Soil water regulates the control of photosynthesis on diel hysteresis between soil respiration and temperature in a desert shrubland

Ben Wang,Yun Tian,Bin Wu,Xin Jia,Tian Shan Zha,Wei Feng,Charles Bourque,Jin Nan Gong,Heli Peltola,Yu Qing Zhang

doi:10.5194/bg-14-3899-2017

Abstract

Abstract. Explanations for the occurrence of hysteresis (asynchronicity) between diel soil respiration (Rs) and soil temperature (Ts) have evoked both biological and physical mechanisms. The specifics of these explanations, however, tend to vary with the particular ecosystem or biome being investigated. So far, the relative degree of control of biological and physical processes on hysteresis is not clear for drylands. This study examined the seasonal variation in diel hysteresis and its biological control in a desert-shrub ecosystem in northwest (NW) China. The study was based on continuous measurements of Rs, air temperature (Ta), temperature at the soil surface and below (Tsurf and Ts), volumetric soil water content (SWC), and photosynthesis in a dominant desert shrub (i.e., Artemisia ordosica) over an entire year in 2013. Trends in diel Rs were observed to vary with SWC over the growing season (April to October). Diel variations in Rs were more closely associated with variations in Tsurf than with photosynthesis as SWC increased, leading to Rs being in phase with Tsurf, particularly when SWC > 0.08 m3 m−3 (ratio of SWC to soil porosity = 0.26). However, as SWC decreased below 0.08 m3 m−3, diel variations in Rs were more closely related to variations in photosynthesis, leading to pronounced hysteresis between Rs and Tsurf. Incorporating photosynthesis into a Q10-function eliminated 84.2 % of the observed hysteresis, increasing the overall descriptive capability of the function. Our findings highlight a high degree of control by photosynthesis and SWC in regulating seasonal variation in diel hysteresis between Rs and temperature.

Highlights

IntroductionDiel hysteresis (asynchronicity) between soil respiration (Rs) and soil temperature (Ts) is widely documented for forests (Tang et al, 2005; Gaumont-Guay et al, 2006; RiverosIregui et al, 2007; Stoy et al, 2007; Vargas and Allen, 2008; Jia et al, 2013), grasslands (Carbone et al, 2008; BarronGafford et al, 2011), and desert ecosystems (Wang et al, 2014; Feng et al, 2014)
The study was based on continuous measurements of Rs, air temperature (Ta), temperature at the soil surface and below (Tsurf and Ts), volumetric soil water content (SWC), and photosynthesis in a dominant desert shrub (i.e., Artemisia ordosica) over an entire year in 2013
We suggest that photosynthesis should be considered in simulations of diel Rs in drylands, especially when SWC falls below 0.08 m3 m−3

Summary

Introduction

Diel hysteresis (asynchronicity) between soil respiration (Rs) and soil temperature (Ts) is widely documented for forests (Tang et al, 2005; Gaumont-Guay et al, 2006; RiverosIregui et al, 2007; Stoy et al, 2007; Vargas and Allen, 2008; Jia et al, 2013), grasslands (Carbone et al, 2008; BarronGafford et al, 2011), and desert ecosystems (Wang et al, 2014; Feng et al, 2014). Two main processes have been reported to relate to diel hysteresis between Rs and Ts. One is associated with the physical processes of heat and gas transport in soils (Vargas and Allen, 2008; Phillips et al, 2011; Zhang et al, 2015). Transport of CO2 gas to the soil surface takes time to oc-

Objectives

Methods

Results

Discussion

Conclusion