Exploring the contrasting lake CO fluxes and influencing variables in four large shallow subtropical lakes with different hydrological connectivity.

Lake carbon dioxide (CO) evasion is a crucial component of global carbon cycle, yet the influence of environmental factors on CO emissions within different hydrological connectivity remains uncertain. Based on multiple machine learning methods, we investigated seasonal and annual CO fluxes, and the discrepancy in contributions and threshold behaviors of key variables to CO flux variations, in two river-connected lakes (Hongze and Poyang) and two non-river-connected lakes (Chaohu and Taihu). Random Forest performed well in CO flux simulations, with R values ranging from 0.

Influences of extreme weather events on the carbon to nitrogen ratios of major staple crops.

Carbon (C) and nitrogen (N) contents, along with the corresponding C:N ratios in crops, significantly impact C and N cycles in cropland ecosystems. However, the effects of climate change and the increasing frequency of extreme weather events (EWEs) on the C:N ratios of major crops remain uncertain. Here, we combined field experiments and mathematical modeling to explore the impact of excessive precipitation, precipitation shortage, and heat events on the C and N contents and C:N ratios of rice and wheat in a major grain production base in China.

Drought-Induced Weakening of Temperature Control on Ecosystem Carbon Uptake Across Northern Lands.

Rapid warming in northern lands has led to increased ecosystem carbon uptake. It remains unclear, however, whether and how the beneficial effects of warming on carbon uptake will continue with climate change. Moreover, the role played by water stress in temperature control on ecosystem carbon uptake remains highly uncertain.

Effects of Extreme Weather Events on Nitrous Oxide Emissions from Rice-Wheat Rotation Croplands.

Cropland ecosystems are significant emission sources of NO, but a limited number of studies have focused on the impact of extreme weather events on NO fluxes from cropland. This present study integrated field observations and model simulations to explore the responses of NO fluxes to extreme weather events in typical rice and wheat rotation croplands in the middle and lower reaches of the Yangtze River (MLRYR) in China. The findings revealed that the studied rice-wheat rotation cropland exhibited a net source of NO over the three-year monitoring period, with annual cumulative NO emissions ranging from 190.

Decoding the dramatic hundred-year water level variations of a typical great lake in semi-arid region of northeastern Asia.

Lakes in arid and semi-arid regions are experiencing dramatic variations in water level and volume, which has caused severe ecological and social problems. Long-term study of the lake dynamics in arid/semi-arid regions could provide particular insights into the mechanisms driving lake variations, while hydro-meteorological data were usually limited in these regions, especially before the instrumental period. In the present study, we focused on a typical great lake - Hulun Lake in semi-arid region in northern China, simulated the hydrological processes from 1904 to 2016 using SWAT model, CRUNCEP7 reanalysis data, and sparse records of lake level during 1900s-1950s, and investigated the mechanisms driving the dramatic variations of the lake at the hundred-year time scale.

Surface nitrous oxide concentrations and fluxes from water bodies of the agricultural watershed in Eastern China.

Agriculture is one of major emission sources of nitrous oxide (NO), an important greenhouse gas dominating stratospheric ozone destruction. However, indirect NO emissions from agriculture watershed water surfaces are poorly understood. Here, surface-dissolved NO concentration in water bodies of the agricultural watershed in Eastern China, one of the most intensive agricultural regions, was measured over a two-year period.

Hydraulic redistribution affects modeled carbon cycling via soil microbial activity and suppressed fire.

Hydraulic redistribution (HR) of water from moist to drier soils, through plant roots, occurs world-wide in seasonally dry ecosystems. Although the influence of HR on landscape hydrology and plant water use has been amply demonstrated, HR's effects on microbe-controlled processes sensitive to soil moisture, including carbon and nutrient cycling at ecosystem scales, remain difficult to observe in the field and have not been integrated into a predictive framework. We incorporated a representation of HR into the Community Land Model (CLM4.

[Spatial characteristics of microbial groups associated with the groundwater flow in a small watershed].

Few reports of microbial groups associated with the groundwater flow system are available in China. 16S rRNA gene library was constructed by the cultured-independent approach to investigate gene sequences of microorganism in groundwater samples from the recharge (R), intermediate (M) and discharge (D) zones of an experimental watershed at Zhuhai campus of Sun Yat-sen University. Proteobacterium, Candidate division OPx, uncultured archaeon (uncultured Crenarchaeote and Euryarchaeote) and Actinobacterium are found predominant in all these three zones with the Proteobacterium accounting for 23.