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Processes driving nutrient retention in stormwater green infrastructure (SGI) are not well quantified in water-limited biomes. We examined the role of plant diversity and physiochemistry as drivers of microbial community physiology and soil N dynamics post precipitation pulses in a semi-arid region experiencing drought. We conducted our study in bioswales receiving experimental water additions and a montane meadow intercepting natural rainfall. Pulses of water generally elevated soil moisture and pH, stimulated ecoenzyme activity (EEA), and increased the concentration of organic matter, proteins, and N pools in both bioswale and meadow soils. Microbial community growth was static, and N assimilation into biomass was limited across pulse events. Unvegetated plots had greater soil moisture than vegetated plots at the bioswale site, yet we detected no clear effect of plant diversity on microbial C:N ratios, EEAs, organic matter content, and N pools. Differences in soil N concentrations in bioswales and the meadow were most directly correlated to changes in organic matter content mediated by ecoenzyme expression and the balance of C, N, and P resources available to microbial communities. Our results add to growing evidence that SGI ecological function is largely comparable to neighboring natural vegetated systems, particularly when soil media and water availability are similar. [ABSTRACT FROM AUTHOR]

Purpose: Microbial carbon use efficiency (CUE) greatly controls the magnitude of soil organic carbon turnover. This study was conducted to estimate the CUE with the additions of different organic matter (OM) to the top soil of a Pinus tabulaeformis forest and explore the variations of CUE and ecoenzyme activity with the quality of the added OM. Materials and methods: Five types of OM, i.e., P. tabulaeformis leaves, Quercus wutaishanica leaves, maize straw, biochar, and wood, were separately crushed by a machine and then manually mixed in the top 20 cm of soil in a plot at 5 × 5 m in June 2014. Concurrently, 20 g of each OM larger than 1 cm was put in a nylon bag of 10 × 15 cm and placed above the plot ground to monitor the OM decomposition. The soil samples were taken and analyzed for the physicochemical properties, the extracellular enzyme activity, and soil microbial biomass, and the OM decomposition rate was also measured in August 2017. Results and discussion: The OM in the litter bag absorbed nitrogen from the soil particle during the decomposition period, and the nitrogen release rates of wood debris and maize straw were significantly lower at − 625.01% and − 276.98%. The carbon targeting enzyme, i.e., α-1,4-glucosidase (AG), was also influenced by the OM addition and changed from 5.39 nmol h−1 g−1 with the Q. wutaishanica leaf addition to 14.82 nmol h−1 g−1 with the wood debris addition. Significant differences were simultaneously detected in the soil microbial biomass carbon content among different OM additions. These changes in soil biophysical properties contributed to much of the variation in CUEC:N. The CUEC:N meaning the microbial carbon assimilation at the cost of nitrogen was highest at 0.221 for wood debris addition. Conclusions: The addition of OM differing in quality could influence the soil resource content, exo-enzyme activity, and soil microbial biomass through its nutrient release rate. The CUEC:N could act as an integrative proxy of soil biophysical properties because it also correlated with the soil nutrient content, ecoenzymatic stoichiometry and the OM nutrient release rate. The high CUEC:N value indicated a big carbon stabilization in soils with wood debris addition. [ABSTRACT FROM AUTHOR]

The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts). We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg ha-1 yr-1 from March 2012 to March 2013. In March 2013, biocrust (0-0.5 cm) and bulk soils (0-10 cm) were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities (EEA) and rates of N transformation. By most measures, nutrient availability, microbial biomass and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N.

The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH, and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts). We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg N ha-1 y-1 from March 2012 to March 2013. In March 2013, biocrust (0-0.5 cm) and bulk soils (0-10 cm) were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities and rates of N transformation. By most measures, nutrient availability, microbial biomass, and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N amendment that included data from 14 other studies. Effect sizes were calculated for biomass and metabolic responses. Regressions of effect sizes, calculated for biomass, and metabolic responses, showed similar trends in relation to N application rate and N load (rate × duration). The critical points separating positive from negative treatment effects were 88 kg ha-1 y-1 and 159 kg ha-1, respectively, for biomass, and 70 kg ha-1 y-1 and 114 kg ha-1, respectively, for metabolism. These critical values are comparable to those for microbial biomass, decomposition rates and respiration reported in broader meta-analyses of N amendment effects in mesic ecosystems. However, large effect sizes at low N addition rates indicate that arid ecosystems are sensitive to modest increments in anthropogenic N deposition. [ABSTRACT FROM AUTHOR]

• Microbial resource limitation varied in different season and peatland type of Zoige. • Abiotic factors affected soil organic carbon more than biotic factors in Zoige soils. • Total nitrogen might be the most critical factor affecting soil organic carbon. • Soil properties directly and indirectly affected soil carbon by affecting microbes. A large quantity of carbon (C) storage in peatland soils plays an important role in global C cycling. Microbial resource limitation and environmental factors can drive C cycling. However, the microbial resource limitation and regulator of C cycling in such an ecosystem are debated and still unclear. Therefore, this study chose Zoige, the largest peatland in the Qinghai-Tibet Plateau of China, to identify microbial resource limitation by analyzing ecoenzymatic stoichiometry and the regulation of soil organic C (SOC) through the interrelationships correlating SOC to abiotic (soil properties) and biotic factors (ecoenzyme activities, microbial communities, and abundance). The results demonstrated that soil microbial resource limitation varied in different seasons, across peatland types, and with depths; SOC content was more affected by abiotic factors (total nitrogen, total phosphorus, Olsen-phosphorus, moisture content) than biotic factors at the regional scale, and the factors driving C cycling differed among peatland types at the subregional scale. The path analysis further emphasized the importance of abiotic factors in C cycling, especially total nitrogen. This study provides important information for the understanding regulator of C cycling in peatland soils, which may help mitigate global climate change. [ABSTRACT FROM AUTHOR]