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UNLABELLED: Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13157-023-01722-2.

The re-vegetation of mining wastes with native plants is a comparatively low-cost solution for mine reclamation. However, re-vegetation fails when extreme pH values, low organic matter, or high concentrations of phytotoxic elements inhibit plant establishment and growth. Our aim was to determine whether the combined addition of municipal waste compost and diazotrophic endophytes (i.e., microorganisms that fix atmospheric N2 and live within plants) could improve plant growth, organic matter accumulation, and phytostabilization of trace element contaminants in two types of hard rock mine waste. We grew a widespread native perennial grass, Bouteloua curtipendula, for one month in alkaline waste rock (porphyry copper mine) and tailings (Ag-Pb-Au mine, amended with dolomite) sourced from southeastern Arizona, United States. B. curtipendula tolerated elevated concentrations of multiple phytotoxic trace elements in the tailings (Mn, Pb, Zn), stabilizing them in roots without foliar translocation. Adding compost and endophyte seed coats improved plant growth, microbial biomass, and organic matter accumulation despite stark differences in the geochemical and physical characteristics of the mining wastes. The widespread grass B. curtipendula is a potential candidate for re-vegetating mine wastes when seeded with soil additives to increase pH and with microbial and organic amendments to increase plant growth. This study quantifies improvements to plant growth, soil fertility, and trace element stabilization with a municipal waste compost topdressing and diazotrophic endophyte seed coating in two common hard rock mining wastes of the western United States. It establishes that a widespread perennial grass, Bouteloua curtipendula, can grow despite high concentrations of phytotoxic trace elements and minimal soil nutrients, and stabilizes trace elements on or in its roots, making it a suitable option for re-vegetation or phytostabilization of hard rock mining wastes. [ABSTRACT FROM AUTHOR]

Soil coarseness decreases ecosystem productivity, ecosystem carbon (C) and nitrogen (N) stocks, and soil nutrient contents in sandy grasslands subjected to desertification. To gain insight into changes in soil C and N pools, microbial biomass, and enzyme activities in response to soil coarseness, a field experiment was conducted by mixing native soil with river sand in different mass proportions: 0, 10, 30, 50, and 70% sand addition. Four years after establishing plots and 2 years after transplanting, soil organic C and total N concentrations decreased with increased soil coarseness down to 32.2 and 53.7% of concentrations in control plots, respectively. Soil microbial biomass C (MBC) and N (MBN) declined with soil coarseness down to 44.1 and 51.9%, respectively, while microbial biomass phosphorus (MBP) increased by as much as 73.9%. Soil coarseness significantly decreased the enzyme activities of β-glucosidase, N-acetyl-glucosaminidase, and acid phosphomonoesterase by 20.2-57.5%, 24.5-53.0%, and 22.2-88.7%, used for C, N and P cycling, respectively. However, observed values of soil organic C, dissolved organic C, total dissolved N, available P, MBC, MBN, and MBP were often significantly higher than would be predicted from dilution effects caused by the sand addition. Soil coarseness enhanced microbial C and N limitation relative to P, as indicated by the ratios of β-glucosidase and N-acetyl-glucosaminidase to acid phosphomonoesterase (and MBC :MBP and MBN:MBP ratios). Enhanced microbial recycling of P might alleviate plant P limitation in nutrient-poor grassland ecosystems that are affected by soil coarseness. Soil coarseness is a critical parameter affecting soil C and N storage and increases in soil coarseness can enhance microbial C and N limitation relative to P, potentially posing a threat to plant productivity in sandy grasslands suffering from desertification. [ABSTRACT FROM AUTHOR]

Soil coarseness decreases ecosystem productivity, ecosystem carbon and nitrogen stocks, and soil nutrient contents in sandy grasslands. To gain insight into changes in soil carbon and nitrogen pools, microbial biomass, and enzyme activities in response to soil coarseness, a field experiment of sand addition was conducted to coarsen soil with different intensities: 0 % sand addition, 10 %, 30 %, 50 %, and 70 %. Soil organic carbon and total nitrogen decreased with the intensification of soil coarseness across three depths (0-10 cm, 10-20 cm, and 20-40 cm) by up to 43.9 % and 53.7 %, respectively. At 0-10 cm, soil microbial biomass carbon (MBC) and nitrogen (MBN) declined with soil coarseness by up to 44.1 % and 51.9 %, respectively, while microbial biomass phosphorus (MBP) increased by as much as 73.9 %. Soil coarseness significantly decreased the activities of β-glucosidase, N-acetyl-glucosaminidase, and acid phosphomonoesterase by 20.2 %-57.5 %, 24.5 %-53.0 %, and 22.2 %-88.7 %, respectively. Soil coarseness enhanced microbial C and N limitation relative to P, indicated by the ratios of β-glucosidase and N-acetyl-glucosaminidase to acid phosphomonoesterase (and MBC:MBP and MBN:MBP ratios). As compared to laboratory measurement, values of soil parameters from theoretical sand dilution was significantly lower for soil organic carbon, total nitrogen, dissolved organic carbon, total dissolved nitrogen, available phosphorus, MBC, MBN, and MBP. Phosphorus immobilization in microbial biomass might aggravate plant P limitation in nutrient-poor grassland ecosystems as affected by soil coarseness. We conclude that microbial C:N:P and enzyme activities might be good indicators for nutrient limitation of microorganisms and plants. [ABSTRACT FROM AUTHOR]

Anthropogenic-driven changes in N and water availability are two of the most important factors determining soil C and N turnover in temperate grassland ecosystems. To gain insight into changes in soil aggregation and C and N dynamics in response to N and water addition, we collected soil samples from a field study conducted for 9 yr in a semiarid steppe grassland in Inner Mongolia, China. Three aggregate size classes (microaggregates, <250 mm; small macroaggregates, 250–2000 mm; macroaggregates, >2000 mm) were isolated and analyzed for their mass proportions, soil organic C (SOC), total N (TN), total extractable inorganic N (TIN), and stable isotope ratio of 13C relative to 12C (d13C) and stable isotope ratio of 15N relative to 14N (d15N) values. Water addition on average increased large macroaggregates by 33% and decreased microaggregates by 42%. Nitrogen and water addition interacted significantly and increased TIN concentration but had no impact on SOC or TN. Soil organic C was negatively correlated with d13C values of large and small macroaggregates under ambient precipitation and within all soil aggregates under water addition. Significant positive correlations between TIN and d15N values were detected for large macroaggregates and microaggregates under ambient precipitation. Our results suggest that water addition accelerated plant residue incorporation into soil organic matter (SOM) (indicated by depleted 13C values) while N addition potentially increased gaseous N losses (suggested by 15N enrichment without changing soil C and N concentrations). Water, but not N, improved soil structure in this semiarid grassland. Our study provides new insights for using natural abundance 13C and 15N to better understand the sensitivity of SOM within different soil particles to coupled N–water changes under global change scenarios. [ABSTRACT FROM AUTHOR]