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森林结构是森林动态变化过程中测度时点的林分状态的高度概括和度量。随着森林可持续经营对森林精确信息的需求增加,森林空间结构研究越显重要[1-3]。林分空间结构决定林木间的竞争态势及其空间生态位,在很大程度上决定林分的稳定性、发展的可能性和经营空间的大小[4-7]。目前,在森林结构解析中,基于相邻木空间关系的林分空间结构分析方法已被广泛应用,由于其可释性、简洁性和可操作性等优点,已经广泛应用在森林类型的研究中,为结构化经营提供了科学依据[8]。森林固定监测大样地在前所未有的尺度上为研究种群动态等生态学规律和现象提供了良好的契机[9],是当前生态学研究中最活跃的领域之一[10-13]。基于最近相邻木关系的林分空间结构参数角尺度、混交度和大小比数等在国内外关于林分空间结构分析、林木竞争与优势度计算、物种多样性测度以及结构恢复重建与优化调整等研究目前主要是以1 hm2或更小面积的样地作为研究对象,在全球的森林大样地中应用较少。各国学者对位于巴拿马的BCI 50 hm2的大样地进行了大量的研究,在生物多样性的维持机制、物种的点格局和群落动态等方面产生了巨大的影响[14-17]。但对BCI 50 hm2大样地空间结构一元及二元分布特征的分析却鲜有报道。因此,作者以BCI 50 hm2大样地为研究对象,利用空间结构参数一元分布和二元分布,量化评价BCI 50 hm2大样地(2010年第7次普查)的活立木空间结构特征,探讨空间结构参数在大样地中的应用前景以及对空间结构参数理论体系进行进一步验证。
BCI 50 hm2森林大样地2010年活立木空间结构分析
Research on Spatial Structure of 50 hm2 Forest Plot at Barro Colorado Island in 2010
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摘要:
目的 以BCI 50 hm2大样地为研究对象,利用空间结构参数一元分布和二元分布,量化评价BCI 50 hm2大样地活立木整体、冠层和下层的空间结构特征。 方法 以巴拿马BCI 50 hm2森林大样地(2010年第7次调查)中所有胸径(DBH)≥ 1 cm的活立木数据为材料,采用基于相邻木关系的空间结构参数方法对其整体、冠层和下层活立木的空间结构进行分析。 结果 表明:BCI大样地第7次调查整体活立木的平均角尺度(W)为0.504,样地大部分林木处于极强度混交状态(Mi=1),比例为74.7%。样地的冠层和下层的状态与整体林分的状态相同,均处于随机分布、强度混交和中庸偏劣势的状态。冠层中几乎没有林木个体处于零度混交(Mi=0)状态。下层的大部分林木处于中高度大小比数和中高度混交度等级的组合上。样地中大部分活立木为小径级个体(1 cm≤DBH<20 cm),使得样地中大部分林木处于劣势状态。无论在整体、冠层和下层,活立木的混交度(Mi)都处于极高水平,在参照树周围的最近4株相邻木中同种个体的比例(Mi=0.00,Mi=0.25)极低。 结论 BCI大样地整体、冠层和下层活立木空间结构呈随机分布,林木的混交度极高,样地中同种个体在最近4株邻体这样的小尺度上呈现聚集分布的情况几乎不存在。 Abstract:Objective To study the forest spatial structure of the permanent 50-ha forest dynamics project plot on Barro Colorado Island (BCI), Panama. Method The seventh censuses (2010) of stems ≥ 1 cm DBH alive trees data of BCI plot was analyzed by the neighborhood-based variables of forest spatial structure, and the spatial structure of canopy trees and understory trees were compared. Result The pattern of live trees followed a random distribution (W=0.504) in the whole plot, 74.7% of the live trees in the state of high mingling degree, few individuals in the status of low mingling degree (Mi=0). Most of understory trees were in higher dominance degree and superior status of mingling. Large numbers of individuals in the plot were small trees (1 cm ≤ DBH < 20 cm), to this degree, they were in a status of disadvantage and belonged to inferior trees.Regardless live trees in the whole plot, the canopy or the understory, almost all individuals were in superior mingling status. At the scale of four neighboring trees around the reference tree within the whole plot, the ratio of conspecific neighbor trees (Mi=0, Wi=0.25) closed to zero. This indicated that the aggregate distribution of conspecific individuals in such a small scale was non-existence. Conclusion The forest was in a state of high mingling.More than half of the trees in the plot followed a random pattern, the trees with different dominance degrees had a similar frequency. It is suggested that the aggregate distribution of conspecific individuals in such a small scale (four neighboring trees around the reference tree) is non-existence. -
Key words:
- BCI plot
- / spatial structure
- / bivariate distribution
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