Section of Ecology, Department of Biology, University of Turku, Turku, 20014, Finland.
Glob Chang Biol. 2015 Jan;21(1):106-16. doi: 10.1111/gcb.12682. Epub 2014 Aug 1.
Knowledge of the latitudinal patterns in biotic interactions, and especially in herbivory, is crucial for understanding the mechanisms that govern ecosystem functioning and for predicting their responses to climate change. We used sap-feeding insects as a model group to test the hypotheses that the strength of plant-herbivore interactions in boreal forests decreases with latitude and that this latitudinal pattern is driven primarily by midsummer temperatures. We used a replicated sampling design and quantitatively collected and identified all sap-feeding insects from four species of forest trees along five latitudinal gradients (750-1300 km in length, ten sites in each gradient) in northern Europe (59 to 70°N and 10 to 60°E) during 2008-2011. Similar decreases in diversity of sap-feeding insects with latitude were observed in all gradients during all study years. The sap-feeder load (i.e. insect biomass per unit of foliar biomass) decreased with latitude in typical summers, but increased in an exceptionally hot summer and was independent of latitude during a warm summer. Analysis of combined data from all sites and years revealed dome-shaped relationships between the loads of sap-feeders and midsummer temperatures, peaking at 17 °C in Picea abies, at 19.5 °C in Pinus sylvestris and Betula pubescens and at 22 °C in B. pendula. From these relationships, we predict that the losses of forest trees to sap-feeders will increase by 0-45% of the current level in southern boreal forests and by 65-210% in subarctic forests with a 1 °C increase in summer temperatures. The observed relationships between temperatures and the loads of sap-feeders differ between the coniferous and deciduous tree species. We conclude that climate warming will not only increase plant losses to sap-feeding insects, especially in subarctic forests, but can also alter plant-plant interactions, thereby affecting both the productivity and the structure of future forest ecosystems.
生物相互作用（尤其是食草作用）的纬度格局知识对于理解控制生态系统功能的机制以及预测它们对气候变化的响应至关重要。我们以吸食汁液的昆虫为模型组，来检验以下两个假说：在北方森林中，植物-食草动物相互作用的强度随纬度的增加而减弱；这种纬度模式主要由仲夏温度驱动。我们采用了重复采样设计，在 2008 年至 2011 年间，从北欧（59°至 70°N，10°至 60°E）的五个纬度梯度（每条梯度长 750-1300 公里，每个梯度有 10 个地点）的四种森林树上定量采集和鉴定了所有吸食汁液的昆虫。在所有研究年份中，所有梯度都观察到吸食汁液的昆虫多样性随纬度的相似减少。在典型夏季，食草昆虫的负荷（即单位叶生物量上的昆虫生物量）随纬度的降低而降低，但在异常炎热的夏季增加，且在温暖夏季与纬度无关。对所有地点和年份的综合数据分析表明，吸食汁液昆虫的负荷与仲夏温度之间存在拱形关系，在云杉中达到峰值 17°C，在欧洲赤松、欧洲白桦和欧洲山杨中达到峰值 19.5°C，在欧洲黑杨中达到峰值 22°C。根据这些关系，我们预测，南部北方森林中森林树木因吸食汁液而损失的比例将比当前水平增加 0-45%，亚北极森林将增加 65-210%，夏季温度每升高 1°C。在针叶树和阔叶树种之间，温度与吸食汁液昆虫的负荷之间的关系不同。我们得出结论，气候变暖不仅会增加吸食汁液的昆虫对植物的损害，尤其是在亚北极森林，而且还会改变植物-植物的相互作用，从而影响未来森林生态系统的生产力和结构。
