Glomalin-related Soil Protein Production Research Articles

Unraveling the impact of global change on glomalin and implications for soil carbon storage in terrestrial ecosystems

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.

Spatial change in glomalin-related soil protein and its relationships with soil enzyme activities and microbial community structures during urbanization in Nanchang, China

Rapid urbanization brings about drastic changes in land use and soil quality. Glomalin-related soil protein (GRSP), a sensitive indicator of soil quality, is possibly secreted by arbuscular mycorrhizal fungi (AMF). Besides, soil microorganisms and enzymatic activities play an irreplaceable role in improving soil quality and regulating soil nutrient circulation. However, little data are available on the interactions between GRSP, microorganisms, and enzymatic activities during urbanization. Here, we selected a built-up area (505 km2) in Nanchang, China, and collected soil samples from 184 sites from different urbanized areas. Soil microorganisms, soil physicochemical properties, soil enzymatic activities, vegetation characteristics, and land-use configurations were used to decouple the variations in total GRSP (TG) and easily extractable GRSP (EEG) during urbanization. Results showed that TG and EEG contents significantly decreased by 16.2 % and 19.4 % from low to heavy urbanization areas, respectively. Moreover, N-acetylglucosamine glycosidase (NAG), acid phosphatase (AP), and leucine aminopeptidase (LAP) activities, and the biomass of gram-positive bacteria (G+) and actinomycetes were significantly larger in lightly urbanized than in heavily urbanized areas (p < 0.05). EEG and TG positively correlated with β-1,4-glucosidase (BG), NAG, LAP, AP, G+, gram-negative bacteria, actinomycetes, and total soil microbial biomass (p < 0.05). Variance partitioning analysis showed that soil enzymatic activities are pivotal in GRSP production. However, no direct evidence shows that AMF secrete GRSP. Furthermore, structural equation modeling found that urbanization could diminish soil enzymatic activities by reducing vegetation cover and increasing the proportion of impervious surface area, indirectly causing a decrease in GRSP content. In conclusion, urbanization could indirectly reduce GRSP content by affecting land-use configurations and soil enzymatic activities. In the future, we shall consider improving soil quality by increasing GRSP content during urbanization.

Extraradical Mycorrhizal Hyphae Promote Soil Carbon Sequestration through Difficultly Extractable Glomalin-Related Soil Protein in Response to Soil Water Stress.

Soil water stress (WS) affects the decomposition of soil organic carbon (SOC) and carbon (C) emissions. Glomalin, released by arbuscular mycorrhizal fungi into soil that has been defined as glomalin-related soil protein (GRSP), is an important pool of SOC, with hydrophobic characteristics. We hypothesized that mycorrhizal fungi have a positive effect on SOC pools under soil WS for C sequestration in GRSP secreted by extraradical mycorrhizal hyphae. A microsystem was used to establish a root chamber (co-existence of roots and extraradical mycorrhizal hyphae) and a hyphal chamber (the presence of extraradical mycorrhizal hyphae) to study changes in plant growth, leaf water potential, soil aggregate stability, SOC, GRSP, C concentrations in GRSP (CGRSP), and the contribution of CGRSP to SOC after inoculating Rhizophagus intraradices with trifoliate orange(Poncirus trifoliata) in the root chamber under adequate water (AW) and WS. Inoculation with R. intraradices alleviated negative effects on leaf water potential and plant growth after 7weeks of WS. Soil WS decreased SOC and mean weight diameter (MWD), while AMF inoculation led to an increase in SOC and MWD in both chambers, with the most prominent increase in the hyphal chamber under WS.The C concentration in easily extractable GRSP (EE-GRSP) and difficultly extractable GRSP (DE-GRSP) was 7.32 - 12.57 and 24.90 - 32.60mg C/g GRSP, respectively. WS reduced CGRSP, while AMF mitigated the reduction. Extraradical mycorrhizal hyphae increased GRSP production and CGRSP, along with a more prominent increase in DE-GRSP under WS than under AW. Extraradical mycorrhizal hyphae increased the contribution of CDE-GRSP to SOC only under WS. CEE-GRSP and CDE-GRSP were significantly positively correlated with SOC and MWD. It is concluded that extraradical mycorrhizal hyphae prominently promoted C sequestration of recalcitrant DE-GRSP under soil WS, thus contributing more organic C accumulation and preservation in aggregates and soil C pool.

Effect of root‐glomalin on soil carbon storage in trees' rhizosphere and interspace of a tropical dry forest

AbstractIncreasing soil organic carbon (SOC) concentration is a desirable aspect of afforestation. Glomalin‐related soil protein (GRSP) is a ubiquitous component of SOC, preferentially produced by arbuscular mycorrhizal fungi (AMF) during symbiotic association with the plant roots. Although the role of AMF in GRSP production is well established, the role of root in GRSP production is not yet clear. Hence, we aimed to assess the glomalin in different tree roots (i.e., glomalin‐related root protein; GRRP) and its influence on GRSP and SOC storage in trees’ rhizosphere and interspace. The experiment was conducted in a tropical dry forest (India) with six native trees (Hardwickia binata, Lagerstroemia parviflora, Diospyros melanoxylon, Terminalia tomentosa, Shorea robusta, and Anogeissus latifolia) and a planted Teak (Tectona grandis). The fine roots (from the rhizosphere) and topsoils (0–15 cm) were collected from the rhizosphere and interspace of each tree. We found GRRP concentration varying between trees, with higher values observed in the roots of native trees than those of Teak. The AMF colonization was positively correlated with GRRP (r2 = 0.88), and GRRP positively correlated with GRSP and SOC. The higher correlation of GRRP was observed with GRSP (r2 = 0.70–0.79) compared with SOC (r2 = 0.56–0.58), while the correlation was much stronger between GRSP and SOC (r2 = 0.91). These results indicate that GRRP influences SOC storage via mediating GRSP concentration. We suggest that GRRP can be used as an indicator for species screening during afforestation with the aim to improve SOC storage on an afforested landscape.

Aggregation of a Ferruginous Nodular Gleysol in a pasture area in Cuba, under the influence of Arbuscular mycorrhizal fungi associated with hybrid Urochloa

The objective of this study was to evaluate in the field the influence of different arbuscular mycorrhizal fungi (AMF) inoculated in a pasture area of hybrid Urochloa (cv. CIAT BR 02/1752 “Caymam Pasture”) regarding the stability of aggregates of a Ferruginous Nodular Gleysol in Cuba. The experiment was conducted at the Pasture and Forage Experimental Station in Cuba (22°39′58.77″ N and 80°31′06.35″ W), using Urochloa hybrid, inoculated with three strains of AMF EcoMic® (Glomus cubense, Funneliformis mosseae and Rhizoglomus irregularis). The chosen design was in plots subdivided over time, with four treatments: three combined inoculations + non-inoculated treatment and two evaluation times (at 140 and 876 days after sowing). The number of spores, glomalin-related soil protein production, the quantification of total extraradicular mycelia, the structural stability coefficient of the soil (dry and wet) and the Soil Structural Stability Index were all evaluated. Greater stability of the aggregates was verified in dry sieving at 140 and 876 days of cultivation, however, influence of inoculation was only observed at 876 days. On the other hand, less stability was found for aggregates immersed in water. The effect of inoculation on soil aggregates can be associated with glomalin increments at 140 days, which has a cementing and cumulative character in the soil, and the length of mycelia at 876 days, which acts in the entanglement of mineral and organic soil particles, favoring the aggregation. Inoculation with AMF associated with the roots of hybrid Urochloa contributed to the best aggregate stability index at 876 days of cultivation, with an emphasis on the species G. cubense, which also showed greater competitiveness with a greater number of spores over time. Inoculation and/or soil management aimed at increasing the infectious potential of AMF is of great relevance for the formation and stability of soil aggregates in these grazing areas.

Glomalin contribution to soil organic carbon under different pasture managements in a saline soil environment

ABSTRACT The glomalin produced by arbuscular mycorrhizal fungi has beneficial effects on soils. We studied the vertical profile of glomalin-related soil protein (GRSP) in pasturelands grown under saline soils and exposed to different management practices. Treatments included haying and grazing of Chloris gayana subject to either N-fertilization or not. We measured mycorrhizal colonization, spores, root biomass, total GRSP, GRSP-carbon (GRSP-C), organic carbon (OC) and total nitrogen (TN). In the meanwhile, we also developed a mathematical procedure to fit continuous power functions to binned soil data. Power decay functions adjusted excellently well the measured data across the 1-meter soil profile. Meaningful increases of root biomass, OC, TN, GRSP and GRSP-C values were associated with grazing and fertilization. Particularly, GRSP-C averaged 1,134 kg C ha−1 at the beginning experiments and increased significantly up to 1,261 kg C ha−1 in grazed and fertilized pastures at the end of the study period. Carbon accounted for between 17% and 50% of GRSP, representing in turn 0.52–1.62% of SOC stock. So, a tropical perennial grass can contribute to the carbon stock in saline soils by promoting production of GRSP. This contribution increases when inputs and cycling of nutrients are enhanced (grazing and N-fertilization).

Enzyme Activity, Glomalin, and Soil Organic Carbon in Agroforestry Systems

Abstract This study aimed to evaluate enzyme activity, glomalin-related soil proteins (GRSP), soil chemical attributes, and total organic carbon (TOC) in two Agroforestry systems (AFS) (AFS-1 and AFS-2), in a traditional agriculture area (TA), and secondary forest (SF) area in Paraty (RJ). Soil samples (from 0 to 5 cm depth) were collected during the rainy and dry seasons. AFS improves and/or maintains soil chemical indicators based on pH increase, reduces aluminum saturation and maintains soil nutrient content (Ca, Mg and K), when compared with SF. The contribution of organic material and the biodiversity of the AFS provide the maintenance of the total organic carbon content of the soil. AFS maintain the activity of the enzymes protease, β-glucosidase, acid phosphatase, and total enzyme activity (FDA), and the production of glomalin-related soil protein at levels similar to those observed in SF, especially during the rainy season.

Effects of Vegetation Restoration on the Distribution of Nutrients, Glomalin-Related Soil Protein, and Enzyme Activity in Soil Aggregates on the Loess Plateau, China

Research Highlights: Soil enzymes have a significant impact on the production of glomalin-related soil protein (GRSP), directly and indirectly affecting the nutrient metabolism balance, but there is little available information on ecological stoichiometry in soil aggregates. Background and Objectives: Vegetation restoration changes community structure and species composition in ecosystems, thus changing the physicochemical properties of soil. Soil aggregate is the most basic physical structure of the soil. Therefore, in order to understand dynamic changes in soil aggregate nutrients as vegetation restoration progresses, we set out to investigate the nutrient distribution and utilization in aggregates, and how enzymes respond to the nutrient changes in achieving a nutritional balance along successive stages of vegetation restoration. Materials and Methods: We collected and analyzed soil from plots representing six different stages of a vegetation restoration chronosequence (0, 30, 60, 100, 130, and 160 years) after farmland abandonment on the Loess Plateau, China. We investigated soil nutrient stoichiometry, GRSP, and enzyme stoichiometry in the different successional stages. Results: The results revealed that soil organic carbon, total nitrogen, enzyme activity, and GRSP increased with vegetation recovery age, but not total phosphorus, and not all enzymes reached their maximum in the climax forest community. The easily extractable GRSP/total GRSP ratio was the largest at the shrub community stage, indicating that glomalin degradation was the lowest at this stage. Ecological stoichiometry revealed N-limitation decreased and P-limitation increased with increasing vegetation restoration age. Soil enzymes had a significant impact on the GRSP production, directly and indirectly affecting nutrient metabolism balance. Conclusions: Further study of arbuscular mycorrhizal fungi to identify changes in their category and composition is needed for a better understanding of how soil enzymes affect their release of GRSP, in order to maintain a nutrient balance along successive stages of vegetation restoration.

Arbuscular mycorrhizal fungi and Urochloa brizantha: symbiosis and spore multiplication

ABSTRACT Arbuscular mycorrhizal fungi (AMF) may exhibit distinct behaviors when associated with the same species of host plant, being necessary to understand their ecology, in order to optimize their management and maintenance in germplasm bank. This study aimed to evaluate different AMF associated with Urochloa brizantha (A. Rich.) Stapf by analyzing the symbiosis establishment time, spore multiplication and production of glomalin-related soil protein. The experiment was carried out in a completely randomized design, in a 6 x 5 arrangement (five AMF species, non-inoculated control treatment and five evaluation times). The following aspects were analyzed: plant growth, spore multiplication, mycorrhizal colonization and glomalin production. The highest number of spores occurred for Acaulospora longula and A. colombiana, exhibiting the highest mycorrhizal colonization at 76 days. The inoculation favored the root growth of U. brizantha at 15 days of cultivation, plant height and root dry matter at 60 days and shoot dry matter at 90 days, especially for the Acaulospora species. The inoculation with A. colombiana, A. longula and Paraglomus occultum resulted in increased glomalin at 120 days. Gigaspora margarita and P. occultum did not reach the maximum colonization and spore multiplication, indicating that a period of time longer than 120 days of cultivation is necessary.

Do different arbuscular mycorrhizal fungi affect the formation and stability of soil aggregates?

ABSTRACT Soil structure, which is defined by the arrangement of the particles and the porous space forming aggregates, is one of the most important properties of the soil. Among the biological factors that influence the formation and stabilization of soil aggregates, arbuscular mycorrhizal fungi (AMF) are distinguished due to extrarradicular hyphae and glomalin production. In this context, the objective of this study was to evaluate different AMF (Acaulospora colombiana, Acaulospora longula, Acaulospora morrowiae, Paraglomus occultum and Gigaspora margarita) associated with Urochloa brizantha (A. Rich.) Stapf on soil aggregate stability. The study was conducted in a completely randomized design, using an Oxisol and autoclaved sand 2:1 (v/v), with seven treatments: five AMF; and treatments with plants without inoculation and with only the soil, with 5 replicates. The experiment was conducted during 180 days and the following variables were evaluated: mycelium total length (TML); production of easily extractable glomalin-related soil protein (GRSP) in the soil and aggregate classes; stability of the dry and immersed in water aggregates through the mean geometric diameter (MGD) and the mean weighted diameter (MWD) of aggregates; and the soil aggregate stability index (ASI). It was observed that the inoculation favored soil aggregation, with a high incidence of A. colombiana, which presented the highest MGD, TML and GRSP production in the aggregates with Ø&gt;2.0mm and for A. colombiana and A. morrowiae in the aggregates with Ø&lt;0.105 mm, when compared to the treatment without inoculation. These results show that there is a distinction between the effects of different AMF on the formation and stability of soil aggregates.

Glomalin-Related Soil Protein Content in Areas of Degraded and Revegetated Caatinga in the Municipality of Irauçuba

Anthropic activities, combined with the natural ones, may trigger soil degradation, which has increased day by day and contributed to accentuating the desertification processes, resulting in losses of biodiversity and fertility of the soils. Because of that, the utilization of tools that indicate the stages of such degradation and recovery becomes necessary, in order to make viable and adequate management of these areas. Thus, the study on arbuscular mycorrhizal fungi (AMF), as a perspective to facilitate the recovery of degraded areas has increased, especially for the production of glomalin-related soil protein, which is of great importance for aggregate stability, besides showing a great potential of utilization as soil quality indicator. Therefore, the present study aimed to evaluate the contents of glomalin-related soil protein, correlating with chemical, physical and biological attributes in areas of the municipality of Irauçuba-CE: area degraded by overgrazing, area under process of natural revegetation managed with the exclusion of domestic animals and area of native forest, characterized by tree-shrub Caatinga vegetation. Disturbed soil samples were collected in the layer of 0-10 cm in each area and evaluated for AMF attributes, soil chemical attributes and physical attributes. The results obtained with the tests of means prove that, among the three areas, only the native forest showed significant differences with respect to both fractions of the protein. However, in regard to spore density and aggregate stability, the areas of native forest and exclusion showed the best mean values. The content glomalin-related soil protein (GRPS), associated with other edaphic attributes, contributes to discriminating the quality and to the monitoring of areas with different levels of soil degradation. The highest correlation values were observed among the contents of calcium, nitrogen and organic carbon and both GRSP fractions (easily extractable: GRSPEE,which represents the recently deposited frsction that has not yet suffered biochemical alterations in the soil; total: GRSPT, which is strongly adhered to the clays), indicating that the protein directly influences the contents of these elements in the soil.

Glomalin accumulated in seagrass sediments reveals past alterations in soil quality due to land-use change

Arbuscular mycorrhizal fungi (AMF), symbionts with most terrestrial plants, produce glomalin-related soil protein (GRSP), which plays a major role in soil structure and quality. Both fungi hyphae and protein production in soils are affected by perturbations related to land-use changes, implying that GRSP is a sensitive indicator of soil quality. Unfortunately, GRSP degrades within years to decades in oxic environments, preventing its use as palaeoecological proxy. However, GRSP is transported to marine, near-shore anoxic sediments, where it accumulates and remains non-degraded, enabling the assessment of its potential as a palaeoecological proxy for soil ecosystem's health. Exploiting this fact, we have obtained for the first time a long-term record (c. 1250years) of GRSP content using a Posidonia oceanica seagrass mat sediment core from the Western Mediterranean (Portlligat Bay, Spain). The trends in GRSP content matched well with land-use changes related to agrarian activities reconstructed by pollen analysis. In periods of cultivation, GRSP accumulation in the mat decreased. Given the role played by GRSP, the results suggest that agrarian intensification may have resulted in perturbations to soil quality. Thus, GRSP in seagrass mat sediments can be used to assess long-term trends in continental soil quality induced by human activities. These findings open new possibilities in long-term ecology research, as other anoxic environments could be potentially valid too. Testing them would open the possibility to identify long-term patterns in soil quality and other environmental stressors that could also affect AMF and GRSP production in soils.

Exogenous application of EE-GRSP and changes in citrus rhizosphere properties

Mycorrhization-induced secretion of glomalin-related soil protein (GRSP) is known to contribute in improving soil fertility and aggregate stability. But, there is hardly any evidence that exogenous GRSP could produce the similar type of response. The present study was, therefore, carried out to extract easily extractable GRSP (EE-GRSP) from citrus rhizosphere soils and evaluate the response at 1/4, 1/2 and full strength EE-GRSP solutions watered into the rhizosphere of 27-year-old Satsuma mandarin (Citrus unshiu) grafted on the rootstock of Poncirus trifoliata. After ~5 months, exogenous EE-GRSP treatments produced significantly positive responses on endogenous EE-GRSP, difficultly-extractable GRSP (DE-GRSP), total GRSP production and soil organic carbon (SOC) content. A significantly positive correlation of these endogenous GRSP fractions with SOC indicated an active participation of GRSP on soil C pool. Exogenous GRSP showed a key role in binding water-stable aggregate (WSA) at 2–4, 1–2, 0.5–1, and 0.25– 0.5 mm size and enhancing WSA stability through changes in mean weight diameter (MWD). A stronger correlation of EE-GRSP and total GRSP with MWD was observed than DE-GRSP fraction. On the other hand, exogenous EEGRSP showed a positive effect on soil phosphatase activity, and soil endogenous EE-GRSP was significantly and positively correlated only with neutral phosphatase. Our studies suggest that exogenous EE-GRSP could be used as an effective regulator to affect soil fertility and soil structure within citrus rhizosphere.

Arbuscular mycorrhiza mediates glomalin-related soil protein production and soil enzyme activities in the rhizosphere of trifoliate orange grown under different P levels.

Glomalin-related soil protein (GRSP) is beneficial to soil and plants and is affected by various factors. To address whether mycorrhizal-induced GRSP and relevant soil enzymes depend on external P levels, a pot study evaluated effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae on GRSP production and soil enzyme activities. Three GRSP categories, as easily-extractable GRSP (EE-GRSP), difficultly-extractable GRSP (DE-GRSP), and total (EE-GRSP + DE-GRSP) GRSP (T-GRSP), were analyzed, together with five enzyme activities (β-glucosidase, catalase, peroxidase, phosphatase, polyphenol oxidase) in the rhizosphere of trifoliate orange (Poncirus trifoliata) grown under 0, 3, and 30mM KH2PO4 in a sand substrate. After 4months, root AM colonization and substrate hyphal length decreased with increasing P levels. Shoot, root, and total biomass production was significantly increased by AM colonization, regardless of P levels, but more profound under 0mM P than under 30mM KH2PO4. In general, production of these three GRSP categories under 0 or 30mM KH2PO4 was similar in non-mycorrhizosphere but decreased in mycorrhizosphere. Mycorrhization significantly increased the production of EE-GRSP, DE-GRSP and T-GRSP, soil organic carbon (SOC), and activity of substrate β-glucosidase, catalase, peroxidase, and phosphatase, but decreased polyphenol oxidase activity, irrespective of P levels. Production of EE-GRSP, DE-GRSP, and T-GRSP significantly positively correlated with SOC and β-glucosidase, catalase, and peroxidase activity, negatively with polyphenol oxidase activity, but not with hyphal length or phosphatase activity. These results indicate that AM-mediated production of GRSP and relevant soil enzyme activities may not depend on external P concentrations.

&lt;b&gt;Arbuscular mycorrhizal fungi within agroforestry and traditional land use systems in semi-arid Northeast Brazil&lt;/b&gt; - doi: 10.4025/actasciagron.v35i3.16213

The diversity of arbuscular mycorrhizal fungi (AMF) can be a critical factor in enhancing both the productivity and the diversity of plants in ecosystems, and the plants in the ecosystem also strongly influence the occurrence of these fungi. The relationships between different land use systems and AMF communities in the semi-arid region of the State of Paraíba, NE Brazil were evaluated. The experiment followed a split-plot randomized block design, with four replicates. The main plots were defined by the presence or absence of trees (gliricidia and maniçoba), while the split plots were defined by three land use systems: 1) traditional cropping of maize + beans, 2) buffel grass pasture, and 3) prickly pear forage crop. The presence of trees increased sporulation, mycorrhizal colonization and the production of infective propagules of AMF in all three land use systems. Greater production of glomalin-related soil protein (GRSP) occurred in the prickly pear plots regardless of the presence or absence of trees. Species belonging to the Glomus genus predominated regardless of the presence of trees, land use systemor soil sampling period.

Fungos micorrízicos arbusculares e proteína do solo relacionada à glomalina em área degradada por extração de argila e revegetada com eucalipto e acácia

http://dx.doi.org/10.5902/198050987556Esse estudo teve como objetivo avaliar a influência da revegetação com Eucalyptus camaldulensis e Acacia mangium, em plantio puro e consorciado, na composição e diversidade de fungos micorrízicos arbusculares (FMAs), bem como na quantidade da proteína do solo relacionada à glomalina (PSRG) em uma área degradada pela extração de argila. O delineamento experimental utilizado foi o de blocos casualizados com quatro tratamentos (plantios puros de Eucalyptus camaldulensis e Acacia mangium; consórcio de Eucalyptus camaldulensis + Acacia mangium; e área degradada com vegetação espontânea – ADVE) e três repetições, onde, em cada uma das parcelas, foram coletadas amostras de solo na camada 0-5 cm. Os esporos de FMA foram extraídos e taxonomicamente identificados. Analisou-se a densidade relativa, a frequência de cada espécie e os índices de Shannon-Wiener, Pielou e de Simpson. A PSRG (glomalina total – GT e glomalina facilmente extraível – GFE) foi extraída com citrato de sódio e quantificada pelo método de Bradford. A abundância de FMAs foi maior na área degradada com vegetação espontânea quando comparada aos plantios, em contrapartida apresentou baixa diversidade de espécies. As áreas de eucalipto em monocultivo mostraram menor índice de diversidade de FMAs em relação às áreas de eucalipto consorciadas com a acácia. Glomus e Acaulospora foram os gêneros de FMAs que apresentaram o maior número de espécies. A PSRG foi estreitamente correlacionada com o C e o N do solo, tendo sido observada em maiores quantidades nos plantios, em relação à ADVE. A revegetação da cava de extração de argila promoveu redução na esporulação dos FMAs, enquanto a diversidade e a quantidade de PSRG foram aumentadas.

O papel da comunidade de fungos micorrízicos arbusculares (FMA) autóctones no desenvolvimento de espécies vegetais nativas em área de dunas de restinga revegetadas no litoral do Estado da Paraíba

A simbiose entre fungos micorrizicos arbusculares (FMA) com raizes de plantas vasculares constitui uma das mais importantes formas de mitigar o impacto das areas pertubadas. O trabalho objetivou caracterizar a comunidade de FMA presente no solo de area de duna revegetada e avaliar sua influencia sobre o desenvolvimento de especies nativas. Foi realizada coleta de solo durante o periodo chuvoso em area revegetada, avaliando-se: producao de proteinas do solo relacionadas a glomalina (PSRG), densidade e diversidade de glomerosporos. A influencia da comunidade nativa de FMA foi determinada para duas especies vegetais nativas: Tabebuia roseo-alba (Ridl.) Sandw. (peroba) e Tocoyena selloana Schum. (jenipapo-bravo). Para cada especie foram testados dois tratamentos - solo nativo (SN) e solo nativo desinfestado (SND) - em delineamento inteiramente casualizado com 10 repeticoes. Ao final foram avaliados: altura, diâmetro do caule, numero de folhas, area foliar, biomassa seca e conteudo de nutrientes nas partes aerea e radicular, densidade de glomerosporos, colonizacao micorrizica hifalica, arbuscular, vesicular e total e producao de proteinas do solo relacionadas a glomalina (PSRG). O solo da area de duna revegetada apresentou 1 glomerosporo g-1 de solo e 1,20 ± 0,04 mg PSRG g-1 solo, sendo identificadas seis especies de FMA. Maior desenvolvimento vegetal e fungico ocorreram no SN. A colonizacao micorrizica na peroba foi de 80% e no jenipapo-bravo 60%. Os FMA estao presentes em areas revegetadas apos extracao de minerios, e contribuem para o crescimento das especies nativas testadas em condicoes de casa de vegetacao, sugerindo assim, que o desempenho dessas plantas e influenciado pela simbiose micorrizica arbuscular.

Re-examining the glomalin-purity of glomalin-related soil protein fractions through immunochemical, lectin-affinity and soil labelling experiments

Due to analytical similarities with the mycorrhizal glycoprotein glomalin, ubiquitous citrate and heat-extractable soil protein fractions have been assumed to be predominantly glomalin-stabilised within soil. Often termed glomalin-related soil protein (GRSP), little however is actually known of the “glomalin-purity” of these soil fractions. We undertook western and lectin blots and crossed immuno/lectin affinity electrophoresis (CIE/CLAE) analysis of “easily extractible” GRSP fractions, as well as liquid chromatography-tandem mass spectrometry (LC–MS/MS) of “total” GRSP fractions. To further test whether soil saprobes contribute to GRSP production, we amended soil with 14C-sucrose and examined whether 14C could be traced in the GRSP pool over a 500-day incubation period. While only four of six bands on SDS–PAGE profiles of easily extracted GRSP reacted with anti-glomalin MAb32B11 and the lectin Con A under our blotting conditions, CIE/CLAE indicated the presence of a single protein moiety in the easily extractible GRSP pool. LC–MS/MS analysis of total GRSP pooled from various soils also showed that although traces of protein tentatively assignable to soil bacteria were present in GRSP, their concentrations were low. Additionally, specific activity of total GRSP in 14C-labelled soil was relatively depleted compared to the bulk soil and soil microbial biomass. This suggests that little GRSP of heterotrophic origin was laid down over the incubation period, although the potential presence of a pre-existing 14C-free GRSP background, as well as of low microbial dynamics in the absence of any further substrate inputs to the soil warrant caution with this inference.

Arbuscular mycorrhizae, glomalin, and soil aggregation

Arbuscular mycorrhizae are important factors of soil quality through their effects on host plant physiology, soil ecological interactions, and their contributions to maintaining soil structure. The symbiosis is faced with numerous challenges in agroecosystems; in order to inform sustainable management strategies it is hence a high priority to work towards mechanistic understanding of arbuscular mycorrhizae contributions to soil quality. This review focuses on glomalin-related soil protein (GRSP), operationally defined soil C pools that have been linked to arbuscular mycorrhizal fungi (AMF). In discussing this protein pool, we propose a new terminology used to describe fractions of soil proteins and glomalin. GRSP concentrations in soil are positively correlated with aggregate water stability. GRSP has relatively slow turnover in soil, contributing to lasting effects on aggregation. Controls on production of GRSP at the phenomenological and mechanistic level are evaluated. While there are significant gaps in our knowledge about GRSP and glomalin (particularly at the biochemical level), it is concluded that research on GRSP holds great promise for furthering our knowledge of soil structure and quality, for informing suitable management, and as a foundation for novel biotechnological applications in agriculture and beyond. Key words: Glomalin, GRSP, soil structure, land use, restoration, soil protein, sustainability, arbuscular mycorrhizae