河岸带研究及其退化生态系统的恢复与重建

河岸带是指水陆交界处的两边,直至河水影响消失为止的地带。河岸带是湿地的重要组成部分,在流域生态系统中发挥着重要的作用,具有较大的生态、社会、经济和旅游价值。河岸带研究以生态学、水文学和地貌学炎基础,涉及多种学科和技术方法。由于自然和人为因素的影响,退化河岸带的生态恢复与重建较为复杂,通过安徽潜山县潜水退化河岸带滩地近6a的生态恢复与重建试验,研究结果表明：恢复与重建后的河岸带滩地生态系统的生物多样性和稳定性增加;土训结构和养分条件得到改善,其中,小于0.002mm的粘粒含量的平均值由恢复前的4.53％,上升到恢复后的11.71％,土壤容重由恢复前的1.455g/cm^2下降到恢复后的1.2g/cm^2,土壤有机质的平均值由恢复前的1.25g/kg上升到恢复后的9.44g/kg;河滩地泥沙淤积量增加;植物抗风浪作用增强,有效地保护了河岸,改善了河岸带地区的小气候。河岸带研究在我国起步较晚,因此,今后应加强河岸带的管理和对退化河岸带生态系统的恢复与重建工作,使河岸带生态系统可持续地为人类提供丰富多样的生产、生活和观光旅游产品。     

Reduction of riparian arthropod abundance and diversity as a consequence of giant reed (Arundo donax) invasion

The non-indigenous perennial grass, Arundo donax, is an aggressive invader of riparian areas throughout California and many sub-tropical regions of the world, and is hypothesized to provide poorer quality habitat for native wildlife in riparian systems. We sampled aerial and ground-dwelling insects and other terrestrial arthropods associated with Arundo, native willow vegetation (Salix spp.), and mixtures of the two vegetation types during two seasons to determine how Arundo influences invertebrate composition in a low gradient stream in central California. The total number of organisms, total biomass and taxonomic richness of aerial invertebrates associated with native vegetation was approximately twice that associated with Arundo vegetation, while mixed vegetation supported intermediate arthropod levels. Shannon-Weaver (Weiner) diversity associated with native vegetation stands was also higher than that of Arundo vegetation. Ground-dwelling assemblages did not show differences as great as aerial assemblages which are more critical to foraging avian species. These results indicate that vegetation type is a significant factor reducing the abundance and diversity of invertebrates in this, and presumably in many other riparian ecosystems where this invasive species has become a dominant component. Arundo invasion changes the vegetation structure of riparian zones and in turn, may increasingly jeopardize its habitat value for birds and other wildlife whose diets are largely composed of insects found in native riparian vegetation.     

Substrate Availability May Be More Important than Aquatic Insect Abundance in the Distribution of Riparian Orb-web Spiders in the Tropics

Spiders that are abundant along streams may depend on energy subsidies across land–water ecotones, but the effects of season and habitat structure on this trophic linkage remain poorly understood in the tropics. We carried out surveys and a manipulative experiment to investigate the effects of season and substrate availability on the distribution of riparian orb-web spiders in Hong Kong, southern China. In the surveys, spider abundance, prey, substrate use, and web orientation were recorded. The experiment involved installation of in-stream artificial substrates (ropes and bamboo poles) to increase substrate availability for web attachment. We found no seasonal difference in web abundance, but seasonal differences were observed for the prey on webs: aquatic insects (mostly Ephemeroptera and chironomid midges) contributed 69 percent of total prey collected during the wet season, but only 38 percent during the dry season. Most webs (50–80%) were < 0.5 m above the water and 45–51 percent of them tended to be orientated horizontally to the water surface and supported by overhanging vegetation and boulders. The addition of artificial substrates resulted in a 23–34 percent increase in the number of webs at the four treatment sites compared to controls, indicating that availability of web-building substrates is a critical determinant of the spider distribution. Our results suggest that riparian zones are potential 'hotspots' of food availability for spiders, and that the aquatic insect subsidy allows this habitat to support increased densities of spiders when the constraint of substrate availability is relaxed.     

文峪河上游河岸林群落类型及其生态适应性

以文峪河上游河岸林为研究对象,采用TWINSPAN法对研究地区河岸林进行群落分类,对各群落类型特征进行分析.在提出河岸林群落生态功能适应性指标的基础上,对研究地区河岸林群落进行生态功能适应性分组.通过研究,文峪河上游河岸林可划分为阔叶混交林、华北落叶松阔叶混交林、云杉落叶松混交林、云杉阔叶混交林、阔针混交林、油松阔叶混交林、青杨林、沙棘灌丛和柳树灌丛等9个群落类型,但群落类型之间的分异性总体表现不高,且表现出突出的多样性特征;群落乔木层和灌木层的物种组成复杂,草本层多为一些耐干扰种和耐水湿种,总体上越远离河岸,高地群落中的物种比例越高,表现出高地森林与河流之间生态过渡带的典型特点和河岸带生态环境的高度异质性;根据本文构建的群落的生态功能适应性指标,研究地区9个河岸林群落类型可以划分为强入侵性功能组、中等入侵性功能组、弱入侵性功能组和高逃避性功能组等4个生态适应性功能组,不同生态适应性功能组的群落中,乔木层和灌木层的主要物种具有明显不同的生态对策,而草本层物种的差异不明显.     

Stream ecosystem responses to the 2007 spring freeze in the southeastern United States: unexpected effects of climate change

Some expected changes in climate resulting from human greenhouse gas emissions are clear and well documented, but others may be harder to predict because they involve extreme weather events or heretofore unusual combinations of weather patterns. One recent example of unusual weather that may become more frequent with climate change occurred in early spring 2007 when a large Arctic air mass moved into the eastern United States following a very warm late winter. In this paper, we document effects of this freeze event on Walker Branch, a well‐studied stream ecosystem in eastern Tennessee. The 2007 spring freeze killed newly grown leaf tissues in the forest canopy, dramatically increasing the amount of light reaching the stream. Light levels at the stream surface were sustained at levels considerably above those normal for the late spring and summer months due to the incomplete recovery of canopy leaf area. Increased light levels caused a cascade of ecological effects in the stream beginning with considerably higher (two–three times) rates of gross primary production (GPP) during the late spring and summer months when normally low light levels severely limit stream GPP. Higher rates of stream GPP in turn resulted in higher rates of nitrate (NO₃^?) uptake by the autotrophic community and lower NO₃^? concentrations in stream water. Higher rates of stream GPP in summer also resulted in higher growth rates of a dominant herbivore, the snail Elimia clavaeformis. Typically, during summer months net NO₃^? uptake and snail growth rates are zero to negative; however, in 2007 uptake and growth were maintained at moderate levels. These results show how changes in forest vegetation phenology can have dramatic effects on stream productivity at multiple trophic levels and on nutrient cycling as a result of tight coupling of forest and stream ecosystems. Thus, climate change‐induced changes in canopy structure and phenology may lead to large effects on stream ecosystems in the future.     

西双版纳傣族村寨对湿地植物的传统利用

作者用半结构访谈与关键人物访谈相结合,并佐以证据标本采集的民族植物学研究方法,对云南省西双版纳3个自然环境和经济社会条件差异较大的典型傣族村寨(曼降,曼安,曼伞)居民的湿地植物知识,以及不同性别、年龄人群掌握湿地植物知识的差异作了统计分析。研究结果表明:(1)西双版纳傣族村寨利用的湿地植物种类丰富,经鉴定的有46科102种,以湿生植物为主;利用类型有食用类、药用、代茶类和宗教类等,以食用类为主。(2)三个村寨中以曼伞调查和采集到的植物种类最多,曼安次之,曼降最低。3个村寨利用的湿地植物种类的相似性低。这与村寨周围的自然植被类型及其干扰程度密切相关。(3)统计分析显示,村寨的自然环境与经济发展状况对该村村民传统湿地知识的掌握有重要的影响。食用和药用、代茶植物知识在3个村寨都表现为年长组(>45岁)明显高于年轻组(≤45岁,P<0.05),而男性和女性对不同知识的掌握则因村寨自然环境和经济发展状况的不同而各不相同。植物多样性和民族传统文化多样性的关系显示出传统知识的传承对植物多样性保护是十分重要的。     

青海湖流域具鳞水柏枝植物水分利用氢同位素示踪研究

具鳞水柏枝(Myricaria squamosa)是我国高寒地区广泛分布的优势河谷灌木, 具有维持河谷湿地系统稳定的功能。然而, 目前国内外有关具鳞水柏枝水分利用来源的定量研究很少。该文运用氢稳定同位素示踪方法, 分析了青海湖流域具鳞水柏枝茎(木质部)水和潜在水源(地下水、河水和土壤水)的氢稳定同位素比率(δD)的季节变化, 发现具鳞水柏枝在不同水文环境下的植物水分利用来源有明显差异。研究结果表明, 生长在河岸边的具鳞水柏枝在6、7月主要利用地下水与河水, 分别占其所利用水分的89%、86%和55%、65%, 8月主要利用0-20 cm土层的土壤水, 9月水源不详。生长在离河岸约100 m处的具鳞水柏枝在6月主要利用地下水与河水(91%、70%), 在7-9月以0-60 cm土层的土壤水为主要水源。这表明生长在河岸边的具鳞水柏枝对地下水和河水的依赖程度较高, 而距离河岸约100 m时对土壤水的利用量较多, 反映出生长在不同生境中的具鳞水柏枝对特定水分条件的特殊适应结果。     

山西文峪河上游河岸林群落稳定性评价

稳定性是植物群落结构与功能的综合特征。该文运用模糊综合评判理论评价了山西文峪河上游13种河岸林群落的稳定性。基于群落整体稳定性和结构稳定性的考虑, 选取乔木层优势树种更新潜力、物种多样性、Godron指数、立地质量和保护程度等5项特征指标, 通过计算各群落5项指标隶属度的平均值来评价群落稳定性。研究结果表明, 多数群落的稳定性隶属度介于0.40-0.60, 属于低山森林演替系列的青杨辽东栎(Populus cathayana + Quercus wutaishanica)混交林和油松白桦(Pinus tabulaeformis + Betula platyphylla)混交林的稳定性居中; 中高山森林演替系列中, 群落稳定性随着演替的进展而增加, 青杨(Populus cathayana)林结构简单, 稳定性最低, 青杄(Picea wilsonii)林接近演替顶极, 稳定性最高; 但并非只有近演替顶极的群落是稳定的, 客观存在的各种林冠干扰和河岸生境的高度异质性也使得白杄杨桦(Picea meyeri + Populus cathayana + Betula platyphylla)混交林、落叶松白杄(Larix principis-rupprechtii + Picea meyeri)混交林和落叶松青杄(Larix principis- rupprechtii + Picea wilsonii)混交林有较高的稳定性。