Higher carbon sequestration potential and stability for deep soil compared to surface soil regardless of nitrogen addition in a subtropical forest

Abstract

Background Labile carbon input could stimulate soil organic carbon (SOC) mineralization through priming effect, resulting in soil carbon (C) loss. Meanwhile, labile C could also be transformed by microorganisms in soil as the processes of new C sequestration and stabilization. Previous studies showed the magnitude of priming effect could be affected by soil depth and nitrogen (N). However, it remains unknown how the soil depth and N availability affect the amount and stability of the new sequestrated C, which complicates the prediction of C dynamics. Methods A 20-day incubation experiment was conducted by adding 13C labeled glucose and NH4NO3 to study the effects of soil depth and nitrogen addition on the net C sequestration. SOC was fractioned into seven fractions and grouped into three functional C pools to assess the stabilization of the new sequestrated C. Results Our results showed that glucose addition caused positive priming in both soil depths, and N addition significantly reduced the priming effect. After 20 days of incubation, deep soil had a higher C sequestration potential (48% glucose-C) than surface soil (43% glucose-C). The C sequestration potential was not affected by N addition in both soil depths. Positive net C sequestration was observed with higher amount of retained glucose-C than that of stimulated mineralized SOC for both soil depths. The distribution of new sequestrated C in the seven fractions was significantly affected by soil depth, but not N addition. Compared to deep soil, the new C in surface soil was more distributed in the non-protected C pool (including water extracted organic C, light fraction and sand fraction) and less distributed in the clay fraction. These results suggested that the new C in deep soil was more stable than that in surface soil. Compared to the native SOC for both soil depths, the new sequestrated C was more distributed in non-protected C pool and less distributed in biochemically protected C pool (non-hydrolyzable silt and clay fractions). The higher carbon sequestration potential and stability in deep soil suggested that deep soil has a greater role on C sequestration in forest ecosystems.

Effects of defoliation and nitrogen on carbon dioxide (CO2) emissions and microbial communities in soils of cherry tree orchards

“…4 and 5 ), (ii) relatively sufficient nutrients in top and middle soils, and (iii) suitable pH and favorable soil structure and properties in top and middle soils ( Wang et al, 2014 ; Tian et al, 2016b ), which provided advantageous conditions for the decomposition of deciduous residues by microbes. Conversely, PI was higher in deep soils than in top and middle soils in our study, concurrent with the result of a prior study ( Liao et al, 2020 ). The proportion of residual organic carbon was calculated based on the input amount of organic carbon and emission amount of CO 2 in soils at different depths, which exhibited that the proportion of residual organic carbon was 88.88%, 88.05%, and 80.60% in top, middle, and deep soils, respectively.…”

“…Soil depth is frequently associated with new increases in CO 2 emissions ( Meyer et al, 2018 ; Liao et al, 2020 ). Throughout the incubation period, the CO 2 efflux rates and cumulative CO 2 emissions were higher in top and middle soils than in deep soils, which might be explained by the following factors: (i) high MBC and activities of soil catalase, alkaline phosphatase, and cellulase in top and middle soils ( Figs.…”

“…Responses of soil CO 2 emissions to different environments are variable because of different soil environments and physicochemical characteristics in soils at varying depths ( De Graaff et al, 2014 ; Tian et al, 2016b ; Liao et al, 2020 ). In top soils (≤10 cm), large amounts of SOC are produced and CO 2 emissions are increased because of litter, fertilization, soil fungi, bacteria, and animals ( Blanco-Canqui & Lal, 2008 ; Tian et al, 2016b ; Banfield et al, 2018 ).…”

Spatio-temporal distribution dynamics of diverse soil nitrogen pools and patterns of nitrogen and carbon sequestration after slope farmland conversion to Zanthoxylum bungeanum plantations

“…The arid regions of Southwest China, such as the transition zone between Sichuan Basin and the eastern edge of the Qinghai-Tibet Plateau, the hotspots of land degradation, have experienced a massive landuse conversion of marginal farmlands (FL) to forest plantations under grain for green program of China (GGP) (Cheng et al, 2015;Liao et al, 2020). However, previous research on FL conversion in this region has mostly emphasized soil C accumulation; apart from total N (TN), other N cycling variables are rarely reported.…”

“…Gregory et al (2016) also reported higher C and N sequestration potential of deep soil Liao et al (2020). reported that C and N pools in the subsoil (below 0-30 cm) are assumed to be more stable than the topsoil due to differences in the composition of SOM and environmental conditions.…”