Feller Ilka C, Chamberlain Anne
Smithsonian Environmental Research Center, 647 Contees Wharf Road, Edgewater, MD 21037, USA.
Oecologia. 2007 Sep;153(3):607-16. doi: 10.1007/s00442-007-0760-9. Epub 2007 Jun 14.
Complex gradients in forest structure across the landscape of offshore mangrove islands in Belize are associated with nutrient deficiency and flooding. While nutrient availability can affect many ecological processes, here we investigate how N and P enrichment interact with forest structure in three distinct zones (fringe, transition, dwarf) to alter patterns of herbivory as a function of folivory, loss of yield, and tissue mining. The effects of nutrient addition and zone varied by functional feeding group or specific herbivore. Folivory ranged from 0 to 0.4% leaf area damaged per month, but rates did not vary by either nutrient enrichment or zone. Leaf lifetime damage ranged from 3 to 10% of the total leaf area and was caused primarily by the omnivorous tree crab Aratus pisonii. We detected two distinct spatial scales of response by A. pisonii that were unrelated to nutrient treatment, i.e., most feeding damage occurred in the fringe zone and crabs fed primarily on the oldest leaves in the canopy. Loss of yield caused by the bud moth Ecdytolopha sp. varied by zone but not by nutrient treatment. A periderm-mining Marmara sp. responded positively to nutrient enrichment and closely mirrored the growth response by Rhizophora mangle across the tree height gradient. In contrast, a leaf-mining Marmara sp. was controlled by parasitoids and predators that killed >89% of its larvae. Thus, nutrient availability altered patterns of herbivory of some but not all mangrove herbivores. These findings support the hypothesis that landscape heterogeneity of the biotic and abiotic environment has species-specific effects on community structure and trophic interactions. Predicting how herbivores respond to nutrient over-enrichment in mangrove ecosystems also requires an assessment of habitat heterogeneity coupled with feeding strategies and species-specific behavior measured on multiple scales of response.
伯利兹近海红树林岛屿景观中复杂的森林结构梯度与养分缺乏和洪水有关。虽然养分有效性会影响许多生态过程，但在这里我们研究了氮和磷的富集如何与三个不同区域（边缘、过渡、矮林）的森林结构相互作用，以改变食草模式，该模式是叶食性、产量损失和组织挖掘的函数。养分添加和区域的影响因功能取食组或特定食草动物而异。叶食性范围为每月0至0.4%的叶面积受损，但速率不受养分富集或区域的影响。叶片终生损伤范围为总叶面积的3%至10%，主要由杂食性树蟹Aratus pisonii造成。我们检测到A. pisonii有两种不同的空间响应尺度，这与养分处理无关，即大多数取食损伤发生在边缘区域，螃蟹主要取食树冠中最老的叶子。芽蛾Ecdytolopha sp.造成的产量损失因区域而异，但不受养分处理的影响。一种皮部挖掘的Marmara sp.对养分富集有积极响应，并且在树高梯度上紧密反映了红树Rhizophora mangle的生长响应。相比之下，一种叶部挖掘的Marmara sp.受寄生蜂和捕食者控制，这些寄生蜂和捕食者杀死了超过89%的幼虫。因此，养分有效性改变了一些但不是所有红树林食草动物的食草模式。这些发现支持了这样的假设，即生物和非生物环境的景观异质性对群落结构和营养相互作用具有物种特异性影响。预测食草动物如何应对红树林生态系统中的养分过度富集还需要评估栖息地异质性，以及在多个响应尺度上测量的取食策略和物种特异性行为。
