沙生植物害虫-天敌对荒漠景观破碎化的响应及尺度效应研究

Landscape changes affecting biodiversity has aroused wide attention. The relationship between plant, pest insects and natural enemies is a research hotspot that it responded to the landscape complexity, landscape fragmentation and landscape scale. In this scheme we take the region of natural and semi-natural desert sandbreak and desert grassland as experimental fields in Ningxia, northwest of China. Using the principles and methods of entomology, geographic information systems and landscape ecology, we investigate and study effects of habitat fragmentation on psammophytes, pest insects and their natural enemies interaction. This study was designed to address three subjects. First, from fine scale to coarse scale of landscape, we investigate the data of abundance and spatial distribution of psammophytes, pest insects and their natural enemies, which revealed population viability analysis and effects landscape structure and patches areas for dynamics of pest insects and their natural enemies. Second, on base of the trophic rank between psammophytes, pest insects and their natural enemies, minimum areas of suitable habitat of natural enemies, sampling scale effect on pest insects and their natural enemies, we explore influencing mechanism of landscape scale and habitat factors on population abundance of pest insects and their natural enemies at fine scale. Third, using spatial statistical methods and landscape models, the small -scale spatial patterns information and landscape pattern-process of desert are combined to explore the impact of spatial and temporal coupling of psammophytes, pest insects and their natural enemies interaction variation. Based on this information, scaling up can be carried. Aim of this study is to reveal the mechanism of habitat fragmentation and landscape complexity on population dynamics of psammophytes, pest insects and their natural enemies, effective control of pest outbreak during recovering and rebuilding processes of sandbreak and desert ecosystems.

景观变化对生物多样性的影响国内外十分关注，植物-害虫-天敌三级营养层对景观复杂性、景观破碎化、景观尺度的响应等是研究热点之一。本项目以宁夏中部自然半自然的荒漠生态系统为试验区，以沙生植物害虫及其寄生性天敌为研究对象，应用昆虫学、地理信息系统、景观生态学等原理和方法，研究生境破碎化对沙生植物害虫-寄生性天敌种群动态、种群生存力的影响；在小尺度不同生境界面斑块下研究沙生植物-害虫-天敌营养关系、天敌最小生存面积、取样尺度对沙生植物害虫-天敌的影响，揭示其对景观尺度、生境因子的生态响应机制；通过小尺度空间格局实验所获得的信息与景观格局、过程相联系，进行大尺度推绎，探讨沙生植物-害虫-寄生性天敌互作的时空耦合变异，阐明其对生境破碎化的响应机制及互作协同控制害虫的行为机制，为在不同尺度下进行荒漠沙生植被的恢复与重建、进行病虫害早期预测和预报，有效控制沙生植物害虫大发生提供新的途径。

生境破碎化、景观变化对生物多样性的影响国内外十分关注，植物-害虫-天敌三级营养层对景观破碎化、景观空间格局的响应是研究热点问题之一。本项目以宁夏灵武白芨滩国家级自然保护区及其周边的自然半自然荒漠生态系统为试验区，研究了生境破碎化、景观格局、取样尺度等对柠条、苦豆子、沙冬青等荒漠沙生植物种子害虫及其寄生性天敌群落结构、营养层、最小适生面积、空间分布格局等方面的影响。结果显示：（1）在小尺度斑块格局下，斑块面积对沙生植物种子害虫数量及危害率影响不显著，但生境破碎化使种子害虫的数量及危害率增加，其寄生性天敌的物种丰富度和群落多样性降低；斑块连接越紧密越有利于种子害虫的扩散；内缘比小、形状规则、边缘效应小的斑块在一定程度能够减轻种子害虫的危害。（2）从营养级方面的研究显示虽然斑块面积与沙生植物的生物量相关性不显著，但斑块面积减小使第二营养级的沙生植物种子害虫的发生量有增加的趋势，使第三营养级天敌的数量有减少的趋势；最小适生面积的大小与营养位的高低有关，寄生性天敌通常较其寄主更易受生境面积的影响，最小适生面积更大。（3）沙生植物种子害虫在空间分布上具有较为明显的边缘正效应，寄生性天敌与种子害虫在空间上存在相关性，下行控制效应明显。（4）沙生植物种子害虫的为害率与取样尺度呈典型的正相关关系，具有明显的尺度效应；寄生性天敌多样性也具有尺度效应，但达到一定取样面积后多样性趋于稳定。该研究结果可以为在荒漠沙生植被的恢复与重建过程中沙生植物斑块的合理配比，进而有效控制沙生植物害虫的发生提供理论数据，为沙化区生态环境建设和绿色防控有害昆虫的发生具有一定的理论参考价值和实际应用前景。