Insight into climate change from the carbon exchange of biocrusts utilizing non-rainfall water

Hailong Ouyang,Chunxiang Hu

doi:10.1038/s41598-017-02812-y

Abstract

Biocrusts are model ecosystems of global change studies. However, light and non-rainfall water (NRW) were previously few considered. Different biocrust types further aggravated the inconsistence. So carbon-exchange of biocrusts (cyanobacteria crusts-AC1/AC2; cyanolichen crust-LC1; chlorolichen crust-LC2; moss crust-MC) utilizing NRW at various temperatures and light-intensities were determined under simulated and insitu mesocosm experiments. Carbon input of all biocrusts were negatively correlated with experimental temperature under all light-intensity with saturated water and stronger light with equivalent NRW, but positively correlated with temperature under weak light with equivalent NRW. LCPs and R/Pg of AC1 were lowest, followed in turn by AC2, LC2 and MC. Thus AC1 had most opportunities to use NRW, and 2.5 °C warming did cause significant changes of carbon exchange. Structural equation models further revealed that air-temperature was most important for carbon-exchange of ACs, but equally important as NRW for LC2 and MC; positive influence of warming on carbon-input in ACs was much stronger than the latter. Therefore, temperature effect on biocrust carbon-input depends on both moisture and light. Meanwhile, the role of NRW, transitional states between ACs, and obvious carbon-fixation differences between lichen crusts should be fully considered in the future study of biocrusts responding to climate change.

Highlights

Arid and semiarid regions account for 41% of global land area, while more than 70% soil surface of these regions is occupied by biocrusts mainly composed by cyanobacteria, fungi, lichen and moss
photosynthesis rate (Pn) obviously increased with light intensity, but decreased with rising temperature for the same biocrusts, though no significant difference over different temperatures
The pattern of Pg was similar to Pn, namely increased with light intensity and temperature, but the increasing amount was highest in ACs, followed by LCs, and moss crust (MC) was the lowest

Summary

Introduction

Arid and semiarid regions account for 41% of global land area, while more than 70% soil surface of these regions is occupied by biocrusts mainly composed by cyanobacteria, fungi, lichen and moss. As to the effects of altered precipitation, the composition and function of biocrusts were not significantly influenced, or only negatively affected in certain areas or seasons[5, 7, 9, 13, 17, 21], or completely contradictory in the same geographic profile[25, 26]. Since photosynthesis of most plants mainly occurs in daytime with abundant sunlight, previous studies paid more attention to the effects of temperature and water rather than light[5, 18, 47], the influence of light on carbon exchange of biocrusts is poorly known

Methods

Results

Conclusion