Space‐for‐time inferences about range‐edge dynamics of tree species can be influenced by sampling biases. (9th February 2021)

• Record Type: Journal Article
• Authors: Ni, Ming; Vellend, Mark
• Is Part Of: Global change biology. Volume 27:Number 10(2021)
• Page Start: 2102
• Page End: 2112
• Publication Date: 2021-02-09
• Subjects: climate change -- forest inventory and analysis -- ontogenetic shift -- sapling -- space‐for‐time -- tree migration; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.15524
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Differences between the distributions of tree saplings and adults in geographic or niche space have been used to infer climate change effects on tree range dynamics. Previous studies have reported narrower latitudinal or climatic niche ranges of juvenile trees compared to adults, concluding that tree ranges are contracting, contradicting climate‐based predictions. However, more comprehensive sampling of adult trees than juvenile trees in most regional forest inventories could potentially bias ontogenetic comparisons. Here we first report spatial simulations showing that reduced sampling intensity can result in underestimates of range and niche limits, but that resampling the same number of individuals of different life stages can eliminate this bias. We then reanalyzed the U.S. Forest Inventory and Analysis data, comparing the range and niche limits between adult trees and saplings of 92 tree species, both using the original data and two resampling procedures. Resampling aimed to reduce sampling biases by controlling for either sampling area or the number of individuals sampled. Overall, these resampling procedures had a major influence on the estimation of range limits, most often by reducing, eliminating, or even reversing the tendency in the original analyses for saplings to have broader distributions than adult trees. These results indicate that previous conclusions that the distributions of juvenile trees were contracting in response to climate change were potentially artifacts of sampling in the underlying data. More generally, sampling effects involved in the estimation of geographic ranges and environmental niche widths need to be taken into account in studies comparing different life stages, and also likely in other types of distribution comparisons. Abstract : Previous studies have concluded that the geographic ranges of tree species are contracting, based on evidence of narrower latitudinal limits of juvenile trees compared to adults. These results run contrary to predictions based on climate warming, but the juvenile versus adult comparisons might be biased by more comprehensive sampling of adults. Using spatial simulations, we found that reduced sampling intensity resulted in underestimates of range limits. Reanalyses of U.S. Forest Inventory and Analysis data (correcting for biases) eliminated, or even reversed the original results, indicating that previous conclusions of tree range contraction were potentially artifacts of sampling.