Abstract
Atmospheric nitrogen (N) and acid deposition have become global environmental issues and are likely to alter soil respiration (Rs); the largest CO2 source is from soil to the atmosphere. However, to date, much less attention has been focused on the interactive effects and underlying mechanisms of N and acid deposition on Rs, especially for ecosystems that are simultaneously subjected to elevated levels of deposition of both N and acid. Here, to examine the effects of N addition, acid addition, and their interactions with Rs, we conducted a two-way factorial N addition (control, CK; 60 kg N ha−1 a−1, LN; 120 kg N ha−1 a−1, HN) and acid addition (control, CK; pH 4.5, LA; pH 2.5, HA) field experiment in a subtropical plantation in China. Our results showed the following: (1) During the one-year observation period, the seasonal dynamics of Rs presented a single peak curve model, which was closely related to the surface soil temperature. (2) The simulated N deposition and acid deposition significantly decreased the Rs in the subtropical plantation. Compared to the CK plots, the LN and HN treatments reduced the annual mean values of Rs by 41% and 56%, and the annual mean values of Rs were inhibited by 26% and 31% in the LA and HA plots. The inhibition of N application on Rs was stronger than that of the simulated acid deposition. (3) Significant interactions between N addition and acid addition on Rs were detected, and Rs was significantly inhibited under four co-addition treatments. (4) The underlying mechanism and main reason for the responses of Rs to simulated N and acid deposition in this study might be the inhibition of soil microbial biomass and soil enzyme activity due to soil acidification under increased N and acid input.
Highlights
Over the past century, atmospheric nitrogen (N) and acid deposition have become global environmental issues, and climate change models predict that atmospheric N deposition and acid deposition will continue to increase within subtropical regions [1,2,3]
The main objectives of this study were to (1) investigate how Rs responds to N deposition and acid deposition; and (2) to explore how soil environmental and biotic factors control the responses of Rs to N deposition and acid deposition
Simulated N deposition, acid deposition, and the co-addition of N and acid significantly decreased the Rs rates in a subtropical plantation in our study, which differed from temperate forests
Summary
Atmospheric nitrogen (N) and acid deposition have become global environmental issues, and climate change models predict that atmospheric N deposition and acid deposition will continue to increase within subtropical regions [1,2,3]. Acid rain deposition has recently declined in developed countries, but it is continuously increasing in developing regions and countries, . With acidic depositional areas accounting for 30% of its land area [3]. The center of the most severe acid rain area, the area south of the Yangtze River, moved eastwards [1,3]. Jia and Gao [8] reported that the red soil region of southern China is known to be heavily polluted with acid deposition. Some researchers have suggested that sulfur (S) deposition in China started to decrease as early as
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