A National Multi-Scale Assessment of Regeneration Deficit as an Indicator of Potential Risk of Forest Genetic Variation Loss

Kevin M Potter,Kurt Riitters

doi:10.3390/f13010019

Abstract

Genetic diversity is essential because it provides a basis for adaptation and resilience to environmental stress and change. The fundamental importance of genetic variation is recognized by its inclusion in the Montréal Process sustainability criteria and indicators for temperate and boreal forests. The indicator that focuses on forest species at risk of losing genetic variation, however, has been difficult to address in a systematic fashion. We combined two broad-scale datasets to inform this indicator for the United States: (1) tree species occurrence data from the national Forest Inventory and Analysis (FIA) plot network and (2) climatically and edaphically defined provisional seed zones, which are proxies for among-population adaptive variation. Specifically, we calculated the estimated proportion of small trees (seedlings and saplings) relative to all trees for each species and within seed zone sub-populations, with the assumption that insufficient regeneration could lead to the loss of genetic variation. The threshold between sustainable and unsustainable proportions of small trees reflected the expectation of age–class balance at the landscape scale. We found that 46 of 280 U.S. forest tree species (16.4%) may be at risk of losing genetic variation. California and the Southeast encompassed the most at-risk species. Additionally, 39 species were potentially at risk within at least half of the seed zones in which they occurred. Seed zones in California and the Southwest had the highest proportions of tree species that may be at risk. The results could help focus conservation and management activities to prevent the loss of adaptive genetic variation within tree species.

Highlights

Genetic diversity within species is essential for populations of living organisms, including forest trees, because it provides the foundation for adaptation and resilience to environmental stresses and changes [1,2,3]
As tree species face severe threats such as climate change [11,12] and insect and disease infestations [13,14,15], the loss of potential future benefit conveyed by genetic diversity could be highly detrimental [16,17]
The fundamental importance of genetic variation is reflected in criteria and indicator (C&I) systems used to track forest sustainability at the national scale

Summary

Introduction

Genetic diversity within species is essential for populations of living organisms, including forest trees, because it provides the foundation for adaptation and resilience to environmental stresses and changes [1,2,3]. Because trees are immobile and long-lived, they are thought to require substantially more genetic variation within their populations than other groups of plants, to enable them to adapt to continually changing environmental conditions [9,10]. As tree species face severe threats such as climate change [11,12] and insect and disease infestations [13,14,15], the loss of potential future benefit conveyed by genetic diversity could be highly detrimental [16,17]. The fundamental importance of genetic variation is reflected in criteria and indicator (C&I) systems used to track forest sustainability at the national scale. Examples include the Forests Europe sustainable forest management C&Is [18] and the Montréal Process Criteria and Indicators for the Conservation and Sustainable Management of Temperate and Boreal Forests [19]

Objectives

Methods

Results

Conclusion