Ecological restoration is widely implemented to recover degraded lands, yet the microbial mechanisms underpinning soil organic carbon (SOC) sequestration during this process remain poorly understood, particularly regarding how nutrient availability shapes microbial community traits and necromass accumulation. In this study, we utilized a space-for-time substitution method across a tropical ecological restoration chronosequence (comprising rubber monoculture, near-natural rainforest, and primary rainforest) and integrated analyses of soil properties, microbial biomarkers, and molecular sequencing to investigate the linkages between microbial nutrient limitation, community structural and functional traits, and soil carbon fractions. Our results showed that ecological restoration significantly improved litter and soil nutrient stoichiometry, alleviating microbial carbon (C) and phosphorus (P) limitation. This variation drove a shift in microbial life-history strategies from high growth yield strategies to resource-acquisition/stress-tolerance strategies, increasing microbial carbon use efficiency (19–60%), richness (27–79%), biomass (10–64%), and network complexity (1.9–3.3-fold) while reducing competitive interactions. Concurrently, stochastic processes became more dominant in community assembly. Metagenomic analysis revealed enhanced expression of genes involved in C fixation, recalcitrant C degradation (e.g., lignin degradation), and P cycling. Consequently, microbial necromass C, particularly fungal-derived C, increased significantly (13–61%) and emerged as a stronger direct driver of SOC accumulation than plant-derived C, despite a decrease in its proportional contribution to the SOC pool. These results suggest that alleviated nutrient limitation is linked to coordinated shifts in microbial metabolism and community characteristics, which in turn promote necromass accumulation and contribute to SOC sequestration. This study underscores the necessity of integrating microbial metabolic traits into soil carbon management strategies for degraded tropical plantations.

Revegetation strongly influences the dynamics of soil organic carbon (SOC) and microbial communities. While microbial communities are known to drive carbon (C) cycling, the specific traits responsible for C stabilization and mineralization during the revegetation of degraded karst ecosystems are not well understood. This study used a combination of metagenomic and instrumental methods to investigate variations in soil physicochemical properties, organic C fractions, C-cycle microbial community traits (diversity, life strategies, and co-occurrence patterns), and C-cycling (fixation and degradation) genes across four karst ecosystems representing a revegetation chronosequence encompassing cropland, grassland, shrubland, and primary forest. Our findings demonstrated that revegetation increased total SOC and recalcitrant OC (ROC) contents, while it decreased dissolved inorganic nitrogen (DIN) and reduced the ratio of labile OC (LOC) to SOC. This indicates enhanced C pool stabilization and storage, alongside reduced soil nutrient availability. These shifts favored the development of C-cycle microbial communities with low diversity and high proportions of K-strategists, which efficiently utilize recalcitrant C under oligotrophic conditions. Consequently, the increased dominance of K-strategists redirected microbial resource acquisition, manifested in a 29 % decrease in C-fixation gene abundances (rTCA, WL, and DC/4-HB pathways) and a 27 % decrease in genes degrading labile C compounds (starch, hemicellulose, cellulose, and chitin). Conversely, genes involved in degrading recalcitrant C compounds (pectin and lignin) increased by 19 %. Furthermore, the elevated proportion of K-strategists enhanced the complexity and stability of microbial taxonomic and functional networks, potentially strengthening community resilience and nutrient cycling efficiency. These results reveal a causal link between shifts in the soil C pool and nutrient availability during revegetation and the subsequent reshaping of C-cycling microbial communities. Such restructured communities, in turn, drive the expression of genes associated with C stabilization and mineralization, thereby impacting the soil C pool. This study provides mechanistic insights into microbial-mediated biochemical processes governing soil C decomposition and stabilization in karst ecosystems, offering critical guidance for ecological restoration in these degraded and fragile regions.

The conversion of primary forests into monoculture plantations is a widespread phenomenon in the tropics, while the restoration of abandoned agricultural lands has gained considerable attention in recent years. Phosphorus (P) is an essential nutrient with very low availability from the soil, constraining the productivity and functioning of tropical ecosystems. However, the impacts of forest restoration on soil P cycling and the underlying mechanisms remain unclear. In Southwestern China, we investigated the plant community characteristics, soil P cycling dynamics, and soil physicochemical properties under different land uses (including monoculture plantations, farmland-regenerated secondary forests, rubber plantation-regenerated secondary forests, and primary rainforests), and identified the predictors of soil available P. We found that the conversion of primary rainforests into monoculture plantations not only substantially decreased tree diversity but also modified soil P cycling (such as total, available, microbial P and phosphatase activity). In contrast, the regeneration of secondary forests (from both farmlands and rubber plantations) significantly enhanced tree diversity and improved soil physicochemical conditions compared to monoculture plantations, thereby promoting soil P bioavailability through increased soil organic carbon, microbial P and phosphatase activity. Soil organic carbon, microbial biomass P and fine root were the main predictors of soil available P, for both annual and seasonal timeframes. Notably, the soil C:P ratio exhibited a more pronounced impact on soil available P during the dry season, while acid phosphatase exerted greater influence during the rainy season. Furthermore, the presence of fine roots and leguminous trees significantly and positively influenced soil P cycling, particularly in the surface soil layers. Thus, these results suggest that establishing legumes-rich, diverse communities and ensuring organic inputs is beneficial for sustaining soil P resources in tropical areas. This work offers important guidance for policy-makers to navigate the trade-offs between conservation and production goals in land development.

Forest restoration is a well-established approach for effective soil rehabilitation, yet how soil microorganisms influence soil fertility at the soil aggregate microscale during tropical forest restoration remains unclear. We investigated the changes in soil microbial diversity and composition across four forest types: a tropical rainforest, a rubber monoculture plantation, and two restored types (natural restoration of rubber monoculture and natural restoration of rubber tree with tea tree intercropping). Results showed that soil fertility (soil organic C, total N, and total P), pH, and electrical conductivity (EC) exhibited increasing trends following forest restoration or decreasing soil aggregate fractions. Forest restoration and soil aggregate fractions were identified as the key predictors of microbial community structure. This relationship may be attributed to enhanced resource availability caused by increased plant diversity, pH, and EC in the restored forests. Smaller aggregates provide physical protection and retain more nutrients, thereby promoting microbial activity and diversity. PLS-PM showed that microbes constituted the primary contributor among all the factors driving soil fertility. Strong positive correlations were observed between soil fertility and microbial communities, particularly in the dominant phyla and microbial networks. Specifically, the abundance of r-strategy bacteria (Bacteroidota, Actinobacteria, and Proteobacteria) increased with forest restoration and decreasing aggregate size fractions. Similarly, fungal K-strategists (Basidiomycota) increased following forest restoration, whereas fungal r-strategists (Mortierellomycota) increased in the smaller aggregate size fractions. Microbial networks became more complex and tighter with forest restoration and decreasing aggregate size fractions. These shifts in microbial life strategies and co-occurrence patterns likely enhance the formation of microbial-derived organic matter, improve the efficiency of resource allocation and ecological signal transmission, and thereby promote soil fertility accumulation. Overall, this study highlights the critical role of forest restoration in abandoned rubber plantations in reshaping soil microbial communities and emphasizes the potential of soil microbes as indicators of soil resilience and health.

Forest restoration is an effective method for restoring degraded soil ecosystems (e.g., converting primary tropical forests into rubber monoculture plantations; RM). The effects of forest restoration on microbial community diversity and composition have been extensively studied. However, how rubber plantation-based forest restoration reshapes soil microbial communities, networks, and inner assembly mechanisms remains unclear. Here, we explored the effects of jungle rubber mixed (JRM; secondary succession and natural restoration of RM) plantation and introduction of rainforest species (AR; anthropogenic restoration established by mimicking the understory and overstory tree species of native rainforests) to RM stands on soil physico-chemical properties and microbial communities. We found that converting tropical rainforest (RF) to RM decreased soil fertility and simplified microbial composition and co-occurrence patterns, whereas the conversion of RM to JRM and AR exhibited opposite results. These changes were significantly correlated with pH, soil moisture content (SMC), and soil nutrients, suggesting that vegetation restoration can provide a favorable soil microenvironment that promotes the development of soil microorganisms. The complexity and stability of the bacterial-fungal cross-kingdom, bacterial, and fungal networks increased with JRM and AR. Bacterial community assembly was primarily governed by stochastic (78.79 %) and deterministic (59.09 %) processes in JRM and AR, respectively, whereas stochastic processes (limited dispersion) predominantly shaped fungal assembly across all forest stands. AR has more significant benefits than JRM, such as a relatively slower and natural vegetation succession with more nutritive soil conditions, microbial diversity, and complex and stable microbial networks. These results highlight the importance of sustainable forest management to restore soil biodiversity and ecosystem functions after extensive soil degradation and suggest that anthropogenic restoration can more effectively improve soil quality and microbial communities than natural restoration in degraded rubber plantations.

Glomalin-related soil protein (GRSP) is a potential byproduct of arbuscular mycorrhizal fungi (AMF) and a major contributor to the passive soil organic carbon (SOC) pool. Despite its crucial role in SOC storage, we know little about the response of GRSP to anthropogenic global change factors (GCFs). Here, using 530 observations from 107 primary studies, we conducted a global meta-analysis to unravel the effects of multiple GCFs (climate change, plant invasion (PI), wildfire, urbanization, land-use change (LUC), and nutrient addition (nitrogen; N, phosphorus; P, and potassium; K) on two functional GRSP fractions (easily extractable- (EE-) and total- (T-) GRSPs) in terrestrial ecosystems. We found that elevated carbon-dioxide increased T-GRSP by 28%, combined NP addition by 39.9%, and NPK addition by 29.5%. Climate warming and alone N addition increased EE-GRSP solely by 2.4% and 13.6%, respectively, but did not influence T-GRSP. However, urbanization and drought decreased T-GRSP by 26% and 15%, respectively. The LUC from natural ecosystems to cropland decreased T-GRSP by 40%, while afforestation in croplands increased it by 32%. Other GCFs (PI, wildfire, and P) had non-significant effects on GRSP probably because of (i) minor changes in AMF activity and (ii) the counterbalancing of effects by opposite processes. GCF impacts were robust when applied at higher intensities for medium-to-long durations (3–10＋ years) in humid conditions and clay-rich soils. The sandy soils experienced greater T-GRSP losses during LUC. Increases in T-GRSP were positively correlated with AMF-root colonization, soil mean-weight diameter, and SOC content. Further, our structure equation model confirmed that GCFs directly influence SOC by altering AMF-GRSP production and indirectly affecting soil aggregate formation and protection, suggesting that optimizing GRSP production can enhance SOC sequestration.

Rainforest conversion into rubber (Hevea brasiliensis) plantations (RP) alters global carbon cycling and contributes to climate change. However, the impact of this widespread tropical land use change on various elements of the carbon cycle is poorly understood. Here, we aimed to investigate the impact of rainforest conversion into RP on soil-dissolved organic carbon (DOC), one of the most mobile organic matter (OM) in the terrestrial ecosystem that causes the transformation and migration of C. We also explored the underlying edaphic factors regulating soil DOC changes. Our study sites were rubber monoculture, mixed-rubber plantations (H. brasiliensis, Ficus langkokensis, and Actinodaphne henryi), and a reference rainforest. We found that soil DOC concentration was 150-200% higher in RP than in rainforests, with an unchanged pattern across the seasons (dry and rainy) and plantation type. These results were concomitant with degradation in main soil properties, markedly including lower pH, electrical conductivity, SOC, available nitrogen, available phosphorus, total nitrogen (TN), and total phosphorus (TP), following the RP establishment and explicitly having a significant negative correlation with DOC. Our fitted structure equation model (SEM) highlights that RP caused accelerated DOC production and a higher DOC/DN ratio by decreasing SOC (38.5%) and nutrients (TN and TP). Further, the SEM revealed a significant negative correlation between microbial biomass C (MBC) and N (MBN) and the DOC/DN ratio, implying limited microbial degradation of DOC under RP. This is further supported by our findings of 81.1% lower MBC per unit DOC and 37.1% lower MBN per unit DN under RP compared to rainforests, indicating poor transformation of DOC to microbial biomass under RP. Collectively, our findings suggest that RP with high nutrient demands and altered soil properties lead to increased leaching of DOC due to its limited utilization by microbes. These findings underscore the importance of robust and sustainable soil management (such as optimizing plant density and legume intercropping) in RP to improve soil health and minimize DOC leaching and its potential environmental consequences.

The deterioration of soil and water resources resulting from tropical rainforest (TR) conversion to monoculture plantations (e.g., rubber monoculture; RM) could be restrained and restored through intercropping. However, the response of soil properties and forest water conservation function to forest conversion, i.e., the conversion of RM to rubber rainforest (RR: derived from the invasion of wild native plants in abandoned RM), is still unclear. We involved four forests types, TR, RM, rubber-tea agroforestry (RTA), and RR, as transitional steps of forest conversion through a space-for-time substitution approach to examine the dynamic of soil physical, hydrological and chemical properties during the forest conversion (from TR to RM, RM to RTA, RTA to RR, and retransformation into TR). The results show that SOC, TN, TP, and TK decreased in the order of TR > RR > RTA > RM, which was followed by the trend of soil hydrological and physical properties among these forest types. The interrelation between soil physical and chemical properties was mediated by water flow behaviours. High macroporosity and related low Ks in TR favoured the occurrence of water flow behaviours. Water flow behaviours not only influenced the distribution of soil chemical elements but also played a crucial role in forming appropriate conditions for nutrient turnover. The co-occurrence of preferential and matrix flow was more prevalent in the rainy season than dry season due to the higher frequency and higher amount of rainwater. The preferential flow promoted the soil water flow in the water flow paths and enhanced water storage in the soil pores. In short, the soil properties and soil water supply decreased in the following order: TR > RR > RTA > RM, suggesting that the severe soil degradation that occurred after TR conversion to RM can be restored back to the extent of TR after a period of succession. The results provided new insights for understanding the forest water conservation function and soil properties in response to forest conversion and highlighted that the RR appeared as a transitional stage during the course of forest restoration from RM to TR under low rubber demand. These findings improve the current knowledge of the relationship among soil physical, hydrological and chemical properties in the rubber-growing humid tropical region of Southeast Asia.

Technogenic soil (technosol) developed from coal fly ash (FA) landfilling has been considered a critical environmental problem worldwide. Drought-tolerant plants often naturally grow on FA technosol. However, the impact of these natural revegetations on the recovery of multiple ecosystem functions (multifunctionality) remains largely unexplored and poorly understood. Here we assessed the response of multifunctionality, including nutrient cycling (i.e., carbon, nitrogen, and phosphorus), carbon storage, glomalin-related soil protein (GRSP), plant productivity, microbial biomass carbon (MBC), microbial processes (soil enzyme activities), and soil chemical properties (pH and electrical conductivity; EC) to FA technosol ten years' natural revegetation with different multipurpose species in Indo-Gangetic plain, and identified the key factors regulating ecosystem multifunctionality during reclamation. We evaluated four dominant revegetated species: Prosopis juliflora, Saccharum spontaneum, Ipomoea carnea, and Cynodon dactylon. We found that natural revegetation initiated the recovery of ecosystem multifunctionality on technosol, with greater recovery under higher biomass-producing species (P. juliflora and S. spontaneum) than lower biomass-producing ones (I. carnea and C. dactylon). The individual functions (11 of the total 16 variables) at higher functionality (70 % threshold) also exhibited this pattern among revegetated stands. Multivariate analyses revealed that most of the variables (except EC) significantly correlated with multifunctionality, indicating the capability of multifunctionality to consider the tradeoff between individual functions. We further performed structural equation modeling (SEM) to detect the effect of vegetation, pH, nutrients, and microbial activity (MBC and microbial processes) on ecosystem multifunctionality. Our SEM model predicted 98 % of the variation in multifunctionality and confirmed that the indirect effect of vegetation mediated by microbial activity is more important for multifunctionality than their direct effect. Collectively, our results demonstrate that FA technosol revegetation with high biomass-producing multipurpose species promotes ecosystem multifunctionality and emphasizes the significance of microbial activity in the recovery and maintenance of ecosystem attributes.

Fungus-feeding termites are considered to be ecosystem engineers because of their ability to construct massive and complex mounds with different soil physicochemical and biological properties in tropical ecosystems. However, the impact of the termite nesting process on soil microbial communities and microbial functions related to nutrient cycling is poorly understood. In this study, we investigated termite-induced changes in soil microbial communities and their nutrient cycling functions within termite mounds (i.e. live mounds and abandoned mounds) in the humid tropical region of Southwest China. We found that the live mounds harbour intermediate microbial community richness (i.e. PLFAs, fungi, bacteria, G+, and G- bacteria) between surrounding topsoils and deep soils, with the ratio of fungi to bacteria (F:B) in mounds being significantly higher than in surrounding soils. However, the microbial communities gradually transformed to resemble the surrounding soils after the mounds were abandoned because of natural weathering and plant invasion. A relatively more uniform distribution of microbial communities was found within live mounds than in abandoned mounds and surrounding soils, suggesting that termites shaped the environment within the mounds, leading to the homogenisation of microbial communities. In addition, the termite-induced changes of soil physicochemical properties (e.g. water content, pH, organic matter, total N and P) were closely linked to microbial communities. We also observed a reduction in microbial processes associated with nutrient cycling, including microbial respiration, and extracellular enzymatic activities, in mounds relative to the surrounding topsoils. These findings have important implications for exploring microbial communities within termite mounds, which is critical to understand the potential role of termites in regulating soil carbon and nitrogen cycling in tropical ecosystems.

Soil erosion by water is a serious global ecological issue that leads to land degradation and threatens ecosystem sustainability. Splash erosion resulting from raindrop impact is the first stage of the erosion process and is mainly responsible for the detachment and migration of soil surface aggregates. In humid tropical regions, however, there has been little quantitative analysis of the relations between splash erosion and variable aggregate characteristics such as stability, particle size distribution and organic matter content. The objective of the current study was to determine how rain splash erosion is related to soil aggregate characteristics under land-use change, i.e., the conversion of tropical rainforest (TR) into rubber plantation (RP). Splash cups containing dry-sieved aggregate samples with eight size classes were exposed to natural rainfall to measure the splash erosion rate. The results showed that the initial aggregate organic carbon, water-stable aggregate index (WSA) and mean weight diameter (MWD) decreased by 31%, 9% and 48%, respectively, after 32 years of rubber cultivation. These degenerations in aggregate properties increased the susceptibility of soil aggregates to erosion and mutually contributed to a higher average splash erosion rate in RP (1.20 kg m-2) than in TR (1.09 kg m-2), regardless of aggregate size fractions. Splash erosion rates for all aggregate sizes were significantly positively correlated with rainfall kinetic energy, rainfall amount and intensity during the study period. The average splash erosion rate of aggregates first increased and then decreased with a decline in aggregate size in both TR and RP. The minimum and maximum splash rates were observed within 10-8 mm and 0.5-0.25 mm size fractions, respectively. In particular, the proportion of small-sized aggregates (i.e., 1-0.15 mm) with a relatively high splash erosion rate increased remarkably after land-use change. This exerted a negative impact on splash erosion control as well as on the sustainable development of rubber cultivation. Increasing the additional input of organic materials (e.g., intercropping cash crops with rubber trees) may help to enhance large aggregate formation and stabilization, which could minimize the risk of splash erosion at the aggregate scale for eroded rubber plantation ecosystems.

Natural tropical landscapes have been continuously altered by land use change and other climate factors. Forest management practices have transformed massive tropical forests into rubber plantations throughout mainland Southeast Asia and Southwest China. However, the effect of the forest-to-plantation conversion on ecosystem functions associated with plant litter is limited. Here, we compare litterfall production, decomposition, nutrient return and nutrient use efficiency between a tropical natural forest (TNF) and a monoculture rubber plantation (MRP) in Xishuangbanna (China) over three years. Annual mean litterfall production was significantly higher in TNF (10.92 Mg ha−1 yr−1) than in MRP (5.23 Mg ha−1 yr−1). Production of leaf litter was positively correlated to that of total litterfall, suggesting that leaf litter could be reliably estimated from total litterfall. Temperature and solar radiation are dominant drivers of seasonal variation of litterfall production. The litterfall production was more sensitive to climate variables in MRP. The average stand litter and the decomposition quotient were 1.8 and 1.2 times greater in TNF than in MRP, respectively. The total nutrient return to the forest floor was 2.1 times higher in TNF (5.66 Mg ha−1 yr−1) than in MRP (2.76 Mg ha−1 yr−1); the return of each mineral element was significantly lower in MRP relative to TNF. The nutrient return preferentially occurred during the cold and dry seasons, which was consistent with the trend of litterfall. Relatively high N, P, Ca, and Mg use efficiencies were observed in MRP in line with their deficiency in the present tropical soils, indicating that rubber trees likely possess an efficient nutrient uptake mechanism to facilitate their adaption to oligotrophic habitats. Our results suggest that the large scale transformation of tropical forests to rubber plantations could alter the biogeochemical cycles related to litterfall, and thus possibly affect the resilience of ecosystems to climate variation. An increasing organic matter input in rubber monoculture may favor the sustainable development of rubber cultivation.

There is a direct link between the increasing human population and soil degradation that raises current and future food security concerns. Soil amelioration using beneficial microorganisms, particularly arbuscular mycorrhizal fungi (AMF), is essential and pragmatic. AMF produces glomalin that also contributes to the mitigation of soil degradation. However, studies on the ecological role of glomalin are scattered and patchy, and no evident overview exists. We fill this knowledge gap by a systematic and comprehensive literature review of the glomalin's role in the context of soil degradation problems, including soil desertification, fertility loss, and pollution. Glomalin improves soil physical properties, carbon sequestration, nutrient contents, microbial activities, stabilizes pollutants, and eventually assists ecological restoration. Such a positive impact of glomalin is thought to be through its prevailing impact on soil; by acting as a substrate for microbes, a gluing agent for aggregate formation, chelation of heavy metals and toxic pollutants, and improving carbon sequestration through long-term persistence (>= 42 years) in soil. Given the production of glomalin as a result of an interplay between plant, soil, and AMF, hence, we provide specific strategies at the plant, soil, and microbial level to improve glomalin concentration. Specifically, we can develop genetically modified or hybrid plants for higher rhizodeposition and promotes soil microbial diversity through the inoculation of AMF and beneficial bacteria. We highlight the research gaps and discuss prospects. This knowledge will improve our understanding of glomalin, stimulate future research, and be useful for the sustainable restoration of degraded lands.

Although the establishment of grazing exclosures is often considered an important strategy of reducing soil degradation, their effect on hydrological functions is still poorly understood, particularly in dry‐hot savanna systems with heavy livestock grazing. In addition, the different roles played by the herb roots and the niche differentiation of woody plant roots induced by the grazing and exclosure in soil hydrological functions are still unclear. This study aimed to evaluate the effect of exclosure management on hydrological functions and services and assess the role of different functional vegetation types in improving these functions and services. The experiments were conducted in the continuous grazing areas and exclosure areas in a savanna ecosystem in Yuanjiang, southwest China. The root biomass of herb and woody plants, soil physical properties, water infiltration, and preferential water flow were measured in each study site. The results showed a significant improvement in soil physical properties with more termite holes, lower soil bulk density, and higher total and non‐capillary soil porosity in exclosure areas compared with grazing ones. As a result, the initial and average water infiltration, and preferential flow significantly increased by 132.76%, 185.31%, and 30.29%, respectively, in exclosure areas compared with the grazing ones. The results also showed that the exclosure significantly improved the soil surface water content by increasing the root biomass of herb and woody plants in the shallow soil layers. Herb plants probably improved water infiltration and insulated evaporation, while woody plants improved lateral preferential water flow paths and accelerated the water exchange between vertical and horizontal soil layers, thereby improving the water availability for different plants. This study demonstrated that the exclosure‐induced restoration and niche differentiation of herb and woody plants, coupled with improved soil structure in exclosures, could promote hydrological function and services and improve water management in savanna systems. Therefore, the grazing exclosures could be expanded periodically and cautiously to prevent soil degradation in the present savanna systems.

Plant competition is a determinant of plant community formation, while resource partitioning is regarded as a critical factor for maintaining species coexistence under competition. However, how resource partitioning varies with species richness remains unclear; additionally, empirical studies of the dynamic processes involved in plant resource competition, especially that for belowground resources, are urgently needed. Here, we used the stable isotope approach to study the temporal dynamics of plant hydrological niches from species-poor to species-rich communities (including monocultural plantations, agroforestry systems and more diverse tropical rainforests) in a tropical area of southwestern China. We found that plant species in multispecies communities could be divided into two groups by comparison of their hydrological niches: deep-resource users and shallow-resource users. Resource partitioning was obvious between these two groups. However, resource partitioning was narrower within deep and shallow-resource users. In addition, with an increase in species richness, the general tendency of resource partitioning among all species became not just increasingly narrow but also uniform and stable. When we combined this information with data on belowground resource distribution and its correlations with plant resource use, we also found that the greater the species diversity and the smaller the resource use advantages among species, the easier it was for the species to achieve "competitive reversals". This study confirmed the generality of the seasonal segregation of the plant hydrological niche and demonstrated that variations in both environmental resources and plant resource partitioning weaken the resource use advantages of species, representing an important mechanism that helps maintain the coexistence of competing species in a species-rich community. These findings therefore provide novel insights for understanding species combinations and plant belowground interactions in complex communities and will be beneficial for seeking solutions to some important ecological issues, such as reconstruction of tropical rainforests.

The long-term cultivation of banana crops (Musa nana Lour.) has caused improper utilization of soil and water resources. However, the effect of the banana plantation regime on soil water flow pattern is still poorly understood. This study focused on the dominant pattern of soil water movement in the 1-year (B1) and 4-year (B2) old banana plantations. The results showed that: (1) the soil physical properties showed variability with soil depths, especially obvious changes from surface to 40 cm depth, which had restriction on soil infiltration in different depths. (2) The saturated hydraulic conductivity (Ks) decreased with the increasing distance from the banana stem. Moreover, the Ks in the B2 plot increased by 65.5% compared to the B1 plot at the soil layer 0-20 cm. (3) Preferential flow was the main path of soil water transport and was significantly influenced by soil bulk density, porosity, and root systems. Redundancy analysis (RDA) showed that banana root biomass was the most prominent factor influencing the dyed area. (4) The soil infiltrability and the preferential flow degree of both B1 and B2 plots were stronger in the root zone than those in the non-root zone. Such results were attributed to the root systems around the banana stem that were more developed than those far away from the stem (more accurately pseudostems); a large number of pore channels formed around the root systems that promoted the preferential flow. Or results suggest that banana root was the important factor affecting soil water movement. The improvement in the root network of banana plantation regime can result in better soil physical properties. This knowledge will be vital for the sustainable cultivation and irrigation of banana crops.

Forestry eco-hydrology is closely related to root architecture, and soil water infiltration has been always associated with root architecture. In this study, dye infiltration experiments and HYDRUS-1D were used to quantify the effects of different root architectures on the dynamics of soil water infiltration, volumetric water content, and soil water pressure head. The results provide evidence that root channels acted as preferential flow paths for water infiltration and percolation into the soil. Maize fibrous roots, rubber trees fine roots, and Spartina alterniflora smooth roots easily penetrated the plough layer of an agriculture site, the hard soil layer of a forest site, and the alternating sandy and mud layers of an intertidal zone, respectively. The initial and final infiltration rates were significantly different between the rooted and rootless soil profiles. The root-induced infiltration events lowered the propagation time of the wetting front across the rooted soil profile by 33%–113% than the rootless soil (p < 0.05), and the volumetric water content of the saturation zone of the rooted soil profile increased by 12%–19% relative to the rootless soil (p < 0.05). Furthermore, the soil water pressure head increased from negative (i.e., unsaturated) to positive (i.e., saturated) in the saturated soil. This change was more pronounced in the maize fibrous roots soil profile, but less pronounced in the rubber fine roots’ soil profiles or the S. alterniflora smooth roots. The results indicate that the downward movement, volumetric water content, and soil water pressure head were higher in soil profiles having plant roots than the rootless soil, and the degree of roots effects depended on roots architectures, soil hardness, and soil layer configuration. The findings provide evidence that root channels can act as preferential flow paths for water infiltration and percolation into the soil.

Banana is an important cash crop in tropical and subtropical areas; however, the development of banana farming has caused thorny ecological problems, such as water and soil loss. There are few studies on the runoff response to rainfall in banana land to date. In this study, several evaluation indexes, rainfall redistribution, throughfall erosivity, splash kinetic energy, soil splash loss and runoff, respectively, were used to clarify the mechanism of soil erosion in banana land. Results showed that the atmospheric rainfall was significantly redistributed by the banana canopy, with about 81.2% throughfall, 8.3% stemflow and the rest canopy interception. Although the throughfall erosivity evaluated by the model was slightly lower than that of open rainfall, the throughfall kinetic energy and the soil particle splash loss reached 1.5 times and 5 times higher than that of open rainfall, respectively. Consequently, throughfall has an obvious splash erosion effect on the surface soil. In addition, influenced by throughfall and stemflow, surface runoff during the rainy season (May–September) accounts for the annual 91.7%, July and August in particular having the highest incidence of soil erosion in banana land. The above results suggest that the convergence effect of the banana canopy on rainwater is the main inducement for the increase in throughfall volume and surface runoff volume. Therefore, it is necessary to implement soil and water conservation measures on banana fields during the rainy season, such as planting low vegetation under the banana canopy to mitigate splash effects.

Heavy metal pollution is becoming recurrent and threatens biota biosafety in many agricultural fields. Diverse solutions explore the application of amendments to enable remediation. Sulfur represents a nonmetallic chemical element that actively affects heavy metals phytoextraction, and promotes and alternatively mitigates soil functions. In this study, we conduct a meta-analysis to synthesize the current knowledge on the influence of sulfur amendments on plants heavy metals uptake from contaminated soil media. Random-effects model was used to summarize effect sizes from 524 data points extracted from 30 peer reviewed studies. The phytoextraction of cadmium, chromium and nickel were 1.6-, 3.3-, and 12.6-fold, respectively, higher when sulfur amendment was applied; while copper uptake was 0.3-fold lower. Irrespective of the sulfur type, heavy metal extraction increased with the raising sulfur stress. Individual organs showed significant differences of heavy metal uptake between sulfur applied and non-sulfur treatments, and combined organs did not. The heavy metals uptake in leaves and roots were higher in sulfur applied than non-sulfur applied treatments, while those in grain, husk, and stalks were lower. The heavy metals phytoextraction (response ratio) followed the order roots > leaves > stalk > grain > husk. Moreover, heavy metals uptake was 2-fold higher in the sulfur applied than the non-sulfur treatments under ideal (5.5-8) and alkaline conditions (8-14), and 0.2-fold lower under acidic pH (1-5.5). Cadmium, manganese and nickel, and chromium were the most extracted under sulfur application by Vicia sp., Sorghum sp. and Brassica sp., respectively; while chromium, manganese, and iron were the most uptake without sulfur amendments by Oryza sp., Zea sp. and Sorghum sp., respectively. Our study highlights that the influence of sulfur on heavy metal phytoextraction depends on the single or combined effects of sulfur stress intensity, sulfur compounds, plant organ, plant type, and soil pH condition.