Department of Geography, University of California, Santa Barbara, CA 93106;
Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106.
Proc Natl Acad Sci U S A. 2020 Apr 14;117(15):8532-8538. doi: 10.1073/pnas.1917521117. Epub 2020 Mar 30.
Understanding the driving mechanisms behind existing patterns of vegetation hydraulic traits and community trait diversity is critical for advancing predictions of the terrestrial carbon cycle because hydraulic traits affect both ecosystem and Earth system responses to changing water availability. Here, we leverage an extensive trait database and a long-term continental forest plot network to map changes in community trait distributions and quantify "trait velocities" (the rate of change in community-weighted traits) for different regions and different forest types across the United States from 2000 to the present. We show that diversity in hydraulic traits and photosynthetic characteristics is more related to local water availability than overall species diversity. Finally, we find evidence for coordinated shifts toward communities with more drought-tolerant traits driven by tree mortality, but the magnitude of responses differs depending on forest type. The hydraulic trait distribution maps provide a publicly available platform to fundamentally advance understanding of community trait change in response to climate change and predictive abilities of mechanistic vegetation models.
理解现有植被水力特征和群落特征多样性模式背后的驱动机制对于推进陆地碳循环的预测至关重要，因为水力特征会影响生态系统和地球系统对水分变化的响应。在这里，我们利用一个广泛的特征数据库和一个长期的大陆森林样地网络，来绘制不同地区和不同森林类型的群落特征分布变化图，并量化从 2000 年至今美国不同地区和不同森林类型的“特征速度”（群落加权特征的变化率）。我们发现，水力特征和光合特征的多样性与当地水分供应的关系比总体物种多样性更为密切。最后，我们发现有证据表明，由于树木死亡，具有更耐旱特征的群落出现了协同变化，但响应的幅度取决于森林类型。水力特征分布图提供了一个公共可用的平台，从根本上推进了对气候变化下群落特征变化以及机制植被模型预测能力的理解。
