Investigating The Diversity Of Herbaceous Plants In Agricultural Landscapes Of Nanning,Guangxi

Although agricultural lands hold a small fraction of the biodiversity of natural ecosystems,their sheer size and proximity to remain natural habitats make them an important target for biodiversity conservation.Non-crop areas,including remnant natural habitats and field margins,clearly increase biodiversity in agricultural areas,but the importance of cropland heterogeneity(particularly the number of crop types)is more controversial.Greater knowledge is also needed about agroecosystems in tropical biodiverse areas where there are more,smaller-scale farms.We laid out a network of 73 sites in an agricultural area of 50 km2 near Nanning,Guangxi Province;here rice and sugarcane are the major crops,but we encountered a total of 45 less dominant kinds of crops.At each site we measured the diversity of herbaceous plants in four to six 1m2 plots during two summers(2016-2017),relating the plant biodiversity,and the percentage of non-native and animal-dispersed species to the extent of agricultural cover,length of field margins and crop heterogeneity measured within a 100 m-radius area(local scale),and another measure of agricultural cover within a 500 m-radius area(landscape scale).We found that agricultural cover at the local scale was associated with lower Shannon-Wiener diversity of herbaceous plants and a lower percentage of animal-dispersed species in both years,and a lower percentage of native species in one year.The length of field margins had the opposite pattern:margins were related with increasing diversity in both years and an increasing percentage of animal-dispersed species in one year.Crop heterogeneity showed a mixed pattern:it was associated with increased diversity in one year,but in both years it was linked with a decreased percentage of animal-dispersed species and non-native species.Our results confirm that the protection of field margins is as important for herbaceous plant biodiversity in this tropical landscape as it is elsewhere.Crop heterogeneity in our site,however,may increase farmers' disturbance to agroecosystems,at the same time as providing more niches for herbaceous plants to persist.