Variation of soil organic carbon and physical properties in relation to land uses in the Yellow River Delta, China

Abstract

Soil physical properties and soil organic carbon (SOC) are considered as important factors of soil quality. Arable land, grassland, and forest land coexist in the saline-alkali reclamation area of the Yellow River Delta (YRD), China. Such different land uses strongly influence the services of ecosystem to induce soil degradation and carbon loss. The objective of this study is to evaluate the variation of soil texture, aggregates stability, and soil carbon affected by land uses. For each land use unit, we collected soil samples from five replicated plots from “S” shape soil profiles to the depth of 50 cm (0–5, 5–10, 10–20, 20–30, and 30–50 cm). The results showed that the grassland had the lowest overall sand content of 39.98–59.34% in the top 50 cm soil profile. The content of soil aggregates > 0.25 mm (R0.25), mean weight diameter and geometric mean diameter were significantly higher in grassland than those of the arable and forest land. R0.25, aggregate stability in arable land in the top 30 cm were higher than that of forest land, but lower in the soil profile below 20 cm, likely due to different root distribution and agricultural practices. The carbon management index (CMI) was considered as the most effective indicator of soil quality. The overall SOC content and CMI in arable land were almost the lowest among three land use types. In combination with SOC, CMI and soil physical properties, we argued that alfalfa grassland had the advantage to promote soil quality compared with arable land and forest land. This result shed light on the variations of soil properties influenced by land uses and the importance to conduct proper land use for the long-term sustainability of the saline-alkali reclamation region.

Variation in Total Soil Organic Carbon Stocks in Relation to Some Land Use Systems in the Bamenda Highlands, Cameroon

“…SOC negatively correlated with BD, Av.P suggesting that an increase in SOC decreases BD and Av.P and vice versa. This result is in agreement with Jiao et al (2020) who also found negative correlations between SOC and BD. Land use practices and inputs can change the dynamic of soil properties yielding some of these negative relationships.…”

“…The results revealed higher BD in smallholder farms > Grazing land > forest with significant differences between BDs of farmlands and forest. This is in accord with the works of Sahani and Jiao et al (2020), who also recorded higher BD in arable lands. The higher BD in smallholder farms could result from the combined influence of the ploughing in tillage layer, roots distribution, repeated sowing and harvesting, and human activities on the farm.…”

“…While the smallholder farmland with little or no litter, frequent disturbance and strong soil respiration in the surface, may have enhanced SOC consumption in the top 30 cm soil rendering farmland with lowest SOC values. This is in accordance withJiao et al (2020) who also found highest SOC content and stocks in forest land and least in arable land. The significant differences in TOC and SOM observed between the three LUSs are in response to the changes in land use/management practices.…”

“…This leads to easy evaporation of soil moisture. Moisture content between forest and grazing land LUS had no significant difference between them but the higher MC in forest could be due to more surface cover by leave litter (Jiao et al, 2020).…”

“…Soil samples were collected with the aid of a soil hand auger at soil depth of 30cm. The sampling plots of each LUS in a microclimatic zone were distributed according to an "S" shape to cover vertical and horizontal variations (Jiao et al, 2020). At each sampling plot, three soil samples were collected, following a diagonal transect across the plot and bulked to give a homogenous sample for that plot.…”