外源性氮和磷添加对马尾松凋落叶分解及土壤特性的影响

Effects of N and P Additions on Decomposition of Needle Litter and Soil Characteristics in Pinus massoniana Woodland

研究外源性氮和磷对马尾松(Pinus massoniana)凋落叶分解速率、分解过程中N、P、K含量变化及马尾松林地土壤生化特性的影响,为阐明外源性氮和磷对凋落叶分解土壤养分的影响及为森林养分管理提供科学依据。采用尼龙网袋分解法,在广东马尾松林内建立4块5 m×5 m的小样地,放置凋落叶样品,测定其分解速率和N、P、K含量变化。结果表明,施N对马尾松凋落叶的分解有抑制作用,施P及N+P对凋落物的分解速率有不同程度的促进,其中施P处理的分解最快;分解24个月后,对照,施N、P和N+P的马尾松纯凋落叶分解率分别为90%,74%、98%和97%。施N、P和N+P的马尾松林地凋落叶N含量显著大于凋落叶的初始N含量,分解24个月后各处理凋落叶的N含量分别增加了18%、34%、23%和38%;各处理凋落叶P含量在分解过程中呈现上升的趋势,分解24个月后凋落叶的P含量分别显著增加了27%、21%、163%和144%,P和N+P处理的凋落叶P含量上升幅度大;而凋落叶K含量无明显变化规律。施N和N+P显著增加了土壤的全P和有效P含量,增量分别为4%、14%和23%、222%;加P显著增加土壤了全P、全K和有效P含量,增量分别为18%、6%和277%。施N、施P和施N+P 3种处理显著增加了土壤细菌、真菌和放线菌数量,加P提高了脲酶、磷酸酶及过氧化氢酶活性,增量分别为11%、17%和16%,施N+P提高了磷酸酶和过氧化氢酶活性,增量分别为7%和2%。综上所述,施N抑制马尾松凋落叶的分解,而施P及N+P促进凋落物的分解。在马尾松林施用P肥可以促进凋落叶的分解和养分循环。

The effects of external nitrogen and phosphorus on needle litter decomposition and soil biochemical characteristics were investigated in Pinus massoniana woodland in order to provide a scientific basis for understanding the mechanism of influence of nitrogen and phosphorus on needle litter decomposition and forest soil management. The study was conducted over 2 years using the litterbag technique in a P. massoniana stand in Yongyun Forest Farm, Guangdong Province, China. Four small sample plots （5 m ×5 m） were established in the P. massoniana stand. Within each of the sample plots, needle litters were placed and their decomposition rate and N, P and K contents were analyzed. The decomposition of needle litter was delayed by N addition or accelerated by P and N＋P additions and the decomposition rate with P addition was the fastest among the four treatments in the P. massoniana woodland. The needle litter treated with the control, N, P and N＋P additions was decomposed by 90%, 74%, 98% and 97%, respectively, 24 months after the experiment. The N content of needle litter in was significantly greater than their initial N content, which increased by 18%, 34%, 23% and 38%, respectively, P content of needle litters increased by 27%, 21%, 163% and 144%, respectively, under the control, under N, P and N＋P additions, and among which increase range of P content was great in P and N＋P addition treatments. K content of needle litters changed irregularly. Soil total P and effective P contents significantly increased by 4%, 14% and 23%,222% under N and N＋P additions, respectively. Soil total P, total K and effective P contents significantly increased by 18%, 6% and 277%, respectively, under P addition. The N, P and N＋P addition treatments significantly increased the numbers of soil bacteria, fungi and actinomycetes. Activities of soil urease, acid phosphatase and catalase significantly increased by 11%, 17% and 16%, respectively, under P addition. Activities of soil acid phosphatase and catalase significantly increased by 7% and 2%, respectively, under N＋P addition. In conclusion,N addition delayed decomposition of needle litter, whereas P and N＋P additions accelerated its decomposition. Application of P fertilization can improve litter decomposition and nutrient cycling.