Browsing by Author "Fuhrmann, Jeffry J."
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Item Moso bamboo expansion into a broadleaved forest alters the dominant soil organic carbon source(European Journal of Soil Science, 2023-05-09) Shao, Shuai; He, Hongbo; Liang, Chenfei; Chen, Junhui; Qin, Hua; Wang, Shanshan; Wang, Zhongqian; Li, Yi; Jia, Weina; Zheng, Xuli; Chen, Yong; Fuhrmann, Jeffry J.; Xu, Qiufang; Zhang, XudongBoth microbes and plants contribute to soil organic carbon (SOC) formation and retention, but their roles in controlling SOC dynamics in forest soils under Moso bamboo (Phyllostachys edulis) expansion remain unclear. Here, amino sugars and lignin monomers were measured to represent microbial necromass and plant-derived components, respectively. The observed decline in both amino sugars and lignin monomers during Moso bamboo expansion indicates a reduction in microbial necromass and recalcitrant plant contributions to SOC composition. This could be attributed to a limitation of microbial substrates and proliferation caused by the reduced litter inputs resulting from the expansion. The proportion of microbial necromass contributing to the SOC pool increased, but that of lignin monomers decreased, as SOC content decreased with Moso bamboo expansion. This suggests that the decrease of SOC during bamboo expansion was mainly due to the reduction of lignin, while the increased contribution of microbial-derived carbon to SOC may serve to improve SOC stability. Our study sheds light on the altered SOC source inputs resulting from Moso bamboo expansion and emphasizes the need for sustainable forestry management practices that differentiate between microbial- and plant-derived carbon pools. HIGHLIGHTS 1. Both soil amino sugars and lignin monomers decreased with Moso bamboo expansion. 2. The dominant source of SOC changed during the Moso bamboo expansion. 3. SOC reduction was mainly due to the decline of lignin during Moso bamboo expansion. 4. Microbial necromass plays a key role in SOC retention during Moso bamboo expansion.Item The unexplored role of preferential flow in soil carbon dynamics(Soil Biology and Biochemistry, 2021-08-28) Franklin, Shane M.; Kravchenko, Alexandra N.; Vargas, Rodrigo; Vasilas, Bruce; Fuhrmann, Jeffry J.; Jin, YanWater is a crucial factor controlling the fate and processing of soil organics. Water commonly flows through the vadose zone via preferential flow pathways, resulting in nonuniform and rapid infiltration. Hence, a large portion of the soil matrix is bypassed. Preferential flow paths, often associated with well-connected macropore networks (>300 μm Ø), offer a unique balance between water availability, nutrient delivery, and re-oxygenation upon drainage. The heightened concentrations of moisture, nutrients, and oxygen make these locations optimal for high rates of microbial activity. Flow paths often display temporal stability. This stability results in repeated wetting and biogeochemical reactivation through time creating a lasting impact on micro-environmental conditions relevant to microbial functioning and carbon cycling in soil. Despite decades of research on preferential flow, there is still a need to link flow paths and the resultant heterogeneous moisture distributions to soil function. In this review, we discuss how preferential flow can serve as a framework of reference for the spatially and temporally heterogeneous biogeochemical cycling of soil carbon. We highlight the importance of combining current knowledge of pore-scale carbon dynamics with an appreciation of connected networks of hydraulically active pores/paths within the soil profile. Such combination opens new possibilities for upscaling pore-scale processes with the inclusion of resource heterogeneity at the macroscale. Working within this hydraulically connected framework can provide insight for the mechanistic representation of hot moments, which are temporally isolated large pulses of CO2 after rewetting or thawing events. We conclude with suggestions on knowledge gaps and stress the critical need of linking soil physics with biology to mechanistically understand soil functions. Highlights • Preferential flow paths play a key role in soil carbon dynamics. • Pore-scale carbon dynamics could be upscaled using hydraulic connectivity. • A conceptual model is presented that considers how soil pores function from hydrological and microbial perspectives.