林分密度对杂种落叶松人工林土壤呼吸的影响

Effects of Stand Density on Soil Respiration in Hybrid Larch Plantations

为了揭示不同林分密度对杂种落叶松人工幼林土壤呼吸的影响规律,在黑龙江省尚志市东北林业大学帽儿山实验林场,选择10年生的杂种落叶松人工林,分3种密度(1283株/hm^2,低密度;2525株/hm^2,中密度;3308株/hm^2,高密度),采用闭合动态法(LI-6400-09)进行土壤呼吸速率(5—10月)测定。结果表明:随林分密度增加,土壤呼吸速率逐渐降低,而且高密度林分的平均土壤呼吸速率(2.05μmol/(m^2·s))明显低于中密度(2.64μmol/(m^2·s))和低密度林分(2.77μmol/(m^2·s))(P<0.05)。土壤温度和含水率均与土壤呼吸速率显著正相关(P<0.05),但在各密度林分间无显著差异(P>0.05)。土壤有机碳和全氮含量与土壤呼吸速率相关不显著(P>0.05)。土壤微生物量碳与土壤呼吸速率呈显著正相关(P<0.05),在生长旺季的5月和7月份土壤微生物量碳随林分密度的变化趋势与土壤呼吸速率相似,均表现高密度林分显著低于中密度和低密度林分(P<0.05)。上述结果说明,土壤微生物量是引起不同密度杂种落叶松林分土壤呼吸速率出现差异的主要原因,营造较高密度的落叶松人工林将更有利于减少因土壤呼吸引起的碳排放。

To reveal the effects of different stand densities on soil respiration in young hybrid larch plantations,three 10-year-old hybrid larch plantations with different densities(1283 plants per hectare,low density;2525 plants per hectare,medium density;3308 plants per hectare,high density)were established to measure soil respiration rate(from May to October)using LI-6400-09 infrared gas exchange analyzer in Northeast Forestry University Mao’er Mountain experiment forest farm,Shangzhi,Heilongjiang Province.Results showed that:soil respiration rate gradually decreased with the increase of stand densities,and the mean soil respiration rate(2.05μmol/(m^2·s))of high density stand was significantly lower than medium density stand(2.64μmol/(m^2·s))and low density stand(2.77μmol/(m^2·s))(P<0.05).Soil temperature and moisture were both significantly positively correlated with soil respiration rate(P<0.05),but there were no significant differences between stands with different densities(P>0.05).Soil organic carbon and total nitrogen content were not significantly correlated with soil respiration rate(P>0.05).Soil microbial biomass carbon was significantly correlated with soil respiration rate(P<0.05),and had similar dynamic trends with soil respiration rate in May and July of peak growing season,with those in high density stand were both significantly lower than medium density and low density stand(P<0.05).The results indicate that soil microbial biomass is the main reason that causes the differences of soil respiration rate among hybrid larch stands with different densities,and building larch plantation with greater density will be beneficial to decrease C emission caused by soil respiration.