景观破碎化对东北虎主要猎物种群动态影响的模拟

以完达山东部地区的现实景观为背景,采用空间直观种群模型LAPS和情景模拟相结合的"虚拟实验"途径,模拟了在10个不同破碎化程度的景观情景中东北虎的主要猎物于1992-2011年间的种群动态,评价了完达山东部地区当前的景观破碎化程度对东北虎主要猎物种群动态的影响。结果表明:LAPS模型准确刻画了研究区东北虎主要猎物种群数量急剧下降的趋势,2002年模拟的东北虎主要猎物的种群数量和实测值之间没有显著差异,马鹿、野猪和狍子的P值分别为0.8651、0.9534和0.2836;不同生境类型的种群密度数据与实测值之间均没有显著差异,其中阔叶林生境中的马鹿、野猪和狍子的P值分别为0.8521、0.9447和0.3152;在灌丛生境中的马鹿、野猪和狍子的P值分别为0.8846、0.9576和0.2415。斑块类型和景观水平上的格局指标变化趋势表明由于农田扩张导致10个景观情景的破碎化程度逐渐增加,景观水平的破碎化程度低于斑块类型水平。方差分析显示10个景观情景中的种群数量没有显著差异,马鹿、野猪和狍子的P值分别为0.8516、0.2624和0.7636,说明研究区当前的景观破碎化程度对种群动态影响并不显著。完达山东部地区存在盗猎等人为干扰,导致了东北虎主要猎物的数量远低于环境容纳量,景观破碎化虽然在局部地区较为严重,但完达山东部地区整体上景观破碎化并不强烈,该地区景观破碎化的效应尚未显现。认为控制盗猎等人为干扰是增加该地区东北虎主要猎物的数量、实现东北虎种群恢复所应优先采取的措施。     

异质种群动态模型:破碎化景观动态模拟的新途径

景观破碎化导致物种以异质种群方式存活,使得基于异质种群动态模拟破碎化景观动态成为可能。异质种群动态模型的发展为景观动态模拟奠定了良好基础。根据空间处理方式的不同,异质种群模型可分为三大类,可不同程度地用于描述破碎化景观动态。(1)空间不确定异质种群模型,假定所有局域种群间均等互联,模型中不包含空间信息,仅能用于景观斑块动态描述;(2)空间确定异质种群模型,假设局域种群在二维空间上以规则格子形式排列,是一种准现实的空间处理方式,可用于景观动态的简单描述;(3)空间现实异质种群模型,包含了破碎化景观中局域种群的几何特征,可直接用于真实景观动态的模拟研究。空间现实的和基于个体的异质种群模型不但是未来异质种群模型发展的主流,也将成为未来破碎化景观动态研究的重要工具。为了更加准确完整地描述破碎化景观动态,不但应该综合运用已有的各种异质种群模型方法,更要引进新模型来刎画多物种、多变量、高维度、复杂连接的破碎化景观格局与过程。     

景观生态学:两栖动物生态学研究的新途径

全球两栖动物正以远超过自然灭绝的高速率灭绝,这与生境丧失和景观破碎化有着直接关系。生境丧失导致两栖动物的生存空间减少,使局部种群消失,而景观破碎化则导致两栖动物种群之间的隔离度增加,不利于动物的繁殖和扩散。但两者往往是同时出现,相互作用。复合种群、景观连接度、景观遗传学及景观模型模拟等理论和方法的发展,为在生境丧失与破碎化景观下两栖动物的种群结构、组成和动态变化研究提供了理论基础和技术方法。同时景观生态学中特别重视研究的尺度,生境破碎化是发生在景观尺度下的生境变化过程,因此对生境破碎化的影响应该从现有的主要集中在斑块尺度和斑块-景观尺度转变到景观尺度上来。     

生境破碎化对生物多样性的影响

生境破碎化对生物多样性和生态系统功能的影响是当前国内外生态学家研究的热点问题之一。生境破碎化导致原生境的总面积减小,产生隔离的异质种群,从而影响个体行为特性、种群间基因交换、物种间相互作用及生态过程。生境破碎化的过程引起栖息地内部食物、繁殖场所、局部小气候、边缘效应等生物和非生物条件的变化,从而影响植物种群的大小和灭绝速率、扩散和迁入、遗传和变异以及存活力等,影响动物种群的异质种群动态、适宜生境比例、灭绝阈值、种间关系等。随着景观生态学与农业科学的融合,探索利用景观布局控制害虫发生将是人类利用生境破碎化为人类服务的一条新途径。     

扩散对破碎化景观上宿主-寄生种群动态的影响

景观破碎化和扩散是空间种群模型的重要因素,对生物入侵存在着深远的影响。本章将基于偶对近似模型,探讨由局部和全局宿主-寄生相互作用共同决定的扩散模式对破坏性景观上疾病入侵与传播的影响。其中,生境破坏由生境丧失量与生境破碎化程度来描述。模拟结果显示,宿主和病毒的全局扩散对疾病的入侵与种群密度产生不对称效应：病毒的全局扩散对系统产生的影响较宿主的全局扩散更为显著。不同扩散模式下,生境丧失越高或破碎化程度越低,均将越有害于寄生病毒的入侵;同时,生境的破坏程度也显著地影响了入侵阈值对扩散模式的响应机制。本文研究结果暗示,景观破碎化的空间分布格局以及病毒扩散的限制均可作为物种保护与管理中有效的疾病控制策略。该研究结果在一定意义上丰富和发展了寄生感染理论,为物种保护提供了生态学理论依据。     

生境破碎化对动物种群存活的影响

生境破碎是生物多样性下降的主要原因之一。通常以岛屿生物地理学、异质种群生物学和景观生态学的理论来解释不同空间尺度中生境破碎化的生态学效应。生境破碎化引起面积效应、隔离效应和边缘效应。这些效应通过影响动物种群的绝灭阈值、分布和多度、种间关系以及生态系统过程,最终影响动物种群的存活。野外研究表明,破碎化对动物的影响,因物种、生境类型和地理区域不同而有所变化,因此,预测物种在破碎生境中的存活比较困难。研究热点集中于：确定生境面积损失和生境斑块的空间格局对破碎景观中物种绝灭的相对影响,破碎景观中物种的适宜生境比例和绝灭阈值,异质种群动态以及生态系统的生态过程。随着3S技术的发展,生境破碎化模型趋于复杂,而发展有效的模型和验证模型将成为一项富有挑战性的任务。     

棉花生境面积及其破碎化对烟粉虱种群的影响

【目的】阐明棉花生境面积变化及其破碎化对烟粉虱Bemisiatabaci种群的作用规律,为合理利用作物布局进行害虫生态调控提供理论支撑。【方法】采用国际流行的微景观试验模型系统(Experimental model landscape system,EMLS)进行试验设计,田间条件下连续两年研究了棉花生境面积变化(20%、40%、60%、80%和100%;其他为玉米生境面积)及2种极端破碎化(完全连通C clumped:H=1.0;完全破碎F fragmented:H=0.0)下烟粉虱种群数量变化,采用广义线性模型(GLM)分析各因素对烟粉虱种群数量的影响。【结果】棉花生境面积及其破碎化单独作用时均对烟粉虱种群数量无显著影响,而取样时间则有显著影响。烟粉虱种群数量也没有受到取样时间与棉花生境面积、取样时间与破碎化以及三者交互作用的显著影响。但是,棉花生境面积与破碎化的互作效应则存在年度变化,2014年无显著作用,2015年显著影响烟粉虱种群。当棉花生境面积较小(20%)或较大(80%)时,破碎化程度高,烟粉虱种群数量少;棉花生境面积中等(40%和60%)时,破碎化程度低,烟粉虱种群数量少。【结论】烟粉虱种群对棉花生境面积变化有较强的适应性,而生境破碎化只能在一定程度上产生影响。     

区域农田景观格局对麦蚜种群数量的影响

明确农田景观格局对麦田蚜虫种群的影响,是开展区域性害虫生态调控的重要理论依据之一。以区域性小麦种植区为研究对象,基于遥感影像与土地覆盖分类数据以及田间调查的蚜虫种群数据,计算景观格局指数,使用负二项分布的广义线性模型从农田景观、非作物生境景观和区域景观3个方面分析了区域农田景观格局对麦田蚜虫种群的影响。结果表明,蚜虫种群的数量与草地的平均斑块面积和最大斑块指数显著正相关,与县域的平均几何最邻近距离和面积加权平均斑块面积显著负相关,与耕地的面积加权平均斑块面积显著负相关,与耕地的斑块密度显著正相关。草地斑块面积的增大、区域景观与耕地的破碎化、区域景观的聚集会促进蚜虫种群数量的增加。使用草地的斑块面积和最大斑块指数、区域景观的平均几何最邻近距离可以预测蚜虫种群的发生量。非作物生境草地的斑块面积、耕地的破碎化、区域景观的空间分布及破碎化是影响麦田蚜虫种群发生的重要景观因素。     

基于GWR模型的道路对景观破碎化影响研究

道路是影响区域景观破碎化的重要因素, 但以往的研究往往忽视这种影响在局部空间上的差异。以惠州市为研究区, 选取国道和省道作为城市主要道路, 引入地理加权回归模型(GWR), 通过道路距离与景观破碎度的关系分析城市主要道路对景观破碎化的影响, 并揭示道路对景观破碎化影响的空间异质性。结果表明: (1)研究区的景观破碎化具有显著的空间集聚现象, 使用GWR 模型分析具有更好的拟合效果。(2)道路对不同类型景观的破碎化造成了不同的影响: 在景观水平上, 道路距离与景观破碎度主要呈正相关关系; 在类型水平上, 道路距离与林地破碎度主要呈正相关关系, 与耕地和城乡建设用地破碎度主要呈负相关关系。(3)道路距离与景观破碎化的关系在不同的空间位置存在差异, 正相关和负相关区域的分布均呈现明显的空间集聚特征。(4)两者关系的空间异质性反映出除了道路外, 地形和所处位置到城市中心的距离对景观破碎化的共同影响。研究结果有利于进一步揭示道路对景观格局变化的影响机制。      

生境破碎化对生物多样性的影响研究综述

生境破碎化与生物多样性的关系是理论生态学的研究热点。本文在综述国内外相关研究内容的基础上,阐述了生境破碎化的概念内涵与度量,介绍了生境破碎化研究的主要理论基础、研究内容与研究进展;总结了目前生境破碎化研究存在度量破碎景观格局的方法尚未统一、研究方法有待精确以及生境破碎化与生物多样性的阈值效应尚未发现等问题。今后,半干旱地区生境破碎化对生物多样性影响的研究需要加强,空间分析理论和方法将会在生境破碎化对生物多样性影响的研究中得到更多应用。     

大兴安岭北部林区景观格局变化及其影响分析

人为干扰影响着景观格局变化的速率和方向 ,这在景观格局变化过程中的作用越来越大 ,同时景观格局的变化也对人类活动产生了重大影响。通过对大兴安岭北部林区的景观多样性指数、优势度指数等一系列景观指数来研究该地区森林景观格局的变化 ,简要分析了格局变化产生的影响。结果表明 ,大兴安岭森林景观中 ,人为干扰使森林景观短时期内多样性增加、森林的优势度降低 ;景观向破碎化趋势发展 ;景观格局的变化对环境和人类活动产生了重大影响 ,森林向不可持续方向发展 ,因此应该进行合理的人类活动使森林可持续发展。     

Predicting extinction risks under climate change: coupling stochastic population models with dynamic bioclimatic habitat models

Species responses to climate change may be influenced by changes in available habitat, as well as population processes, species interactions and interactions between demographic and landscape dynamics. Current methods for assessing these responses fail to provide an integrated view of these influences because they deal with habitat change or population dynamics, but rarely both. In this study, we linked a time series of habitat suitability models with spatially explicit stochastic population models to explore factors that influence the viability of plant species populations under stable and changing climate scenarios in South African fynbos, a global biodiversity hot spot. Results indicate that complex interactions between life history, disturbance regime and distribution pattern mediate species extinction risks under climate change. Our novel mechanistic approach allows more complete and direct appraisal of future biotic responses than do static bioclimatic habitat modelling approaches, and will ultimately support development of more effective conservation strategies to mitigate biodiversity losses due to climate change.     

破碎化生境中粗柄独尾草种群大小对繁殖特性的影响

景观破碎化是目前存在的一种普遍现象,导致物种生存的原有生境总面积减小,产生许多大小不一的斑块种群。不同斑块生境中植物种群的大小直接反映植物对环境的响应特征和适应对策,与植物繁殖有关的开花结实特性、种子形态及萌发特性的研究将有助于深入了解植物在不同生境中的生存策略。以粗柄独尾草(Eremurus inderiensis)为研究对象,以野外调查为基础,对比研究不同斑块粗柄独尾草种群的种群大小和生殖成功,揭示不同生境中粗柄独尾草的生态适应性。结果表明:(1)不同斑块生境中,种群大小差异较大,且较小的种群幼苗比例也较小,种群大小与种群幼苗比例呈显著相关;(2)较小的种群自然座果率、结籽率较低,种群间差异显著;(3)随着生境破碎化程度增加,种子千粒重,种子长、宽等形态特征呈减小趋势,但种翅占比增大;(4)在粗柄独尾草最适萌发温度下,随着生境破碎化程度增加,种子萌发率有下降趋势。针对人类干扰程度强的衰退型粗柄独尾草种群,亟需减少人为干扰,依据不同生境中的干扰因素及种群生存现状,制定科学与切实可行的保护和恢复策略。     

Population Status and Reproductive Success of an Endangered Epiphytic Orchid in a Fragmented Landscape

Habitat fragmentation and disturbance are two of the most significant drivers of species extinctions in plant populations. The degree of impact of fragmentation on plant populations depends on the level of specificity of plant–animal interactions, as well as on the availability of suitable sites for seedling recruitment. In this study, we describe the population density and structure, pollen limitation and reproductive success of the endangered tropical orchid Myrmecophila christinae, an epiphytic species with a specialized pollination system. We surveyed a total of 14 populations located in a fragmented landscape. Seedling density was related to habitat disturbance and host plant density; while density of juveniles was related to density of adults. Adult and total individual densities were related to habitat affectation. We also found that fragments <1 ha had significantly fewer seedlings, as well as an over‐representation of large adults. On the other hand, fruit production was higher in fragments >10 ha, and fruit set was significantly lower in highly disturbed fragments. Hand pollination experiments showed that M. christinae was pollen limited in all the studied populations, suggesting that pollen limitation is unrelated to habitat disturbance. Overall, our results suggest that fragmentation has affected key demographic features of M. christinae, including reproduction and recruitment.     

栖息地片断化对动物种群间基因流的影响及其测定方法

栖息地片断化指在人为活动和自然干扰下,大面积连续分布的自然栖息地被其它非适宜栖息地分隔成许多面积较小的斑块(岛屿)的过程。栖息地片断化是导致生物多样性丧失和物种绝灭的主要因素,也是威胁自然界生物生存的重要因素之一。栖息地片断化将影响基因在种群间和种群内的运动(基因流),开展栖息地片断化研究对保持物种间遗传多样性具有重要意义。本文介绍了片断化程度和基因流的测定方法。回顾了国内外的研究现状,并探讨了片断化对种群间基因流的影响和对濒危物种保护的意义。     

Environmental factors affecting population level genetic divergence of the striped field mouse (<Emphasis Type="Italic">Apodemus agrarius</Emphasis>) in South Korea

The cognizing of connectivity among small mammal populations across heterogeneous landscapes is complicated due to complex influences of landscape and anthropogenic factors on gene flow. A landscape genetics approach offers inferences on how landscape features drive population structure. Through a landscape genetics approach, we investigated influences of geographical, environmental, and anthropogenic features on populations of Apodemus agrarius, the striped field mouse, the prime vector of hemorrhagic fever by a landscape genetic approach. We identified landscape features that might affect the population structure of striped field mice by analyzing microsatellite markers of 197 striped field mice from 21 populations throughout South Korea. We developed Maximum-likelihood population effects models based on landscape distances and resistance matrices and pairwise F_ST values for meta-populations of striped field mouse. We also conducted Mantel and partial Mantel tests to investigate geographic patterns of genetic similarities. In Mantel and partial Mantel tests, the F_ST was significantly correlated with all three models of movement; movement cost, Euclidian distance and least-cost distance, although the magnitudes of correlations varied. The 4 top-ranked models included three variables; temperature, precipitation and one human disturbance factor (population). We did not attain a significant effect for anthropogenic factors on genetic similarities among populations in the Korean striped field mouse, but we confirmed a significant association for genetic similarity with climatic features (temperature and precipitation).     

Does Landscape Fragmentation Influence Sex Ratio of Dioecious Plants? A Case Study of Pistacia chinensis in the Thousand-Island Lake Region of China

The Thousand-Island Lake region in Zhejiang Province, China is a highly fragmented landscape with a clear point-in-time of fragmentation as a result of flooding to form the reservoir. Islands in the artificial lake were surveyed to examine how population sex ratio of a dioecious plant specie Pistacia chinensis B. was affected by landscape fragmentation. A natural population on the mainland near the lake was also surveyed for comparison. Population size, sex ratio and diameter at breast height (DBH) of individuals were measured over 2 years. More than 1,500 individuals, distributed in 31 populations, were studied. Soil nitrogen in the different populations was measured to identify the relationship between sex ratio and micro-environmental conditions. In accordance with the results of many other reports on biased sex ratio in relation to environmental gradient, we found that poor soil nitrogen areas fostered male-biased populations. In addition, the degree of sex ratio bias increased with decreasing population size and population connectivity. The biased sex ratios were only found in younger individuals (less than 50 years old) in small populations, while a stable 1∶1 sex ratio was found in the large population on the mainland. We concluded that the effects of landscape fragmentation on the dioecious population sex ratio were mainly achieved in relation to changing soil nitrogen conditions in patches and pollen limitation within and among populations. Large populations could maintain a more suitable environment in terms of nutrient conditions and pollen flow, subsequently maintaining a stable sex ratio in dioecious plant populations. Both micro-environmental factors and spatial structure should be considered in fragmented landscape for the conservation of dioecious plant species.     

Potential impacts of climate and landscape fragmentation changes on plant distributions: Coupling multi-temporal satellite imagery with GIS-based cellular automata model

Climate change and landscape fragmentation are considered to be the main treats to biodiversity. In this study, probable alteration of future species distribution was tested based on the association of landscape fragmentation and climate change scenarios compared to the classical approach that assumed an unchanged landscape. Also, projected range shifts including realistic dispersal scenarios were compared with classical models, in which no or full dispersal has been supposed.A GIS-based cellular automata model, MigClim, was implemented to projection of future distribution over the 21st century for three plant species in a study area of the central Germany. For each species, simulations were run for four dispersal scenarios (full dispersal, no dispersal, realistic dispersal, and realistic dispersal with long-distance dispersal events), two landscape fragmentation (static and dynamic change) and two climate change (RCP4.5 and RCP8.5) scenarios. In this research, temporal satellite data were utilized to simulate landscape changes by the use of a hybrid (CA-Markov) model for the years 2020, 2040, 2060 and 2080.A significant difference appears to be between the simulations of realistic dispersal limitations and those considering full or no dispersal for projected future distributions. Although simulations accounting for dispersal limitations produced, for our study area, results that were closer to no dispersal than to full dispersal. Additionally, our results revealed that change in landscape fragmentation is more effective than the climate change impacts on species distributions in this study.     

Landscape structure effects on forest plant diversity at local scale: Exploring the role of spatial extent

Since landscape attributes show different patterns at different spatial extents, it is fundamental to identify how the relation between landscape structure and plant species diversity at local scale varies with scale. Then, it is fundamental to assess the appropriate extent at which landscape factors affect plant species richness at the local scale. To investigate this relation, data on plant species richness of forest communities at plot scale were extracted from a large data set and landscape metrics were calculated around the same plots for a range of extents (250–3000 m). Then, multiple regression models and variance partitioning techniques were applied to assess the amount of variance explained by the landscape metrics on plant species richness for a range of extents. In general, we found that increasing extent of the surrounding landscape analyzed, improved the strength of relationship between the landscape metrics and the properties of plant communities at plot scale. The medium-large extent was most informative as it combined a decent total variance explained with high variance explained by the pure fractions of complexity, fragmentation and disturbance and the minimum of collinearity. In conclusion, we found that it is possible and beneficial to identify a specific extent, where the redundancy in the predictor variables is minimized and the explanatory power of the pure fractions (or single groups) maximized, when examining landscape structure effects on local plant species richness.     

Applying a continua landscape approach to evaluate plant response to fragmentation: Primula vulgaris in the Cantabrian mountains

Question: Continua landscape approaches conceptualize the effects of habitat fragmentation on the biota by considering fragmented landscapes as continuous gradients, departing from the view of habitat as either suitable (fragment) or unsuitable (matrix). They also consider the ecological gradients or the ‘Umwelt’ (species‐specific perception of the landscape) to represent the processes that ultimately limit organisms' ability to colonize and persist within habitat remnants. Are these approaches suitable for evaluating the response of plant species to fragmentation? Location: Fragmented mid‐elevation temperate forests, Cantabrian range, Spain. Methods: The presence, abundance and demographic structure of populations of the perennial herb Primula vulgaris were sampled across a continuous extent of 100 ha, subdivided into 400 50 m × 50 m sampling units. These variables were related to forest availability, forest subdivision and edge density, topography and the spatial clumpiness of populations (a measure of plant dispersal constraints and, hence, a major surrogate of plant Umwelt). Results: Fragmentation processes, especially habitat loss, negatively affect P. vulgaris, with a stronger effect on presence than on abundance and demography. Despite the importance of habitat availability, P. vulgaris does not occupy all potentially suitable forest habitat, mostly owing to dispersal constraints. A positive effect of slope on plant presence also suggests some effect of habitat quality in determining establishment and occupancy of forest landscape. Conclusions: Within‐habitat dispersal constraints are as important as forest fragmentation in determining the landscape‐scale distribution of P. vulgaris. By assessing the relative role of the diverse fragmentation processes, and of the species' landscape perception, a continua landscape approach proves to be a valuable tool for predicting plant response to landscape change.