Ecosystem carbon dioxide (CO₂), water vapor, and heat exchanges in alpine wetlands on the Qinghai–Tibetan Plateau are not comprehensively understood. Thus, we studied variability of net ecosystem CO₂ exchange (NEE), ecosystem respiration (Re), gross primary production (GPP), evapotranspiration (ET), and heat fluxes over a headwater wetland ecosystem in the Qinghai Lake region. Results showed that the headwater wetland ecosystem was net CO₂ absorption on the annual scale, in which monthly NEE, GPP, and Re in two consecutive years varied from -165.16 to 93 g CO₂ m^-2 mo^-1, 6.66 to 384.45 g CO₂ m^-2 mo^-1, and 6.9 to 232.02 g CO₂ m^-2 mo^-1, respectively. The monthly ET from June to September was smaller than precipitation; these results reversed in the remaining months. Annual ET was 362.1 mm in 2015 and 324.96 mm in 2016. The net radiation (R_n), sensible heat (H), latent heat (LE), and ground heat (G) fluxes showed similar monthly patterns. Values of monthly average half-hour R_n, H, LE, and G at the daytime showed R_n > LE > H > G, and the time of the monthly half-hour G peak obviously lagged the R_n, H, and LE. Monthly average Bowen ratios were <1 from May to October, but it reversed in the rest of the months.

Incorporation of salvaged peat in soil cover designs for oil sands mine reclamation is a common practice. However, current peat salvage practices do not differentiate between peatland types or the botanical composition of peat. In this study, we characterized the botanical composition of natural peat and coversoil on reclaimed sites and examined the influence of botanical composition on the physicochemical characteristics of reclaimed coversoil. Peat samples were collected from 15 natural peatlands (bog, poor fen, and rich fen) and peat coversoils were sampled from six reclaimed sites in the Athabasca oils sands region. The botanical compositions (Sphagnum, wood Sphagnum, woody, and woody/moss herbaceous) of all samples were determined. We found that natural peatland types had different physicochemical properties, primarily driven by Sphagnum-dominated samples with a high carbon:nitrogen (C:N) ratio and low total exchange capacity (TEC) when compared with samples dominated by more woody/moss herbaceous material. Similarly, we found that coversoil with Sphagnum-dominated peat compared with woody/moss herbaceous peat had lower TEC, pH, and total nitrogen values and higher C:N ratios (∼40 vs. 20 for Sphagnum and woody/moss herbaceous, respectively). Our results indicate that physicochemical properties driven by botanical composition remain in coversoil 5 yr after placement.

Soil pollution is an extensive global problem, and effective management depends on accurate characterization and mapping of the extent of soil contamination. The objectives of this study were to determine the accuracy of different sampling intensities and the optimal number of samples required to minimize remediation project costs. To determine the accuracy associated with different sampling intensities, a Monte Carlo simulation was conducted. A simulated contaminant plume was created based on inverse distance weighting, kriging, or multivariate adaptive regression splines. Different sampling intensities, with grid spacing ranging from approximately 10% to 50% of the site extent, were used to generate a plume map using random forest model with a Euclidean distance matrix as predictors. The relative error was then determined as part of a Monte Carlo simulation that ran 10 000 simulations for each grid intensity for a total of 90 000 simulations. The optimal number of samples was determined based on economic factors, and the error functions generated with the Monte Carlo simulations. Average error ranged from 57% for 25 data points to 5% for 2800 data points. The 90th percentile error ranged from 100% to 0.3% for the sample data point range. Based on these results, the optimal number of samples, depending on pricing, ranged from 31 samples for a 10 m³ contaminant plume to 3475 samples for a 10 000 m³ soil contaminant plume.

Since 1963 approximately 100 000 oil and gas well pads have been officially certified as reclaimed in Alberta, yet follow-up monitoring programs have not been established to assure provincial environmental desired outcomes such as equivalent land capability are met at these certified well pads. The Ecological Recovery Monitoring Project was designed to determine long-term recovery of environmental quality at certified, reclaimed oil and gas well pads. Our study used soil data from 25 oil and gas well pads that were certified as reclaimed between 1964 and 2011. The objective of this study was to determine if well pad reclamation had long-term legacy effects on soil parameters and land capability as measured with the land suitability rating system (LSRS). We used multivariate covariance generalized linear models to determine effects of recovery time and reclamation on well pad soil parameters pH, bulk density (Db), total organic carbon (TOC), and electrical conductivity relative to reference soils. We also determined effects of reclamation on capability ratings using the LSRS. We concluded that soil quality and LSRS indices on well pads were lower than references due to adverse effects on pH, Db, and TOC. Long-term legacy effects on cultivated soils are significant and not well aligned with intended provincial outcomes. Further monitoring of reclaimed sites is strongly recommended.

Soil moisture is a key element of the hydrological cycle, and it significantly impacts the surface water and energy fluxes. However, a knowledge gap exists on the spatial variability of root-zone soil moisture at the regional scale in arid and hyperarid regions. Thus, soil moisture measurements at 142 sites were taken in Xinjiang (northwest China), and the relationships between soil moisture and 19 environmental factors were analyzed. The results showed that both absolute gravitational soil water content (SWC) and relative extractable water (REW) increased with increasing soil depth in the 0–100 cm soil profile. It generally decreased in the order of cropland > forestland > grassland > shrubland > bare land. Semivariograms suggested that SWC had moderate spatial dependence over a large range of 473–558 km, and REW was more randomly distributed at the regional scale in Xinjiang. Redundancy analysis suggested that environmental factors could explain 47.5%–50.9% of the variability of soil moisture, which was more strongly driven by land surface factors (p < 0.01) than by climatic factors (p > 0.05). Soil properties and other local variables explained, respectively, 40.7% and 32.3% of the variability of soil moisture in the 0–100 cm soil profile. Soil properties independently accounted for 12.8% and 28.1% of the variability in soil moisture in the 0–50 and 50–100 cm soil layers, respectively. Soil texture, field capacity, wilting point, organic carbon, bulk density, land use, and normalized difference vegetation index were the dominant factors influencing soil moisture variations.

Soil phosphorus (P) availability may be impacted by management practices, thereby affecting plant P uptake and plant response to P amendments. The aim of this study was to determine the effects of long-term management on soil P pools and to assess the response of P bioavailability, plant growth, and P uptake to mineral versus manure P treatments. Soils were collected from plots under organic (ORG), organic with composted manure (ORG + M), conventional (CONV), and restored prairie (PRA) management. Italian ryegrass (Lolium multiflorum L.) seedlings were grown in the greenhouse for 106 d in soils amended with various rates of manure or mineral P. The ORG soil had lower concentrations of labile P (resin-P and NaHCO₃-P) compared with the CONV and PRA soils, as determined by sequential P fractionation prior to planting. Ryegrass biomass (root + shoot) and shoot P uptake from soils receiving no P were significantly lower for the ORG than all other management systems. Although apparent P use efficiency of the whole plant was increased by low P rate in the ORG management system, the source of applied P, manure > mineral, only influenced Olsen test P.

Soil erosion is a major environmental threat to the sustainability and productive capacity of soils. This study aimed to identify optimal land use types for Zayandehrood watershed in central Iran for the first time which is large and mountainous to minimize runoff production and soil loss. Two different types of land use data for two scenarios were developed using soil and water assessment tool (SWAT) in combination with Sequential Uncertainty Fitting Program (SUFI-2) at the subbasin level with uncertainty analysis to explicitly quantify hydrological components on a daily time step. In the first scenario, the current land use map of the study area was used, and the second scenario was constructed using an optimal land use map obtained from a land evaluation study. Promotion of the land uses in the second scenario resulted in a noticeable reduction in discharge and sediment productions in the watershed. The simulated mean discharge values by the scenarios 1 and 2 were approximately 14 658 and 13 290 m³ yr^-1, respectively. The mean annual sediment yield simulated by the scenario 1 (approximately 122 220 t yr^-1) decreased to that of the scenario 2 (94 440 t yr^-1). This study provides a strong basis for reducing runoff and sediment yields in central Iran; however, its general analytical framework could be applied to other parts of the world that are facing similar challenges.

An error-free and fast approach for the identification of the area dynamics of soil erosion intensity (SEI) is essential for local governments. In this study, a simple method combination of the vegetation cover, gradient slope, and land use coupling index (vegetation and slope coupling index) model with field sampling unit schemes was explored to estimate the area variations of SEI between the years 1998 and 2009. The obtained results show that the minimum average prediction accuracy (PA) for sampling units was 94% among different land use types, whereas the maximum PA was 98.5%. Although PAs for different land use types showed discrepancies, the trend clearly depicted higher rates of sampling units and lower relative errors. The average fitting accuracies (FAs) of the sampling units were 98.84%, 97.92%, and 97.26%, respectively, based on different proposed strategies, whereas the FAs of the extrapolation results were 94.77%, 87.57%, and 92.41%, respectively. In addition, the extrapolation results were found to be less efficient than the sampling units. However, this is acceptable, considering the field observation workloads and time consumption. Therefore, this study provides a promising scheme for the rapid estimation of the area dynamics of SEI, which will be useful for estimating the SEI in other areas.

Crop residues and N fertilizer under no-till may increase soil water repellency (SWR) and soil hydrophobicity, but few studies have examined these two treatment factors and their interaction. A laboratory study was conducted using a long-term (since 1999) field experiment on a clay loam soil to determine the effect of three crop residues and two N fertilizer levels on SWR and soil hydrophobicity under no-till within the Dark Brown soil zone of the semi-arid Canadian prairies. The three residue treatments were residues removed from soil (Rx0), residues returned to soil (Rx1), and residues supplemented to soil (Rx2). The two fertilizer N treatments were 0 (N0) and 45 kg N ha^-1 (N1). Surface (0–10 cm) soil samples were taken in the spring of 2017 after 17 yr. Laboratory measurements were conducted on air-dried and sieved (<2 mm) soil to determine SWR using the repellency index method (RI), soil organic C, hydrophobic CH and hydrophilic CO functional groups, and soil hydrophobicity (CH/CO ratio). Mean RI values ranged from 2.19 to 2.75, indicating subcritical (RI > 1.95) SWR. Similar (P > 0.05) RI values were found for the three residue and two N fertilizer treatments, but the trend was for greater RI with increased residue addition (by 12%–26%) and N fertilizer (by 8%). Soil hydrophobicity was significantly greater by 47%–82% for straw returned or supplemented than straw removed treatments, and by 33% for fertilized than unfertilized treatments. Overall, greater residues and N fertilizer had no effect on SWR, but significantly increased soil hydrophobicity.

Fertilizer NO₃-N may represent a benefit over NH₄-N containing sources in semiarid regions where rainfall is often not sufficient to leach fertilizer-N out of crop rooting zones, denitrification concerns are not great, and when NH₃ volatilization concerns exist. The objective of our study was to contrast plant-N derived from fertilizer-¹⁵N (¹⁵Ndff), fertilizer-¹⁵N recovery (F¹⁵NR), total N uptake, grain yield, and protein of wheat (Triticum aestivum L.) from spring-applied NaNO₃ relative to urea and urea augmented with urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT). We established six fertilizer-N field trials widespread within the state of Montana between 2012 and 2017. The trials incorporated different experimental designs and ¹⁵N-labeled fertilizer-N sources, including NaNO₃, NH₄NO₃, urea, and urea + NBPT. Overall, F¹⁵NR and ¹⁵Ndff in mature crop biomass were significantly greater for NaNO₃ than urea or urea + NBPT (P < 0.05). Crop ¹⁵Ndff averaged 53.8%, 43.9%, and 44.7% across locations for NaNO₃, urea, and urea + NBPT, respectively. Likewise, crop F¹⁵NR averaged 52.2%, 35.8%, and 38.6% for NaNO₃, urea, and urea + NBPT, respectively. Soil ¹⁵N recovered in the surface layer (0–15 cm) was lower for NaNO₃ compared with urea and urea + NBPT. Wheat grain yield and protein were generally not sensitive to improvements in ¹⁵Ndff, F¹⁵NR, or total N uptake. Our study hypothesis that NaNO₃ would result in similar or better performance than urea or urea + NBPT was confirmed. Use of NO₃-N fertilizer might be an alternative strategy to mitigate fertilizer-N induced soil acidity in semiarid regions of the northern Great Plains.