If a toxic pollutant or nutrient imbalance were to blame for the decline, a correlation between bigleaf maple and decline and elemental concentrations should be found. Leaf samples from healthy and declining trees, and soil samples from healthy and declining plots, were analyzed to determine elemental concentrations. Soil and leaf samples used for elemental concentration analysis. Decline was also found to be present across age and size classes. The use of randomized plots selected without bias were critical in efforts to correlate decline with environmental variables or conditions.īy combining these measurements with National Land Cover Database and PRISM Climate Data, it was found that decline in bigleaf maple was associated with increased human development, proximity to roadways, as well as hotter, drier summers. In addition to resampling the original DNR survey locations, which were chosen specifically because they contained declining bigleaf maple, randomized plots on public lands were included. The research project at the University of Washington involved sampling forest plots throughout the range of bigleaf maple in Washington state, during the summer of 2017, and taking measurement and observations of the plot, including the health of the bigleaf maple within the plot. With funding from the USDA NIFA McIntire-Stennis Cooperative Forestry Program, scientists from the University of Washington investigated the spatial patterns and environmental variables associated with decline, while the DNR forest pathologists continued searching for a pathogen responsible for the decline. Leaf hoppers have also been found on bigleaf maple trees, but they have not yet been conclusively linked to decline either. There was some initial interest in Xylella fastidiosa, but subsequent tests gave inconclusive results. Initial surveys did find several pathogens, such as Phytophthora, Armillaria, Neonectria, Nectria, and Ganoderma, but none were found in enough of the declining bigleaf maple to suggest that they were the primary cause of the decline. Decline in bigleaf maples has also been reported throughout the tree’s entire geographic range, including in California, Oregon, and British Columbia. These are all common signs that something is amiss with the tree, either from drought, root disturbance, chemical imbalance, or pathogen. Symptoms of the decline include partial or entire crown dieback, discoloration and reduced size of the leaves, crown thinning, and death. Forest pathologists at Washington DNR have been investigating the increase in mortality and symptoms in bigleaf maples since 2011, when numerous calls from concerned members of the public and land managers began coming in.
Photo by Jacob Betzen.Īs of the end of 2018, there was no sign of recovery in sick and dying bigleaf maple throughout Western Washington.
WHAT COULD BE CAUSING THE DECLINE IN BIGLEAF MAPLES ( ACER MACROPHYLLUM) ? Crown dieback, thinning, reduced leaf size, and discoloration in bigleaf maple tree.
#Big leaf maple fall update#
This article is an update to those published by the Tree Link in October 2014, “ Bigleaf Maple Dieback in Western Washington? ”, and the follow-up articles in September of 2015, ” What’s Going on with Bigleaf Maple?“, and in August 2016, “ Bigleaf Maple Decline, Update and Next Steps”.
0 kommentar(er)
