| Agro-landscape is the main type of landscape in the Northeast Plain,China.With the development of agricultural mechanization,maize had achieved large-scale cultivation in the Northeast Plain,China.However,due to this planting method,the agro-landscape here has become homogenized,leading to the decline of biodiversity and the loss of ecosystem services.Our current study on plant diversity of agro-landscapes take more attention in the North China Plain,and lack of attention in the Northeast Plain,China.We study the structural characteristics of plant communities on the landscape level in this region,that results will provide theoretical basis and data supporting for the father research on animal diversity of agro-landscapes and construction of sustainable agro-landscape.In order to explore the relationship between plant species diversity and heterogeneity of agricultural landscape,and furthermore,to probe the suitable proportion of non-cropped habitats in agricultural landscape,we investigated plant diversity in Changtu County in the Northeast Plain,China.We created fishnet in ArcGIS to transform geographic data in Changtu County to be grid(1 km×1 km).A total of 20 sampling plots(1 km × 1 km)were selected for area proportions 0–50% of non-cropped habitats,and were divided into five groups according to area proportion of non-cropped habitats,which were 0–10%,10%–20%,20%–30%,30%–40% and 40%–50%.The plant species in non-cropped habitats were investigated using the Braun-Blanquet method.The surveyed non-cropped habitats included woodland,grassland,ditch,orchard and field road.We identified family,genus and species of plants sampled in 20 sampling plots by automatic plant identification method.The heterogeneity indexes of agricultural landscape with different proportions of non-cropper habitats were extracted by Fragstats 4.2.Used Excel to calculate the plant species Shannon-Wiener,richness and evenness indexes and to analyzed composition of plant species and flora features in 20 sampling plots.We analyzed characteristics of landscape heterogeneity and plant species diversity in 20 sampling plots and their correlation by the tool of combining Excel with SPSS16.0.The results are as follows:1.In the study area,129 species,belonging to 35 families and 91 genus,were recorded.Asteraceae,Gramineae,Polygonaceae,and Leguminosae are the dominant families.The plants are predominantly cosmopolitan(25 families,116 species)and pantropic(6 families,8species)types,accounting for 88.57% of the total families and 96.12% of the total species.The genus show complex patterns of geographical distribution type,comprising 11 of the 15 distribution types of Chinese seed plants.The cosmopolitan(25 genus,48 species),pantropic(20 genus,25 species),north temperate(18 genus,31 species)and temperate Eurasia are the dominant distribution types(78.02% of all genera and 82.95% of all species).Although florafeatures have significant differences in different habitats,the study area is dominated by the widespread species generally.2.The Shannon diversity index,Shannon evenness index of agricultural landscape increased with increasing of area proportion of non-cropped habitats,while landscape contagion metrics showed contrary tendency,indicating that lower area proportion of non-cropped habitats induced higher landscape dominance.Plant species diversity and evenness of agricultural landscapes gradually increased initially and later decreased with increasing area proportion of non-cropped habitats.Peak plant species diversity and evenness were in landscapes with 20%–30% area of non-cropped habitats.Meanwhile,plant species richness gradually increased initially when area proportion of non-cropped habitats was0–30%,decreased later when area proportion of non-cropped habitats was 30%–40% and increased finally when area proportion of non-cropped habitats was 40%–50%.However,plant species richness was obvious variation when area proportion of non-cropped habitats was 40%–50%,its peak was in agricultural landscape with 40%–50% area of non-cropped habitats.Thus the optimum area proportion of non-cropped habitats was 20%–30% within agricultural landscapes in typical maize planting areas in the Northeast Plains,China.3.The composition of dominant plant species in different non-cropped habitats was similar,but their dominant degree,ecological function and service function were different.The plants are predominantly Gramineae and Asteraceae in study area,but the species in different non-cropped habitats were different.Lolium multiflorum and Artemisia scoparia Waldst.et Kit.were dominant species in woodland and field road.Lolium multiflorum and Artemisia lancea Van were dominant species in grassland.Poa pseudo-palustris and Artemisia scoparia Waldst.et Kit.were dominant species in orchard.Lolium multiflorum and Beckmannia syzigachne(Steud)Fern were dominant species in ditch.The order of dominant degree of dominant species was orchard,ditch,grassland,field road and woodland.Meanwhile,the dominant degree of dominant species in orchard,ditch and grassland were significantly higher than those in woodland and field road.4.The correlation between landscape heterogeneity and species diversity decreased from grassland to orchard,ditch,field road and to woodland.The correlation between species Shannon diversity richness indexes and landscape heterogeneity was significant in grassland,but it was insignificant in other non-cropped habitats.Different non-cropped habitats disturbances resulted in different correlation coefficients between landscape heterogeneity and plant species diversity.5.Woodland and ditch had a positive effect on conservation of species diversity.However the effect on conservation of species diversity was relatively small in grassland,orchard and field road.Species Shannon diversity and evenness in orchard,grassland and ditch weresignificantly higher than those in woodland and field road.Species richness(from high to low)was grassland,woodland,ditch,orchard and field road.There were obvious variation in plant community diversity among orchards,grasslands and ditches. |
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