A primary aim in conservation is to either bolster threatened populations or eradicate invasive ones. Classical elasticity analysis suggests the survival of long-lived adults will have the largest impact on changing population growth, but this result relies on a linear approximation. In reality, the population growth response to perturbing a single demographic rate is nonlinear. We applied exact perturbation analyses to a large database of plant matrix population models in a meta-analysis to determine when and under what conditions population growth may be ‘stabilized’. We found this relationship to be strongly nonlinear, making standard methodology misleading. The vital rate change required for population replacement (λ = 1) is more biased and more likely to fail when mitigating decline as opposed to controlling population expansion. However, these biases and conservation deficits are structured among vital rates and life history strategies. The patterns we describe provide guidance not only for when to expect decits and bias, but also for deciding which vital rates may be most responsive to conservation interventions.

Despite widespread evidence that biological invasion influences both the biotic and abiotic soil environments, the extent to which these two pathways underpin the effects of invasion on plant traits and performance is unknown. Leveraging a long-term (14-yr) field experiment, we show that an allelochemical-producing invader affects plants through biotic mechanisms, altering the soil fungal community composition, with no apparent shifts in soil nutrient availability. Changes in belowground fungal communities result in high costs of nutrient uptake for native perennials and a shift in functional traits linked to their water and nutrient use efficiencies. Some species in the invaded community compensate for high nutrient costs by reducing nutrient uptake and maintaining photosynthesis by expending more water, which demonstrates a trade-off in trait investment. For the first time, we show that the disruption of belowground nutritional symbionts can drive native plants toward novel regions in order to maintain their water and nutrient economics.