Department of Zoology, University of Oxford, Oxford, OX1 3PS, UK.
Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK.
New Phytol. 2018 Nov;220(3):799-810. doi: 10.1111/nph.15338. Epub 2018 Jul 26.
Insect herbivores cause substantial changes in the leaves they attack, but their effects on the ecophysiology of neighbouring, nondamaged leaves have never been quantified in natural canopies. We studied how winter moth (Operophtera brumata), a common herbivore in temperate forests, affects the photosynthetic and isoprene emission rates of its host plant, the pedunculate oak (Quercus robur). Through a manipulative experiment, we measured leaves on shoots damaged by caterpillars or mechanically by cutting, or left completely intact. To quantify the effects at the canopy scale, we surveyed the extent and patterns of leaf area loss in the canopy. Herbivory reduced photosynthesis both in damaged leaves and in their intact neighbours. Isoprene emission rates significantly increased after mechanical leaf damage. When scaled up to canopy-level, herbivory reduced photosynthesis by 48 ± 10%. The indirect effects of herbivory on photosynthesis in undamaged leaves (40%) were much more important than the direct effects of leaf area loss (6%). If widespread across other plant-herbivore systems, these findings suggest that insect herbivory has major and previously underappreciated influences in modifying ecosystem carbon cycling, with potential effects on atmospheric chemistry.
昆虫食草动物会对它们所攻击的叶子造成显著的变化，但它们对相邻、未受损叶子的生态生理学的影响在自然树冠层中从未被量化过。我们研究了冬季蛾（Operophtera brumata），一种温带森林中的常见食草动物，如何影响其宿主植物——栓皮栎（Quercus robur）的光合作用和异戊二烯排放速率。通过一项操纵实验，我们测量了被毛毛虫或机械切割损伤的、或完全未受损的嫩枝上的叶子。为了量化树冠尺度的影响，我们调查了树冠中叶片面积损失的范围和模式。食草动物既降低了受损叶片的光合作用，也降低了其未受损邻居的光合作用。机械叶片损伤后，异戊二烯排放速率显著增加。将其扩展到树冠水平，食草动物会降低 48±10%的光合作用。食草动物对未受损叶片光合作用的间接影响（40%）比叶片面积损失的直接影响（6%）重要得多。如果在其他植物-食草动物系统中普遍存在，这些发现表明昆虫食草动物对改变生态系统碳循环具有重大且以前未被充分认识的影响，可能对大气化学产生潜在影响。
