● Ascomycetes of the genus Trichoderma are beneficial fungi that promote plant growth.

Plants drive both carbon and nitrogen cycling and mediate complex biotic interactions with soil microorganisms. Climate change and the resulting temperature variations, altered precipitation, and water shortages in soils, affect the performance of plants. Negative effects of abiotic stress are reflected in changes of plant morphology associated with biochemical alterations and inadequate adaptation to rapid ecological change. Accumulation of chemical agents, derived from pesticides, salinity due to chemical fertilization, and accumulation of heavy metals, are recurrent problems in agricultural soils. Trichoderma spp. are soil fungi interacting with roots and in this way helping plants to cope with abiotic stresses by increasing root branching, shoot growth and productivity. In part, such fungal effects on the host plant are consequences of the activation of fine-tuned molecular mechanisms mediated by phytohormones, by profound biochemical changes that include production of osmolytes, by the activity of the redox-enzymatic machinery, as well by as complex processes of detoxification. Here, we summarize the most recent advances regarding the beneficial effects of Trichoderma in mitigating the negative effects on plant performance caused by different environmental and chemical factors associated with global change and agricultural practices that provoke abiotic stress. Additionally, we present new perspectives and propose further research directions in the field of Trichoderma-plant interactions when the two types of organism cooperate.

● Rubber-based agroforestry systems increased the complexity of fungal networks.

Rubber-based agroforestry systems have been recognized as a practical and sustainable solution to promote the development of agriculture and the environment. However, interactions between fungal communities and these systems are still not sufficiently investigated. In this study, we compared the abundance, diversity, and community composition of soil fungi in four treatments, including rubber monoculture and three rubber-based agroforestry treatments involving intercropping with Camellia sinensis, Coffea liberica, and Theobroma cacao. The results revealed that the community composition exhibited significant variation between the four different treatments, while the overall soil α-diversity was relatively stable across all treatments. Soil pH and soil organic carbon were significantly related to the structure of the fungal community. In particular, the complexity of the functional fungal network increased in response to agroforestry treatments, promoting beneficial fungi and suppressing certain plant pathogens. These results suggest that rubber-based agroforestry systems can promote the health of soil microbial community composition, and therefore provide an effective approach to enhancing soil quality.

● Organic fertilization increased the richness and abundance of beneficial communities.

Soil microbiomes play a crucial role in maintaining ecological functions and are of great importance for soil health. Some of them could bring benefits to plants for growth promotion. Despite numerous studies have focused on specific beneficial bacteria and their interactions with soils and plants, we still lack a comprehensive understanding of beneficial communities in plant–soil continuums and their responses to agricultural activities. To address this gap, we carried out a microcosm experiment using 16S rRNA amplicon sequencing to explore the effects of organic fertilization on beneficial communities in plant–soil continuums and assess their potential multifunctionality. Our findings reveal that organic fertilization had a positive impact on the beneficial functionality of bacterial communities in plant–soil continuums. This improvement was primarily attributed to the optimized soil physicochemical conditions resulting from organic fertilization. Additionally, organic fertilization increased the complexity of bacterial co-occurrence networks in both soils and the endosphere. Keystone taxa in the endosphere undergone a shift of functions toward pathogen suppression as the result of organic fertilization. Furthermore, this study revealed that plants exhibited a preference for internalizing beneficial bacteria over other type of bacteria. We also provided new insights for evaluating the multifunctionality of microbiomes, and found that the functionality of beneficial communities in plant–soil continuums is enhanced by organic fertilization. All these findings suggested that organic fertilization can be an effective strategy for maintaining plant and soil health.

● Salt spray is a natural disturbance in coastal area of Southern China.

Salt spray is a natural disturbance in coastal region. Arbuscular mycorrhizal fungi (AMF) are recognized as bio-ameliorators of soil salinity in plants. However, the mechanism through which AMF protects Cinnamomum camphora against aerial salinity remains unclear. To address this knowledge gap, plants were subjected to four fungal regimes, namely sterilized fungal inoculum, Glomus tortuosum, Funneliformis mosseae, or a combination of these two fungi, and exposed to three sprayed-salt regimes (0, 7, or 14 mg NaCl cm⁻² d⁻¹) in a greenhouse. Salt spray significantly decreased photosynthetic capabilities, total dry weight, and salinity tolerance of non-mycorrhizal plants. Mycorrhizal inoculation, particularly a combination of G. tortuosum and F. mosseae, evidently mitigated the detrimental effects induced by salt spray. Meanwhile, mycorrhiza-mediated protection depended on the intensity of sprayed salt and the identity of fungal taxa. Furthermore, the enhanced resistance of mycorrhizal C. camphora seedlings to aerial salinity was mainly owing to increased leaf thickness and photosynthetic capabilities. These findings imply that inoculation with combined fungi could be an optimal strategy for cultivating C. camphora plants in coastal regions. The results gained hold the potential to offer both theoretical and practical guidance for the managers of coastal ecosystems in soil restoration and conservation.

● Rice planting decreased total iron but increased active iron.

Human activities have intensified the activity and morphological transformation of iron in soils, but there is a lack of quantitative assessment of the loss or of the transformation pattern. By studying Fe-rich rice soils in southern China and comparing them with corresponding woodland soils, it was found that rice planting reduced the total iron (Fe_t) content, mainly of crystalline iron (Fe_c), along soil profiles (0−100 cm) while increasing the content of active iron (Fe_o). The activation degree of Fe_o (Fe_o%) varied significantly among different parent materials in paddy soils but showed less variation in woodland soils. Regression analysis revealed significant correlations between both the content of Fe_c and the content of Fe_o in paddy soils with soil organic carbon (SOC) and particle composition (p < 0.05). The Fe_o% was primarily influenced by pH, SOC, and particle composition. The iron loss in paddy soil was mainly Fe_c and was closely related to SOC, whereas the transformation of active iron (Fe_o) was influenced by a combination of soil factors and environmental conditions. The results demonstrate that human activities accelerate the loss and activation of active iron in the soil, thereby altering the iron cycling process in rice paddy ecosystems.

● Land use type affects the physicochemical properties of soil.

Soil fertility is affected by land-use types and land management, which exacerbates soil erosion and various other forms of soil degradation in the mountainous regions of Vietnam. This study was conducted in A Luoi District, Thua Thien Hue, Vietnam to identify the effects of land-use types on specific soil physicochemical characteristics related to soil fertility. Soil physicochemical properties, such as organic matter (OM), total nitrogen (TN), total phosphorous (TP), and K⁺ were significantly affected by land-use type. The results showed that the soils were sandy in rice but clay loam for acacia and cassava. The mean bulk density value of acacia soil was significantly greater than that of other soils. TN were higher in the acacia soils than those in the rice, maize, and banana soils. The OM content was significantly higher in the acacia, cassava, and banana soils than those in the rice and maize soils. The mean of exchangeable K⁺ in the rice soil was higher compared to those in other soils and was affected by land-use type. The high exchangeable acidity content in the soils was probably due to intensive precipitation. However, both land use type and management did not affect the CEC value. Overall, the inappropriate land use caused the disturbance of soil physicochemical properties, indicating that the conditions of rice and maize soils are becoming worse than acacia soils. Therefore, lowering the intensity of cultivation, adopting incorporated soil fertility management, and applying organic fertilizer should preserve the existing conditions and enhance soil properties.

● High-quality and low-quality root litter had contrasting patterns of mass loss.

Decomposing root litter is a major contributor to soil carbon (C) storage in forest soils. During decomposition, the quality of root litter could play a critical role in soil C storage. However, it is unclear whether root litter quality influences soil C storage efficiency. We conducted a two-year greenhouse decomposition experiment using ¹³C-labeled fine root litter of two tree species to investigate how root litter quality, represented by C to nitrogen (C/N) ratios, regulates decomposition and C storage efficiency in subtropical forest soils in China. ‘High-quality’ root litter (C/N ratio = 26) decayed faster during the first year (0−410 days), whereas ‘low-quality’ root litter (C/N ratio = 46) decomposed faster toward the end of the two-year period (598−767 days). However, over the two years of the study, mass loss from high-quality root litter (29.14 ± 1.42%) was lower than ‘low-quality’ root litter (33.01 ± 0.54%). Nonetheless, root litter C storage efficiency (i.e., the ratio of new root litter-derived soil C to total mineralized root litter C) was significantly greater for high-quality root litter, with twice as much litter-derived C stored in soils compared to low-quality root litter at the end of the experiment. Root litter quality likely influenced soil C storage via changes in microbial diversity, as the decomposition of high-quality litter declined with increasing bacterial diversity, whereas the amount of litter-derived soil C from low-quality litter increased with fungal diversity. Our results thus reveal that root litter quality mediates decomposition and C storage in subtropical forest soils in China and future work should consider the links between root litter quality and soil microbial diversity.

● Decay stages and meteorological factors affect leaf litter’s microbial community.

Litter microorganisms play a crucial role in the biological decomposition in forest ecosystems; however, the coupling effect of meteorological and substrate changes on it during the different stages of leaf decomposition in situ remains unclear. Hence, according to meteorological factors dynamics, a one-year field litter of Quercus wutaishanica in situ decomposition experiment was designed for four decay stages in a warm temperate forest. Microbial community composition was characterized using Illumina sequencing of fungal ITS and bacterial 16S genes. Bacterial (6.6) and fungal (3.6) Shannon indexes were the largest after 125 days’ litter decomposition (October). The relative abundance of Acidobacteria after 342 days and Bacteroidetes after 125 days were 3 and 24 times higher than after 31 days, respectively. Some non-dominant species (bacteria: Firmicutes, Planctomycotes, and Verrucomicrobia; fungi: Chytridiomycota and Glomeromomycota) may be absent or present at different decomposition stages due to litter properties or meteorological factors. Chemoheterotrophy and aerobic-chemoheterotrophy were the dominant bacterial functional groups, and the dominant fungal functional groups were saprotrophs, pathotrophs, and symbiotrophs. Precipitation and relative humidity significantly affected bacteria. Temperature, sunlight intensity, and net radiation significantly affected fungi. Besides, among the relative contributions of changes in bacterial and fungal community structure, leaf litter properties alone explained the variation of 5.51% and 10.63%. Microbial diversity and decay stage directly affected the litter mass-loss rate, with meteorological factors (precipitation, relative humidity, air temperature, and sunlight intensity) being indirect. Our findings highlight the importance of microbial diversity for leaf litter decomposition and the influence of meteorological factors.

● Sexually dimorphic belowground responses to cope with drought.

How sex-related root traits and soil microbes and their interactions respond to drought remains unclear. Here, we investigated how fine root traits and the composition of rhizosphere microbial communities in Populus euphratica females and males respond to drought in concert in 17-year-old plantations. Females increased specific root length (SRL) in response to drought. However, males showed no changes in their roots but significant increases in arbuscular mycorrhizal hyphal biomass and population of Gram-negative bacteria in the rhizosphere. Also, fungal symbiotroph communities associated with root systems in males differed from those in females under drought. We further demonstrated that the Gram-positive to Gram-negative bacteria ratios positively correlated with the SRL, while fungi to bacteria ratios were negatively correlated. Meanwhile, the relative abundance of symbiotrophs was negatively correlated with the SRL, while saprotroph abundance was positively correlated. Nevertheless, the relative abundance of symbiotrophs was positively correlated with the root carbon content (RCC). These findings indicate that microbial responses to drought depend highly upon the sex of the plant and microbial group and are related to root trait adjustments to drought. This discovery also highlights the role of plant-microbial interactions in the ecosystems of P. euphratica forest plantations.

● Soil C-, N-, P-acquiring enzymes changed significantly during vegetation restoration.

Changes in litter quality (carbon:nitrogen, C:N) and above-ground biomass (AGB) following vegetation restoration significantly impact soil physicochemical properties, yet their effects on soil microbial metabolic limitations remain unclear. We measured litter quality, AGB, soil physicochemical properties, and extracellular enzyme activity (EEA) along a vegetation restoration gradient (7, 14, 49, 70 years, and nearly climax evergreen broadleaved forests) in southern China. We also evaluated soil microbial metabolic limitations by a vector analysis of the EEA. Results revealed the soil microbial metabolisms were co-limited by C and phosphorus (P). The microbial C limitation initially decreased (before 14 years) and then increased, while the microbial P limitation initially increased (before 49 years) and then decreased. Partial least squares path modeling (PLS-PM) showed that the microbial C limitation was mainly attributed to microbial C use efficiency induced by litter quality, suggesting that microorganisms may transfer cellular energy between microbial growth and C-acquiring enzyme production. The microbial P limitation was primarily correlated with AGB-driven change in soil elements and their stoichiometry, highlighting the importance of nutrient stoichiometry and balance in microbial metabolism. The shifts between microbial C and P limitations and the strong connections of plant–soil-microbe processes during vegetation restoration revealed here will provide us with helpful information for optimal management to achieve forest restoration success.

● The PSF of three species is positive in response to different soil origin.

Secondary succession is the process by which a community develops into a climax community over time. However, knowledge on the mechanisms, relating to soil legacy effects (soil chemistry and enzyme activity) and plant–soil feedback (PSF), driving community succession remains limited. In this work, we examined the PSF associated with three succession stage species through a 2-year greenhouse experiment. Setaria viridis, Stipa bungeana, and Bothriochloa ischemum were selected to represent dominant and representative early-, mid-, and late-successional stage species, respectively, of semiarid grasslands on the Loess Plateau. In response to the different soil origin, the shoot biomass of early-, mid-, and late-species were all higher when grown in their own soil than in other species’ soils, which indicated that the PSF of three species were positive. Over two growth periods, the early-species experienced a negative PSF, but the mid- and late-species experienced negative, neutral and positive PSF in the soil of early-, mid- and late-species, respectively. Our study demonstrates that soil legacy effects and PSF have a significant impact on community succession processes.

● The overall abundance of secondary metabolites-encoding genes in soil and root microbiomes is similar.

Secondary metabolites (SMs) produced by soil bacteria, for instance antimicrobials and siderophores, play a vital role in bacterial adaptation to soil and root ecosystems and can contribute to plant health. Many SMs are non-ribosomal peptides and polyketides, assembled by non-ribosomal peptides synthetase (NRPS) and polyketide synthase (PKS) and encoded by biosynthetic gene clusters (BGCs). Despite their ecological importance, little is known about the occurrence and diversity of NRPs and PKs in soil. We extracted NRPS- and PKS-encoding BGCs from 20 publicly available soil and root-associated metagenomes and annotated them using antiSMASH-DB. We found that the overall abundance of NRPSs and PKSs is similar in both environments, however NRPSs and PKSs were significantly clustered between soil and root samples. Moreover, the majority of identified sequences were unique to either soil- or root-associated datasets and had low identity to known BGCs, suggesting their novelty. Overall, this study illuminates the huge untapped diversity of predicted SMs in soil and root microbiomes, and indicates presence of specific SMs, which may play a role in inter- and intra-bacterial interactions in root ecosystems.

• Metabolic and non-metabolic benefits of AM fungi under intercropping were reviewed.

Intercropping, which gains productivity and ecological benefits through plant facilitative interactions, is a practice often associated with sustainable agriculture. In such systems, arbuscular mycorrhizal (AM) fungi and the hyphal networks play key roles in plant facilitation by promoting connectivity, mediating interplant transfer of metabolic resources, and managing weeds, pathogens, and contaminants. This review states that the symmetrically or unsymmetrically delivered resources via AM fungi are imperative to maintain facilitative interactions between intercrops. In addition, the responses of AM fungi to intercropping are also discussed, including changes in abundance, diversity, community composition and colonization level. Although general proliferations in AM fungi via intercropping have been shown, the plant hosts and neighbors may exert different influences on AM fungi. Therefore, further research is needed in quantifying the mediating role of AM fungi on outputs of intercropping systems, clarifying the driving forces, and exploring the causation between these processes and the changes in AM fungi themselves. To conclude, the integration with AM fungi extends the understanding of key soil biological processes driving plant facilitation and will guide efforts to optimizing intercropping systems.

• We performed a meta-analysis to synthesize the rhizosphere effect on soil gross nitrogen mineralization rate.

Rhizosphere effects play crucial roles in determining soil carbon (C) and nitrogen (N) cycling. However, the rhizosphere effect on soil gross nitrogen (N) mineralization (N_min) has not been quantitatively assessed on the global scale. Here we performed a meta-analysis of compiled data from 24 publications and 37 species to synthesize the rhizosphere effect on soil gross N_min and its influencing factors. We found that the rhizosphere effect significantly enhanced soil gross N_min by 81% on average. Such rhizosphere effect was significantly higher in woody species than in non-woody species, and higher in ECM (ectomycorrhizal) associated species than in AM (arbuscular mycorrhizal) associated species. Moreover, the variations of the rhizosphere effect on soil gross N_min were correlated with those on soil C mineralization, phenol oxidase activity and root biomass rather than with other plant (growth form and mycorrhizal association) and climatic (mean annual temperature and precipitation) factors. These results support the ‘microbial activation’ and ‘microbial N mining’ hypotheses of rhizosphere effects and indicate the coupling of soil C and gross N mineralization in the rhizosphere. Overall, these findings provide novel insights into the rhizosphere effect on soil gross N_min among plant growth forms and mycorrhizal associations, and improve our mechanistic understanding of soil N dynamics in the rhizosphere.

Leshan Giant Buddha is damaged seriously because of weathering and plant settlement

The accumulation of soil organic matter and nutrients are important pathways in effectively understanding the mechanisms of plant settlement and rock weathering, while the characteristics of soil organic carbon (C), nitrogen (N) and phosphorus (P) under different vegetation remains unclear. In this study, the stocks and stoichiometry of soil organic C, N and P were determined in different positions and types of vegetation on the surface of the Leshan Giant Buddha. We found that the total stocks of soil organic C, N and P were 1689.77, 134.6 and 29.48 kg, respectively, for the Buddha. The stocks of soil organic C, N and P under vascular plants were higher than those under other vegetation, with highest values observed under herb. Higher stocks per unit area (m²) of soil organic C, N and P were found on the left and right arms, shoulders, and two platforms. These results provide a full primary picture in understanding soil organic C, N and P accumulation and distribution on the surface of the Buddha, which could supply the fundamental data on weathering management of the Buddha and other similar open-air stone carvings.

• Elevated CO₂ increased the amounts of rhizodeposits.

Rhizodeposits in rice paddy soil are important in global C sequestration and cycling. This study explored the effects of elevated CO₂ and N fertilization during the rice growing season on the subsequent mineralization and retention of rhizodeposit-C in soil aggregates after harvest. Rice (Oryza sativa L.) was labeled with ¹³CO₂ under ambient (400 ppm) and elevated (800 ppm) CO₂ concentrations with and without N fertilization. After harvest, soil with labeled rhizodeposits was collected, separated into three aggregate size fractions, and flood-incubated for 100 d. The initial rhizodeposit-¹³C content of N-fertilized microaggregates was less than 65% of that of non-fertilized microaggregates. During the incubation of microaggregates separated from N-fertilized soils, 3%–9% and 9%–16% more proportion of rhizodeposit-¹³C was mineralized to ¹³CO₂, and incorporated into the microbial biomass, respectively,, while less was allocated to soil organic carbon than in the non-fertilized soils. Elevated CO₂ increased the rhizodeposit-¹³C content of all aggregate fractions by 10%–80%, while it reduced cumulative ¹³CO₂ emission and the bioavailable C pool size of rhizodeposit-C, especially in N-fertilized soil, except for the silt-clay fraction. It also resulted in up to 23% less rhizodeposit-C incorporated into the microbial biomass of the three soil aggregates, and up to 23% more incorporated into soil organic carbon. These results were relatively weak in the silt-clay fraction. Elevated CO₂ and N fertilizer applied in rice growing season had a legacy effect on subsequent mineralization and retention of rhizodeposits in paddy soils after harvest, the extent of which varied among the soil aggregates.

•Exotic species cannot obtain more biomass when growing in new areas.

Exotic species invasion represent important causes of harming the structure, function, and ecological environment in ecosystems. Yet, knowledge remains limited on the invasibility (invasion advantage of exotic species) and recoverability (recovery ability of native species) of a plant community following invasion depend on its successional stages. We selected three grasses of Setaria viridis, Artemisia gmelinii, and Bothriochloa ischemum representing early (E), middle (M), and late (L) successional species, respectively. Meanwhile, the grasses of Panicum virgatum was selected represent exotic species (invasion species). Three types of soil were collected to treat the three E, M, and L successional species, and one types of soil was collected to treat the exotic species. We compared the performance of the three native plant species and one exotic species grown in their “own” and “other” soils in a 2-year greenhouse experiment. Our study showed that exotic species performed better in soils of E and M successional species than in the soil of L successional species. After exotic species removed, E and M successional species exhibited poor growth in the soil of exotic species, while that of L successional species performed poor in field exotic species soils, but performed better in soils disturbed by exotic species. Our study demonstrated that the invasibility and recoverability of native plant communities changed with vegetation succession.

• Both plants and microbes were strictly homeostatic.

Nitrogen (N) deposition, the source of N input into terrestrial ecosystems, is exhibiting an increasingly serious impact on the biogeochemical cycle and functional stability of ecosystems. Grasslands are an important component of terrestrial ecosystems and play a key role in maintaining terrestrial ecosystem balance. Therefore, it is critical to understand the effects of nitrogen addition on grassland ecosystems. We conducted gradient N addition experiments (0, 3, 6, and 9 g N m⁻² y⁻¹) for three years in grassland communities with similar site conditions. We utilized four typical herbaceous plants, including the dominant species Bothriochloa ischemum (B. ischemum) and companion species Stipa bungeana (S. bungeana), Artemisia gmelinii (A. gmelinii), and Cleistogenes squarrosa (C. squarrosa), to explore how different plant–soil–microbe systems respond to N addition. Stoichiometric homeostasis analysis demonstrated that both plants and microbes were strictly homeostatic. However, the companion species were found to be more susceptible to P dominant species. Furthermore, aggravated overlap in stoichiometric niches between plant species were observed at the N6 and N9 levels. Vector analysis indicated that the vector angle was >45° regardless of plant species and N levels, suggesting that there was a strong P limitation in the rhizosphere microbial community. Variation partitioning analysis revealed that the Composite roots exhibited a greater effect (explaining 34.7% of the variation) on the rhizosphere microbes than on the Gramineae, indicating that there may be more intense nutrient competition in its rhizosphere. In general, the effects of N addition on species were different across functional groups, with a significant positive effect on the Gramineae (B. ischemum, S. bungeana, and C. squarrosa) and a significant negative effect on the Compositae (A. gmelinii), which should be fully considered in the future ecological management and restoration.