Density effects at multiple scales in an experimental plant population
Density effects at multiple scales in an experimental plant population
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DOI：
10.1111/j.1365-2745.2007.01226.x
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发表时间：
2007-05-01
影响因子：
5.5
通讯作者：
Kunin, William E.
中科院分区：
文献类型：
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作者：
Gunton, Richard M.;Kunin, William E.
在无根生物中，种群中的每个个体经历不同的局部同比密度，并且该密度本身将根据测量的尺度而变化（仅在粗尺度下收敛于“平均场”种群密度）因此，密度对任何生态过程（如竞争、草食、死亡）的影响可能是尺度特异性的，不同的过程可能在不同的空间尺度上响应密度在4个空间尺度（边长分别为16 cm、80 cm、4 m和20 m）下，采用不同密度的田间试验方法，研究了不同密度条件下的黑松叶；收集了生长、草食、开花和成活的数据。采用赤池信息准则确定哪个量表在密度与各响应变量之间表现出最强的关系各变量对密度的响应在不同尺度下呈现峰值，且呈不同的正、负、非单调关系。有些（如哺乳动物的食草性）在不同尺度上表现出截然不同的反应生长速率对同种密度的响应非常小，这可能是由于来自周围植被的种内和种间竞争的平衡效应。然而，第一年存活率的25%的变化可以用一个模型来解释，这个模型包括了80厘米尺度的密度的积极影响草食主要以蛞蝓为主，在4 m和20 m尺度上对密度呈负响应，符合资源限制、迁移和空间尺度的假设。食草哺乳动物在80 cm和20 m尺度上表现出不同的反应模式。草食反应和生存反应之间的一致性表明草食是导致死亡的重要原因因此，植物种群格局可以反映密度效应在不同特征尺度上的相互作用。如果不能认识到密度依赖于尺度，那么关于空间结构种群的密度依赖的概括可能是误导性的。
1 In sessile organisms, each individual in a population experiences a different local conspecific density, and this density itself will vary depending on the scale at which it is measured (converging on a 'mean field' population density only at coarse scales).2 The effects of density on any ecological process (e.g. competition, herbivory, mortality) may therefore be scale-specific, and different processes may respond to density at different spatial scales.3 A field experiment was set up in which focal Silene latifolia plants were subjected to a range of densities at each of four spatial scales (squares with sides of 16 cm, 80 cm, 4 m and 20 m); data were collected on growth, herbivory, flowering and survival. The Akaike information criterion was used to determine which scale displayed the strongest relationship between density and each response variable.4 The variables showed peak responses to density at different scales and with various relationships (positive, negative and non-monotonic). Some (e.g. herbivory by mammals) showed contrasting responses at different scales.5 Growth rate showed surprisingly little response to conspecific density, presumably owing to balancing effects of intra-specific and inter-specific competition from the surrounding vegetation. However, 25% of variation in first-year survival was explained by a model including a positive effect of density at the 80-cm scale.6 Herbivory was mainly due to slugs and showed negative responses to density at the 4-m and 20-m scales, in accordance with hypotheses about resource limitation, mobility and spatial scaling. Mammal herbivory responded with contrasting patterns at the 80-cm and 20-m scales. Congruence between the responses of herbivory and survival suggest that herbivory was an important cause of mortality.7 Plant population patterns may thus reflect density effects interacting at different characteristic scales. Generalizations about density-dependence in spatially structured populations may be misleading if they fail to recognize that density is scale-dependent.