Climate Impacts on Tree Growth in the Sierra Nevada

Mélaine Aubry-Kientz,Emily Moran

doi:10.3390/f8110414

Abstract

Rising temperatures and aridity may negatively impact tree growth, and therefore ecosystem services like carbon sequestration. In the Sierra Nevada in California, annual variation in precipitation is high, and forests have already been impacted by several recent severe droughts. In this study, we used growth census data from long-term plots in the Sierra Nevada to calibrate an annual climate-dependent growth model. Our results highlight a high diversity of responses to climate, although the effects of climate are small compared to those of tree size and competition. Some species grow less during dry years (Pinus contorta and Calocedrus decurrens) but, surprisingly, other species exhibit higher growth during dry years (Pinus monticola, Abies magnifica, Pinus jeffreyi, Quercus kelloggii). These results emphasize the need for growth models to take into account species variability, as well as spatial heterogeneity, when studying mixed conifer forests. So far, temperatures have increased in California, and tree growth of some species may drastically decrease in the Sierra Nevada if warming continues, leading to changes in forest structure and composition as well as potential changes in wood production and carbon sequestration.

Highlights

Forest dynamics are strongly affected by climate [1,2,3,4,5,6] and, as climate continues to change, impacts on forests are likely to be profound [7,8]
We considered that the climate variable had an impact on growth when the 95% confidence interval of parameter β 3 of Equation (2)
Our study provides new information about the relationship between annual tree growth and climate because previous dendrochronological studies in the Sierra Nevada have focused on fewer species (3–5) and diameter classes [37,38,39,58]

Summary

Introduction

Forest dynamics are strongly affected by climate [1,2,3,4,5,6] and, as climate continues to change, impacts on forests are likely to be profound [7,8]. The forests of the Sierra Nevada in California are exposed to a Mediterranean climate, with little or no precipitation during summer Longer and drier summers can lead to severe drought. Average temperatures and precipitation patterns in California have already shifted since the beginning of the 20th century [10]. Future climate in the Sierras is predicted to be warmer, with an average increase in annual temperature ranging from 1.35 to 2 ◦C by mid-century and summer temperature increases that are equal to or greater than increases in winter temperatures [13,14]. Projections of annual precipitation for 2060–2069 vs 1985–1994 range from −23% to 9% in the Sierra Nevada [13]

Methods

Discussion

Conclusion