Litter and soil biodiversity jointly drive ecosystem functions

Vegetation types shape the soil micro-food web compositions and soil multifunctionality in Loess Plateau

Introduction

Vegetation degradation and soil erosion are severe problems in the Loess hilly region, rendering it one of the most ecologically vulnerable areas in China and globally. Vegetation restoration has been recognized as an effective approach to amending the fragile ecological environment and restoring degraded ecosystems.

Methods

The effects of different vegetation types: Caragana korshinskii, Prunus armeniaca L., Pinus tabuliformis Carrière, Medicago sativa L., and the control vegetation Stipa bungeana on soil micro-food webs and soil multifunctionality, as well as their response mechanisms to soil environmental drivers, were investigated using High-throughput sequencing technology.

Results

C. korshinskii significantly enhanced soil physicochemical properties and soil enzyme activities by facilitating the stability of the soil micro-food web structure driven by soil bacteria and fungi and increasing the soil multifunctionality in contrast to S. bungeana. Prunus armeniaca also improved soil multifunctionality by promoting soil organic carbon and alkaline phosphatase activity. However, the stability of the soil micro-food web structure and soil multifunctionality were suboptimal in P. tabuliformis and M. sativa. Soil pH, along with carbon, nitrogen, and phosphorus cycling nutrients and enzymes, profoundly influences the structure of the soil micro-food web and soil multifunctionality; among these factors, those related to the carbon and phosphorus cycles are identified as key influencing factors.

Discussion

Therefore, a vegetation restoration strategy prioritizing C. korshinskii as the dominant vegetation type, supplemented by P. armeniaca, significantly impacts restoring soil multifunctionality and stabilizing the soil micro-food web in Loess hill regions and comparable ecological areas.

Polyethylene microplastics distinctly affect soil microbial community and carbon and nitrogen cycling during plant litter decomposition

Plant litter is an important input source of carbon and nitrogen in soil. While microplastics (MPs) and plant litter are ubiquitously present in soil, their combined impact on soil biogeochemical processes remains poorly understood. To address this gap, we examined the soil changes resulting from the coexistence of plant litter (Alfalfa) and polyethylene microplastics (PE). The soil changes included physicochemical properties, composition of soil dissolved organic matter, and structure of the soil microbial community. The results showed that the addition of polyethylene (PE) inhibited the degradation of humus-like substances and decreased the quantity of humic acid-like compounds in soil dissolved organic matter (DOM). PE negatively impacted plant litter decomposition, disrupted soil organic carbon (SOC) breakdown, interfered with the nitrogen cycle, and significantly altered microbial community structures during the process. By day 35, SOC and total nitrogen (TN) levels were reduced by 39.8% and 10.1%, respectively, in the presence of PE. Furthermore, PE significantly decreased the abundance of nitrogen-fixing microbes, including Streptomyces (43.1%) and Bacillus (45.9%), which play key roles in nitrate reduction to ammonium. This study highlights the environmental effects of MPs on plant litter decomposition and their potential implications for soil biogeochemical processes.

Exploring Fungal Biodiversity in Crop Rotation Systems: Impact of Soil Fertility and Winter Wheat Cropping

This study investigated soil fungal biodiversity in wheat-based crop rotation systems on Chernozem soil within the Pannonian Basin, focusing on the effects of tillage, crop rotation, and soil properties. Over three years, soil samples from ten plots were analyzed, revealing significant fungal diversity with Shannon-Wiener diversity indices ranging from 1.90 in monoculture systems to 2.38 in a fertilized two-year crop rotation. Dominant fungi, including Fusarium oxysporum, Penicillium sp., and Aspergillus sp., showed distinct preferences for soil conditions such as pH and organic matter (OM). Conservation tillage significantly enhanced fungal diversity and richness, with the highest diversity observed in a three-year crop rotation system incorporating cover crops, which achieved an average winter wheat yield of 7.0 t ha-1-47% higher than unfertilized monoculture systems. Increased OM and nitrogen levels in these systems correlated with greater fungal abundance and diversity. Canonical correspondence analysis revealed strong relationships between fungal communities and soil properties, particularly pH and calcium carbonate content. These findings highlight the importance of tailored crop rotation and tillage strategies to improve soil health, enhance microbial biodiversity, and boost agricultural sustainability in temperate climates, providing valuable insights for mitigating the impacts of intensive farming and climate change.

Comparative Genomics of Fungi in Nectriaceae Reveals Their Environmental Adaptation and Conservation Strategies

This study presents the first genome assembly of the freshwater saprobe fungus Neonectria lugdunensis and a comprehensive phylogenomics analysis of the Nectriaceae family, examining genomic traits according to fungal lifestyles. The Nectriaceae family, one of the largest in Hypocreales, includes fungi with significant ecological roles and economic importance as plant pathogens, endophytes, and saprobes. The phylogenomics analysis identified 2684 single-copy orthologs, providing a robust evolutionary framework for the Nectriaceae family. We analyzed the genomic characteristics of 17 Nectriaceae genomes, focusing on their carbohydrate-active enzymes (CAZymes), biosynthetic gene clusters (BGCs), and adaptations to environmental temperatures. Our results highlight the adaptation mechanisms of N. lugdunensis, emphasizing its capabilities for plant litter degradation and enzyme activity in varying temperatures. The comparative genomics of different Nectriaceae lifestyles revealed significant differences in genome size, gene content, repetitive elements, and secondary metabolite production. Endophytes exhibited larger genomes, more effector proteins, and BGCs, while plant pathogens had higher thermo-adapted protein counts, suggesting greater resilience to global warming. In contrast, the freshwater saprobe shows less adaptation to warmer temperatures and is important for conservation goals. This study underscores the importance of understanding fungal genomic adaptations to predict ecosystem impacts and conservation targets in the face of climate change.

Warming enhances the negative effects of shrub removal on phosphorus mineralization potential

Shrubs have developed various mechanisms for soil phosphorus utilization. Shrub encroachment caused by climate warming alters organic phosphorus mineralization capability by promoting available phosphorus absorption and mediating root exudates. However, few studies have explored how warming regulates the effects of dominant shrubs on soil organic phosphorus mineralization capability. We provide insights into warming, dominant shrub removal, and their interactive effects on the soil organic phosphorus mineralization potential in the Qinghai-Tibetan Plateau. Real-time polymerase chain reaction was used to quantify the soil microbial phosphatase genes (phoC and phoD), which can characterize the soil organic phosphate mineralization potential. We found that warming had no significant effect on the soil organic phosphate-mineralized components (total phosphate, organic phosphate, and available phosphate), genes (phoC and phoD), or enzymes (acid and alkaline phosphatases). Shrub removal negatively influenced the organic phosphate-mineralized components and genes. It significantly decreased soil organic phosphate mineralization gene copy numbers only under warming conditions. Warming increased fungal richness and buffered the effects of shrub removal on bacterial richness and gene copy numbers. However, the change in the microbial community was not the main factor affecting organic phosphate mineralization. We found only phoC copy number had significant correlation to AP. Structural equation modelling revealed that shrub removal and the interaction between warming and shrub removal had a negative direct effect on phoC copy numbers. We concluded that warming increases the negative effect of shrub removal on phosphorus mineralization potential, providing a theoretical basis for shrub encroachment on soil phosphate mineralization under warming conditions.

Keystone taxa enhance the stability of soil bacterial communities and multifunctionality under steelworks disturbance

Continuous discharge of wastewater, emissions, and solid wastes from steelworks poses environmental risks to ecosystems. However, the role of keystone taxa in maintaining multifunctional stability during environmental disturbances remains poorly understood. To address this, we investigated the community diversity, assembly mechanisms, and soil multifunctionality of soils collected from within the steelworks (I), within 2.5 km radius from the steelworks (E), and from an undisturbed area (CK) in Jiangsu Province, China, via 16 S rRNA sequencing. Significant differences were found in the Chao1 and the richness indexes of the total taxa (p < 0.05), while the diversity of keystone taxa was not significant at each site (p > 0.05). The deterministic processes for total taxa were 42.9%, 61.9% and 47.7% in CK, E, and I, respectively. Steelworks stress increased the deterministicity of keystone taxa from 52.3% in CK to 61.9% in E and I soils. The average multifunctionality indices were 0.518, 0.506 and 0.513 for CK, E and I, respectively. Although the soil multifunctionality was positive correlated with α diversity of both the total and keystone taxa, the average degree of keystone taxa in functional network increased significantly (79.96 and 65.58, respectively), while the average degree of total taxa decreased (44.59 and 51.25, respectively) in the E and I. This suggests keystone taxa contribute to promoting the stability of ecosystems. With increasing disturbance, keystone taxa shift their function from basic metabolism (ribosome biogenesis) to detoxification (xenobiotics biodegradation, metabolism, and benzoate degradation). Here we show that keystone taxa are the most important factor in maintaining stable microbial communities and functions, providing new insights for mitigating pollution stress and soil health protection.

Interguild fungal competition in litter and soil inversely modulate microbial necromass accumulation during Loess Plateau forest succession

Microbial interactions determine ecosystem carbon (C) and nutrient cycling, yet it remains unclear how interguild fungal interactions modulate microbial residue contribution to soil C pools (SOC) during forest succession. Here, we present a region-wide investigation of the relative dominance of saprophytic versus symbiotic fungi in litter and soil compartments, exploring their linkages to soil microbial residue pools and potential drivers along a chronosequence of secondary Chinese pine (Pinus tabulaeformis) forests on the Loess Plateau. Despite minor changes in C and nitrogen (N) stocks in the litter or soil layers across successional stages, we found significantly lower soil phosphorus (P) stocks, higher ratios of soil C: N, soil N: P and soil C: P but lower ratios of litter C: N and litter C: P in old (>75 years) than young stands (<30 years). Pine stand development altered the saprotroph: symbiotroph ratios of fungal communities to favor the soil symbiotrophs versus the litter saprotrophs. The dominance of saprotrophs in litter is positively related to microbial necromass contribution to SOC, which is negatively related to the dominance of symbiotrophs in soils. Antagonistic interguild fungal competition in litter and soil layers, in conjunction with increased fungal but decreased bacterial necromass contribution to SOC, jointly contribute to unchanged total necromass contribution to SOC with stand development. The saprotroph: symbiotroph ratios in litter and soil layers are mainly driven by soil P stocks and stand parameters (e.g., stand age and slope), respectively, while substrate stoichiometries primarily regulate microbial necromass accumulation and fungal: bacterial necromass ratios. These results provide novel insights into how microbial interactions at local spatial scales modulate temporal changes in SOC pools, with management implications for mitigating regional land degradation.

Trophic interactions in soil micro-food webs drive ecosystem multifunctionality along tree species richness

Rapid biodiversity losses under global climate change threaten forest ecosystem functions. However, our understanding of the patterns and drivers of multiple ecosystem functions across biodiversity gradients remains equivocal. To address this important knowledge gap, we measured simultaneous responses of multiple ecosystem functions (nutrient cycling, soil carbon stocks, organic matter decomposition, plant productivity) to a tree species richness gradient of 1, 4, 8, 16, and 32 species in a young subtropical forest. We found that tree species richness had negligible effects on nutrient cycling, organic matter decomposition, and plant productivity, but soil carbon stocks and ecosystem multifunctionality significantly increased with tree species richness. Linear mixed-effect models showed that soil organisms, particularly arbuscular mycorrhizal fungi (AMF) and soil nematodes, elicited the greatest relative effects on ecosystem multifunctionality. Structural equation models revealed indirect effects of tree species richness on ecosystem multifunctionality mediated by trophic interactions in soil micro-food webs. Specifically, we found a significant negative effect of gram-positive bacteria on soil nematode abundance (a top-down effect), and a significant positive effect of AMF biomass on soil nematode abundance (a bottom-up effect). Overall, our study emphasizes the significance of a multitrophic perspective in elucidating biodiversity-multifunctionality relationships and highlights the conservation of functioning soil micro-food webs to maintain multiple ecosystem functions.