Sensitivity of soil organic matter to climate and fire in a desert grassland

Enqing Hou, Jennifer A. Rudgers, Scott L. Collins, Marcy E. Litvak, Carleton S. White, Douglas I. Moore, Yiqi Luo

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Drylands contain a third of the organic carbon stored in global soils; however, the long-term dynamics of soil organic carbon in drylands remain poorly understood relative to dynamics of the vegetation carbon pool. We examined long-term patterns in soil organic matter (SOM) against both climate and prescribed fire in a Chihuahuan Desert grassland in central New Mexico, USA. SOM concentration was estimated by loss-on-ignition from soils at 0–20 cm depth each spring and fall for 25 years (1989–2014) in unburned desert grassland and from 2003 to 2014 following a prescribed fire. SOM concentration did not have a long-term trend but fluctuated seasonally at both burned and unburned sites, ranging from a minimum of 0.9% to a maximum of 3.3%. SOM concentration declined nonlinearly in wet seasons and peaked in dry seasons. These long-term results contrast not only with the positive relationships between aboveground net primary production and precipitation for this region, but also with previous reports that wetter sites have more SOM across drylands globally, suggesting that space is not a good substitute for time in predicting dryland SOM dynamics. We suggest that declines in SOM in wet periods are caused by increased soil respiration, runoff, leaching, and/or soil erosion. In addition to tracking natural variability in climate, SOM concentration also decreased 14% following prescribed fire, a response that magnified over time and has persisted for nearly a decade due to the slow recovery of primary production. Our results document the surprisingly dynamic nature of soil organic matter and its high sensitivity to climate and fire in a dry grassland ecosystem characteristic of the southwestern USA.

Original languageEnglish (US)
Pages (from-to)59-74
Number of pages16
JournalBiogeochemistry
Volume156
Issue number1
DOIs
StatePublished - Oct 2021

Keywords

  • Climate sensitivity function
  • Climate variability
  • Desert grassland
  • Soil organic matter
  • Standardized Precipitation Evapotranspiration Index

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology
  • Earth-Surface Processes

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