Abstract
Northern peatlands are often dominated by ericaceous shrub species which rely on ericoid mycorrhizal fungi (ERM) for access to organic sources of nutrients, such as nitrogen (N) and phosphorus (P), and host abundant dark septate endophytes (DSE). Relationships between hosts and fungal symbionts may change during deposition of anthropogenic N and P. We studied the long-term effects of N and P addition on two ericaceous shrubs, Calluna vulgaris and Erica tetralix, at Whim Bog, Scotland by analyzing fungal colonization of roots, enzymatic activity, and fungal species composition. Unexpectedly, the frequency of typical ERM intracellular colonization did not change while the occurrence of ERM hyphae tended to increase and DSE hyphae to decrease. Our findings indicate that altered nutrient limitations shift root associated fungal colonization patterns as well as affect ericaceous root enzyme activity and thereby decomposition potential. Reduction of recalcitrant fungal biomass in melanized DSE may have implications for peatland C sequestration under nutrient addition.
Highlights
Peatlands in the Northern hemisphere are often nutrient poor eco systems characterized by acidic, anoxic, water saturated conditions with considerable nitrogen (N) and phosphorus (P) limitations (Aerts et al, 2001)
Ericaceous shrubs are largely dependent on ericoid mycorrhizal fungi (ERM) to provide access to organic N and P which they provide in ex change for photosynthetic carbon (C) from the host plant (Smith and Read, 2008)
The increases in overall fungal colonization for both Calluna vulgaris and Erica tetralix under nutrient addition were unexpected and the un changed frequency of ERM intracellular coiling showed that long-term N and NPK addition did not reduce mycorrhizal colonization
Summary
Peatlands in the Northern hemisphere are often nutrient poor eco systems characterized by acidic, anoxic, water saturated conditions with considerable nitrogen (N) and phosphorus (P) limitations (Aerts et al, 2001). The ERM fungi are capable of accessing organic N and P via a large variety of degradative enzymes which act primarily on plant cell wall components (Perotto et al, 2018), demonstrating a potential versatility more comparable to saprotrophs than to other types of mycorrhizae. These ericaceous species are host to abundant dark septate endophytes (DSE) with extracellular enzyme capabilities potentially capable of improving host nutrient uptake (Mandyam and Jumpponen, 2005, 2014; Upson et al, 2009)
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