植物种和氮添加对元谋干热河谷草地土壤有机碳分解的影响

Effects of plant species and nitrogen addition on soil organic carbon decomposition in the Yuanmou dry-hot valley grassland, China

为了解植物生长和氮(N)添加对元谋干热河谷区草地土壤活性炭组分和惰性碳组分分解的影响,在元谋干热河谷典型燥红土上开展植物物种和氮添加实验,分析不同物种[扭黄茅(Heteropogon contortus)、橘草(Cymbopogon goeringii)、孔颖草(Bothriochloa pertusa)、拟金茅(Eulaliopsis binata)]和氮(N)添加对干热河谷区草地土壤有机碳分解的影响.结果表明:(1)相较于裸地,植物着生后土壤全碳(TC)、全氮(TN)含量以及土壤C:N增加;土壤微生物含量增加,土壤活性炭组分和惰性碳组分分解速率显著升高.(2)N添加后土壤中微生物呼吸速率、微生物代谢熵以及惰性碳组分分解速率均不同程度降低.(3)双因素方差分析表明,N添加和不同植物种对碳分解均有显著影响,但两者交互作用对碳分解速率的影响不显著.总之,在元谋干热河谷植物生长能够显著改善土壤理化性质,促进土壤有机碳的分解,而氮添加对土壤惰性碳组分的分解有抑制作用;上述研究结果可为认识植被恢复和氮沉降背景下干热河谷土壤碳循环提供一定理论基础,同时为干热河谷土壤生态系统功能恢复和调控提供科学依据.

To investigate the effects of plant growth and nitrogen(N) addition on the decomposition of active carbon and inactive carbon components in the Yuanmou dry-hot valley grassland, a field manipulation experiment was conducted from 2013 to 2015 on rhodoxeral soils in an arid-hot valley of the Jinsha River, with a factorial treatment of plants and nitrogen addition. The plant treatments included bare plots and four grass species(Heteropogon contortus,Bothriochloa pertusa, Cymbopogon goeringii, and Eulaliopsis binata), with 10 replications. Half of each plot received N addition(5 g m;a;), and the other half was a control. The effects of treatment on aboveground biomass and soil chemical properties were analyzed using a univariate ANOVA. A two-way ANOVA analysis determined the effects of nitrogen addition, plant species, and their interactions on carbon decomposition parameters. Their relationships were investigated using a general linear regression model correlation analysis. The results showed that:(1) the total carbon(TC), total nitrogen(TN), soil C:N, and soil microbial contents were significantly higher in the vegetation plots than in the bare plots. Similarly, the decomposition rates of active carbon components and inactive carbon components were significantly higher in the vegetation plots than in the bare plots;(2) the respiration rate, metabolic quotient, and decomposition rate of inactive carbon components of soil microorganisms decreased after N addition;and(3) the twoway ANOVA results showed that both N addition and plant species had significant effects on carbon decomposition,with no significant interactions. In conclusion, the growth of plants can significantly improve the physical and chemical properties of soil and promote the decomposition of soil organic carbon, while nitrogen addition has an inhibitory effect on the decomposition of soil inert carbon. The findings presented here can improve our understanding of changes in the soil carbon cycle under vegetation restoration and nitrogen deposition and provide a scientific basis for restoring and regulating soil ecosystem function in dry-hot valleys.