Climate‐smart agriculture (CSA) management practices (e.g., conservation tillage, cover crops, and biochar applications) have been widely adopted to enhance soil organic carbon (SOC) sequestration and to reduce greenhouse gas emissions while ensuring crop productivity. However, current measurements regarding the influences of CSA management practices on SOC sequestration diverge widely, making it difficult to derive conclusions about individual and combined CSA management effects and bringing large uncertainties in quantifying the potential of the agricultural sector to mitigate climate change. We conducted a meta‐analysis of 3,049 paired measurements from 417 peer‐reviewed articles to examine the effects of three common CSA management practices on SOC sequestration as well as the environmental controlling factors. We found that, on average, biochar applications represented the most effective approach for increasing SOC content (39%), followed by cover crops (6%) and conservation tillage (5%). Further analysis suggested that the effects of CSA management practices were more pronounced in areas with relatively warmer climates or lower nitrogen fertilizer inputs. Our meta‐analysis demonstrated that, through adopting CSA practices, cropland could be an improved carbon sink. We also highlight the importance of considering local environmental factors (e.g., climate and soil conditions and their combination with other management practices) in identifying appropriate CSA practices for mitigating greenhouse gas emissions while ensuring crop productivity.

No abstract

The soil active layer in boreal forests is sensitive to climate warming. Climate-induced changes in the active layer may greatly affect the global carbon budget and planetary climatic system by releasing large quantities of greenhouse gases that currently are stored in permafrost. Ground surface temperature is an immediate driver of active layer thickness (ALT) dynamics. In this study, we mapped ALT distribution in Chinese boreal larch forests from 2000 to 2015 by integrating remote sensing data with the Stefan equation. We then examined the changes of the ALT in response to changes in ground surface temperature and identified drivers of the spatio-temporal patterns of ALT. Active layer thickness varied from 1.18 to 1.3 m in the study area. Areas of nonforested land and low elevation or with increased air temperature had a relatively high ALT, whereas ALT was lower at relatively high elevation and with decreased air temperatures. Interannual variations of ALT had no obvious trend, however, and the ALT changed at a rate of only −0.01 and 0.01 m year −1 . In a mega-fire patch of 79,000 ha burned in 2003, ∆ALT (ALT i − ALT 2002 , where 2003 ≤ i ≤ 2015) was significantly higher than in the unburned area, with the influence of the wildfire persisting 10 years. Under the high emission scenario (RCP8.5), an increase of 2.6-4.8 • C in mean air temperature would increase ALT into 1.46-1.55 m by 2100, which in turn would produce a significant positive feedback to climate warming.

No abstract

No abstract

Land use conversion on river plain has profound impacts on soil characteristics and elemental stoichiometry. Four wetland types (Riparian lower‐beach wetland [RLW], Riparian higher‐beach wetland [RHW], Cultivated wetland [CW] and Mesophytic wetland [MW]) were selected in the lower Yellow River area to investigate the consequence of wetland type conversion on soil carbon (C), nitrogen (N) and phosphorus (P) stoichiometry. The results demonstrated that wetland conversion induced significant spatio‐temporal variations in soil C, N and P stoichiometry and physicochemical characteristics in soil. Frequent agricultural activities (fertilizer input) raised the nutrient content of natural wetland, particularly in surface soil (0–30 cm). Soil volumetric water content (VWC), soil bulk density (SBD), pH and soil enzyme activity varied significantly in different wetlands. Total carbon (TC) and total nitrogen (TN) contents in MW decreased with increasing soil depth (<40 cm layers), as did TN and total phosphorus (TP) contents in CW. On the other hand, TC, TN and TP contents in RLW and RHW did not change significantly with soil depth. However, the contents of TOC, and Fe/Al‐P, etc., varied among soil layers and among wetland types. Furthermore, the stoichiometric characteristics changed significantly in some soil layers, with mean values being less than the Chinese average. Statistically, significant positive correlations were determined between TC and TN (r = .56), TDC and TP (r = .62), N:P and pH (r = .57) (p < .05) and and pH (r = .66, p < .01). VWC was negatively correlated with pH (r = −.56, p < .05), while C/P was negatively associated with soil temperature (ST) and SBD (r = −.55, r = −.64, p < .05). TDC, IP, TN, Fe/Al‐P and ST were identified as the dominant factors, with the percentage of variance 41%, 20%, 12%, 9% and 6% respectively. These findings have a great scientific significance for the ecological conservation of wetlands in the lower Yellow River area.