Early-successional ectomycorrhizal fungi effectively support extracellular enzyme activities and seedling nitrogen accumulation in mature forests

Abstract

After stand-replacing disturbance, regenerating conifer seedlings become colonized by different ectomycorrhizal fungi (EMF) than the locally adapted EMF communities present on seedlings in mature forests. We studied whether EMF species that colonized subalpine fir (Abies lasiocarpa) seedlings in clearcuts differed from those that colonized seedlings in adjacent mature forests with respect to mycorrhizoplane extracellular enzyme activities (EEAs) and N status of the seedlings. We tested two alternate hypotheses: (1) that EEAs would differ between the two EMF communities, with higher activities associated with forest-origin communities, and (2) that acclimation to soil environment was considerable enough that EEAs would be determined primarily by the soil type in which the ectomycorrhizas were growing. Naturally colonized fir seedlings were reciprocally transplanted between clearcuts and forests, carrying different EMF communities with them. EEAs were influenced more by destination environment than by EMF community. EEAs were as high in early-successional as in late-successional communities in both destination environments. Buds of clearcut-origin seedlings had the same or higher N contents as forest seedlings after a growing season in either environment. These results indicate that (i) symbiotic EMF and/or their associated microbial communities demonstrate substantial ability to acclimate to new field environments; (ii) the ability to produce organic matter-degrading enzymes is not a trait that necessarily distinguishes early- and late-successional EMF communities in symbiosis; (iii) early-successional EMF are as capable of supporting seedling N accumulation in forest soils as late-successional EMF; and (iv) disturbed ecosystems where early-successional EMF are present should have high resilience for organic matter degradation.

Limited Effects of Variable-Retention Harvesting on Fungal Communities Decomposing Fine Roots in Coastal Temperate Rainforests

“…However, soil nitrogen concentrations initially increased in response to clearcutting but became negligible after 5 years in a forest type similar to that in our study (44). Host specificity is an unlikely explanation for the delayed establishment of these species, as both are known generalists (45), nor is dispersal limitation, as at least Wilcoxina is a widespread genus in North American spore banks (46), and Amphinema species have been reported in seedling bioassays within 5 years of harvesting (47). R. vinicolor may simply be more competitive early in succession but declined in response to increased competition from Amphenima spp.…”

Early Stage Root-Associated Fungi Show a High Temporal Turnover, but Are Independent of Beech Progeny

“…Moreover, ectomycorrhizal colonization is characterized by priority effects, i.e., early colonizers can outcompete others when new root tips become available [59]. Thus, some of the these ectomycorrhizal pioneers can persist many years even after new tree transplantation events [60], which might account for the stable part of the symbiotrophic communities. Supposedly, saprotrophic fungi benefit from this relative stability of symbiotrophic diversity and community structure.…”

Phosphorus deficiencies invoke optimal allocation of exoenzymes by ectomycorrhizas

“…Given the high β diversity across this landscape, it appears less likely that capacity for physiological plasticity by fungal individuals or intraspecific variations were drivers of EM fungal community assembly here [ 27 ]. Some controlled, manipulative studies (e.g., reciprocal seedling transplants across soil types; [ 78 ]) could be used to test these capacities more thoroughly.…”