Intraspecific variation in sapling mortality and growth predicts geographic variation in forest composition
Intraspecific variation in sapling mortality and growth predicts geographic variation in forest composition
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DOI：
10.2307/2963474
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发表时间：
1996-05-01
影响因子：
6.1
通讯作者：
Kobe, RK
中科院分区：
文献类型：
--
作者：
Kobe, RK
为了了解不同森林群落中物种组成的变化，我在三个对比地点研究了幼龄树（直径2.3-78 mm，距地面10 cm）的种特异性生长和死亡率。土壤矿物学和海拔不同的两个地点（片岩/片麻岩高地与钙质基岩山谷）位于美国康涅狄格州西北部。为了研究在更广泛的地理范围内的变化，我位于中西部密歇根州，美国的第三个网站。在这三个网站中，落叶树种（美国山毛榉，白色灰，糖枫）表现出小种内的相对径向增长率作为光可用性的函数模型的变化。引人注目的是，在密歇根州网站的径向生长的变化的一个重要组成部分可以解释最初校准的康涅狄格州网站的树苗生长模型。与落叶树种相比，万年青树种（白松和铁杉）在生长模型上表现出显著的种内差异，不同地点间的生长模型差异表现为弱光下生长的显著差异。这一结果表明，光和其他资源可以同时受到限制，并挑战李比希最小值定律在树苗生长中的应用。对于落叶树种，死亡过程在不同地点之间表现出比生长更大的差异。我发现显着的网站差异，死亡率作为最近的增长的功能，糖枫和白色灰石灰质土壤相比，在康涅狄格州的片岩/片麻岩土壤。在一般情况下，在密歇根州和高地康涅狄格网站的死亡率函数是相似的，都不同的康涅狄格州石灰质site.Community动态在三个网站的每一个被称为SORTIE的森林动力学模型，其中包括观察到的差异，幼树死亡率和生长功能之间的网站进行了模拟。使用SORTIE，仅在少年生存和增长的差异是足够的，以预测在成年树冠优势种，表现出至关重要的幼树阶段的群落dynamics.If一个物种在一个特定的网站上表现不同，它与其他物种在该网站的相互作用也将改变，可能会导致进一步的差异，在社区物种组成。物种响应不同立地条件的表现变化以及物种随后的相互作用对于了解这些森林群落的动态和组成之间的差异至关重要。
With a view toward understanding variation in species composition among different forest communities, I examined species-specific growth and mortality of juvenile trees (2.3-78 mm diameter at 10 cm above the ground) at three contrasting sites. Two sites differing in soil mineralogy and elevation (schist/gneiss uplands vs. calcareous bedrock valley) were situated in northwestern Connecticut, USA. To examine variation over a more extensive geographic scale, I located the third site in central-western Michigan, USA.Among the three sites, the deciduous species (American beech, white ash, and sugar maple) showed little intraspecific variation in models of relative radial growth rate as a function of light availability. Strikingly, a substantial component of the variation in radial growth at the Michigan site could be explained by sapling growth models originally calibrated for the Connecticut sites. In contrast to the deciduous species, the evergreen species (white pine and eastern hemlock) exhibited significant intraspecific differences in growth models between the two Connecticut sites.Intraspecific variation in growth models among sites was characterized by significantly different estimates of growth at low light. This result suggests that light and other resources can be simultaneously limiting, and challenges the application of Liebig's law of the minimum to tree sapling growth.For the deciduous species, mortality processes exhibited more variation among the sites than did growth. I found significant site differences in mortality as a function of recent growth for both sugar maple and white ash on the calcareous soils in comparison to the schist/gneiss soils in Connecticut. In general, the mortality functions at the Michigan and the upland Connecticut site were similar, and both differed from the Connecticut calcareous site.Community dynamics at each of the three sites were simulated with a model of forest dynamics called SORTIE, which incorporated observed differences in sapling mortality and growth functions among the sites. Using SORTIE, among-site differences in only juvenile survivorship and growth were sufficient to predict dominant species in the adult canopy, demonstrating the critical importance of sapling stages to community dynamics.If a species performs differently at a particular site, its interactions with other species at the site will also change, potentially contributing to further differences in community species composition. Changes in species' performance in response to different site conditions and the species' subsequent interactions are critical to understanding differences among the dynamics and compositions of these forest communities.