Microbial production of CO_2 in red soil in Stone Forest National Park

Lunan stone forest is a kind of typical karst in China, which is mainly developed under red soil. In the winter of 1999, three study sites were chosen in stone forest national park according to vegetation cover, geomorphologic location and soil types. CO 2 concentration was measured with Gastec pump at different depths of soil (20, 40, 60 cm) and at the same time soil samples were gathered and soil properties such as soil moisture, pH, soil organic content were analyzed and the total number of viable microbes were counted in laboratory. In the study, dependent variable was chosen as the mean soil log (PCO 2 ), and soil properties were chosen as the independent variables. Multiple stepwise regression analysis showed that the total amount of microbes and soil moisture are the best indicators of the CO 2 production, with the equation LOG(PCO 2 ) = - 0.039(TNM) - 0.056(Mo) + 1.215 accounting for 86% of the variation of the soil CO 2 concentration, where TNM is the total number of microbes in the soil and Mo is the moisture of soil sample.

干旱半干旱区果园生草条件下土壤微生物(细菌)的多样性

采选4种具备潜在“绿肥”功能的草种(黑麦草、苜蓿、高羊茅、长柔毛野豌豆)以及自然生草和清耕模式进行果园行间长期生草处理,应用高通量测序技术分析不同生草模式下果园土壤细菌群落结构、数量和功能的变化,以期为干旱半干旱区果园的合理生草和苹果生产可持续发展提供参考依据。结果表明:生草处理下细菌OTUs被划分为39个已知细菌门、94纲、266目、541科、127属。其中苜蓿(458个OTUs)及自然生草(531个OTUs)处理具有更多的群体特异性OTUs,其次为黑麦草与长柔毛野豌豆处理,并且相较于清耕,生草处理的土壤显著富集了拟杆菌纲、梭状芽孢杆菌纲、放线菌纲、变形菌纲、拟杆菌门、草酸杆菌科、假单胞菌科、芽孢杆菌科等有益微生物。PCoA主成分、Adonis组间差异分析和α多样性(ACE指数)进一步表明,土壤细菌群落的组成主要受生草处理影响,其中自然生草、苜蓿及长柔毛野豌豆处理区域土壤样品中的细菌群落差异以及细菌多样性更显著。同时自然生草、苜蓿及长柔毛野豌豆生草处理下差异代谢通路主要聚焦于碳水化合物代谢,氨基酸代谢,能量代谢,跨膜转运及核苷酸代谢,其平均丰度分别为13.6%、9.5%、4.2%、3.4%、3.2%。综上所述,生草处理可影响细菌群落结构,其中自然生草、苜蓿及长柔毛野豌豆生草进一步显著促进了细菌群落的功能。