimated area adjusted for the degree of topographic heterogeneity. The proportion of endemic species increases steadily from low to high elevations. The peak in endemism (c. 4000 m) corresponds to the start of a rapid decrease in species richness above 4000 m. This may relate to the last glacial maximum (equilibrium line at c. 4000 m) that penetrated down to 2500–3000 m. This dynamic hard boundary may have caused an increase in the extinction rate above 4000 m, and enhanced the probability of isolation and facilitated speciation of neoendemics, especially among genera with a high proportion of polyploids. Main conclusions The results reject the idea of corresponding maxima in endemic species and species richness in the lowlands tentatively deduced from Stevens’ elevational Rapoport effect. They confirm predictions based on hard boundary theory, but hard-boundaries should be... [ABSTRACT FROM AUTHOR]

Compares different null models for plant species richness patterns in the Nepalese Himalayas. Species presence in different recorded altitudinal ranges; Estimation of species richness by interpolation; Linear relationship between species richness and altitude.

Summary 1.The relationship between biomass and species richness in temperate vegetation has been described as a hump-back response model. The hump-back model predicts that herbaceous species richness is highest at an intermediate level of biomass. However, this has not been investigated in arid-zone grazing lands. 2.We tested the hump-back prediction in an arid tropical grazing region in northern Kenya where a seasonal grazing exclosure system is practised. We compared vegetation structure, species richness and composition on an open range and exclosures at five sites to elucidate the potential mechanisms behind variation in species richness. 3.More biomass was accumulated within seasonal exclosures than in continuously grazed areas. Species richness in exclosure plots varied from 5·3 to 8·3 species m-2 , while that in open plots varied from 5·1 to 7·5 species m-2 . A pair-wise test showed no difference in two of the five sites with respect to both total and herbaceous species richness. 4.The primary floristic gradient illuminated through ordination was related to biomass, while the secondary gradient was related to species richness. The exclosure plots had more abundant species, especially compared with open plots, which had more rare and occasional species. A total of 37 herbaceous species was recorded; 22% were indifferent to grazing, 30% grazing intolerant and 48% promoted by grazing. 5.The relationship between biomass and herbaceous species richness showed (i) no trend within the exclosures (maximum biomass 800 g m-2 ); (ii) a positive trend in the open grazing land (maximum of 500 g m-2 ); and a hump-back pattern when (i) and (ii) were analysed together. Optimum richness corresponded to a biomass level of 400–500 g m-2 . Species richness declined with increase in age of exclosures. 6.We confirmed that species richness will decline when biomass exceeds 500 g m-2 ,... [ABSTRACT FROM AUTHOR]

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