•GRSP is more strongly related to SOC than other soil parameters or climate factors.•GRSP content is greater in conifer forest topsoils than broadleaf topsoils.•SOC is enriched in GRSP in very acid ...soils (<4.0), possibly indicating a fungal role.•Vertical distributions of GRSP and SOC follow different exponential declines.
Soil organic matter (SOM) is of critical importance to the functioning of ecosystems because of its effects on soil nutritional quality, microbial activity and soil structure. SOM is made up of a variety of compounds ranging from chemically reactive and mobile forms to stable, recalcitrant forms. An operationally defined fraction of soil organic matter known as glomalin-related soil protein (GRSP) is thought to be of fungal origin, very stable and responsible for increased physical stability of soil. To date, the origin of this fraction of SOM and the factors controlling its accumulation in soils are not well understood. The aim of this study was to contribute to the understanding of the origin of this fraction and the factors which contribute to its accumulation in the soil. This study was carried out on archived soils from 102 sites of the long-term monitoring network for forest ecosystems in France (RENECOFOR), from depths up to 1 m. The effects of tree type, climate and soil properties on the accumulation and vertical distribution of GRSP were assessed. GRSP was greater under conifer forests than broadleaf forests. GRSP in the top soil layer was positively correlated with both SOC and total nitrogen, and inversely related with pH, with the strongest effect observed at very acid (pH ≤ 4.0). Both GRSP and SOC were found to follow exponential declines with depth. The contrast in vertical distribution of GRSP and SOC supports the hypothesis that GRSP is a distinct fraction of SOM. Climate and soil properties had significant influence on the vertical distribution of GRSP. The accumulation of GRSP, and the enrichment of SOC in GRSP, at acid pH could indicate a fungal origin of GRSP.
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•Arbuscular mycorrhizal fungi (AM fungi) directly or indirectly alleviate heavy metal in host plant.•AM fungi improve nutrient uptake, plant biomass and antioxidants under heavy metal ...stress in the host plant.•AM fungi remediate heavy metal by accumulating large part of heavy metals in fungal structures.
The heavy metal pollution is a worldwide problem and has received a serious concern for the ecosystem and human health. In the last decade, remediation of the agricultural polluted soil has attracted great attention. Phytoremediation is one of the technologies that effectively alleviate heavy metal toxicity, however, this technique is limited to many factors contributing to low plant growth rate and nature of metal toxicities. Arbuscular mycorrhizal fungi (AMF) assisted alleviation of heavy metal phytotoxicity is a cost-effective and environment-friendly strategy. AMF have a symbiotic relationship with the host plant. The bidirectional exchange of resources is a hallmark and also a functional necessity in mycorrhizal symbiosis. During the last few years, a significant progress in both physiological and molecular mechanisms regarding roles of AMF in the alleviation of heavy metals (HMs) toxicities in plants, acquisition of nutrients, and improving plant performance under toxic conditions of HMs has been well studied. This review summarized the current knowledge regarding AMF assisted remediation of heavy metals and some of the strategies used by mycorrhizal fungi to cope with stressful environments. Moreover, this review provides the information of both molecular and physiological responses of mycorrhizal plants as well as AMF to heavy metal stress which could be helpful for exploring new insight into the mechanisms of HMs remediation by utilizing AMF.
Arbuscular mycorrhizal fungi (AMF) produce glomalin-related soil protein (GRSP) that influences organic carbon (C) storage in soil; however, how much purified GRSP fractions contribute to soil ...organic carbon (SOC) is yet not known. The present study evaluated the contribution of GRSP towards changes in SOC in trifoliate orange grown in a rootbox divided into a roots + hyphae chamber (roots colonized by AMF hyphae and AMF extraradical hyphae) and a hyphae chamber (only the presence of AMF extraradical hyphae, without roots). Three AMF species (Diversispora epigaea, Paraglomus occultum and Rhizoglomus intraradices) were inoculated into the roots + hyphae chamber. Following four months of plant growth, P. occultum showed higher AMF hyphal growth in roots, soils and nylon mesh than D. epigaea or R. intraradices. Mycorrhizal inoculation improved the plant growth performance and increased easily extractable GRSP (EE-GRSP) and difficultly extractable GRSP (DE-GRSP) concentrations in both chambers, regardless of AMF species. The C content observed in total GRSP of the soil after purification was 2.71 ± 0.49 mg g−1, while purified EE-GRSP and DE-GRSP showed the C content of 1.01 ± 0.19 mg g−1 and 1.70 ± 010.34 mg g−1, respectively. The C contribution by purified EE-GRSP and DE-GRSP accounted for 8.67 ± 0.95% and 14.59 ± 2.21%, respectively, of total SOC, with a total C contribution of purified GRSPs accounting for 23.26 ± 2.67% of total SOC. A significantly higher C content of GRSP and the C contribution of GRSP to SOC were observed in DE-GRSP than in EE-GRSP, as well as the soil of the roots + hyphae chamber than the soil of the hyphae chamber. The proportionate distribution of water-stable aggregate in 2–4 and 1–2 mm sizes and their stability were higher under AMF hyphae than under non-AMF hyphae. This study thus provided a database evidence of increased contribution of GRSP towards build-up of SOC in response to mycorrhizal symbiosis.
•GRSP contribution to SOC in trifoliate orange was studied.•The C content of EE-GRSP and DE-GRSP was 1.01 ± 0.19 mg g-1 and 1.70 ± 0.34 mg g.•C contribution of total GRSPs achieved 23.26 ± 2.67% of total SOC.•C content of GRSP and C contribution of GRSP to SOC were higher in DE-GRSP than in EE-GRSP.
Microbial metabolic products play a vital role in maintaining ecosystem multifunctionality, such as soil physical structure and soil organic carbon (SOC) preservation. Afforestation is an effective ...strategy to restore degraded land. Glomalin‐related soil proteins (GRSP) and amino sugars are regarded as stable microbial‐derived C, and their distribution within soil aggregates affects soil structure stability and SOC sequestration. However, the information about how afforestation affects the microbial contribution to SOC pools within aggregates is poorly understood. We assessed the accumulation and contribution of GRSP and amino sugars within soil aggregates along a restoration chronosequence (Bare land, Eucalyptus exserta plantation, native species mixed forest, and native forest) in tropical coastal terraces. Amino sugars and GRSP concentrations increased, whereas their contributions to the SOC pool decreased along the restoration chronosequence. Although microaggregates harbored greater microbial abundances, amino sugars and GRSP concentrations were not significantly affected by aggregate sizes. Interestingly, the contributions of amino sugars and GRSP to SOC pools decreased with decreasing aggregate size which might be associated with increased accumulation of plant‐derived C. However, the relative change rate of GRSP was consistently greater in all restoration chronosequences than that of amino sugars. The accumulation of GRSP and amino sugars in SOC pools was closely associated with the dynamics of soil fertility and the microbial community. Our findings suggest that GRSP accumulates faster and contributes more to SOC pools during restoration than amino sugars did which was greatly affected by aggregate sizes. Afforestation substantially enhanced soil quality with native forest comprising species sequestering more SOC than the monoculture plantation did. Such information is invaluable for improving our mechanistic understanding of microbial control over SOC preservation during degraded ecosystem restoration. Our findings also show that plantations using arbuscular mycorrhizal plants can be an effective practice to sequester more soil carbon during restoration.
Afforestation of bare land greatly enhanced the accumulation of glomalin‐related soil proteins (GRSP) and amino sugars, but it decreased their contribution to soil organic carbon (SOC). The faster accumulation and greater contribution of GRSP to SOC compared with those of amino sugars highlight the important role of arbuscular mycorrhizal fungi in mediating soil C cycling during forest restoration, despite the proportional contribution of GRSP and amino sugars to the SOC pool diminishing with forest restoration.
Glycoproteins, e.g., glomalin related soil proteins (GRSP), are sticky organic substances produced by arbuscular mycorrhizal fungi (AMF). This review summarizes the information on i) the biochemical ...nature, physical state and origin of GRSP, ii) GRSP decomposition and residence time in soil, iii) GRSP functions, in particular the physical, chemical, and biochemical roles for soil aggregation and carbon (C) sequestration, and finally iv) how land use and agricultural management affect GRSP production and subsequently, organic C sequestration. GRSP augment soil quality by increasing water holding capacity, nutrient storage and availability, microbial and enzymatic activities, and microbial production of extracellular polysaccharides. After release into the soil, GRSP become prone to microbial decomposition due to stabilization with organic matter and sesquioxides, and thereby increasing the residence time between 6 and 42 years.
Temperate soils contain 2-15 mg GRSP g-1, whereas arid and semiarid grasslands amount for 0.87-1.7 mg g-1, and GRSP are lower in desert soils. GRSP content is highest in acidic soils as compared to neutral and calcareous soils. Conservation tillage, organic fertilizers and AMF inhabiting crops (e.g. maize, sorghum, soybean, and wheat) increase GRSP production and transform C into stable forms, thereby sustaining soil health and reducing CO2 emissions. Crop rotations with non-mycorrhizal species (e.g. rapeseed) and fallow soils reduce AMF growth and consequently, the GRSP production. The GRSP production increases under nutrient and water deficiency, soil warming and elevated CO2. In the context of global climate change, increased C sequestration through GRSP induced aggregate formation and organic matter stabilization prolong the mean residence time of soil C. Protecting soils against degradation under intensive land use, stable aggregate formation, and prolonging the residence time of C calls for strategies that maximize GRSP production and functions based on reduced tillage, AMF-relevant crop rotations and organic farming.
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•Glomalin related soil proteins (GRSP) increase C sequestration mainly indirectly.•GRSP increase aggregate size and stability enhance AMF survival, protect hyphae.•AMF host plants and organic fertilizers increase glycoprotein production.•Tillage disrupts the AMF hyphal network and thus reduces GRSP production.•GRSP are key indicators of soil quality and good agricultural management practices.
Manure application is widely recognized as a method of improving soil structure and soil fertility due to additional organic matter and nutrient inputs. However, the salinity of animal manure may ...have a detrimental effect on soil aggregation. The objective of this study was to determine the effects of long-term animal manure application on soil aggregation, binding agents (soil organic carbon, SOC and glomalin-related soil protein, GRSP), and dispersing agents (e.g., Na+) and their relationships based on nine long-term fertilization experiments (12 to 39 yr) across China. The two red soil experiments (Qiyang, QY and Jinxian, JX) and one paddy soil experiment in Jinxian (JX-P) were conducted in southern China (precipitation above 1200 mm yr−1), whereas the other six experiments were established in semi-humid or arid regions in China with precipitation in the range of 500–900 mm yr−1. Each experiment included three treatments as follows: no fertilization (Control), inorganic fertilizer (NP or NPK), and a combination of inorganic fertilizer and animal manure (NPM or NPKM). Long-term animal manure application not only significantly increased the biological binding agents (i.e., SOC and GRSP) in the nine experiments but also considerably increased the dispersing agents (i.e., exchangeable Na+) (P < 0.05), except for the paddy soil experiment. Consequently, soil aggregate stability increased after animal manure application in three experimental sites in southern China but not in the experimental sites in northern China. Aggregate stability had a positive relationship with SOC and GRSP in the experimental sites in southern China (P < 0.01) but a negative relationship with exchangeable Na+ in the experimental sites in northern China (P < 0.05). The Na+ accumulation in soils was negatively related to mean annual precipitation (P < 0.001). Our study demonstrates that the long-term application of animal manure may degrade soil structure via the Na+ accumulation.
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•Animal manure improved soil aggregation in southern China but not in northern China.•Animal manure degrades soil structure due to Na+ accumulation in dry regions.•The Na+ accumulation in soils was negatively related to mean annual precipitation.
Mycorrhizas and Soil Structure Rillig, Matthias C.; Mummey, Daniel L.
The New phytologist,
July 2006, Letnik:
171, Številka:
1
Journal Article
Recenzirano
In addition to their well-recognized roles in plant nutrition and communities, mycorrhizas can influence the key ecosystem process of soil aggregation. Here we review the contribution of mycorrhizas, ...mostly focused on arbuscular mycorrhizal fungi (AMF), to soil structure at various hierarchical levels: plant community; individual root; and the soil mycelium. There are a suite of mechanisms by which mycorrhizal fungi can influence soil aggregation at each of these various scales. By extension of these mechanisms to the question of fungal diversity, it is recognized that different species or communities of fungi can promote soil aggregation to different degrees. We argue that soil aggregation should be included in a more complete 'multifunctional' perspective of mycorrhizal ecology, and that in-depth understanding of mycorrhizas/soil process relationships will require analyses emphasizing feedbacks between soil structure and mycorrhizas, rather than a unidirectional approach simply addressing mycorrhizal effects on soils. We finish the discussion by highlighting new tools, developments and foci that will probably be crucial in further understanding mycorrhizal contributions to soil structure.
Grazing prohibition is an effective measure in improving soil stability and ecological quality. However, only a limited number of studies have been published on the dominant factors that impact soil ...aggregate stability and their associated effects on nutrient distribution for different size soil aggregates under long-term grazing prohibition management. In this study, we investigated variation in soil aggregate stability and nutrient distribution characteristics in semiarid grassland sites under different grazing prohibition timeframes (0 years GP0, 11 years GP11, 26 years GP26, and 36 years GP36). Results showed that organic carbon (C) and total nitrogen (TN) concentrations in soil aggregates decreased at GP11 before progressively increasing and reaching its highest value at GP36, and the total phosphorus (TP) concentration did not change significantly. Most nutrients accumulated in macroaggregates (> 0.25 mm) under grazing prohibition, and the nutrient stoichiometry in soil aggregates increased after 26 years. Compared to the control (GP0), the mean weight diameter (MWD) value of the soil stability index increased at GP11 (21.7%) and decreased at GP26 (18.9%). Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) also showed that the proportion of stable organic C-related functional groups (i.e., alkene-C and aromatic-C) in macroaggregates were higher at GP11 and GP36 than at GP26. Furthermore, principal component analysis (PCA), partial least squares path modeling (PLS-PM), and the relative importance of regressors all showed that glomalin-related soil proteins (GRSP) and nutrients indirectly improved aggregate stability in semiarid grassland through their influence on the GRSP accumulation potential and nutrient stoichiometry. Generally, after 26 years grazing prohibition had a positive effect on soil aggregate stability and nutrient accumulation in the semiarid grassland sites investigated for this study. Results from this study provide a theoretical basis to select appropriate grazing prohibition timeframes under grassland management initiatives to optimize ecological quality measures in semiarid regions.
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•Soil aggregates have more nutrients after 26 years grazing prohibition.•Soil aggregates' stability index MWD showed an order of 11 > 36 > 26 years.•GRSP potential and nutrient stoichiometry are the main factors controlling MWD.•High aggregate stability of semi-arid grasslands has more alkene-C and aromatic-C.•Grazing prohibition after 26 years favors the ecological quality of the grassland.
Soil aggregates are critical to soil functionality, but there remain many uncertainties with respect to the role of biotic factors in forming aggregates. Understanding the interacting effects of ...soil, land use type, vegetation and microbial communities is a major challenge that needs assessment in both field and controlled laboratory conditions, as well as in bulk and rhizosphere soils. To address these effects and their feedbacks, we first examined the influence of soil, root and litter characteristics along a land use gradient (ancient woodland, secondary woodland, grassland, pasture and arable land) on microbial community structure (in both bulk and rhizosphere soil), as well as on aggregate stability. Then, we performed an inoculation experiment where we extracted soil columns from the arable and secondary woodland and used a third unstructured loamy soil as a control. We sterilized these three soils to remove microbial communities, and then inoculated the tops of sterilized soil columns with soil from the secondary woodland or the arable field sites. Control columns of all soil types were not inoculated. In a fully-crossed design, we planted two species possessing distinct root system morphologies: Brachypodium sylvaticum (fibrous system with many thin and fine roots) and Urtica dioica (taproot system with few fine roots). After four months, microbial communities (in bulk and rhizospheric soil) and aggregate stability were measured, along with root traits. In both the field and laboratory experiments, bacterial (16S) and fungal (ITS) diversity was determined using high throughput sequencing. In the field study we found that: i) there were strong relationships between aggregate stability and microbial community composition that were driven by land use, ii) the relationship between aggregate stability along the land use gradient and the trophic nature of bacterial communities was not significant, but certain soil, root and litter parameters shaped bacterial phyla, with oligotrophic bacteria conditioned by the rhizosphere niche, and copiotrophic phyla more dependent on bulk soil conditions, iii) land use gradient (from woodland to arable), reduced the relative abundance of saprotrophic and ectomycorrhizal fungi with an increase in the relative abundance of Ascomycota and a reduction in the relative abundance of Basidiomycota. In the laboratory experiment we found that: i) the inoculation of sterilized soils with soils from the field significantly increased aggregate stability in control soil that was initially poorly structured, ii) the effects of inoculation on aggregate stability were similar when either secondary woodland or arable soils were used as inoculums and iii) these effects were impacted significantly by root length density. Our results show that microbial communities influence soil structure and that bacterial communities are intimately associated to rhizospheric conditions and root traits (of which root length density was the most pertinent).
•Complex relationships between soil, land use and plant traits shape microbial communities.•Strong relationships exist between microbial communities and soil aggregate stability.•Bacterial trophic modes were related to bulk soil and rhizosphere niche differentiation.•Microbial inoculation with communities from intact soils affected aggregate stability.•The effect of microbial inoculation was modulated by root length density.
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