ABSTRACT

Soil organic matter composition controls many microbial processes in the soil matrix. How these processes interact to drive carbon cycling through greenhouse gas fluxes or carbon stabilization through biochemical transformations continues to evolve. From laboratory incubations, it is clear that low molecular weight compounds (LMWCs; e.g. dextrose, mannitol, and trehalose) can have a profound effect on microbially mediated fluxes. However, relationships between LMWCs and soil efflux have been largely unproven in field studies due to methodological constraints. In the current study we developed a novel use of Near Infrared Reflectance Spectroscopy (NIRS) to quantify LMWCs (explaining 38–51% of the variance). Paradoxically, we found dextrose concentrations to be negatively correlated with carbon dioxide fluxes in residential sites while mannitol was positively correlated with carbon dioxide fluxes in agricultural sites. Methane fluxes were strongly correlated with trehalose indicating a potential fungal interaction with bacterial methanogens. We found no clear link between LMWCs on nitrous oxide emissions suggesting inorganic nitrogen is a stronger limiting factor. The results from this study showed how a NIRS-based approach can improve mechanistic understanding of the drivers of soil greenhouse gas fluxes.

摘要

土壤有机质成分控制着土壤基质中的许多微生物过程。这些过程如何相互作用以驱动通过温室气体通量的碳循环或通过生化转化的碳稳定化不断发展。从实验室培养中可以清楚地看出，低分子量化合物（LMWC；例如右旋糖，甘露醇和海藻糖）对微生物介导的通量具有深远的影响。然而，由于方法学上的限制，LMWC与土壤外排之间的关系在实地研究中尚未得到充分证实。在当前的研究中，我们开发了一种新颖的近红外反射光谱（NIRS）用途来量化LMWC（解释了38％至51％的方差）。矛盾的是，我们发现右旋糖浓度与居民区的二氧化碳通量呈负相关，而甘露醇与农业区的二氧化碳通量呈正相关。甲烷通量与海藻糖密切相关，表明与细菌产甲烷菌的潜在真菌相互作用。我们发现LMWC之间与一氧化二氮排放之间没有明确的联系，表明无机氮是一个更强的限制因素。这项研究的结果表明，基于近红外光谱的方法如何改善对土壤温室气体通量驱动因素的机械理解。我们发现LMWC之间与一氧化二氮排放之间没有明确的联系，表明无机氮是一个更强的限制因素。这项研究的结果表明，基于近红外光谱的方法如何改善对土壤温室气体通量驱动因素的机械理解。我们发现LMWC之间与一氧化二氮排放之间没有明确的联系，表明无机氮是一个更强的限制因素。这项研究的结果表明，基于近红外光谱的方法如何改善对土壤温室气体通量驱动因素的机械理解。