Investigation And Study On Vegetation-Effect In Different Vegetation Restoration Patterns Of Returning Land For Farming To Forestry In Guangxi

Six vegetation restoration patterns of returning land for farming to forestry including Illicium verum,Juglans regia,Castanea mollissima,Pinus massoniana,Betula alnoides and Eucalyptus in Baise and Hechi of Guangxi were studied by establishment of sample plot.The results followed that:1.The biomass of tree layer increased with the time of returning land for farming to forestry,and it was related to the site conditions,the fertilizer,the initial planting density.The fast-growing characteristic of tree species,density and site conditions affect the biomass allocation of tree layer.The crown density of tree layer significantly affected the biomass of shrub and herb in the timber forest model,and they were negative correlative.The artificial factor significantly affected the biomass of shrub and herb in the economic forest model,and they were negative correlative.The volume of timber forest correlated to the planting density.2.The undergrowth vegetation of various models was mainly the herbage, which community structure was simple,and the differentiation of administrative levels was not obvious.The dominant species in herb vegetation community were positive-herb,and mainly gramineae and compositae.The species diversity indexes of Shrub and herb layer were less than 2.5796,which difference was negative correlative with the time of returning land for farming to forestry.With the time increased of returning land for farming to forestry,there was no significant difference among shrub and herb species diversity index of various vegetation restoration patterns,except that herb species diversity index in of vegetation restoration patterns of Illicium verum was significant different because of the artificial factor.In 2004,Shannon-Wiener indexes were significant different between Betula alnoides and Pinus massoniana,Betula alnoides and Juglans regia,Eucalyptus and Juglans regia,and Castanea mollissima and Juglans regia.The species diversity index between Eucalyptus and Castanea mollissima was very significantly different in the herb layer.There was very significant difference of Simpson index between Pinus massoniana and Castanea mollissima in the herb layer.3.The thickness of litter was 1-3cm,which was positive correlate to the time of returning land from farming to forestry in all vegetation restoration patterns.Dry weight of litter was negative correlative with biomass of undergrowth shrub and herb,but was positive correlative with the artificial factor.Water absorption multiples of litter was correlative to the composition of litter.The more proportion of litter of shrub and herb which was easily decomposed,the more water absorption multiples of litter.Contrarily,the more proportion of litter of Pinus massoniana and Eucalyptus which were difficultly decomposed,the less water absorption multiples of litter.Water holding capacity of litter was relevant to the biomass of litter and water absorb multiples,the order was Betula alnoides＞Juglans regia＞Eucalyptus＞Illicium verum Pinus massoniana＞Castanea mollissima.