Universidad de Santiago de Chile (USACH), Facultad Tecnológica, Departamento de Gestión Agraria, Chile.
Universidad de Santiago de Chile (USACH), Facultad Tecnológica, Departamento de Gestión Agraria, Chile.
Sci Total Environ. 2021 Jun 1;771:145360. doi: 10.1016/j.scitotenv.2021.145360. Epub 2021 Jan 23.
Epiphytic and epixylic lichens respond negatively to forest degradation, climate change and pollution, but those effects may depend on functional traits or interact with the stage of tree decay. Disentangling the main drivers of lichen communities remains a challenge in regions where lichens are diverse and poorly known, as the case of Patagonian temperate forests. We used a multi-scale approach to evaluate the relationship between environmental variables, tree decay stage and lichens. We sampled lichens across three increasing scales (tree ≪ site ≪ landscape) by selecting 19 landscape units, where trees in four decay stages (snags, logs, cavity trees and healthy trees) were selected within sampling plots. A total of 35 predictors were measured over different scales, including 25 remote sensing indices of forest conditions, climate and air pollutants. Structural Equation Models were used to test the causal linkages of predictors with lichens, distinguishing functional categories (size, growth and reproductive strategy). A total of 69 lichen species were recorded. Cavity trees and logs supported the largest diversity, while snags and healthy trees had the lowest diversity. Functional lichen groups responded differently to fine-scale variables, including the diameter, height, density and pH of trees. Air pollutants affected species with sexual and mixed strategies. Lichens were sensitive to precipitation, temperature and wind speed, with foliose and sexual species responding positively to the latter. The abundance of all species and macrolichens increased with tree senescence and decreased with canopy continuity. Lichens occupying snags and logs responded negatively to primary productivity and tree senescence, but positively to soil organic matter. Our findings suggest: i) the functional structure of lichen communities varies non-linearly with the wood decay process; ii) the reproductive strategy influences the sensitivity to air pollutants, iii) climate variables influence dispersal and colonization of woody substrates; and iv) forest structure/succession interacts with tree decay.
附生和石生地衣对森林退化、气候变化和污染作出负面响应，但这些影响可能取决于功能特征，或与树木腐朽阶段相互作用。在那些地衣种类多样且知之甚少的地区，如巴塔哥尼亚温带森林，厘清地衣群落的主要驱动因素仍然是一个挑战。我们采用多尺度方法评估环境变量、树木腐朽阶段和地衣之间的关系。我们通过选择 19 个景观单元，在三个递增尺度上（树≪地点≪景观）对地衣进行采样，在样方内选择四个腐朽阶段（枯立木、原木、树洞树和健康树）的树木。在不同尺度上共测量了 35 个预测因子，包括森林状况、气候和空气污染物的 25 个遥感指数。结构方程模型用于检验预测因子与地衣之间的因果关系，区分功能类别（大小、生长和繁殖策略）。共记录了 69 种地衣。树洞树和原木支持最大的多样性，而枯立木和健康树的多样性最低。功能地衣组对包括树木的直径、高度、密度和 pH 值在内的小尺度变量有不同的反应。空气污染物影响具有有性和混合策略的物种。地衣对降水、温度和风速敏感，叶状和有性物种对后两者的反应呈正相关。所有物种和大型地衣的丰度随树木衰老而增加，随冠层连续性降低而减少。占据枯立木和原木的地衣对地衣对初级生产力和树木衰老的反应呈负相关，但对土壤有机质的反应呈正相关。我们的研究结果表明：i）地衣群落的功能结构随木材腐朽过程呈非线性变化；ii）繁殖策略影响对空气污染物的敏感性，iii）气候变量影响木质基质的扩散和定植；iv）森林结构/演替与树木腐朽相互作用。
