Significant loss of soil inorganic carbon at the continental scale.

Widespread soil acidification due to atmospheric acid deposition and agricultural fertilization may greatly accelerate soil carbonate dissolution and CO2 release. However, to date, few studies have addressed these processes. Here, we use meta-analysis and nationwide-survey datasets to investigate changes in soil inorganic carbon (SIC) stocks in China. We observe an overall decrease in SIC stocks in topsoil (0-30 cm) (11.33 g C m-2 yr-1) from the 1980s to the 2010s. Total SIC stocks have decreased by ∼8.99 ± 2.24% (1.37 ± 0.37 Pg C). The average SIC losses across China (0.046 Pg C yr-1) and in cropland (0.016 Pg C yr-1) account for ∼17.6%-24.0% of the terrestrial C sink and 57.1% of the soil organic carbon sink in cropland, respectively. Nitrogen deposition and climate change have profound influences on SIC cycling. We estimate that ∼19.12%-19.47% of SIC stocks will be further lost by 2100. The consumption of SIC may offset a large portion of global efforts aimed at ecosystem carbon sequestration, which emphasizes the importance of achieving a better understanding of the indirect coupling mechanisms of nitrogen and carbon cycling and of effective countermeasures to minimize SIC loss.

Spatial Distribution of Soil Phosphorus, Calcium, and pH after Long-term Broiler Litter Application.

Water movement over and through soil is largely driven by topography and soil management across landscapes. This research tested the hypothesis that the water movement determines the potential for P and Ca redistribution and pH variance across landscapes. This hypothesis was evaluated by using digital elevation model-derived terrain attributes in fields after 55 yr of broiler litter applications on pastures in Smith County, Mississippi. Results show that soils receiving broiler litter had mean Mehlich-3 P levels of 1221.8 mg kg at 0- to 15-cm depth and 618.6 mg kg at 15- to 30-cm depth, and Ca with mean values of 768.3 and 645.0 mg kg at 0- to 15-cm and 15- to 30-cm soil depths, respectively. Across fields, soils in areas of predicted convergent flow contained higher P, Ca, and lower pH values in the upper 0 to 15 cm, suggesting contributions via surface overland flow from areas with higher elevation and lower slope gradient. On the other hand, soils in areas with lesser slope and higher elevation also contained high levels of P, Ca, and pH for the subsurface soil depth, suggesting that vertical flow of water on this landscape is a mechanism for movement of P and Ca deeper in the profile. The incorporation of topographic characteristics across fields offers promising results that may be incorporated into improved P indices and management, making them more robust indicators of P mobilization to waterways.

Influences of shale gas well-pad development on land use and vegetation biomass in a shale gas mining area.

It is not clear how shale gas mining would affect land use change and vegetation biomass in the villages and farmlands where was substantially influenced by human activities around the well-pads of the shale gas mining areas in Sichuan Province. Using remote sensing and image interpretation in 2012 and 2017 and in situ vegetation investigation data in 2017, we analyzed the changes of land use and biomass in well-drilling fields and buffer zones and further examined the extent affected by well-drilling and subsequently vegetation biomass loss. The results showed that shale gas mining had converted 93.81 hm2 of land to mining land from 2012 to 2017, among which almost half (48.6%) was dry land (about 45.61 hm2), 17.2% forest land (16.13 hm2), 11.0% residential land (10.28 hm2), and 11.1% shrubland (10.39 hm2). The extent affected by well-drilling ranged from 0 to 50 m at the early stage, which decreased at the stage of stable gas production. As a result of well-drilling, over 2477.53 t of vegetation biomass was lost, of which 71.6% being accounted for by the well-drilling fields and the remaining (28.4%) being caused by road construction and temporary land use. Direct occupation of dry land and forested land by shale gas well-pads mainly caused land use changes and biomass losses in this shale gas mining area. Our results have implications for ecological environment management and shale gas sustainable mining in this area.

[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 urban sprawl on arthropod communities in peri-urban farmed landscape in Shenbei New District, Shenyang, Liaoning Province, China.

Peri-urban farmland provides a diversity of ecological services. However, it is experiencing increasing pressures from urban sprawl. While the effects of land use associated with farming on arthropod assemblages has received increasing attention, most of this research has been conducted by comparing conventional and organic cropping systems. The present study identifies the effects of urban sprawl and the role of non-cropped habitat in defining arthropod diversity in peri-urban farmed landscapes. Multi-scale arthropod data from 30 sampling plots were used with linear-mixed models to elucidate the effects of distance from urban areas (0-13 km; 13-25 km and >25 km, zones I, II, and III, respectively) on arthropods. Results showed that urban sprawl, disturbed farm landscapes, and disturbance in non-cropped habitats had negative effects on arthropods, the latter requiring arthropods to re-establish annually from surrounding landscapes via dispersal. While arthropod species richness showed no obvious changes, arthropod abundance was lowest in zone II. Generally, patch density (PD), Shannon diversity index (SHDI), and aggregate index (AI) of non-cropped habitat were major drivers of changes in arthropod populations. This study contributes to identifying the effects of urban sprawl on arthropod diversity and documenting the multiple functions of farm landscapes in peri-urban regions.

[Cooperative relations between non-cropped habitats and soil animals in suburban farmland Landscape: A case in Shenbei New District in Shenyang, China].

Non-cropped habitat in farm landscape plays a significant role in biodiversity, the functions of arable land and crop yields. This study focused on Shenbei New District in Shenyang City of Liaoning Province in Northeast China, which was a typical area with contradiction between biodiversity conservation and the high demand of agricultural production in the process of urbanization. Information entropy model, hand-picking and Baermann method were used for survey and identification of arthropods and nematodes in soils in urban suburban (US), urban fringe area (UFA) and rural area ( RA). The cooperative relations between the number of soil animals and types, structure as well as the total amount of non-cropped habitat were investigated in these three types of areas using linear regression. Our results showed that the area of single patch in non-cropped habitat was smaller than one hectare in Shenbei New District, and the types and the proportion of non-cropped habitat patches were increasing along with the increase of their distance to the urban center. But the proportion of non-cropped habitats areas appeared under an inverted U-type change. The proportion of non-cropped habitat patches was from 8.6% to 27.8%. The individual number of soil animals showed the U-type trend, while their species number changed irregularly. The individual number of soil animals increased with the increase of the proportion of non-cropped habitat patches in RA and US. There was no obvious correlation between the individual number of soil animal and the proportion of non-cropped habitat patches in UFA. The individual number of soil animals decreased with the increase of the proportion of non-cropped habitats areas. There was no cooperative relation in the proportion of non-cropped habitats and the number of soil animal species.

[Effects of applying different kind fertilizers on enzyme activities related to carbon, nitrogen, and phosphorus cycles in reddish paddy soil].

Based on the long-term fixed position experimental data from Qianyanzhou Ecological Experiment Station, Chinese Academy of Sciences in 1998, this paper analyzed the effects of applying different kind fertilizers (straw, ST; pig manure, OM; and chemical fertilizer, NPK) on the nutrients (C, N, and P) status and the activities of related enzymes ( beta-1,4-glucosidase, betaG; beta-1,4-N-acetylglucosaminidase, NAG; L-leucine aminopeptidase, LAP; and acid phosphatase, AP) in reddish paddy soil. With the application of OM, the activities of soil betaG, NAG, and LAP increased significantly, as compared with other treatments, and were 1.4, 2. 6, and 1.9 times higher than the control (CK) , respectively. Applying OM also improved the ratio of soil organic carbon to total nitrogen (C/N), but decreased the soil betaG/(NAG+LAP) ratio, suggesting that pig manure could benefit the degradation of soil cellulose and the accumulation of soil organic carbon. Applying NPK increased the activities of soil betaG, NAG, and LAP, but decreased the AP activity, with a decrement of 34% as compared with CK. Under the application of NPK, the soilbetaG/AP and (NAG+ LAP)/AP ratios increased, but the ratios of soil organic carbon to total phosphorus (C/P) and of soil total nitrogen to total phosphorus (N/P) decreased, indicating that chemical fertilizers could induce the accumulation of soil inorganic phosphorus, and inhibit the microbial functions of degrading polysaccharides and phosphate phospholipids.

[Spatial variability of soil total K and available N in Shenyang urban area].

Geostatistics combined with geographical information system (GIS) was applied to analyze the spatial variability of soil total K and available N in urban area of Shenyang City. The results showed that the theoretical semivariogram models of soil total K was best described by an exponential model, while soil available N was best fitted by a Gaussian model. The ratios of nugget to sill of soil total K and available N were 10.65% and 17.96%, respectively, indicating that there existed significant spatial correlations between soil total K and available N, and the spatial variability was mainly caused by structural factors. The spatial distributions of soil total K and available N in urban area of Shenyang were analyzed by kriging interpolation, and it was found that the content of soil total K had no definite spatial distribution pattern, while the content of soil available N was higher in the around and lower in the middle of the city.