DOI: 10.5061/dryad.kf575
title: Data from: From the individual to the landscape and back: Time-varying effects of climate and herbivory on tree sapling growth at distribution limits

description: 1. As herbivory can modulate climate-induced shifts in species
 distribution, disentangling the relative importance of herbivory and
 climate on plant growth can help to predict and manage future changes in
 vegetation, such as those occurring at treeline areas. 2. An
 individual-based hierarchical Bayesian time-series model (Individual-Based
 Model; IBM) was developed to estimate the time-varying impact of climate
 and herbivory on individual pine-sapling height growth in woodland and
 treeline ecosystems of Southern Europe during a 16-year period. The
 performance of the IBM was compared to a Linear Mixed-Effects (LME) model
 to test for potential inferential effects when individual variability is
 marginalized. Time-varying models were also compared to constant parameter
 approaches. 3. Model fitting and posterior predictive checking suggests a
 better statistical performance of individual-scale, time-varying
 inference. LME modeling overestimated herbivory effects and underestimated
 environmental stochastic effects, and model validation indeed suggested
 severe overfitting in the LME model relative to the IBM strategy. These
 results reveal a potential failure of common aggregation strategies to
 correctly resolve the effects of climate and herbivory variability at the
 individual scale. Moreover, ignoring the time-varying nature of the
 effects may preclude the correct estimation of the temporal scale of
 climate and herbivory impacts. 4. In general, we found stronger
 individual- and time-averaged effects of summer precipitation relative to
 the effects of herbivory, particularly at the treelines. Also, individual
 pines responses showed effects of the same sign more consistently in the
 case of precipitation. This suggests that precipitation is more pervasive
 at the population level, while herbivory act as a spatially aggregating
 force through individual-level damage. 5. Synthesis. Our results suggest
 that accounting for individual and temporal variability in ecological
 inference greatly improve the assessment of the relative importance of
 climate and herbivory on species distribution shifts. Strong effects of
 precipitation at the treeline could allow tree upward expansion, although
 increasing ungulate populations and associated browsing damages might
 limit positive climatic responses of pine-saplings in the near future. In
 this context, the spatially heterogeneous effect exerted by herbivory
 could result in diverse vegetation structures in ecotones, adding a new
 dimension to the predictions on climate-driven vegetation shifts.
description: Precipitation, herbivory
 intensity and pine sapling height growthThe dataset contain
 Relative Height Growth (RHG) and age of 234 pine saplings of Pinus
 sylvestris and P. nigra in two native forests of Southern Europe during
 the period 1993-2008, both at treeline and woodland areas. Red deer
 (Cervus elaphus) abundance and summer (June, July and August) total
 precipitation data of the study area (Sierra de Baza Natural Park, SE
 Spain) are included, as well as herbivory intensity (percentage of
 saplings suffering leader browsing) recorded in sampled plots for the
 study period.Dataset.csv