Carbon and nitrogen cycling immediately following bark beetle outbreaks in southwestern ponderosa pine forests
Carbon and nitrogen cycling immediately following bark beetle outbreaks in southwestern ponderosa pine forests
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DOI：
10.1016/j.foreco.2008.01.050
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发表时间：
2008-04-20
影响因子：
3.7
通讯作者：
Kaye, A.
中科院分区：
文献类型：
--
作者：
Morehouse, K.;Johns, T.;Kaye, A.
树皮甲虫的侵扰是一个众所周知的原因，历史上低水平的干扰西南黄松森林，但最近的火灾排除和树木密度的增加，使大规模的树皮甲虫爆发，生态系统功能的未知后果。在一个生长季节内，在亚利桑那州的Sierra Ancha实验林中，对黄松的未受虫害和受虫害的地块（n=10对地块，两个方面）进行了比较，以确定虫害是否与地上生物量和土壤中碳（C）和氮（N）库和通量的差异相关。在我们测量的2年内，至少有80%的上层黄松被小蠹攻击。未受感染和受感染的地块在地上树木生物量中储存了类似于9 kg C m（-2）的生物量，但受感染的地块在死树中储存了60%的地上树木生物量，而未受感染的地块为5%。我们假设，减少地下C分配甲虫引起的树木死亡率会改变土壤呼吸速率，但这一假设不支持，在整个生长季节，在虫害地块的土壤呼吸是类似于未虫害地块。与此相反，一些结果支持的假设，过早的针叶从虫害的树木提供了一个脉冲的低C：N针叶改变土壤氮循环。在整个生长季中，有虫害样地的松针凋落物的C：N质量比（接近45）低于无虫害样地（接近95）。从虫害地块的矿质土壤有更大的实验室净硝化速率和现场树脂袋铵积累比uninfested地块。随着树皮甲虫的爆发在西方景观中变得越来越普遍，关于与其他干扰（例如火灾，收获等）相互作用的长期生物地球化学研究预测生态系统结构和功能的变化。(c)2008 Elsevier B. V.保留所有权利。
Bark beetle infestation is a well-known cause of historical low-level disturbance in southwestern ponderosa pine forests, but recent fire exclusion and increased tree densities have enabled large-scale bark beetle outbreaks with unknown consequences for ecosystem function. Uninfested and beetle-infested plots (n=10 pairs of plots on two aspects) of ponderosa pine were compared over one growing season in the Sierra Ancha Experimental Forest, AZ to determine whether infestation was correlated with differences in carbon (C) and nitrogen (N) pools and fluxes in aboveground biomass and soils. Infested plots had at least 80% of the overstory ponderosa pine trees attacked by bark beetles within 2 years of our measurements. Both uninfested and infested plots stored similar to 9 kg C m(-2) in aboveground tree biomass, but infested plots held 60% of this aboveground tree biomass in dead trees, compared to 5% in uninfested plots. We hypothesized that decreased belowground C allocation following beetle-induced tree mortality would alter soil respiration rates, but this hypothesis was not supported; throughout the growing season, soil respiration in infested plots was similar to uninfested plots. In contrast, several results supported the hypothesis that premature needlefall from infested trees provided a pulse of low C:N needlefall that altered soil N cycling. The C:N mass ratio of pine needlefall in infested plots (similar to 45) was lower than uninfested plots (similar to 95) throughout the growing season. Mineral soils from infested plots had greater laboratory net nitrification rates and field resin bag ammonium accumulation than uninfested plots. As bark beetle outbreaks become increasingly prevalent in western landscapes, longer-term biogeochemical studies on interactions with other disturbances (e.g. fire, harvesting, etc.) will be required to predict changes in ecosystem structure and function. (c) 2008 Elsevier B.V. All rights reserved.