Postfire Restoration Framework For National Forests In California

Author : Derek Jon Nies Young
Publisher :
ISBN 13 : 9780355969122
Total Pages : pages
Book Rating : 4.9/5 (691 download)

DOWNLOAD NOW!

Download or read book Post-fire Forest Recovery and Restoration in a Changing Climate written by Derek Jon Nies Young and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Yellow pine and mixed-conifer (YPMC) forests in California are subject to multiple anthropogenic pressures, including fire suppression and climate change. Although YPMC forests historically experienced a high-frequency, low-severity fire regime, fire suppression has resulted in increased fuel loads and has therefore increased the severity of the fires that do occur. Some of the historically dominant tree species in YPMC forests, particularly pines (Pinus spp.), establish primarily following wildfire. However, the increasing extent of severely-burned areas with few nearby seed sources for conifer regeneration has resulted in poor post-fire tree recruitment across large areas. Climate change has the potential to further substantially alter post-fire regeneration patterns. When post-fire tree regeneration is poor, managers often plant tree seedlings in order to speed forest recovery. However, little is known about (a) how natural post-fire tree regeneration patterns may change as climate changes and (b) how appropriate seed sources for post-fire tree seedling plantings should be selected. Further, despite the fact that most studies of climate change impacts rely on modeled climate variables when examining the relationship between climate and vegetation, there has been little critical evaluation of several important climate variables that are increasingly used in ecological analyses. I address these knowledge gaps in this dissertation. In Chapter 1, I evaluate some central assumptions that are made when modeling climatic water balance variables including actual evapotranspiration (AET) and climatic water deficit (CWD). I find that the assumptions can substantially affect both the absolute and relative values of modeled AET and CWD across landscapes—as well as the inferences drawn from ecological analyses that apply the variables—despite the fact that there is no practical means for avoiding the need to make assumptions. Representing the hydrological climate using simple precipitation variables may introduce less bias than using AET and CWD. In Chapter 2, I use recent interannual variation in precipitation to evaluate the sensitivity of post-fire tree recruitment to changes in precipitation patterns. I find that while post-fire recruitment of some conifer species is reduced—and recruitment of shrubs increased—under post-fire drought, the response of post-fire tree seedling species composition to weather variation is constrained by the species composition of the surrounding unburned forest. Forest tree community composition thus may not rapidly shift as climate changes. Finally, in Chapter 3, I test the application of assisted gene flow—the managed relocation of genotypes within the species’ range—in large-scale post-fire restoration plantings. I find that in the short term, under anomalously hot and dry conditions, trees grown from seed collected at elevations below the planting site generally perform as well as, if not significantly better than, trees grown from seed collected near the planting site. However, challenges specific to large-scale restoration projects—in particular, the use of seed collections that are not geographically precise—can complicate selection of appropriate provenances and lead to unexpected results. Overall, the work in this dissertation contributes to increased potential to understand and predict the natural response of forest ecosystems to climate change and to update management practices in response to changes in climate.