Provenance Geographical and Climatic Characteristics Influence Budburst Phenology of Southwestern Ponderosa Pine Seedlings

Aalap Dixit,Thomas Kolb,Owen Burney

doi:10.3390/f11101067

Abstract

Ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) forests of the southwestern US are threatened by climate change and deforestation. Information about geographic patterns of provenance variation in budburst phenology is needed to make decisions about selecting seed sources for future planting. In this study, provenance variation in the budburst phenology of ponderosa pine seedlings was examined using common garden studies. Seedlings from 21 provenances, representing an elevational gradient in Arizona and New Mexico, were planted in July 2018 at a ponderosa pine-dominated field site in northern Arizona. Field budburst was monitored weekly on all seedlings in the spring of 2019. Field budburst was compared with budburst timing of the same provenances measured under greenhouse conditions. The hypotheses for this study were that (1) budburst varies among provenances, with earlier budburst in low-elevation provenances, and (2) differences in budburst timing among provenances are consistent for seedlings grown in greenhouse and field environments. Field results show that provenances vary in budburst date and that low- and middle-elevation provenances break bud sooner than high-elevation provenances. Field budburst date had a moderate, positive correlation with provenance mean annual precipitation (r = 0.522) and a moderate, negative trend with latitude (r = −0.413). Budburst date of provenances in the greenhouse had a moderate, positive trend with budburst date in the field (r = 0.554), suggesting application of greenhouse results to field plantings. Such information about provenance variation and environmental and geographic trends in budburst timing will be useful for developing species-specific seed transfer guidelines and effective assisted migration strategies in a changing climate.

Highlights

Tree species have considerable genetic variation among provenances and are generally adapted to local climate [1,2]
The goal of this study was the hypotheses that (1) timing of budburst would vary among provenances in a field planting, to test the hypotheses that (1) timing of budburst would vary among provenances in a field planting, and low-elevation provenances would break bud sooner because budburst timing is often genetically and low-elevation provenances would break bud sooner because budburst timing is often genetically controlled and associated with spring frost hardiness [30,31]; and (2) provenance variation in budburst controlled and associated with spring frost hardiness [30,31]; and (2) provenance variation in timing measured under field conditions would be related to budburst timing of the same provenances budburst timing measured under field conditions would be related to budburst timing of the same measured under greenhouse conditions
Budburst timing varies among provenances of southwestern ponderosa pine

Summary

Introduction

Tree species have considerable genetic variation among provenances and are generally adapted to local climate [1,2]. Due to the inability to adapt or acclimate to rapid climatic change and associated disturbances. Forests of the southwestern US are already experiencing increases in warming, drought, and tree-killing disturbances [5]. An increase in temperature of over 1 ◦ C occurred in the southwestern US between. 2001–2010, and mean annual temperature is expected to increase between 3 and 5 ◦ C by the end of this century [6]. Climate warming has already caused an earlier onset of spring in western North America forests [7,8] because tree budburst timing responds to many factors including temperature [9].

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