退耕还林对地面蜘蛛种群的影响

为探究退耕还林对地面蜘蛛群落的影响,分别于2014和2015年3月—9月期间,采用陷阱法对北京市顺义区南彩镇退耕还林已2a和3a的林带及相邻原非作物生境林带中地面蜘蛛的活动密度进行了系统调查和分析。结果,2014年在调查区域共采集地面蜘蛛1465头,隶属8科18属32种,2015年共收集地面蜘蛛2186头,隶属10科25属45种;退耕还林以后蜘蛛类群发生改变,地面蜘蛛丰富度增加,而部分农田蜘蛛消失;2014年原非作物生境林带中地面蜘蛛的多样性指数、丰富度都极显著高于退耕还林林带(P0.01),均匀性指数不存在显著差异,2015年两个林带的多样性指数仍存在极显著差异(P0.01),丰富度存在显著差异(P0.05),均匀性指数之间不存在显著差异;退耕还林以后第3年新建林带和原非作物生境林带中地面蜘蛛的活动密度随时间的变化趋势相近。研究结果表明:顺义地区退耕还林工程实施3a以后,新建人工林仍处于生境重建阶段,未完全达到稳定状态,退耕还林以后第3年新建林带中地面蜘蛛群落的稳定性高于第2年。退耕还林通过改变原有农田生态系统的植被种类、结构、人为管理等方式,使原有农田生态系统发生了根本性的改变。持续研究退耕还林对地面蜘蛛的类群变化的影响对生境受到干扰后生物群落变化过程的认识有理论意义。

Effects of returning farmland to forests on a ground-dwelling spider (Araneae) community

The spatial extent of plantation forests continued to increase after the Grain for Green Project (GGP) started in January 2002 in China, with more than 20 thousand km² forests developed from 1999 to 2008 throughout the entire country. From 2012 to 2014, the purpose of Beijing''s plain reforestation project was to increase the spatial extent of the forest area in the administrative sub-units that make up the city of Beijing with a plains habitat. In the GGP, one third of the farmland in this region has been replanted with trees to increase the extent of the green area and improve the environment. However, considerable controversy remains related to whether afforestation can effectively result in the conservation of biological diversity. The objective of this study is to explore the effects of afforestation on the ground-dwelling spider community and evaluate the effects of the GGP on the ecosystem and biodiversity during afforestation. From March to September 2014 and 2015, pitfall traps were used to collect ground-dwelling spiders every 10 days in habitats that had been returned to forests from farmland for 2 and 3 years, respectively, in Shunyi District, Beijing. Ground-dwelling spider communities were compared between two adjacent habitats, a former non-crop habitat and an afforested habitat. A total of 18 pitfall traps were placed in the same randomly selected pattern in both habitats. During the investigations, we collected a total of 1465 individuals from eight families, 18 genera and 32 species in 2014, and a total of 2186 individuals from 10 families, 25 genera and 45 species in 2015. Afforestation within the study sites had a positive effect on ground-dwelling spider diversity over the first 3 years. The species of ground-dwelling spiders present changed with afforestation; total species richness increased and some of the farmland spiders were not found in afforested habitats. In 2014, species richness and a diversity index of ground-dwelling spiders in former non-crop habitats were significantly higher than in afforested habitats (P < 0.01). In 2015, the diversity index in former non-crop habitats was still significantly higher than in afforested habitats (P < 0.01), while species richness in former non-crop habitats was significantly higher than in afforested habitats (P < 0.05). An evenness index in the two habitats was not significantly different in both 2014 and 2015. In the second year after afforestation, the peak of the ground-dwelling spider activity density in former non-crop habitats occurred in mid-June, which was 1 month earlier than that in the afforested habitat. In the third year after afforestation, the ground-dwelling spider activity density exhibited similar trends in both habitats; that is, in both habitats the peak of activity density occurred at the same time in early July. The results show that in the first years of habitat alteration, the ground-dwelling spider community in the afforested habitat was still in a stage of community reconstruction, and the community''s stability increased year by year. Returning farmland to forests influenced the original farmland ecosystem through changes in the vegetation type, structure and management practices. As the forests mature, additional effects on spider species at the site are expected because of changes in light conditions, microclimate, vegetation and so on. Therefore, the effects of returning farmland to forests on the ground-dwelling spider community will need further study over time. The aim of this study is to determine whether afforestation contributed to enhancing biodiversity and conservation. Studying the process of change in biological communities after habitat alteration is of great theoretical significance.