Herbaceous layer determines the relationship between soil respiration and photosynthesis in a shrub-dominated desert plant community

Aims Although the linkages between aboveground photosynthates production and belowground respiration processes have been well studied, doubts remain as to the extent that photosynthate regulates soil respiration (R soil ) and its generality throughout the growing season in a given ecosystem. This study aimed to test whether photosynthesis affected R soil at the diurnal scale and assess how the relation between them changed with changing vegetation composition. Methods We measured R soil and gross primary productivity (GPP using eddy covariance) in two consecutive growing seasons (2013–2014) in a desert ecosystem, western China. We compared R soil on sunny days with that on adjacent cloudy days in two periods with different vegetation compositions [herbs-shrub coexistence period (HSP) and purely shrubs dominated period (SDP)] to identify how photosynthesis affect R soil . Results GPP regulated diurnal variations of R soil conspicuously in spite of the strong correlation between soil temperature (T soil ) and R soil , but such regulation was limited in HSP. 48.3% of the changes in daytime R soil between sunny and cloudy days was explained by changes in T soil together with changes of GPP in HSP. When spring annuals died, no differences in daily amplitude and average of R soil between sunny and cloudy days were found. Conclusions Our results suggested that effect of photosynthesis on R soil was not constant throughout the growing season. In the presence of herbaceous plants, R soil was directly related to photosynthesis. These findings highlighted the important role of photosynthesis played in R soil regulation and the importance of community composition in determining the extent that photosynthesis affects R soil .