Suárez Esteban R, Fahey Timothy J, Yavitt Joseph B, Groffman Peter M, Bohlen Patrick J
Department of Natural Resources, Cornell University, Ithaca, New York 14853, USA
Ecol Appl. 2006 Feb;16(1):154-65. doi: 10.1890/04-0788.
A field study was conducted to evaluate the effects of exotic earthworm invasions on the rates of leaf litter disappearance in a northern hardwood forest in southcentral New York, USA. Specifically, we assessed whether differences in litter quality and the species composition of exotic earthworm communities affected leaf litter disappearance rates. Two forest sites with contrasting communities of exotic earthworms were selected, and disappearance rates of sugar maple and red oak litter were estimated in litter boxes in adjacent earthworm-free, transition, and earthworm-invaded plots within each site. After 540 days in the field, 1.7-3 times more litter remained in the reference plots than in the earthworm-invaded plots. In the earthworm-invaded plots, rates of disappearance of sugar maple litter were higher than for oak litter during the first year, but by the end of the experiment, the amount of sugar maple and oak litter remaining in the earthworm-invaded plots was identical within each site. The composition of the earthworm communities significantly affected the patterns of litter disappearance. In the site dominated by the anecic earthworm Lumbricus terrestris and the endogeic Aporrectodea tuberculata, the percentage of litter remaining after 540 days (approximately 17%) was significantly less than at the site dominated by L. rubellus and Octolasion tyrtaeum (approximately 27%). This difference may be attributed to the differences in feeding behavior of the two litter-feeding species: L. terrestris buries entire leaves in vertical burrows, whereas L. rubellus usually feeds on litter at the soil surface, leaving behind leaf petioles and veins. Our results showed that earthworms not only accelerate litter disappearance rates, but also may reduce the differences in decomposition rates that result from different litter qualities at later stages of decay. Similarly, our results indicate that earthworm effects on decomposition vary with earthworm community composition. Furthermore, because earthworm invasion can involve a predictable shift in community structure along invasion fronts or through time, the community dynamics of invasion are important in predicting the spatial and temporal effects of earthworm invasion on litter decomposition, especially at later stages of decay.
在美国纽约中南部的一个北方硬木森林中，开展了一项实地研究，以评估外来蚯蚓入侵对落叶消失速率的影响。具体而言，我们评估了凋落物质量和外来蚯蚓群落的物种组成差异是否会影响落叶消失速率。选择了两个具有不同外来蚯蚓群落的森林地点，并在每个地点相邻的无蚯蚓、过渡和蚯蚓入侵地块的凋落物箱中估计糖枫和红橡凋落物的消失速率。在田间放置540天后，对照地块中剩余的凋落物比蚯蚓入侵地块中的多1.7至3倍。在蚯蚓入侵地块中，第一年糖枫凋落物的消失速率高于橡树叶凋落物，但到实验结束时，每个地点的蚯蚓入侵地块中剩余的糖枫和橡树叶凋落物量相同。蚯蚓群落的组成显著影响了凋落物消失的模式。在以表栖蚯蚓陆正蚓和内栖蚯蚓多毛环爪蚓为主的地点，540天后剩余的凋落物百分比（约17%）显著低于以红色爱胜蚓和微小双胸蚓为主的地点（约27%）。这种差异可能归因于这两种取食凋落物的物种在取食行为上的差异：陆正蚓将整片叶子埋在垂直洞穴中，而红色爱胜蚓通常在土壤表面取食凋落物，留下叶柄和叶脉。我们的结果表明，蚯蚓不仅加速了凋落物的消失速率，而且还可能减少了腐烂后期因不同凋落物质量而导致的分解速率差异。同样，我们的结果表明，蚯蚓对分解的影响因蚯蚓群落组成而异。此外，由于蚯蚓入侵可能涉及沿入侵前沿或随时间推移在群落结构上的可预测变化，入侵的群落动态对于预测蚯蚓入侵对凋落物分解的时空影响非常重要，尤其是在腐烂后期。
