Changes in soil aggregation and glomalin

A soil constituent known as glomalin provides a secure vault for the world's soil carbon. Glomalin is a sticky substance secreted by threadlike fungal structures called hyphae that funnel nutrients and water to plant roots. Glomalin acts like little globs of chewing gum on strings or strands of plant roots and the fungal hyphae. The sand, silt and clay stick to the glomalin, starting aggregate formation, a major step in soil creation.

On the surface of soil aggregates, glomalin forms a lattice-like waxy coating to keep water from flowing rapidly into the aggregate and washing away everything, including the carbon. Nichols uses glomalin measurements to gauge which farming or rangeland practices work best for storing carbon. Since glomalin levels can reflect how much carbon each practice is storing, they could be used in conjunction with carbon credit trading programs.

In studies on cropland, Nichols has found that both tilling and leaving land idle—as is common in arid regions—lower glomalin levels by destroying living hyphal fungal networks. The networks need live roots and do better in undisturbed soil. When glomalin binds with iron or other heavy metals, it can keep carbon from decomposing for up to years. Even without heavy metals, glomalin stores carbon in the inner recesses of soil particles where only slow-acting microbes live.

This carbon in organic matter is also saved, like a slow-release fertilizer, for later use by plants and hyphae. Nichols began her career with ARS working with soil scientist Sara Wright, who first discovered and named glomalin in Wright has since retired. Note: Content may be edited for style and length. Science News. Nichols presented these research results June 17 at a public field day in Brookings, S.

ScienceDaily, 2 July Retrieved October 10, from www. In contrast, the Corn Belt of the U. By measuring Researchers now have shown, however,In a recent column about the benefits of organically farmed soil I mentioned that soils with higher carbon stored more moisture. The mechanism for this interaction is glomalin, a sugar protein that was only identified and named in Studies by US researcher Kristine Nicols have found that glomalin levels were higher in soils under native grasses than soils under introduced species, and that shifting cattle before they over-grazed an area helped to raise soil glomalin levels.

Her cropping study found that cultivation and fallowing lowered glomalin levels because cultivation destroyed the hyphae, and fallowing starved them. Glomalin is produced by mycorrhizal fungi that live inside plant roots and extend hairlike filaments or hyphae into the surrounding soil to obtain more nutrients. Together, the hyphae and glomalin form a sticky net that traps particles of sand, silt, clay and organic matter and holds them together to form lumps or aggregates of soil.

On the surface of these lumps or aggregates, the glomalin forms a waxy coating to stop water pouring into the aggregate and breaking it up. Aggregates are important in soils because they allow water infiltration, hold water for plant use, and provide organic carbon for soil organisms to feed on.

At the same time, the aggregates also store carbon deep inside the aggregate that microbes cannot access. It coats the fungal hyphae to protect them from decomposition and microbial attack and to ensure that water and nutrients reach the plant.

Scientists are now thinking that glomalin also helps hyphae stay rigid enough to extend into the soil and span the air spaces between soil particles. We are updating the DPI website as part of our commitment to deliver high quality information to our customers.

If you encounter problems using our website, you can report them. Glomalin is the soil's super glue. The sticky glomalin proteins sit on the hyphae like small gobs of chewing gum.

Glomalin has other benefits as well. So how do you know how much glomalin is in your soil? Basically, the more you have, the better your soil texture and structure.Glomalin-related soil protein GRSP contributes to the formation and maintenance of soil aggregates, it is however remains unclear whether long-term intensive manure amendments alter soil aggregates stability and whether GRSP regulates these changes.

The regulatory process of GRSP allocations in soil aggregates has important implications for manure management under intensive agriculture. Glomalin is a glycoproteinaceous substance that is produced by arbuscular mycorrhizal fungi AMF 12. Glomalin is usually quantified in soils as glomalin-related soil protein GRSP 2345which is a component of the hyphal walls of AMF and is likely released into the soil after death 6 ; thus, GRSP subsequently contributes to the linkage between soil particles and the stabilization of aggregates.

Positive correlations between the GRSP concentration and the amount of water-stable aggregates have been documented 237. In addition, glomalin is relatively recalcitrant and has a long residence time in the soil to contribute to stable carbon storage 89 ; microbial-derived carbon inputs to soils are being recognized as increasingly important in the long-term storage of carbon and nitrogen Despite recalcitrant features, GRSP can be sensitive to various agricultural management practices, such as tillage 11121314cropping treatments 1115and land use change 1617 Chemical and organic fertilizations are common practices and play a key role in maintaining long-term agricultural production; however, the effects of different types of fertilization on the changes in glomalin concentrations have received very limited attention.

For example, long-term fertilization, especially amendments with manure and straw, increase soil GRSP accumulation 19 However, the effects of different amounts of manure and mineral fertilizer and their interactions on GRSP dynamics have not been elucidated.

Aggregates are composed of primary mineral particles and organic binding agents Therein, arbuscular mycorrhizal fungi produce large amounts of insoluble glycoprotein, glomalin and polysaccharides, which contribute to aggregate stability 24.

These results collectively suggest a possible strong correlation of glomalin with aggregate stability 2. However, the underlying mechanism of this tight association between GRSP and aggregate stabilization remains poorly investigated. Furthermore, understanding factors controlling GRSP production such as fungal community composition, fungal physiology, and cell biology aspects as well as soil biota, soil physicochemical characteristics, and fungus—host plant species combinations will elucidate soil aggregation in crop production systems Long-term experiments provide a realistic and effective means for obtaining valuable information that is required to maintain the soil quality and health by determining changes in the soil properties and processes 24 Soil fertility degradation has long been a major concern in China due to the replacement of organic fertilizers by chemical fertilizers One of these experiments was set up in a brown soil region located in Liaohe Plain to explore the effect of long-term fertilization on the soil properties and crop yield Soil aggregate formation and stability are key variables for investigation; however, the role of GRSP on soil aggregates during long-term fertilization experiments has received little attention in this carbon-rich and high-productivity agricultural region, which hindered our understandings of how management practices alter GRSP concentrations in soil aggregates and how to maintain soil aggregate stability, fertility and productivity under different fertilization practices.

The objectives of this study were to examine the effects of the long-term application of mineral and organic fertilizers alone or in combination on the concentration and allocation of GRSP in different aggregate classes. This study is expected to clarify on the relationship between GRSP in different soil aggregate sizes and aggregate stability for the sake of optimal management practices in this region. The small macroaggregate comprised the largest proportion of the soil Different fertilization regimes altered the aggregate percentages in the soil.

High amounts of organic manure input M2, M2NPK tended to diminish the proportion of large macroaggregate compared to the other treatments. The abbreviations of fertilization treatments are the same as presented in Table 1.

Generally, the combined application of organic manure and fertilizer increased the proportions of small macroaggregate and decreased the proportions of microaggregate in the soil 28 In our study, changes in the proportions of soil aggregates varied with different fertilization treatments.

For instance, NPK treatment decreased the proportion of small macroaggregates, but manure or manure plus chemical fertilizers increased the same size aggregate. In contrast, NPK increased the proportion of microaggregates, but manure or manure plus chemical fertilizers decreased the same size aggregate.

As a measure of aggregate stability, mean weight diameter MWD has been used to assess manure amendments on soil aggregate stability.

changes in soil aggregation and glomalin

This contradiction may be due to the accumulation of large macroaggregates that were derived from different sources of manure materials. In this study, a very high amount of manure amendment provided POC 31which coated macroaggregates. Long-term manure applications with a large amount of organic input increased the macroaggregate dispersion and thus resulted in a decrease in aggregate stability In addition, there is unclear relationships between aggregate stability and rates of organic input by analyzing the literatures due to different factors such as the quality, quantity and timing of organic matter addition Glomalin-related soil protein GRSP is known as an important microbial by-product which is crucial for preserving or accumulating soil organic carbon SOC.

However, the underlying mechanisms are not well understood. The three forests, including a planted forest PFa secondary forest MF and a primary forest BFwere selected to represent the natural successional process after disturbance in southern China. Results showed that the average concentrations of GRSP were 3.

changes in soil aggregation and glomalin

This study demonstrated that the stubborn structure of GRSP probably regulate the resistance of SOC sequestration in tropical forests, especially in the planted and secondary forests. Plants allocate a considerable amount of carbohydrates to arbuscular mycorrhizae AM 3 for exchanging available phosphorus P and nitrogen N 45. Fungi- and other microbe-derived C remained in the soil longer than plant-derived C does 7.

Most of these conclusions were based on short-term laboratory experiments under abrupt environmental change scenarios, such as atmospheric CO 2 enrichment and N addition 810 For instance, AMF increased organic C decomposition by receiving N that was required by the rapid plant growth under elevated CO 2 treatment conditions Notably, soil C dynamics in forest ecosystems had exhibited little fluctuations over time. Therefore, the short-term AMF-mediated increase in C losses may be offset by a long-term C gain in recalcitrant compounds Most reports on how AMF facilitate SOC accumulation have considered that the external mycelia and its production of glycoprotein, glomalin-related soil protein GRSPcan promote the formation of soil aggregations 17 — Intensive studies have focused on the role of the external mycelia 2021 and soil aggregation 2223 in SOC sequestration.

Studies have found that GRSP represents a considerable amount ca. Although the composition of this glycoprotein was still unclear, Schindler et al. Three forest types were chosen along a successional trajectory, including a planted forest pine forest, PFa secondary forest mixed pine and broadleaf forest, MFand a primary forest monsoon evergreen broadleaf forest, BF.

It was also found higher proportion of C allocated to belowground in the BF compared to the PF when the net primary productivity NPP was comparable in these two forests Overall, the mean GRSP contents were 3. Mean values derived from 7 replications are presented with standard deviations. Abbreviations: BF, the primary monsoon evergreen broadleaf forest; MF, the secondary mixed pine and broadleaf forest; PF, the planted pine forest.

We detected the C concentrations in GRSP for all the 42 samples collected from these tropical forests. The soil microbial biomass C accounted for 1.Soil aggregation and soil structure are fundamental properties of natural and managed ecosystems. However, most of our knowledge on the role of plant species in soil aggregation is derived from work in agroecosystems or with agriculturally important plants. Here we examined the effects of five plant species on soil aggregate water stability.

The five species three grasses, one forb, and a legume were from the same natural grassland, and were grown in monoculture plots in the field. Our first goal was to test if productivity-related or species-specific factors would prevail in determining soil aggregation. We also tested what the relative importance of the soil protein glomalin produced by arbuscular mycorrhizal fungi, AMF in soil aggregation is, compared to other factors, including AMF hyphal and root length and percent plant cover.

We found significant differences in soil aggregate water stability 1—2 mm size class for the five plant species examined, and corresponding differences in plant cover, root weight and length, AMF soil hyphal length, and glomalin concentrations. A structural equation modeling approach path analysis was used to distinguish direct from indirect effects of factors on soil aggregation based on covariance structures.

Root length, soil glomalin, and percent cover contributed equally strong paths to water-stable aggregation. The direct effect of glomalin was much stronger than the direct effect of AMF hyphae themselves, suggesting that this protein is involved in a very important hypha-mediated mechanism of soil aggregate stabilization, at least for the 1—2-mm size class of aggregates. This is a preview of subscription content, log in to check access. Rent this article via DeepDyve. Google Scholar. Biogeochemistry 42, 44— Degens B P, Sparling G P and Abbott L K The contribution from hyphae, roots, and organic carbon constituents to the aggregation of a sandy loam under long-term clover-based and grass pastures.

Soil Sci. Degens B P Macro-aggregation of soils by biological bonding and binding mechanisms and the factors affecting these: A review.

Glomalin is the soil's super glue

Soil Res. Mycological Res. Haynes R J and Beare M H Influence of six crop species on aggregate stability and some labile organic matter fractions. Soil Biol Biochem. Spread of hyphae and phosphorus inflow into roots. New Phytologist— Jastrow J D Changes in soil aggregation associated with tallgrass prairie restoration. Jastrow J D and Miller R M Soil aggregate stabilization and carbon sequestration: feedbacks through organomineral associations. Klute A. Klironomos J N and Kendrick B Palatability of microfungi to soil arthropods in relation to the functioning of arbuscular mycorrhizae.

Soils 21, 43— Soil Biol. Miller R M, Reinhardt D R and Jastrow J External hyphal production of vesicular-arbuscular mycorrhizal fungi in pasture and tallgrass prairie communities.Glomalin is a soil proteinaceous substance produced by arbuscular mycorrhizal fungi.

Most of the information available concerning this protein has been collected in relation to its role in soil aggregation. In this study, we explored the distribution of glomalin across soil horizons, decomposition of glomalin, and relationship with soil C and N in an agricultural field, a native forest, and an afforested system.

Glomalin was present in A, B, and C horizons in decreasing concentrations. As measured after a day laboratory soil incubation, glomalin was least persistent in the A horizon of the afforested area. In agricultural soils and native soils, ca.

Soil Structure: A natural defense against soil compaction (2nd in series)

Comparison of glomalin decomposition with CO 2 -C respired during incubation indicates that glomalin makes a large contribution to active soil organic C pools. Soil C and N were highly correlated with glomalin across all soils and within each land-use type, indicating that glomalin may be under similar controls as soil C.

Czech Academy of Agricultural Sciences

Our results show that glomalin may be useful as an indicator of land-use change effects on deciduous forest soils. This is a preview of subscription content, log in to check access.

Rent this article via DeepDyve. Forest Ecol. Google Scholar. Soil Sci. Plant and Soil— USA 10, — In Assessment Methods for Soil Carbon. Determination of the controls on C and N dynamics in afforested agricultural soils. Special Issue. In review. Academic Press, San Diego. Oikos 97, 52— Rillig M C, Wright S F and Eviner V b The role of arbuscular mycorrhizal fungi and glomalin in soil aggregation: comparing effects of five plant species.

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changes in soil aggregation and glomalin

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