Ecosystems最新文献

Drainage is known to reduce carbon sequestration in peatlands, but its effect on the stability of carbon pool and changes in recalcitrant organic carbon fractions remain relatively unknown, especially in temperate montane peatlands. We investigated the effect of drainage on physicochemical properties and organic carbon fractions of six peat cores from drained and near-pristine areas of Baijianghe peatland, NE China, basing on ²¹⁰Pb and AMS ¹⁴C dating. The vegetation biomass and biomass-C sequestration were also measured in both areas. The loss of total soil carbon accumulation due to drainage was 7.5 kg m⁻² (− 25%), equivalent to a complete consumption of carbon accumulated for nearly 170 years in the near-pristine area. Vegetation succession after drainage had a little positive effect on ecosystem carbon sequestration, with an increase of 0.26 kg m⁻², which compensated for only 3.5% of the peat soil carbon loss. Notably, over 80% of the total carbon loss after drainage was attributed to the loss of the recalcitrant carbon fraction. The study emphasizes the crucial impact of drainage on carbon sequestration in temperate peatlands. Our findings suggest that continuous water table drawdown induced by drainage, together with drought driven by climate warming, will further reduce carbon sequestration in drained peatlands. There is an urgent need to restore hydrology of peatlands in order to mitigate the long-lasting negative effect of drainage.

While climate change significantly influences nitrogen cycling and its related microbial diversity, the effects of warming on nitrate reduction processes and their related microbial communities and functional gene abundances in mangrove sediments are not fully understood. In this study, mangrove sediment slurry was incubated under six controlled temperatures for 28 days to simulate warming trends. Following the incubation, rates of denitrification (DNF), anaerobic ammonium oxidation (ANA), and nitrate decomposition reduction to ammonium (DNRA), and net nitrous oxide (N₂O) production, functional gene abundances, and the structure of functional microbial taxa were investigated using a ¹⁵N tracer method, high-throughput sequencing, and qPCR methods. DNF’s optimal temperature was 25 °C, but ANA’s ranged from 25 to 35 °C. The DNRA rates; nosZ, nirS, and nrfA gene abundances; nosZ/(nirK + nirS) ratios; and, in particular, net N₂O production in the mangrove sediment significantly increased with increasing temperature. Furthermore, DNRA’s contributions to nitrate reduction increased from 26.70% at 10 °C to 44.42% at 40 °C, suggesting that the DNRA process transforms more nitrate to ammonia and retains more nitrogen within mangrove sediments than the other processes do. Meanwhile, microbial taxa changed significantly in relation to DNRA, indicating that DNRA is enhanced as temperature increases. Also, temperature explained most of the variance in the dominant bacterial communities (68.3%), nitrate reduction functional genes (91.8%), and process rates (79.9%). Thus, warming promotes nitrogen conservation in mangrove sediments but stimulates N₂O emissions, which in turn exacerbates global warming.

Understanding the biotic mechanisms of community stability in variable environments has been a focal point of fundamental ecological research. A multitude of mechanisms, encompassing compensatory dynamics arising from negative species covariance, portfolio effect linked to species richness and evenness, and dominant species stability, have been found to collectively enhance community stability. However, it is not clear how their stabilizing effects change and contribute to the maintenance of community stability along environmental gradients. We performed a ten-year investigation in a large shallow lake with a eutrophic gradient across space. With the dataset, we quantified the role of the three stability mechanisms, and their changes in effect size along the eutrophic gradient to determine their relative importance in biomass stability. Our results showed that the biomass stability shifted from one stable state at eutrophic sites to another stable state at hypertrophic sites, and biomass stability was positively correlated with composition stability. In the relatively stable state, biomass stability exhibited a closely synchronized variation along with compositional stability in response to environmental changes. Conversely, in the unstable state, biomass stability displayed weaker sensitivity to environmental changes compared to compositional stability. The effect sizes of different biotic mechanisms of biomass stability varied across the eutrophic gradient. Compensatory dynamics emerged as the primary force governing biomass stability in eutrophic waters, overshadowing the relatively weak impact of the portfolio effect, which might help resist the shift from turbid state to clear state with decreasing nutrient concentrations. However, as nutrient levels increased, the primary force shifted from compensatory dynamics toward the dominant species stability. This study improves our understanding for the biotic mechanisms of phytoplankton community responding to nutrients mitigation in eutrophic waters, which might be one of the most important ecological components for managing communities to maintain ecosystem functioning.

Relatively unmanaged interstitial areas at the residential–wildland interface can support the development of novel woody plant communities. Community assembly processes in urban areas involve interactions between spontaneous and cultivated species pools that include native, introduced (exotic/non-native) and invasive species. The potential of these communities to spread under changing climate conditions has implications for the future trajectories of forests within and beyond urban areas. We quantified woody vegetation (including trees and shrubs) in relatively unmanaged “interstitial” areas at the residential–wildland interface and in exurban reference natural areas in six metropolitan regions across the continental USA. In addition, we analyzed soil N and C cycling processes to ensure that there were no major anthropogenic differences between reference and interstitial sites such as compaction, profile disturbance or fertilization, and to explore effects of novel plant communities on soil processes. We observed marked differences in woody plant community composition between interstitial and reference sites in most metropolitan regions. These differences appeared to be driven by the expanded species pool in urban areas. There were no obvious anthropogenic effects on soils, enabling us to determine that compositional differences between interstitial and reference areas were associated with variation in soil N availability. Our observations of the formation of novel communities in interstitial spaces in six cities across a very broad range of climates, suggest that our results have relevance for how forests within and beyond urban areas are assessed and managed to provide ecosystem services and resilience that rely on native biodiversity.