黄河下游农业景观中景观结构和生境特征对林表生蜘蛛多样性的影响

以捕食者来进行"自上而下"的生物防治是有效而经济的。蜘蛛作为农业景观中重要的捕食者,在不同的尺度上研究景观和环境要素对其多样性的影响是十分必要的。目前,有关黄河下游农业景观研究中,关于蜘蛛多样性的研究报道较少。针对黄河下游农业景观中林地生境的蜘蛛多样性展开研究,于2014年4月和7月采用陷阱法调查林地生境中蜘蛛种群的分布及其多样性,分析了对蜘蛛多样性影响最强烈的环境因子,以及不同蜘蛛种群对草本植被盖度的不同选择。结果发现:研究区林地生境内蜘蛛的优势种群为星豹蛛(Pardosa astrigena)、单带希托蛛(Hitobia unifascigera)、类水狼蛛(Pirata piratoides)和陕西近狂蛛(Drassyllus shaanxiensis)。不同尺度上的景观要素和环境要素(解释变量)对蜘蛛多样性的影响存在差异,且在不同的季节均为100 m尺度上的解释变量对蜘蛛多样性的影响最大。在100 m尺度上,不同的解释变量对蜘蛛多样性的影响也不同,春季林地中的植被盖度对其影响最大,路距和林地面积也有较为明显的影响,夏季林地中的植被高度和植被盖度对其影响最大,其余解释变量的影响则极小。不同的蜘蛛种群对草本植被盖度大小的偏好不同,多数蜘蛛偏好高的植被盖度,如星豹蛛和白纹舞蛛(Alopecosa albostriata)等,也有部分蜘蛛种群偏好中、低植被盖度,如赫氏花蟹蛛(Xysticus hedini Schenkel)、白斑猎蛛(Evarcha albaria)和皮雄红螯蛛(Araneae)。研究表明,黄河下游农业景观林地生境中,不同的景观要素和环境要素在不同尺度和不同季节上对蜘蛛多样性的影响具有显著的差异,草本植被对蜘蛛多样性的影响极为显著。因此在研究区内合理规划林地的建设,加强草本植被的保护,提高林地捕食者的数量,有助于生物防治工作的发展和生物多样性保护工作的进行。

Effects of landscape structure and habitat characteristics on spider diversity in the agro-landscape along the lower reaches of the Yellow River

Top-down control from predators on herbivores provides an effective and economic means of control in the agricultural landscape. Research into which factor, in areas at different scales, has the strongest effect on spider diversity is beneficial to facilitate increasing the diversity of spiders. In most regions, spider diversity shows a declining trend, the reasons behind which are not fully explained by available data. As a result, many researchers have focused on the protection of the biodiversity, however, in our study area, the agro-landscape along the lower reaches of the Yellow River, the current level of protection is inadequate. We therefore set samples in the woodland habitat in our study area and, by comparing the effect of different factors (landscape and environment variables) on the spider diversity in different scales (100, 200, 350, 500 m), we tried to identify which factor in which scale had the most important effect on the spider diversity in the study area. Spider abundance was selected because of its strong correlation (P < 0.05) with the number of species and then data (i.e. the number of specimens that caught) were ln transformed. In order to compare and rank the factors, we selected the lowest Akaike Information Criteria values using the step AIC function within the MASS package in the R program. Owing to the small sample sizes, we used AICc instead of AIC, and to measure the influence of each variable in every model, we also calculation the Akaike Weights (W_i). To characterize the species of spider in relation to the three groups of herb coverage, an indicator species analysis was undertaken using the IndVal function in the Labdsv package in R. The results showed that the dominant spider species in the study area were Pardosa astrigena, Hitobia unifascigera, Pirata piratoides and Drassyllus shaanxiensis. A different effect existed between factors and spider diversity in different scales, but the best scale to study factor effect on spider diversity was 100 m. In spring, the most important factor influencing spider diversity was herb coverage, followed by crop area, woodland area and distance from road. In summer, only herb coverage and herb height had an obvious influence. Through IndVal value analysis, we found that different species of spider had different tendencies to herb coverage, but the most of the spider species preferred high herb overage, especially the spiders in Lycosidae family. However, a few spider species, such as Xysticus hedini Schenkel, Evarcha albaria, Achaearanea asiatica and Araneae, were more frequently appear in woodland with Medium or Low herb coverage. According to the indicator species analysis, some spider species also had a relatively high indicator value (>0.2), which was associated with High herb coverage. Examples of such species are Pardosa astrigena, Hitobia unifascigera. This study demonstrates that herb is the most important of the factors tested with respect to spider diversity. Therefore, increasing herb cover in the agricultural landscape would contribute to an increase in the number of predatory arthropod and improve the abundance of predatory arthropod conducive to the protection of biodiversity in the agricultural landscape and the controlling of biological pests in the terrestrial ecosystem.