近40年来冷龙岭地区冰川退缩和气候变化的关系

运用比值阈值法(TM3/TM5)结合目视解译,从1973年、1999年和2010年3个时段的MSS、ETM、TM影像中提取了祁连山东段冷龙岭地区冰川的边界,并对距其较近的门源、乌鞘岭、武威和永昌4个气象站点1961—2010年的气象数据以及冰川区的气象数据进行了分析,结果表明:(1)37a来,冰川处在持续退缩状态;近10a来,冰川消融速度加快;南坡退缩较快,北坡退缩较慢,其它坡向介于二者之间;(2)该区增温趋势较明显;该区的降水虽有少量增加,但趋势却很不明显;(3)37a来,冰川退缩的主要原因是气温的升高;近10a来,冰川加速消融反映了20世纪90年代末以来的气温变化特征;南坡冰川对气候变化的反应较敏感。     

Large-scale estimators of threatened freshwater catchment species relative to practical conservation management

Freshwater ecosystems are among the most threatened in the world. In light of the threats to freshwater biodiversity, it is essential to map the distribution and status of species to ascertain their threat status for prioritizing conservation action. However, while there is agreement that the conservation of freshwater ecosystems depends on whole-catchment management, there are still a wide variety of large-scale mapping methods in use, the advantages and disadvantages of which have not been fully explored. This study shows that area estimation based on minimum convex polygons should not be encouraged for aquatic species. The IUCN definition of area of occupancy (AOO) is a useful term, albeit highly scale-dependent, for assessment of the total approximate area over which a species occurs. However, for aquatic fauna, and perhaps many other organisms, assessment of occurrence should be based on the more accurate point-locality presences only. The IUCN extent of occurrence (EOO), for freshwater catchment species, should be redefined as ‘the sum of the smallest hydrological units identified, of presently known, inferred or projected occurrences of a taxon, excluding cases of vagrancy, that are used to estimate the threat to a taxon’. A single hydrological unit is also the conservation or management unit. Here we suggest that this unit is the quaternary catchment. This new mapping approach is more appropriate and practical for use in both management planning and conservation action. We suggest that conservation managers and decision makers facilitate co-operation in freshwater mapping efforts by working at the same spatial scale, i.e. the same hydrological unit.     

Assisted migration of plants: Changes in latitudes, changes in attitudes

Rapid climate change has the potential to alter the location of bioclimatic envelopes for a significant portion of the world’s flora. Plant species will respond variously via phenotypic plasticity, evolutionary adaptation, migration, or extinction. When fragmentation limits migration potential of many species or when natural migration rates are outstripped by the pace of climate change, some propose purposeful, human-mediated migration (assisted migration) as a solution. Here, we join the debate on assisted migration, and while recognizing the potential negative impacts, present a strategy to collect and bank seeds of plant species at risk of extinction in the face of rapid climate change to ensure that emerging habitats are as species-diverse as possible. We outline the framework currently being used by the Dixon National Tallgrass Prairie Seed Bank to prioritize species for seed banking, both for restoration purposes and for potential assisted migration in the future. We propose a strategy for collecting across the entirety of a species range, while targeting populations likely to go extinct under climate change, determined by application of species distribution models. Finally, we discuss current international efforts to collect and bank the global flora, as well as the research needs necessary to fully undertake the strategy presented.     

The potential for interspecific competition among African carnivores

The general importance of interspecific competition as an ecological factor for carnivores is unknown and its conservation significance may have been inflated by intensive research conducted on a few vulnerable species. We therefore examined the potential for interspecific competition across carnivores on one continent, Africa, by calculating, for each of 70 carnivore species, the number of other carnivore species that overlapped it in geographic range, habitat, and diet, and that could potentially kill the species in question. The average carnivore in Africa shares some of its geographic range and habitat with 26 other species suggesting competition could be pervasive. More specifically, carnivores may have to share food resources with 22 other carnivore species, on average, although the potential for food stealing is far lower. The average African carnivore may be vulnerable to predation by 15 other species although it is unlikely to be eaten by other carnivores. These analyses indicate that exploitative competition and interspecific killing are of potential widespread importance for a large number of carnivores in Africa, rather than being restricted to a few selected carnivores highlighted in the current literature.     

美国草原本科教育的现状与特征

本研究基于美国草原管理学会（Society for Range Management,SRM）及美国高校网站,对美国草原本科专业开设状况、专业主页简介、人才培养方案等信息进行检索与分析,得到美国草原本科教育的现状与特征。结果表明：美国目前共有21所大学开办草原本科专业,另有17所大学开设草原学课程,其布局特征基本与美国草原地理分布相吻合;各高校的草原专业培养方案根据定位与特色具有较大差异,呈现多样性特点;草原专业的设立凸显了美国对草原资源重要性的认知,本科毕业生也普遍具有较好的就业渠道与职业发展前景。总体而言,美国草原本科的概念和内涵要远远小于我国的“草业科学”,更聚焦于对草原资源管理方向的人才培养,不涉及草坪学与饲草学。     

Reduced tree health and seedling production in fragmented Fagus sylvatica forest patches in the Montseny Mountains (NE Spain)

Habitat fragmentation results in smaller and more isolated populations that may be at higher risk of extirpation or further decline in comparison with their more continuously distributed progenitors. Risks to fragmented populations have frequently been considered from the perspective of population genetics, however, disruption of normal plant demography may be an equal or greater threat to population persistence. We compared demographic performance and tree health in continuous and fragmented forest plots with similar tree size structure and local climatic and physiographic conditions in order to determine if fragments are characterized by poor health and reproduction. We found that beech forest fragments showed lower seedling density, more tree crown damage and also higher percentage of dead trees. However, mortality of juveniles in the youngest age class was substantially lower in fragments such that long-term population structure remained similar between the two forest types. If reduced mortality compensates for reduced seedling establishment, as our data suggest, then fragmented populations should show greater long-term persistence than would be predicted based on comparison of young age cohorts alone. However, despite such demographic compensation, the decreased health of adult trees may pose an increasing future threat to the fragmented populations. Our results demonstrate the importance of integrating demographic patterns over long time periods and not relying on single year or cohort comparisons and may partly explain population genetic differences previously reported for the same populations.     

石羊河流域年径流序列的变异诊断

采用重新标度极差分析法(R/S分析方法),对石羊河流域8条河流的年径流序列进行了变异诊断,计算了变异前后序列均值和年径流随时间的变化关系。结果表明,石羊河流域8条河流的年径流序列已发生了变异,变异年份分别为:杂木河1989年,西营河1989年,金塔河1973年,黄羊河1982年,古浪河1984年,大靖河1959年,东大河1967年,西大河1960年。经回归分析表明,对这些变异年份的诊断是合理的。     

混合正交试验优化微波消解测定沉积物中重金属Pb

[目的]探讨土壤中重金属Pb消解的影响因素。[方法]利用二维平面吸光度等值线变化探讨区域范围内吸光度趋势变化,绘制Pb吸光度分布图,用Minitab 16软件对试验结果进行极差分析和方差分析。[结果]影响Pb消解因素主次排序为HF、HNO_3、HClO_4、燃气流量、HCl、助燃气流量、灯电流和燃烧器高度。优化试验表明,在土壤样品中加入9 mL HNO_3、5 mL HF、3 mL HClO_4经微波消解后,原子吸收分光光度计工作条件如下:Pb波长为217.0 nm,狭缝宽度为1.3 nm,燃烧器高度为4 nm,助燃气流量为2.4 L/min,灯电流为4.0 mA,燃气流量为4.0 L/min。在上述条件下,最优吸光度为0.302。[结论]研究结果可为精确测定土壤中各种重金属吸光度提供理论依据。     

我国北方农牧交错带的草地植被类型、特征及其生态问题

我国北方农牧交错带地处湿润气候与干旱气候、农业区与牧业区的过渡地带,草地植被类型和生态景观极具特殊性。其总面积65.46万km2,其中天然草地面积3165.1万hm2,占土地总面积的48.35%。其天然草地植被主要包括疏林草地、灌丛草地和草本植被草地三大类,面积分别为100.29万hm2、721.11万hm2和2343.7万hm2,各占该区天然草地植被总面积的3.17%、22.78%和74.05%。由于长期受到人为强烈干扰,植被退化、沙化严重,生产力急剧下降,成为我国北方生态问题最严重的地区之一。其草地植被的恢复重建应重点注意植被类型的选择、合理的种植密度与适宜的封育期限和放牧利用强度,同时加强对传统畜牧业的改造,大力发展季节畜牧业和减轻草地放牧压力,消除草地退化沙化的根源。     

Scaling patterns of biomass and soil properties: an empirical analysis

We argue that studies at multiple scales must necessarilychange the extent of measurements, not just the spacing, in order toeffectivelycapture information regarding processes at multiple scales. We have implementeda multi-scale sampling scheme using transects of 10 cm, 1m, 10 m, 100 m, and 1 km ateach of four sites along an elevational gradient from dry foothills forest toalpine tundra in the Front Range of Colorado; these four sites form anadditional transect of 22 km. Along each of these transects wetookten equally spaced soil cores and measured variables important in determiningboth microbial and plant community structure: soil water content, organicmattercontent, pH, and total soil biomass. With this sampling scheme we are able totreat scale as an independent variable in our analyses, and our data show thatboth particular sites and particular variables can determine whether estimatesof mean values are scale-dependent or not. A geostatistical analysis using allof our data shows common relationships between scales across ecologicallydiverse sites; biomass shows the most complex pattern of distribution acrossscales, as measured by fractal dimension. Our analyses also reveal theinadequacy of several standard geostatistical models when applied to data frommultiple scales of measurement – we recommend the use of the boundedpowerlaw model in such cases. We hypothesize that because biological communitiesmustrespond simultaneously to multiple variables with differing patterns of spatialvariation, the spatial variation of biological communities will be at least ascomplex as the most complex environmental variable at any given site.This revised version was published online in May 2005 with corrections to the Cover Date.