模拟氮沉降对华西雨屏区慈竹林凋落物分解的影响

试验设对照(CK，0 kg·hm^-2·a^-1)、低氮(LN，50 kg·hm^-2·a^-1)、中氮(MN，150 kg·hm^-2·a^-1)和高氮(HN，300 kg·hm^-2·a^-1)4个施氮水平,通过原位试验，研究了模拟N沉降对华西雨屏区慈竹(Neosinocalamus affinis)林凋落物分解的影响.结果表明：不同组分凋落物分解过程中，慈竹叶片分解速率最快，其次是箨，枝最慢，分解15个月时，叶片、箨、枝的质量残留率分别为26.38%、46.18%和54.54%，三者差异极显著(P<0.01)；叶片在凋落后第1～2月和7～10月分解较快，而箨和枝则在第5～8月分解较快；凋落叶片分解95%需要的时间(2.573年)分别比箨和枝短1.686年和3.319年.凋落叶分解15个月时，各N沉降处理间分解率差异不显著；凋落箨分解95%需要2.679～4.259年，其中MN分解率最高，CK最低；凋落枝经过15个月的分解，各处理分解率大小顺序为MN>HN>LN>CK，MN与LN处理间差异达显著水平(P<0.05).说明N沉降对3种凋落物分解均有明显的促进作用，且对凋落箨促进作用最强；但随着N沉降浓度的增加和时间的延长，其促进作用减缓.

Effects of simulated nitrogen deposition on litter decomposition in Neosinocalamus affinis stands in rainy area of West China

An in situ experiment was conducted to study the effects of simulated nitrogen deposition on the litter decomposition in Neosinocalamus affinis stands in rainy area of West China. Four treatments were installed, i.e., null N (CK, 0 kg·hm^-2·a^-1), low N (LN, 50 kg·hm^-2·a^-1), medium N (MN, 150 kg·hm^-2·a^-1), and high N (HN, 300 kg·hm^-2·a^-1). Among the litters, leaf had the highest decomposition rate, followed by sheath, and twig, with a remaining rate aft
er decomposing for 15 months being 26.38%, 46.18%, and 54.54%, respectively (P<0.01). Leaf litter decomposed faster during the first 2 months and the 7^th-10^th month, while the decomposition of sheath and twig was faster from the 5^th to the 8^th month. It took 2.573 years to decompose 95% of l
eaf litter mass, 1.686 years and 3.319 years shorter than that of sheath and twig, respectively. After 15 months decomposition of leaf litter, no significant differences were observed among different treatments. To decompose 95% of sheath litter needed 2.679-4.259 years, being the longest in CK and the shortest in treatment MN. After decomposing for 15 months, the decomposition rate of twig litter was in the order MN>HN>LN>CK, and significant difference existed between treatments MN and LN. Nitrogen deposition had obvious promotion effect on the litter decomposition in the N. affinis stands, but this effect decreased with increasing deposited N concentration and time extension.