Staining and microscopy of mycorrhizal fungal colonization in preserved ericoid plant roots

BACKGROUND: Visualization of ericoid mycorrhizal colonization using traditional methods relies on either fresh or KOH stored samples. Increasing interest in studying ericoid mycorrhization has highlighted a need for methods which can be used for preserved samples and are simple to implement with commonly available equipment. OBJECTIVE: The aim of this study was to improve on traditional techniques for staining ericoid mycorrhizal fungi and microscopically visualizing ericoid mycorrhizal roots which have been preserved. METHODS: Ericoid mycorrhizal roots were placed in KOH or frozen at -20 degrees C for long-term storage. Traditional Trypan Blue staining methods were modified to reduce damage to fine mycorrhizal hyphae and cortical cells. A high light-intensity dark-field microscopy technique was applied to clearly visualize stained mycorrhizae. The novel application was compared to other commonly used practices. RESULTS: Trypan Blue staining without KOH storage or clearing allowed for successful staining of ericoid mycorrhizal roots stored at -20 degrees C. The application of high light-intensity dark-field microscopy provided high contrast visualization of mycorrhizal structures. CONCLUSIONS: The modified Trypan Blue staining method was effective on frozen root samples, with dark-field microscopy being particularly effective at visualizing dark colored roots. Advantages to this method are lowcost and relatively fast application time. Therefore, this method is a realistic option for large scale analyses with many samples which require long-term preservation.Peer reviewe

Mechanisms of Carbon Sequestration in Highly Organic Ecosystems – Importance of Chemical Ecology

Abstract Organic matter decomposition plays a major role in the cycling of carbon (C) and nutrients in terrestrial ecosystems across the globe. Climate change accelerates the decomposition rate to potentially increase the release of greenhouse gases and further enhance global warming in the future. However, fractions of organic matter vary in turnover times and parts are stabilized in soils for longer time periods (C sequestration). Overall, a better understanding of the mechanisms underlying C sequestration is needed for the development of effective mitigation policies to reduce land-based production of greenhouse gases. Known mechanisms of C sequestration include the recalcitrance of C input, interactions with soil minerals, aggregate formation, as well as its regulation via abiotic factors. In this Minireview, we discuss the mechanisms behind C sequestration including the recently emerging significance of biochemical interactions between organic matter inputs that lead to C stabilization.Peer reviewe

Contribution of understorey vegetation and soil processes to boreal forest isoprenoid exchange

Boreal forest floor emits biogenic volatile organic compounds (BVOCs) from the understorey vegetation and the heterogeneous soil matrix, where the interactions of soil organisms and soil chemistry are complex. Earlier studies have focused on determining the net exchange of VOCs from the forest floor. This study goes one step further, with the aim of separately determining whether the photosynthesized carbon allocation to soil affects the isoprenoid production by different soil organisms, i.e., decomposers, mycorrhizal fungi, and roots. In each treatment, photosynthesized carbon allocation through roots for decomposers and mycorrhizal fungi was controlled by either preventing root ingrowth (50 mu m mesh size) or the ingrowth of roots and fungi (1 mu m mesh) into the soil volume, which is called the trenching approach. Isoprenoid fluxes were measured using dynamic (steady-state flow-through) chambers from the different treatments. This study aimed to analyze how important the understorey vegetation is as a VOC sink. Finally, a statistical model was constructed based on prevailing temperature, seasonality, trenching treatments, understory vegetation cover, above canopy photosynthetically active radiation (PAR), soil water content, and soil temperature to estimate isoprenoid fluxes. The final model included parameters with a statistically significant effect on the isoprenoid fluxes. The results show that the boreal forest floor emits monoterpenes, sesquiterpenes, and isoprene. Monoterpenes were the most common group of emitted isoprenoids, and the average flux from the non-trenched forest floor was 23 mu gm(-2) h(-1). The results also show that different biological factors, including litterfall, carbon availability, biological activity in the soil, and physico-chemical processes, such as volatilization and absorption to the surfaces, are important at various times of the year. This study also discovered that understorey vegetation is a strong sink of monoterpenes. The statistical model, based on prevailing temperature, seasonality, vegetation effect, and the interaction of these parameters, explained 43% of the monoterpene fluxes, and 34-46% of individual alpha pinene, camphene, beta-pinene, and Delta(3)-carene fluxes.Peer reviewe

Sysmän yksityismetsänomistajien suhtautuminen metsäluonnon suojeluun ja hoitoon

TutkimusartikkeliTutkimuksessa selvitettiin Sysmän yksityismetsien omistajien suhtautumista maa- ja metsätalousministeriön ja ympäristöministeriön laatimiin, ympäristönäkökulmat huomioon ottaviin metsänhoito-ohjeisiin. Tämän lisäksi selvitettiin metsänomistajien metsiin liittämiä aineettomia merkityksiä sekä suhdetta luontoon. Tutkimus toteutettiin lomakekyselynä. §§ Tutkimuksen mukaan taloudellinen turvallisuus ja puunmyyntitulot ovat selkeästi metsänomistuksen tärkein tavoite Sysmässä. Taloudellisten arvojen korostaminen ei kuitenkaan poissulje täysin muita näkökulmia, ja metsänomistajat suhtautuvatkin varsin myönteisesti uusiin toimenpide-ehdotuksiin. Varauksellisempia erilaisia suojeluehdotuksia kohtaan olivat nuoret ja suurien tilojen omistajat. Haluttomuutta metsäluonnon suojeluun saattaa nostattaa myös suojelumenettely §§ Sysmässä näin on käynyt esimerkiksi valkoselkätikan suojelun kohdalla. §§ Tutkimuksen mukaan sysmäläiselle metsänomistajalle metsä on olennainen osa kodin ympäristöä ja maisemaa sekä paikka, josta voi tarpeen tullen hakea mielenrauhaa. Ahdistavaksi tai pelottavaksi paikaksi metsän koki kymmenesosa vastaajista

The effect of plant-derived C flow on the microbial community structure and enzymatic activities in boreal forest

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Interaction between tannins and fungal necromass stabilizes fungal residues in boreal forest soils

See also the Commentary on this article by Hattenschwiler et al., 223: 5-7.Peer reviewe

Contrasting effects of reindeer grazing on CO2, CH4, and N2O fluxes originating from the northern boreal forest floor

SPECIAL ISSUE ARTICLE Editor Dr. Chris J. BarrowReindeer (Rangifer tarandus L.) is considered to be an important mammalian herbivore, strongly influencing Arctic lichen-dominated ecosystems. There is no wide knowledge about the effect of reindeer on greenhouse gas (GHG) fluxes in northern boreal forests. Ground vegetation plays an important role in absorbing nitrogen (N) and carbon dioxide (CO2) from the atmosphere. Lately, it has also been found to be a significant source of nitrous oxide (N2O) and a small source of methane (CH4). We investigated the influence of reindeer grazing on field layer GHG (CO2, CH4, and N2O) fluxes, ground vegetation coverage and biomass, and soil physical properties (temperature and moisture) in a northern boreal forest. At our study site, the reindeer-induced replacement of lichen by mosses had contrasting effects on the GHG fluxes originating from the field layer. Field layer CO2 efflux was significantly higher in grazed areas. The field layer was a CH4 sink in all areas, but grazed areas absorbed more CH4 compared to non-grazed areas. Although total N2O fluxes remained around 0 in grazed areas, a small N2O sink occurred in non-grazed areas with lower moss biomass. Our results indicated that grazing by reindeer in northern boreal forests affects GHG fluxes from the forest field layer both positively and negatively, and these emissions largely depend on grazing-induced changes in vegetation composition.Peer reviewe

Microbial biodiversity contributes to soil carbon release : a case study on fire disturbed boreal forests

Microbial biodiversity plays the dominant role in soil carbon emissions in fire-disturbed boreal forests. Microbial communities often possess enormous diversity, raising questions about whether this diversity drives ecosystem functioning, especially the influence of diversity on soil decomposition and respiration. Although functional redundancy is widely observed in soil microorganisms, evidence that species occupy distinct metabolic niches has also emerged. In this paper, we found that apart from the environmental variables, increases in microbial diversity, notably bacterial diversity, lead to an increase in soil C emissions. This was demonstrated using structural equation modelling (SEM), linking soil respiration with naturally differing levels of soil physio-chemical properties, vegetation coverage, and microbial diversity after fire disturbance. Our SEMs also revealed that models including bacterial diversity explained more variation of soil CO2 emissions (about 45%) than fungal diversity (about 38%). A possible explanation of this discrepancy is that fungi are more multifunctional than bacteria and, therefore, an increase in fungal diversity does not necessarily change soil respiration. Further analysis on functional gene structure suggested that bacterial and fungal diversities mainly explain the potential decomposition of recalcitrant C compare with that of labile C. Overall, by incorporating microbial diversity and the environmental variables, the predictive power of models on soil C emission was significantly improved, indicating microbial diversity is crucial for predicting ecosystem functions.Peer reviewe

Root presence modifies the long-term decomposition dynamics of fungal necromass and the associated microbial communities in a boreal forest

Recent studies have highlighted that dead fungal mycelium represents an important fraction of soil carbon (C) and nitrogen (N) inputs and stocks. Consequently, identifying the microbial communities and the ecological factors that govern the decomposition of fungal necromass will provide critical insight into how fungal organic matter (OM) affects forest soil C and nutrient cycles. Here, we examined the microbial communities colonising fungal necromass during a multiyear decomposition experiment in a boreal forest, which included incubation bags with different mesh sizes to manipulate both plant root and microbial decomposer group access. Necromass-associated bacterial and fungal communities were taxonomically and functionally rich throughout the 30 months of incubation, with increasing abundances of oligotrophic bacteria and root-associated fungi (i.e., ectomycorrhizal, ericoid mycorrhizal and endophytic fungi) in the late stages of decomposition in the mesh bags to which they had access. Necromass-associated beta-glucosidase activity was highest at 6 months, while leucine aminopeptidase peptidase was highest at 18 months. Based on an asymptotic decomposition model, root presence was associated with an initial faster rate of fungal necromass decomposition, but resulted in higher amounts of fungal necromass retained at later sampling times. Collectively, these results indicate that microbial community composition and enzyme activities on decomposing fungal necromass remain dynamic years after initial input, and that roots and their associated fungal symbionts result in the slowing of microbial necromass turnover with time.Peer reviewe