台湾桤木林草复合模式土壤微生物量碳季节动态

摘要

Soil microbes drive carbon and nutrient cycling in forest ecosystem.Soil microbial biomass is commonly limited by environmental factors and soil carbon availability.We employed two forest-grass systems of alder (Alnus formosana) + regrass (Lolium multiflorum) (AL) and alder (Alnus formosana) + limpograss (Hemarthria compress) (AH),as well as alder + natural weed (AN) that served as control,in a returning farmland to forest land in Danling,Sichuan Province,to investigate dynamics of soil organic carbon (SOC) and soil microbial biomass carbon (SMBC) content.The results showed that soil organic carbon and soil microbial biomass carbon content in the two forest-grass compound models and the control (AN) all decreased with depth of the soil layers (0-10,10-20,20-30,30-40 cm),and the decrease speed was fastest in AN,followed by AL and then AH model.The dynamic of SOC content of the three models over the all soil layers exhibited a "down-up-down" trend from spring to winter,except 0-10,10-20 cm in AH model.The SOC content was highest in summer,and lowest in autumn.However,SMBC content exhibited the opposite trend,highest in autumn and lowest in summer.There was significant difference in soil organic carbon and soil microbial biomass carbon between the two forest-grass compound models and AN (P ＜ 0.01),and the rank was in an order of AH model ＞ AL model ＞ AN model.The content of soil organic carbon in AH,and AL was 1.24-1.55,and 1.16-1.30 times of that in AN; and the content of soil microbial biomass carbon in AH,and AL was 1.50-2.95,and 1.23-1.80 times of that in AN.%在四川省丹棱县退耕还林地,设置台湾桤木+多花黑麦草(AL)与台湾桤木+扁穗牛鞭草(AH)2种林草模式,以台湾桤木自然模式(AN)为对照,研究土壤有机碳含量以及土壤微生物量碳含量的季节变化.结果表明:随土层深度增加,2种林草模式与对照土壤有机碳含量和土壤微生物量碳含量均呈现下降趋势,在下降幅度上均表现为台湾桤木+扁穗牛鞭草模式较缓慢,对照模式下降最快;3种模式不同土层土壤有机碳含量从春季到冬季随季节变化均呈现“升-降-升”的变化趋势,夏季含量最高,秋季最低,但这种变化趋势在台湾桤木+扁穗牛鞭草模式下0～10和10～20 cm土层表现得并不明显;而3种模式各土层土壤微生物量碳含量则表现出与土壤有机碳季节动态相反的变化趋势,即“降-升-降”的变化趋势,夏季最低,秋季最高;2种林草模式与对照的土壤有机碳含量和土壤微生物量碳含量差异均达到极显著水平(P＜0.01),其大小顺序均表现为台湾桤木+扁穗牛鞭草模式＞台湾桤木+多花黑麦草模式＞对照模式;台湾桤木+扁穗牛鞭草、台湾桤木+多花黑麦草模式下土壤有机碳含量分别是对照模式的1.24 ～ 1.55和1.16～ 1.30倍,土壤微生物量碳含量分别是对照模式的1.50 ～2.95和1.23 ～1.80倍.