Net carbon exchange and its driving factors of Haloxylon ammodendron plantation in the oasis-desert ecotone of Minqin, China

Abstract

Carbon fluxes in a Haloxylon ammodendron plantation in the oasis-desert ecotone of Minqin was measured using an eddy covariance system. To provide scientific data for carbon source/sink assessment, we quantitatively analyzed the characteristics of CO2 flux and its driving factors in the growing season from May to October, 2018. The results showed that the trend of daily net carbon exchange in the growing season followed a symmetrical "U" shape curve. As to seasonality, bimodal curve was obvious. The plantation ecosystem was a carbon sink every month. The total carbon sequestrated was 34.38 g C·m-2, with the peak of 12.31 g C·m-2 in September and the lowest value of 0.89 g C·m-2 in July. The net carbon exchange in this ecosystem increased during the daytime with the increasing photosynthetically active radiation, consistent with the Michaelis-Menten rectangular hyperbola change. When the vapor pressure deficit was greater than 2.5 kPa, the increasing trend tended to flat. Ecosystem respiration increased exponentially with temperature, with temperature sensitivity being 1.7. Net carbon exchange in either day or night was significantly correlated with soil temperature through the whole growing season.