Effects of proximity of stems and tree diameters on fine root density in plantations
Effects of proximity of stems and tree diameters on fine root density in plantations
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发表时间：
2005
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通讯作者：
Chen Guang;He Zong
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作者：
Chen Guang;He Zong
通常认为封闭森林中的细根密度与距树的距离和树的大小无关。在福建三明的川槠（CK）和杉木（CF）人工林中进行了研究，通过将细根密度与最近的 3 棵树的距离和直径联系起来，获得细根密度的水平分布信息。 2000年7月，使用岩心（内径6.8厘米，长度100厘米）测量根密度。收集了大量采样点（CK中41个，CF中40个）。在每个采样点测量到最近的3棵树的距离以及这些树的胸径。本研究对所得数据进行了统计分析，以确定对抽样设计的影响。 CK和CF的平均细根密度分别为3.266 t/hm~2和2.048 t/hm~2。样品中细根密度的变异性很大，CK 的 Cv% 为 37.3%，CF 的 Cv% 为 42.8%。根密度频率符合正态分布（p0.05）。在两片森林中，细根密度与距最近的两棵树的距离显着负相关，其中距最近的一棵树的距离 R~2 最高。 CK的细根密度与最近树的胸径呈显着正相关，而CF的根密度与树径之间不存在显着关系。使用逐步线性回归，到最近的树的距离和胸径可以解释 CK 根密度变化的 41.0%，到最近的 2 棵树的距离可以解释 CF 根密度变化的 40.6%。由于这些人工林中存在一定的细根分布水平模式，因此当在距树木恒定距离或特定大小的树木周围选择采样点时，细根密度评估可能会出现系统误差。然而，使用分层随机设计或随机抽样设计可以轻松避免这些系统误差。如果要研究根密度与其他因素（例如树木距离或大小）之间的关系本身，那么即使在同质土壤中也需要更多数量的采样点。
The fine root density in a closed forest is usually considered to be independent of distance from the tree and of the tree size. Studies have been carried out in a Castanopsis kawakamii (CK) and a Cunninghamia lanceolata (CF) plantation in Sanming, Fujian, to obtain information on horizontal distribution of fine root densities by relating fine root densities to proximity and diameter of the nearest 3 trees. Root densities were measured using a core (6.8 cm inner diameter, 100 cm length) in July 2000. A large number of sampling points (41 in the CK and 40 in the CF) were collected. The distances to the nearest 3 trees and the diameter at breast of these trees were measured at each sampling point. The resulting data were statistically analyzed in the present study, to ascertain the implications for sampling design. Mean fine-root density amounted to 3.266 t/hm~2 and 2.048 t/hm~2 for the CK and the CF, respectively. There was large variability in fine root density in the samples, with a Cv % of 37.3% for the CK and of 42.8% for the CF. The frequency of root density fitted well with a normal distribution (p0.05). In the two forests, fine root densities were significantly negatively related to either of the distances to the nearest 2 trees, with the distance to the nearest one having the highest R~2. Fine root density of the CK showed significant positive relation to the DBH of the nearest tree, while no significant relationship were found between root density and tree size in the CF. Using the stepwise linear regression, the distance to and the DBH of the nearest tree together could explain 41.0% of the variation in root density of the CK, and the distances to the nearest 2 trees together could explain 40.6% of the variation in root density of the CF. Since a certain horizontal pattern of fine root distribution occurred in these plantations, systematic errors in the assessment of fine root density can arise when sampling points are chosen at a constant distance from trees or around trees of certain size. However, these systematic errors can be avoided easily, using a stratified random design or a random sampling design. If the relation between root density and other factors (e.g. with tree distance or size) itself is to be investigated, then even larger numbers of sampling points are needed even in homogenous soils.