Edge Effects Of Farmland Interface On Predatory Natural Enemies And Their Responses To Alfalfa Mowing In Different Farmland Patch Structures

To uncover Space-time dynamic distribution of species diversity and dominant species population of the ground-dwelling beetle and spider on wheat lands in different landscape structures of farmland, to provide a theoretical practical basis and method for the wheat production and pest population control. According to the survey, We simulated the field and time dynamic distribution of the carabid beetles and spiders on the wheat ground under the different landscape structures using the species diversity index. Taking the wheat-alfalfa and wheat-wheat interfaces as a model system, a sampling point was set by the method of pitfall trapping in the wheat field at the distance of3m,6m,9m,12m,15m,18m,21m,24m, and27m from the interface. The species composition and abundance of ground beetles and spiders captured in pitfalls were discussed in this study.l.there were totally amount of5683beetles and spiders including17families and92species in the Yinchuan plain ground, in which the number of the spider and carabid beetle were respectively account for15.61%and31.15%. We simulated the field and time dynamic distribution of the carabid beetles and spiders on the wheat ground under the different landscape structures using the species diversity index, and then draw the conclusion that the district of the investigation which has a more complicated landscape structure have more species diversities than that of other area in which has simple biological species diversity. The time dynamic distribution form indicated that in early may, the index of the carabid beetle’s diversity is high, and later appears the trend of the down first and up second. Whereas, the spiders’diversity index seems high in late June and later it is down lasting. It is mainly caused by the affection of the activities of the Beetles and spiders on the ground by Irrigation. We can see clearly from the population density of the field distribution about Chlaenius pallipes and Pardosa astrigera that the population numbers in the survey area of Complex landscape structure are much more than that of Simple landscape structure.2.(1) To some extent there were an edge effect on species diversity and abundance of ground beetles and spiders along the two interfaces. Along alfalfa-wheat interface in the wheat field, there was an marked edge effect between15m and18m, however no edge effect was found at the distance of over20m. There was an weaker edge effect along the wheat-wheat interface in comparison to alfalfa-wheat interface.(2) The alfalfa mowing management cause a migration of a large number of ground beetles and spiders to adjacent wheat filed. During ten days since mowing, both species number and abundance of ground beetles and spiders increased within20m in wheat filed along alfalfa-wheat interface, where the abundance was pronounced more than species number.(3)The spatial distribution of species diversity of ground beetles and spiders, together with population density of the dominant Chlaenius pallipes and Pardosa astrigera, were clearly observed, which directly indicated migrating process of natural enemy from alfalfa to wheat field.3.It is more the important way of crop cultivation system for intercropping mode,interplanting mode and neighborhood mode. The biodiversity of community and environment of many crop cultivation system was more complex than monoculture system, It can avoid large outbreaks of pests.Through the investigation, the results showed:(1) The stability of community of predatory in wheat near alfalfa is better than wheat far away from near alfalfa, at0m relative, It was the highest for the abundance,diversity and evenness of community of Predatory at the distance of0m from the interface. It was lowest at27m.(2) The stability of ground beetles from wheat-wheat interface is lower than alfalfa-wheat interface in the wheat field.By the difference analysis:It is no significant for the differences of the species evenness and diversity of ground beetle beween wheat-wheat interface and alfalfa-wheat interface in the wheat field.It showed that population of ground beetle is similar under two planting pattern in the fields of wheat. However, It was significant for the differences of the species evenness and diversity of spiders beween wheat-wheat interface and alfalfa-wheat interface in the wheat field.It showed that population of spiders is different under two planting pattern in the fields of wheat.These studies can provide new ideas and methods for pest population control.