The Landscape Pattern And Dynamics In Zhifanggou Watershed In Hilly-Gully Region Of Loess Plateau, Ansai

Based on widely investigation of the condition of social-economic and natural environment in Zhifanggou watershed , depended on the topographic map in proportion 1:7500, the vegetation landscape patch mosaic map was drawn practically in 2005 . the vegetation landscape patch mosaic maps of 1982, 1990 and 2005 were transformed into electronical vegetation map after digitizing processing , analyzed the landscape elements pattern characteristics in Zhifanggou watershed in different conservation stage,supported by applied Geographical Information Systems arc/info,Arcview3.2a , evolvement process and relative regulation of the landscape patch element scale,patch element shape,diversity and fragmentation were studied systemically in Zhifanggou watershed in recent 25 years . The main results were as following:1)The landscape elements were divided into three types, eco-protection type,pro-economics type and living-service type by ecological function in watershed. analyzed the vegetation landscape elements in different stage, The results showed that:the main types were eco-protection grassland landscape and pro-economics farmland landscape which accounted for 73.631% of the total area in 1982; the main types were eco-protection grassland and shrub landscape which accouned for 62.780% of the total area in 1990; the main types were eco-protection grassland and forest landscape which accounted for 68.242% of the total area in 2005. In different conservation stage, there were 8 eco-protection vegetation landscape, Robinia pseudacacia,Caragana microphlla,Sophora viciifolia,Hippophae rhamnoides,Bothriochloa ischcemum,Artemisia giraldii+ Stipa bungeana- Stipa bungeana,Artemisia giraldii+ Stipa bungeana- Bothriochloa ischcemum,Artemisia giraldii+ Stipa bungeana+Stipa przewalskyi took up high proportion of the total area and were major vegetation landscape in Zhifanggou watershed2)From 1982 , the area proportion of eco-protection forest,shrub and grassland landscape had increased gradually, whereas the area proportion of pro-economics farmland and orchard landscape had decreased gradually, the area proportion of living-service river,dam and settlement landscape had been remained stable at about 1.5% in Zhifanggou watershed, The eco-protection vegetation landscape ,Artemisia giraldii+ Stipa bungeana- Stipa bungeana, Robinia pseudacacia,Caragana microphlla had been advantage status throughout; The patch element shape of pro-economics farmland and orchard landscape were regular comparatively, the patch element shape of eco-protection forest,shrub and grassland landscape were complex comparatively;the patch element shape were complex comparatively and the fragmentation degree were high comparatively in 1990.The diversity indices,evenness indices and fragmentation indices of the vegetation landscape elements increased after decreased ,but dominance indices decreased after increased in Zhifanggou watershed .The fragmentation degree were high in 1990,were low comparatively in 2005;In eight eco-protection vegetation landscape, The fragmentation degree of Sophora viciifolia and Hippophae rhamnoides were high,Artemisia giraldii+Stipa bungeana- Stipa bungeana were low comparatively.3)Through conservation for about 30 years,by 2005,ecosystem have already entered basically positive cycle stage in ZhiFanggou watershed, the vegetation landscape layout has been reasonable comparatively, the area proportion of the eco-protection forest,shrub and grassland landscape have get to the historical maximum level , the area proportion of the pro-economics farmland and orchard landscape and the living-service river,dam,settlement landscape are suitable for the population and social development,might take it as the important reference of the vegetation conservation in hilly-gully region of loess plateau.But the partial landscape layout also exists unreasonable aspects, for example , artificial forests (Robinia pseudacacia,Populus simonii) exist"dried earth layers"and"lower-yields stands", artificial grassland(Medicago sativa) exists"the periodicity declines"and so on ,will need adjust landscape pattern and make it consummate unceasingly in the future.