干旱区生态环境知识资源中心

Predicting ecological responses to a changing climate is becoming a critical tool to inform natural resource management efforts. Within Joshua Tree National Park (JTNP), Joshuatrees (Yucca brevifolia) reach their southern-most distribution. Previous research modeling distributional shifts of Joshuatrees in response to climatechange have been conducted at large regional scales, predicting widespread extirpation of Joshuatrees from their current southern and central distribution. Here we employed the Mahalanobis D-2 statistic and constructed a finer-scale model of the Joshuatree’s current distribution within and surrounding JTNP, and then assessed their sensitivity to a gradient of climatechange scenarios. Local scale analyses may identify local adaptations and climate-change refugia, a result which may not be possible with larger scale analyses. Under the most severe climate scenario we modeled (a 3 degrees C increase in mean July maximum temperature) there was a 90% reduction in their current distribution, nevertheless a refugium of suitable Joshuatree habitat still remained within JTNP. A niche model for juvenile Joshuatrees revealed a near match with the boundary of the +1 degrees C shifted adult model providing a level of model validation, consistent with a hypothesis that early levels of climatechange may have already had an impact on Joshuatree recruitment. The match of juvenile Joshuatrees provides support for the findings of our climate-shifted niche models for the future distribution of this species within JTNP. This analysis represents a more optimistic scenario than previously published models of climate change impacts on Joshuatrees.