柴达木盆地尕斯库勒盐湖区盐生植物吸盐效应及其耐盐性评价<sub><sup> </sup></sub>

本项研究选取柴达木盆地尕斯库勒盐湖区作为研究区,筛选出了9种优势盐生植物,开展了盐生植物生长区土体颗粒、容重、含水量等物理性质指标,以及土体中HCO<sub>3</sub><sub><sup>-</sup></sub>、Cl<sub><sup>-</sup></sub>、SO<sub>4</sub><sub><sup>2-</sup></sub>、K<sub><sup>+</sup></sub>、Na<sub><sup>+</sup></sub>、Ca<sub><sup>2+</sup></sub>和Mg<sub><sup>2+ </sup></sub>7种易溶盐离子含量试验测试,分析了区内芦苇、海韭菜等9种盐生植物茎叶和根系部分HCO<sub>3</sub><sub><sup>-</sup></sub>、Cl<sub><sup>-</sup></sub>等7种易溶盐离子含量及其分布规律。在此基础上,探讨了区内9种盐生植物对易溶盐离子吸收作用及其差异性;采用盐生植物地上茎叶部分K<sub><sup>+</sup></sub>/Na<sub><sup>+</sup></sub>值结果,定量评价了区内9种盐生植物耐盐性及变化规律,结果表明,区内9种盐生植物茎叶部分K<sub><sup>+</sup></sub>/Na<sub><sup>+</sup></sub>比值,其由大至小依次为：小花棘豆0.84、羊齿天门冬0.58、白刺0.55、盐地风毛菊0.52、海韭菜0.50、无脉苔草0.47、洽草0.41、芦苇0.39和赖草0.34。本项研究结果,利用为尕斯库勒湖区及其周边地区,利用盐生植物有效改良土壤盐渍化方面提供理论支撑。     

基于生态位理论的东北三省政府干预强度与市场化水平格局演变研究

以“政府干预强度”和“市场化水平”为研究对象,通过对其生态系统的剖析,构建相应的评价指标体系及其生态位模型,并选取东北三省地级市为评价对象,对其“强政府弱市场”格局和演变趋势进行分析。定量分析的主要结论为：东北三省普遍存在“强政府弱市场”现状,其中黑龙江省最为突出,其次为吉林省、辽宁省;东北三省“强政府弱市场”格局出现多次波动,仅2003~2005年降幅较高,说明2003年“东北振兴战略”影响效果的持续性较短;东北各地市“强政府弱市场”格局具有明显的区域溢出效应,格局较明显的区域主要集中在离中心城市或沿海口岸较远的黑龙江省北部以及辽宁省、吉林省的部分内陆城市。     

科尔沁沙质放牧草地植物多样性及生态位的分异规律研究

研究结果表明:①不同放牧强度下群落演替方向和速度有很大差异,其中过牧使植被种类组成趋于简单,植物多样性指数下降,草地中以一年生劣质牧草占绝对优势,轻牧和禁牧则相反;②由于群落的物种组成和植物种群数量的变化,使群落占据的物种生态位也明显分异,其中轻牧和禁牧的生态位宽度指数趋于增大,过牧趋于下降,中牧年际波动大。由于生态位分离明显,使生态位相似性降低,生态位重叠部分很小;③随着植被的分异,在属性空间上其位置发生飘移,变异越大,飘移的愈分散,其中轻牧和禁牧下植被在属性空间的位置呈曲线型分布,说明其演替呈有规律的渐变过程,而重牧下植被分异剧烈,各点在空间分布零散且距离远,说明其演替跃变性强。     

基于小生境遗传算法软土地基上加筋路堤稳定性分析

在软土地基加筋路堤稳定性分析方法中,传统分析方法(如瑞典法和荷兰法)因对加筋材料的加筋作用估计不足,导致计算结果过于保守,与实际不符。本文在充分考虑加筋体的加筋作用下,提出了新的加筋路堤稳定性分析计算方法,并采用小生境遗传算法搜索临界滑动面和最小安全系数。算例计算结果表明,本文提出的加筋路堤稳定性分析方法与工程实际情况吻合较好,并且小生境遗传算法能有效地搜索到边坡所有的临界滑动面。     

小生境遗传算法求解多峰问题在反演中应用

基于反演问题的不确定性和目标函数的多峰性，引入改进的小生境遗传算法，求解出目标函数的若干个局部峰（或全局峰），然后利用先验知识，判定得到满意解，并利用褶积模型进行层速度反演，通过理论速度与反演速度的比较，验证了进行多峰优化的有效性。     

Differential recruitment of introduced Pacific oysters and native mussels at the North Sea coast: coexistence possible?

Pacific oysters (Crassostrea gigas Thunberg 1793) have been introduced into the Wadden Sea (North Sea), where they settle on native mussel beds (Mytilus edulis L.), which represent the only extensive insular hard substrata in this soft-sediment environment. As abundances of C. gigas rose, some mussel beds became increasingly overgrown with oysters, whereas others did not. Field experiments revealed that recruitment of C. gigas was higher in the lower intertidal than in the upper subtidal zone, that it was higher on conspecifics than on mussels, and that it was not affected by barnacle epigrowth except when settling on mussels. Mussel recruitment is known from inter- and subtidal zones. It occurred equally on oyster and mussel shells but showed a clear preference for barnacle epigrowth over clean shells. Assuming that settlement and recruitment are key processes for species abundances on the North Sea coast, it is predicted that the positive feedback in oyster settlement will lead to rapid reef formation of this invader at the expense of mussel beds. Mussels, however, may escape competitive exclusion by settling between or on the larger oysters especially when barnacles are abundant. Experimental patches with mussels were more often covered by fucoid algae (Fucus vesiculosus forma mytili Nienburg) than patches with oysters, and oyster recruitment was poor underneath such algal canopies. Thus, fucoids may provide the native mussels with a refuge from the invading oysters and the two bivalves may coexist, provided food is not limiting.     

Visualizing Patterns of Genetic Landscapes and Species Distribution of Taxus wallichiana (Taxaceae), Based on GIS and Ecological Niche Models

The Chinese yew (Taxus wallichiana), which is widely distributed in the Himalayas and in southern China, is now on the edge of extinction. In order to understand the evolutionary processes that control the current diversity within this species at the genetic and ecological levels, its genetic patterns and range dynamics must first be identified and mapped. This knowledge can then be applied in the development of an effective conservation strategy. Based on molecular data obtained from 48 populations of T. wallichiana, we used GIS-based interpolation approach for the explicit visualization of patterns of genetic divergence and diversity, and a number of potential evolutionary hotspots have been specifically identified within the genetic landscape maps. Within the maps of genetic divergence and diversity, five areas of high inter-population genetic divergence and six areas of high intra-population genetic diversity have been highlighted in a number of separate mountain regions, and these evolutionary hotspots should have the priority to be protected. Furthermore, four geographical barriers have been identified: the eastern Himalayas, the Yunnan Plateau, the Hengduan Mountains and the Taiwan Strait. According to ecological niche modeling (ENM), the populations of T. wallichiana within the Sino-Himalayan Forest floristic subkingdom experienced westward expansion from the periods of Last Inter-glacial to Last Glacial Maximum (LGM). Following the LGM, the distribution range overall became reduced and fragmented. These findings challenge the classic mode of contraction-expansion in response to the last glaciation. In conclusion, our findings suggest that the changes in geographical landscapes and climate that occurred during the Quaternary resulted in current genetic landscape patterns.     

Sensitivity to climate change for two reptiles at the Mojave-Sonoran Desert interface

The high temperatures and extended droughts that characterize habitat for desert-living reptiles may already approach their physiological tolerances and so could put them at risk due to climate change. Here I examined climate change sensitivity for desert tortoises, Gopherus agassizii, and common chuckwallas, Sauromalus ater, two large-bodied reptiles that occur across the Mojave-Sonoran Desert interface. I employed the Mahalanobis D² statistic to model their niche spaces and then assessed climate-change sensitivity by altering climate variables along a gradient of increasing temperature and decreasing precipitation. While shifting climate variables, I held terrain and soils variables that otherwise define these species’ preferred habitat constant, providing a more realistic prediction of available niche space. Both reptiles’ modeled niches responded to climate change by shifting to higher elevations and increasingly away from their Sonoran Desert distribution. At moderate predictions of climate change (+2 °C, −50 mm precipitation) desert tortoises’ suitable habitat was reduced by nearly 88% in the Sonoran Desert portions my study area, and nearly 66% in the Mojave Desert regions. Under the same scenario chuckwallas lost nearly 92%, but increased 120% respectively. Within the context of climate change potential increases in drought frequency appear to present the greater challenge for these species.     

Using very high resolution remote sensing for the management of coral reef fisheries: Review and perspectives

Coral reef fisheries are critical for food security and as a source of income in developing and developed countries, but they are collapsing in many areas. Following the emergence and routine availability of commercial very high spatial resolution (0.6-10 m) multispectral satellite images, we reviewed the use of these new high-quality remote sensing data and products for coral reef fisheries management. The availability of habitats maps improves management by guiding sampling strategies, mapping resources, involving local communities, identifying conservation areas, and facilitating Ecosystem Based Fishery Management (EBFM) approaches. However, despite their potential, very little use of products designed specifically for fishery management can be reported, likely due to high costs, inherent technology limitations and lack of awareness on the possibilities. Given the theoretical benefits brought by relevant habitat maps in EBFM frameworks, we advocate the use of adequate remote sensing products that integrate fishery technical services demands and local requirements.     

Dietary niche partitioning in a piscivorous fish guild in response to stocking of an additional competitor - The role of diet specialisation

Species belonging to the same ecological guild can coexist only if there are differences in their responses to limiting resources. Thus, competitor introductions may modify the niches of the resident competitors, but empirical studies are rare. The extent of niche modification might further depend on the species’ trophic specialisation along the specialists-to-generalists axis. In this study, we performed a semi-natural experiment by introducing a trophically specialised piscivorous fish (pikeperch) to the resident predator guild of a trophic generalist (perch) and a trophic specialist (pike) in a temperate freshwater lake. Individual diet data were used to calculate total niche hypervolume and inter- and intraspecific dietary niche overlap to evaluate strength of competitive interactions before and after pikeperch introduction. In both pike and perch, there was a moderate niche compression in response to pikeperch stocking. Furthermore, whereas perch diet hypervolume did not overlap at all with that of pikeperch, the intersection of niche space between the two trophic specialists was highly asymmetrical in favour of pike due to its less specialised diet composition in comparison with pikeperch. The intraspecific dietary niche overlap between perch size classes reflected an enhanced partitioning, whereas that of pike size classes was found almost unchanged in response to pikeperch stocking. These empirical results corroborate that competitive interactions and the degree of specialisation may strongly shape the success of introductions of top-predators in freshwater ecosystems. The most specialised species may persist only if the competitors belong rather to the generalists along the specialisation continuum.