Effects Of Semi-natural Habitat Heterogeneity And Rice Field Heterogeneity On Spider Diversity

Farmland biodiversity and its ecosystem services,such as biological control and pollination,are the basis of sustainable agricultural development.rice fields have a high degree of biodiversity due to their alternating dry and wet conditions and the main regional tropical distribution;Rice field is the main food source and plays an important role in agriculture.Many studies on agricultural landscape mainly focus on the drylands and wheat fields in Europe and the United States and Northern China.At present,there are few studies on rice field landscape.Therefore,it is necessary to study the impact mechanism of rice field landscape heterogeneity on biodiversity.Whether China’s fragmented farmland landscape conforms to the conclusion that reducing farmland area is conducive to farmland biodiversity in European and American countries is not clear.Semi-natural habitats(such as hedgerow,permanent grassland and fallow farmland)can provide habitat and food sources.The increase of rice field heterogeneity is conducive to structural heterogeneity.This study predicts that semi natural habitat heterogeneity and rice field heterogeneity have a positive impact on biodiversity,but there is no final conclusion about the impact of semi natural habitat heterogeneity and rice field heterogeneity on biodiversity.Based on this,in this study spiders were sampled and landscape patterns were investigated in 34 rice fields in Ranyi Town,Chengdu.Spider sampling was carried out in the landscape center by using the Surface trap cup method and Vacuum-suction method.The obtained spiders were classified and identified,and the spider species diversity index was calculated.The landscape survey was conducted by UAV to obtain the landscape data,and then the semi-natural habitat heterogeneity index and rice field heterogeneity index were calculated.The effects of semi-natural habitat heterogeneity and paddy field heterogeneity on spider diversity were analyzed,and the key landscape factors and scales affecting spider diversity were identified.The effects of semi-natural habitat heterogeneity and paddy field heterogeneity on spider diversity in paddy field landscape were further discussed.The main results are as follows:(1)At a landscape scale with a 200-400 m radius centered on the sampling point,the higher the proportion of semi-natural habitat,the higher the diversity of net-forming spiders,especially Ummeliata insecticeps;The proportion of semi-natural habitat was positively correlated with Shannon index.However,the proportion of semi-natural habitat had positive effects on Pirata subpiraticus and the individuals of adults of Linyphiidae.The number of semi-natural habitat types in the range of 200-400 was positively correlated with the Surface trap cup method,active hunting spiders,total Shannon index and large spiders.The proportion of nursery had a positive effect on Ummeliata insecticeps and Pirata subpiraticus.Forestland had positive effects on the adults of Ummeliata insecticeps,Pirata subpiraticus and the adults of Linyphiidae.Therefore,in rice fields in the landscape,therefore,should also increase or retain existing half proportion of natural habitats,increase forest land,nursery plants such as structure rich half natural habitat types and their ratio,ensure that every field around half a natural habitat patches,can effectively promote the different functional groups and common spider populations and the whole maintenance and conservation of spider community diversity.(2)The mean area of rice field and the Chao-1 index of active hunting spiders increased linearly at different scales,and the most significant was at the small scale of 100 m,that is,the greater the mean area of rice field,the higher the diversity of active hunting spiders.There was a significant positive correlation between the individuals of common species of spiders in rice fields,for example,the individual numbers of Trochosa ruricoloides and larvae of the family of Clubionidae.At the 100-500 m scale,the total length of the ridge was positively correlated with the diversity of weaving spiders.At the 250-500 m scale,the total length of the ditch was negatively correlated with active hunting spiders.The heterogeneity of rice fields had an important effect on the diversity of spiders,and the diversity of multi-functional groups and common spiders could be improved by properly merging the over-fragmented fields,increasing the area and ridge length of individual rice fields,and avoiding over-hardening and deep ditches.(3)At 100 m and 400 m scales,the semi-natural habitat heterogeneity mainly affected the hunting type,followed by weaving spiders;In the semi-natural habitat heterogeneity,the proportion of nurseries had the greatest influence on the diversity of active hunting spiders and the Surface trap cup method,and provided rich food resources,shade and shelter for spiders.The heterogeneity of rice field mainly affected active hunting spider.Larger rice fields can increase the habitat range of spider species,increase population numbers and avoid excessive human disturbance.The heterogeneity of semi-natural habitat and rice field affected active hunting spiders,followed by weaving spiders.Among them,the proportion of semi-natural habitat,the mean area of rice field and the proportion of barren grassland contributed the most.The higher the proportion of semi-natural habitat was,the larger the mean area of rice field was,and the lower the proportion of barren grass and ridge with low vegetation coverage was,the better the spider diversity was.The results showed that semi-natural habitat heterogeneity had an important impact on spider diversity in farmland,and it was particularly important to preserve and improve the proportion of semi-natural habitat at a large scale of 400 m.Heterogeneity also had a significant effect.The greater the mean area of rice field,the higher the diversity of spiders in rice field.Policy and the construction of agricultural landscape of land arrangement in context,We propose to maintain the current proportion of semi-natural habitat at large scale,increase the area of farmland by properly merging farmland plots at small scale,build a landscape composed of large farmland rice fields and surrounding semi-natural habitat,and promote the restoration and protection of farmland biodiversity.