Study On The Nutrient Characteristics Of Soil And Litter And Its Water Conservation Function In The Guansi River Basin

The Guansi river is located in the northwest of Sichuan Basin,is an important water conservation and soil and water conservation area in the upper reaches of the Yangtze River.In recent years,due to the increasing human activities,the disturbance of soil and litter in different vegetation and topographic conditions in the basin has not only affected the soil and water conservation,but also poses a potential threat to the ecological security of the middle and lower reaches of the Yangtze River.In this paper,the soil nutrient characteristics and water holding capacity of different vegetation and topography were studied by means of field investigation and laboratory analysis,and the effects of different vegetation and topography Litter to maintain the ability of water and nutrient return,from the perspective of the evaluation of the value of soil and water conservation ecological services to explore the different values of soil fertility under the conditions of water conservation and water conservation value,with a view to the small watershed effective control of soil erosion and ecological restoration and reconstruction theoretical guidance.The main conclusions are as follows:(1)The contents of soil nutrient were the highest in different vegetation cond-iti ons,and the contents of soil were the highest,and the content of soil organic matter was the lowest.The soil nitrogen content was the lowest among the mixed woodl-a nd of Pinus massoniana and Pinus massoniana.The content of phosphorus in the 20-40cm soil layer was the lowest,and the soil potassium content was the lowest in the pure woodland of Eucalyptus grandis,and the soil nutrient level was the lowe st.Soil nitrogen supply intensity of 1-2.5%,phosphorus supply intensity of 2-10%,pot assium supply intensity of less than 1%.Soil water holding capacity of 0-20cm soil layer is more than 20-40cm soil layer,0-20cm soil maximum water holding capaci ty,capillary water holding capacity and field maximum water content are bamboo f orest,Eucalyptus grandis forest,Pinus massoniana pure forest,The minimum values were Platycladus orientalis-Quercus acutissima mixed forestand;20-40cm soil layer maximum holding capacity Kashiwagi-Pinus massoniana mixed forest the highest,Pi nus massoniana-Kashiwagi-Quercus acutissima mixed forest minimum.Capillary wat er holding capacity,field water holding capacity of Eucalyptus grandis is the highe st,Platycladus orientalis-Quercus acutissima mixed forest minimum.(2)There were significant differences in the vegetation types between the six typical vegetation types in the Yaowan and Gaojiawan catchment areas.The litter organic carbon content was the highest in Pinus massoniana pure forest,Eucalyptus grandis pure forest minimum;The total nitrogen content of Eucalyptus grandis was the highest,Pinus massoniana pure forest was the lowest.The total phosphorus content of Pinus massoniana was the highest,and the mixed forest of Platycladus orientalis-Quercus acutissima was the lowest;Potassium content was the highest in Pinus massoniana,and Pinus massoniana-Kashiwagi-Quercus acutissima was the lowest.Four indicators of litter decomposition,litter lignin content Pinus massoniana pure forest,Platycladus orientalis-Quercus acutissima mixed forest minimum.The results showed that the contents of litter decomposition were the highest in Pinus massoniana and the lowest in bamboo forest.Cellulose content Pinus massoniana Pure forest was the highest,Pinus massoniana-Kashiwagi-Quercus acutissima was the lowest;C/N Pinus massoniana was the highest Eucalyptus grandis forest minimum;lignin/N Pinus massoniana pure forest,eucalyptus pure forest minimum.The results showed that the average anti-membership function and the potential decomposition ability of litter decomposition were as follows:Litter litter potential decomposition ability Platycladus orientalis-Quercus acutissima mixed forest strongest,Pinus massoniana pure forest the weake.The maximum water holding capacity of litter was the largest in Pinus massoniana.And the change trend of water holding capacity and water time was in accordance with the corresponding function model.(3)The content of soil nutrient in different locations of Jiangjiawan catchment area is higher than that of sunny slope,0-20cm soil layer is higher than 20-40cm soil layer,soil nutrient is relatively rich and trench The supply intensity of soil nitrogen was 1-2%,the supply of phosphorus was less than 7%and the supply of potassium was less than 0.5%.The soil water holding capacity in the different locations of the Jiangjiawan catchment channel is higher than that of the sunny slope,the 0-20cm soil layer is higher than 20-40cm soil layer,the interaction between the channel position and the slope position is The impact of the indicators of water is not significant.(4)The nutrient content of litter in different locations of Jiangjiawan catchment area is higher than that of sunny slope and slope,and the content of litter in lower and lower slope is relatively high,And the channel nutrient enrichment position is just the opposite.The potential decomposition capacity of the litter in different positions of the channel is stronger and the sunny slope,and the decomposition ability of the channel ditch is stronger.The maximum water holding capacity of the litter showed a higher slope than the sunny slope,and the law of water holding capacity and the rate of water uptake at any time was in accordance with the corresponding function model.(5)The value of soil fertility and the potential return value of litter nutrient under the condition of different vegetation in Gao wan Bay and Gaojiawan catchment area totaled 260.19 million yruan·hm-2,and the value of water conservation was 35,300 yuan hm-2,totaling 2.6372 million yuan hm-2;The value of soil fertility and the potential return value of litter nutrient under different vegetation conditions were 1.3781 million yuan·hm-2,the value of water conservation was 11,200 yuan·hm-2,totaling 1,389,300 yuan·hm-2,and the three catchment areas Soil fertility value,litter nutrient potential return value and water conservation value under different vegetation conditions totaled 402.65 million yuan·hm-2.