Litter Fall Character And Effects On Soil Ecological Functions Of Different Types Of Plantations In Karst Area

In this thesis, the author investigated litter production, litter decomposition and ecological function of four types of plantations for restoration purposes (E.ulmoides Oliver plantation, A.cremastogyne plantation, C.duclouxiana plantation and P.salicina plantation) in order to evaluate ecological benefits of plantation restoration. The main research subjects include the seasonal dynamics of litter production and decomposition rate, the water conservation function of litter and surface layer soil, the effects of litter on soil quality, such as physical and chemical properties, enzyme activity and soil carbon contents. The main results were described as follows:1. The total amount of litter and annual litter production of four types of plantations were in order of A.cremastogyne> E.ulmoides> P.salicina> C.duclouxiana. The definite peak of monthly litter production of four types of plantations occurred between July and September.2. By means of litter bag method, the dynamics of litter decomposition was studied. The results showed that the order of litter decomposition rate of those four plantations was E.ulmoides> P.salicina> A.cremastogyne> C.duclouxiana. Litter decomposition processes were simulated with Olson's exponential models, and precise fitting results were received. It was estimated that 5-10 years were needed for 95% of the litter finishing decay among four studied plantations. The C and N contents of leaf litter in four plantation stands decreased at earlier stage of decomposition, then accumulated at the middle stage of decomposition and finally released at the latest stage.3. The order of water-holding capacity of litter fall among four types of plantations was A.cremastogyne> E.ulmoides> P.salicina> C.duclouxiana. The relationship between the water-holding capacity of the litter fall and the immersed time could be simulated with exponential function. The relationship between water absorption rate and the immersed time matched the power function.4. The effects of litter on soil physical and chemical characteristics, the soil enzyme activity and carbon pool were studied. The results indicated that the litter of plantation could improve the soil quality. The SOC and DOC contents decreased with the increasing soil depth. In addition, there was a significant correlation between litter accumulation and DOC content at the soil depth of 0 to 15 cm (R2=0.8485*). However there was no significant correlation between litter accumulation and SOC content at the soil depth of 0 to 15cm (R2=0.3441).