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To stem catastrophic wildfires and create firebreaks, whole Pinus edulis and Juniperus osteosperma trees are being mechanically shredded into coarse woody debris (CWD) and deposited on soils previously exposed to decades of tree-induced changes creating “tree-islands of fertility.” To investigate the unknown consequences of CWD on the availability of essential nutrients for establishing grass species, we evaluated the N transformation rates and P availability in interspace and Pinus and Juniperus tree-island (i.e., soils beneath the canopy and at the edge of the canopy) surface soils exposed to field CWD manipulation in over forty cold deserts. Also, in conjunction with our nutrient measurements, we evaluated the frequency of three exotic grasses and thirty-five native grasses to identify links between N and P dynamics. The addition of CWD decreased N mineralization and nitrification rates in tree-island edge soils but increased N mineralization in interspace soils. CWD enhanced the availability of P in all soils with the greatest percent increase occurring in canopy (36%), followed by canopy edge (26%), and finally interspace (17%) soils. The frequency of perennial native grasses, especially Elymus elymoides and Psuedoroegneria spicata, was at least 70% higher under CWD additions in all soils. Also, the frequency of perennial exotic grasses and Bromus tectorum was higher under CWD additions in interspace and tree-island edge soils. Our results suggest that inorganic N availability was directly depressed by CWD as microbes potentially coped with the addition of more woody recalcitrant C sources by scouring soils for N, but also indirectly enhanced as the higher grass frequencies in interspace soils supplied microbes with more labile C substrates stimulating N to mineralize. Ultimately, CWD additions increased the availability of N and P and native and exotic grasses indiscriminately used these nutrients alike.