秦岭火地塘林区油松(Pinus tabulaeformis)林休眠期的土壤呼吸

Soil respiration in Pinus tabulaeformis forest during dormant period at Huoditang forest zone in the Qinling Mountains

林木休眠期林地土壤CO2释放是森林生态系统碳平衡关键组成部分之一。由于绝大多数森林生态系统林木休眠期土壤CO2释放过程测定困难,国内有关林木休眠期CO2释放,量化方面的研究开展较少。采用动态开路气室法对秦岭火地塘林区天然次生油松(Pinus tabulaeformis)林土壤呼吸的日变化进行了测定,分析了土壤呼吸速率(mgCO2m-2h-1)与土壤温度和体积含水率的关系,基于土壤日均呼吸速率和土壤日均温度指数方程与观测季的总天数,估算了林木休眠期林地土壤CO2释放量。结果表明:(1)研究区林地土壤呼吸速率存在较大的时、空变异。不同观测部位土壤呼吸速率的峰值出现时间各异,呼吸作用较弱的时段也不一致。同一观测部位不同观测月中,土壤日均呼吸速率变异系数分别为48.38%,82.51%和81.88%;(2)当土温>8.5℃时,0~5 cm和5~10 cm土层,土壤日均温与土壤日均呼吸速率间存在极显著(p<0.001)的指数关系,Q10分别为1.297和1.323;(3)0~5 cm和5~10 cm土层,土壤体积含水率与土壤呼吸速率间关系复杂;(4)林木休眠期研究区林地土壤CO2释放量变化于(977.37±88.43)^(997.19±80.73)gCm-2(p=0.005)间。

Soil CO2 efflux in forest ecosystems during dormant season is one of the key components of the forest ecosystem carbon balance. Little work has been done to quantify soil CO2 effiuxes in most forests in the special time in China because of the difficulty in taking measurements. Soil respiration in a natural secondary Pinus tabulaeformis forest at Huoditang in the Qinling Mountains was measured from October to December in 2006 by means of open-path dynamic chamber technique. Relationships between soil respiration rate （R） and soil mean temperature （SMT）, Rs and soil mean volumetric moisture content （SMVC） in different depth （0- 5 cm, 5 --10 cm） were examined in the current study. We found that （1） there were tremendous temporal and spatial variations in Rs with coefficients of variation of Rx at same observation site （ upper- part, middle and under-part） of 48.38%, 82.51% and 81.88% in October, November and December respectively; （2） Fc （ soil diurnal mean respiration rate） and SDMT （ soil diurnal mean temperature） were significantly correlated with an exponent relationship when SDMT 〉8.5 % for both soil depths （0--5 cm and 5 --10 cm ） examined. The temperature sensitivity of soil respiration, known as the Q10 value, was 1. 297 and 1. 323 respectively in depth of 0--5 cm and 5 --10 cm in soil; （3） relationship between R~ and SMVC was complex in depth of 0 --5 cm and 5 --10 cm in soil; （4） soil CO2 effluxes from October to December in 2006 in the experimental area was （977.37±88.43 ） --（997.19 ±80.73 ） gCm^-2 （p =0. 005）.