小尺度下柠条林破碎化生境对地表甲虫多样性的影响

一般认为,景观斑块面积和破碎化对物种丰富度和分布格局有重要的影响。在宁夏中部荒漠地区,天然柠条林和人工柠条林地交错排列,形成点、片、带状等大小不等的斑块性分布,表现为典型的破碎化斑块格局生境特征。本文采用巴氏罐诱法调查了在小尺度下荒漠景观人工柠条林破碎化生境不同斑块内地表甲虫的物种多样性。结果共获得10科20属29种地表甲虫,其中拟步甲科昆虫占绝对优势,阿小鳖甲Microdera kraatzi alashanica Skopin、克小鳖甲Microdera kraatzi kraatzi(Reitter)为优势种。Rarefaction曲线显示较大面积的斑块有较多的物种多样性,但群落多样性指数各斑间块差异不显著。利用斑块面积对物种数-个体数进行回归分析表明,地表甲虫的物种多样性受斑块面积的影响,生境破碎化会导致地表甲虫多样性下降。     

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。     

宏生态尺度上景观破碎化对物种丰富度的影响

生物多样性的地理格局及其形成机制是宏生态学与生物地理学的研究热点。大量研究表明,景观尺度上的生境破碎化对物种多样性的分布格局具有重要作用,但目前尚不清楚这种作用是否足以在宏生态尺度上对生物多样性地理格局产生显著影响。利用中国大陆鸟类和哺乳动物的物种分布数据,在100 km×100 km网格的基础上生成了这两个类群生物的物种丰富度地理格局,进一步利用普通最小二乘法模型和空间自回归模型研究了物种丰富度与气候、生境异质性、景观破碎化的相关关系。结果表明,景观破碎化因子与鸟类和哺乳动物的物种丰富度都具有显著的关联关系,其方差贡献率可达约30%—50%(非空间模型)和60%—80%(空间模型),略低于或接近于气候和生境异质性因子。方差分解结果显示,景观破碎化因子与气候和生境异质性因子的方差贡献率的重叠部分达20%—40%。相对鸟类而言,景观破碎化对哺乳动物物种丰富度的地理格局具有更高的解释率。     

生境破碎化对植物-昆虫及昆虫之间相互关系的影响

生境破碎化对生物多样性和生态系统功能影响是当前国内外生态学家研究的热点问题之一。文章针对生境破碎化的内涵、量度指标进行介绍,着重分析生境破碎化对植物-昆虫关系的影响,包括植物与植食性昆虫的关系、植物与传粉昆虫的关系、种子与种子捕食者的关系,植物及其分解者的关系,还分析生境破碎化对昆虫-昆虫关系的影响,包括昆虫及其拟寄生物的关系、捕食者与猎物的关系。通过对上述方面的阐述,旨在更好地理解生境破碎化对动植物群落相互关系产生的深刻影响,并提出今后研究中应注意的问题和研究热点。     

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。     

黑龙江省完达山地区马鹿生境破碎化及其影响因子

应用景观生态学原理和地理信息系统技术,分析黑龙江省完达山地区马鹿生境相关因子重要性、对景观连接度进行模糊相对赋值,建立了景观连接度评价模型及景观斑块指数,研究了黑龙江省完达山地区关于马鹿生境的景观连接度水平、生境的适宜性以及景观的空间结构。结果表明:(1)在155.6km2的面积中,适宜地区的总面积仅为14.81km2,占研究地区的9.52%;次适宜地区的总面积为9.57km2,占研究地区的6.15%;一般适宜地区的总面积为130.05km2,占研究地区的83.58%;不适宜地区的总面积为1.17km2,占研究地区的0.75%;(2)研究地区马鹿各类适宜地区呈多个斑块且相互隔离,在空间分布上处于破碎状态,而且不适宜地区斑块(人为活动景观)的面积比例虽小,在生态系统中形态上的破碎化程度较小,但对马鹿的生境的生态功能的丧失起到重要作用。     

漫湾库区景观破碎化对区域生境质量的影响

水利工程的建设不仅改变了库区的景观格局,还会导致区域生物生境质量的变化。以澜沧江漫湾库区为例,在综合海拔高度、植被类型和水源地距离生境因子的基础上,考虑生物扩散过程,研究了建坝前后整个库区以及典型研究小区(库首、库中、库尾、对照)的重要生境斑块空间分布变化。结果表明:漫湾水电站建成后库区的猕猴总体生境破碎化程度增加,景观连接度减少且重要生境斑块的比例也有所降低,生境质量整体下降;4个研究小区的景观格局变化情况同整个库区相一致。空间上,生境质量明显退化的地区主要分布在库区的西部和南部,尤其是库尾地区,其生境斑块数量相较于建坝前增长了9倍,而景观连接度指数下降了81.48%。回归分析结果表明景观连接度指数与占景观面积百分比指数(PLAND)呈显著正相关(R~2=0.973),与斑块数(NP)呈显著负相关(R~2=-0.611);肯德尔系数表明斑块数(NP)、最大斑块指数(LPI)、占景观百分比指数(PLAND)、相似邻近百分比指数(PLADJ)、连通度指数(CONNECT)和香农多样性指数(SHDI)7个景观格局指数与景观连接度指数均表现出显著一致性。由此看出,库区景观破碎化越严重、区域景观连接度越低生境质量退化越明显;而提高生境主要植被类型的覆盖率、保护连接度贡献大的重要斑块和建设生态廊道,可以有效恢复库区生物生境质量。     

生境破碎化对丹顶鹤巢位选择的影响

1985、1995年和1998年4－5月,采用查阅保护区历史资料及实地调查方法,对辽宁双台河口国家级自然保护区内丹顶鹤（Grus japonensis)的主要营巢地－东郭苇场和赵圈河苇场的生境破碎化及丹顶鹤在2片苇场中的营巢状况和繁殖种群数量变动情况作了系统的考察和研究,发现丹顶鹤的营巢生境破碎严重,已由成片的芦苇湿地变成91个斑块,其中最小营巢斑块面积为0．37km^2,最小巢间距为304m,比过去资料记载的最小巢区面积缩小了0．72km^2,但繁殖种群数量变动不大,多年来一直维持在30对左右,丹顶鹤为了适应变化了的环境,已采取了缩小巢区面积的生态适应对策。     

广西黑叶猴栖息地景观格局破碎化分析及其对种群的影响

黑叶猴(Trachypithecus francoisi)是仅分布于喀斯特石山生境的珍稀濒危灵长类动物。由于非法捕杀和人类活动干扰,其种群数量正在急剧减少。同时,随着森林砍伐和土地开垦的加速,其栖息地严重破碎化。因此,了解栖息地破碎化对黑叶猴种群的影响对于保护这一珍稀濒危物种具有重要意义。基于遥感影像、土地利用数据以及黑叶猴种群调查数据,通过Fragstats软件开展广西黑叶猴栖息地景观破碎化分析,并通过相关性和多元逐步回归分析,探讨了景观格局对广西黑叶猴种群数量的影响。结果表明：(1)广西黑叶猴栖息地呈现破碎化严峻、斑块形状复杂化、斑块团聚程度较弱且分散化的现象;栖息地以林地景观占据重要优势,但人为景观的干扰十分强烈;在不同地区中,生境破碎化程度、人为干扰强度以及景观配置均呈现不同的特征,其中扶绥地区人为干扰最为强烈,德保地区的景观块数破碎化程度较为严重,而龙州地区的人为干扰程度最小,其森林景观最为聚集。(2)蔓延度指数、平均斑块分维指数、林地面积、林地斑块大小、裸岩面积和裸岩面积比重等景观指数与黑叶猴种群数量有显著正向关系,Shannon多样性指数则是显著负向关系;而耕地面积、耕地...     

农田景观格局对南疆枣园传粉昆虫群落多样性的影响

[目的]明确新疆南疆地区农田景观格局对枣园传粉昆虫群落多样性的影响.[方法]2019和2020年在新疆阿克苏地区共选取29个试验站点,通过陷阱诱集法获取中心枣园内传粉昆虫多样性数据,调查中心枣园周围半径2 000 m范围内土地使用信息,建立枣园传粉昆虫群落指数与景观变量之间的线性混合模型,使用基于赤池信息准则的多模型推...     

Effects of habitat loss, habitat fragmentation, and isolation on the density, species richness, and distribution of ladybeetles in manipulated alfalfa landscapes

Abstract.  1. Habitat loss and fragmentation are the main causes of changes in the distribution and abundance of organisms, and are usually considered to negatively affect the abundance and species richness of organisms in a landscape. Nevertheless, habitat loss and fragmentation have often been confused, and the reported negative effects may only be the result of habitat loss alone, with habitat fragmentation having nil or even positive effects on abundance and species richness.
2. Manipulated alfalfa micro-landscapes and coccinellids (Coleoptera: Coccinellidae) are used to test the effects habitat loss (0% or 84%), fragmentation (4 or 16 fragments), and isolation (2 or 6 m between fragments) on the density, species richness, and distribution of native and exotic species of coccinellids.
3. Generally, when considering only the individuals in the remaining fragments, habitat loss had variable effects while habitat fragmentation had a positive effect on the density of two species of coccinellids and on species richness, but did not affect two other species. Isolation usually had no effect. When individuals in the whole landscape were considered, negative effects of habitat loss became apparent for most species, but the positive effects of fragmentation remained only for one species.
4. Native and exotic species of coccinellids did not segregate in the different landscapes, and strong positive associations were found most often in landscapes with higher fragmentation and isolation.
5. The opposing effects of habitat loss and fragmentation may result in a nil global effect; therefore it is important to separate their effects when studying populations in fragmented landscapes.     

Climate change and human colonization triggered habitat loss and fragmentation in Madagascar

The relative effect of past climate fluctuations and anthropogenic activities on current biome distribution is subject to increasing attention, notably in biodiversity hot spots. In Madagascar, where humans arrived in the last ~4 to 5,000 years, the exact causes of the demise of large vertebrates that cohabited with humans are yet unclear. The prevailing narrative holds that Madagascar was covered with forest before human arrival and that the expansion of grasslands was the result of human‐driven deforestation. However, recent studies have shown that vegetation and fauna structure substantially fluctuated during the Holocene. Here, we study the Holocene history of habitat fragmentation in the north of Madagascar using a population genetics approach. To do so, we infer the demographic history of two northern Madagascar neighbouring, congeneric and critically endangered forest dwelling lemur species—Propithecus tattersalli and Propithecus perrieri—using population genetic analyses. Our results highlight the necessity to consider population structure and changes in connectivity in demographic history inferences. We show that both species underwent demographic fluctuations which most likely occurred after the mid‐Holocene transition. While mid‐Holocene climate change probably triggered major demographic changes in the two lemur species range and connectivity, human settlements that expanded over the last four millennia in northern Madagascar likely played a role in the loss and fragmentation of the forest cover.     

The geometry of habitat fragmentation: Effects of species distribution patterns on extinction risk due to habitat conversion

Land‐use changes, which cause loss, degradation, and fragmentation of natural habitats, are important anthropogenic drivers of biodiversity change. However, there is an ongoing debate about how fragmentation per se affects biodiversity in a given amount of habitat. Here, we illustrate why it is important to distinguish two different aspects of fragmentation to resolve this debate: (a) geometric fragmentation effects, which exclusively arise from the spatial distributions of species and habitat fragments, and (b) demographic fragmentation effects due to reduced fragment sizes, and/or changes in fragment isolation, edge effects, or species interactions. While most empirical studies are primarily interested in quantifying demographic fragmentation effects, geometric effects are typically invoked as post hoc explanations of biodiversity responses to fragmentation per se. Here, we present an approach to quantify geometric fragmentation effects on species survival and extinction probabilities. We illustrate this approach using spatial simulations where we systematically varied the initial abundances and distribution patterns (i.e., random, aggregated, or regular) of species as well as habitat amount and fragmentation per se. As expected, we found no geometric fragmentation effects when species were randomly distributed. However, when species were aggregated, we found positive effects of fragmentation per se on survival probability for a large range of scenarios. For regular species distributions, we found weakly negative geometric effects. These findings are independent of the ecological mechanisms which generate nonrandom species distributions. Our study helps to reconcile seemingly contradictory results of previous fragmentation studies. Since intraspecific aggregation is a ubiquitous pattern in nature, our findings imply widespread positive geometric fragmentation effects. This expectation is supported by many studies that find positive effects of fragmentation per se on species occurrences and diversity after controlling for habitat amount. We outline how to disentangle geometric and demographic fragmentation effects, which is critical for predicting the response of biodiversity to landscape change.     

Effects of habitat fragmentation on the functional diversity of insects in Thousand Island Lake,China

Due to habitat fragmentation, the loss of species diversity has been extensively studied. On the contrary, the effects of habitat fragmentation on functional diversity is still poorly understood. In the Thousand Island Lake, we conducted studies of insect functional diversity on a set of 29 isolated islands. We used 10 functional diversity indices from three aspects (functional richness, functional evenness and functional divergence) to respectively describe functional diversity of insects on sample islands. We found the following results: (i) The functional indices selected could reflect the functional diversity of sample islands and it is further proved that in general, three components of functional diversity were independent of each other; (ii) Sample islands could be divided into two categories, island JSD and the remaining islands; (iii) Functional richness increased with island area and shape index, but had no significant correlation with isolation. Likewise, both functional evenness and functional divergence had no significant correlation with island attributes. The conclusion to emphasize from our research is that: (i) habitat fragmentation reduced the biological functional diversity to some extent, further demonstrating the importance of habitat continuity in biodiversity protection; and (ii) for functional diversity protection of insects in a fragmented landscape, an island which has high approximate shape index values of at least hundred hectare magnitude order has a critical promoting effect.     

How fire interacts with habitat loss and fragmentation

Biodiversity faces many threats and these can interact to produce outcomes that may not be predicted by considering their effects in isolation. Habitat loss and fragmentation (hereafter ‘fragmentation’) and altered fire regimes are important threats to biodiversity, but their interactions have not been systematically evaluated across the globe. In this comprehensive synthesis, including 162 papers which provided 274 cases, we offer a framework for understanding how fire interacts with fragmentation. Fire and fragmentation interact in three main ways: (i) fire influences fragmentation (59% of 274 cases), where fire either destroys and fragments habitat or creates and connects habitat; (ii) fragmentation influences fire (25% of cases) where, after habitat is reduced in area and fragmented, fire in the landscape is subsequently altered because people suppress or ignite fires, or there is increased edge flammability or increased obstruction to fire spread; and (iii) where the two do not influence each other, but fire interacts with fragmentation to affect responses like species richness, abundance and extinction risk (16% of cases). Where fire and fragmentation do influence each other, feedback loops are possible that can lead to ecosystem conversion (e.g. forest to grassland). This is a well-documented threat in the tropics but with potential also to be important elsewhere. Fire interacts with fragmentation through scale-specific mechanisms: fire creates edges and drives edge effects; fire alters patch quality; and fire alters landscape-scale connectivity. We found only 12 cases in which studies reported the four essential strata for testing a full interaction, which were fragmented and unfragmented landscapes that both span contrasting fire histories, such as recently burnt and long unburnt vegetation. Simulation and empirical studies show that fire and fragmentation can interact synergistically, multiplicatively, antagonistically or additively. These cases highlight a key reason why understanding interactions is so important: when fire and fragmentation act together they can cause local extinctions, even when their separate effects are neutral. Whether fire–fragmentation interactions benefit or disadvantage species is often determined by the species' preferred successional stage. Adding fire to landscapes generally benefits early-successional plant and animal species, whereas it is detrimental to late-successional species. However, when fire interacts with fragmentation, the direction of effect of fire on a species could be reversed from the effect expected by successional preferences. Adding fire to fragmented landscapes can be detrimental for species that would normally co-exist with fire, because species may no longer be able to disperse to their preferred successional stage. Further, animals may be attracted to particular successional stages leading to unexpected responses to fragmentation, such as higher abundance in more isolated unburnt patches. Growing human populations and increasing resource consumption suggest that fragmentation trends will worsen over coming years. Combined with increasing alteration of fire regimes due to climate change and human-caused ignitions, interactions of fire with fragmentation are likely to become more common. Our new framework paves the way for developing a better understanding of how fire interacts with fragmentation, and for conserving biodiversity in the face of these emerging challenges.