| In order to analyze the effects of forest canopy damage, especially suddenly change inabnormal litterfall caused by natural disasters on soil nitrogen mineralization, during the periodfrom2010October to2011February, a Castanopsis fissa community in Xiaokeng forest farm,south of Nanling Mountains was selected to study the litter changes thats on soil nitrogenmineralization. The treated sample plots iduced: control plots (CN), damage and removal andtreatment (TR); damage+retention and processing (TD); untreated+add foliage treatment(UD). In2012， the culture method using soil in situ was used for monitoring net nitrogenmineralization rate and other indexes of four different treatments of the four quarter. Theresults show that:(1) Differences in soil physical and chemical properties of different treatmentsIn spring,,the pH value, water content, organic carbon, total nitrogen, total phosphorus,available nitrogen between each treatment of CN, TR, UD and TD had no significant difference.In summer, soil moisture, pH, organic carbon, total phosphorus, available phosphorus and totalnitrogen among the different treatments (CN, TR, UD and TD) had no significant difference,but there existed significant difference in soil total nitrogen content between TR and TD andtotal nitrogen content of TR was significantly higher than that of TD. In autumn, soil moisture,organic carbon, total nitrogen, total phosphorus, available phosphorus among the differenttreatments (CN, TR, UD and TD) were not significantly different, but there was a significantdifference in soil pH between TR and UD, TD and TR, soil pH of TR was significantly lowerthan that of UD and TD. In winter, the soil pH value, soil water content, organic carbon, totalphosphorus among CN, TR, UD and TD treatments had no significant difference. But there aresignificant differences in the total nitrogen between TR and UD, TR and TD. There weresignificant differences in available phosphorus content between UD and CN, TD, TRtreatments. The soil available phosphorus content of UD was highest, followed by TD, but theeffective phosphorus content of CN was higher than that of TR. The differences of the effectivephosphorus content among different treatments were significant, size order: UD>TD>CN>TR,the average content of effective phosphorus of UD, TD, CN and TR were1.71,1.49,1.32and1.30mg/kg respectively. This indicated that increasing litterfall can promote soil effectivephosphorus and the phosphorus in surface litter can be transfered well into the soil.(2) Change trends of net nitrogen mineralization rate, the net nitrification rate, netammonification rate, the net leaching rate index following the different treatments and seasons.In the spring, there were no significant differences of the net nitrogen mineralization rate,the net nitrification rate, net nitrogen leaching rate among different treatments.In the summer, the differences of net nitrification rate, net N leaching rate among thedifferent treatments were not significant. But net nitrogen mineralization rate in CN and UDwas obvious difference, net nitrogen mineralization rate of CN is obviously higher than that ofUD.In the autumn, differences among the different treatments of the net nitrogenmineralization rate, net ammonification rate were not significant. Net nitrification ratesignificant differences between TR and UD, the former was smaller than the latter. Netleaching rate in TR is negative, and there existed outstanding differences between TR and CN,UD, TD.In the winter, differences among the different treatments of net nitrogen mineralizationrate, net ammonification rate were not significant. There was a significant difference in netnitrification rate of UD samples with CN plots, the net nitrification rate of UD (3.49mg·kg-1·month-1) was significantly less than that of CN (8.62mg·kg-1·month-1). There were notabledifferences of net leaching rate between UD and TR, TD. And net nitrification rate of TR andTD were negative,,-6.80mg·kg-1·month-1and-6.70mg·kg-1·month-1, respectively. |
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