Joint Biotic and Abiotic Spatial Turnover: A Basis for Modelling
Ecosystem Pattern at Landscape Extents
Abstract
Ecosystem models are typically built to predict patterns of one or more
ecosystem properties, and those properties are often biotic. While some
ecosystem models incorporate either biotic and abiotic responses, biotic
and abiotic variables are rarely applied jointly as responses in
ecosystem models. Here we model continuous spatial turnover among 21
biotic and abiotic properties to explore forest ecosystem patterns
across landscapes of Nova Scotia, Canada (55 000 km2) at high (10 x 10
m) resolution. To achieve this objective, we fit generalized
dissimilarity models to field collected data on biotic and abiotic
response variables and geographic and environmental gradients described
by remotely sensed predictor variables. We develop three separate models
targeting ecosystem, biotic, and abiotic responses to identify
relationships among forest ecosystem properties, across levels of
ecological organization. Our final ecosystem, abiotic, and biotic models
explained 41.4, 29.03, and 50.9 percent of variance. Vegetation-based
predictors were the most significant for our ecosystem and biotic
response models, while topographic and hydrological predictors were
foremost in our abiotic response model. We show how relationships among
biotic and abiotic ecosystem properties collectively give rise to
predicted patterns of forest ecosystem heterogeneity across Nova Scotia,
with the strongest variations occurring along elevational and
north-south gradients. Our emphasis on multiple ecosystem properties,
and our simultaneous modelling of both biotic and abiotic responses,
including ecosystem structural, compositional, and functional variables,
differs from the approaches taken in most spatial ecosystem models. This
study provides an analytical road map for scientists and conservation
practitioners looking to predict continuous variation in ecosystem
makeup and to apply those predictions for mapping emergent spatial
ecosystem patterns. Such spatial models of ecosystem pattern are crucial
for achieving national and sub-national commitments to global ecosystem
conservation targets.