Abstract
An in-depth understanding of the dominant factors controlling soil respiration is important to accurately estimate carbon cycling in forest ecosystems. However, information on variations in soil respiration at different soil depths and the influencing factors in forest is limited. This study examined the variations in soil respiration at two soil depths (0–10 and 10–20 cm) as well as the effects of soil temperature, soil water content, litter removal, and root cutting on soil respiration in three typical forest types (i.e., Pinus tabulaeformis Carrière, Platycladus orientalis (L.) Franco, and Quercus variabilis Bl.) in the mountainous area of north China from March 2013 to October 2014. The obtained results show that soil respiration exhibited strong seasonal variation and decreased with soil depth. Soil respiration was exponentially correlated to soil temperature, and soil respiration increased with soil water content until reaching threshold values (19.97% for P. tabulaeformis, 16.65% for P. orientalis, and 16.90% for Q. variabilis), followed by a decrease. Furthermore, interactions of soil temperature and water content significantly affected soil respiration at different soil depths of forest types, accounting for 68.9% to 82.6% of the seasonal variation in soil respiration. In addition to soil temperature and water content, aboveground litter and plant roots affected soil respiration differently. In the three forest types, soil respiration at two soil depths decreased by 22.97% to 29.76% after litter removal, and by 44.84% to 53.76% after root cutting. The differences in soil respiration reduction between the two soil depths are largely attributed to variations in substrate availability (e.g., soil organic content) and soil carbon input (e.g., litter and fine root biomass). The obtained findings indicate that soil respiration varies at different soil depths, and suggest that in addition to soil temperature and water content, soil carbon input and dissolved organic substances may exert a strong effect on forest soil respiration.
Highlights
With the rapid development of industrialization and the continuous growth of its population, China has become one of the world’s largest emitters of greenhouse gases [1]
In these three forest types, fine root (5mm) was found in the Platycladus orientalis (PO) plot
This study showed that differences in soil respiration at different soil depths exist in typical forests in the mountainous area of north China
Summary
With the rapid development of industrialization and the continuous growth of its population, China has become one of the world’s largest emitters of greenhouse gases [1]. The increase of CO2 concentration can directly break the dynamic balance of the carbon cycle and cause ecological and environmental problems, such as global warming [2]. As the second largest contributor of CO2 flux between terrestrial ecosystems and the atmosphere, soil respiration plays an important role in global carbon cycling [3,4]. Forests 2019, 10, 1081 even a slight variation in soil respiration can significantly influence both the atmospheric CO2 concentration and carbon cycling [2,6]. Predicting soil respiration and identifying the driving environmental factors are of considerable importance to improve carbon cycle models and evaluate the potential effects of global warming on terrestrial ecosystems
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