DOI: 10.5061/dryad.31887
title: Data from: Woodland resilience to regional drought: Dominant controls on tree regeneration following overstorey mortality

description: Drought events occurring under warmer temperatures (i.e. “hotter
 droughts”) have resulted in widespread tree mortality across the globe,
 and may result in biome-level vegetation shifts to alternate vegetation
 types if there is a failure of trees to regenerate. We investigated how
 overstorey trees, understorey vegetation, and local climatic and edaphic
 conditions interact to influence tree regeneration, a key prerequisite for
 resilience, in a region that has experienced severe overstorey tree
 mortality due to hotter droughts and beetle infestations. We used detailed
 field observations from 142 sites that spanned a broad range of
 environmental conditions to evaluate the effects of climate and recent
 tree mortality on tree regeneration dynamics in the spatially extensive
 piñon (Pinus edulis)-juniper (Juniperus osteosperma, Juniperus monosperma)
 woodland vegetation type of the southwestern USA. We used a structural
 equation modelling framework to identify how tree mortality and local
 climatic and edaphic conditions affect piñon and juniper regeneration and
 electivity analyses to quantify the species-specific associations of tree
 juveniles with overstorey trees and understorey shrubs. Piñon regeneration
 appears to be strongly dependent upon advanced regeneration, (i.e. the
 survival of juvenile trees that established prior to the mortality event),
 the survival of adult seed-bearing trees (inferred from basal area of
 surviving trees) and the facilitative effects of overstorey trees for
 providing favourable microsites for seedling establishment. Model results
 suggest that local edaphoclimatic conditions directly affected piñon and
 juniper regeneration, such that stands with hotter, drier local climatic
 conditions and lower soil available water capacity had limited tree
 regeneration following large-scale dieback. Synthesis. We identify four
 indicators of resilience to hotter drought conditions: (1) abundant
 advance regeneration of tree seedlings; (2) sufficient canopy cover for
 survival of emergent seedlings and existing regeneration; (3) sufficient
 seed source from surviving trees with high reproductive output; (4) areas
 with cooler and wetter local climates and greater soil available water
 capacity. In the absence of these conditions, there is greater likelihood
 of woodlands transitioning to more xeric vegetation types following
 dieback.
description: data_summary_dryadThis spreadsheet provides data on tree juvenile density, woodland structure (tree density, tree mortality, etc.), vegetation cover, and abiotic characteristics for each site. For a description of each column on this spreadsheet, please see the metadata file titled, 'data_summary_dryad_metadata'. These data were used in all structural equation modeling in the associated manuscript.nurse_data_dryadThis spreadsheet provides data on how many juveniles were found in each microsite, including units. For a description of each column on this spreadsheet, please see the metadata file titled, 'nurse_data_dryad_metadata'. These data were used in the interaction (also referred to as electivity) analyses in the associated manuscript.data_summary_dryad_metadataThis spreadsheet provides a written description of each column in the spreadsheet titled, 'data_summary_dryad', including the units.nurse_data_dryad_metadataThis spreadsheet provides a written description of each column in the spreadsheet titled, 'nurse_data_dryad', including the units. These data also note which columns were not used in any of the analyses.