Ulyshen Michael D
Southern Research Station, United States Department of Agriculture, Forest Service, Starkville, Mississippi, United States of America.
PLoS One. 2014 Jul 10;9(7):e101867. doi: 10.1371/journal.pone.0101867. eCollection 2014.
Saproxylic arthropods are thought to play an important role in wood decomposition but very few efforts have been made to quantify their contributions to the process and the factors controlling their activities are not well understood. In the current study, mesh exclusion bags were used to quantify how arthropods affect loblolly pine (Pinus taeda L.) decomposition rates in both seasonally flooded and unflooded forests over a 31-month period in the southeastern United States. Wood specific gravity (based on initial wood volume) was significantly lower in bolts placed in unflooded forests and for those unprotected from insects. Approximately 20.5% and 13.7% of specific gravity loss after 31 months was attributable to insect activity in flooded and unflooded forests, respectively. Importantly, minimal between-treatment differences in water content and the results from a novel test carried out separately suggest the mesh bags had no significant impact on wood mass loss beyond the exclusion of insects. Subterranean termites (Isoptera: Rhinotermitidae: Reticulitermes spp.) were 5-6 times more active below-ground in unflooded forests compared to flooded forests based on wooden monitoring stakes. They were also slightly more active above-ground in unflooded forests but these differences were not statistically significant. Similarly, seasonal flooding had no detectable effect on above-ground beetle (Coleoptera) richness or abundance. Although seasonal flooding strongly reduced Reticulitermes activity below-ground, it can be concluded from an insignificant interaction between forest type and exclusion treatment that reduced above-ground decomposition rates in seasonally flooded forests were due largely to suppressed microbial activity at those locations. The findings from this study indicate that southeastern U.S. arthropod communities accelerate above-ground wood decomposition significantly and to a similar extent in both flooded and unflooded forests. Seasonal flooding has the potential to substantially reduce the contributions of these organisms to wood decomposition below-ground, however.
腐木节肢动物被认为在木材分解过程中发挥着重要作用，但很少有人致力于量化它们对这一过程的贡献，且对控制其活动的因素也了解甚少。在本研究中，使用网袋来量化节肢动物如何在美国东南部31个月的时间里影响季节性水淹和未水淹森林中火炬松（Pinus taeda L.）的分解速率。未水淹森林中以及未受昆虫保护的原木的木材比重（基于初始木材体积）显著较低。31个月后，分别约20.5%和13.7%的比重损失可归因于水淹和未水淹森林中的昆虫活动。重要的是，处理间含水量差异极小，且单独进行的一项新测试结果表明，网袋除了排除昆虫外，对木材质量损失没有显著影响。基于木制监测桩，与水淹森林相比，未水淹森林中地下白蚁（等翅目：鼻白蚁科：散白蚁属）的活动活跃程度要高5至6倍。它们在未水淹森林中的地上活动也略为活跃，但这些差异无统计学意义。同样，季节性水淹对地上甲虫（鞘翅目）的丰富度或数量没有可检测到的影响。尽管季节性水淹极大地降低了散白蚁的地下活动，但从森林类型和排除处理之间的非显著相互作用可以得出结论，季节性水淹森林中地上分解速率降低主要是由于这些地点的微生物活动受到抑制。本研究结果表明，美国东南部的节肢动物群落显著加速了地上木材分解，在水淹和未水淹森林中的加速程度相似。然而，季节性水淹有可能大幅降低这些生物对地下木材分解的贡献。
