Abstract Understanding the effects of forest structure, the frequency and size of canopy gaps is pivotal for precisely modelling forest soil carbon budgets. We aimed to determine the differences in soil respiration between closed canopy areas and canopy gaps with various sizes and how soil respiration is affected by biotic and abiotic factors, e.g., soil nutrients, soil microbial biomass and community composition, enzyme activities and fine root biomass. Soil respiration and these environmental factors were measured in eleven tree fall gaps (separated into small, medium and large with sizes ranging from 20 m2 to 450 m2) and three control plots in a mixed broadleaved-Korean pine forest during the growing season. Our results showed that soil respiration was similar between the control and small canopy gaps, while it was 17–49% lower in the medium and large canopy gaps compared to that of the control. There was a significant parabolic relationship between soil respiration and soil moisture, and the optimum moisture was approximately 40%. Fine root biomass and soil enzyme activities showed positive effects on soil respiration across different levels of canopy gaps. Furthermore, soil respiration was significantly declined with increasing soil microbial diversity (OTUs of bacteria). Our findings demonstrate that canopy gap has significant impact on soil CO2 emission in a temperate mixed forest, however, further studies concerning other forest ecosystem types and larger scale are warranted.

中文翻译：

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林冠间隙大小对阔叶松林土壤呼吸的影响：来自生物和非生物因素的证据

摘要 了解森林结构的影响、冠层间隙的频率和大小对于精确模拟森林土壤碳收支至关重要。我们旨在确定封闭冠层区域和不同大小冠层间隙之间土壤呼吸的差异，以及土壤呼吸如何受到生物和非生物因素的影响，例如土壤养分、土壤微生物生物量和群落组成、酶活性和细根生物量。土壤呼吸和这些环境因素在生长季节期间在阔叶 - 韩国松林中的 11 个树木倒塌间隙（分为小型、中型和大型，尺寸范围为 20 平方米至 450 平方米）和三个对照地块中进行测量。我们的结果表明，对照和小冠层间隙之间的土壤呼吸相似，与对照相比，中大树冠间隙低 17-49%。土壤呼吸与土壤水分之间存在显着的抛物线关系，最适水分约为40%。细根生物量和土壤酶活性对不同水平冠层间隙的土壤呼吸具有积极影响。此外，随着土壤微生物多样性（细菌的 OTU）的增加，土壤呼吸显着下降。我们的研究结果表明，冠层间隙对温带混交林土壤 CO2 排放有显着影响，但是，有必要对其他森林生态系统类型和更大规模进行进一步研究。最佳水分为40%左右。细根生物量和土壤酶活性对不同水平冠层间隙的土壤呼吸具有积极影响。此外，随着土壤微生物多样性（细菌的 OTU）的增加，土壤呼吸显着下降。我们的研究结果表明，冠层间隙对温带混交林土壤 CO2 排放有显着影响，但是，有必要对其他森林生态系统类型和更大规模进行进一步研究。最佳水分为40%左右。细根生物量和土壤酶活性对不同水平冠层间隙的土壤呼吸具有积极影响。此外，随着土壤微生物多样性（细菌的 OTU）的增加，土壤呼吸显着下降。我们的研究结果表明，冠层间隙对温带混交林土壤 CO2 排放有显着影响，但是，有必要对其他森林生态系统类型和更大规模进行进一步研究。