Comparison of soil organic carbon and nitrogen dynamics between urban impervious surfaces and vegetation

Abstract

Impervious surfaces (IS) are widespread globally due to increasing urbanization, and relatively static carbon (C) and nitrogen (N) processes are usually expected in these soils. However, an understanding of how soil organic carbon (SOC) and soil organic nitrogen (SON) dynamics under IS in comparison with urban vegetation is still lacking.Here we used soil fractionation and stable isotopic analysis to examine C and N dynamics in IS soils and soils that were vegetated for 20-30 years in Guangzhou and Shenzhen, China. Soil samples from bare land (CK) and other land uses (grass, forest, and IS) were split into different chemical fractions. The C and N content, C:N ratio, δ 13 C, δ 15 N, C and N recalcitrant indices (RIC, RIN), and mean residence time (MRT) were analyzed. The results showed that soil C and N stocks increased in the first (20 years) as reflected in the enhanced labile (LP) and recalcitrant C pools (RP), but then stabilized or decreased after 30 years with the IS ages in both cities. IS had a lower SOC decomposition rate and thus resulted in 5-10-times longer MRT (259-465 years) than that in vegetated soils (39-55 years). The study showed that IS caused remarkable changes in soil C and N pools and turnover rates compared with vegetated lands. Our results are potentially useful for better understanding, predicting, and managing soil C dynamics under urbanization. K E Y W O R D S grass, impervious surfaces, SOC turnover, urban forest, δ 13 C and δ 15 N 1 | INTRODUCTION Urban expansion has changed the natural landscape by transforming the natural and/or semi-natural lands into impervious surface (IS), which are characterized by high spatiotemporal heterogeneity in both

Methodological Approaches and Literature Analysis in the Study of Soil Carbon in Urban Green Spaces: A Systematic Review

“…The included studies examined soil carbon using both direct and indirect approaches. Direct studies explicitly focused on carbon stock analysis in urban green areas [4,17,18,21,25,28,[48][49][50][51][52][53][54][55][56][57][58][59][60][61]. The indirect studies deviated from a specific focus on soil carbon as a central theme.…”

“…As mentioned in the introduction, a predominant focus on soil carbon has been studied in the form of SOC [1,2,4,[16][17][18][19]21,22,[26][27][28][29]43,45,[48][49][50][51][52][54][55][56][57][58][59][60][61][62]65,67,[69][70][71][72]74,76,[80][81][82][83] and in the form of Total Carbon [25,50,51,63,65,66,68,73,75,[77]…”

“…In terms of the methodology, there majority of the articles reported in situ sampling in soils of urban green areas. Many of these studies were based solely on in situ measurements [1,2,16,18,21,22,29,43,49,[52][53][54]56,[58][59][60][61][62][63][64][65][66][67][68][70][71][72][73][74][75][76]78,80,81,83,85]. Some researchers complement this approach with other methods such as remote sensing imagery [4,26,27,57], open data [26,28,45,79,84], logarithmic modelling [17,31,48,50,…”

“…In the analyses carried out using in situ measurements, a discrepancy was found in the criteria used for soil sampling depth. While the prevailing trend was to focus on the upper 0-20 or 0-30 cm soil depth [1,4,18,27,28,31,49,54,[56][57][58][59]62,63,65,69,71,72,75,82,83], there were also studies that consider the superficial soil layers, specifically 0-5 cm [21,76], or 0-10 cm [22,29,43,53,64,68,70,85]. Furthermore, some studies even considered in situ sampling at soil depths greater than 50 cm [2,16,17,25,26,45,48,50,52,60,67,74,[78][79][80]84].…”

“…Other studies found focused on urban horticultural spaces, community gardens, and allotment gardens [16,17,27,28,31,71,82], cultivated farmland [31,48,77], residential gardens [21,43,63,69,74], urban grasslands [1,4,49,59,70,76], green roofs [84], shrublands [4], roadsides and road greenbelt [75; 69; 85; 43; 76; 28], educational areas, university campuses or experimental centers [2,28,31,43,50,69,76], infiltration and vegetated swales [83], car parks [84], construction sites [77], bare land [77], and even cemeteries [31]. Wetlands [48,52,63,77] and mangroves [79] were also considered.…”