模拟降水减少对帽儿山地区兴安落叶松径向生长的影响

以2004年在小兴安岭帽儿山地区栽植的兴安落叶松(Larix gmelinii)为研究对象,在2012年,经过100%减雨、50%减雨、冬季除雪和对照4种处理,在控雨的前期(6月)和后期(8月)用微生长锥取样利用石蜡切片方法测量扩大细胞的径向长度和数量。在10月末用生长锥取样,打磨后测量成熟管胞的径向长度和数量,进而分析降水减少对兴安落叶松径向生长的影响。结果表明:在帽儿山地区,生长季温度与兴安落叶松径向生长显著正相关,降水在生长季后期为负相关。大树芯成熟管胞测定表明,3块样地综合而言,除雪组成熟管胞数量最多,其次是对照组,50%减雨组和100%减雨组成熟管胞数量最少;管胞径向长度在各个处理组之间差异不显著。但是,在3块样地中,成熟管胞数量和径向长度在相同处理间测定结果有差别,样地1的100%减雨组、50%减雨组、除雪组和对照组中成熟管胞数量随土壤湿度增加而增加,径向管胞长度差异不明显;样地2的除雪组中成熟管胞径向长度显著小于其他3个实验组,而50%减雨组、100%减雨组和对照组的成熟管胞径向长度和数量均差异不显著;样地3中4个实验组的成熟管胞数量均差异不显著,成熟管胞径向长度100%减雨组略小于其他3个实验组,这与样地3遮阴较大、土壤湿度较高有关。石蜡切片的形成层扩大细胞分析表明:在减雨处理的初期(6月份),样地3在扩大细胞的数量上,随着不同处理间土壤湿度的减小而减少。在减雨处理的后期(8月份),样地1扩大细胞的数量随着不同处理间土壤湿度的减小而减少。研究结果表明降水减少会对兴安落叶松径向生长产生影响,其影响程度取决于微环境条件的差异,且不同时期降水减少的影响也有差异。

Impact of decreasing precipitation on Larix gmelinii radial growth in Maoershan, Xiaoxing'an Mountain, China

A Larix gmelinii forest planted in 2004 at Maoershan, Xiaoxing''an Mountain, China was taken as study materials. In 2012, the Larix gmelinii forest was divided into three plots and four removal precipitation treatments in each 25 m×25 m plot: 100% rainfall removed, 50% rainfall removed, snow removal and control. To observe the effect of decreasing precipitation on radial growth of Larix gmelinii in cellular scale, the radial length and quantity of expansion cells were measured by using paraffin section method with micro increment borer in early June and late August. Tree-ring cores were extracted by increment borer in October, and the radial length and quantity of mature tracheids were measured to identify the impact of decreasing precipitation on Larix gmelinii radial growth. The results showed that the radial growth of Larix gmelinii significantly positively correlated with monthly mean temperature at growing season, and negatively correlated with monthly total precipitation at the end of growing season. In terms of three plots taken together, the number of mature tracheids in snow removal treatment was the largest, followed by the control treatment, and then in 50% and 100% rainfall removal treatment. Radial length of mature tracheids, however, did not show significant difference among four treatments. Whereas the number and radial length of mature tracheids among three plots were significantly different. In plot 1, the number of mature tracheids in 100% and 50% rainfall removal treatment, snow removal treatment and control increased with the increasing of soil moisture, but the radial tracheid length did not show obviously difference. In plot 2, the radial length of mature tracheid in snow removal treatment was significantly smaller than those in other three treatments, while the radial length of mature tracheid in 50% and 100% rainfall removal treatments were not significantly different with that in control treatment. In plot 3, there was no significant difference in the radial length of mature tracheid among four treatments, except the radial length of mature tracheid in 100% rainfall removal treatment was slightly smaller than that in other three treatments. It could be caused by lots of shade and higher soil moisture in plot 3. The data of paraffin was to investigate the effects of decreasing precipitation on the number of cambium cell division and radial length from the cambium cells that expand in June and August. At the beginning of decreasing precipitation (in June), the number of expansion cells in plot 3 was decreased with the decrease of soil moisture among different treatments. At the end of decreasing precipitation (in August), the number of expansion cells in plot 1 was decreased with the decrease of soil moisture among four treatments. Our results indicated that the decrease of precipitation will produce a significant impact on radial growth of Larix gmelinii in Maoershan, while the extent of the influence is determined by the microenvironment of tree growth. In addition, the effects of decreasing precipitation in different seasons on Larix gmelinii radial growth are significant differences.