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In the northeastern United States, tree declines associated with acid deposition induced calcium depletion have been documented, notably for red spruce (Picea rubens Sarg.) and sugar maple (Acer saccharum Marsh.). There is conflicting evidence concerning whether co-occurring tree species capitalized on these declines or suffered similar growth reductions and on how growth has fluctuated relative to environmental variables. We examined five species along three elevational transects on Mt. Mansfield, Vermont: sugar maple, red spruce, red maple (Acer rubrum L.), yellow birch (Betula alleghaniensis Britton), and balsam fir (Abies balsamea (L.) Mill.). We found baseline differences ingrowth. Red maple and yellow birch had the highest growth, sugar maple and red spruce had intermediate growth, and balsam fir had the lowest growth. While some year-to-year declines were associated with specific stress events, protracted patterns such as recent increases in red spruce and red maple growth were correlated with increased temperature and cooling degree days (heat index). For most species and elevations, there was a positive association between temperature and growth but a negative association with growth in the following year. Based on our comparisons, for some species, growth at Mt. Mansfield aligns with regional trends and suggests that patterns assessed here may be indicative of the broader region. Key words: red spruce, sugar maple, yellow birch, red maple, balsam fir. Dans le nord-est des Etats-Unis, le deperissement des arbres associe a l'appauvrissement des sols en calcium cause par les depots acides a ete documente, notamment dans le cas de l'epinette rouge (Picea rubens Sarg.) et de l'erable a sucre (Acer saccharum Marsh.). Il y a des indications contradictoires au sujet des especes d'arbre coexistantes a savoir si elles ont profite de ce deperissement ou subi des reductions similaires de croissance, et de quelle facon leur croissance a fluctue en fonction des variables environnementales. Nous avons etudie cinq especes le long de trois transects altitudinaux sur le mont Mansfield au Vermont: l'erable a sucre, l'epinette rouge, l'erable rouge (A. rubrum L.), le bouleau jaune (Betula alleghaniensis Britton) et le sapin baumier (Abies balsamea (L.) Mill.). Nous avons observe des differences de base dans la croissance. L'erable rouge et le bouleau jaune avaient la plus forte croissance, l'erable a sucre et l'epinette rouge avaient une croissance intermediate et le sapin baumier avait la plus faible croissance. Tandis que d'annee en annee des deperissements ont ete associes a des evenements stressant specifiques, des tendances prolongees, telles que l'augmentation recente de la croissance de l'epinette rouge et de l'erable a sucre, etaient correlees avec l'augmentation de la temperature et les degres-jours de refroidissement (indice de chaleur). Dans le cas de la plupart des especes et des altitudes, il y avait une relation positive entre la temperature et la croissance, mais une relation negative avec la croissance de l'annee suivante. Sur la base de nos comparaisons, dans le cas de certaines especes la croissance au mont Mansfield s'harmonise avec les tendances regionales et indique que les comportements evalues ici sont possiblement representatifs de l'ensemble de la region. [Traduit par la Redaction] Mots-cles: epinette rouge, erable a sucre, bouleau jaune, erable rouge, sapin baumier., Introduction Regional forests in the northeastern United States (US) reflect temporally and spatially complex land use change in the 19th and 20th centuries that included deforestation, agricultural expansion, and subsequent [...]

Highlights • In the 5-state region, damages affected 3.4 ± 1.3% of forestland per year. • There were no significant linear, temporal trends in the area damaged annually. • 10% of regional forests experienced 1+ events; 3% experienced 2+ events. • Non-native insects were associated with widespread and locally intense damage. Abstract Forest damage and disturbance can have significant influences on tree vigor, species composition, biodiversity, and associated ecosystem services. Recognizing the importance of monitoring spatiotemporal patterns of forest health, federal and state agencies in the United States (US) have conducted aerial insect and disease surveys (IDS) annually to quantify the extent of forest damage by type and causal agent. Although agencies have collected these geospatial data for decades, long-term trends and patterns have not been synthesized across the predominantly forested region of northern New England and New York. Here, we utilized a novel, online forest damage and disturbance mapping portal, the Northeastern Forest Health Atlas, to investigate inter-annual and long-term patterns (2000–2016). Our analysis indicated that ∼11.0 million ha of forestland (10% of the study region) experienced at least one damage event (i.e., an IDS polygon) over the 17-year period, averaging 647,425 ± 215,482 ha (3.4 ± 1.1% of the region's forestland) annually. While there were no detectable linear, long-term trends in annual extent or relative abundance of damage by agent category, we found that some ecoregions experienced relatively higher damage rates (e.g., Acadian Plains and Hills, Atlantic Coastal Pine Barrens). Across the region, insects were the most extensive damage agent category mapped (∼8 million ha), with a relatively small number of invasive insects (19 species) accounting for half of this damage. Because climate change may alter the type, severity, and frequency of forest disturbance, quantifying baseline patterns of forest damage is critical for detecting shifts in forest dynamics and developing adaptive management strategies. [ABSTRACT FROM AUTHOR]

Acidic sulfur (S) and nitrogen (N) deposition depletes cations such as calcium (Ca) from forest soils and has been linked to increases in foliar winter injury that led to the decline of red spruce ( Picea rubens Sarg.) in the northeastern United States. We used results from a 30 m resolution steady-state S and N critical load exceedance model for New England to better understand the spatial connections between Ca depletion and red spruce productivity. Atmospheric deposition and other inputs were estimated for a 5-year period (1984–1988) in order to smooth year-to-year variations in climate and patterns of atmospheric transport. Deposition levels prior to the reductions that followed the 1990 Amendments to the Clean Air Act were used because tree health and productivity declines were expected to be most responsive to high acid loading. We examined how radial growth (basal area increment) of 441 dominant and co-dominant red spruce trees from 37 sites across Vermont and New Hampshire was related to modeled estimates of S and N critical load exceedance. We assessed growth using statistical models with exceedance as a source of variation, but which also included “year” and “elevation class” (to help account for climatic variability) and interactions among factors. As expected, yearly climate-related sources of variation accounted for most of the differences in growth. However, exceedance was significantly and negatively associated with mean growth for the study period (1951–2010) overall, and particularly for the 1980s and 2000s – periods of numerous and/or severe foliar winter injury events. Because high winter injury reflects the convergence of predisposing (cation depletion) and inciting (weather) factors, exceedance alone appears insufficient to define associated patterns of growth reduction. Significant interactions indicated that exceedance had little influence on growth at low elevations (where intrinsic conditions for growth were generally good) or high elevations (where growth was uniformly poor), whereas exceedance was significantly associated with reduced growth at mid elevations over long periods of time. Exceedance was also linked to reduced growth rebounds following a region-wide foliar winter injury event in 2003. Overall, our analyses suggest that modeled S and N critical load exceedance can help account for red spruce growth and rebound from injury in the field. Interestingly, recent growth for red spruce is above average for the 20th to 21st century dendrochronological record – indicating that the factors shaping growth may be changing. The influence of reduced pollution inputs on this recent growth surge is under investigation. [ABSTRACT FROM AUTHOR]

Highlights: [•] Red spruce declined in growth for 3years after the 2003 winter injury event. [•] This event reduced the C sequestration of red spruce by about 673,000 metric tons. [•] Growth impacts following winter injury were not uniform across elevations. [•] By 2010, net growth had rebounded at low and mid-, but not high elevation plots. [•] There was a growth upsurge in 2009 and 2010, particularly for mid-elevations. [ABSTRACT FROM AUTHOR]