间伐对杉木人工林林下植被多样性及其营养元素现存量影响

间伐改变了林分结构，影响林下植被的生长和发育，但长期间伐对杉木Cunninghamia lanceolata林下植被多样性的影响尚缺乏系统研究。在浙江开化通过样地调查，采用Simpson指数、Shannon-Wiener指数和Pielou均匀度指数研究3种间伐处理下杉木人工林林下植被多样性的变化；分析林下植被主要营养元素含量，研究间伐对营养元素现存量的影响。以试验区传统经营方式为对照，即林木生长中期（第14年）进行1次轻度间伐（间伐强度约15%，T1）；中度（总间伐强度约35%， T2）和强度（总间伐强度约50%，T3）间伐均在第7年和第14年进行了2次间伐。间伐15年后的结果表明，3种间伐处理下，林下植物种类数分别为18种（T1）、17种（T2）和20种（T3），林下植被总密度和盖度均随间伐强度增加而增大；林下植物Simpson指数、Shannon-Wiener指数和Pielou均匀度指数在不同间伐处理之间均没有显著差异（P＞0.05）。林下植被全碳（TC）、全磷（TP）和全钾（TK）含量在不同间伐处理之间差异不显著（P＞0.05），全氮（TN）含量随间伐强度增加而降低，其中T3处理显著低于T1（P＜0.05）。林下植被生物量随间伐强度增大而增加，林下植被TC、TN、TP和TK现存量在不同间伐处理之间均没有显著差异（P＞0.05）。这些试验结果说明杉木人工林间伐15年后间伐强度不会显著影响林下植被多样性和营养元素的积累。

Effect of thinning on understory vegetation diversity and its nutrient stocks in Cunninghamia lanceolata plantation

Thinning changed stand structure, which influenced growth and development of understory vegetation. Long term effect of thinning on understory vegetation diversity is still poorly understood. Simpson index、Shannon-Wiener index and Pielou index were used to evaluate understory vegetation diversity in three thinning treatments in Chinese fir plantations in Kaihua County, Zhejiang Province,China. Change of nutrient contents and current nutrient stocks of the understory vegetation in the three thinning treatments were also studied. Traditional silviculture operation as a control （stand was thinned approximately 15%（T1） at the 14th year during a rotation）, moderate （total thinning intensity approximately 35%, T2） and heavy intensity （total thinning intensity approximately 50%, T3） thinning treatments were thinned twice （in the 7th year and 14th year）. 15 years after thinning, the number of plant species in the three thinning treatments was 18 （T1）, 17 （T2） and 20 （T3）, respectively. Total plant density and coverage of the understory vegetation increased with the increase of thinning intensity. The Simpson index、Shannon-Wiener index and Pielou index of the understory vegetation were no significant differences among the three thinning treatments （P＆gt;0.05）. Total carbon （TC）, total phosphorus （TP） and total potassium （TK） contents of the understory vegetation were not significantly different among these three thinning treatments （P＆gt;0.05）. Total nitrogen （TN） content reduced with increasing thinning intensity, TN in T3 treatment was significantly lower than that in T1 treatment （P＆lt;0.05）. The biomass of understory vegetation increased with the increase of thinning intensity. No significant difference was detected in TC, TN, TP or TK stocks of understory vegetation among the three thinning treatments （P＆gt;0.05）. These results illustrate thinning intensity may not have a significant impact on understory vegetation diversity and nutrient accumulation in Chinese fir plantation after 15 years treatment.