| This paper,in accordance with the GIS technology in combination with the findings ofground survey,the vegetation landscape elements pattern characteristics,the distributingcharacteristics of the vegetation landscape patch size,the patch shape indices,landscapediversity index,fragmentation degree,and so forth of Xiannangou watershed that was justmanaged in recent years and Zhifanggou watershed that was managed for more than 30 yearswere analyzed.The growth,updating,biodiversity,soil nutrition and water and environmentfactors and so on of the typical eco-system were analyzed and evaluated.The aim offered thescientifical foundation for the landscape pattern's sensible distribution and watershedenvironment construction.The main results were as following:(1)The landscape pattern is similar basically in two watersheds:Through more thanthirty years management,the vegetation eco-system pattern in Zhifanggou watershed isrelatively reasonable,and the proportion of eco-protection forest and grassland is higher thanother landscape types.The area of forest and grassland come to 5.647 km~2 with 68.24 % ofZhifanggou watershed.the perimeter of eco-protection forest and grassland come to 172.54km with 62.67 % of Zhifanggou watershed.The proportion of forest and grassland is alsohigher than other types in Xiannangou watershed,the other landscape parameter were justsimilar with Zhifanggou watershed.The total area of shrub,farmland,orchard,and so on wasrelatively small,with lower than 40 percent of the whole Xiannangou watershed.The patchnumber of different landscape types was very disproportion.There is no obvious regularbetween different landscape types in the term of the number of patches,the proportion ofpatches,the density of patches,and the difference of the different landscape type index wasvery significance.(2)The landscape diversity indices of Zhifanggou watershed were higher thanXiannangou watershed,but the dominance degree in Zhifanggou watershed was lower than inXiannangou watershed.And the fragmentation index in Zhifanggou watershed is higher thanin Xiannangou watershed as a whole.With the increase of eco-economic health index andlandscape diversity index,the fragmentation index will increase in the mean time,accordingto the comparing of landscape diversity index and eco-economic system health index. (3)The analysis of the four typical eco-system stabilities showed:Hippophae rhamnoidecould renew very well in Hilly-gully region of Loess plateau.The number of youth and adultswas large on half-sunny,half-cloudy slope and cloudy slope,which showed that thispopulation was a developing one,and could survival in the future.There were higherbiodiversity and better moisture and nutrition in soil in this population on the half-sunny andhalf-cloudy slope which provided a guarantee for community stabilizing gradually.ThePopulus simonii population renew difficultly in Hilly-gully region of Loess plateau.The resultof research on different habitats showed that this population could not renew at sunny slope.Compare with in the sunny slope,there were growing well Populus simonii,several seedlingsappeared higher biodiversity and better soil nutrient content in the cloudy slope.But thesecould not change the declining trend of the whole population.Sophora davidii can renew wellin half-sunny slope and sunny slope,the individual number of middle aged were many,Sophora davidii population in Hilly-gully region of Loess plateau was a developing one,Sophora davidii population could survived for long in different habitat in Hilly-gully regionof Loess plateau.Diversity was high,community was stability more and more,water andnutrition was better in half-sunny slope and sunny slope.Community was more stability.Robinia pseudoacacia population had not renewed seeding in the sunny slope.Robiniapseudoacacia population in loess hilly region was a recession one,that is not stabilitypopulation,would disappear with the development of time in the sunny slope,but was fitterand had the renewed seedlings basically in the half-cloudy slope and gully and valley.Diversity was high in the half-cloudy slope,gully and valley.Water was serious shortage inthe sunny slope,which affect grow of Robinia pseudoacacia.(4)This paper applied the method of the membership function of Fuzzy mathematics toevaluate the typical eco-system stability.The results showed that Hippophae rhamnoide,Populus simonii,Sophora davidii and Robinia pseudoacacia were more stability in thehalf-cloudy slope,cloudy slope,sunny slope and gully and valley respectively.The rationality of landscape pattern was a relative conception.Through conservation forabout 30 years,eco-system had already entered basically positive cycle stage in Zhifanggouwatershed,the vegetation landscape layout had been reasonable comparatively,the areaproportion of the eco-protection forest,shrub and grassland landscape had got to the historicalmaximum level,the area proportion of the pro-economics farmland and orchard landscapeand the living-service river,dam,settlement landscape were suitable for the population andsocial development,might take it as the important reference of the vegetation conservation inHilly-gully region of loess plateau.But the partial landscape layout also existed unreasonableaspects,for example,artificial forests (Robinia pseudacacia,Populus simonii) existed"dried earth layers"and"lower-yields stands",artificial grassland (Medicago sativa) existed"theperiodicity declines"and so on,would need adjust landscape pattern and made itconsummation unceasingly in the future.
|
PDF Full Text Request