去除和添加凋落物对枫香（Liquidambar formosana）和樟树（Cinnamomum camphora）林土壤呼吸的影响

2007年1月至12月,在长沙天际岭国家森林公园,使用LI-COR-6400-09连接到LI-6400便携式CO2/H2O分析系统,测定亚热带枫香(Liquidambar formosana)和樟树(Cinnamomum camphora)林去除和添加凋落物(931.5 g · m-2a-1和1003.4 g · m-2a-1)的土壤呼吸速率以及5 cm土壤温、湿度,研究凋落物对2种森林生态系统中土壤呼吸速率的影响.结果表明:枫香和樟树林去除和添加凋落物的土壤呼吸速率季节变化显著,在季节动态上的趋势与5 cm土壤温度相似,均呈单峰曲线格局,全年去除凋落物土壤呼吸速率平均值分别为1.132 μmol CO2 · m-2s-1和1.933 μmol CO2 · m-2s-1,分别比对照处理1.397 μmol CO2 · m-2s-1和2.581 μmol CO2 · m-2s-1低18.62%和26.49%;添加凋落物土壤呼吸速率平均值分别为2.363 μmol CO2 · m-2s-1和3.267 μmol CO2 · m-2s-1,分别比对照处理高71.31%和39.18%.两种群落去除和添加凋落物土壤呼吸的季节变化均与5 cm土壤温度呈显著指数相关(P﹤0.001),与5 cm土壤湿度相关性不显著(P>0.05);土壤温度和湿度可以共同解释去除和添加凋落物后土壤呼吸变化的95.2%、93.7%和90.0%、92.8%.枫香和樟树群落去除和添加凋落物土壤呼吸温度敏感性Q10值分别为3.01、3.29和3.02、4.37,均比对照处理Q10值2.98和2.94高.这证明凋落物是影响森林CO2通量的一个重要因子.

Impact of litter addition and exclusion on soil respiration in a Liquidambar formosana forest and a nearby Cinnamomum camphora forest of central southern China

We evaluated the impact of litter-fall on soil respiration under a Liquidambar formosana forest and a nearby Cinnamomum camphora forest in Tianjiling National Forestry Park of Changsha, Hunan, using a field study with litter removal and exclusion and litter addition in a full factorial design. Soil respiration was measured using an infrared gas exchange analyzer (LI_COR -6400-09) from January to December 2007. Soil temperature and moisture at 5 cm depth in the experimental plots were also recorded at the same time. On average, soil respiration was significantly decreased by litter exclusion, about 18.6% and 26.5% lower relative to controls in Liquidambar formosana and Cinnamomum camphora forests, respectively. On the other hand, litter addition significantly increased soil respiration by 71.3% and 39.2% in these two forests compared with the controls. Significant relationships were found between soil respiration and soil temperatures at 5 cm soil depth in litter addition and exclusion plots, which could be best described by exponential equations. However, not significant relationships were found between soil respiration and soil moistures at 5 cm depth in all study plots. Soil temperature and moisture together could explain changes in soil respiration of 75.2% and 93.7%, and 90.0% and 92.8% in litter exclusion and addition plots in the Liquidambar formosana and Cinnamomum camphora forests, respectively. The Q10 values were increased in litter exclusion and litter addition plots (3.01, 3.29 and 3.02, 4.37) relative to controls (2.98 and 2.94) in the Liquidambar formosana and Cinnamomum camphora forests, respectively. The results indicated that above-ground litter-fall is an important factor in affecting soil CO2 efflux in forests.