Spatial distribution and dynamic characteristics of the grassland vegetation in Hebei.

Open-air survey data from 110 plots and 330 quadrats(not including output examination spots) obtained from a Hebei grassland survey from 2005 to 2007 and a grassland survey of Hebei materials from 1979 to 1984,were used to investigate the grassland vegetation coverage,height,production,and vegetation fluctuation.Grassland vegetation quantitative fluctuation and its fluctuation ratio between 2005 and 2007 were calculated,and rangeland types,area and their spatial distribution in Hebei province were rearranged.According to the Chinese Grassland Classification System initiated by the Committee of Systematic Grassland Surveys,Hebei rangeland was divided into seven types: Temperate steppe,temperate meadow-steppe,mountain meadow,warm temperate tussock,warm temperate shrub-grassland,lowland meadow,and marsh grassland.Based on the differences of topography,soil,climate and vegetation characteristics,the spatial distribution of Hebei rangeland was divided into three districts.The Bashang plateau region accounted for 29.7% of the area of the whole rangeland,with a rangeland area of 1.41×106 ha,containing temperate steppe,temperate meadow-steppe and mountain meadow distributing in this region.In mountain and hilly areas,the total area of all three rangeland types,mountain meadow,warm temperate tussock and warm temperate shrub-grassland,was 3.3×106 ha,accounting for 69.3% of the area of the whole Hebei rangeland.The rangeland area of the littoral plain was 0.05×106 ha,accounting for 1% of the whole Hebei rangeland with two grassland types in this region: Lowland meadow and marsh grassland.Grassland production(hay output) of warm temperate shrub-grassland reached 5 133.35 kg/hm2 and was the highest of all the steppe types.It was followed by warm temperate tussock(4 182.22 kg/hm2),mountain meadow(in Bashang plateau district,3 268.35 kg/hm2),temperate meadow-steppe(2 665.94 kg/hm2),mountain meadow(in mountain and hilly areas,2 111.55 kg/hm2),lowland meadow(1 872.44 kg/hm2),and temperate steppe(1 103.29 kg/hm2).The order of vegetation coverage(%) of different steppe types was mountain meadow(in Bashang plateau district,93.97%)mountain meadow(in mountain and hilly areas,82.60%)lowland meadow(82.26%)warm temperate shrub-grassland(79.70%)warm temperate tussock(76.91%)temperate meadow-steppe(71.59%)temperate steppe(57.63%).The order of vegetation height of different steppe types appeared as warm temperate tussock(49.25 cm)warm temperate shrub-grassland(34.18 cm)mountain meadow(in Bashang plateau district,28.88 cm)temperate meadow-steppe(26.22 cm)mountain meadow(in mountain and hilly areas,21.98 cm)temperate steppe(19.77 cm)lowland meadow(18.77 cm).The quantitative fluctuation of the grassland vegetation was positive in 2005,2006,and 2007,but that in 2007 was negative and the fluctuation ratio lower than compared with 2005,suggesting the worst vegetation growth was in 2007.Among the steppes types,the vegetation fluctuation ratio of warm temperate tussock was the highest and that of temperate meadow-steppe was the lowest with the ratios of other steppe types between the two.