Abstract
ABSTRACT Soil respiration represents the largest flux of CO2 emission from terrestrial ecosystems, being affected by land-use changes and soil properties. There are few studies investigating the response of soil respiration to land-use changes in the Caatinga biome. This study aimed to measure soil respiration from Caatinga vegetation and degraded pasture, to verify the effect of land-use changes on soil respiration. Measurements of soil respiration were performed using the infrared gas analyzer method over nine months (in rainy and dry seasons), in Caatinga and degraded pasture in the semi-arid region of Pernambuco. The soil moisture, soil temperature, soil organic carbon (SOC), Normalized Difference Vegetation Index (NDVI), and climatic variables were also measured. Soil organic carbon and NDVI were higher in Caatinga than in degraded pasture, while the inverse occurred with soil temperature. The soil respiration showed a clear seasonal variation, with the highest values occurring in the wet season, being positively correlated with soil moisture and negatively with soil temperature. Soil respiration was significantly higher in the Caatinga (8.0 ton ha-1 yr-1 of C) than in degraded pasture (3.7 ton ha-1 yr-1 of C). These higher values of soil respiration in Caatinga were due to lower soil temperature and higher SOC, and can be seen as indicators of good environmental quality.
Highlights
The CO2 emission from the soil surface, commonly referred to as soil CO2 efflux (ECO2) or soil respiration (SR), is the sum of processes that include the production of CO2 by roots, micro-organisms, and soil fauna throughout the soil profile, and the subsequent diffusion of CO2 to the soil surface (Bond-Lamberty and Thomson, 2010; Ferreira et al, 2018)
This flux has great importance for the global carbon balance, returning from 80 to 98 Pg of C to the atmosphere each year (Raich et al, 2002; Bond-Lamberty and Thomson, 2010), which is more than 11 times that CO2 emission from fossil fuel combustion (Peng et al, 2009; Xu and Shang, 2016)
Rainfall higher than 20 mm occurred on 07 dates (2/20/2017; 3/9/2017; 3/17/2017; 3/31/2017; 4/2/2017; 4/11/2017; and 5/31/2017) and accounted for 50 % of the total rainfall in the studied period (Figure 2)
Summary
The CO2 emission from the soil surface, commonly referred to as soil CO2 efflux (ECO2) or soil respiration (SR), is the sum of processes that include the production of CO2 by roots, micro-organisms, and soil fauna throughout the soil profile, and the subsequent diffusion of CO2 to the soil surface (Bond-Lamberty and Thomson, 2010; Ferreira et al, 2018) This flux has great importance for the global carbon balance, returning from 80 to 98 Pg of C to the atmosphere each year (Raich et al, 2002; Bond-Lamberty and Thomson, 2010), which is more than 11 times that CO2 emission from fossil fuel combustion (Peng et al, 2009; Xu and Shang, 2016). Arid and semiarid ecosystems may dominate the trajectory of biosphere-to-atmosphere carbon (C) exchange, and understanding SR in these ecosystems is important for C cycling at the global scale and to ensure the accurate representation in large-scale carbon models (Wang et al, 2014; Tucker and Reed, 2016)
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