Old growth forest soils are large C reservoirs, but the impacts of tree-fall gaps on soil C in these forests are not well understood. The effects of forest gaps on soil C dynamics in old growth northern hardwood-hemlock forests in the upper Great Lakes region, USA, were assessed from measurements of litter and soil C stocks, surface C efflux, and soil microbial indices over two consecutive growing seasons. Forest floor C was significantly less in gaps (19.0 Mg C hap#) compared to gap-edges (39.5 Mg C hap#) and the closed forest (38.0 Mg C hap#). Labile soil C (coarse particulate organic matter, cPOM) was significantly less in gaps and edges (11.1 and 11.2 Mg C hap#) compared to forest plots (15.3 Mg C hap#). In situ surface C efflux was significantly greater in gaps (12.0 Mg C hap# yp#) compared to edges and the closed forest (9.2 and 8.9 Mg C hap# yp#). Microbial biomass N (MBN) was significantly greater in edges (0.14 Mg N hap#) than in the contiguous forest (0.09 Mg N hap#). The metabolic quotient (qCO) was significantly greater in the forest (0.0031 mg CO hp# gp#/mg MBC gp#) relative to gaps or edges (0.0014 mg CO hp# gp#/mg MBC gp#). A case is made for gaps as alleviators of old growth forest soil C saturation. Relative to the undisturbed closed forest, gaps have significantly less labile C, significantly greater in situ surface C efflux, and significantly lower decreased qCO values.
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机译：旧的生长森林土壤是大型的C储层，但对于这些森林中的树倒隙对土壤C的影响尚不十分了解。通过测量连续两个生长季凋落物和土壤碳储量，表面碳外排量和土壤微生物指标，评估了美国美国大湖区北部北部老龄阔叶铁杉铁杉林中森林缺口对土壤碳动态的影响。 。与间隙边缘（39.5 Mg Chap＃）和密林（38.0 Mg Chap＃）相比，林地C的缝隙（19.0 Mg Chap＃）明显更少。与林区（15.3 Mg Chap＃）相比，不稳定土壤C（粗粒有机物，cPOM）的间隙和边缘（11.1和11.2 Mg Chap＃）明显更少。与边缘和封闭林区（9.2和8.9 Mg Chap＃yp＃）相比，间隙中的原位表面C外排明显更大（12.0 Mg Chap＃yp＃）。边缘（0.14 Mg N hap＃）的微生物生物量氮（MBN）显着大于连续森林（0.09 Mg N hap＃）。相对于间隙或边缘（0.0014 mg CO hp＃gp＃/ mg MBC gp＃），森林中的代谢商（qCO）明显更高（0.0031 mg CO hp＃gp＃/ mg MBC gp＃）。提出了作为缓解老生长森林土壤C饱和度的缺口的理由。相对于未受干扰的封闭森林，缝隙的不稳定C值显着降低，原位地表C流量显着提高，qCO降低值显着降低。
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