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Figure 5 in Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Figure 5. Non-metric multidimensional ordering (NMDS) of tree species treated with herbicides and control was performed for all analyzed variables of the tree species.

Figure 1 in Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Figure 1. Percentage of total dry mass in relation to the control treatment of seedlings of forest trees species subjected to the herbicides atrazine and sulfentrazone via sub-irrigation. Averages followed by the same lowercase letter do not differ by Tukey's test at 5% significance for the herbicidal factor. Means followed by the same capital letter do not differ according to the Scott-Knott grouping criterion at 5% significance for the species. CV (Coefficient of variation) = 18.3%.

Figure 3 in Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Figure 3. Spore count percentage in relation to the control treatment of seedlings of forest trees species subjected to the herbicides atrazine and sulfentrazone via sub-irrigation. Averages followed by the same lowercase letter do not differ by Tukey's test at 5% significance for the herbicidal factor. Means followed by the same capital letter do not differ according to the Scott-Knott grouping criterion at 5% significance for the species. CV (Coefficient of variation) = 10.96%.

Figure 4 in Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Figure 4. Percentage of basal soil respiration in relation to the control treatment of seedlings of forest tree species subjected to the herbicides atrazine and sulfentrazone via sub-irrigation. Averages followed by the same lowercase letter do not differ by Tukey's test at 5% significance for the herbicidal factor. Means followed by the same capital letter do not differ according to the Scott-Knott grouping criterion at 5% significance for the species. CV (Coefficient of variation) = 11.63%.

Figure 2 in Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides

Figure 2. Percentage of rhizospheric colonization by mycorrhizae in relation to the control treatment of seedlings of forest trees species subjected to the herbicides atrazine and sulfentrazone via sub-irrigation. Averages followed by the same lowercase letter do not differ by Tukey's test at 5% significance for the herbicidal factor. Means followed by the same capital letter do not differ according to the Scott-Knott grouping criterion at 5% significance for the species. CV (Coefficient of variation) = 8.93%.

openCC0Jan 2021View details →

edi40/100

Soil extracellular enzyme activities in plots dominated by trees that associate with arbuscular mycorrhizal or ectomycorrhizal fungi in the N fertilized and reference watershed at the Bear Brook Watershed in Maine, USA.

Our objective was to detect possible differences in N fertilization responses of soil extracellular enzymes in plots dominated by trees that associate with arbuscular mycorrhizal fungi (AM) or ectomycorrhizal fungi (ECM). To do this, we established a plot network of 6 AM and 6 ECM dominated (>65% diameter at breast height) 10 x 10 m plots in the lower elevation hardwood zone of both the reference and N fertilized watersheds (N=24 plots) at Bear Brook Watershed, in Maine USA. We assayed the potential activity of hydrolytic enzymes that release N (N-acetylglucosaminidase; NAG), phosphorus (acid phosphatase; AP), and simple carbon (ß-glucosidase; BG). In addition, we measured microbial allocation to complex C degrading oxidative enzymes phenol oxidase and peroxidase. The activities of these enzymes were measured separately in bulk mineral, rhizosphere, and organic horizon soils during the growing season in 2016.

edi40/100

Fine root morphology in plots dominated by trees that associate with arbuscular mycorrhizal or ectomycorrhizal fungi in the N fertilized and reference watershed at the Bear Brook Watershed in Maine, USA during the final year of N fertilization (2016) and during the year after N fertilization ceased (2017).

Our objective was to detect possible differences in N fertilization responses of fine root morphology in plots dominated by trees that associate with arbuscular mycorrhizal fungi (AM) or ectomycorrhizal fungi (ECM). To do this, we sampled fine roots in a plot network of 6 AM and 6 ECM dominated (>65% diameter at breast height) 10 x 10 m plots in the lower elevation hardwood zone of both the reference and N fertilized watersheds (N=24 plots) at Bear Brook Watershed, in Maine USA during final year of N fertilization at Bear Brook in 2016 and during the year after N fertilization ceased in 2017.

openCC0Aug 2021View details →

zenodo36/100

Ectomycorrhizal trees rely on nitrogen resorption less than arbuscular mycorrhizal trees globally

Nitrogen (N) resorption is an important pathway of N conservation, contributing to a proportion of plant N requirement. However, whether the ratio of N resorption to N requirement would be affected by environmental factors, mycorrhizal types or atmospheric CO2 concentration remains unclear. Here, we conducted a meta-analysis on the impacts of environmental factors and mycorrhizal types on this ratio. We found this ratio in ectomycorrhizal (EM) trees decreased with mean annual precipitation (MAP), mean annual temperature (MAT), soil total N content (TN) and atmospheric CO2 concentration and was significantly lower than that in arbuscular mycorrhizal (AM) trees. An in situ 15N tracing experiment further confirmed this stronger reliance on N resorption for AM trees than EM trees. Our study suggests that AM and EM trees potentially have different strategies for alleviation of progressive N limitation, highlighting the necessity of incorporating plant mycorrhizal types into Earth System Models.

opencc-by-4.0Oct 2023View details →

opencc-zeroOct 2022View details →

Ectomycorrhizal (Dipterocarp) and arbuscular mycorrhizal (non-dipterocarp) tree

The type of mycorrhizal associations (i.e. ecto- or arbuscular mycorrhizal) formed by trees is of fundamental importance for a range of soil properties and processes in forest ecosystems, yet their importance for the distribution of other important soil biota such as bacteria is still largely unknown. This is especially so in diverse tropical forests where trees of different mycorrhizal types are intermingled in a highly heterogeneous biotic and abiotic environment. Here we used an experimental common garden that helped us to assess how abiotic and biotic variation differentially influenced bacterial communities associated with trees planted in a secondary tropical forest of Borneo. We used high-throughput amplicon sequencing to characterize rhizosphere bacterial communities of 13 climax tree species (8 ectomycorrhizal and 5 arbuscular mycorrhizal) in relation to plant traits, plant neighborhood, and abiotic environment. Rhizosphere bacterial (RB) communities differed significantly between EM and AM trees but not among EM species and only marginally among AM species. Foliar nutrients, especially potassium, showed relationships with RB community composition. Rhizosphere bacterial communities were related to the density and size of neighboring ectomycorrhizal but not arbuscular mycorrhizal trees. Diversity of RB on AM trees responded positively to AM neighbors and negatively to EM neighbors but RB diversity associated with EM trees was unaffected by neighborhood. Rhizosphere bacterial communities of AM trees were more responsive to environmental variation such as light availability and position on a slope. Plant-growth-promoting taxa of RB assorted similarly to total RB but more strongly. Synthesis: Our results suggest that the distribution of rhizosphere bacterial communities is linked to plant functional group and plant neighborhood. Because rhizosphere bacteria play important roles in nutrient cycling that influence plant species composition, it is likely that their distributional patterns are important for understanding ecosystem processes and plant demographics.

opencc-zeroJul 2023View details →

Seedling performance in a dioecious tree species is similar near female and male conspecific adults despite differences in colonization by arbuscular mycorrhizal fungi

Plant–soil feedbacks (PSFs) are a key driver of species diversity and composition in plant communities worldwide; however, the factors that may cause feedbacks to vary within species are rarely examined. In dioecious species, the strength of feedbacks may differ near female plants that produce seed versus near male plants (which do not) because repeated inputs of seeds and high seedling densities near females may cause accumulation of host‐specific soil microbes that influence seedling performance. To test whether conspecific seedling performance is reduced near seed‐producing female trees relative to male or heterospecific trees, we conducted shadehouse and field experiments with a dioecious tropical tree species, Virola surinamensis (Myristicaceae), on Barro Colorado Island, Panama. The shadehouse experiment isolated the effect of soil microbial communities on seedling growth and allowed us to quantify colonization by mutualistic arbuscular mycorrhizal (AM) fungi, while the field experiment allowed us to assess seedling survival and growth in the presence of nearby conspecific adults and seedlings. In both experiments, seedling performance was similar between seedlings grown in the soil microbial communities and field environments underneath female conspecific, male conspecific, and heterospecific trees. However, contrary to expectation, seedling colonization by AM fungi was higher in male conspecific soil microbial communities than in female or heterospecific soil microbial communities at the end of the shadehouse experiment. Together, our experiments show that while differences among female and male plants in dioecious species may influence the association of conspecific seedlings with AM fungi in their soils, this variation does not necessarily translate directly to differences in seedling performance, at least over the time frame of our experiments. Studies of additional dioecious species are needed to help determine differences in soil microbial communities beneath male and female plants and to assess the role of seed input versus adult root systems in driving PSFs.

opencc-zeroJul 2023View details →

Depth-dependent effects of Ericoid Mycorrhizal shrubs on soil carbon and nitrogen pools are accentuated under Arbuscular Mycorrhizal Trees

Plant mycorrhizal associations influence the accumulation and persistence of soil organic matter and could therefore shape ecosystem biogeochemical responses to global changes that are altering forest composition. For instance, arbuscular mycorrhizal (AM) tree dominance is increasing in temperate forests, and ericoid mycorrhizal (ErM) shrubs can respond positively to canopy disturbances. Yet how shifts in the co-occurrence of trees and shrubs with different mycorrhizal associations will affect soil organic matter pools remains largely unknown. We examine the effects of ErM shrubs on soil carbon and nitrogen stocks and indicators of microbial activity at different depths across gradients of AM versus ectomycorrhizal (EcM) tree dominance in three temperate forest sites. We find that ErM shrubs strongly modulate tree mycorrhizal dominance effects. In surface soils, ErM shrubs increase particulate organic matter accumulation and weaken the positive relationship between soil organic matter stocks and indicators of microbial activity. These effects are strongest under AM trees that lack fungal symbionts that can degrade organic matter. In subsurface soil organic matter pools, by contrast, tree mycorrhizal dominance effects are stronger than those of ErM shrubs. Ectomycorrhizal tree dominance has a negative influence on particulate and mineral-associated soil organic matter pools, and these effects are stronger for nitrogen than for carbon stocks. Our findings suggest that increasing co-occurrence of ErM shrubs and AM trees will enhance particulate organic matter accumulation in surface soils by suppressing microbial activity while having little influence on mineral-associated organic matter in subsurface soils. Our study highlights the importance of considering interactions between co-occurring plant mycorrhizal types, as well as their depth-dependent effects, for projecting changes in soil carbon and nitrogen stocks in response to compositional shifts in temperate forests driven by disturbances and global change.