半干旱区湿地-干草原群落交错带边缘效应研究

以宁夏盐池四儿滩湿地为例,于2005年和2006年7~8月份沿湿地—干草原生境梯度按东、东北、西、西北4条样线进行实地植被调查,并采用TWINSPAN数量分类和植物群落结构指数计量研究湿地—干草原交错带边缘效应。结果表明:(1)四儿滩湿地生态系统植物群落分为沼泽植被、草甸植被、干草原植被3个类型。(2)四儿滩湿地植物群落结构指数除群落均匀度指数外,生态优势度、丰富度和物种多样性均是交错带最大,其次是旱生带,湿生带最小。(3)四儿滩湿地—干草原交错带不同方向群落结构差异较大,各项植物群落结构指数均是东北样线最大,西北样线最小。造成不同样线间边缘效应差异的主要因素是人为干扰程度和地形抬升程度不同。     

生态交错带宽度判定及其影响因子研究进展

生态交错带是相邻生态系统之间的过渡带,是生态系统结构和功能在时、空尺度上变化较快的区域,也是生物多样性丰富区、全球变化敏感区.生态交错带位置和宽度的判定是定量研究交错带生态过程的基础,对生物多样性保护、片断化森林生态系统的管理与恢复以及自然保护区的功能分区都具有重要意义.由于生态交错带本身的复杂性,在相当程度上依赖于尺度水平,并受到各种自然和人为因素的影响,以致于目前还缺乏公认的原理和方法定量研究生态交错带,对其位置、宽度判定和动态变化研究一直处于不断的探索中.在分析大量相关研究资料的基础上,文章对生态交错带宽度判定方法以及影响因子进行论述,并对生态交错带宽度判定的研究前景进行展望.     

生态交错带的定量判定

生态过渡性是梯度环境的特征之一,过渡带的显著性是地理学和地植物学中长期争论的重要问题,生态交错带位置和宽度的判定是定量研究交错带生态学过程的基础。样带法是采集非连续梯度数据和研究交错带的结构,功能和格局梯度变化的有效方法。生态交错带变化最为显著的特征是植被的变化,包括植物种类组成和植被结构的变化,植被生态学群落分析中的相异系数,β多样性,梯度分析和分类排序技术等已被证明是成熟可靠的方法。介绍两种交错带定量判定的有效方法。游动分割窗技术是通过滑动求取样带上样点间相异系数,通过相异系数变化曲线判定交错带的位置和宽度。分割窗技术提供了敏感地定位非连续梯度的客观且有效的方法,它不仅可用于环境梯度上的等距离样点取样,而且可用于非等距离梯度带多元变量的分析。植被的特征是对生态环境连续体的综合反应,植被在环境梯度上的排序参数提供了一种较好的交错带定量指标,样带植被数据特征参数的变异轮廓图能够反应植被沿样带的物种组成,结构和空间变化格局,可以反应植被沿环境梯度的β多样性和植物群落的梯度分化,植被变异侧面轮廓图的间断或不连续（突变）区间就是群落边界的位置。     

游动分割窗技术在生态交错带定量判定中的应用*-以四川巴郎山岷江冷杉林线为例

 以样带上样方间的距离系数为指标,采用游动分割窗技术辨析了岷江冷杉(Abies faxoniana)林线附近交错带的位置和宽度。结果表明,Bray-Curtis距离、相对欧氏距离、弦距离与平方欧氏距离的峰值和峰宽具有很好的重合性,上述距离系数均能作为判定林线交错带群落的边界和宽度的优良指标,其中,平方欧氏距离更能直观和准确地反映交错带植被的变异。样带上距离系数的峰值区和峰宽对生态交错带的位置和宽度有较为敏感的指示意义,游动分割窗技术是交错带判定和群落划分的有效方法。以样带上样方间的距离系数为指标,采用游动分割窗技术辨析了岷江冷杉(Abies faxoniana)林线附近交错带的位置和宽度。结果表明,Bray-Curtis距离、相对欧氏距离、弦距离与平方欧氏距离的峰值和峰宽具有很好的重合性,上述距离系数均能作为判定林线交错带群落的边界和宽度的优良指标,其中,平方欧氏距离更能直观和准确地反映交错带植被的变异。样带上距离系数的峰值区和峰宽对生态交错带的位置和宽度有较为敏感的指示意义,游动分割窗技术是交错带判定和群落划分的有效方法。     

水文情势与盐分变化对湿地植被的影响研究综述

湿地植被是湿地生态系统的重要组成部分。水文情势与盐分变化直接影响到湿地植被的分布与演替。目前,全球气候变化和人类活动导致的水文情势改变与盐分聚集已造成大面积的湿地退化和盐渍化,已严重威胁全球淡水湿地生态系统的稳定和健康。系统总结了水文情势与盐分变化单一环境变量及其交互作用对湿地植物生理生态、物种多样性、群落结构与演替和植被动态等诸多方面的影响研究进展,并探讨了湿地水文动态-盐分变化-植被响应的综合模型研究现状,认为发展湿地综合模型预测未来水文情势与盐分变化情景下湿地演变,是应对气候变化湿地水盐管理和生态保护的重要工具,最后指出今后亟需加强的研究方向。     

游动分割窗技术在生态交错带定量判定中的应用:以四川巴郎山岷江冷杉林线为例

以样带上样方间的距离系数为指标 ,采用游动分割窗技术辨析了岷江冷杉 (Abiesfaxoniana)林线附近交错带的位置和宽度。结果表明 ,Bray_Curtis距离、相对欧氏距离、弦距离与平方欧氏距离的峰值和峰宽具有很好的重合性 ,上述距离系数均能作为判定林线交错带群落的边界和宽度的优良指标 ,其中 ,平方欧氏距离更能直观和准确地反映交错带植被的变异。样带上距离系数的峰值区和峰宽对生态交错带的位置和宽度有较为敏感的指示意义 ,游动分割窗技术是交错带判定和群落划分的有效方法。     

黄土高原半干旱区云雾山封禁草原30年植被恢复对气候变化的响应

植被是区域气候与环境的综合反映,研究特定地区草地植被与气候变化的关系,寻找影响植被变化的关键因子,是植被重建和生态环境恢复的前提。利用1957-2008年的气候数据和1982-2008年的植被定位监测资料,分析了黄土高原半干旱区的宁夏云雾山植被动态变化规律及其与温度和降水的关系。结果表明:51a来,该区年平均温度明显升高,而年平均降水量总体呈减少趋势,显示黄土高原地区气候暖干化趋势明显。统计分析表明,研究区年平均温度对植被的重要值年际变化有极显著影响(P0.01),而年降水量与植被的重要值呈极显著正相关(P0.01),表明气候持续干旱化对该区植被的生长有较大影响,该区降水的多寡是直接影响植被生长优劣的决定性因子,改善区域水分状况和封禁是推进植被恢复与重建的主要措施。     

岷江上游花椒地/林地边界土壤水分影响域的定量判定

在岷江上游干旱河谷区,选取典型的花椒地/林地边界,利用TDR仪测定干旱条件下、雨后和每月0～15 cm土层水分含量,并用移动窗口法判定土壤水分的边界影响域.结果表明,若用移动窗口法对土壤水分的边界影响域进行判定,当窗口宽度为8～12时,边界影响域较易判定.年内土壤水分随时间变化而变化.这种变化可分为土壤水分上升期、高峰期和消退期3个时期.干旱条件下土壤水分的边界影响域较小,其宽度约从花椒地6 m到林地2 m;雨后土壤水分的边界影响域有较大增加,其宽度约从花椒地12 m到林地2 m;年内土壤水分的边界影响域宽度约从花椒地10 m到林地2 m之间变化.不同季节土壤水分的边界影响域不同,并随着季节的变化呈动态变化.从生态学意义上讲,岷江上游地区目前进行的将花椒地退耕成林地、栽植树苗的措施是不可取的,该区退耕还林的最好方法应该是退耕,使其灌木林或草本植物自然生长.     

基于土壤养分的农林生态系统生态交错带宽度测定

生态交错带变化最显著的是物种组成和植被结构, 然而植物群落与土壤养分是相互制约相互促进的两个系统。前期利用植物物种多样性变化趋势测定出退耕还林政策驱动下, 退耕撂荒地-云南松林(Pinus yunnanensis Franch)交错带宽度约9 m。假设利用土壤养分变化与前期利用植物物种多样性变化测定出的生态交错带宽度和类型一致。为验证此假设, 选取滇西北维西县永春乡退耕还林政策下形成的退耕撂荒地-云南松林交错带为研究对象, 测定其土壤养分变化趋势, 并利用移动窗口法进行交错带位置和宽度的测定。结果表明: (1)相对于云南松林, 退耕撂荒地土壤养分含量(有机质, 碱解氮, 速效钾, 速效磷)均显著偏低; (2)pH, 有机质, 碱解氮的变化趋势能更好的用于测定交错带的位置和宽度, 且SED指数优于PD指数; (3)最终测定农林生态交错带的宽度为11 m, 属于急变型交错带, 与前期利用植物多样性变化测定的结果一致。     

互花米草入侵影响下闽江河口湿地土壤有效硅的时空变化特征

2016年1—12月,选择闽江河口鳝鱼滩的短叶茳芏湿地、互花米草湿地以及二者的交错带湿地为研究对象,采用定位研究方法探讨了互花米草入侵影响下湿地土壤有效硅含量的时空变化特征。结果表明:互花米草入侵影响下3块湿地土壤有效硅含量随时间推移整体呈波动上升趋势;互花米草入侵显著提高了鳝鱼滩湿地30—60 cm土层土壤有效硅含量(P0.01),与短叶茳芏湿地相比,交错带湿地和互花米草湿地30—60 cm土层土壤有效硅含量分别增加了8.56%和19.97%,逐步线性回归分析表明土温和电导是影响其变化的重要因素(P0.01)。研究互花米草入侵影响下湿地土壤有效硅含量的变化特征,对于揭示湿地生态系统生源要素硅生物地球化学循环过程以及互花米草入侵及其扩张机制具有重要意义。     

华北农牧交错带农田-草地界面土壤水分影响域分析

在华北农牧交错区,选择线状边界的农田与草地典型区进行调查与土壤水分测定,采用移动窗口法,对农田-草地景观界面表层（0～20 cm）土壤水分影响域进行研究.结果表明：界面水分的影响域为草地6 m到农田4 m,总宽度10 m,属急变型界面;将农田-草地景观界面划分为3个功能区：农田功能区、草地功能区和农田-草地复合功能区.其中农田-草地复合功能区的土壤含水量变化剧烈,而草地功能区与农田功能区内土壤水分基本呈线性分布;草地生态系统土壤平均含水量比农田高约1 g·g^-1,这主要是由于草地开垦为农田后风蚀等作用而引起的土壤毛管持水力下降所致.作为植被覆盖不同的两个生态系统,不同的植物蒸腾和地表蒸发,可使不同功能区的土壤含水量产生明显差异,从而使土壤水势发生变化,使水分跨生态系统运移成为可能.     

Distribution and persistence of temporary wetland habitats in arid Australia in relation to climate

The distribution and area of temporary wetlands across the arid zone of Australia are highly variable. Any change in their distribution or extent due to climate change and/or extraction of water has the potential to adversely impact dependent biota. Satellite imagery was used to determine the spatial and temporal distribution of wetlands across arid Australia over an 11‐year period. Synoptic climate data were examined to identify the weather systems that caused wetland filling events. Simple threshold models relating rainfall to wetland filling for seven large regions of Australia were developed to examine patterns of wetland filling over the last 100 years. These data were used to examine the climatic processes that drive wetland filling and the likely impacts of climate change on wetland distribution. The strongest climatic influence on wetland filling in the arid zone was tropical weather systems. Their influence extended into southern regions and their effects were often widespread. Variation in wetland area in all regions of the arid zone was high. The Lake Eyre Basin experienced more large flood events than other regions and had the most large, persistent wetlands that remain unregulated by humans. Hindcasting of past filling events indicated that there was a general pattern of frequent wetland filling across inland Australia in the 1910s, 1950s and 1970s, and less frequent wetland filling in the late 1920s, 1930s and 1960s. Furthermore, there appeared to be no period greater than 12 months over the previous 95 years when there was no predicted wetland filling in the arid zone. Wetland ecosystems dependent on a few infrequent heavy rainfalls are clearly vulnerable to any change in frequency or magnitude of these events. Climate change that results in a drying or reduced frequency of large flood events, exacerbated by extraction of water for agriculture, could be catastrophic for some biota, particularly waterbirds, which use a mosaic of wetland habitat at broad spatial scales.     

干旱和半干旱地区灌木下土壤“肥岛”研究进展

世界许多干旱、半干旱地区草地生态系统逐渐被灌木生态系统取代,这种取代过程的发展是由灌木冠幅下土壤中“肥岛”的形成和灌木的扩散相互作用直接造成的,这种“肥岛”的形成和灌木的扩散之间的反馈作用能够改变该系统中的植被组成、结构和土壤养分分布格局,从而改变该生态系统的结构和功能,文中从“肥岛”的概念和形成机制出发,对“肥岛”现象形成的原因、“肥岛”现象的研究意义、研究方法、灌木扩散与“肥岛”之间的相互关系及生物对“肥岛”的响应进行了总结,并分析了“肥岛”研究中应注意的问题,希望为中国干旱、半干旱区域土地退化的成因和过程以及植被恢复的研究提供一些参考。     

若尔盖高原土地利用变化对生态系统服务价值的影响

运用GIS和遥感技术分析了若尔盖高原1990年、2000年和2005年的土地利用/覆盖特征, 在此基础上, 使用生态价值系数(C)计算出该区生态系统服务价值, 并使用敏感性指数(CS)对所选的C值进行验证. 结果表明, 该区域1990-2005年间生态系统服务价值从603.10?108元减少到586.07?108元, 共损失17.03?108元, 且损失量和损失幅度呈加速增加趋势; 该区域生态系统服务价值中, 废物处理价值最高, 水源涵养价值次之, 食物生产价值最低, 且各服务类型的价值均呈持续减小趋势; 若尔盖高原1990和2005年人均生态系统服务价值分别为38.93万元和27.03万元, 表明若尔盖高原由于人口增长和土地退化, 环境压力呈明显增大趋势. 湿地和草地退化是导致该区域生态系统服务价值减少的主要原因, 尤其是湿地退化. CS检验说明本文所选C值较为合理.     

Development of community metrics to evaluate recovery of Minnesota wetlands

Monitoring wetland recovery requires assessment tools that efficiently and reliably discern ecosystem changes in response to changes in land use. The biological indicator approach pioneered for rivers and streams that uses changes in species assemblages to interpret degradation levels may be a promising monitoring approach for wetlands. We explored how well metrics based on species assemblages related to land use patterns for eight kinds of wetlands in Minnesota. We evaluated land use on site and within 500 m,1000 m, 2500 m and 5000 m of riverine, littoral, and depressional wetlands (n = 116) in three ecoregions. Proportion of agriculture, urban, grassland, forest,and water were correlated with metrics developed from plant, bird, fish, invertebrate, and amphibian community data collected from field surveys. We found79 metrics that relate to land use, including five that may be useful for many wetlands: proportion of wetland birds, wetland bird richness, proportion of insectivorous birds, importance of Carex, importance of invasive perennials. Since very few metrics were significant for even one-half of the wetland types surveyed, our data suggest that monitoring recovery in wetlands with community indicators will likely require different metrics,depending on type and ecoregion. In addition, wetlands within extensively degraded ecoregions may be most problematic for indicator development because biotic degradation is historic and severe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Faunistic data and biogeography of terrestrial isopods from Tunisian wetlands

In Tunisia, while wetlands are considered as remarkable habitats for their faunal and floral diversity, few studies on the biogeography and the diversity of terrestrial isopods were performed. To fill this gap, we carried out a field study in the supralittoral zone of 146 Tunisian wetlands belonging to eight types (lagoon, river, lake, sebkha, dam, hill reservoir, beach and chott) and to five bioclimatic zones (humid, subhumid, semi‐arid, arid and Saharan). Field work was carried out in spring 2010. Terrestrial isopods were collected in the morning by hand search each time with the same sampling effort. During the study, 22 species of terrestrial isopods belonging to nine families were collected. Porcellio variabilis, Porcellio laevis, Chaetophiloscia elongata and Armadillidium pelagicum are the most common species identified. From the northern to the southern regions, a gradual decrease in species richness has been shown. The identified species belonged to different biogeographical categories: Mediterranean, Mediterranean‐Atlantic, North Africa with circum‐Sicilian islands, semi‐arid and Saharan species. Some of these species are endemic to Tunisia (Porcellio dominici) or to North Africa (Armadillidium sulcatum, Armadillidium tunisiense, Porcellio marginenotatus and P. variabilis). Terrestrial isopod species differ according to wetland type and bioclimatic zone.     

唐古拉山以北地区生态资产核算

生态系统核算可以为生态文明建设提供定量性的决策依据,包括生态资产核算和生态系统服务核算两个方面,生态资产指生产和提供生态系统产品和服务的生态系统。以唐古拉山以北地区(简称唐北地区)为研究对象对其生态资产进行了核算,建立生态资产实物量及变化核算表、损益表,提出了生态资产综合指数。2015年唐北地区草地生态资产面积为21800.01 km~2,其中良级比重最高达68.46%,湿地生态资产面积为4763.01 km~2,其中优级比例最高为59.72%,野生动植物共有138种,其中重点保护动物10种。2015年唐北地区生态资产综合指数为79.77,比2000年降低了3.60%。2000—2015年,湿地、草地生态资产分别增加了164.23、2.82 km~2。2000—2015年湿地生态资产存量增加202.90 km~2,其中由湿地恢复导致面积增加最大为200.50 km~2,存量减少38.63 km~2,其中湿地退化是导致存量减少的主要原因,面积为36.23 km~2,草地存量增加了39.18 km~2,主要是由于湿地退化导致的草地扩张,存量减少36.26 km~2,主要由湿地恢复和荒漠化引起。研究中不同生态资产质量等级的核算以及生态资产综合指数的提出利于生态资产的全面核算和比较,对于建立离任责任制、生态文明建设意义重大。     

Land‐use and isolation interact to affect wetland plant assemblages

Different management regimes imposed on similar habitat types provide opportunities to investigate mechanisms driving community assembly and changes in species composition. We investigated the effect of pasture management on vegetation composition in wetlands with varying spatial isolation on a Florida cattle ranch. We hypothesized that increased pasture management intensity would dampen the expected negative effect of wetland isolation on native species richness due to a change from dispersal‐driven community assembly to niche‐driven assembly by accentuated environmental tolerance. We used native plant richness, exotic plant richness and mean coefficient of conservatism (CC) to assess wetland plant assemblage composition. Sixty wetlands were sampled, stratified by three levels of isolation across two pasture management intensities; semi‐native (less intensely managed; mostly native grasses, never fertilized) and agronomically improved (intensely managed, planted with exotic grasses, and fertilized). Improved pasture wetlands had lower native richness and CC scores, and greater total soil phosphorus and exotic species coverage compared to semi‐native pasture wetlands. Increased wetland isolation was significantly associated with decreases in native species richness in semi‐native pasture wetlands but not in improved pasture wetlands. Additionally, the species–area relationship was stronger in wetlands in improved pastures than semi‐native pastures. Our results indicate that a) native species switch from dispersal‐based community assembly in semi‐native pastures to a species‐sorting process in improved pastures, and b) recently‐introduced exotic species already sorted for more intensive management conditions are primarily undergoing dispersal‐based community assembly. That land‐use may alter the relative importance of assembly processes and that different processes drive native and exotic richness has implications for both ecosystem management and restoration planning.     

Elevated CO2 does not stimulate carbon sink in a semi‐arid grassland

Elevated CO₂ is widely accepted to enhance terrestrial carbon sink, especially in arid and semi‐arid regions. However, great uncertainties exist for the CO₂ fertilisation effects, particularly when its interactions with other global change factors are considered. A four‐factor (CO₂, temperature, precipitation and nitrogen) experiment revealed that elevated CO₂ did not affect either gross ecosystem productivity or ecosystem respiration, and consequently resulted in no changes of net ecosystem productivity in a semi‐arid grassland despite whether temperature, precipitation and nitrogen were elevated or not. The observations could be primarily attributable to the offset of ecosystem carbon uptake by enhanced soil carbon release under CO₂ enrichment. Our findings indicate that arid and semi‐arid ecosystems may not be sensitive to CO₂ enrichment as previously expected and highlight the urgent need to incorporate this mechanism into most IPCC carbon‐cycle models for convincing projection of terrestrial carbon sink and its feedback to climate change.