Wang Binli, Li Ling
Department of Biological and Food Engineering, Lyuliang University, Lvliang, China.
Front Plant Sci. 2025 Jun 16;16:1508665. doi: 10.3389/fpls.2025.1508665. eCollection 2025.
Landscape-scale forest loss threats biodiversity and ecosystem functioning, but its effect on insect herbivory and pathogen infection on trees is not well understood. Little is known about how forest loss alters the effects of biotic and abiotic factors on foliar damages. Here, we assessed the relative importance of forest loss, microclimates, tree community attributes, leaf traits (e.g., specific leaf area, SLA), and arthropod abundance on insect and pathogen damage on laurel poplars in natural riparian forests in Xinjiang, China. We found that forest loss increased foliar insect herbivory directly through reduction of food availability and indirectly through reduction in tree diversity and host resistance (greater SLA). In comparison, forest loss only indirectly increased pathogen infection through lower tree diversity and associated higher SLA. Early season insect herbivory promoted later season pathogen infection. Microclimates were not associated with insect and pathogen damage, nor was arthropod abundance with insect herbivory. Our results suggest that forest loss reduced tree diversity which, in turn, changed host leaf traits and associational resistance and undermined bottom-up controls on insect herbivory and pathogen infection. Comparatively, top-down control of herbivory through predation was not significant. The positive relationship between tree diversity and host resistance (leaf traits, e.g., SLA) may be critical for maintaining forest health and ecosystem functioning in plantations and fragmented natural forests when insect pathogen damage at normal, non-outbreak conditions.
景观尺度的森林丧失威胁着生物多样性和生态系统功能，但其对树木上昆虫食草作用和病原体感染的影响尚不清楚。关于森林丧失如何改变生物和非生物因素对叶片损害的影响，人们了解甚少。在这里，我们评估了森林丧失、小气候、树木群落属性、叶片性状（例如，比叶面积，SLA）以及节肢动物丰度对中国新疆天然河岸森林中月桂杨树上昆虫和病原体损害的相对重要性。我们发现，森林丧失直接通过减少食物可利用性增加了叶片昆虫食草作用，并且间接通过降低树木多样性和宿主抗性（更高的SLA）增加了叶片昆虫食草作用。相比之下，森林丧失仅通过较低的树木多样性和相关的较高SLA间接增加了病原体感染。早期的昆虫食草作用促进了后期的病原体感染。小气候与昆虫和病原体损害无关，节肢动物丰度与昆虫食草作用也无关。我们的结果表明，森林丧失降低了树木多样性，这反过来又改变了宿主叶片性状和关联抗性，并削弱了对昆虫食草作用和病原体感染的自下而上控制。相比之下，通过捕食对食草作用的自上而下控制并不显著。在正常、非爆发条件下存在昆虫病原体损害时，树木多样性与宿主抗性（叶片性状，例如SLA）之间的正相关关系对于维持人工林和破碎化天然林中的森林健康和生态系统功能可能至关重要。
