What Are the Seasonal Dynamics of Ecosystem Carbon Exchange at different Phenological Stages of Plant Community?

Arid and semi-arid regions, covering about 30% of the global land surface, significantly contribute to global carbon cycle. Compared to other ecosystems, desert is more heavily influenced by climate change, thus it is one of the most active compo?nents of carbon budget in arid and semi-arid regions. In desert ecosystems, there are large variations in ecosystem carbon (C) exchange, and changes in vegetation composition and dominant plant functional group could affect ecosystem C exchange. However, few studies have examined the effects of community phenological staging on seasonal variations of ecosystem C exchange.

Gurbantunggut Desert has a typical continental arid climate with different plant species dominated the plant community in different seasons. In this desert, the accumulated snow rapidly melts in early spring and the melting water is absorbed into the soil, which highly favors the germination and growth of ephemerals. As a result, ephemerals dominate the plant community in spring. In summer, the annuals and perennials, especially drought-tolerant species, rely on some specific adaptations (i.e. leaf hairs, succulence and a reduction in leaf size) to grow fast and dominate the plant community.

Researchers from Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences measured and analyzed the ecosystem C exchange by using closed static chamber method at daily and seasonal intervals in the south margin of the Gurbantunggut Desert. They also investigated soil moisture and temperature, photosynthetically active radiation (PAR) and plant biomass at the same time.

During the whole growing season, the dominant plant functional group shifted from the spring annuals to summer annuals and perennials. Both of soil temperature and moisture exhibited strong seasonal dynamics, with the peak value of soil temperature occurring in late June and the peak values of soil moisture occurring in the snow-melting phase and in October. Soil temperature had a significant effect on C release into the atmosphere from the ecosystem during the snow-melting phase (from mid-March to early April). Net ecosystem C exchange (NEE) was positively correlated with soil moisture and plant biomass during the spring annual dominant phase, but negatively correlated with soil temperature in the snow-melting phase, spring annuals dominant phase, and summer annuals and perennials dominant phase. The diurnal pattern of NEE was consistent with the pattern of PAR from mid-March to early April. Furthermore, the ecosystem acted as a weak C source during this phase.

The result was published in Journal of Vegetation Science in March 2015.

Contact

Prof. HUANG Gang

State Key Lab of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, China

E-mail: hg@ms.xjb.ac.cn