Study On Ecological Restoration Treatments Of Degraded Red Soil In Western Fujian Province

There is a typical south subtropical degraded red soil ecological system in Hetian town,Changting County, Fujian Province. Many domestic ecological workers have studied managementbenefit and management mode since the40th of last century, especially since2000. A lot ofmanagement work has been done through a variety of measures and many effective managementmodes have been formed. This study selected three kinds of management modes with basicconsistent background values, carried out field investigation and laboratory analysis of samples,systematically analyzed and evaluated soil water-stable aggregates (WSA), hydrologycharacteristics of ecological system, soil fertility, community biodiversity, community biomass,element contents of C, N, P, K, Ca and Mg and their stocks of vegetation, predicted the successiontrend of variety of sample plots and put forward future restoration strategies, unrestored region andsecondary forest undisturbed as a reference for comparison. Main conclusions are as follows:(1) In the topsoil (0-20cm), the content of WSA(>0.25mm), the content and stock of soilorganic carbon (SOC) of WSA were low in the untreated land, in general,they increased as thedecreasing of aggregates' size. The difference was small between various size aggregates. Thevegetation restoration had little effect on the cumulative contributing rates of soil organic carbon(SOC) of WSA in soil organic carbon, but significantly (P<0.05) improved the content of WSA,the content and stock of SOC of WSA. The fractal dimension and percentage of aggregatedestruction (PAD0.25) were reduced, the mean weight diameter (MWD) was increased and thewater stability of WSA was improved. The new increased organic carbon promoted theenrichment of large particle size aggregates (＞2mm) from smaller ones. The content of WSA, thecontent and stock of SOC of WSA were variable in the subsoil (20-40cm).(2) After vegetation restoration, the components of the floor litter were changed, the waterholding rate and water absorption speed were improved, the biomass of floor litter was increased,the water holding capacity was further improved, the soil bulk density and the soil crust werereduced, the soil porosity, the permeation rate, the function of soil reservoir and the hydrologiccharacteristics of soil were improved. Different treatment measures had little effect on the ratio ofsoil capillary water holding capacity to soil total water holding capacity.(3) After the recovery of vegetation, the soil nutrient element contents and soil fertilityquality indexes were significantly improved, but the soil pH was slightly decreased. The order ofboth total and available nutrient element contents was: K>N>P under the same treatment. Thecontent of total K was roughly equivalent in both soil layers; other nutrient contents had differentsurface accumulation effect, that was, their surface accumulation quantity increased with theenhancement of content. The stock variety of total N, P and K was similar to each other with thechange of nutrient contents.(4)In the research land, there were vascular plants of34families,66genera and81species.The differentiation grades of families and genera were low, more than half of the family wassingle-species, and nearly2/3of the genera were single-species. Vascular plants were mainlydistributed in the tropic areas, and the temperate area in the next place.The plant density was small, the way of growing was bad, the community structure wassimple, the plant diversity was small and the indexes of Shannon-Wiener and Simpson were lowwithout management. The community structure tended to be complex, interlayer plants appeared,and indexes of Shannon-Wiener and Simpson increased after the ecological reconstruction. In thevertical structure of same community,the order of Pielou even index varied with different treatment measures,while the order of the rest diversity indexes was: community>shrub layer>herb layer>inter plant layer>abor layer as a whole.The indexes of Jaccard and Sorenson betweentreated lands and secondary forest were enhanced, the invading of species was promoted, and thedensity of regeneration seedings was obviously improved. For most of the populations, thedistribution area and niche breadth value (B(sw)i) were narrow, and the values of niche overlap weresmall. The utilization of resources was inadequate, especially in the arbor layer.The species richness of all vertical structure increased under the improvement of soilchemical-physical property,The path analysis showed that the SOC content and available Ncontent were the dominant factors affecting the community species richness and the herb layerspecies richness respectively; the effect of the factors were mainly lay in the direct effect,whilecanopy density and＞0.25mmWSA content,stock of floorlitter and soil capillary porosity wereminor factors affecting the community and the herb layer species richness, the effect of thosefactors mainly lay in the indirect effect.(5)The community biomass and annual biomass of litter fall increased quickly in the treatedland, and it was8.68-12.09,12.23-17.84times that of no treatment respectively. The Pinusmassonian took up the highest ratio in the community. Turnover rate of floor litter decompositiondecreased and the nutrient element circulation were enhanced along with the ecological recovery.As a whole, in the same community, after vegetation restoration, the content of mineral elements(N, P, K, Ca, Mg) and C gradually decreased from the arbor to the herb layer. The mean contentsof mineral elements under treatment were higher than those of no treatment. The stocks of thoseelements were clearly increased in the plant layer, their distribution pattern were similar to thoseof biomass distribution. Among the mineral elements, the stocks of N, K and Ca were the largest.The treatment of degraded land obviously increased both plant and soil carbon stocks ofecosystem. The ratio of plant carbon stock increased quickly with the increasing of biomass whilethe ratio of soil carbon stock decreasing continuously.(6)Soil WSA stability, hydrologic characteristics of ecosystem, soil fertility, stability degreeof community,integrate recovery degree of ecosystem under treatment were evaluatedquantitatively by optimal comprehensive evaluation method and other methods. Results showedthat:the score order of stability degree indexe of community was: arbor planting>shrub planting>grass planting; other indexes achieved the same score order by these methods: arbor planting inthe first place,grass planting in the second place and shrub planting in the end, in which, integraterecovery degree of ecosystem were0.308,0.281,0.212respectively.In conclusion, through arbor planting, shrub planting and grass planting, either soil orvegetation characteristic of degraded red soil had been obviously improved comparing with the notreatment.The soil characteristics were still different with those of secondary forest as thetreatment time was short. On the condition that the soil erosion was controlled, the followingmeasures should be taken to further enhance the stability and the service function of ecosystem.Enhance the vegetation introduction strength of regeneration layer, properly increase the speciesrichness and the density of intolerant tree species, strengthen the cultivation of regeneration layer,increase the vertical stratification of community, and promote the succession of community fromconiferous forest to mixed conifer-broadleaf forest.