中国东北样带（NECT）：十年集成与未来挑战

作为“国际地圈-生物圈计划(IGBP)”的15条陆地样带之一,中国东北样带(Northeast China Transect,NECT)在IGBP核心项目“全球变化与陆地生态系统(GCTE)”中已经建立10年之久。该样带位于中纬度温带半干旱地区,跨越北纬42~46,东经110~132,其主要全球变化驱动因素为降水,次要驱动因素为土地利用强度。在过去的10年里,中国东北样带的研究进展表现在以下几个方面:生态数据库发展、气候及其变异性、植物对环境的生态生理响应、植被和景观变化、生物多样性格局及其变化、植物功能型和植物性状及气候梯度分析、生产力和碳动态、花粉-植被相互关系、痕量气体放散、土地利用和土地覆盖变化以及生物地理和生物地球化学模拟。为达到更高水平的集成研究,中国东北样带今后需要:统一框架下的坚实的基础数据集、进一步的野外实验和观测、从斑块、景观到生物群区尺度的植被结构、过程和功能的集成模拟、样带内和与其他IGBP样带研究结果的相互比较、多学科交叉研究、国内和国际协作以及完整的科学计划和实施对策。     

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。     

从生态地理特征论中国东北样带(NECT)在全球变化研究中的科学意义

中国东北样带(NECT)是国际地圈生物圈计划(IGBP)全球变化研究的陆地样带之一。该样带在东经112°与130°30′之间沿北纬43°30′设置,长约1600km,跨越北纬42°～46°,宽约300km,位于中纬度温带地区以降水或湿润度/干燥度为主要全球变化驱动因素,自东至西沿一个连续的空间过渡梯度,植被类型或生物群区是由温带针阔叶混交林、温带落叶阔叶林、农田及温带草原的3个亚地带:草甸草原、典型草原和荒漠草原等类型组成。给出了样带的基本生态地理特征及其梯度分析,包括其地理位置、地形地貌、气候梯度、土壤类型、土地利用格局、植被类型、主要优势种和群落类型的生态地理特征以及全新世适宜期的植被分布格局。这些特征沿经向均表现出明显的梯度分布。     

鄂尔多斯高原生态过渡带的判定及生物群区特征

 本文用Holdridge生命地带方法对鄂尔多斯高原的生物群区进行了分类研究,研制了用于生态过渡带判定的计算机模型,模拟结果与实际情况基本吻合。鄂尔多斯高原的生物群区可分为草原、荒漠灌丛和荒漠3大类,草原群区以本氏针茅(Stipa bungeana)群落为主,荒漠灌丛群区以冷蒿(Artemisia frigida),狭叶锦鸡儿(Caragana stenophylla)群落为主,荒漠群区以红砂(Reaumuria soongorica)群落为主。鄂尔多斯高原的地带性植被在传统上分为典型草原、荒漠草原和草原化荒漠3部分,在典型草原的边界划分上,传统划分与本文结果一致。而在荒漠草原和草原化荒漠的边界方面,模拟结果与传统划分有一定的差异。荒漠灌丛和荒漠草原以及荒漠和草原化荒漠在生物群落特征上具有一定的相似性,荒漠灌丛和荒漠在生态特征上较荒漠草原和草原化荒漠更为旱化,在地理位置上更为靠西部。该计算机模型结合了地理空间分析,能准确地确定生态过渡带的位置和宽度,为研究鄂尔多斯高原生态过渡带的特征提供了较可靠的技术手段。     

鄂尔多斯高原生态过渡带的判定及生物群区特征

本文用Holdridge生命地带方法对鄂尔多斯高原的生物群区进行了分类研究,研制了用于生态过渡带判定的计算机模型,模拟结果与实际情况基本吻合。鄂尔多斯高原的生物群区可分为草原、荒漠灌丛和荒漠3大类,草原群区以本氏针茅(Stipa bungeana)群落为主,荒漠灌丛群区以冷蒿(Artemisia frigida),狭叶锦鸡儿(Caragana stenophylla)群落为主,荒漠群区以红砂(Reaumuria soongorica)群落为主。鄂尔多斯高原的地带性植被在传统上分为典型草原、荒漠草原和草原化荒漠3部分,在典型草原的边界划分上,传统划分与本文结果一致。而在荒漠草原和草原化荒漠的边界方面,模拟结果与传统划分有一定的差异。荒漠灌丛和荒漠草原以及荒漠和草原化荒漠在生物群落特征上具有一定的相似性,荒漠灌丛和荒漠在生态特征上较荒漠草原和草原化荒漠更为旱化,在地理位置上更为靠西部。该计算机模型结合了地理空间分析,能准确地确定生态过渡带的位置和宽度,为研究鄂尔多斯高原生态过渡带的特征提供了较可靠的技术手段。     

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.     

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。     

用气象卫星对东亚季风区的生态过渡带的遥感监测研究

用极轨气象卫星的归一化植被指数(NDVI)对中国东亚季风区的生态过渡带(样带)进行遥感监测研究。研究结果表明,在过渡带内的各个生态区的NDVI与东亚季风进退的关系极为密切。在正常季风年NDVI有正常分布;在异常季风年,NDVI呈反常分布;把遥感过渡带内季风气候的变化简化为遥感生态区植被指数的变化。分析了在过渡带内主要生态区,即荒漠草原、干草原、草甸草原、农耕区、森林区ND-VI的变化规律,以及旬NDVI与旬降水量之间的关系。在过渡带内每年NDVI随时间变化的曲线形状可以作为每年季风气候变化特征的量度。     

中国东北样带的梯度分析及其预测

陆地样带研究已成为国际地圈-生物圈计划(IGBP)全球变化研究的重要手段与热点。中国东北样带(NECT)已被列为IGBP国际全球变化陆地样带之一。该样带在东经112°与130°30＇之间沿北纬43°30＇设置,长约1600km,是一条中纬度温带以降水为驱动因素的梯度,具有由温带针阔叶混交林向温带草原的3个亚地带——草甸草原、典型草原与荒漠草原过渡的空间系列。该样带上有4个生态实验站。在大量的固定样地、实验调查研究资料与数据的基础上给出了样带的初步梯度分析及在全球变化图景下的预测,包括其地理位置、设置意义、地形地貌、气候梯度、土壤类型、植被类型和土地利用格局,一个遥感数据驱动的模型和NPP模型在整个样带上运行过。今后NECT将在生物地球化学循环(水、C、N、P等与痕量气体CO_2、CH_4等)、生态系统结构、功能与动态、生物多样性、土地利用与土地覆盖、动态全球植被模型(DGVM)以及高分辨率遥感数据应用等方面得到加强,将成为我国全球变化与陆地生态系统(GCTE)与其它IGBP核心项目研究的前沿阵地。     

惠州市景观格局空间分异特征的梯度分析

本文将景观指数、梯度分析和移动窗口法相结合,分析了惠州市景观格局的空间分异特征。以中心城区为起点,向外等距设置辐射状梯度带;同时结合研究区的特点,设置了4个不同方向的样带。综合运用景观指数粒度效应分析和土地面积变化评价指数模型,确定适合研究区的分析粒度;考虑到景观格局的各向异性,计算不同方向的半变异函数和相应的块基比,确定不同方向样带的分析幅度;采用移动窗口法分析不同方向样带的景观格局特征。结果表明:(1)50 m的栅格大小为适合研究区景观格局分析的粒度值,4条样带上移动窗口的适宜分析尺度分别为750、850、1350、1150 m;(2)从中心城区到外围区域,可将惠州市依次划分为城市中心区、农业区、城市副中心区、过渡区和生态保育区;(3)高强度城市化地区和远郊区的景观组分类型单一,优势度特征明显,城市边缘区或城乡过渡带的景观异质性增加,破碎化程度高;(4)不同方向的样带能够反映景观格局的方向分异特征,是城市景观梯度分析的有效手段。     

Global patterns in the vulnerability of ecosystems to vegetation shifts due to climate change

Aim Climate change threatens to shift vegetation, disrupting ecosystems and damaging human well‐being. Field observations in boreal, temperate and tropical ecosystems have detected biome changes in the 20th century, yet a lack of spatial data on vulnerability hinders organizations that manage natural resources from identifying priority areas for adaptation measures. We explore potential methods to identify areas vulnerable to vegetation shifts and potential refugia. Location Global vegetation biomes. Methods We examined nine combinations of three sets of potential indicators of the vulnerability of ecosystems to biome change: (1) observed changes of 20th‐century climate, (2) projected 21st‐century vegetation changes using the MC1 dynamic global vegetation model under three Intergovernmental Panel on Climate Change (IPCC) emissions scenarios, and (3) overlap of results from (1) and (2). Estimating probability density functions for climate observations and confidence levels for vegetation projections, we classified areas into vulnerability classes based on IPCC treatment of uncertainty. Results One‐tenth to one‐half of global land may be highly (confidence 0.80–0.95) to very highly (confidence ≥ 0.95) vulnerable. Temperate mixed forest, boreal conifer and tundra and alpine biomes show the highest vulnerability, often due to potential changes in wildfire. Tropical evergreen broadleaf forest and desert biomes show the lowest vulnerability. Main conclusions Spatial analyses of observed climate and projected vegetation indicate widespread vulnerability of ecosystems to biome change. A mismatch between vulnerability patterns and the geographic priorities of natural resource organizations suggests the need to adapt management plans. Approximately a billion people live in the areas classified as vulnerable.     

边缘效应的空间尺度与测度

综述了边缘效应的空间尺度类型以及在不同尺度上的测度方法.基于大量的研究整合,认为边缘效应空间尺度的划分,可以根据空间尺度的不同以及边缘效应形成和维持因素,分为大中小3个尺度类型,即大尺度的生物群区交错带、中尺度的景观类型之间的生态交错带和小尺度的斑块(生态系统)之间的群落交错区.大尺度主要是以植被气候带为标志的生物群区间的边缘效应,这种地带性的交错区主要受大气环境条件的影响.中尺度类型主要包括城乡交错带、林草交错带、农牧交错带等类型,是不同生态系统要素的空间交接地带,在物质能量等相互流动的作用下变得更为复杂.小尺度水平上是指斑块之间的交错所形成的边缘效应,受小地形等微环境条件及生物非生物等因子的制约,研究主要集中在群落边缘、林窗边缘和林线交错带等方面.对边缘效应测度的定量化研究有助于更加深入理解边缘效应.在大尺度水平上,边缘效应测度的研究主要是应用数量生态学等方法,研究不同气候带之间界线的划分及其物种分布的梯度规律性.中尺度水平上应用景观生态学的3S技术等方法,侧重于研究交错带的动态变化趋势及位置宽度的判定.小尺度水平上通过对距离边缘的长度,各群落中种群的数量、结构、多样性等定量指标的测定来构建测度公式,从而对边缘效应的强度进行量化,并反映边缘对群落的正负效应.总体上看,主要集中于中小尺度上,未来应该强化大尺度边缘效应测度的研究.     

Spatial scale types and measurement of edge effects in ecology

Classification of spatial scales and measurement of edge effects in ecology were reviewed. The spatial scales can be classified into large scale (biome ecotone), meso-scale (ecological ecotone) and small scale (community ecotone) through the formation and maintenance of edge effects in ecology based on the synthetic analysis of published literatures. The biome ecotone is influenced by climate, regional dominant vegetation and terrain environment. The ecological ecotone is usually distributed in the transitional region with remarkable habitat heterogeneity. It connects adjacent ecosystems and affects the flow of energy and nutrient. Nowadays, study on edge effects in ecology mainly focuses on boundary sensitivity which associates with urban-rural ecotone, forest-grassland ecotone, agro-pastoral ecotone, forest-farmland ecotone, water-land ecotone and forest-swamp ecotone. As to the community ecotone which links with different patches to the interior of the community, previous studies focused on community edge, gap edge and treelines. The borderlines of different biome ecotones and the gradients of species distribution in the biome ecotones have been investigated through the method of quantitative ecology. The dynamic change, location and width of the ecological ecotone have been studied using the Geographic Information System (GIS), Remote Sensing (RS) and Global Positioning System (GPS) technologies and the landscape ecology theory. As important indicators, distance from edge, population, structure and diversity determined for establishing models can be applied to measure the intensity of edge effects and decide the positive or negative impact on communities. Although study on the edge effects in ecology was mostly reported at the meso-scale and small scale, study at large scale should be paid more attention as it is the potential value in ecology and global change fields.     

Efficiency of protected areas in Amazon and Atlantic Forest conservation: A spatio-temporal view

The Amazon and Atlantic Forest are considered the world's most biodiverse biomes. Human and climate change impacts are the principal drivers of species loss in both biomes, more severely in the Atlantic Forest. In response to species loss, the main conservation action is the creation of protected areas (PAs). Current knowledge and research on the PA network's conservation efficiency is scarce, and existing studies have mainly considered a past temporal view. In this study, we tested the efficiency of the current PA network to maintain climatically stable areas (CSAs) across the Amazon and Atlantic Forest. To this, we used an ecological niche modeling approach to biome and paleoclimatic simulations. We propose three categories of conservation priority areas for both biomes, considering CSAs, PAs and intact forest remnants. The biomes vary in their respective PA networks' protection efficiency. Regarding protect CSAs, the Amazon PA network is four times more efficient than the Atlantic Forest PA network. New conservation efforts in these two forest biomes require different approaches. We discussed the conservation actions that should be taken in each biome to increase the efficiency of the PA network, considering both the creation and expansion of PAs as well as restoration programs.     

Anthropogenic and climatic impacts on surface pollen assemblages along a precipitation gradient in north‐eastern China

Aim To understand the scenarios of ‘anthropogenic biomes’ that integrate human and ecological systems, we need to explore the impacts of climate and human disturbance on vegetation in the past and present. Interactions among surface pollen, modern vegetation and human activities along climate and land‐use gradients are tested to evaluate the natural and anthropogenic forces shaping the modern vegetation, and hence to aid the reconstruction of vegetation and climate in the past. This in turn will help with future predictions. Location The North‐east China Transect (NECT) in north‐eastern China. Methods We analysed 33 surface pollen samples and 213 quadrats across four vegetation zones along the moisture/land‐use gradients of the NECT. Detrended correspondence analysis (DCA) and redundancy analysis (RDA) of 52 pollen taxa and three environmental variables were used to distinguish anthropogenic and climatic factors that affect surface pollen assemblages along the NECT. Results The 33 surface samples are divided into four pollen zones (forest, meadow steppe, typical steppe and desert steppe) corresponding to major vegetation types in the NECT. Variations in pollen ratios of fern/herb (F/H), Artemisia/Chenopodiaceae (A/C) and arboreal pollen/non‐arboreal pollen (AP/NAP) represent the vegetation and precipitation gradient along the NECT. DCA and RDA analyses suggest that surface pollen assemblages are significantly influenced by the precipitation gradient. Changes in the abundance of Chenopodiaceae pollen are related to both human activities and precipitation. Main conclusions Surface pollen assemblages, fossil pollen records, archaeological evidence and historical documents in northern China show that a large increase of Chenopodiaceae pollen indicates human‐caused vegetation degradation in sandy habitats. The A/C ratio is a good indicator of climatic aridity, but should be used in conjunction with multiple proxies of human activities and climate change in the pollen‐based reconstruction of anthropogenic biomes.     

气候变暖与荒漠-草原过渡带植物动态响应灰色分析--以美国新墨西哥州Sevilleta生态过渡带为例

在当前全球气候变暖的形势下,地表生态系统表现出不同的响应。干旱-半干旱地区的生态过渡带的生物反应更为敏感。美国新墨西哥州中部的荒漠-草原生态过渡带是监测全球气候变化和人类活动对生物影响的重要区域之一。本文以Sevilleta荒漠．草原生态过渡带为例,运用灰色系统分析方法．研究在当前全球气候变暖的条件下,1989～1998年10年间该生态过渡带的两种共存的植物优势种(Bouteloua eripoda)和(Bouteloua grncilis)历年的种群密度、组合形式和变化趋势,分析引起这些变化的主要气候因子。结果表明,Sevilleta生态过渡带中来自荒漠草原的优势物种Bouteloua eripoda的密度有上升的趋势,来自大草原的优势物种Bouteloua gracilis的密度有下降的趋势,它们的密度比大于1且有上升的趋势;在影响种群密度变化的降水、最高温度、最低温度、湿度的4个气候因子中,温度因子起着重要的作用。由此可以认为,随着气候的变暖,本区来自荒漠地区的优势植物种在荒漠-草原群落过渡带中将逐渐处于强优势地位,生态过渡带将有可能被荒漠草原所替代。     

Losing your edge: climate change and the conservation value of range‐edge populations

Populations occurring at species' range edges can be locally adapted to unique environmental conditions. From a species' perspective, range‐edge environments generally have higher severity and frequency of extreme climatic events relative to the range core. Under future climates, extreme climatic events are predicted to become increasingly important in defining species' distributions. Therefore, range‐edge genotypes that are better adapted to extreme climates relative to core populations may be essential to species' persistence during periods of rapid climate change. We use relatively simple conceptual models to highlight the importance of locally adapted range‐edge populations (leading and trailing edges) for determining the ability of species to persist under future climates. Using trees as an example, we show how locally adapted populations at species' range edges may expand under future climate change and become more common relative to range‐core populations. We also highlight how large‐scale habitat destruction occurring in some geographic areas where many species range edge converge, such as biome boundaries and ecotones (e.g., the arc of deforestation along the rainforest‐cerrado ecotone in the southern Amazonia), can have major implications for global biodiversity. As climate changes, range‐edge populations will play key roles in helping species to maintain or expand their geographic distributions. The loss of these locally adapted range‐edge populations through anthropogenic disturbance is therefore hypothesized to reduce the ability of species to persist in the face of rapid future climate change.     

中国东北样带土壤氮的分布特征及其对气候变化的响应

根据2001年中国东北样带土壤全氮和有效氮的实测数据,结合CO₂浓度倍增与不同土壤湿度的模拟试验数据,对土壤全氮和有效氮的梯度分布、影响因子分析及其对气候变化的响应进行研究.结果表明,样带土壤表层全氮和有效氮的梯度分布与土壤有机碳的分布基本一致:沿经度呈现东高西低的趋势,局部由于土壤退化而出现低谷.土壤全氮的剖面分布和土壤有机碳相似,而土壤有效氮则有所不同.样带土壤全氮和有效氮与土壤pH、有机碳、全磷、全硫、全锌、土壤活性碳、有效磷、有效钾、有效锰、有效锌、土壤容重、田间持水量、土壤总孔度等因子均呈显著或极显著的相关关系.样带土壤全氮和有效氮与降雨量之间呈极显著的正相关关系(r=0.682,P＜0.001和0.688,P＜0.001).短期培养试验中,CO₂浓度倍增和不同土壤湿度下土壤全氮和有效氮的变异较小(变异系数分别是5.55%和3.84%),但可反映一定的变化趋势.