Abiotic regulators of soil respiration in desert ecosystems

Soil temperature and soil moisture are the most important environmental factors controlling soil respiration in mesic ecosystems. However, soil respiration and associated abiotic regulators have been poorly studied in desert ecosystems. In this study, soil respiration was measured using an automated CO₂ efflux system (LI-COR 8100), and the effects of soil temperature and moisture on the rate of soil respiration were examined in six desert sites three communities—Haloxylon ammodendron, Halostachys caspica and Anabasis aphylla at high (B) and low (A) vegetation coverage respectively]. It was found that soil respiration was significantly and positively correlated with soil surface temperature. A multi-variable model of soil temperature and soil moisture could explain 61.9% of temporal variation in soil CO₂ efflux at a larger scale. There were significantly negative correlations between soil respiration and soil moisture in Haloxylon ammodendron B and Halostachys caspica B sites, which represented the driest and wettest sites, respectively. The results also showed that soil respiration displayed obvious diurnal and seasonal patterns during the growing season. The Q₁₀ values for Haloxylon ammodendron A and B, Halostachys caspica A and B, and Anabasis aphylla A and B sites were 1.3, 1.34, 1.58, 1.65, 1.31 and 1.17, respectively, with a cross-site average of 1.39. The results showed that soil respiration was not positively correlated with soil moisture unlike in most mesic ecosystems. However, soil respiration in desert ecosystems is less sensitive to temperature variation than most mesic ecosystems as indicated by the lower Q₁₀ values possibly due to energy limitation.