Spatial and seasonal patterns of insect herbivory in southern beech (Nothofagus) Patagonian forests

MAZÍA, C.N.; CHANETON. E.C.; KITZBERGER, T.

Leipzig, Alemania

Conferencia; 4th International Canopy Conference “Tropical versus Temperate Forests”; 2005

University of Leipzig, Institute of Botany

Theory suggests that niche differentiation patterns and species coexistence are strongly influenced by spatial and temporal heterogeneity in habitat conditions. In the context of traditional community ecology,  negative trophic interactions (competition) were proposed as a central force structuring insect communities. More recently,  have been suggested that insects could compete indirectly, via plant response to herbivory. In this study,  we examined spatial and seasonal patterns of foliar damage by different insect feeding guilds in Nothofagus pumilio (‘lenga’) forests located at both ends of a steep precipitation gradient (800–3000 mm/yr) in northern Patagonia, Argentina. We found higher maximum levels of herbivory in dry (25%) than in wet (5%) forests. Insect leaf miners and leaf tiers accounted for 80% of total damage in the dry forests, whereas leaf chewers and skeletonizers produced most damage (75%) in the wet forests. Dry forests showed a remarkable seasonality in leaf damage patterns; leaf miners dominated during the early season, with a peak in midseason (January), while leaf tiers only appeared in February and dominated towards the end of the season (April). Such temporal separation did not occur in the wet forest, where herbivory tended to increase throughout the season. Insect damage decreased in February, when early absicion of damaged leaves and leaf expansion from a second flush counteracted prior damage. We conclude that habitat heterogeneity, leaf phenology, and life-history attributes of feeding guilds may help to explain the spatial (gradient scale) and temporal (stand scale) patterns of resource use by foliar insects in these Nothofagus forests.