Nutrient addition increases insect herbivory in Nothofagus antarctica on North-Patagonian forests

Abstract

The change in nutrient availability in the soil can affect key functions of forest ecosystems, suchas insect herbivory. Although insect herbivory is particularly relevant because it can impact onthe growth and mortality of forest plant species, the evidence of the impacts of fertilizersaddition on herbivory patterns is limited. In this study, we specifically evaluated how herbivoryfrequency on the timber species Nothofagus antarctica is affected by the addition of nitrogen(N), phosphorus (P), potassium (K) and their combinations to the soil, using a long term full-factorial field experiment in a North-Patagonian Forest (Argentina). Our study investigated theeffects of fertilizers (N, P, and K) on herbivory frequency and leaf nutrient concentrations of thestudied species. We found that the addition of fertilizers to the soil increased herbivoryfrequency, which was mediated by increases in leaf nutrient concentrations. Furthermore, weobserved that interactions between fertilizers in leaf nutrient concentrations generally producedincreases in herbivory, both in the amount of leaf consumed and in the foliar damagepercentage. These findings suggest that fertilization can have complex effects on plant-herbivore interactions, and that the specific effects may depend on the identity of the nutrientsthat combined, the plant species, and the level of nutrient availability. Our results provideevidence that changes in soil nutrient availability are important in forest ecosystems, and thatshould be considered to develop effective management strategies for the sustainable use ofnatural resources in Patagonian forests.