Species distribution models predict temporal but not spatial variation in forest growth

Abstract

Bioclimate envelope models have been widely used to illustrate the discrepancy between current species distributions and their potential habitat under climate change. However, the realism and correct interpretation of such projections has been the subject of considerable discussion. Here, we investigate whether climate suitability predictions correlate to tree growth, measured in permanent inventory plots and inferred from tree‐ring records. We use the ensemble classifier RandomForest and species occurrence data from ~200,000 inventory plots to build species distribution models for four important European forestry species: Norway spruce, Scots pine, European beech, and pedunculate oak. We then correlate climate‐based habitat suitability with volume measurements from ~50‐year‐old stands, available from ~11,000 inventory plots. Secondly, habitat projections based on annual historical climate are compared with ring width from ~300 tree‐ring chronologies. Our working hypothesis is that habitat suitability projections from species distribution models should to some degree be associated with temporal or spatial variation in these growth records. We find that the habitat projections are uncorrelated with spatial growth records (inventory plot data), but they do predict interannual variation in tree‐ring width, with an average correlation of .22. Correlation coefficients for individual chronologies range from values as high as .82 or as low as −.31. We conclude that tree responses to projected climate change are highly site‐specific and that local suitability of a species for reforestation is difficult to predict. That said, projected increase or decrease in climatic suitability may be interpreted as an average expectation of increased or reduced growth over larger geographic scales.

Historical and event‐based bioclimatic suitability predicts regional forest vulnerability to compound effects of severe drought and bark beetle infestation

“…This would agree with the interpretation that directional acclimation and increasing stand density under favorable, climatically stable conditions could increase vulnerability when unfavorable extreme conditions occur due to higher hydraulic failure (Anderegg, Schwalm et al, 2015) or competition . Likewise, vulnerability in P. edulis populations living near climatically unsuitable, highly variable edges endorses the relevance of the cumulative effects of past extreme events (Lloret et al, 2004) likely due to a depletion of stored reserves (Dickman, McDowell, Sevanto, Pangle, & Pockman, 2015) or the loss of meristems that allow regrowth (Zeppel et al, 2015).…”

“…Positive effects of HCS-SD on die-off would indicate increased population vulnerability in highly fluctuating climatic environments, heightening the cumulative effects of past deleterious periods (Anderegg, Schwalm et al, 2015;Lloret, Siscart, & Dalmases, 2004), despite the transitory recovery of suitable conditions. Interaction of HCS-SD with HCS would indicate whether climatic core or edge populations are more or less vulnerable to past bioclimatic variability, while interaction with ECS would indicate a reinforcing mechanism between past and current events.…”

Multi‐variable approach pinpoints origin of oak wood with higher precision

“…Environmental information on growing conditions as stored in tree rings is widely used to predict growth responses of trees to climate change (Holz et al, 2018;Williams, Michaelsen, Leavitt, & Still, 2010), to model potential future species distribution (Gutiérrez, Snell, & Bugmann, 2016;van der Maaten et al, 2017), to quantify forest resistance to drought events (Gazol, Camarero, Anderegg, & Vicente-Serrano, 2017) and to reconstruct growth-limiting climate factors during the pre-instrumental period (Čufar, De Luis, Zupančič, & Eckstein, 2008;Rydval et al, 2017;Schofield, Barker, Gelman, Cook, & Briffa, 2016). Information on spatial variation of climatic signals in tree rings is also important for archaeological and historical studies, as it serves as a basis for dating and determining the geographical origin of historical timbers ("dendroprovenancing") (Speer, 2010).…”

Intra-annual stem size variations converge across marginal populations of European beech

“…Given the forecasting climate change and resulting shift of ecological niches, the beech is expected to expand not only beyond its current north-eastern, but also south-eastern distribution margin (Saltré et al 2015;van der Maaten et al 2017). Moreover, the ongoing changes in environmental conditions could affect more dramatically the populations located at the boundary of the species distribution.…”