European Journal of Soil Biology最新文献

Precipitation changes altered soil heterotrophic respiration, but the underlying microbial mechanisms remain rarely studied. This study conducted three-year switchgrass (Panicum virgatum L.) mesocosm experiment to investigate soil heterotrophic respiratory responses to altered precipitation. Five treatments were considered, including ambient precipitation (P0), two wet treatments (P+33 and P+50: 33% and 50% enhancement relative to P0), and two drought treatments (P-33 and P-50: 33% and 50% reduction relative to P0). The plant's aboveground biomass (AGB), soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC), heterotrophic respiration (R_s), biomass-specific respiration (R_ss: respiration per unit of microbial biomass as a reciprocal index of microbial growth efficiency), and extracellular enzymes activities (EEAs) were quantified in soil samples (0–15 cm). Despite significantly different soil moisture contents among treatments, results showed no impact of precipitation treatments on SOC and TN. Increasing precipitation had no effect, but decreasing precipitation significantly reduced plant AGB. Relative to P0, P+33 significantly increased R_s by more than 3-fold and caused no changes in MBC, leading to significantly higher R_ss (P < 0.05). P+33 also significantly increased hydrolytic enzyme activities associated with labile carbon acquisition (C_acq) by 115%. The only significant effect of drought treatments was the decreased β-d-cellobiosidase (CBH) and peroxidase (PEO) under P-33. Nonparametric analyses corroborated the strong influences of moisture and CBH on the enhanced precipitation, which stimulated soil respiratory carbon loss, likely driven by both elevated hydrolase activities and reduced microbial growth efficiency. However, the less sensitive drought effects suggested potential microbial tolerance to water deficiency despite depressed plant growth. This study informs the likely decoupled impacts of microbes and plants on soil heterotrophic respiration under changing precipitation in the switchgrass mesocosm experiment.

The metabolic activity of soil microorganisms is often limited by soil nutrient availability. Fertilization can increase available nutrient content, but nutrient limitations may persist because of imbalances in nutrient inputs. However, the mechanisms driving the response of soil microbial nutrient limitation to N and P application in grasslands remain unclear. To address this issue, we applied fifteen fertilization treatments composed of five N levels (0, 1.55, 4.65, 13.95, 27.9 g N m⁻² y^r−1) and three P levels (0, 5.24, 10.48 g P m⁻² yr⁻¹) to a meadow steppe in Inner Mongolia across three years using a split-plot experiment design. Soil microbial biomass and extracellular enzyme activities were analyzed in samples collected from each plot in May, July, and August. The addition of N significantly reduced microbial biomass carbon (MBC) in samples collected in May and increased microbial biomass nitrogen (MBN) in July samples, thus decreasing the ratio of MBC:MBN in both months. P addition significantly increased microbial biomass phosphorus (MBP), whereas it reduced the ratio of MBC:MBP and MBN:MBP. Using vector analysis, we found that vector angle was less than 45° across all sampling dates, indicating that soil microbial metabolism was predominately limited by N rather than P. The severity of microbial N limitation was attenuated by N addition, but was worsened by P addition in May and July. The severity of microbial C limitation was significantly intensified by N addition in May and July, and forced by P addition in July and August. Visual partitioning analysis showed that soil physicochemical and microbial properties explained 37% and 70% of variation in microbial C and N limitation, respectively. Besides soil available nutrient concentrations, soil water content (SWC) and pH were identified as the key factors driving microbial C and N limitations. The relative influence of SWC on microbial N limitation was highest across all sampling dates. According to PLS-SM modeling, SWC had a total effect of −0.349 on microbial N limitation, which was significantly higher than the effects than N addition (−0.192) and P addition (0.131). Overall, this study indicates that soil moisture was the primary control over the response of microbial nutrient limitation to N and P additions in a meadow steppe in Inner Mongolia.

It is well known that the mosaic patches of alpine meadows are primarily shaped by plant-soil interactions. However, we know little about whether and how plant functional traits mediate the influence of edaphic factors on soil microbial diversity through the mass and diversity effects. In this study, we investigated plant functional traits in five distinctive of mosaic patches (communities) dominated by different plant functional groups in a Tibetan alpine meadow. We measured key functional traits for every plant species within each plot to calculate the functional composition (i.e., community-weighted mean, CWM) and structure (i.e., functional diversity, FD) of the plant community to examine the mass and diversity effects of plants on soil microbial diversity. In general, the difference in soil microbial diversity across the mosaic communities can be predicted by changes in CWM and FD of plant communities incorporating edaphic factors. The change in FD of five plant traits alone can predict 46% variation for soil bacterial richness, and up to 91% variation for soil fungal richness when the direct effect of edaphic factors was included. In response to variations in soil available phosphorus and pH, an increase in plant CWM and FD of leaf phosphorus and nitrogen content significantly promoted the richness of soil bacteria but lowered soil fungal richness. Hence, plant functional traits play a critical role in mediating the effects of edaphic factors on soil microbial diversity through mass and diversity effects. Our study not only illustrates the functional significance of plant traits in shaping plant-soil interactions in mosaic communities of the Tibetan alpine meadow but also promotes research linking biodiversity in mosaic patches to the functionality of the fragile alpine ecosystem.

Ants are undisputed masters at transforming the local environments they inhabit, with subsequent vast effects on soil chemical and hydrological processes. Yet, it remains unclear how deep into the subsoil these effects range, as most ant-soil studies focus on the topsoil. Furthermore, studies quantifying these effects on podzolized, and nutrient-poor heathland soils remain scarce. We excavated 15 Formica exsecta ant mounds on a long-term, unmanaged heathland in Denmark. We sampled soil moisture, soil penetration resistance (SPR), pH, total phosphorous content, and the thickness of each soil horizon at three positions at each mound: directly below the mound, at the edge of the mound, and an adjacent undisturbed reference soil. Results revealed that ant activity reduced soil moisture, loosened the soil, and increased the flow of total phosphorus to the deeper layers. Importantly, the cemented spodic horizons (hardpans) with waterlogging properties were penetrated by ant digging, resulting in potentially higher water infiltration into the subsoil. The ant activity within the otherwise undisturbed sandy subsoil below the hard pan caused a slight alteration in the thickness of each soil horizon and chemistry. These patchy, small-scale disturbances (mounds covered 0.06 % of the site) increase heathland soil heterogeneity and affect subsoil properties in time. We conclude that ant mounds may play a previously overlooked role in heathland soil dynamics by penetrating the heathland hardpans and manipulating soil chemistry and soil moisture. We argue that a viable mound-forming ant community is valuable for the soil heterogeneity of dry heathland ecosystems.

Earthworms can act as ecosystem engineers by altering soil structure, which impacts other organisms and ecosystem functioning. Jumping worms (family Megascolecidae) originating in Asia have been spreading in North America, extending their northern range limits to Ontario, Canada in the last decade and to New Brunswick in 2021. At the northern limits of their current range, little research has been done to examine the effects of jumping worms in these new habitats since their recent establishment. Our objectives were to evaluate: (1) how jumping worms impact soil nitrogen and soil carbon; (2) how their presence impacts the abundance of non-native European earthworms (family Lumbricidae); and (3) whether two sampling methods (i.e., mustard solution and wooden discs) are equally effective at detecting jumping worms. We sampled a residential property in Oromocto, New Brunswick, which was the first location where jumping worms were found in the province. Jumping worms did not have significant impacts on the abundance and biomass of European earthworms or soil carbon content in the top 5 cm of the soil, but they did significantly affect soil nitrogen levels. Both sampling methods were equally effective at detecting the presence of jumping worms. Further research is needed in managed landscapes, urban areas, and forests to determine the ecosystem impacts and invasion dynamics of jumping worms in Canada as this invasion progresses.

Large-scale replacements of native birch with spruce have been carried out in Western Norway for economic reasons. This tree species shift potentially affects biotic components such as the eucaryome, consisting of microscopic animals (Metazoa), protists and fungi, which are key players in the functioning of forest ecosystem. The impact on the belowground eukaryome and its interactions with vegetation and soil properties is not well assessed. We examined the impact of replacing native birch with Norway spruce plantations on the eukaryome of the boreal forest floor in Western Norway using 18S rDNA metabarcoding. The tree species shift from birch to spruce had significant impacts on the eukaryome at both taxonomic (Metazoa) and functional categories (phagotrophs, phototrophs, parasites and osmotrophs). The distinct differences in eukaryome communities were related to changes in understorey vegetation biomass and soil chemistry following the tree species shift. This had a negative effect on eukaryome richness, particularly affecting phagotrophs and parasites, while the opposite was observed for osmotroph richness. Our results indicated that the spruce plantations altered the eukaryome communities and their food-web patterns compared to what was found in the native birch forest soil. This information should be taken into consideration in forest management planning.

In temperate grassland, earthworms contribute to the major soil processes which determine most of the ecosystem services. The characteristics of plant communities in grassland are key factors in maintaining earthworm communities, however effects of different herbage management on earthworms remain largely unknown. In this context, the aim of the present study was to determine the long-term effects of herbage management on grassland plant and earthworm communities. Plants and earthworms were sampled in a 14-years-old experiment in upland grasslands (Massif central, France). Abandoned grasslands were compared with mowed grasslands and with pastures grazed by cattle (at low or high intensities) or grazed by sheep (at low intensity). Compared to abandoned grassland, herbage management by grazing or by mowing display higher leguminous plant, community-weighted mean Ellenberg light values as well as plant richness while they display lower percentage of plant litter and community-weighted mean Ellenberg nitrogen values. The differences in plant richness were associated with a significant change in plant community structure. Compared to the abandoned grassland, herbage management by grazing or mowing significantly display higher earthworm biomass and total richness. Except for pastures grazed by cattle at high intensity, earthworm abundance was at least twice that in the grassland at low grazing intensity or mowing compared to the abandoned grassland. Earthworm communities were significantly different between grazed and mown treatments notably due to changes within Aporrectodea anecic and endogeic earthworm species. Overall, herbage management by animals or by mechanical export is beneficial for plant and earthworm diversity although no clear differences between management practices for earthworm richness, total biomass or total abundance were observed. Our results highlight that abandonment does not preserve biodiversity (plant, soil macrofauna) while management of grassland by grazing or mowing is a necessary tool for biodiversity conservation and improvement.

Nitrite-driven anaerobic oxidation of methane (nitrite-driven AOM), mediated by ‘Candidatus Methylomirabilis oxyfera’ (M. oxyfera)-related bacteria, is a newly-discovered CH₄ consumption process in coastal wetlands. Although Spartina alterniflora invasion significantly affects CH₄ emissions from coastal wetlands, its impact on the nitrite-driven AOM process and the underlying mechanisms remain unknown. Here, we examined nitrite-driven AOM activity and M. oxyfera-related bacterial community in four coastal wetlands along the southeastern coast of China, under invasive Spartina alterniflora and native plants, including Kandelia candel, Avicennia marina or Phragmites australis. Linear mixed-effects models indicated that the Spartina alterniflora invasion stimulated the overall nitrite-driven AOM activity by an average of 61.5% in coastal wetlands (p < 0.05), but had no impact on the M. oxyfera-related bacterial abundance (p > 0.05). The nitrite-driven AOM activity was 7.1 times higher under Spartina alterniflora than under native species in Yueqing Bay (p < 0.05), and was 34.7%, 8.9% and 15.1% higher under Spartina alterniflora than under native species in Hengsha Island, Jiulong River and Zhanjiang, respectively (p > 0.05). Spartina alterniflora invasion increased the bacterial abundance in Yueqing Bay and Jiulong River Estuary by 6.8 and 7.6 times, respectively, while decreased the abundance by 34.4% and 51.4%, respectively, in Hengsha Island and Zhanjiang (p > 0.05). The partial least squares path model indicated an indirect impact of Spartina alterniflora invasion on the nitrite-driven AOM activity through its effect on soil properties, primarily including dissolved organic carbon content and nitrate content. The Spartina alterniflora invasion did not greatly alter M. oxyfera-related bacterial community. Overall, we shed new light on the potential impact of Spartina alterniflora invasion on CH₄ cycling in coastal wetlands.