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Variations in tree growth provide limited evidence of species mixture effects in Interior West USA mixed‐conifer forests
Journal of Ecology ( IF 5.3 ) Pub Date : 2020-10-09 , DOI: 10.1111/1365-2745.13523 Christopher E. Looney 1 , Wilfred J. Previant 2 , Linda M. Nagel 1
中文翻译：
树木生长的变化提供了有限的证据，证明了美国西部内陆混合针叶林的物种混合效应
更新日期：2020-10-09
Journal of Ecology ( IF 5.3 ) Pub Date : 2020-10-09 , DOI: 10.1111/1365-2745.13523 Christopher E. Looney 1 , Wilfred J. Previant 2 , Linda M. Nagel 1
Affiliation
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- In mixed stands, species complementarity (e.g. facilitation and competition reduction) may enhance forest tree productivity. Although positive mixture effects have been identified in forests world‐wide, the majority of studies have focused on two‐species interactions in managed systems with high functional diversity. We extended this line of research to examine mixture effects on tree productivity across landscape‐scale compositional and environmental gradients in the low functional diversity, fire‐suppressed, mixed‐conifer forests of the U.S. Interior West.
- We investigated mixture effects on the productivity of Pinus ponderosa, Pseudotsuga menziesii and Abies concolor. Using region‐wide forest inventory data, we created individual‐tree generalized linear mixed models and examined the growth of these species across community gradients. We compared the relative influences of stand structure, age, competition and environmental stress on mixture effects using multi‐model inference. We analysed growth of neighbouring tree species to infer whether a mixture effect in a single species translated to the stand‐level.
- We found support for a positive mixture effect in P. menziesii, although our results were equivocal in light of a weaker but still plausible alternative model. Growth of P. menziesii neighbouring species in mixed stands declined or held constant depending on aridity, suggesting that a positive mixture effect in P. menziesii does not necessarily extend to the stand level. We found no evidence for mixture effects in P. ponderosa, A. concolor or their neighbouring species.
- Complementarity appears to have a limited influence on tree growth in the mixed‐conifer systems of the U.S. Interior West, reflecting limited functional diversity. Historical changes in stand structure following fire exclusion, particularly high stand densities, may limit the potential for positive species mixture effects. The limited species pool of Interior West forests increases the risk that, without careful management, what functional diversity exists could be lost to compositional changes resulting from stand dynamics or disturbance.
中文翻译：
树木生长的变化提供了有限的证据，证明了美国西部内陆混合针叶林的物种混合效应
- 在混交林中，物种的互补性（例如促进和减少竞争）可以提高林木生产力。尽管在全世界的森林中已经确定了积极的混合效应，但是大多数研究都集中在功能多样性高的受管理系统中的两种物种相互作用上。我们扩展了这一研究范围，以研究美国内陆西部低功能多样性，受火压抑的针叶树混交林中混合景观对景观尺度组成和环境梯度上树木生产力的影响。
- 我们研究了混合饲料对黄松，假单胞菌和冷杉生产力的影响。使用区域范围内的森林清单数据，我们创建了单个树的广义线性混合模型，并研究了这些物种在群落梯度上的生长。我们使用多模型推理比较了林分结构，年龄，竞争和环境压力对混合效应的相对影响。我们分析了邻近树种的生长，以推断单个树种中的混合效应是否转化为林分水平。
- 尽管考虑到较弱但仍可行的替代模型，我们的结果是模棱两可的，但我们发现对孟席斯体育中的阳性混合效应有支持。混交林中P. menziesii邻近物种的生长下降或保持恒定，这取决于干旱程度，这表明P. menziesii中的积极混合效应并不一定扩展到林分水平。我们发现没有证据表明黄粉假单胞菌，红曲霉或其邻近物种具有混合效应。
- 在美国内陆西部的针叶树系统中，互补性对树木生长的影响似乎有限，反映出功能多样性有限。防火排除后林分结构的历史变化，尤其是高林分密度，可能会限制产生积极的物种混合效应的潜力。西部内陆森林的物种库数量有限，这增加了以下风险：如果不谨慎管理，由于林分动态或干扰而导致的成分变化会失去现有的功能多样性。
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