| The Loess Plateau of Our country is a soil erosion region and is one of the most serious regions in the world, after the reform opens, in order to resolve the depravation of environment quality, the slow-developing economy and the poor problem of local crowd by root, our nature have established 11 experimental demonstration areas in various areas on the Loess Plateau and carried on research and want to resolve environment and development problem in rare special view area. After 20 years of management and practice, whether these small watersheds carried out the expectation targets of the nation or not? For this, this paper with the Gaoquan small watershed of DingXi county, the Zhifang small watershed of AnSai county and the Nihe small watershed of ChunHua county as research objects, with the land use and its evaluation as the breakthrough to answer above-mentioned questions, and to provide a reference to the water and soil conservation of the Loess Plateau and ecosystem environment management.In the Chap 2 analyzed the varieties of the land use changes of the 3 small watersheds after conservation implementation, the main conclusion are:①In this 3 small watersheds, on upland, the farmland areas decreased, woodland and lawn areas increased; in the gully-slope land, all of the slope farmland have abandoned, woodland and lawn areas increased significantly; In the channel bottom ground, the farmland areas increased a little. From the efficiency of land use, the efficiencies of this three land types all get a certain increase.②After conservation implementation, the total changes of land use of this three small watershed is: In Nihe, the woodland areas decline after increase, the farmland areas rise after declining, lawn and others has been descending. In Zhifang, the farmland areas descend, woodland, lawn and others increase. In Gaoquan, the farmland and the lawn areas have a small increased, the woodland areas increase quickly, the other descends quickly. Total up, the change trends of land use in the three small watersheds: the farmland decreased, woodland, lawn, resident ground and road increased, the waste land decreased.In the Chap 3 mainly studied the results which caused by land use structure adjustment in 3 small watersheds. The main conclusions are:①The structure adjustment of land use should carried on gradually according to the district natural and social economic condition; secondly, the space design of the land ecosystem is needed; thirdly, carry on water and soil conservation decision, carry out water and soil conservation project, reduce the erosion risk of land exploitation; finally, improve and establish land ecosystems.②Under the trends that the farmland area lets up, the food total yield of the small watershed and personally food can acquire a significant exaltation through exaltation food outputs per unit, In addition, after structure adjustment of the land exploitation, the agricultural total production value, personal production value, personal pure value and personal habitation areas of the 3 small watersheds all raise significantly, the average erosion mold of the small watershed lets up significantly.③in the Nihe small watershed, wood and fruit industry is the predominant industry and "wood-fruit ecological agriculture" is the developing mode; in Zhifang, wood is the predominant industry, while plants industry and fruit industry develop appropriately and "the ecosystem agriculture of the water and soil conservation type" is the developing mode; in Gaoquan, special crop industry, grass and domestic half feed is the predominant in agriculture industrial structure. At the same time, form "the half dry area of the Loess Plateau's rehabilitation of vegetation, grass and domestic animal and special features farm crop industrial turn efficiently an ecosystem agriculture" developing mode which is base on rehabilitation of vegetation ,ecosystem environment construction and high efficiency use of natural precipitation.④The land use structure index (SI) of the Nihe, the Zhifang and the Gaoquan are 0.3083, 0.3514 and 0.2435, respectively. According to the influence of land use structure upon the soil erosion, the kind of land use structure in the Zhifang small watershed have the minimum influence upon the soil erosion and is best to keep Water and soil.In the Chap 4 computational methods and distribution characteristics of LNPI of various typical land parcels are researched and obtaining as follows as results:①taking the land type as basic map and according to the land use type, slope and soil type, each small watershed can get the representative and typical plots.②The soil organic matter, soil bulk density, slope of ground, etc.11 land ecological factors can reflect the natural productivity condition of land.③Adopted evaluation model of land natural productivity can better metered reflect production potential of land, principal component analysis and factor analysis method can more objectively settle the power of each factor in the model, the adoption of the revises membership grade can compute a grade of ecosystem factor in each land and each value has a better distinction.④The whole characteristics of the land natural productivity in this three small watersheds are: in the Nihe small watershed, the LNPI sequence of various typical land parcels is woodland>lawn>orchand land>farmland; in Zhifang the LNPI sequence is highwood> orchand land >farmland>bush wood>natural lawn> abandoned land, in Gaoquan the sequence of LNPI is highwood and shrub mixed forest land>shrubbery land >highwood>farmland> native grass land >cultivated lawn>abandonment of arable land.⑤The distributed characteristics of the land natural productivity in these three small watersheds is: in the Nihe small watershed, the LNPI sequence of upland is woodland>orchard land>farmland, the LNPI sequence of gully-slope land is woodland>lawn> orchard land >farmland, the LNPI sequence of channel land is woodland>lawn>farmland. In Zhifang all LNPI sequences of upland, gully-slope land and channel land are woodland is the maximum, farmland is in the center and the lawn is minimum. In Gaoquan, the LNPI sequence of terrace is the lawn higher than the farmland; the LNPI of upland and woodland are the maximum, farmland secondly, the lawn is the minimum; in channel land, the LNPI of farmland is higher than the woodland. Among all of the different land use, the LNPI of slope woodland is the maximum.⑥On the whole, among agriculture land, wood land and grass land, the Gaoquan have the maximum LNPI, the Nihe is the center, and the Zhifang is the minimum.In the chap 5, we analyzed the economic productivity characteristics of the various typical land parcels of the three small watersheds, the main conclusions are as followed:①form the whole characters of the land economic productivity (kg/hm2·a) of the small watersheds, can give these results: in the Nihe small watershed: wood land>orchard land >farm land>pasture. In Zhifang small watershed: farm land>orchard land>native grass land >shrubbery land>Highwood land>abandoned land, in Gaoquan small watershed: farm land>shrubbery land>shrubbery and Highwood mixed land>wild grass ground>Highwood land>cultivated pasture>abandonment of arable land。②the characters of the land economic productivity of the three small watersheds on the spatial distribution had these rules: in Nihe small watershed: orchard land>farm land>wood land in upland, wood land>orchard land and grass land>farm land in gully-slope land, wood land>grass land>farmland in channel ground; in Zhifang small watershed: farm land>wood land>grassland in upland, farm land>grass land>wood land in gully-slope land, farm land>wood land in channel ground; in Gaoquan small watershed: farm land>grass land in the terrace, farm land>wood land>grass land in upland, farm land>wood land in the bottam of valley;③under the different land use types in the 3 small watesheds, the characteristic of the land economic productivity of typical land parcel are as follow:Nihe>Zhifang>Gaoquang on the farm land economic productivity, Nihe > Gaoquan > Zhifang on the wood land economic productivity, Gaoquan>Nihe>Zhifang on the grass land economic productivity.In chap 6,we analyses coupling characters of land productivity of typical land parcels of the three small watersheds, and the conclusions are as followed:①the analysis of coupling characters of land productivity of typical land parcels of the small watersheds, should not only due to the types of the land, but also due to the land use types.②In the farm land of Nihe small watershed, the coupling efficient of part of the typical land parcel is lower, the factors are climate,density,seed time,variety,geographic location, and the time of cultivated crop of the land can also deeply effect the land productivity of land parcels. In wood land, the coupling efficient was effected by the culture density,man-made damage,the different between trees and geographic location, the proper planting density of Robinia pseudoacacia in this small watershed is 1.5m×2.0m,and the proper planting density of Fiji and Qinguan is 2.0m×3.0m and 3.0m×3.0m,respectively. The orchard land should be changed into farm land beside the gully, or ecology wood should be cultured to weaken the effect ion caused by bad climate. In grass land, the differences between soil structures of the land parcels are the main factor that affects the coupling efficient.③In Zhifang small watershed, the improper planting density is the main reason that caused the low coupling efficient of the high wood land, In this small watershed, the culture density of the high wood having a higher biomass most is 4m×5m, in Highwood and shrubbery land, choose improper shrub breeds is the main factor. In shrubbery land, high culture density causing water deficit that kill the plant, this is the main factor, in this small watershed, the proper density of the shrubbery land is 1.0m×1.5m. In farm land, the degenerate of the variety,the neglect of plant disease and insect pest,and the short of field management, these are the main factors. In grass land, especially abandoned grass land, the low survival rate is the main factor that caused low economic productivity, In the wood land of Gaoquan small watershed, the improper culture density of the trees is the main reason, in farmland the difference between the variety ,especially between the potatoes is the main factor. And the culture density of the potatoes can affect the economic productivity deeply.④t he productivity coupling characters of the farm,wood and grass land in the three small watersheds are as followed: In Gaoquan small watershed, the coupling efficient of farm land is lower; the deficit of the precipitation is its main factor. The three small watersheds both have a better coupling efficient in grass land; while in Nihe small watershed people take more attention to orchard land profoundly, and have achieved encouraging economic, ecological and social results. Nihe small watershed had a lower coupling efficient in grass land, it should learn the good experience on the develop of grass land and animal agriculture from Gaoquan small watershed...
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