GIS Park

Site type classification is the necessary and basic work in the process of vegetation restoration. For better restoring vegetation and planting trees on the suitable sites condition in Agriculture and Pasturage Interlaced Zone of Northern Shaanxi, Site type classification must be carried out, each site type area and distribution characteristics must be understood and difficulty degree of reforestation must be divided, thus realizing the scientific planning for reforestation. So far, site type classification in Agriculture and Pasturage Interlaced Zone of Northern Shaanxi based on GIS has not been reported. The study adopts the quantification theoryⅠcombining with the GIS technology, taking Zhouwan town and Changcheng town of Wuqi County in northern Shaanxi for example, based on investigating vegetation biomass in six counties(Wuqi, Zhidan, Jingbian, Hengshan, Yuyang, Shenmu)of Agriculture and Pasturage Interlaced Zone of Northern Shaanxi, carries on the site type classification taking water content as the main factor, obtains the site type distribution map and analyzes the area and distribution of each site type, at the same time, establishes the suitable tree species for each site type and puts afforestation technology model forward. The main conclusions of the study are as follows:(1) Vegetation shows strongly man-made characteristic in Agriculture and Pasturage Interlaced Zone of Northern Shaanxi. From the southeast to the northwest, vegetation shows a transition from forest-grassland to arid grassland, desert grassland. Soil is mainly loess and Aeolian sandy soil. The arbor species are mainly Populus hopeiensis, Populus simonii, Robinia pseudoacacia, Pinus tabulaeformis, Salix matsudana, Pyrus betulaefolia, Prunes armeniaca, Ulmus pumila, Morus alba, Pyrus pyrifolia, Malus prunifolia, Thuja orientalis, Juglans regia, Zizyphus jujube, etc. The shrub species are mainly Hippophae rhamnoides, Caragana microphylla, Amorpha fruticosa, Tamarix chinensis, Salix psammophila, Prunus davidiana, Xanthoceras sorbifolia, etc. The biomass is mainly affected by water, reducing as the site condition deteriorates.(2) The water content is the predominant factor in restricting the survival rate in the study area. According to the water content, the site types are divided into five ranks: superior, good, medium, passing, bad. The quantification theoryⅠindicates that the factor affecting the soil water is: the aspect>the slope position>the slope. The water content can be intuitively shown by the terrain factors. The site types are classified into 18 kinds, corresponding to different site type ranks.(3) According to the statistical result, the superior site type area is 113.47 hm2 in the northeast of Wuqi County, accounting for 27.92% of the total area. The part is easy to restore vegetations, mainly concentrating in the bottom and the shade-gentle area, which has good quality and suits to develop economic forest, farmland protection forest and timber forest. The suitable trees are Populus Simonii,Salix matsudana,Malus prunifolia,Ulmus pumila, etc. The good site type area is 99.06 hm2, accounting for 24.37% of the total area. The part can be restored, mainly concentrating in the downhill, which is suitable to develop water conservation forest and fuelwood forest. The suitable trees are Thuja orientalis,Ulmus pumila,Pinus tabulaeformis,Robinia pseudoacacia, etc. The medium site type area is 109.15 hm2, accounting for 26.86% of the total area. The part is difficult to restore vegetations where can be planted Pinus tabulaeformis,Robinia pseudoacacia, etc. The passing site type area is 84.76 hm2, accounting for 20.85% of the total area. The part is advised to plant Hippophae rhamnoides and Caragana microphylla for lacking water heavily.(4) The technology flow of planting trees on the suitable sites condition in the study, which takes water content as the main factor, adopts the quantification theoryⅠas theoretical basis of site type quantitative segmentation and takes site factors auto-computation based on DEM and forest resource inventory data as the condition, provides the foundation for site type automated classification and decision support system of planting trees on the suitable sites condition.