Return Sharacteristics Of Forest Vitter And Valuation Of Soil Water Conservation Function In Degraded Red Soil

The accumulation of litter on the soil surface has played an important role in the process of vegetation restoration,it also has an important role in enhancing the soil water conservation function.In this study,artificial coniferous & broad leaved mixed forest,secondary mixed coniferous & broad leaved forest and artificial broad leaved mixed forest as the research objects on the typical subtropical red soil in eroded land.The amount and monthly dynamics features of litterfall,the amount of carbon and nitrogen content and the amount of return,Surface litter water holding characteristics and evaluation of water conservation functions of topsoil were studied in the three vegetation restoration models.The research results can provide theoretical bases for choosing vegetation restoration measures.The main results were as follows:(1)The amount of annual litter was 5602.97~7529.23 kg·hm-2 in different vegetation restoration models.There were obvious differences.The annual litter amount of artificial coniferous & broad leaved mixed forest was significantly higher than that of secondary mixed coniferous & broad leaved forest and artificial broad leaved mixed forest(P<0.05).The monthly dynamics of litter in artificial coniferous & broad leaved mixed forest was three peaks,peak appears in 3-4 months,august and 10-11 months.Secondary mixed coniferous & broad leaved forest and artificial broad leaved mixed forest was two peaks,peak appears in 3-4 months and 10-11 months.(2)The amount of organic carbon return in litter was 2409.81~3794.62 kg·hm-2 in different vegetation restoration models.The amount of water-soluble organic carbon return in litter was 217.24~442.56 kg·hm-2.The amount of total nitrogen return in litter was 59.07~87.84kg·hm-2.The amount of water-soluble nitrogen return in litter was 217.24~442.56 kg·hm-2.The order of all were artificial coniferous & broad leaved mixed forest > artificial broad leaved mixed forest > Secondary mixed coniferous & broad leaved forest.(3)The amount of litter accumulation was 3311.61~7649.34 kg·hm-2 in different vegetation restoration models.The litter accumulation of artificial coniferous & broad leaved mixed forest was 1.79 times of that of artificial broad leaved mixed forest and 2.31 times of that of secondary mixed coniferous & broad leaved forest.The maximum water holding capacity of litter was about 2 times of its own weight.The natural moisture content,the maximum water holding capacity and the water absorption rate of litter were artificial coniferous & broad leaved mixed forest > artificial broad leaved mixed forest > secondary mixed coniferous & broad leaved forest.(4)The average soil bulk density was 1.46~1.57 g·cm-3 of different vegetation restoration models in the soil depth of 0~30cm.And it shows an increasing trend with the increase of soil depth.The total porosity,natural moisture content and the maximum water holding capacity of soil showed a downward trend in general.The order of all were artificial broad leaved mixed forest > artificial coniferous & broad leaved mixed forest > secondary mixed coniferous & broad leaved forest.The soil non capillary porosity of artificial coniferous & broad leaved mixed forest was maximum,and it was 9.20%.and that of secondary mixed coniferous & broad leaved forest(8.12%)was the second and the artificial broad leaved mixed forest(4.87%)was minimum.The order of soil stable permeability was secondary mixed coniferous & broad leaved forest > artificial coniferous & broad leaved mixed forest > artificial broad leaved mixed forest.The soil layer is the largest reservoir of forest.(5)The correlation analysis between litter and soil water conservation function was as follows: The amount of litter accumulation and water-soluble organic carbon return were significantly positively correlated with soil organic matter.The amount of organic nitrogen return was significantly correlated with soil organic matter,bulk density and natural water content.Litter C/N ratio was significantly correlated with soil bulk density and natural water content,total porosity and capillary porosity.By general comparison,the annual litter,annual litter carbon return and annual litter nitrogen returned to maximum in artificial coniferous & broad leaved mixed forest,but also the water holding capacity of litter layer and soil water conservation function were the best,that of artificial broad leaved mixed forest was the second and the enclosed forest was the worst.The maximum water holding capacity was 1121.52~1250.33t·hm-2.And it was 84.45~183.95 times of litter water holding capacity.