The effects of environment and life stage on Quercus abundance in the eastern deciduous forest, USA: are sapling densities most responsive to environmental gradients?
The effects of environment and life stage on Quercus abundance in the eastern deciduous forest, USA: are sapling densities most responsive to environmental gradients?
复制标题
环境和生命阶段对美国东部落叶林栎属丰度的影响：树苗密度对环境梯度最敏感吗？
DOI：
10.1016/j.foreco.2004.06.023
复制
发表时间：
2004
影响因子：
3.7
通讯作者：
W. Carson
中科院分区：
文献类型：
--
作者：
Rachel J. Collins;W. Carson
大多数描述树种在环境梯度上的分布的研究只关注成虫的丰度。这种方法可能会忽略年轻生命阶段（即幼苗和幼树）的反应，因此可能无法识别对特定环境梯度（即随景观变化的场地特征，例如海拔或坡向）最敏感的生命阶段。或者，幼苗和幼树的丰度可能与环境梯度无关，并且可能完全取决于成虫的丰度。为了有效管理东部阔叶林，促进物种组成，从而最大限度地提高经济或生态价值，我们需要了解场地特征和成虫丰度在所有生命阶段的相对作用。为了满足这一需求，我们研究了五种场地特征（坡向、坡度、场地指数、林龄和海拔）与三种橡树（红栎、白栎和白栎）的幼苗、幼树和成树丰度之间的关系。我们通过对大块土地（500 平方米）的幼苗、幼树和成虫进行普查，并量化弗吉尼亚州中北部莫农加希拉国家森林 21 个林分的当地立地特征，评估了这些关系。成年白橡树密度在西南坡达到峰值（R2= 0.24）；成年栗橡树密度在山脊顶部达到峰值 (R2= 0.58)；成年北方红橡树的密度与任何地点特征均不相关（R2 = 0.00）。白橡树和栗橡树幼苗的密度与立地特征和幼苗密度的组合高度相关（R2分别= 0.75和0.81），而北方红橡树的密度仅与立地特征高度相关（R2= 0.70）。对于幼苗，白橡树和栗橡树的密度仅与成年丰度相关（R2= 0.53、0.56），而北方红橡树的密度仅与立地特征相关（R2= 0.45）。这些数据表明，在没有干扰的情况下，地点特征对这些橡树在幼苗阶段的丰度模式具有最强的影响。对于这三个物种中的每一个，幼苗、幼树和成年密度都与不同的因素子集相关，这意味着不同的生物和非生物条件促进了每个生命阶段的峰值密度。这种模式表明存在重要的“人口冲突”（sensu [Battaglia, L.L., Fore, S.A., Sharitz, R.R., 2000. 两种低地阔叶树种的幼苗出苗、存活和大小与光和水可用性的关系。J. Ecol. 88, 1041–1050]）。
Most studies that describe tree species distributions across environmental gradients focus only on the abundance of adults. This approach may overlook the response of younger life stages (i.e., seedlings and saplings) and thus may fail to identify the life stage that is most sensitive to a particular environmental gradient (i.e., site characteristics that vary across landscapes such as elevation or aspect). Alternatively, seedling and sapling abundance may be unrelated to environmental gradients and may be entirely dependent on adult abundance. In order to effectively manage eastern hardwood forests to promote species compositions that maximize economic or ecological value, we need to understand the relative roles of site characteristics and adult abundance on all life stages. To address this need, we examined the relationships between five site characteristics (aspect, slope position, site index, stand age and elevation) and the abundance of seedlings, saplings and adults of three species of oak (Quercus rubra, Quercus alba, and Quercus prinus). We assessed these relationships by censusing seedlings, saplings, and adults in large plots (500m2) and quantifying local site characteristics in 21 forest stands in the Monongahela National Forest in North Central West Virginia. Adult white oak densities peaked on southwestern slopes (R2= 0.24); adult chestnut oak densities peaked on ridge tops (R2= 0.58); and adult northern red oak densities were not correlated with any site characteristics (R2= 0.00). Densities of white oak and chestnut oak saplings were highly correlated with a combination of site characteristics and seedling densities (R2= 0.75, 0.81, respectively), and northern red oak densities were highly correlated with site characteristics solely (R2= 0.70). For seedlings, white oak and chestnut oak densities were correlated only with adult abundance (R2= 0.53, 0.56, respectively), and northern red oak densities were correlated solely with site characteristics (R2= 0.45). These data suggest that in the absence of disturbance, site characteristics have the strongest effects on abundance patterns of these oaks during the sapling stage. For each of the three species, seedling, sapling and adult densities were correlated with a different subset of factors meaning that different biotic and abiotic conditions promoted peak densities for each life stage. Such a pattern indicates that important “demographic conflicts” exist (sensu [Battaglia, L.L., Fore, S.A., Sharitz, R.R., 2000. Seedling emergence, survival and size in relation to light and water availability in two bottomland hardwood species. J. Ecol. 88, 1041–1050]).