西双版纳大卡老寨农地景观格局变化

农地景观比自然景观更具有变异性 ,它既受到自然环境的制约 ,又受到人类活动和社会经济条件的影响和干预。大范围地区农耕生态系统的景观格局一直都是景观生态学研究热点之一[1～ 4 ] ,然而村级水平的景观格局的研究报道则不多见[5] 。本文以西双版纳热带山区大卡老寨为例 ,对农地景观的格局及其变化进行了初步调查与分析。1　材料与研究方法1.1　自然概况大卡老寨是隶属勐腊县勐仑镇大卡办事处的一个爱尼族村寨 ,地处Ｎ2 1°4 1′ ,Ｅ10 1°2 5′ ,距勐仑镇8ｋｍ ,距勐仑自然保护区 10ｋｍ。年平均气温2 1 5℃ ,≥ 10℃积温为 7811℃ ,年降…     

基于机器学习方法的景观斑块属性对物种丰富度的影响研究

景观破碎化对物种的影响依赖于斑块属性,斑块属性体现了斑块的类型、面积、形状及其与周围斑块间关系。然而,在破碎化农业景观中这些斑块属性对关键物种的联合影响仍知之甚少。选取中国海南地区的典型农业破碎化景观,实测了180个斑块中三类关键物种,分别为害虫-橡胶材小蠹虫(Xyleborus affinis)、传粉昆虫-中华蜜蜂(Apis cerana)和天敌物种-玉米螟赤眼蜂(Trichogrammatid ostriniae Pang et Chen),刻画了各斑块属性,包括斑块类型、斑块面积、形状指数、距天然林距离、是否与橡胶接触、景观中天然林所占比例、是否有林下植物,并使用3种机器学习模型(神经网络、随机森林、支持向量机)拟合斑块属性与三类物种丰富度关系,解析斑块属性的相对重要性。结果表明,与支持向量机和神经网络相比,随机森林模型对三个物种的丰富度预测效果均最好,其R²在橡胶材小蠹虫、中华蜜蜂和赤眼蜂中分别达到0.785、0.845和0.798;基于随机森林模型的结果表明,斑块类型对橡胶材小蠹虫和中华蜜蜂丰富度相对重要性高于其他斑块属性;斑块面积对赤眼蜂丰富度影响高于其他斑块属性,且与斑块类型存在交互作用;橡胶林中橡胶材小蠹虫与中华蜜蜂丰富度高于天然林和其他斑块类型,玉米螟赤眼蜂丰富度则在天然林与农田中最高。研究揭示了斑块属性对不同物种丰富度的相对影响,阐明了斑块类型在不同物种中的重要作用,并证实了机器学习是推导斑块属性对物种影响的有效方法。     

景观物种的理论与实践

结合保护生物学和景观生态学的理论发展起来的景观物种的理论,为更有效地保护物种及其生境开拓了新的视角。本文就景观物种的概念及其相关理论作一初步的介绍,并概括了对其实施保护的具体步骤。     

南京地区美丽乡村植物景观的物种丰富度及其群落特征

为了探究南京地区美丽乡村植物景观的物种丰富度及其群落特征,实地踏查了南京地区42个美丽乡村,对1 013个样地的绿地类型、植物种类和植物生长状况进行记录;运用R语言对数据进行量化分析,并构造独立系数探究不同绿地类型间的独立程度。结果表明：（1）南京地区美丽乡村植物景观的物种丰富度较高,调查记录的维管植物共计139科438属667种,主要属于广布型（41科）、泛热带型科（36科）和北温带型（24科）植物,植物群落物种生活型结构为金字塔形,乔木种数（111）<灌木种数（136）<草本种数（357）;(2)不同乡村的植物群落存在明显差异,平均Jaccard距离为0.76,平均S?rensen距离为0.61;(3)不同绿地的植物群落存在明显差异,平均Jaccard距离为0.55,平均相互独立系数为0.22;(4)存在的风险主要为外来植物的入侵风险和野生植物的无序生长问题,对此应该予以重视。     

乌云界国家级自然保护区蝴蝶物种多样性及其保护

2008年6月至2010年9月采用路线法对湖南乌云界国家级自然保护区蝴蝶物种多样性进行了调查,针对4条调查路线31个样线段的植被物种丰富度、海拔高度、离水源距离和人为干扰程度等影响蝴蝶物种丰富度的主要因子,开展多元回归分析比较,同时对试验区、缓冲区和核心区3个规划区域进行蝴蝶群落多样性分析和相似度比较.共采集记录到蝴蝶147种,隶属于10科94属,其中国家保护种4种;多元回归分析表明,植被物种丰富度、海拔高度和人为干扰程度是影响蝴蝶分布最主要的3个因子,其中植被物种丰富度与蝴蝶物种丰富度存在极显著正相关（P<0.01）,海拔高度和人为干扰程度与蝴蝶物种丰富度存在显著负相关（P<0.05）;核心区的蝴蝶物种丰富度、多样性指数均高于缓冲区和试验区,试验区的优势度指数较高;缓冲区与核心区的相似度系数较高,达到0.526.该自然保护区蝴蝶物种多样性的保护重点在于保护植物群落多样性,保持林相之间的自然演替,适当减少人为干扰,以及加强特殊蝴蝶生境的维护.     

青海湖流域典型草地物种丰富度与生产力的关系

通过2009-2010年青海湖流域的样地实测数据,研究了不同尺度物种丰富度与生产力的关系,并初步探讨了其形成机制.结果表明:青海湖流域典型草地物种丰富度与生产力的关系在小尺度上(群落内和群落间)表现为线性正相关、负相关,在大尺度上(区域)则以单峰相关为主.沼泽草甸和高寒草甸的物种丰富度随生产力的增加而降低,高寒草原和温性草原的物种丰富度随生产力的增加而增加.在整个研究区内则表现为单峰型相关.研究还表明,研究区群落生产力的变化范围为65～585 g·m-2·a-1,物种丰富度为2～9种;生产力从高到低的顺序为沼泽草甸＞高寒草甸＞高寒草原＞温性草原.     

西双版纳种子植物物种多样性的垂直格局及机制

物种多样性海拔分布格局及其形成机制的研究是生物地理学和宏观生态学的重要议题之一。本文利用西双版纳植物专著资料, 结合高分辨率的地形和气候等数据, 探讨了面积、边界限制和现代气候对西双版纳野生种子植物物种丰富度及物种密度海拔分布格局的影响。结果表明: (1)物种丰富度呈单峰分布格局, 面积(81.9%)、边界限制(17.5%)和气候(60.0-69.3%)都不同程度地解释了物种丰富度的单峰格局; (2)利用幂函数种-面积关系计算的物种密度沿海拔大致呈减小的分布趋势, 气候的解释率降低为32.6-40.6%, 与边界限制无显著相关关系; (3)利用等面积高度带划分得到的物种密度沿海拔呈单峰变化趋势, 物种密度与边界限制无显著相关性, 但气候对物种密度的解释率为81.6-89.9%。研究结果有助于准确全面地理解物种多样性的海拔分布格局及其成因机制, 为西双版纳生物多样性保护提供理论支撑和实践指导。     

民族民间医药与农业生物多样性保护——以西双版纳大卡老寨为例

运用户级农业生物多样性的评估方法 ,以西双版纳大卡老寨为例 ,随机抽取 1 2户农户进行庭院样方和 2户典型样方调查 ,并对关键人物访谈 ,进行民族医药与生物多样性保护的关系研究。结果表明 :1 民族医药对农业生物多样性保护具有促进作用 ;2 传统医药知识正在大量流失 ,值得重视 ;3 市场收购对当地物种具有不良影响。提出相应的对策为 :1 加强民族民间医药的整理工作 ;2 加强对农户的培训 ,传承传统知识 ;3 制定合理的经济发展措施 ,保证民族经济的协调发展 ;4 利用庭院进行稀有、濒危药用植物的保护     

高寒草甸不同草地群落物种多样性与生产力关系研究

生态系统的结构和功能、生物多样性与生产力的关系问题是近年来群落生态学中研究的中心问题,其中,生态系统生产力水平是其功能的重要表现形式,用4种不同草地类型探讨自然群落的物种多样性与生产力关系.结果表明,矮嵩草草甸、小嵩草草甸和金露梅灌丛群落中物种多样性与生产力的关系呈线性增加关系,藏嵩草沼泽化草甸群落中线性增加关系不显著,这表明群落生产力除受物种多样性的影响外,也受物种本身特征和环境资源的影响.不同的环境资源和环境异质性是形成群落结构特征、物种多样性分布格局差异的主要原因之一.     

The relationships between net primary productivity, human population density and species conservation

Aim In this study, I determine the relationships between net primary productivity (NPP), human population density, species richness and land use. I also examine the implications of human settlement patterns for species conservation. Location Australia. Methods I document the associations between NPP, human population density and the species richness of birds, butterflies and mammals using correlations and spatial regressions. I also assess changes in land‐use with NPP and population density, focussing particularly on protected areas. An initial exploration into the implications of the NPP‐population density relationship for regional conservation strategies is provided. Results Human population density increases with NPP suggesting that available energy may be a key driving force of human settlement patterns. The species richness of each taxonomic group and geographically restricted species also increases with NPP leading to substantial overlap between species diversity and populated regions. The percentage of land designated as minimal use decreases considerably with increasing human population density and NPP, while intensive agriculture is confined entirely to areas of high NPP. There are strong negative relationships between the size of Australia's National Parks and human population density and NPP. Small parks are often surrounded by relatively dense settlements, but have high average NPP, while large parks are mostly isolated and characterized by low productivity. There are no areas in the highest quartile of NPP that also occur in the most sparsely populated regions, presenting challenges for conservation strategies wanting to protect productive areas under the least threat of human development. Main conclusions Human population density and species richness respond similarly to variation in NPP, leading to spatial congruence between human settlements and productive, species rich regions. Planning strategies are required that minimize the potential threat posed by human development to diverse ecosystems and maximize the underlying productivity of protected areas. Reducing the level of threat may require stabilizing the size of the human population, while capturing larger areas of relatively high productivity in the conservation reserve system would lead to greater protection of local diversity.     

Floral species richness,structural diversity and conservation value of vanilla agroecosystems in Madagascar

Agricultural landscapes provide financial livelihoods for farming communities in rural areas. However, such agroenvironments can significantly impact the local floral biodiversity and introduce harmful invasive species to the ecosystem. Despite the prominence of plantations throughout the tropics, their effects on local flora are limited to only a few specific cash crops and geographical regions. Here, we compared the species richness and structural diversity of vegetation in natural forest fragments and three types of vanilla plantation within the Sava region of north-east Madagascar ranging from those within or adjacent to existing forests, to intensively cultivated plantations. We recorded data on plant species abundance, diameter at breast height and canopy cover within multiple sites of each habitat. We used abundance data to calculate species richness indices, and we compared these metrics between habitats. Forested habitats contained a significantly higher floral species richness, structural diversity and more endemic and regionally native species than nonforested, anthropogenic vanilla plantations. However, our results suggest that the high floral species richness and structural diversity of natural forests can be partially achieved in vanilla plantations, depending on the site's management regime; traditionally managed vanilla plantations located close to natural forests can support diverse floral communities. These encouraging findings for plant conservation and sustainable agroforestry in Madagascar suggest that that newly created vanilla plantations and already existing nonforested plantations should endeavour to follow the more traditional forested approach to enhance the future sustainability and promote floristic diversity.     

Relationship between grass species richness and ecosystem stability in Kruger National Park, South Africa

The relationship between grass species richness and ecosystem stability was investigated in the Kruger National Park. A total of 135 489 individual grasses were identified from 189 sites spread across 19 485 km² of savanna biome, making this one of the largest studies of its kind. At each site, grass percentage abundance and standing crop were measured at one year intervals to provide an index of ecosystem function. A severe drought that affected the region between 1991 and 1993 provided a convenient perturbation. At the height of the drought, mean species richness declined by 12.7% while standing crop declined by 38.1%, from 3199 to 1979 kg ha^?1. Percentage grass abundance declined to 87.5% of its pre‐drought value. After the drought had passed species richness, standing crop and percentage abundance recovered to 92.1%, 113.8% and 92.8% of their pre‐perturbation values, respectively. Statistical analysis of these responses revealed that grass assemblages of low species richness were more resistant to drought than assemblages of high species richness. Species‐poor sites also showed better recovery from perturbation after the drought had passed. These findings suggest that ecosystem stability may be negatively related to grass species richness in South African savanna grasslands.     

Habitat fragmentation and species richness

In a recent article in this journal, Fahrig (2013, Journal of Biogeography, 40 , 1649–1663) concludes that variation in species richness among sampling sites can be explained by the amount of habitat in the ‘local landscape’ around the sites, while the spatial configuration of habitat within the landscape makes little difference. This conclusion may be valid for small spatial scales and when the total amount of habitat is large, but modelling and empirical studies demonstrate adverse demographic consequences of fragmentation when there is little habitat across large areas. Fragmentation effects are best tested with studies on individual species rather than on communities, as the latter typically consist of species with dissimilar habitat requirements. The total amount of habitat and the degree of fragmentation tend to be correlated, which poses another challenge for empirical studies. I conclude that fragmentation poses an extra threat to biodiversity, in addition to the threat posed by loss of habitat area.     

Geographical patterns and determinants of species richness in Mexico across selected families of vascular plants: implications for conservation

Mexico is considered a megadiverse country containing more than 10% of the world's biodiversity. The distribution of this species richness and endemism is different among the different Mexican states. We examined the species richness patterns of 13 families of vascular plants (including ferns, gymnosperms and angiosperms) in Mexico using political divisions (states) as units of analysis. We analysed the species richness values (absolute richness, endemic richness and restrictive richness) of these plant families using stepwise multiple regression analysis, assessing their relationship with a set of 10 environmental variables (expressed as heterogeneity coefficients). A combined cluster analysis with multidimensional scaling analysis (MDS) and an analysis of similarities were also undertaken to define the spatial–geographical patterns. Additionally, we proposed a methodological strategy to determine which states of Mexico have priorities for conservation. Our results suggested that the three species richness values used were significantly predicted by environmental factors, especially by climatic heterogeneity. Notwithstanding that a linear pattern was recognized, the Mexican states were gathered in four groups, which were confirmed by the MDS and the cluster analysis: (1) the Yucatan Peninsula, (2) arid Mexico, (3) the Mexican Transition Zone and (4) the megadiverse states. We proposed that 12 Mexican states include all the environmental conditions and are candidates for developing conservation programmes: (1) Quintana Roo, Tabasco and Yucatán, (2) Baja California, Chihuahua and Sinaloa, (3) Guerrero, Jalisco and Nuevo León and (4) Chiapas, Oaxaca and Veracruz.     

基于焦点物种的北京市生物保护安全格局规划

快速城市化进程中,城市及周边地区生物栖息地的丧失和破碎化对生物多样性保护构成严重威胁。如何在景观尺度上判别对于生物保护具有重要意义的栖息地及其空间格局成为了重要问题。选取快速城市化的典型地区——北京市作为研究对象,将焦点物种和景观安全格局方法相结合,对北京市生物保护安全格局进行判别和规划。根据焦点物种的定义和选取标准,将在栖息地类型、生物学特征等各方面具有代表性的大白鹭(Casmerodius albus)、绿头鸭(Anas platyrhynchos)、环颈雉(Phasianus colchicus)选作北京市的焦点物种,应用最小阻力模型和GIS空间分析技术,对焦点物种的栖息地适宜性进行分析,并建立物种运动的等阻力面,根据阻力面的空间特征对北京市生物保护安全格局进行规划。结果显示:规划后的安全格局的斑块数量、分离度、邻近距离显著下降,平均斑块面积和最大斑块指数显著上升;该格局用约60%的土地,保护了北京市主要生境类型及关键性空间格局,可有效缓解栖息地丧失和破碎化的问题,从而达到保护整体生物多样性的目的。这一研究方法和成果可为北京市生物多样性保护和城乡生态建设提供决策依据,也对同类研究具有借鉴价值。