Primary net productivity and biomass quality as drivers of herbivory rate at the regional scale.

ENRICO L.; DÍAZ S

Chania, Grecia

Simposio; 52 Symposium of the International Association for Vegetation Science,; 2009

International Association for Vegetation Science,

There has been much discussion on the factors driving herbivory at the broad (regional to trans-regional) scale. There is no consensus about the main factor influencing herbivory rate.  We proposed a  hypotethical model of  relationships  between PPNA, quality and  herbivory. W e sampled 9 ecosystems including arid shrublands, grasslands, dry forests and savannahs. In each ecosystem we identified 10 plots subjected to both vertebrate and invertebrate herbivory, and 10 plots excluded from vertebrate herbivores. In each ecosystem, and in all plots we measured 7 leaf traits on the 10 most abundant species, as indicators of biomass quality: - content of carbon (C), - nitrogen (N), and phosphorous (P), - tensile strength (LTS) and specific area (SLA).   In order to estimate herbivory rate, we tagged intact fully-expanded young leaves of the 10 dominant plant species, and measured % leaf area removed by vertebrates or invertebrates (%H-V and %H-I respectively) during a standard period of time. In general, we found that, at ecosystem level, %H was mainly associated to ANPP, and secondly to the same functional leaf traits associated to ANPP along the gradient (SLA and P content). However, as this last relationships were strongly driven by the values found at the extremes of the gradient, when analizing consumption patterns in  the context of our proposed model we cannot fully support the proposed model. Our results suggest complex interactions between herbivory controls at the within- and among-ecosystem scales.