间伐对落叶松人工林内草本植物多样性及其组成的影响

通过对落叶松人工林间伐林分和未间伐林分林下草本植物的调查以及林下光照条件的测定,分析间伐对林下草本植物多样性、组成的影响及其与光照条件的关系。结果表明,除均匀度指数在春、秋季表现不同外,间伐林分的丰富度指数、多样性指数均高于未间伐林分,说明间伐后草本植物多样性明显增加。依据草本物种在间伐前后出现与否和密度变化情况将其划分为正反应种(间伐后密度明显增加和间伐后新出现的种)、中性反应种(间伐后密度变化不明显或没有变化的种)和负反应种(间伐后密度明显减小和间伐后消失的种),间伐后出现大量新的草本种类,同时在间伐和未间伐林分的共有种中有许多表现为负反应种。在间伐林分中,间伐行和未间伐行的共有种春季有11个、秋季有10个,分别占间伐林分草本总种数的17.74%和15.15%,表明各行草本植物组成差异较大;各指数均呈现了从间伐行到未间伐行逐渐减小的趋势。主要的正反应种、中性反应种和负反应种均表现出与光照具有一定的相关性,且这种相关性与间伐和非间伐林分之间各草本物种与光照的相关性基本一致。

Effects of thinning on species diversity and composition of understory herbs in a larch plantation

The study showed that there was a difference in the species diversity of understory herbs between thinned and un-thinned stands. All of the diversity indices except evenness had higher values in thinned than in unthinned stands,suggesting that the diversity of herb layer was increased after thinning. According to the changes of herb density and the appearance or not of a species,all of the herb species were classified into three types,i.e.,positive,neutral,and negative,which referred to a species newly appeared and having an obviously increased density after thinning,with no or no obvious changes in its appearance and density after thinning,and disappeared and having an obviously decreased density after thinning,respectively. Many new species were found in thinned stands,and most species found in both thinned and unthinned stands were negative species. In all 9 sub-plots,there were 11 mutual species found in spring and 10 mutual species in autumm,accounted for 17.74% and 15.15% of all the species in thinned stand,respectively. All of the diversity indices had the highest values in middle sub-plots,and most of them showed a consistent trend,i.e.,reduced from middle to side sub-plots. There was a definite correlation between most of the three types of species and light condition,which was similar in the two stands.