不同种桉树人工林土壤呼吸速率时空动态及其影响要素

Temporal and spatial dynamics of soil respiration and influencing factors in Eucalyptus plantations

为研究不同种桉树Eucalyptus人工林土壤呼吸速率时空变异特征及其影响要素,估算桉树人工林土壤碳排放通量,测定2016年3月-2017年2月时段内5个不同种桉树林及1个湿加松Pinus elliottii×caribaea林土壤呼吸速率,分析桉树人工林土壤呼吸速率时空变化及其与影响要素的相关关系。结果表明:6个林分土壤呼吸速率时间变化明显,均呈单峰曲线格局;土壤呼吸速率与表层土壤温度符合指数模型,与平均体积含水率符合二次多项式模型(P<0.001),土壤呼吸速率时间变化受土壤温度和体积含水率共同驱动,温、湿度双因素模型可以解释土壤呼吸速率44.8%~83.9%的变异。土壤呼吸速率的空间变异主要受表层土壤容重、叶面积指数、总孔隙度和非毛管孔隙度的影响,相关性均为极显著(P<0.01);土壤表面二氧化碳累积通量还受到土壤表层有机碳密度影响,相关性显著(P<0.05)。尾叶桉E.urophylla林和托里桉E.torelliana林的土壤呼吸速率年均值及土壤表面碳排放年累积通量均显著大于其他林分(P<0.05),两者之间差异不显著。

To contribute to a further understanding of soil respiration dynamics and to help to provide an accurate calculation of carbon emissions, the relationship between soil respiration dynamics and influencing factors for six plantation types： Eucalyptus urophylla, E. pellita, E. torelliana, E. camaldulensis, E. urophylla x E. grandis and Pinus elliottii x P. caribaea, along the Leizhou Peninsula was field continuously using the LI 8100A （LI-COR, USA） for spatial and temporal variability in the soil respiration rate from March 2016 to February 2017. With this data, analyses （including correlation analyses） of spatial and temporal variation and analyses of the relative importance of key factors influencing these parameters were undertaken. Results showed that soil respiration rates for the six plantations studied, in relation to soil temperature, all had a single peak in their pattern with both index and quadratic models able to simulate relationships between soil respiration and soil temperature or moisture （0-10 cm）. Temporal variation of the soil respiration rate was driven by both soil temperature and moisture with a two-factor equation （soil temperature and moisture at 10 cm） explaining 44.8% to 83.9% of the variation in soil respiration. Spatial variation of the soil respiration rate was mainly affected by soil bulk density, leaf area index, total soil porosity, and non-capillary soil porosity, with correlations between these parameters and soil respiration rates highly significant （P〈0.01）. Soil surface carbon flux was also correlated to soil organic carbon density （P〈0.05） except for soil bulk density, total soil porosity and non-capillary soil porosity. The annual average of soil respiration and soil surface carbon flux in both E. uro- phylla and E. torelliana plantations were all significantly higher than E. pellita, E. camaldulensis, E. urophylla x E. grandis plantations and P. elliottii x P. caribaea plantation （P〈O.05）, and with no significant differences between E. urophylla and E. torelliana plantations. In total, the spatial and temporal heterogeneity of soil respiration was influenced by various factors, which is the most important consideration in estimating soil respiration flux.