Appendix B. Assessment of the relationship between hemlock crown health and understory light availability.

Assessment of the relationship between hemlock crown health and understory light availability

Appendix B. Propagule pressure results.

Propagule pressure results

Appendix A. Methodological details: site description, vegetation measurements, hemispherical photography, invasibility, and propagule pressure indices.

Methodological details: site description, vegetation measurements, hemispherical photography, invasibility, and propagule pressure indices

Appendix A. Methodological details: site description, propagule pressure indices, and germination rates.

Methodological details: site description, propagule pressure indices, and germination rates

Appendix A. Methodological details.

Methodological details

Appendix B. Summary of exotic plant species cover and density for the 1-m2 monitoring plots of exotic species in 10 hemlock sites in the Delaware Water Gap National Recreation Area (New Jersey and Pennsylvania) in 2003 and 2006.

Summary of exotic plant species cover and density for the 1-m2 monitoring plots of exotic species in 10 hemlock sites in the Delaware Water Gap National Recreation Area (New Jersey and Pennsylvania) in 2003 and 2006

Wason_etal_2017_JApplEcol_data

Datasets on Whiteface Mountain microclimate, tree growth (from permanent plots and tree cores), and plot level basal area and density for dominant tree species

Restoring Soil Calcium Reverses Forest Decline

Forest decline in the northeastern United States has been linked to the effects of acid deposition on soil nutrients. To test this link, we added a calcium silicate mineral to a paired watershed at the Hubbard Brook Experimental Forest, New Hampshire, in an amount designed to gradually replace the estimated amount of calcium lost as a result of human activity in the 20th Century (primarily because of acid deposition). The experimental restoration resulted in a recovery of tree biomass increment. The improved calcium nutrition also promoted higher aboveground net primary production and increased the photosynthetic surface area in the treated watershed relative to that in the reference watershed. These results demonstrated that soil acidification accelerated by acid deposition has contributed to the decline of forest growth and health on naturally acidic soil in the northeastern United States and that decline can be reversed by the addition of calcium

Appendix A. Description of treatments, plot data collection, shrub cover and snag recruitment analyses, and tree vulnerability profile development.

Description of treatments, plot data collection, shrub cover and snag recruitment analyses, and tree vulnerability profile development

High Hydroquinone Emissions from Burning Manzanita

California wildfires are becoming larger and more frequent because of climate change and historical fire suppression. The 2017 fire season was record-breaking in terms of monetary damage, area burned, and human casualties. In addition, roughly 20 million people were exposed to dense wildfire smoke for days. Understanding the health impacts of wildfire smoke requires detailed chemical speciation of smoke produced from different fuels. This study demonstrates the unique chemical fingerprint observed in smoke from burning manzanita, a common chaparral and forest understory shrub found in several ecosystems of California. Burning manzanita during the FIREX Fire Laboratory experiments emitted hydroquinone (1,4-dihydroxybenzene with an emission factor of 0.4 g/kg) and two sterol/triterpenoid tracer compounds at levels up to 100 times higher than those of the other common wildland fuels in California such as pine trees, other shrubs, grasses, and duff. Additionally, these compounds were detected in Berkeley, CA, from smoke produced during the October 2017 wildfires in northern California, a region where manzanita grows. In contrast, the identified fingerprint for manzanita burning emissions was not observed during prescribed fires of a mixed conifer forest in California’s Sierra Nevada, indicating negligible amounts of manzanita were burned. As confirmed by shrub inventory data collected prior to the burns, small amounts of manzanita remain after prescribed burning, a low-severity forest management technique, but larger amounts can occur after recovery from high-severity events like wildfires. Results from this study show that chemical signatures in smoke can be traced back to specific fuels like manzanita and that forest management techniques can be used to limit certain types of wildfire emissions