[Impact of Climate Warming on Paddy Soil Organic Carbon Change in the Sichuan Basin of China].

Climate warming can increase soil temperature and lead to soil carbon release, but it can also increase soil organic carbon by increasing primary productivity. Cropland soils are considered to have a huge potential to sequester carbon; however, direct observations for the responses of cropland soil organic carbon to climate warming over broad geographic scales are rarely documented. Paddy soil is one of the important cultivated soils in China. Based on the data of 2217 sampling points obtained during the second national soil survey and the data of 2382 sampling points collected during 2017-2019, this study analyzed the change characteristics of soil organic carbon content of paddy surface soil in Sichuan Basin of China and explored the relationships between the soil organic carbon change of paddy soil and temperature, precipitation, cropland use type, fertilization intensity, and grain yield. The results showed that the content of soil organic carbon of paddy soil changed from 13.33 g·kg-1to 15.96 g·kg-1, with an increase of 2.63 g·kg-1, suggesting that soils in the Sichuan Basin have acted as a carbon sink over past 40 years. The soil organic carbon increment of paddy soil varied with different geomorphic regions and different secondary basins. The increase in SOC content in paddy soil was positively correlated with annual average temperature; negatively correlated with annual average precipitation; and initially increased and then decreased with annual average fertilizer application, annual average increase rate of fertilizer application, annual average grain yield, and annual average grain yield growth rate. The relationship between the increase in SOC content and the annual average temperature growth rate was different under different farmland utilizations, and the increase in the annual average temperature growth rate had significant effects with the increase in SOC content only on paddy-dryland rotation. These results indicate that the paddy soil organic carbon change in Sichuan Basin was co-affected by various factors, but climate warming was an important factor leading to the paddy soil organic carbon change, and its influence was controlled by the water conditions determined by farmland use.

[Spatial heterogeneity of soil hydrolase activities and their influencing factors in a typical Karst catchment of Guizhou Province, China.] / å–€æ–¯ç‰¹å ¸åž‹é›†æ°´åŒºåœŸå£¤æ°´è§£é ¶æ´»æ€§ç©ºé—´å¼‚è´¨æ€§åŠå ¶å½±å“å› ç´ .

Soil enzyme activities are sensitive indicators of soil quality. However, their spatial hetero-geneity and the influencing factors are not well known. In this study, geostatistics, Kriging method, one-way ANOVA and correlation analyses were used to examine the spatial variability and influencing factors of activities of six soil hydrolases: ß-1,4-glucosidase (ßG), ß-1,4-xylosidase (ßX), cellobiohydrolase (CBH), ß-1,4-N-acetylglucosaminidase (NAG), leucine amino peptidase (LAP), and acid phosphatase (AP) in 0-10 cm soil layers in a karst catchment in Guizhou Pro-vince, China. The results showed that the activities of those soil hydrolase had different spatial hete-rogeneity. The optimal models were the spherical models for ßX, CBH and AP, the Gaussian model for ßG and NAG, and the exponential model for LAP, respectively. The spatial structure ratios C/(C0 +C) of ßG, ßX, CBH, NAG and LAP activities were 99.9%, 99.9%, 99.9%, 76.3% and 96.6%, respectively, implying strong spatial autocorrelation and weak influence from topographic factors. The spatial structure ratio of AP activity was 50.0%, suggesting moderate spatial autocorrelation and vulnerable to the influences of random factors. The variation ranges of the hydrolase acti-vities were greater than the sampling distance, indicating that the sampling methods could mirror spatial variability of the soil enzyme activities at a small watershed scale. Land use type significantly affected the activities of NAG and AP. Slope position significantly affected AP activity. The activity of AP was negatively correlated with soil pH, while the activities of other enzymes except NAG were positively correlated with soil pH. Our results provided useful information on the spatial distribution mechanism of soil hydrolase.

[Effects of Myospalax baileyi disturbance on plant community at alpine meadow in Three Rivers Headwater Region, China.] / é«˜åŽŸé¼¢é¼ å¹²æ‰°å¯¹ä¸‰æ±ŸæºåŒºé«˜å¯’è‰ç”¸ç¾¤è½ç‰¹å¾çš„å½±å“.

Plateau zokor (Myospalax baileyi) is one of the major rodent species at the alpine meadow in Three Rivers Headwater Region. They eat plant roots, excavate many tunnels and deposit soil on the surface, which result in many exposed mounds to cover the aboveground part of plants. Here, taking plateau zokor mound density in a plot as their disturbance degree, we selected seven plots with different plateau zokor mound densities and one control plot which was not disturbed by plateau zokor to explore the effects of M. baileyi disturbance on community composition, species diversity and productivity. The results showed that, with the increases of available mound density, the dominant species were changed from Cyperaceae and Gramineae species to forb species, including Poly-gonum viviparum, Potentilla anserine, and Polygonum sibiricum. The community coverage and height were significantly decreased. Light or intermediate disturbance by plateau zokor improved species diversity, whereas the evenness index showed no significant change. The changes of community productivity did not support the 'intermediate disturbance hypothesis'. With the increases of plateau zokor disturbance, the aboveground biomass, belowground biomass, total biomass of community significantly decreased. Our findings revealed the effects of plateau zokor's activity on plant community at alpine meadow and presented important information for the management and restoration of degraded grassland and the sustainable utilization of grassland in Three Rivers Headwater Region.

Surface modeling of soil antibiotics.

Large numbers of livestock and poultry feces are continuously applied into soils in intensive vegetable cultivation areas, and then some veterinary antibiotics are persistent existed in soils and cause health risk. For the spatial heterogeneity of antibiotic residues, developing a suitable technique to interpolate soil antibiotic residues is still a challenge. In this study, we developed an effective interpolator, high accuracy surface modeling (HASM) combined vegetable types, to predict the spatial patterns of soil antibiotics, using 100 surface soil samples collected from an intensive vegetable cultivation area located in east of China, and the fluoroquinolones (FQs), including ciprofloxacin (CFX), enrofloxacin (EFX) and norfloxacin (NFX), were analyzed as the target antibiotics. The results show that vegetable type is an effective factor to be combined to improve the interpolator performance. HASM achieves less mean absolute errors (MAEs) and root mean square errors (RMSEs) for total FQs (NFX+CFX+EFX), NFX, CFX and EFX than kriging with external drift (KED), stratified kriging (StK), ordinary kriging (OK) and inverse distance weighting (IDW). The MAE of HASM for FQs is 55.1 µg/kg, and the MAEs of KED, StK, OK and IDW are 99.0 µg/kg, 102.8 µg/kg, 106.3 µg/kg and 108.7 µg/kg, respectively. Further, RMSE simulated by HASM for FQs (CFX, EFX and NFX) are 106.2 µg/kg (88.6 µg/kg, 20.4 µg/kg and 39.2 µg/kg), and less 30% (27%, 22% and 36%), 33% (27%, 27% and 43%), 38% (34%, 23% and 41%) and 42% (32%, 35% and 51%) than the ones by KED, StK, OK and IDW, respectively. HASM also provides better maps with more details and more consistent maximum and minimum values of soil antibiotics compared with the measured data. The better performance can be concluded that HASM takes the vegetable type information as global approximate information, and takes local sampling data as its optimum control constraints.