| Sandy Grassland is the important land resource in Arid and semi-arid regions innorthern China and its serious degradation and desertification has become the vitalecological environment problem in northern China. At present, exclosure is one of thesignificant measures in dealing with the restoration and reconstruction of soil andplant of degraded sandy grassland. The survey of exclosure effects on soil and plantsystem is not only the element task to exactly estimate the desertification status andthe degree of reverse of the region but also has the extensive application value andguiding significance in applying the economic and effective exclosure methods.Through the alternation study in different measures on plant characteristics ofbiological diversity and structural component biomass and soil physicochemicalproperties of soil moisture, soil nutrient, soil organic carbon and nitrogen stores ofsandy grassland of Gansu Jingtai oasis edge, the research gets hold of the responsemechanism between the sandy grassland plant and soil restoration and the exclosuremeasure which has provided the scientific basis for China’s western ecologicalenvironment construction and restoration. The study result show:1. The effects of exclosure on species composition and diversity characteristicsof plant community of sandy grassland are extraordinary.Desert plant species haveincreased from nine kinds in mobile sandy grassland to18kinds in19-year-oldexclosure (19-year-old artificial restoration). After the application of natural exclosureplus artificial exclosure, the dominant species in sandy grassland are mainly artificialshrub species such as caragana microphylla and hedysarum solarium. Although thespecies richness is inferior to that cultivated by natural exclosure and short-termartificial nurture, artificial shrub species presents perfect growing status and stands ina dominant position. The total trend of species diversity characteristics is:19-year-oldexclosure (19-year-old artificial restoration)>19-year-old exclosure (5-year-oldartificial restoration)>10-year-old exclosure (natural restoration)> mobile sand.2. The average index of height, density, canopy and coverage of plant underdifferent exclosure management measure has an obvious difference (P<0.05). Theindex all show as:19-year-old exclosure (19-year-old artificial restoration)>19-year-old exclosure (5-year-old artificial restoration)>10-year-old exclosure(natural restoration)>mobile sand. Through multiple comparisons in different slopepositions, the results show that the plant average height, average density, averagecanopy and average coverage in sandy grassland are more likely to be influenced bythe slope positions than mobile sand(P<0.05).3. The total biomass of sand community increased with exclosure lasting. Theorder of total biomass under different exclosure management is:19-year-old exclosure (19-year-old artificial restoration)(94.41g/m~2)>19-year-old exclosure (5-year-oldartificial restoration)(60.08g/m~2)>10-year-old exclosure (natural restoration)(58.22g/m~2)> mobile sand (33.75g/m~2). But long time exclosure (19-year-old exclosure and19-year-old artificial restoration) that can’t change the contribution rate of flowers,stems, leaves and the root to the whole plant. However, the flowers, stems, leaves andthe root modular of suffurticosa plant change the whole composition of the wholeplant. In general, root shoot ratio in exclosure sample plot is smaller than that ofmobile sand. The ratio order of most plant modular with aboveground biomass is:stems> leaves> flowers> root, and the ratio list of plant modular with individualbiomass is: leaves> stems> flowers> root.4. The exclosure measure can significantly improve soil physical properties ofsandy grassland. Compared with mobile sand, with the rise of years of exclosure, thesand content is significantly reduced, the content of clay particle increase dramatically.Soil bulk density tends to decrease, total soil porosity and maximum moisture contentare both increase obviously. The10cm depth of soil water content of three exclosuresandy grasslands lower than mobile sand. The order of soil water storage is: mobilesand>19-year-old exclosure (5-year-old artificial restoration)>10-year-old exclosure(natural restoration)>19-year-old exclosure (19-year-old artificial restoration).Through the comparisons of different slope positions, the result shows that soilphysical properties in exclosure sandy land is more likely to be influenced by theslope positions than mobile sandy(P<0.05).5. The SOC and N P K nutrient have a significant regression directed by sandygrassland exclosure, it can promote sand soil property developed. Compared withmobile sand,19-year-old exclosure (19-year-old artificial restoration) sandy grassland(0~20cm), SOC、total N and total P and total K increase380.0%,238.9%,75.0%and59.6%, respectively. Soil physicochemical properties in exclosure sandy grassland isinfluenced by slopes positions obviously. However, the characteristics of the mobilesandy have a tiny influence by the slop positions (P<0.05). Exclosure sandy grasslandSOC, total N and total P and total K and available nutrient content increase greatlyfrom upper slop positions to foot slop positions. However, the mobile sandy doesn’tpresent an obvious tendency.6. After the application of natural exclosure and artificial exclosure, in sandygrassland0~40cm, light fraction and the total content of carbon and nitrogen, unitarea of organic carbon and the content of total nitrogen increased greatly(P<0.05).The proportion of soil light fraction orgnic carbon or nitrogen with totalorgnic carbon or nitrogen, the exclosure sandy grassland is higher than the mobilesand. Compared with mobile sand, natural exclosure and artificial restoration can botheffectively reduce HFOC/SOC. In general, in0~20cm， HFOC/SOC basically demonstrates that exclosure sandy land is higher than mobile sand. However, theHFOC/SOC and LFOC/SOC change opponently.7. The correlation analysis of plant characteristics and soil physicochemicalproperties show, the index of Margalef, Shannon-Wiener, Pielou and Simpsona havepositive correlation with SOC, LFOC, available nitrogen and soil moisture content,and they have a negative correlation with available phosphorus, soil bulk density andsand. The above ground biomass, underground biomass and the content of litter fall indifferent exclosure sandy grassland have a positive correlation with SOC, total N,LFOC, LFN and HFOC（P<0.01）, however, they have a negative correlation with soilwater storage and sand content(P<0.01).The rise of the SOC and total N in exclosuresandy grassland have a significantly positive correlation with the rise of soil clayparticle content (P<0.01), but it has a significantly negative correlation with thedecrease of the content of sand (P<0.01).The content of SOC and total N and total Khas a significantly positive correlation (P<0.01). Meanwhile, the content of SOC, totalN and total K have an significantly positive correlation with the average height ofplant, the average cnopy and total biomass characteristics (P<0.01) and （P<0.05）,respectively. The characteristics of soil bulk density and the content of sand have anobvious negative correlation with the average height of plant, the average canopy, andtotal biomass.8. The effects and improved degree of the measure of natural exclosure andartificial restoration in sandy grassland are higher than that of pure natural exclosure.After the measure of exclosure and afforestation and replanting, a mutual effectbenign recycling system between plant and soil are being formed in sandy grasslandof oasis edge. The mesures can promote the deteriorated grasslands favorableevolution, and have energetic action in desertification reversed. |
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