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As temperatures rise, plants are expected to shift their ranges to align with their abiotic niches. If plants do not encounter suitable mycorrhizal fungi in new habitats, however, these migrations may fail. We review the literature to describe how arbuscular mycorrhizal (AM) fungi, ectomycorrhizal (EM) fungi, and ericoid mycorrhizal (ErM) fungi currently vary within and beyond host plants’ ranges and how these mycorrhizal fungi shape plant ranges. We introduce a framework that predicts when plants are likely to encounter suitable mycorrhizal mutualists in new habitats. Critically, the probability of beneficial plant-mycorrhizal fungal interactions depends on 1) plants’ specificity to mycorrhizal fungi, 2) abiotic distance between historic and new ranges, 3) plants’ relatedness to new range plants, 4) geographic distance between historic and new ranges, and 5) the alignment of plant and mycorrhizal fungal niches, all of which are moderated by mycorrhizal guild. Finally, we review research frontiers in the field of plant-mycorrhizal fungal interactions. 

Quantifying nitrogen uptake rates across different forest types is critical for a range of ecological questions, including the parameterization of global climate change models. However, few measurements of forest nitrogen uptake rates are available due to the intensive labor required to collect in situ data. Here, we seek to optimize data collection efforts by identifying measurements that must be made in situ and those that can be omitted or approximated from databases. We estimated nitrogen uptake rates in 18 mature monodominant forest stands comprising 13 species of diverse taxonomy at the Morton Arboretum in Lisle, IL, USA. We measured all nitrogen concentrations, foliage allocation, and fine root biomass in situ. We estimated wood biomass increments by in situ stem diameter and stem core measurements combined with allometric equations. We estimated fine root turnover rates from database values. We analyzed similar published data from monodominant forest FACE sites. At least in monodominant forests, accurate estimates of forest nitrogen uptake rates appear to require in situ measurements of fine root productivity and are appreciably better paired with in situ measurements of foliage productivity. Generally, wood productivity and tissue nitrogen concentrations may be taken from trait databases at higher taxonomic levels. Careful sorting of foliage or fine roots to species is time consuming but has little effect on estimates of nitrogen uptake rate. By directing research efforts to critical in situ measurements only, future studies can maximize research effort to identify the drivers of varied nitrogen uptake patterns across gradients.