Journal Article plant radiations priority effects Flow-IR Research Support, Non-U.S. Gov't Soil alpine ecosystems anthropogenic disturbance benchtop NMR climatic gradients community assembly disturbance environmental filtering functional traits immigration timing lineage diversification low-field NMR niche conservatism niche occupancy niche preemption nonnative species palaeogeography phylogenetic clustering process analytical technology reaction monitoring root porosity soil resource availability stress gradient hypothesis