马尾松林土壤呼吸组分对不同营林措施的响应

Responses of soil respiration and its components to forest management in Pinus massoniana stands

针对不同营林措施(对照、除灌、采伐1(15%)、采伐2(70%)后的三峡库区马尾松飞播林,采用LI-8100对其土壤呼吸组分的呼吸速率和土壤温度、湿度进行为期1年的连续观测分析表明,不同营林措施对土壤呼吸组分的影响不同。1)观测期内,各营林措施下凋落物层呼吸速率差异并不显著,对照、除灌、采伐1、采伐2的根呼吸速率均值分别为:1.00、0.83、0.86、1.11μmolCO_2m^(-2)s^(-1);采伐处理下矿质土壤呼吸显著高于对照和除灌(P<0.05);2)与对照相比,营林措施并未显著改变凋落物呼吸对于土壤总呼吸的贡献率(18.78%-23.70%),但降低了根呼吸的贡献率,其中以采伐1最为显著(P<0.05);除灌的矿质土壤呼吸贡献率(37.00%)与对照(38.32%)相近,而采伐1(45.63%)和采伐2(43.07%)均显著增加了矿质土壤呼吸的贡献率,矿质土壤呼吸的变化是造成采伐措施下土壤呼吸变化的主要土壤呼吸组分;3)营林后仅采伐2措施下土壤温湿度显著高于对照,土壤温湿度双因子模型较单因子模型能更好的解释土壤呼吸组分变化,但仅能解释其部分变化(4.6%-59.3%),仍需对营林后其他相关因子进行深入的综合研究。

Forest soils play a critical role in the carbon cycle and carbon sequestration at both global and local scales, and forest management practices （e.g., harvesting, burning, and thinning） influence soil carbon processes by altering organic matter quality and quantity, key microclimatic conditions, microbial communities, and other factors. However, the effects of forest management on soil carbon effluxes in different ecosystems are still largely unknown, despite being critical to estimate global carbon fluxes. Quantifying the responses of soil respiration and its components to forest management is vital to accurately evaluate forest carbon balance. Thus, an aerially seeded Pinus massoniana forest was chosen in the Three Gorges reservoir area to evaluate the effects on soil respiration of different forest management practices （i.e., control; shrub-cutting：harvesting all shrubs and removing all harvest residues. Harvest strategy 1%-15% harvest intensity and removing main harvest residues without leaves and small branches; Harvest strategy 2%-70% harvest intensity and the same harvest residue management as that in harvest 1）. All experimental treatments were located in similar habitats and consisted of three 20 m×20 m plots. The treatments were conducted in October 2013. A combination of trenching and litter removing methods were employed in order to partition soil respiration into components of litter layer respiration, root respiration, and mineral soil respiration. The soil temperature, soil moisture, and rate of soil respiration and its components were observed continuously for one year （from November 2013 to October 2014） using a Li-8100 system. Management did not affect litter layer respiration within the measuring period. Root respiration in the control, shrub-cutting, harvest strategy 1, and harvest strategy 2 treatments were 1.00, 0.83, 0.86, and 1.11 μmol CO2 m^-2 s^-1, respectively. The mineral soil respiration of harvested stands was significantly higher than that of control and shrub-cutting stands （P 〈 0.05）. The proportion of litter layer respiration to total respiration was not significantly influenced by forest management （18.78%-23.70%）, but the contribution of root respiration to total respiration was reduced, especially in the harvest strategy 1 treatment （P 〈 0.05）. The contribution of mineral respiration to total respiration significantly increased in harvested stands, which was mainly attributed to the decrease in total soil respiration. Management effects on soil temperature and soil moisture were only observed in the stands of harvest strategy 2. A two-factor model that included soil temperature and moisture better explained the variations in soil respiration （4.6%-59.3%） than that by a model using temperature （4.2%-59.1%） or moisture （0.3%-23.5%） alone. Other factors that influence soil respiration and its components need to be further elucidated.