马尾松人工纯林凋落松针数量及基质质量动态

凋落物是森林生态系统的重要组成部分,其产量与基质质量是影响植物-土壤间养分循环的重要因素。以3种密度马尾松人工纯林为研究对象,分析松针凋落模式及基质质量变化规律,比较不同林分密度间松针凋落特性差异,探讨松针基质质量、产量及气候因素间的关系。结果表明:松针凋落数量动态变化属双峰型,在2月呈现一个小高峰,在10/11月达最高峰。3种密度林分中各月凋落松针的N、P浓度均差异显著(P0.05),全年最高值出现在4—6月,8—12月的松针N、P浓度显著低于其他时段;不同月份凋落松针木质素浓度也差异显著(P0.05),在2月木质素含量达峰值,7、8月含量较低;3种密度林分中各月凋落松针的C/N、C/P、L/N和L/P比存在显著差异(P0.05),4—6月呈现最低值,9/11/12月则出现最高值,相差达2—3倍,且均高于养分释放临界值,不利于松针N素和P素的释放。林分密度对松针凋落数量和N浓度影响显著(P0.05),中等密度林分松针凋落数量高于低、高密度林分,中、高密度林分凋落松针N浓度显著高于低密度林分。凋落松针基质质量与自身凋落数量密切相关,并且受气温和降水量的影响。凋落松针N、P浓度与凋落数量呈显著负相关(P0.05),C/N、C/P、L/N、L/P比与凋落数量呈显著正相关(P0.05),说明更多凋落物产量将伴随着更低的基质质量,将有更慢的分解速度。

Dynamics and quality of leaf litter fall in pure Pinus massoniana plantations

Litter is an important component of forest ecosystems, and its production and substrate quality influence the cycling of nutrients among plants and the soil. Therefore, to explore the relationships among litter production, litter chemistry, and meteorologic factors, three Pinus massoniana stands with different stand densities (low, medium, and high) were selected and compared on a monthly basis. The production of leaf litter exhibited a bimodal distribution pattern, with a smaller peak in February and a higher peak during October and November. The concentration of N and P varied considerably among months (P < 0.05), with peak values observed from April to June and significantly lower values observed from August to December. The concentration of lignin (L) varied considerably among months (P < 0.05), with the highest concentration observed in February and subsequent decreases until July or August. The C/N, C/P, L/N, and L/P ratios also varied between months (P < 0.05), with significantly lower value in April, May, and June and significantly higher values in September, November, and December. The ranges spanned nearly two-fold or three-fold differences, and all were above critical values, which generally inhibits the release of N and P. Meanwhile, stand density significantly influenced litter quantity and N concentration (P < 0.05), with significantly more litter produced by the medium-density stand and a significantly lower N concentration in litter from the low-density stand. The substrate quality of the litter were closely related to litter quality and were influenced by temperature and precipitation, whereas monthly litter production was negatively correlated with the litter''s N and P concentrations and positively correlated with its C/N, C/P, L/N, and L/P ratios. Therefore, greater litter production was associated with lower litter quality and, subsequently, slower decomposition.