杉木生长及土壤特性对土壤呼吸速率的影响

Effects of tree growth and soil properties on soil respiration rate in Chinese fir plantations

在江西大岗山生态站选择不同发育阶段杉木人工林,研究土壤呼吸速率、土壤性质和年凋落物量的变化特征以及它们之间的相互关系。结果表明:杉木人工林随林分发育过程中林龄增加,林分年凋落物量和土壤纤维素酶活性逐渐增加;蔗糖酶活性呈现出先增加后降低的变化趋势,而淀粉酶活性无明显变化规律。土壤理化性质表现为幼龄林阶段较好,中龄林最差、近熟林—过熟林又逐渐恢复的变化特征;但不同指标恢复速度不同。土壤呼吸速率从幼龄林到近熟林呈明显先降低后增加的变化规律;从近熟林到成熟林略有增加,但增加不显著;过熟林时又显著降低,达到中龄林水平。通径分析表明,不同土壤性质对土壤呼吸速率表现出不同程度的影响;在被研究的土壤性质中,年凋落物量、土壤有机碳含量和纤维素酶活性对土壤呼吸速率表现出更强烈的直接影响和间接影响作用。

As an important component of carbon cycle in forest ecosystem,soil respiration characteristics and its affecting factors in Chinese fir plantations have gradually become the focus.Tree growth and soil properties definitely affect soil respiration rate in the entire developmental stages of Chinese fir plantations from juvenile,medium,near mature,mature,to over mature.In this paper,the Chinese fir plantations at different developmental stages in Dagang Mountain of Jiangxi Province were selected to investigate the effects of tree growth on soil respiration rate,and the relationship between soil respiration rate and soil properties was further studied with path analysis.The results showed that soil respiration rate ranged from 0.51 μmol · m-2s-1 to 1.14 μmol · m-2s-1,and it decreased first and then increased from juvenile to near-mature,slightly increased from near-mature to mature,and significantly decreased in the over-mature forest soil.With increasing stand age,annual litterfall amount and soil cellulase activity increased gradually,invertase activity decreased first and then increased,and amylase activity had no significant change.Soil physico-chemical properties were found better in the juvenile forest,worst in the medium forest,and they recovered gradually from near-mature to over-mature with different recovery speed.The direct path coefficients of soil properties to soil respiration rate were in the descending order of annual litterfall amount,soil organic carbon content,soil cellulase activity,field capacity,non-capillary porosity,bulk density,total nitrogen content,invertase activity,capillary porosity,capillary water-holding capacity,amylase activity,and total porosity.The direct path coefficients of annual litterfall amount,soil organic carbon content and soil cellulase activity to soil respiration rate were 1.069,0.736,0.518,respectively,indicating the most intense direct effects.Their high indirect path coefficients further indicated the profound influence of their interaction on soil respiration rate.With intense direct and indirect effects,annual litterfall amount,soil organic carbon content and soil cellulase activity were the dominant factors for the variation of soil respiration rate.