Vegetation Characteristics And Regional Distribution Of Grassland Types In Northern Liaohe River Plain

The grassland resources of Liaoning Province are mainly distributed in the long and narrow belts in the north and northwest of the province.This area is an important ecological protection zone in our province and it is also the main area for animal husbandry production,among which there are six national and semi-agricultural and semi-animal husbandry counties.Since the first survey of grassland resources in 1979,no detailed grassland resources surveys have been conducted in our province in the past 40 years.The quantity,quality and spatial distribution of grassland resources are unclear,and there is still no scientific basis for grassland resource ecological construction,planning and utilization.The northeast section of grassland resources in the province extends from the right bank of the Liaohe River in the west of Changtu County and extends westwards to Jianping County.It is a narrow and long strip distribution and borders the grasslands of Inner Mongolia.In order to determine the status of provincial grassland resources,Changtu County,Kangping County,Zhangwu County,and Faku County in the northern part of Liaohe Plain were investigated as the scope of the survey.Through three years of field investigation,the vegetation characteristics of grassland resources were analyzed and the data of grassland were compared with the 1980 s,the evolutionary trend was analyzed,and the evolution mechanism was explored in conjunction with changes in hydrothermal conditions.Using ArcGIS 10.0 software to draw a map of grassland types in 4 counties and analyze the distribution characteristics of grassland.The results show:(1)There were 164 species of plants in the survey area,which belonging to 46 families and 129 genera.According to the characteristics of community structure,the grassland resources in the survey area were divided into three categories: sparse forest grassland class,warm shrub grassland class and lowland grassland class.The species diversity of open sparse forest grassland is the highest,accounting for 71.3 percent of the total species.The sparse forest grassland and warm shrub-grassland are dominated by xeric plants,and there are relatively more wet meadows and aquatic plants in lowland meadows.There are eight grassland types in the three classes of grasslands,two sparse forest grasslands,three warm grass shrubs and three low-lying meadows.Grassland plant communities usually have a three-layered structure of trees and shrubs,and grassland types all have "arbor or tree irrigation",which are obviously different from those of Inner Mongolia.(2)The xenobiotic evolution of grassland plant communities is very obvious in the survey area.Compared with the early 1980 s,the dominant type of grassland type Elymus dahuricus,Arundinella anomala,Achnatherum splendens,Pennisetum alopecuroides,and Triarrhena sacchariflora has basically disappeared.The zonal community of moderate droughts represented by Leymus chinensis is only distributed in the habitats with relatively high hydrothermal conditions,such as under forest,riverside,and dunes lowland.While Cleistogenes squarrosa and Artemisia frigida the dominance of typical xerotic plants such as Artemisia frigida has increased,and the distribution area of xeric plants in typical grasslands has extended eastward.After analyzing the characteristics of climate change,it was found that there was a clear trend of high-temperature drought in the study area.Compared with the early 1980 s,the annual precipitation increased slightly,but the average annual temperature increased by 1°C,daily average ?10°C cumulative temperature increased by 205°C,and the dryness increased to 1.2.Changtu County and Faku County have been transformed from temperate climate zones to warm temperate climate zones.The trend of high-temperature climate and aridity of habitats was obvious.Xenobiotic succession of grassland community is synchronized with the climate aridity trend in the area.(3)In Zhangwu County,65.1 percent of the total grassland in the county was sparse forest grassland class.In Changtu County,54.5 percent of the total grassland was warm shrub grassland class.Kangping and Faku counties were dominated by low-level meadows,which accounting for 52.6 percent and 50.6 percent respectively.There were 11,250 grassland patches in 4 counties,94.4 percent of which were below 10,5.4 percent were between 10 and 100 hectares,and only 0.2 percent were above 100 hectares.Grassland is scattered and habitat fragmentation is serious.