Winter Climate Change Reshapes Soil Climate and Biogeochemistry in a Novel Snowmelt Experiment.

Soil moisture is the major factor influencing microbial community structure and enzyme activities across seven biogeoclimatic zones in western Canada

The winter climate is changing in many parts of the world, and it is predicted that winter climate change will modify the structure and function of plant–soil systems. An understanding of these changes and their consequences in terrestrial ecosystems requires knowledge of the linkage between above‐ and below‐ground components as well as the species interactions found in plant–soil systems, which have important implications for biogeochemical cycles. However, winter climate‐change studies have focused on only a part of the ecosystem or ecological process. We summarize here recent findings related to the effects of winter climate and its changes on soil nitrogen (N) dynamics, greenhouse gas (N 2 O) emissions from the soil, N use by individual plants, vegetation development, and interactions between vegetation and pollinators to generate an integrative understanding of the response of the plant–soil system to winter climate change. This review indicates that the net effects on plants, soil microbes, pollinators, and the associated biogeochemical cycles are balanced among several processes and are highly variable depending on the context, such as the target species/functional group, original winter condition of the habitat, and type of climate change. The consequences of winter climate change for species interactions among plants, associated animals, and biogeochemical cycles are largely unknown. For further research, a large‐scale comparative study to measure ecosystem‐level functions is important, especially in less‐cold ecosystems.

Mulching is a widely used agricultural management practice with profound effects on soil properties and crop productivity. However, its impact on soil microbial community structure and function remains insufficiently understood. This study aimed to investigate how different mulching treatments influence the composition, functional potential, and interaction networks of soil microbial communities in a chieh-qua-legume rotation system. Metagenomic sequencing was employed to analyze soil samples subjected to four mulching treatments (biodegradable mulch, non-degradable silver mulch, non-degradable black mulch, and straw mulch) as well as a no-mulch control (CK). Mulching treatments significantly altered soil microbial diversity and community structure, with straw and biodegradable mulches supporting higher diversity than the control. Biodegradable mulch was strongly correlated with changes in soil pH and enriched denitrifying bacteria such as Thauera and Comamonadaceae, while reducing the abundance of genes related to energy metabolism and carbon fixation. These findings suggest that organic carbon from mulch degradation may enhance denitrification, potentially leading to nitrogen loss. Co-occurrence network analysis revealed that biodegradable mulch promoted more complex and connected microbial networks, whereas plastic mulches resulted in simpler structures. Additionally, all mulching treatments significantly reduced the abundance of the autotrophic ammonia-oxidizing archaeon Thaumarchaeota, likely due to reduced soil oxygen under mulch. This study provides new insights into how different mulching practices modulate soil microbial communities and their ecological functions. The results underscore the importance of tailoring mulching strategies to maintain soil health and fertility. Specifically, nitrogen supplementation is recommended when using biodegradable mulch in chieh-qua cultivation systems.

One of the major factors associated with global change is the ever-increasing concentration of atmospheric CO(2). Although the stimulating effects of elevated CO(2) (eCO(2)) on plant growth and primary productivity have been established, its impacts on the diversity and function of soil microbial communities are poorly understood. In this study, phylogenetic microarrays (PhyloChip) were used to comprehensively survey the richness, composition and structure of soil microbial communities in a grassland experiment subjected to two CO(2) conditions (ambient, 368 p.p.m., versus elevated, 560 p.p.m.) for 10 years. The richness based on the detected number of operational taxonomic units (OTUs) significantly decreased under eCO(2). PhyloChip detected 2269 OTUs derived from 45 phyla (including two from Archaea), 55 classes, 99 orders, 164 families and 190 subfamilies. Also, the signal intensity of five phyla (Crenarchaeota, Chloroflexi, OP10, OP9/JS1, Verrucomicrobia) significantly decreased at eCO(2), and such significant effects of eCO(2) on microbial composition were also observed at the class or lower taxonomic levels for most abundant phyla, such as Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Acidobacteria, suggesting a shift in microbial community composition at eCO(2). Additionally, statistical analyses showed that the overall taxonomic structure of soil microbial communities was altered at eCO(2). Mantel tests indicated that such changes in species richness, composition and structure of soil microbial communities were closely correlated with soil and plant properties. This study provides insights into our understanding of shifts in the richness, composition and structure of soil microbial communities under eCO(2) and environmental factors shaping the microbial community structure.

The positive effect of earthworms on soil processes and plant growth has been extensively documented. The capacity of earthworms to decompose organic matter has been attributed to the microbial communities that inhabit their digestive track or the structures they build, which in turn contribute to make up the drilosphere, a hotspot for microbial activity. However, how earthworms modify the structure of soil microbial communities and how these changes affect soil microbial processes is still unclear. Do earthworms reduce microbial abundance and activity because they feed on microorganisms or do they select and stimulate specific microbial groups? We hypothesise that “the effect of earthworms on nutrient cycling and plant growth is not only a direct effect but is mainly mediated indirectly, via modifications of the microbial community.” The objective of this review is to synthesize the existing literature concerning the influence of earthworms on the structure and function of soil microbial communities, as well as to understand how earthworm-induced changes in the soil microbiota would in turn impact soil processes, particularly those occurring in the rhizosphere and involved in plant growth and health. Recent reports have shown that specific bacterial groups consistently increase in soils where earthworms are present, regardless of the earthworm functional group. The extent of this increase seems to be dependent upon the type of substrate under study. Our synthesis also reveals that endogeic and anecic earthworms regularly induce an increase in soil nutrients, whilst this positive effect is not as evident in the presence of epigeic earthworms. The effect of earthworms on nutrient cycling has been further investigated with microbial functional genes, although existing reports largely focus on nitrogen cycling. Earthworms seem to enhance denitrification, most likely through the increase in organic compounds due to organic matter decomposition. By enhancing soil nutrient availability, earthworms indirectly promote plant growth, which has also been attributed to the induction of signal molecules. However, no experiment to date has been able to prove a direct causal relationship between specific signal molecules, earthworms and plant growth promotion. Finally, we propose a framework for earthworm-microbiota interactions and recommend further research.

Core Ideas The effect of cover crops on soil microbes and biogeochemistry was examined. Cover crops increase microbial biomass and bioavailable soil carbon. Increasing cover crop biomass amplifies belowground effects. Agricultural soils are largely degraded or under threat of degradation. Given a growing human population and the subsequent need to feed this population, agricultural practices must maintain productivity and soil quality. Cover cropping regimes are a management approach that aims to address these dual goals. Although the use of cover crops has been linked to many positive effects on soil quality and crop yields, few studies have examined their effects on soil microbial community structure and function under active farm management. We assessed soil characteristics and microbial community structure and function between agricultural field plots with and without cover crops. We expected microbes would respond in the short‐term to increasing cover crop biomass, with increases in microbial activity and a shift in C acquisition toward substrates indicative of root exudation. In the presence of cover crops, we found active microbial biomass and bioavailable‐C increased by 64 and 37%, respectively, indicating the potential for increased C sequestration. Soil NH4+ increased by 64%, whereas soil NO3‐ decreased by 30%, indicating a shift toward less mobile N forms and the potential of greater nutrient retention under cover cropping regimes. Additionally, increasing cover crop biomass was related to lower microbial biomass C/N ratios and to decreased utilization of recalcitrant C substrates. These results potentially suggest a shift toward greater microbial utilization of root‐derived compounds with increasing cover crop biomass. Together, these results indicate that, in the short‐term, the presence of cover crops may improve soil quality, as measured by indices of microbial activity, and soil C and nutrients.

Effects of different management practices on soil microbial community structure and function in alpine grassland

Identifying spatiotemporal influences on soil microbial community (SMC) structure is critical to our understanding of patterns in biogeochemical cycling and related ecological services (e.g. plant community structure, water quality, and response to environmental change). Because forest canopy structure alters the spatiotemporal patterning of precipitation water and solute supplies to soils (via ‘throughfall’), is it possible that changes in SMC structure could arise from modifications in canopy elements? Our study investigates this question by monitoring throughfall water and dissolved ion supply to soils beneath a continuum of canopy structure: from large gaps (0% cover), to bareQuercus virginianaMill. (southern live oak) canopy (~50–70%), to heavyTillandsia usneoidesL. (Spanish moss) canopy (>90% cover). Throughfall water supply diminished with increasing canopy cover, yet increased wash off/leaching of Na+, Cl‐, PO43‐, and SO42‐from the canopy to the soils. Presence ofT. usneoidesdiminished throughfall NO3‐, but enhanced NH4+, concentrations supplied to subcanopy soils. The mineral soil horizon (0–10 cm) sampled in triplicate from locations receiving throughfall water and solutes from canopy gaps, bare canopy, andT. usneoides‐laden canopy significantly differed in soil chemistry parameters (pH, Ca2+, Mg2+, and cation‐exchange capacity). Polymerase chain reaction denaturant gradient gel electrophoresis banding patterns beneath similar canopy covers (experiencing similar throughfall dynamics) also produced high similarities per analyses of similarity and clustered together when analysed by nonmetric multidimensional scaling. These results suggest that modifications of forest canopy structures are capable of affecting mineral soil horizon SMC structure via throughfall when canopies' biomass distribution is highly heterogeneous. As SMC structure, in many instances, relates to functional diversity, we suggest that future research seek to identify functional diversity shifts (e.g. nitrogen transformation) in response to canopy structural alterations of throughfall water/solute concentration. Copyright © 2015 John Wiley & Sons, Ltd.

Sulfur (S) is an essential nutrient for plant growth, influencing not only crop yields but also the composition and function of soil microbial communities. However, the differential effects of S fertilization on abundant and rare taxa in agricultural soils remain poorly understood. This study investigates the impact of different S fertilizer types on maize yield and the structure and stability of soil microbial communities, with a particular focus on abundant and rare taxa. S fertilization led to significant increases maize yield on two typical soils (black soil and sandy soil) (5.3–24.3%) and altered soil properties, including reducing pH (0.04–0.20) and increasing the available sulfur (AS) content (3.8–8.0 mg kg−1), with ammonium sulfate having a more pronounced effect than elemental sulfur. Microbial analysis revealed distinct impacts on the diversity and community structure of both abundant and rare taxa. Elemental sulfur reduced the alpha diversity of abundant taxa more than ammonium sulfate, while NMDS indicated significant shifts in community structures, particularly among abundant taxa. Network analysis showed that S fertilization decreased the complexity of microbial interactions among rare taxa, with ammonium sulfate leading to simpler networks and elemental sulfur resulting in higher modularity. SEM highlighted that the diversity of rare taxa played a crucial role in influencing maize yield, alongside direct effects from soil properties such as AS and SAR (aryl sulfatase). Functional predictions demonstrated that amino acid metabolism and xenobiotic biodegradation and metabolism pathways were enriched in rare taxa, suggesting significant implications for soil health and crop productivity. This study provides new insights into the roles of abundant and rare bacterial taxa under S fertilization, emphasizing their importance in optimizing fertilization strategies for enhanced crop yield in specific soil types.

Human activities have significantly increased nitrogen (N) and phosphorous (P) inputs to terrestrial ecosystems. However, the impact of N and P enrichment on soil microbial community structure and functioning in temperate and alpine grassland ecosystems remains unclear. In this study, we investigated the responses of soil microbial communities to nutrient (N and P) additions in two temperate and one alpine grassland ecosystems in China. We measured soil chemical properties, microbial community composition (indicated by the phospholipid fatty acids, PLFA) and potential enzyme activities related to carbon (C), N, and P cycling in the peak growing season after 4 years of nutrient addition. We found that N addition reduced soil pH and increased soil total N content at two meadow sites, P addition increased soil total P content at all three sites, but both N and P additions had minimal effects on soil organic C content. Bacteria and total microbial abundances did not change after N and P additions, while fungi and arbuscular mycorrhizal fungi (AMF) abundances were suppressed by N addition. Moreover, the activity of soil extracellular enzymes involved in C, N and P cycling and their stoichiometric ratios were not responsive to N and P additions, except for inhibition of acid phosphatase by P addition at the temperate meadow site. Despite significant changes in soil chemistry (e.g., pH and available nutrients), soil microbial biomass (except fungi and AMF abundances), community structure, and enzyme activities (except phosphatase) were generally resistant to 4 years of N and P addition in the three temperate and alpine grassland ecosystems in China.

Soil microbial community structure, function and network along a mangrove forest restoration chronosequence

Land-use change affects the functionality of soil microbial communities: A chronosequence approach in the Argentinian Yungas

Soil microbial community structure and function mainly respond to indirect effects in a multifactorial climate manipulation experiment

The microplastisphere: Biodegradable microplastics addition alters soil microbial community structure and function

The effects of drought on soil dynamics after fire are poorly known, particularly its long-term (i.e., years) legacy effects once rainfall returns to normal. Understanding this is particularly important for nutrient-poor soils in semi-arid regions affected by fire, in which rainfall is projected to decrease with climate change. Here, we studied the effects of post-fire drought and its legacy on soil microbial community structure and functionality in a Cistus-Erica shrubland (Spain). Rainfall total and patterns were experimentally modified to produce an unburned control (natural rainfall) and four burned treatments: control (natural rainfall), historical control (long-term average rainfall), moderate drought (percentile 8 historical rainfall, 5months of drought per year), and severe drought (percentile 2, 7months of drought). Soil nutrients and microbial community composition (ester-linked fatty acid approach) and functionality (enzyme activities and C mineralization rate) were monitored during the first 4years after fire under rainfall treatments, plus two additional ones without them (six post-fire years). We found that the recovery of burned soils was lower under drought. Post-fire drought increased nitrate in the short term and reduced available phosphorus, exchangeable potassium, soil organic matter, enzyme activities, and carbon mineralization rate. Moreover, drought decreased soil total microbial biomass and fungi, with bacteria becoming relatively more abundant. Two years after discontinuing the drought treatments, the drought legacy was significant for available phosphorus and enzyme activities. Although microbial biomass did not show any drought legacy effect, the proportion of fungi and bacteria (mainly gram-positive) did, being lower and higher, respectively, in former drought-treated plots. We show that drought has an important impact on soil processes, and that some of its effects persist for at least 2years after the drought ended. Therefore, drought and its legacy effects can be important for modeling biogeochemical processes in burned soils under future climate change.