Warming and microbial uptake influence the fate of added soil carbon across a Hawai'ian weathering gradient. (February 2021)

• Record Type: Journal Article
• Authors: Neupane, Avishesh; Reed, Sasha C.; Cusack, Daniela F.
• Is Part Of: Soil biology and biochemistry. Volume 153(2021)
• Publication Date: 2021-02
• Subjects: LSAG -- Soil organic carbon -- Microbial biomass -- Carbon use efficiency (CUE) -- Glucose -- Glycine -- 13C; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2020.108080
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: Tropical forest soils contain some of the largest carbon (C) stocks on Earth, yet the effects of warming on the fate of fresh C entering tropical soils are still poorly understood. This research sought to understand how the fate of fresh C entering soils is influenced by warming, soil weathering status, and C chemistry. We hypothesized that compounds that are quickly incorporated into microbial biomass (i.e., greater C use efficiency [CUE]) subsequently have longer-term (255 days) retention in soil. We also hypothesized that relatively weathered soils with greater sorptive capacity also retain more fresh C in the short and longer-terms, and that C in these soils is more resistant to weathering loss compared with less weathered soils. We tested these hypotheses by adding two 13 C-labeled compounds (glucose and glycine) to three tropical forest soils from a weathering gradient in Hawai'i, and then incubating soils at ambient (16 °C), +5 °C, and +10 °C for 255 days. We found that 255-day 13 C retention in mineral soil across sites and temperatures was best predicted by two factors: initial retention of 13 C in mineral soil and initial microbial 13 CUE (Adjusted R 2 = 0.78). Carbon compound type influenced 13 C initial retention, with greater glucose- 13 C retention versus glycine- 13 C retention in mineral soils and microbial biomass, corresponding to greater glucose- 13 C retention in soil at 255 days. Warming had a negative longer-term effect on the retention of 13 C only in the least-weathered soil, supporting our hypothesis. These results show that initial retention of fresh C in soils via mineral sorption and microbial uptake is a strong predictor of longer-term retention, indicating that immediate C losses are a major hurdle for soil C storage. Also, retention of fresh C appears most sensitive to warming in less-weathered tropical soils, supporting the idea that mineral sorption may provide some protections against warming. Understanding the interaction between soil sorptive properties and warming for C cycling could improve predictions of forest-climate feedbacks for tropical regions. Highlights: We studied retention of C from glucose and glycine across a soil mineralogical gradient. Higher initial mineral soil uptake and microbial C use efficiency promoted soil C storage. More C was retained in soil from glucose than from glycine. Warming reduced C retention in least-weathered soil with a lower sorptive capacity. Soil mineralogy may control the temperature sensitivity of extant vs. fresh C differently.