Soil Microbial Functional Diversity Research Articles

The Heterogeneous Habitat of Taiga Forests Changes the Soil Microbial Functional Diversity.

The soil contains abundant and diverse microorganisms, which interrelate closely with the aboveground vegetation and impact the structure and function of the forest ecosystem. To explore the effect of vegetation diversity on soil microbial functional diversity in taiga forests, we selected significantly different important values of Larix gmelinii as experimental grouping treatments based on plant investigation from fixed plots in Da Xing'anling Mountains. Following that, we collected soil samples and applied the Biolog-ECO microplate method to investigate differences in carbon source utilization, features of functional diversity in soil microorganisms, and factors influencing them in taiga forests. The AWCD decreased as the important value of Larix gmelinii grew, and soil microorganisms preferred carboxylic acids, amino acids, and carbohydrates over polymers, phenolic acids, and amines. The Shannon and McIntosh indexes decreased significantly with the increase of the important value of Larix gmelinii (p < 0.05) and were positively correlated with soil SOC, MBC, C/N, and pH, but negatively with TN, AP, and AN. Redundancy analysis revealed significant effects on soil microbial functional diversity from soil C/N, SOC, AP, MBC, TN, pH, AN, and WC. To sum up, heterogeneous habitats of taiga forests with different important values altered soil microbial functional diversity.

Impacts of vegetable processing and cheese making effluent on soil microbial functional diversity, community structure, and denitrification potential of land treatment systems.

The cheese making and vegetable processing industries generate immense volumes of high-nitrogen wastewater that is often treated at rural facilities using land applications. Laboratory incubation results showed denitrification decreased with temperature in industry facility soils but remained high in soils from agricultural sites (75% at 2.1°C). 16S rRNA, phospholipid fatty acid (PLFA), and soil respiration analyses were conducted to investigate potential soil microbiome impacts. Biotic and abiotic system factor correlations showed no clear patterns explaining the divergent denitrification rates. In all three soil types at the phylum level, Actinobacteria, Proteobacteria, and Acidobacteria dominated, whereas at the class level, Nitrososphaeria and Alphaproteobacteria dominated, similar to denitrifying systems such as wetlands, wastewater resource recovery facilities, and wastewater-irrigated agricultural systems. Results show that potential denitrification drivers vary but lay the foundation to develop a better understanding of the key factors regulating denitrification in land application systems and protect local groundwater supplies. PRACTITIONER POINTS: Incubation study denitrification rates decreased as temperatures decreased, potentially leading to groundwater contamination issues during colder months. The three most dominant phyla for all systems are Actinobacteria, Proteobacteria, and Acidobacteria. The dominant class for all systems is Nitrosphaeria (phyla Crenarchaeota). No correlation patterns between denitrification rates and system biotic and abiotic factors were observed that explained system efficiency differences.

Land conversion to agriculture induces taxonomic homogenization of soil microbial communities globally

Agriculture contributes to a decline in local species diversity and to above- and below-ground biotic homogenization. Here, we conduct a continental survey using 1185 soil samples and compare microbial communities from natural ecosystems (forest, grassland, and wetland) with converted agricultural land. We combine our continental survey results with a global meta-analysis of available sequencing data that cover more than 2400 samples across six continents. Our combined results demonstrate that land conversion to agricultural land results in taxonomic and functional homogenization of soil bacteria, mainly driven by the increase in the geographic ranges of taxa in croplands. We find that 20% of phylotypes are decreased and 23% are increased by land conversion, with croplands enriched in Chloroflexi, Gemmatimonadota, Planctomycetota, Myxcoccota and Latescibacterota. Although there is no significant difference in functional composition between natural ecosystems and agricultural land, functional genes involved in nitrogen fixation, phosphorus mineralization and transportation are depleted in cropland. Our results provide a global insight into the consequences of land-use change on soil microbial taxonomic and functional diversity.

Weed control, soil health, and yield tradeoffs of between-bed management strategies in organic plasticulture vegetable production

Planting a cover crop living mulch between plastic mulch beds in fresh market vegetable production can reduce soil erosion and runoff, and offers an opportunity to grow an income generating cash crop alongside a soil building cover crop. However, potential negative impacts on yield, variable weed control, unclear impacts on soil health, and limited management recommendations challenge adoption of this practice, despite grower interest. In a two-year study in southwest Michigan, living mulches were evaluated in the production of plasticulture organic summer squash (Cucurbita pepo cv. Lioness) and bell pepper (Capsicum annuum cv. Paladin). Strategies evaluated included three common grower practices (cultivation, dead straw mulch, mowing ambient weeds) and three mowed living mulch treatments (Italian ryegrass [Lolium multiflorum] monoculture, rye [Secale cereale] monoculture, and a Dutch white clover [Trifolium repens]/rye mixture). We determined the impact of these strategies on weed control, organic matter inputs, vegetable crop performance, nitrogen retention, and soil microbial communities. We found that cultivation and dead mulch provided superior in-season weed control, reducing weed biomass by an average of 86% compared to 18% among living mulch treatments, with associated reductions in the weed seedbank compared to living mulches and mowed weeds. In most cases, living mulch establishment was a challenge and weed biomass on average accounted for 99, 74, and 94% of organic matter inputs in rye, ryegrass, and clover/rye treatments, respectively. Squash performance was unaffected by our treatments, but pepper yield reductions ranged from 41 to 54% in all treatments relative to cultivation in one of two years. Living mulches and the weedy treatment showed the ability to reduce end-of-season potentially leachable nitrogen by 61% compared to cultivation and dead mulching. Soil microbial abundance and functional diversity were similar across treatments, but extracellular enzyme activity was higher in dead mulch, living mulch and weedy treatments compared to cultivation. Results from this study help quantify tradeoffs between common grower practices for managing weeds and soil between plastic mulch beds, highlight key challenges with living mulch alternatives, and identify areas for future research.

Soil microbial functional diversity is primarily affected by soil nitrogen, salinity and alkalinity in wetland ecosystem

Wetland ecosystems, recognized as important carbon sinks, face challenges due to climate change. Although wetland soil microorganisms play a major role in the wetland carbon cycle, the mechanisms influencing their spatial distribution remain elusive. Here, we investigate the impact of soil properties on the spatial distribution of soil microorganisms across five saline-alkali wetlands (Xianghai [XH], Niuxintaobao [NX], Momoge [MMG], Zhalong [ZL], and Halahai [HLH]) within the Songnen Plain, China. We utilized the Biolog-ECO method to assess the carbon metabolic activity, microbial diversity, and carbon source utilization preference of soil microorganisms. Using the structural equation model, we analyzed factors influencing microbial carbon metabolic activity and microbial diversity. Results indicate that southern wetlands harbor soil microbial communities exhibiting higher carbon metabolic activity, Shannon index, and substrate richness, compared to their northern counterparts. Specifically, soil microorganisms in NX and XH wetlands demonstrate a preference for labile organic carbon, whereas those in HLH and ZL wetlands preferred to use recalcitrant carbon. Furthermore, soil microbial carbon metabolic activity is primarily regulated by soil total nitrogen content, whereas soil microbial diversity is primarily regulated by soil salinity and alkalinity. Our findings revealed the distribution characteristics and influencing factors of soil microorganisms in the Songnen Plain wetland, contributing to understanding the maintenance mechanism of wetland carbon sink function.

Microbial response to Nature-Based Solutions in urban soils: A comprehensive analysis using Biolog® EcoPlates™

The study presents a comprehensive examination of changes in soil microbial functional diversity (hereafter called microbial activity) following the implementation of Nature-Based Solutions (NBS) in urban areas. Utilizing the Biolog® EcoPlates™ technique, the study explored variations in microbial diversity in urban soil under NBSs implementation across timespan of two years.Significant differences in microbial activity were observed between control location and those with NBS implementations, with seasonal variations playing a crucial role. NBS positively impacted soil microbial activity especially at two locations: infiltration basin and wild flower meadow showing the most substantial increase after NBS implementation. The study links rainfall levels to microbial functional diversity, highlighting the influence of climatic conditions on soil microbiome. The research investigates also the utilization of different carbon sources by soil microorganisms, shedding light on the specificity of substrate utilization across seasons and locations. The results demonstrate that NBSs implementations lead to changes in substrate utilization patterns, emphasizing the positive influence of NBS on soil microbial communities. Likewise, biodiversity indices, such as Shannon-Weaver diversity (H′), Shannon Evenness Index (E), and substrate richness index (S), exhibit significant variations in response to NBS. Notably, NBS implementation positively impacted H′ and E indexes, especially in infiltration basin and wild flower meadow, underlining the benefits of NBS for enhancing microbial diversity.The obtained results demonstrated valuable insight into the dynamic interactions between NBS implementation and soil microbial activity. The findings underscore the potential of NBS to positively influence soil microbial diversity in urban environments, contributing to urban sustainability and soil health. The study emphasizes the importance of monitoring soil microbial activity to assess the effectiveness of NBS interventions and guides sustainable urban development practices.

Soil Microbial Community Structure and Functional Diversity Character of Abandoned Farmland in Minqin Oasis

To clarify the impact of the structure and function of soil microbial communities in the stage of abandoned farmland, three different stages of land abandoned in desert oasis areas were selected as the research objects. We used metagenomic sequencing technology to research soil microbial community structure and functional diversity characteristics of different stages of abandoned farmland. The results showed that there were significant differences in the relative abundance of the dominant phyla Actinobacteria, Proteobacteria, and Gemmatimonadetes in the soil of the three stages of returning farmland. Compared with that in the early stage of abandoned farmland, the later stage of abandoned farmland restoration increased the gene proportion involved in Quorum sensing, porphyrin and chlorophyll metabolism, pantothenate and CoA biosynthesis, and styrene degradation, and there was a significant difference in relative abundance (P<0.05), which indicated that different stages of abandoned farmland had changed the functional potential of the nutrient cycle and energy metabolism in soil microbial communities. The RDA results showed that EC, AK, and TN had a significant impact on the functional composition of soil microbes, and soil EC had the greatest impact on microbial functional composition. The results showed that different stages of abandoned farmland had a significant impact on the soil microbial community structure and functional composition. In the ecological restoration of abandoned farmland in Minqin Oasis, the sensitivity of microbial community structure and functional composition to soil restoration at different stages should be considered using comprehensive relevant indicators.

Enhancing soil health and carbon sequestration through phytogenic treatment: insights into microbial functional pathways in pasture dieback affected soil

Abstract Background and aims Phytogenic bioactive plant products have shown promise in mitigating Australian pasture dieback (PDB) syndrome, a complex condition that adversely affects pasture productivity and sustainability. PDB is characterised by the progressive decline of grass, resulting in reduced soil organic matter. Recent studies have indicated that soil microbial communities play a crucial role in the remediation of affected pastures. In our previous research, the application of a phytogenic secondary metabolic product demonstrated a positive impact on soil microbial diversity, and it significantly increased pasture biomass. Building upon our previous study, we aimed to further investigate the mechanisms underlying pasture improvement through phytogenic treatment by spraying. Methods Here, we conducted a shotgun metagenomic investigation of the soil microbiome functional pathways affected by the phytogenic treatment. Results The application of phytogenic treatment to the PDB-affected soil resulted in a notable increase in soil microbial functional richness and diversity and showed alterations in beta diversity. Among the 65 significantly altered functional pathways, 54 showed an increase, while 11 decreased in response to the phytogenic treatment. The treatment altered the soil’s functional capacity towards increased production of biomolecules, including amino acids, lipids, and cofactors, thus enhancing the soil’s nutritional value. Furthermore, the phytogenic treatment significantly increased pathways involved in soil detoxification and carbon sequestration, suggesting its potential to promote soil health and carbon storage. Conclusion Our findings contribute to a better understanding of the mechanisms involved in improving the soils affected by pasture dieback. These insights will help develop sustainable strategies for pasture production.

Responses of soil bacterial functional group diversity to nitrogen enrichment in global grasslands

Soil microbial functional groups are closely linked to ecosystem functioning and are highly sensitive to global environmental changes. However, compared to the species diversity, how soil microbial functional group diversity responds to environmental changes remains poorly understood. Here, we investigated the nitrogen (N) effect on soil bacterial functional group diversity and predicted its spatial pattern in global grasslands. By re-analyzing publicly available 16S rRNA gene amplicon data from 38 N-addition experiments including 96 paired measurements across five continents, we found that N enrichment significantly leads to a more similar β-diversity but had no pronounced effect on α-diversity of soil bacterial functional groups. Global mapping with a random forest model revealed a clear spatial pattern of the N effect: ∼78 % of the global grasslands have shifted towards a more similar bacterial functional group β-diversity under contemporary N deposition rates, and in the regions particularly affected by high N deposition and vulnerable to global changes (e.g. the Eurasian steppe), the magnitude of change was greater. These results make a step in understanding soil microbial functional group diversity in addition to species diversity in the face of environmental changes, and provide more knowledge and rationale for the conservation of soil microbial functional diversity hotspots in global grasslands.

Effects of long-term drainage and afforestation on carbon utilization function of soil microbial communities vary between the types of subtropical moss peatlands

Subtropical moss peatlands are valuable delicate ecosystems that play crucial roles in biodiversity preservation, carbon sequestration, and water retention. However, driven by economic interests, a large area of subtropical moss peatlands in the Yunnan-Guizhou Plateau of China has been used for drainage and afforestation of a Cryptomeria japonica forest, leading to changes in the ecological functions of the peatlands. The Biolog EcoPlate™ method was used to study the differences in the carbon utilization functions of the soil microbial communities between a typical natural Sphagnum fen (SF), a natural Polytrichum bog (PB) and a Cryptomeria swamp forest that were formed by long-term drainage and afforestation (more than 20 years) in the region. Combined with measurements of the soil physicochemical properties, the effects of drainage and afforestation on different types of moss peatlands and the underlying mechanisms were explored. The results showed that long-term drainage and afforestation significantly increased the soil microbial carbon utilization activity and functional diversity in the SF, but no significant effects were observed in the PB. Drainage and afforestation did not significantly alter the proportion structures of the soil microbial carbon source utilization in the SF or PB but did significantly affect soil microbial preferences for specific carbon source utilization in the SF. Carbohydrates, amino acids, carboxylic acids and polymers were the main carbon sources utilized by the microbial communities in the three vegetation types. The soil volumetric water content (SVW) and available phosphorus (AP) content were significant factors affecting the functional characteristics of soil microbial carbon utilization. There was a significant negative correlation between the SVW and the activity of soil microbial carbon source utilization and functional diversity, and there was a significant positive correlation between the AP and polymer utilization activity. Moreover, the SVW significantly and indirectly affected overall carbon source utilization by influencing the utilization of carbohydrates. In the restoration of subtropical moss peatlands affected by drainage and afforestation, in addition to emphasizing vegetation restoration, the SF restoration should be focused on the restoration of water conditions, while the PB restoration should be focused on the restoration of nutrients (such as AP).

Seasonal changes of soil microbiota and its association with environmental factors in coal mining subsidence area

As a special type of wetland, the new wetland in the coal mining subsidence area is highly sensitive to environmental changes. In recent years, more and more attention has been paid to the studies of soil microbial diversity in newly born wetlands in coal mining subsidence areas. However, there are few reports on the seasonal variation of soil microbial diversity and its relationship with soil physical and chemical properties. In this study, 16S rRNA gene sequencing technology was used to analyze the seasonal changes of soil microbial composition and functional diversity in newly formed wetlands in coal mining subsidence areas, and to determine the seasonal changes of soil nutrient elements and physical and chemical properties in coal mining subsidence areas, so as to analyze the correlation between soil microbial diversity and soil nutrient elements and physical and chemical properties in newly formed wetlands in coal mining subsidence areas. A total of 16,050 OTUs were obtained after sample gene noise reduction. Proteobacteria, Acidobacteriota and Bacteroidota were the highest abundance in the coal mining subsidence area of Jining. The two seasons gathered separately, and temperature (Temp), total phosphorus (TP), available phosphorus (AP), total organic carbon (TOC) and dry matter content (DMC) were the key factors for the seasonal change of soil microbial community in the wetland of the coal mining subsidence area of Jining. The contents of Temp, AP and TP were significantly correlated with the abundance of soil microorganisms in summer subsidence area, while the contents of DMC and TOC were significantly correlated with the abundance of soil microorganisms in winter subsidence area. Soil microbial diversity in coal mining subsidence area was correlated with the seasons. Temp, TP, AP, TOC and DMC were the key factors for the seasonal change of soil microbial community in the wetland of the coal mining subsidence area of Jining.

The impact of smash-ridge tillage on agronomic traits of tobacco plants, soil enzymatic activity, microbial community structure, and functional diversity

ABSTRACT Smash-ridge tillage is a novel cultivation technique that significantly influences the quality of arable land and crop yield. In this study, we employed high-throughput 16S rRNA sequencing and Biolog-ECO methods to systematically investigate the impact of smash-ridge tillage on soil microbial community structure and functional diversity. The results demonstrate that both ST30 and ST50 treatments significantly enhance the average plant height, average plant diameter, average fresh root weight, stem fresh weight, and leaf area of tobacco plants, with the ST50 treatment exhibiting superior performance. Furthermore, both ST30 and ST50 treatments exhibit significantly higher soil enzyme activity and microbial community diversity compared to the CK treatment. They also improve the soil microbial utilization of carbon sources. Additionally, the ST50-treated soil samples demonstrate 15 microbial functional pathways that exceed those of the CK and ST30 treatments. In conclusion, the Smash-ridge tillage treatment at a depth of 50 cm yields more favorable results. This study provides a theoretical foundation for enhancing soil quality in Smash-ridge tillage by elucidating the mechanisms through which it impacts soil microbial ecology.

Deciphering the degradation characteristics of the fungicides imazalil and penflufen and their effects on soil bacterial community composition, assembly, and functional profiles

The adsorption-desorption and degradation characteristics of two widely applied fungicides, imazalil and penflufen, and the responses of soil bacterial diversity, structure, function, and interaction after long-term exposure were systemically studied in eight different soils. The adsorption ability of imazalil in soil was significantly higher than that of penflufen. Both imazalil and penflufen degraded slowly in most soils following the order: imazalil > penflufen, with soil pH, silt, and clay content being the potential major influencing factors. Both imazalil and penflufen obviously inhibited the soil microbial functional diversity, altered the soil bacterial community and decreased its diversity. Although exposure to low and high concentrations of imazalil and penflufen strengthened the interactions among the soil bacterial communities, the functional diversity of the co-occurrence network tended to be simple at high concentrations, especially in penflufen treatment. Both imazalil and penflufen markedly disturbed soil nitrogen cycling, especially penflufen seriously inhibited most nitrogen cycling processes, such as nitrogen fixation and nitrification. Meanwhile, sixteen and ten potential degradative bacteria of imazalil and penflufen, respectively, were found in soils, including Kaistobacter and Lysobacter. Collectively, the long-term application of imazalil and penflufen could cause residual accumulation in soils and subsequently result in serious negative effects on soil ecology.

Effects of Soil Microbiological Properties on the Fractional Distribution and Stability of Soil Organic Carbon under Different N Addition Treatments

Soil organic carbon (SOC) fractions are influenced by inputs of nitrogen (N) from globally rising N deposition; however, the mechanisms of how soil microbiological properties are influenced by N deposition and its impact on the fractional distribution and stability of SOC remain unclear. In this study, we assessed the effects on SOC fraction distribution and stability from four aspects of soil microbiological properties: soil microbial biomass (SMB), soil microbial activity, structure diversity, and functional diversity of soil microbial community in a Pinus tabuliformis plantation, which received four N addition levels (0 g N m−2 y−1 (N0), 3 g N m−2 y−1 (N3, low N addition), 6 g N m−2 y−1 (N6, mid-N addition), and 9 g N m−2 y−1 (N9, high N addition)) for 2 years. The N inputs did significantly affect some soil microbiological properties, like SMB, soil phospholipid fatty acid (PLFA), and soil microbial functional diversity. Mid- and high N addition decreased the richness (HPLFA) and evenness (EPLFA) index of the soil microbial community, from 3.24 to 2.91 and 0.93 to 0.87, respectively. In addition, the low N addition promoted the carbon management index (CMI) to 141.35, i.e., higher than the CMIs in the mid- and high-level treatments. The SOC stability also showed significant differences among N addition treatments, and SOC could be the most stable at the mid-N addition level. Regarding the effects of the four soil microbiological attributes on the CMI and stability, SMB and soil respiration positively impacted the CMI, but did not significantly affect the stability. In addition, EPLFA had positive effects, but EBIOLOG had negative effects on CMI and lability. Our findings indicate that soil microbiological properties are essential in SOC fractional distributions and stability. Further identification and study of soil microbial species used to change SOC fractions would help to clarify the detailed mechanisms involved.

Functional diversity and behavioral changes of microbial communities under salt affected soils

Salt-affected soils (SASs) are globally distributed especially in the arid and semi-arid regions of the world which highly affect the crop growth and productivity. The soil physico-chemical and biological properties largely vary with different types of SASs which trigger the crop yield, nutrient imbalance and soil quality. Therefore, to understand the changes in soil microbiology in relation to soil characteristics, a micro plot study was conducted to evaluate the impact of soil salinity/sodicity on physical, chemical properties at surface (0–15 cm) and subsurface (15–30 cm) soils in relation to soil microbial population, activities and functional diversity with focusing on community-level physiological profiling (CLPP) study. Five types of soils based on pH, electric conductivity (EC) and salt concentration maintained for last 25 years - highly saline, moderately saline, highly sodic, moderately sodic and normal were evaluated in micro plots to understand the changes in soil biological properties in relation to salt concentration. The results revealed that the highest value of pHs, ECe (EC of soil saturated paste extract), cation exchange capacity (CEC), exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), anions and cations concentrations, bulk density (BD), infiltration rate (IR), penetration resistance (PR) were observed in highly saline and highly sodic soils at surface and subsurface soil layer. In surface and subsurface layers, organic carbon (0.67 and 0.52 %) and available N (110 and 195 kg ha−1) were found higher under normal soils than SASs (% OC: 0.20–0.34 and 0.17–0.38; available N: 75–80 and 47–77 kg ha−1), respectively. In relation to changes in soil physicochemical properties, average well color development (AWCD) was found highest with normal soils followed by moderately saline and moderately sodic soils and lowest was found in highly sodic soils at surface soils which indicates interference of salts in metabolic activities of microbes. The utilization of amino acids, amines, carboxylic acids, phenolic compounds and polymers was highest for normal soils followed by moderately saline and lowest was recorded for highly sodic soils. But AWCD for carbohydrates was highest in highly saline soils, followed by highly sodic soils in contrast to normal soil and lowest was found under moderately sodic soils. Shannon diversity index (H) and substrate richness (SR) were found higher (3.19 and 24.07) in normal soils than SASs. Similarly, effect of salt load was also reflected on less soil enzymatic activities such as dehydrogenase, aryl sulfatase, invertase, etc. under varying types of SASs. Thus, with the increasing salt load, chemical and physical properties of soils were found to deteriorate and directly affected the microbial population, activities and their diversity in soil. This study indicated that soil physico-chemical properties, functional diversity, population and community of microbes were highly influenced by nature of salts and their concentration that may affect the soil quality and crop yield.

Effects of Pruning on Tea Tree Growth, Soil Enzyme Activity and Microbial Diversity

In order to investigate the effect of pruning on the soil environment in which tea trees grow and the growth of tea trees, this study used Wuyi Meizhan (Camellia sinensis) as a research object and measured its growth indexes, soil physicochemical indexes, soil enzyme activity and microbial functional diversity to analyze the effects of pruning treatments on the growth of tea trees, soil enzyme activity and soil microbial functional diversity and the correlation between them. The results of the analysis of tea tree growth indexes showed that the hundred-bud weight, leaf area and yield in the pruning treatment were significantly higher than those in the unpruned treatment. The results of soil physicochemical index analysis showed that pH, available phosphorus, available potassium and organic matter were significantly higher in the pruning treatment than in the unpruned treatment (p &lt; 0.05), while available nitrogen and total phosphorus were significantly lower than in unpruned treatment (p &lt; 0.05). The results of soil enzyme activities showed that only polyphenol oxidase and catalase activities were significantly higher in the pruning than in the unpruned treatment, while urease, protease, acid phosphatase, asparaginase and glutaminase activities were significantly lower than in the unpruned treatment (p &lt; 0.05). Biolog analysis showed that the utilization of microbial carbon sources, especially amino acid and amine, increased in the rhizosphere soil of the pruned tea tree, while there was a significant decrease (p &lt; 0.05) in microbial diversity. It is evident that pruning promoted tea tree growth and some enzyme activity, while inhibiting the activity of enzymes associated with the nitrogen cycle, and the utilization of microbial carbon sources increased, but their diversity decreased. This study provides a theoretical basis for the daily management of tea plantation after pruning.

Canopy Gaps Control Litter Decomposition and Nutrient Release in Subtropical Forests

The formation of a canopy gap results in changes to the microenvironment which, in turn, affect litter decomposition and nutrient release. However, the mechanisms underlying these effects in differently sized gaps and non-gaps remain poorly understood. To address this gap in knowledge, we selected three large gaps (above 150 m2), three medium gaps (50–100 m2), three small gaps (30–50 m2), and three non-gaps with basically the same site conditions. We then used the litter bag method to investigate leaf and branch litter decomposition over a year in a Castanopsis kawakamii natural forest with the aim of characterizing the litter mass remaining and the nutrient release in canopy gaps and non-gaps. Our results revealed that the remaining litter mass of leaf and branch litter was lower in medium gaps compared to other gaps, and leaf litter decomposed faster than branch litter. Environmental factors were identified as the primary drivers of total carbon and nitrogen release during litter decomposition. Gap size (canopy openness), taxonomic Margalef index, the Brillouin index of soil microbes, soil total nitrogen content, soil pH value, and average air temperature were identified as the main factors driving carbon and nitrogen release from branch litter. In the late decomposition stage, the taxonomic Pielou index, soil total potassium content, soil water content, and average relative air humidity were the main drivers of nutrient release from branch litter. The soil water content and average relative air humidity were also found to be the main factors affecting the nutrient release from leaf litter throughout the different stages of decomposition. Overall, our study highlights the impact of canopy gaps on microenvironmental variation, taxonomic community diversity, and soil microbial functional diversity and how these factors ultimately influence litter decomposition and nutrient release. Our findings provide an important foundation for further research into soil nutrient cycling in subtropical natural forests.

Effects of different fertilization treatments on soil microbial functional diversity of dry tableland wheat field in south Shanxi Province.

Understanding the effects of different fertilization treatments on microbial functional diversity in loess tableland wheat soil in south Shanxi Province can provide the theoretical basis from the perspective of microbial functional diversity for chemical fertilizer reduction, wheat yield increase, and soil fertility improvement in dryland soil. We conducted a long-term field experiment with seven fertilization treatments in winter wheat cultivation area of loess tableland in south Shanxi Province, including straw charcoal fertilizer (SF), bacterial fertilizer (BF), organic fertilizer (OF), humic acid fertilizer (HF), monitoring fertilizer (MF), farmer fertilizer (FF) and no fertilizer (CK). We employed Biolog-ECO microplate technique to investigate the differences of carbon source utilization capacity and functional diversity of soil microorganisms. The results showed that all the fertilization treatments could improve the metabolic activity and functional diversity of soil microbial community. Carbon source utilization was the most efficient in SF, with the overall soil microbial utilization ability of the 31 carbon sources and the utilization ability of different guilds of carbon sources being improved. Functional diversity, richness, and dominance based on microbial carbon sources utilization were significantly higher in SF treatment than that under other five treatments, and the evenness was higher than BF. Results of principal component analysis (PCA) and biclustering heatmap analysis showed that different fertilization treatments had significant effects on the metabolic function of microbial community. SF treatment could promote the functional diversity of soil microbial community, especially for the utilization of carbohydrates, carboxylic acids and amino acids. In conclusion, straw charcoal fertilizer had positive effects on soil microbial activity in wheat soil of loess tableland in south Shanxi Province.

Soil microbial and macroinvertebrate functional diversity in response to Zokor disturbance in Tibetan alpine meadow

Soils contain a remarkable diversity of organisms that are important regulators of ecosystem functions. However, the knowledge of how the environment shapes biodiversity patterns below ground remains limited in alpine areas of the Tibetan Plateau. Here, we conducted a microhabitat scale study (400 m2 plot) integrating data on soil and plant community characteristics to explore the driving forces of functional diversity of soil microbial and macroinvertebrate communities under disturbance by plateau zokor (Eospalax baileyi), a subterranean rodent inhabiting the Tibetan Plateau. The results show that plateau zokor disturbance led to a decline in the belowground biomass of grasses, whereupon the total belowground plant biomass and soil organic carbon decreased significantly. The functional diversity of soil microbial and macroinvertebrate communities was significantly increased under plateau zokor disturbance. Redundancy analysis indicated that soil moisture, temperature and compaction, in combination with plant species richness and belowground biomass of forb were the most important factors in driving soil microbial and macroinvertebrate functional diversity. Piecewise structural equation modeling (SEM) revealed that plateau zokor mound disturbance had positive effects on the functional diversity of soil microbial and macroinvertebrate communities by regulating soil physical properties (moisture, temperature, and compaction) and plant species richness within the habitat. Further, zokor disturbance affected the functional diversity of soil microbial and macroinvertebrate communities indirectly via regulating soil organic carbon. Our study provides evidence that the functional diversity of microbes is more driven by environmental changes than those of macroinvertebrates.

A sensitive soil biological indicator to changes in land-use in regions with Mediterranean climate

The demand for reliable indicators to quantify soil health has increased recently. We propose and test the use of soil microbial functional diversity as an indicator of multifunctional performance in agriculturally important areas. Agricultural fields in the Mediterranean and semiarid regions of Israel were selected as test sites and measured in Spring and Autumn seasons. Measurements included microbial parameters, basic soil abiotic properties and biological responses to agricultural management relative to measures of a natural ecosystem. Using a canonical correlation analysis we found that soil moisture was the most important basic soil property with different responses in Spring and Autumn. In Spring, it had a strongly negative relation with microbial biomass (MB), community level physiological profiling (CLPP) and the Shannon-Weaver index H', while in Autumn it had a strong relation with CLPP. We further show a significant interaction between CLPP and climate for land-use type "orchards". CLPP measured in the autumn season was thus identified as a useful and rapid biological soil health indicator, recommended for application in semiarid and Mediterranean agricultural regions. Apart from obtaining a better understanding of CLPP as the soil indicator, the study concludes that CLPP is well suited to differentiate between soils in different climates, seasons and land use types. The study shows a promising direction for further research on characterizing soil health under a larger variety of conditions.