Uriarte M
Section of Ecology and Systematics, Corson Hall, Cornell University, Ithaca, NY 14853, USA e-mail:
Oecologia. 2000 Mar;122(4):521-528. doi: 10.1007/s004420050975.
Consumers can mediate the composition of plant communities and alter ecosystem processes. Although herbivores usually increase N availability in the short term, they might decrease it in the long term. I investigated the long-term effect of insect herbivores on leaf tissue quality and soil N availability in goldenrod (Solidago altissima) fields using two approaches: (1) I compared plots from which herbivores had been excluded for 17 years with adjacent plots that had experienced normal levels of herbivory, and (2) I examined a chronosequence of nine goldenrod fields representing three successional stages: early, middle, and late. These parallel approaches showed that, in the long term, herbivores decrease the quality of leaf litter and soil N availability in goldenrod fields. These long-term effects appear to compensate for various short-term effects that increase N availability in the soil (e.g., added frass, increased light penetration). Furthermore, herbivores decrease leaf litter quality and N availability by reducing the quality of leaf tissue within the same species. This pattern may result from insect herbivores preferentially grazing on plants with a high N content thereby increasing the amount of recalcitrant litter over the course of succession.
消费者能够调节植物群落的组成并改变生态系统过程。虽然食草动物通常在短期内会增加氮的有效性，但从长期来看它们可能会降低其有效性。我采用两种方法研究了食草昆虫对一枝黄花（Solidago altissima）田中叶组织质量和土壤氮有效性的长期影响：（1）我将食草动物被排除达17年之久的样地与经历正常食草水平的相邻样地进行了比较；（2）我考察了代表三个演替阶段（早期、中期和晚期）的九个一枝黄花田的时间序列。这些并行的方法表明，从长期来看，食草动物会降低一枝黄花田中叶凋落物的质量和土壤氮有效性。这些长期影响似乎抵消了各种使土壤中氮有效性增加的短期影响（例如，添加粪便、增加光照穿透）。此外，食草动物通过降低同一物种内叶组织的质量来降低叶凋落物质量和氮有效性。这种模式可能是由于食草昆虫优先啃食含氮量高的植物，从而在演替过程中增加了难分解凋落物的数量。
