光照强度对毛竹竹笋到幼竹生长过程的影响

为了解毛竹竹笋到幼竹生长过程对光的需求,通过对野外毛竹林样地内竹笋设置笋尖透光、全遮光2种处理,以全自然光作对照,动态测定了各处理下毛竹幼竹的生长指标,结果表明:不同光照强度对毛竹幼竹成竹过程有显著差异,笋尖透光处理的毛竹生长最好,株高、胸径分别比对照提高了12.99%和2.43%。从动态生长看,毛竹株高从3月份到4月底,增长相对缓慢,5月份开始,增长明显加快,到5月下旬至6月初增长平缓,毛竹的生长过程基本结束。而毛竹胸径从4月底开始,迅速增加,到5月中旬达到稳定不变,与对照相比差异不显著(P<0.05),说明毛竹胸径的大小几乎不受光照强度的影响,而取决于竹笋的大小。但其生长过程受到光照强度的影响,适当遮光有助于提前进入胸径生长。3种立地条件下,表现的趋势基本一致。这对解释毛竹幼竹在林下迅速进入林冠层而似乎不依赖较强光照强度有着重要的理论意义,同时有利于分析毛竹成功扩张到周边森林群落的内在机制。

Effects of Shading on Growth of Phyllostachys pubescens

An experiment was conducted to study the demand of Phyllostachys pubescens for light during the growth process.P.pubescens in three bamboo plantations was treated with two different shading levels: with bamboo shoot tips to light only and 100% shading.In contrast with natural light,the dynamic changes of growth indexes of P.pubescens were analyzed.Results indicate that different shading treatments have a significant effect on the growth of P.pubescens.P.pubescens with bamboo shoot tip to light only grew better than those under natural light,and the seedling height and diameter at breast height(DBH) increased by 12.99% and 2.43%,respectively.P.pubescens grew relatively slowly in height from March to late April,it grew fast in May,and then the height growth was basically complete in late May or early June.A rapid growth in DBH was observed in late April,and tended to be stable in mid-May.There is no obvious difference in DBH growth between the two treatments and the control,indicating that the growth of DBH is not affected by light intensity,but greatly depends on the size of bamboo shoots.However,the growth process is influenced by light intensity.Proper shading is beneficial to advance the time of DBH growth.Similar tendencies were observed under three different site conditions.The result of the experiment is of great theoretical significance to explain the independence of light for P.pubescens during the process from undergrowth to canopy layer.Moreover,it is valuable to analyze the intrinsic mechanism of bamboo grove expansion to its peripheral forest communities.