Canopy Gaps and the Landscape Mosaic in a Coastal Temperate Rain Forest
Canopy Gaps and the Landscape Mosaic in a Coastal Temperate Rain Forest
复制标题
DOI：
10.2307/2265594
复制
发表时间：
1996-06
期刊：
影响因子：
4.8
通讯作者：
K. Lertzman;G. Sutherland;A. Inselberg;S. Saunders
中科院分区：
文献类型：
--
作者：
K. Lertzman;G. Sutherland;A. Inselberg;S. Saunders
我们研究了加拿大不列颠哥伦比亚省西南部克拉阔湾温带雨林不同林龄和场地湿度级别的树冠间隙。我们在三个分辨率级别上测试了对景观马赛克的预测：整个森林、间隙和间隙制造者。除了由优势树木的斑片死亡（发育差距）引起的树冠间隙外，我们还描述了由土壤和地形特征引起的间隙的普遍性和特征。大约 56% 的森林面积在某种程度上受到树冠开口（树冠间隙 + 扩大的间隙）的影响，所有地点平均有 30% 的森林面积处于树冠间隙（14% 为发育树冠间隙，16% 为土壤树冠间隙）。在采样最密集的生物地理气候分区内，73% 的差距源于发育。大多数土壤间隙是由河道造成的。尽管不同林分年龄等级的发育冠层间隙百分比面积相似，但间隙和间隙制造者在老林中比在成熟林中更常见。大多数发育差距是由一棵以上树木的死亡造成的：96%的发育差距有一个以上的差距制造者，50%有三个或更多。成熟林分的每个间隙中的间隙制造者数量明显高于老林分。因此，古老森林以许多小间隙为主，而成熟森林则以较少的大间隙为主。较干燥和湿润的场地，每个间隙的间隙制造者比中湿场地的间隙制造者要多。发育差距中差距制造者的衰退类别数量随着每个差距的差距制造者数量的增加而增加，这表明较大的差距代表了时间上分开的不同死亡事件的综合影响，而不是单个大事件的影响。发育差距中的间隙制造者在衰退类别范围内广泛且均匀地分布，这表明间隙制造者的招募是连续的模式，而不是更大的偶发性死亡事件。折断树干和站立死亡是间隙制造者最常见的死亡方式，合计占所有间隙制造者死亡率的 76%。在成熟林和老年林中，连根拔起是最不常见的间隙制造者死亡方式（分别为 23.6% 和 15.6%；占所有间隙制造者的 20.6%），并且在干燥和潮湿的地点，拔除比在湿地更常见。这些间隙相结构和间隙形成过程的总体趋势与在不列颠哥伦比亚省海岸其他地方收集的间隙和森林年龄结构的数据一致，表明小规模、低强度的扰动在不列颠哥伦比亚省沿海的古老森林中很常见。我们估计，在没有大规模干扰的情况下，这片森林的周转时间在 350 至 950 年之间，导致整个景观马赛克普遍存在晚期演替特征。旨在模拟这些森林的自然干扰状况的造林实践应在连续的森林基质中创造 3-10 棵树的小间隙，并应在管理的森林内保留大量的后期演替特征。
We studied canopy gaps over a range of stand ages and site moisture classes in the temperate rain forest of Clayoquot Sound, southwestern British Columbia, Canada. We tested predictions about the landscape mosaic at three levels of resolution: the forest as a whole, gaps, and gapmakers. In addition to canopy gaps arising from the patchy mortality of dominant trees (developmental gaps), we described the prevalence and characteristics of gaps arising from edaphic and topographic features. Roughly 56% of the forest area is influenced to some degree by canopy openings (canopy gap + expanded gap), with 30% of forest area in canopy gaps averaged over all sites (14% developmental canopy gaps and 16% in edaphic canopy gaps). Within the most intensively sampled biogeoclimatic subzone, 73% of gaps were developmental in origin. The majority of edaphic gaps result from streamcourses. Though percent area in developmental canopy gaps was similar across stand age classes, gaps and gapmakers were more common in old growth than in mature stands. Most developmental gaps resulted from the mortality of more than one tree: 96% of the developmental gaps had more than one gapmaker, and 50% had three or more. Mature stands had a significantly higher number of gapmakers per gap than old-growth stands. Old-growth forests were thus dominated by many small gaps and mature forests by fewer larger gaps. Drier and wetter sites had more gapmakers per gap than did stands on mesic sites. The number of decay classes of gapmakers in developmental gaps increases with number of gapmakers per gap, indicating that larger gaps represent the combined effects of distinct mortality events separated in time, rather than single large events. Gapmakers in developmental gaps were distributed broadly and evenly over the range of decay classes, suggesting a continuous pattern of recruitment of gapmakers rather than larger episodic mortality events. The snapping of boles and standing death were the most common modes of gapmaker mortality, together accounting for 76% of the mortality of all gapmakers. Uprooting was the least common mode of gapmaker mortality in both mature and old-growth forests (23.6% and 15.6%, respectively; 20.6% of all gapmakers) and uprooting was more common in drier and wetter sites than in mesic sites. These general trends in gap-phase structure and gap formation processes are consistent with data on gaps and forest age structure collected elsewhere on the British Columbia coast, suggesting that a regime of small-scale, low-intensity disturbance is common in the old-growth forests of coastal British Columbia. We estimate that, in the absence of large-scale disturbances, turnover time for this forest is between 350 and 950 yr, resulting in ubiquitous late successional character throughout the landscape mosaic. Silvicultural practices intended to emulate the natural disturbance regime of these forests should create small gaps of 3-10 trees in an otherwise continuous forest matrix and should retain substantial late-successional characteristics within managed forests.