Han Menghua, Feng Huili, Peng Changhui, Lei Xiangdong, Xue Jianhui, Malghani Saadatullah, Ma Xuehong, Song Xinzhang, Wang Weifeng
Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing, Jiangsu 210037, China.
School of Geographic Science, Hunan Normal University, Changsha, Hunan 410000, China.
Tree Physiol. 2022 Dec 12;42(12):2454-2467. doi: 10.1093/treephys/tpac091.
In forest ecosystems, the majority of methane (CH4) research focuses on soils, whereas tree stem CH4 flux and driving factors remain poorly understood. We measured the in situ stem CH4 flux using the static chamber-gas chromatography method at different heights in two poplar (Populus spp.) forests with separate soil textures. We evaluated the relationship between stem CH4 fluxes and environmental factors with linear mixed models and estimated the tree CH4 emission rate at the stand level. Our results showed that poplar stems were a net source of atmospheric CH4. The mean stem CH4 emission rates were 97.51 ± 6.21 μg·m-2·h-1 in Sihong and 67.04 ± 5.64 μg·m-2·h-1 in Dongtai. The stem CH4 emission rate in Sihong with clay loam soils was significantly higher (P < 0.001) than that in Dongtai with sandy loam soils. The stem CH4 emission rate also showed a seasonal variation, minimum in winter and maximum in summer. The stem CH4 emission rate generally decreased with increasing sampling height. Although the differences in CH4 emission rates between stem heights were significant in the annual averages, these differences were driven by differences observed in the summer. Stem CH4 emission rates were significantly and positively correlated with air temperature (P < 0.001), relative humidity (P < 0.001), soil water content (P < 0.001) and soil CH4 flux (P < 0.001). At these sites, the soil emitted CH4 to the atmosphere in summer (mainly from June to September) but absorbed CH4 from the atmosphere during the other season. At the stand level, tree CH4 emissions accounted for 2-35.4% of soil CH4 uptake. Overall, tree stem CH4 efflux could be an important component of the forest CH4 budget. Therefore, it is necessary to conduct more in situ monitoring of stem CH4 flux to accurately estimate the CH4 budget in the future.
在森林生态系统中，大多数甲烷（CH₄）研究集中在土壤方面，而树干CH₄通量及其驱动因素仍知之甚少。我们采用静态箱 - 气相色谱法，在两种具有不同土壤质地的杨树（Populus spp.）林中，于不同高度原位测量了树干CH₄通量。我们用线性混合模型评估了树干CH₄通量与环境因素之间的关系，并估算了林分水平上树木的CH₄排放率。我们的结果表明，杨树树干是大气CH₄的净源。泗洪的平均树干CH₄排放率为97.51 ± 6.21 μg·m⁻²·h⁻¹，东台为67.04 ± 5.64 μg·m⁻²·h⁻¹。泗洪黏壤土的树干CH₄排放率显著高于（P < 0.001）东台的砂壤土。树干CH₄排放率也呈现季节性变化，冬季最低，夏季最高。树干CH₄排放率通常随采样高度增加而降低。尽管不同树干高度的CH₄排放率在年平均值上存在显著差异，但这些差异是由夏季观察到的差异驱动的。树干CH₄排放率与气温（P < 0.001）、相对湿度（P < 0.001）、土壤含水量（P < 0.001）和土壤CH₄通量（P < 0.001）显著正相关。在这些地点，夏季（主要是6月至9月）土壤向大气排放CH₄，而在其他季节则从大气中吸收CH₄。在林分水平上，树木CH₄排放占土壤CH₄吸收量的2% - 35.4%。总体而言，树干CH₄外流可能是森林CH₄收支的重要组成部分。因此，有必要对树干CH₄通量进行更多的原位监测，以便在未来准确估算CH₄收支。
