Plant biomass
The aboveground vegetation was sampled in two 0.25m2quadrats per plot in September 2010 and 2021. Species richness and abundance were monitored based on the number of individuals per species (a ramet was regarded as an individual for clonal species). Individual plants in each quadrat were clipped for biomass assessment.Eucalyptus nutans height was measured on three randomly selected individuals in each quadrat. Concurrent with the aboveground vegetation sampling, three soil cores (diameter, 3.8cm; depth, 25cm) were taken randomly from each plot. The roots were removed using a 1-mm sieve and washed to measure root biomass. Shoot and root samples were dried at 80°C for 48h, and weighed. The dry plant samples were ground to a fine powder to determine the tissue N contents.