Lhasa Plateau Ecosystem Research Station, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
College of Forestry and Conservation, University of Montana, Missoula, Montana, USA.
Glob Chang Biol. 2022 Oct;28(20):6102-6113. doi: 10.1111/gcb.16337. Epub 2022 Jul 21.
Elucidating the response mechanism of soil respiration (Rs) to silvicultural practices is pivotal to evaluating the effects of management practices on soil carbon cycling in planted forest ecosystems. However, as common management practices, how thinning, understory plant removal, and their interactions affect Rs and its autotrophic and heterotrophic components (Ra and Rh) remains unclear. Therefore, we investigated Rs, Ra and Rh by the trenching method from 2011 to 2015 in a Pinus tabuliformis plantation in northern China, subjecting to four treatments (intact control plots [CK], thinning [T], understory removal [UR], and thinning with understory removal [TUR]). Mean annual Rs was significantly increased by thinning (by 15.3%), whereas decreased by UR (by 17.4%), compared with CK. These variations in Rs were mainly attributed to changes in Ra. The increments of Ra were caused by the enhanced growth of fine root biomass after thinning. However, UR led to lower Ra compared with CK (p < .05), indicating that understory growth is inadequate to compensate for the decreased respiring root biomass induced by understory removal. Rs was unchanged between TUR and the intact control plot due to the opposite effects of thinning and UR on the Ra. Changes in Rh exhibited no significant differences among the treatments, partly because of the stable microbial biomass carbon (MBC) and forest floor mass (litter and fine woody debris). No interaction effect between thinning and understory removal was detected on Rs, Ra, and Rh. The lowest temperature sensitivity (Q ) value of Ra was found in CK. This study highlights the necessity of incorporating understory plant effects on soil CO efflux in assessing forest management practices on soil carbon cycling.
阐明林地土壤呼吸（Rs）对营林措施的响应机制，对于评估管理措施对人工林生态系统土壤碳循环的影响至关重要。然而，作为常见的管理措施，间伐、去除林下植被及其相互作用如何影响 Rs 及其自养和异养组分（Ra 和 Rh）尚不清楚。因此，我们采用坑槽法，于 2011 年至 2015 年在中国北方的油松人工林内，设置了完整对照（CK）、间伐（T）、去除林下植被（UR）和间伐+去除林下植被（TUR）4 种处理，研究了 Rs、Ra 和 Rh。与 CK 相比，间伐（增加 15.3%）显著增加了 Rs，而 UR（减少 17.4%）降低了 Rs。这种 Rs 的变化主要归因于 Ra 的变化。Ra 的增加是由于间伐后细根生物量的增强生长所致。然而，UR 导致 Ra 低于 CK（p <.05），表明林下植被的生长不足以弥补因去除林下植被而导致的呼吸根生物量减少。由于间伐和 UR 对 Ra 的相反作用，TUR 与完整对照之间 Rs 没有变化。处理之间 Rh 的变化没有显著差异，部分原因是微生物生物量碳（MBC）和枯落物和细木质残体的林地板质量稳定。间伐和去除林下植被之间没有检测到 Rs、Ra 和 Rh 的交互作用。Ra 的最低温度敏感性（Q ）值出现在 CK 中。本研究强调，在评估森林管理措施对土壤碳循环的影响时，需要考虑林下植被对土壤 CO 排放的影响。
