Spatial variability in foliar carbon and nitrogen isotope values on Tenerife reflects both climate and soils: Establishing a framework for future work

Abstract

Tenerife Island is well-known for its biodiversity. It boasts the highest elevation in the Atlantic Ocean and its northern and southern slopes have varying moisture and temperature gradients. Consequently, there are multiple spatially discrete vegetation zones, or biomes, recognized on the island that roughly follow elevation. We investigated the extent to which climatic variables as well as soil nitrogen isotope values (δ15N) and weight %N influence spatial isotopic variability in C3 plants during the rainy season and assessed the degree to which foliar carbon isotope discrimination (Δleaf) and δ15N values are able to distinguish biomes. Mean Annual Precipitation explained 71% and 55% of the spatial variability in Δleaf and δ15N values, respectively. Overall, foliar δ15N values tracked those in soils, and soil %N was negatively correlated with both soil and foliar δ15N values. However, there was considerable variability among co-occurring species, as well as among sites within the same biome, which obscured trends among biomes. As a result, only a few biomes were isotopically distinct: Broad-leaved evergreen forest and sub-desert coastal scrub on the northern slope, and summit scrub and sub-desert coastal scrub on the southern slope. Further investigation into the influence of coastal orientation, topography, plant physiology, soil characteristics, as well as seasonal and inter-annual climate variability on foliar isotope values would be fruitful. Nevertheless, these results provide baseline information for researchers seeking to interpret diet and mobility of animals and people, as well as environmental changes over time on Tenerife and other Macaronesian volcanic islands.