Grazing,forest density,and carbon storage: towards a more sustainable land use in Caatinga dry forests of Brazil

Grazing is the main land use in semi-arid regions of the world, and sustainable management practices are urgently needed to prevent their degradation. However, how different grazing intensities affect forest density and ecosystem functions is often not sufficiently understood to allow for management adaptations that safeguard the ecosystems and their functions in the long run. We assessed the aboveground carbon stocks and plant densities along a grazing gradient in the semi-arid seasonally dry tropical forest of north-eastern Brazil (Caatinga). On 45 study plots, we analysed the aboveground carbon stocks of the vegetation and determined forest density and recruitment as well as the population structure of the most abundant tree species. Grazing intensity was accounted for based on the weight of livestock droppings and classified as low, intermediate, or high. Mean aboveground carbon stock was 15.74?±?1.92 Mg ha^?1 with trees and shrubs accounting for 89% of the total amount. Grazing at high intensities significantly reduced aboveground carbon stocks of herbs but not of other plant functional types. Instead, aboveground carbon stocks of trees and shrubs were negatively related to altitude above sea level, which is a proxy for reduced water availability along with lower anthropogenic impact. The population structure of the most common tree species was characterised by abundant recruitment, irrespective of grazing, whereas the recruitment of less frequent woody species was negatively affected by grazing. Overall, our data imply that grazing and forage management need to be adapted, including the reduction of free-roaming livestock and storage of fodder, to maintain carbon storage and forest density.     

Land-use and land-cover effects on regional biodiversity distribution in a subtropical dry forest: a hierarchical integrative multi-taxa study

Latin American subtropical dry ecosystems have experienced significant human impact for more than a century, mainly in the form of extensive livestock grazing, forest products extraction, and agriculture expansion. We assessed the regional-scale effect of land use and land cover (LULC) on patterns of richness distribution of trees, birds, amphibians, and mammals in the Northern Argentine Dry Chaco (NADC) over c. 19 million hectares. Using species distribution models in a hierarchical framework, we modeled the distributions of 138 species. First, we trained the models for the entire Argentinean Chaco with climatic and topographic variables. Second, we modeled the same species for the NADC including the biophysical variables identified as relevant in the first step plus four LULC-related variables: woody biomass, distance to crops, density of livestock-based rural settlements (puestos), and vegetation cover. Third, we constructed species richness maps by adding the models of individual species and considering two situations, with and without LULC variables. Four, richness maps were used for assessing differences when LULC variables are added and for determining the main drivers of current patterns of species richness. We found a marked decrease in species richness of the four groups as a consequence of inclusion of LULC variables in distribution models. The main factors associated with current richness distribution patterns (both negatively) were woody biomass and density of livestock puestos. Species richness in present-day Semiarid Chaco landscapes is strongly affected by LULC patterns, even in areas not transformed to agriculture. Regional-scale biodiversity planning should consider open habitats such as grasslands and savannas in addition to woodlands.     

Communities of trees along a tropical forest restoration gradient

Increasing rates of deforestation in tropical forests have been linked to agriculturalists. A critical concern generating debate is how well communities of trees recover into a more species rich ecosystem after restoration planting. The aim of the study was to evaluate the pattern of recovery of communities of tree, assess the influence of Acanthus pubescens, Lantana camara and Pennisetum purpureum, on the recovery as well as how restoration planting facilitates recruitment of other native tree seedlings along a gradient of forest restoration in Kibale National Park, Uganda after evictions of illegal settlers. We studied six restoration forests ranging in age from 3 to 16 years, naturally regenerating and three primary forests. Our results showed that recovery with natural regeneration was more effective than restoration planting although the latter enhanced recruitment of other native tree seedling. Tree recovery was generally correlated with age so that species density and diversity increased although at different rates. A reverse pattern was found for dominance but no clear pattern was found for tree density (individual/ha). Communities of tree showed directional patterns of change however community composition were still distinct among the different forests. A. pubescens, L. camara and P. purpureum negatively correlated with species density, tree density and diversity but a positive correlation was found for dominance. Restoration planting can reestablish forests with high species density, tree density and diversity, but this is dependent on age and the extent of the herbs, grasses and shrubs cover in tropical forests.     

Changes in the structure of a <Emphasis Type="Italic">Dactylorhiza incarnata</Emphasis> (L.) Soó population during the overgrowing of a meadow-bog community complex in the Moscow region

The overgrowing of meadow-bog communities by shrubs and trees (age 5–40 years, crown closure 0.4–0.9) leads to a decrease in incident illumination. As a consequence, juvenile and generative plants disappear from D. incarnata population loci, their average ecological density decreases, and the loci enter the state of regression. The digging activity of wild boars disrupts phytocenotically closed groups of longirhizomatous herbs, thereby creating favorable conditions for seed reproduction of D. incarnata. The species begins to form population loci with a complete ontogenetic spectrum and high ecological density, eventually restoring the normal (definitive) population structure.     

Plant biodiversity and ethnobotany inside the projected impact area of the Upper Seti Hydropower Project,Western Nepal

A survey of plant biodiversity and ethnobotany was conducted along the Seti river banks in the Tanahun district of Western Nepal. This area, home of the Magar ethnic group, will be impacted by a major hydropower project, currently under feasibility study. The objective of the study was to document plant biodiversity and ethnobotany in order to suggest appropriate conservation and management strategies. Botanical sampling was conducted inside quadrats and along transects. A total of 221 plant species were recorded in the study area, distributed as herbs (80 species), trees (68), shrubs (28), climbers (19), pteridophytes (18), lianas (5), and epiphytes (3). Twelve of the inventoried species figure in one or more conservation categories identified by various national or international agencies. Group discussions and personal interviews allowed to find out that 43% of the species were ethnobotanically important for the local people and that most were used as medicine, food, or timber. We propose specific species for sustainable use programs based on certain criteria. The area is very important in terms of plant biodiversity and ethnobotany, and hence, immediate implementation of conservation measures is recommended to maintain the high social, ecological and economic values of the area.     

三峡库区常绿落叶阔叶混交林的监测研究

生物多样性的长期动态监测是生物多样性研究的热点之一。陆生植物监测实验站作为长江三峡工程生物与环境监测系统的重点站,完成了大量的野外监测样地建立工作,为今后的长期研究打下了良好的基础。以米心水青冈及曼青冈组成的常绿落叶阔叶林的相关研究为例,介绍了陆生植物观测实验站现阶段关于监测方面的部分研究工作。在多个尺度下对米心水青冈及曼青冈两种优势种进行格局分析,结果表明两者均为聚集分布,米心水青冈的聚集强度高于曼青冈。按1 ～4 cm, 4 ～ 8 cm及8 cm以上3个径级对曼青冈分布格局进行比较,各径级间聚集强度相似,这与群落年龄、特殊的地形环境及种群的生态习性有关。群落的地形异质性研究表明0.96 hm2范围内坡度及坡向存在明显的差异,研究范围内样方的平均坡度在18.2°～ 74.6°之间。坡向可以分为南坡、西南坡及东南坡3部分。地形的异质性影响着群落的内部结构,植物与地形因素的相关分析表明不同的种对地形的适应性不同,群落中的24种主要植物可以分为4个生态种组。     

分布式TOPMODEL模型在清江流域降雨径流模拟中的应用

以清江流域上游为研究区域，探讨TOPMODEL模型在大流域的应用；对比了SRTM和地形图两种DEM数据在流域地形指数计算及降雨径流模拟中的差异，结果表明，虽然不同DEM计算得到的地形指数和模型率定参数存在较大差异，但是模拟效率基本相同，SRTM数据作为全球覆盖的免费高分辨率DEM数据将极大促进TOPMODEL模型的应用；分析了TOPMODEL模型在大流域中应用存在的局限性，在此基础上，构建了基于子流域的松散耦合的分布式TOPMODEL模型，提出了利用流域实际下垫面数据进行模型参数率定的方法，探讨了子流域划分详细程度对模拟结果的影响，结果表明，分布式TOPMODEL模型充分考虑了流域降雨和下垫面属性空间不均匀性对水文过程的影响，模拟效率高于传统TOPMODEL模型，随着子流域数目的增加，模型在率定期和校验期的效率均呈上升趋势，但是到达一定程度之后，受降雨等输入参数及模型计算误差所限，增加子流域个数不能继续提高模拟效率.     

Effect of three georges reservoir (Yangzi River) on the plant species richness in drawdown zone downstream the tributary river (Pengxihe River)

In order to understand the spatial pattern of plant community and the maintenance mechanism of biodiversity in littoral zone of Three Gorges Reservoir, 110 km stretches of Pengxihe River (from estuary to the backwater of Three Gorges) were chose to study. We investigated species composition and environmental variables along 50 m long stretches of riverbank between the high-water level and the lowest summer water level, at a 5 km interval. The results showed that: (1) along longitudinal gradients, longitudinal species richness, longitudinal shrub species richness and longitudinal herb species richness were significantly related to distance to estuary; (2) along lateral gradient, there were visible different changes in all kinds of types (lateral species richness, lateral tree species richness, lateral shrub species richness, lateral herb species richness). Along lateral gradient, species richness and herb species richness first increased with the elevation then reduced with it, trees and shrubs species richness increased with the elevation. (3) Correlation analyses showed that substrate types were correlated with the longitudinal species richness, without considering the distance to estuary. Soil moisture and substrate heterogeneity were correlated with lateral, species richness. These results indicated that, along longitudinal gradient of the river, distance to estuary plays an important role in species richness, and along lateral gradient spatial heterogeneity due to inundation and flooding plays an important role in forming a new pattern of plant community in the littoral zone of Three Gorges Reservoir Region. Because of special hydrological dynamics, plant in the littoral zone of Three Gorges, are gradually form a unique spatial pattern to some extent, though it had the same change law with riparian plant of a natural river.     

三峡水库蓄水对长江干流河岸植物组成的影响

三峡水库采取“冬蓄夏泄”的水位调度方式，导致淹没区的原河岸带和陆地植物及其群落的大量消失，并将逐渐形成适应消落带环境的植物群落。在忠县选择长江干流北岸典型区域建立固定样区，对蓄水前（2007年）后（2015年）158~173 m高程段植物组成变化进行研究。结果发现：（1）蓄水前，样区共有维管束植物106种（隶属47科96属），优势植物生活型为多年生草本、一年生草本和灌木；蓄水后维管束植物种类下降了45.28%，只有58种（隶属26科51属），其中多年生草本所占比例由蓄水前的40.57%上升为43.10%，一年生草本由蓄水前的28.30%上升为48.28%，灌木已不再是优势植物生活型。（2）蓄水后，狗牙根（Cynodon dactylon）的重要值由蓄水前的1.72%增大到45.06%，荩草（Arthraxon hispidus）和白茅（Imperata cylindrica）则由之前的6.81%和16.48%下降到0。样区下部的优势物种由蓄水前的荩草、白茅和喜旱莲子草（Alternanthera philoxeroides）变为狗牙根、稗（Echinochloa crusgalli）和水蓼（Polygonum hydropiper）；样区中部的优势物种由蓄水前的荩草和白茅变为狗牙根、苍耳（Xanthium sibiricum）、鬼针草（Bidens pilosa）和喜旱莲子草；样区上部的优势物种由蓄水前的白茅变为狗牙根、鬼针草和狗尾草（Setaria viridis）。（3）蓄水前，158~173 m物种数范围为42~66，各高程段物种数无明显变化趋势；蓄水后，158~173 m物种数范围为14~43，各高程段物种数差异明显，且呈现出随高程上升而增加的趋势，而物种多样性指数和物种均匀度指数均未随高程变化呈现出明显的变化趋势。研究表明，三峡水库运行导致消落带植物种类下降了近50%，许多不适应水淹的物种消失或优势度减小；一些克隆能力强的多年生草本竞争优势明显，部分种子扩散能力强的一年生草本依靠种子休眠的形式躲避冬季长期淹水，也能适应消落带这种特殊的生境；不同高程段消落带生态系统受淹水深度、淹水时间、淹水频率的影响不同，导致植物群落的物种组成和物种分布存在显著差异，特别是优势种变化明显。 关键词： 狗牙根；一年生草本；多年生草本；物种丰富度；水位变动     

Inhibition of restorative succession by invasive plant species: Examples from southeastern Belarus

Consideration is given to the examples of suppression of restorative succession by invasive plant species (Solidago canadensis L., Helianthus subcanescens (A. Gray) E. Watson, Impatiens glandulifera Royle) in anthropogenic landscapes of southeastern Belarus. Characteristics of communities blocking the succession process have been revealed: low species richness, dominance of alien species in coverage, high level of synanthropization, and the absence of natural regeneration of trees and shrubs. It is suggested that a delay in succession is caused by the suppressing influence of transformer species on seed germination in apophytic trees.     

Decline of woody vegetation in a saline landscape in the Groundnut Basin,Senegal

Several studies have documented that vegetation in the Sahel is highly dynamic and is affected by the prevailing climatic conditions, as well as by human use of the areas. However, little is known about vegetation dynamics in the large saline areas bordering the rivers of West Africa. Combining satellite imagery, the perception of local people and botanical information, this study investigated the vegetation dynamics and the drivers of vegetation changes in Fatick Province, Senegal. Satellite images showed a change in vegetation composition, i.e., a loss of tree cover and an increase in shrub cover, herbaceous cover and tans (highly saline areas with sparse vegetation). Although the trend was the same, the three villages had different vegetation histories. A survey of the woody vegetation showed that shrubs and young trees were dominating with relatively few large trees. Local people perceived a general decline of woody plants from 1993 to 2013. Among 60 species mentioned by local people, 90 % were declining and 10 % increasing. Together the three methods documented a decrease in density and diversity of the woody vegetation, mainly influenced by salinity and land use. The large numbers of young trees indicate a potential for regeneration of some, but not all, tree species. As many tree species appreciated by local people were reported to be declining, local communities have experienced a reduction of their natural resources. Based on villagers’ recommendations for improved vegetation management, we discuss possible contributions including reforestation, desalinization and environmental protection for restoration of the vegetation.     

Taxonomy, phenology, and trophics of the urban macrolepidoptera feeding on trees and shrubs

A total of 107 macrolepidopteran species from 12 families have been recorded in 2006–2010 on trees and shrubs in the city of Yekaterinburg; in contrast to natural communities, no lasiocampids and few nymphalids have been found. The proportion of specialized species among the Macrolepidoptera living in the city is decreased, although the proportion of obligate dendrophagous species is increased. Differences in the phenology of lepidopterans living in urban greenery from those living in natural communities have been observed: a decreased proportion of autumn-spring species and an increased proportion of summer species. These differences can be explained both by relatively weak colonization of urban territory by facultative dendrophagous species with their specific seasonal strategies and by differences in methods used to collect the insects.     

Modelling the trade-off between fire and grazing in a tropical savanna landscape, northern Australia.

As savannas are widespread across northern Australia and provide northern rangelands, the sustainable use of this landscape is crucial. Both fire and grazing are known to influence the tree-grass character of tropical savannas. Frequent fires open up the tree layer and change the ground layer from perennials to that dominated by annuals. Annual species in turn produce copious quantities of highly flammable fuel that perpetuates frequent, hot fires. Grazing reduces fuel loads because livestock consumes fuel-forage. This trade-off between fire and grazing was modelled using a spatially explicit, process-orientated model (SAVANNA) and field data from fire experiments performed in the Victoria River District of northern Australia. Results of simulating fire (over 40 years) with minimal or no grazing pressure revealed a reduction in the shrub and woody plants, a reduction in grasses, and no influence on the tree structure given mild fires. While mature trees were resistant to fire, immature trees, which are more likely associated with the shrub layer, were removed by fire. The overall tree density may be reduced with continual burning over longer time periods because of increasing susceptibility of old trees to fire and the lack of recruitment. Increases in stocking rates created additional forage demands until the majority of the fuel load was consumed, thus effectively suppressing fire and reverting to the grazing and suppressed fire scenario where trees and shrubs established.     

The phenomenon of forest invasion to steppe areas in the Middle Urals and its probable causes

Steppes at the northern limit of their distribution are a convenient object for studying climate-induced modifications of the environment, being sensitive to regional climate changes. Over the past 46–47 years, herbaceous vegetation in the study steppe areas has been replaced by shrubs and trees. Petrophytic steppes on hilltops and stony knolls, where conditions are not favorable for tree growth, has proved to be more resistant to such changes. In these habitats, however, the influence of surrounding forest phytocenoses has also resulted in a gradual decrease in the proportions of species from the steppe and forest–steppe floras in the structure of communities and the invasion by species typical of forest vegetation.     

沱江源森林群落生物多样性垂直格局研究

在野外样带调查的基础上，分析了沱江源头九顶山植被生物多样性随海拔而变化的规律，并简要分析了植被生物多样性垂直格局的影响因子。从河谷到林线，乔木占据群落上层，其郁闭度对林下灌草层群落发育影响很大，生物多样性体现出乔木层与灌草层的相互关系：乔木盖度大的群落其灌木和草本层稀疏，而盖度小的次生林和林线上的高海拔区域灌木和草本种类与个体都迅速增加。多样性指数Hill指数及N1、N2指数变化规律基本相似：林线以下乔木层多样性指数最高，灌木层次之，草本层多样性指数最小，尤其在中度海拔体现明显，海拔3 500 m以上，草本多样性指数最高，灌木次之，而乔木已退出竞争。     

Towards a general relationship between climate change and biodiversity: an example for plant species in Europe

Climate change is one of the main factors that will affect biodiversity in the future and may even cause species extinctions. We suggest a methodology to derive a general relationship between biodiversity change and global warming. In conjunction with other pressure relationships, our relationship can help to assess the combined effect of different pressures to overall biodiversity change and indicate areas that are most at risk. We use a combination of an integrated environmental model (IMAGE) and climate envelope models for European plant species for several climate change scenarios to estimate changes in mean stable area of species and species turnover. We show that if global temperature increases, then both species turnover will increase, and mean stable area of species will decrease in all biomes. The most dramatic changes will occur in Northern Europe, where more than 35% of the species composition in 2100 will be new for that region, and in Southern Europe, where up to 25% of the species now present will have disappeared under the climatic circumstances forecasted for 2100. In Mediterranean scrubland and natural grassland/steppe systems, arctic and tundra systems species turnover is high, indicating major changes in species composition in these ecosystems. The mean stable area of species decreases mostly in Mediterranean scrubland, grassland/steppe systems and warm mixed forests.     

On adaptations of trees and shrubs in the north of the Russian Far East

Specific ecological features of trees (Chosenia arbutifolia and Betula lanata) and shrubs (Pinus pumila and Duschekia fruticosa) at the northern limit of their distribution are compared. New biomorphological adaptations of these species under extreme conditions are described.     

Radionuclide transfer from soil to fruit

The available literature on the transfer of radionuclides from soil to fruit has been reviewed with the aim of identifying the main variables and processes affecting the behaviour of radionuclides in fruit plants. Where available, data for transfer of radionuclides from soil to other components of fruit plant have also been collected, to help in understanding the processes of translocation and storage in perennial plants. Soil-to-fruit transfer factors were derived from agricultural ecosystems, both from temperate and subtropical or tropical zones. Aggregated transfer factors have also been collected from natural or semi-natural ecosystems. The data concern numerous fruits and various radionuclides. Soil-to-fruit transfer is nuclide specific. The variability for a given radionuclide is first of all ascribable to the different properties of soils. Fruit plant species are very heterogeneous, varying from woody trees and shrubs to herbaceous plants. In temperate areas the soil-to-fruit transfer is higher in woody trees for caesium and in shrubs for strontium. Significant differences between the values obtained in temperate and subtropical and tropical regions do not necessarily imply that they are ascribable to climate. Transfer factors for caesium are higher in subtropical and tropical fruits, while those for strontium, as well as for plutonium and americium, in the same fruits, are lower; these results can be interpreted taking into account different soil characteristics.     

Synthesis of ecosystem vulnerability to climate change in the Netherlands shows the need to consider environmental fluctuations in adaptation measures

Climate change impacts on individual species are various and range from shifts in phenology and functional properties to changes in productivity and dispersal. The combination of impacts determines future biodiversity and species composition, but is difficult to evaluate with a single method. Instead, a comparison of mutually independent approaches provides information and confidence in patterns observed beyond what may be achieved in individual approaches. Here, we carried out such comparison to assess which ecosystem types in the Netherlands appear most vulnerable to climate change impacts, as arising from changes in hydrology, nutrient conditions and dispersal limitations. We thus combined meta-analyses of species range shifts with species distribution modelling and ecohydrological modelling with expert knowledge in two respective impact studies. Both impact studies showed that nutrient-poor ecosystems and ecosystem types with fluctuating water tables—like hay meadows, moist heathlands and moorlands—seem to be most at risk upon climate change. A subsequent meta-analysis of species–environmental stress relations indicated that particularly endangered species are adversely affected by the combination of drought and oxygen stress, caused by fluctuating moisture conditions. This implies that adaptation measures should not only aim to optimise mean environmental conditions but should also buffer environmental extremes. Major uncertainties in the assessment included the quantitative impacts of vegetation-hydrology feedbacks, vegetation adaptation and interactions between dispersal capacity and traits linked to environmental selection. Once such quantifications become feasible, adaptation measures may be tailor-made and optimised to conserve vulnerable ecosystem types.     

Industrial pollution reduces the effect of trees on forming the patterns of heavy metal concentration fields in forest litter

An analysis is made of the effect of large spruce and birch trees on the spatial pattern of the fields of heavy metal concentrations (Cu, Pb, Cd, Zn) and pH in the forest litter formed in tree stands exposed to long-term pollution with emissions from the copper smelter in Revda, Sverdlovsk oblast. The fields formed by trees growing in the background area have a regular spatial structure: the concentrations of elements decrease with increase in the distance from the tree trunk to the edge of canopy gap, with the position of sampling point relative to the trunk accounting for more than half of total variance. In polluted areas, the regular component of the field structure is very weakly expressed, and the main role is played by higher-order heterogeneity related to the mosaic pollution pattern on the scale of tens to hundreds of meters.