Among species, sugar maple was the most sensitive to excess Mn based on growth and photosynthetic measurements. In field samples, Mn in deciduous foliage hyperaccumulated to concentrations more than twice as high as those found in evergreen needles.

In a second study, we examined growth and photosynthetic responses of seedlings exposed to excess Mn in sand culture. For the first objective, leaf samples of seedlings from five acidic, non-glaciated field sites on Pennsylvania's Allegheny Plateau were collected and analyzed for leaf element concentrations. The objectives of this study were to: (1) compare foliar nutrient accumulation patterns of six deciduous (sugar maple (Acer saccharum Marsh.), red maple (Acer rubrum L.), red oak (Quercus rubra L.), white oak (Quercus alba L.), black cherry (Prunus serotina Ehrh.) and white ash (Fraxinus americana L.)) and three evergreen (eastern hemlock (Tsuga canadensis L.), white pine (Pinus strobus L.) and white spruce (Picea glauca (Moench) Voss.)) tree species growing on acidic forest soils and (2) examine how leaf phenology and other traits that distinguish evergreen and deciduous tree species influence foliar Mn accumulation rates and sensitivity to excess Mn. More information about this initiative will be announced later in 2023.Foliar nutrient imbalances, including the hyperaccumulation of manganese (Mn), are correlated with symptoms of declining health in sensitive tree species growing on acidic forest soils. The agency is currently working closely with Tribes to provide technical assistance and award financial assistance to tribal nurseries to improve nursery operations. In addition to regularly appropriated funding, the Bipartisan Infrastructure Law is helping to fund RNGR technical assistance to improve reforestation and restoration activities on Federal, state, Tribal, local, private, industrial, and international lands. This program is composed of specialists and researchers who provide technical guidance and best available science for nurseries and land managers regarding production and planting of trees and other native plants for reforestation, restoration, and conservation. The Forest Service also supports technical assistance and research to assist nursery operators through the Reforestation, Nurseries, and Genetic Resources ( RNGR) program. Twenty-seven state nurseries have been selected to receive funding, as well as two nurseries managed by Commonwealth of the Northern Mariana Islands and Republic of Marshall Islands. In early 2023, state, island territory, and commonwealth nurseries across the country received financial assistance through the Bipartisan Infrastructure Law to make improvements to the operation and efficiency of reforestation nurseries. In 2022, 38 State and territorial nurseries reported growing 123 million tree seedlings to support projects across the nation. The Bipartisan Infrastructure Law invests in the nation’s network of state, commonwealth and territory, and tribal nurseries, which produce tree seedlings to support ecosystem restoration and conservation on all lands. America’s forests are in a state of fire emergency: Nearly a quarter of the contiguous United States remains at moderate to very high risk of severe wildfires, and the need for intensive reforestation efforts is increasing. Over the last two decades we have witnessed what has become a now familiar pattern: bigger and more destructive wildfires that are extremely difficult to suppress. Targeted replanting of forests on federal, state, tribal, and privately managed land following devastating wildfires is key to ensuring resilient forests for future generations to use and enjoy. Tree nurseries are vital to efforts to restore forests following wildfires, hurricanes, and other natural disturbances. (USDA Forest Service photo by Andrew Avitt). Conifer seedlings at a nursery take root.

Tree seedlings mn