Dynamics Of Nutrient Loss From Surface Runoff And Its Relationship With Soil Nutrients In Moso Bamboo Forests Under Different Management Modes

To determine the effect of different management modes on runoff nutrient losses in Moso bamboo(Phyllostachys pubescens)forests under natural rainfall conditions,Qingshan Moso bamboo orchard of Lin'an District,Hangzhou City,Zhejiang province was selected as experiment area.Field observation stations were set up at field-sized catchments of extensive and intensive management plots,respectively The Continuous fixed-point observation study was carried out for a period of one year.The runoff and sediment yields of Moso bamboo forests under natural rainfall,the dynamic changes of runoff nutrient in Moso bamboo forest as well as the correlation between runoff nutrients and soil nutrients in slope land were studied.The main results and conclusions are as follows(1)The annual runoff yield of Moso bamboo forest for extensive and intensive management modals were 4851.0 m3·hm-2 and 8086.5 m3·hm-2,the annual sediment yield were 34.8 kg·hm-2 and 49.4 kg·hm-2,respectively.It can be seen that intensive management increased the runoff and sediment yield of Moso bamboo forest under natural rainfall conditions(2)Intensive management of Moso bamboo forest increases the risk of total nitrogen(TN)and total phosphorus(TP)loss.The annual TN loss amounts in runoff water of extensive management and intensive management of bamboo forest were 25.1 kg·hm-2 and 45.3 kg·hm-2,respectively,while the annual TP loss amounts were 0.21 kg·hm-2 and 0.31 kg·hm-2,respectively.Compared with extensive management,the loss of TN and TP in runoff water of intensive management increased by 80.68%and 47.62%,respectively(3)Under natural rainfall conditions,the annual TN and TP loss amounts with runoff and sediment loss in two management modes of Moso bamboo forest were 25.13 kg·hm-2 and 0.23 kg·hm-2 in extensive management,while 45.38 kg·hm-2 and 0.35 kg·hm-2 in intensive management.The loss of nitrogen and phosphorus is mainly caused by runoff.(4)The total nitrogen concentration in runoff is positively correlated with the available nitrogen in the middleslope soil with extensive management(R2=0.40).The total phosphorus concentration in runoff is negative correlated with downslope soil available nitrogen(R2=0.43),but positively correlated with downslope soil available phosphorus(R2=0.52)with intensive management.Intensive management has changed the relationship between runoff nutrient loss and soil nutrient availability at different slope positions(5)The average concentrations of exchangeable base ions in the runoff were in the order Ca2+>Mg2+>Na+>K+,and the loss of base ions in the runoff from the intensive management area were higher than that in the extensive management one.The dynamic change of base ions concentrations is mainly affected by season and operation mode,it changes actively in March,April,September and October,and intensive management led to increased loss of base ions in March and April,and decreased loss in September and October.