太白红杉林林窗特征及其对群落更新的影响研究

【作者】 涂云博；

【导师】 王孝安；

【作者基本信息】 陕西师范大学 ， 生态学， 2008， 硕士

【摘要】 太白红杉(Larix chinensis)是我国特有的国家二级保护植物,主要分布于秦岭的太白山,另外在光头山、柞水牛背梁国家级自然保护区、洋县长青国家级自然保护区等也有少量分布,太白红杉是秦岭山区最上线的唯一乔木树种,是该地生态系统的重要组成部分,在涵养水源、稳固山石、保持水土等方面发挥着重要的作用。林窗干扰是森林群落中经常发生的重要的小规模干扰,它不仅是森林生态系统得以长期维持的重要驱动力,而且对森林结构、循环和更新产生重要的影响。系统研究林窗干扰可为受干扰森林生态系统的恢复提供理论指导。本文通过对秦岭太白红杉林林窗特征及其对群落更新的影响研究,揭示了不同海拔太白红杉林林窗的分布和形成特点及其对优势树种的更新的影响机理,为研究秦岭太白红杉林群落的自然更新及抚育和管护措施提供科学依据。在太白红杉集中分布的秦岭太白山地区按照上、中、下限各设置一个大小为100m×100m的样地,对每个样地内的林窗进行数量统计,调查每个林窗的特征指标以及其中的幼苗、幼树数量和特性指标:在林窗临近处做1个与林窗同样面积大小的样方,调查所有乔木树种(包括幼苗和幼树)的数量、高度、胸径、冠幅等特性指标,运用统计分析等研究方法得到以下主要结果:(1)太白红杉分布的下限和中部,以中小林窗为主,大林窗较少;而在上限区域,以大型林窗为主。在其分布的下限、中部和上限,林窗面积占样地面积的比例分别为9.4%、34.4%和30.4%,而扩展林窗的面积占样地面积的比例分别为22.6%、67.0%和54.6%。(2)太白红杉林的林窗形成主要是上层乔木发生折干、折枝、掘根风倒或枯立几种方式。随着海拔的升高,林窗的形成方式逐步由枯立为主转为以折干为主,林窗的形成方式逐步由单一方式转为多种林窗形成方式。(3)太白红杉林的林窗形成木数量随着海拔的升高而增加。在其分布的下限、中部和上限,林窗形成木的数量平均数分别为1.4、2.3、3.1个。(4)太白红杉林林窗边界木的高度和胸径大小随海拔升高而降低或减小,但边界木个体与林内的个体平均大小相一致。在太白红杉分布的下限、中部和上限,林窗边界木的平均高度分别为6.15 m、4.9 m、3.3 m:平均胸径分别为18.0 cm、16.2 cm和14.8 cm。(5)在太白红杉林分布的下限,形成太白红杉+巴山冷杉(Abies fargesii)混交林,群落中巴山冷杉有大量的幼苗和幼树,但太白红杉占据着群落中的优势地位。群落中林窗内太白红杉幼苗、幼树的存活率相对较高,而巴山冷杉长期处于幼苗、幼树阶段,只有出现干扰形成林窗后,巴山冷杉才可能长成为成树。(6)不同大小林窗内乔木幼苗幼树更新密度的变化,反映了太白山亚高山带主要针叶树种的更新策略与林窗大小的关系。在太白红杉分布的下限和中部,太白红杉的更新密度在中等大小(100～150 m~2)的林窗内最大;而在分布的上限,小林窗(＜50 m~2)有利于太白红杉的更新,可能由于林窗内昼夜温差太大,不利于乔木幼苗的生存,而一些灌木在林窗内大量生长也在一定程度上抑制了太白红杉的更新。巴山冷杉更新密度随着林窗面积的增加而逐渐减少,呈现出单调递减趋势。可能较大的林窗有更强烈的光照,不利于耐阴植株巴山冷杉的生长。(7)林窗内太白红杉的更新密度明显高于林冠下的更新密度。而巴山冷杉在林窗和林内的更新密度不存在明显的差异。这种差异决定了未来上层优势树种组成的差异,林窗和林内幼苗更新及组成的差异也从另一个方面说明了林窗在推动森林更新及维持森林物种多样性等方面的重要性。更多还原

【Abstract】 Larix chinensis is mainly distributed in Mt.Taibai, Shannxi, and scattered in other areas, such as Mt.Guangtou in Changan County, Niubeiliang National Reserve in Zhashui County and Changqing National Nature Reserve in Yang County. L. chinensis is the only tree that forms the pure forest which has special functions to conserve water, firm mountain stone and maintain water and soil at the timberline area. Forest gap disturbance, an important small scale disturbance, often occurs in forest community. It is one of the most important drives for maintaining of forest ecosystem, and has important influence on forest structure, cycle and regeneration. In this paper, through the research on characters of L. chinensis forest gap and it’s effect on community regeneration, reveals the characters of distribution and formation of L. chinensis gap. All these will provide the scientific basis for studying the natural regeneration, tending and management measures of L. chinensis community in Qin Ling. Setting a sample plot size of 100 m×100 m at high-altitude, mid-altitude, low-altitude on Taibai Mountain, Qin Ling ,where is the concentrated distribution of L. chinensis. Count the quantities of forest gap in each sample plot, investigate characteristic index of each forest gap and the numbers of seedlings, saplings and it’s characteristic index. At the same time, set a sample plot nearby the same area, investigated the characteristic index such as quantities of all arbor species (besides seedlings and saplings) , height, diameter, crown width. Based on statistics of techniques and analysis, we get results as follows:①In low-altitude transect and in mid-altitude, the gap size class distributions were also similar. In high-altitude, most of the gaps size class distributions were large. The proportion of gap size account for 9.4%, 34.4%, 30.4% of sample area in low-altitude , mid-altitude, high-altitude respectively. The proportion of extended gaps size account for 22.6%, 67.0%, 54.6%.②The main manners of gap formation are stem breakage of overwood, branch break, uprooting or standing death. As the altitude becomes higher, the manners of gap formation convert from standing death to stem breakage. The manners of gap formation convert from sole way to many ways gradually.③With the increase of altitude, the number of gap makers of I. chinensis increases. The average number of gap makers are 1.4, 2.3, 3.1 on it’s distribution of low-altitude , mid-altitude and high-altitude.④There were significant differences in the size and number of seedlings among the different sized gaps and understorey. The average height and average dbh are 6.15 m. 4.9 m, 3.3 m and 18.0 cm, 16.2 cm, 14.8 cm on it’s distribution of low-altitude, mid-altitude and high-altitude.⑤Larix chinensis + Abies fargesii mixed forest forms on the distribution of low-altitude of I. chinensis. There are great amount of seedlings and saplings of A. fargesii, but L. chinensis occupy dominant position in the community. The survival rate of L. chinensis seedlings and saplings is better than A. fargesii which has already been in the seedlings and saplings stage. It only become mature tree when gaps appear. ⑥The change of regeneration density of seedlings and saplings in gaps with different sizes reflects the relationship between updating strategy of coniferous species and gap size. On the distribution of low-altitude and mid-altitude, the regeneration density of mid-altitude is bigger than low-altitude, on the distribution of high-altitude, small gap is good for regeneration, maybe the diurnal temperature difference is too large for seedling survival. And the shrub mass growth would inhibit the regeneration. A. fargesii regeneration density is along with the gap area increases, but reduces gradually, presents the monotone decreasing tendency. Possibly big gap has a more intense illumination that not favor for A. fargesii which is shade-tolerant.⑦The regeneration density in gap is higher than canopy. There are not obvious differences of regeneration density between gap and canopy for A. fargesii. This kind of difference has decided the difference of upper advantage trees composition in future. The difference of seedlings regeneration and composition between in gap and canopy explains the importance of gap in promoting forest regeneration and maintenance species diversity.更多还原