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.

北部的泥炭地通常以高泥质灌木物种为主，后者依靠类胡萝卜菌根真菌（ERM）来获取营养素的有机来源，例如氮（N）和磷（P），并拥有丰富的深色隔生内生菌（DSE）。人为氮和磷的沉积过程中，寄主与真菌共生体之间的关系可能会发生变化。我们研究了氮和磷的添加对两种菊科灌木，菜花愈伤组织和Erica tetralix的长期影响。通过分析根的真菌定植，酶活性和真菌物种组成，在苏格兰的Whim Bog进行了研究。出乎意料的是，典型的ERM细胞内定植的频率没有改变，而ERM菌丝的发生趋于增加而DSE菌丝的发生却趋于减少。我们的研究结果表明，改变的养分限制改变了根系相关的真菌定植模式，并影响了菊科根系酶的活性，从而影响了分解潜力。黑色素化DSE中顽固型真菌生物量的减少可能对添加养分的泥炭地碳固存有影响。