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Soil easily oxidizable organic carbon (EOC) is directly related to CO2 density; dynamics in subsurface EOC have been observed globally in relation to rapid urbanization. However, in the context of rapid urbanization, the factors related to EOC and the response of the EOC pool to urbanization down the profile remain elusive. The aim of the current paper is to investigate possible changes in the distribution of EOC over the soil profile and the impact of land use, socioeconomic, and natural factors on these. The study used samples from 182 soil profiles (0–100 cm) taken in the peri-urban areas of the megacity Chengdu (a typical megacity with rapid urbanization). Main drivers of changes in soil EOC were analyzed by using spatial and regression analyses. Closer to the centre of the city, soil EOC levels were lower and land-use factors and socioeconomic factors contributed more to explaining variation in EOC levels in the 0–40-cm layer, whereas natural factors were most important at larger distance from the city. The effect of land-use factors and socioeconomic factors on EOC reached down to 60-cm depths. Moreover, an estimated 20% loss of EOC stock was observed close to the city in comparison with the surroundings, suggesting that the rapid process of urbanization was accompanied by a loss of EOC stock down the profile to depths of 60 cm, and the negative effects on EOC stock became more intensive as the distance to the city decreased.

Seed germination is a fundamental process in the plant life cycle and is regulated by functionally opposing internal and external inputs. Here we explored the role of a negative regulator of photomorphogenesis, a B-box-containing protein (BBX19), as a molecular link between the inhibitory action of the phytohormone abscisic acid (ABA) and the promoting role of light in germination. We show that seeds of BBX19-overexpressing lines, in contrast to those of BBX19 RNA interference lines, display ABA hypersensitivity, albeit independently of elongated hypocotyl 5 (HY5). Moreover, we establish that BBX19 functions neither via perturbation of GA signaling, the ABA antagonistic phytohormone, nor through interference with the DELLA protein germination repressors. Rather, BBX19 functions as an inducer of ABA INSENSITIVE5 (ABI5) by binding to the light-responsive GT1 motifs in the gene promoter. In summary, we identify BBX19 as a regulatory checkpoint, directing diverse developmental processes and tailoring adaptive responses to distinct endogenous and exogenous signals.