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Sugar maple ( Acer saccharum Marsh.) is a keystone species in the northern hardwood forest, and decline episodes have negatively affected the growth and health of sugar maple in portions of its range over the past 50+ years. Crown health, growth, survival, and flower and seed production of sugar maple were negatively affected by a widespread decline event in the mid-1980s on the unglaciated Allegheny Plateau in northern Pennsylvania. A long-term liming study was initiated in 1985 to evaluate responses to a one-time application of 22.4 Mg·ha-1 of dolomitic limestone in four northern hardwood stands. Over the 23-year period ending in 2008, sugar maple basal area increment (BAINC) increased significantly ( P ≤ 0.05) in limed plots from 1995 through 2008, whereas American beech ( Fagus grandifolia Ehrh.) BAINC was unaffected. For black cherry ( Prunus serotina Ehrh.), the third principal overstory species, BAINC and survival were reduced in limed plots compared with unlimed plots. Foliar Ca and Mg remained significantly higher in sugar maple foliage sampled 21 years after lime application, showing persistence of the lime effect. These results show long-term species-specific responses to lime application. [ABSTRACT FROM AUTHOR]

Sugar maple (Acer saccharum Marsh.) decline has occurred throughout its range over the past 50 years, although decline symptoms are minimal where nutritional thresholds of Ca, Mg, and Mn are met. Here, we show that availability of these elements also controls vascular plant species composition in northern hardwood stands and we identify indicator species of these nutrient thresholds. Presence and abundance of vascular plant species and data on 35 environmental variables were collected from 86 stands in New Hampshire and Vermont (NHVT) and Pennsylvania and New York (PANY). Nonmetric multidimensional scaling ordination was used to determine which variables affected presence and abundance of species; both measures gave similar results. A base cation – acid cation nutrient gradient on axis one accounted for 71.9% (NHVT) and 63.0% (PANY) of the variation in the nonmetric multidimensional scaling ordination. Measures of Ca, Mg, and pH formed the base end and Al, Mn, K, soil acidity, and organic matter the acid end in both subregions. In both subregions, sugar maple foliar Mg and Ca had the strongest association with the base end of axis 1; exchangeable Al in NHVT and foliar Mn in PANY were strongly associated with the acid end. McNemar’s exact test and indicator species analysis were used to determine which species were present in stands that met the nutritional thresholds for Ca, Mg, and Mn foliar chemistry. McNemar’s exact test identified 16 species in NHVT and PANY, 16 additional species in NHVT only, and 12 additional species in PANY only. Indicator species analysis identified a subset of these species with the highest frequency of occurrence. Indicator species could provide land managers with a diagnostic tool for determining where on the landscape sugar maple is “at risk” or likely to remain healthy in the face of stresses. Le dépérissement de l’érable à sucre (Acersaccharum Marshall) est survenu partout dans l’aire de répartition de cette essence au cours des 50 dernières années mais il y a très peu de symptômes de dépérissement aux endroits où les seuils nutritionnels pour Ca, Mg et Mn sont atteints. Nous montrons ici que la disponibilité de ces éléments régit également la composition en espèces de plantes vasculaires dans les peuplements de feuillus nordiques et nous identifions des espèces indicatrices des seuils pour ces nutriments. La présence et l’abondance des espèces de plantes vasculaires ainsi que 35 variables environnementales ont été mesurées dans 86 peuplements des tats du New Hampshire et du Vermont (NHVT) ainsi que ceux de la Pennsylvanie et de New York (PANY). L’ordination de mesures multidimensionnelles non paramétriques a été utilisée pour déterminer quelles variables influencent la présence et l’abondance des espèces; les deux mesures ont produit des résultats similaires. Un gradient de nutriments allant des cations basiques à acides sur l’axe un expliquait 71,9% (NHVT) et 63% (PANY) de la variation dans l’ordination. Les mesures de Ca, Mg et de pH formaient la partie basique et Al, Mn, K, l’acidité du sol et la matière organique formaient la partie acide dans les deux sous-régions. Dans les deux sous-régions, le Mg et le Ca foliaire de l’érable à sucre était le plus étroitement associé à la portion basique de l’axe un; l’Al échangeable dans la sous-région NHVT et le Mn foliaire dans la sous-région PANY étaient fortement associés à la portion acide. Le test de McNemar et l’analyse des espèces indicatrices ont été utilisés pour déterminer quelles espèces étaient présentes dans les peuplements où les seuils nutritionnels pour Ca, Mg et Mn étaient atteints dans les feuilles. Le test de McNemar a identifié 16 espèces dans les deux sous-régions, 16 autres dans la sous-région NHVT et seulement 12 autres dans la sous-région PANY. L’analyse des espèces indicatrices a identifié un sous-ensemble des ces espèces dont la fréquence était la plus élevée. Les espèces indicatrices pourraient fournir aux aménagistes du territoire un outil de diagnostique pour déterminer à quel endroit le paysage d’érable à sucre est à risque et où il restera sain face aux stress. Note : l.7 de l’abstract, saccharum Marshall au lieu desaccharum Marsh. [ABSTRACT FROM AUTHOR]

Light transmittance estimates under open, heterogeneous woodland canopies such as those of longleaf pine (Pinus palustris Mill.) forests report high spatial and temporal variation in the quantity of the light environment. In addition, light quality, that is, the ratio of red to far-red light (R:FR), regulates important aspects of plant development including stem extension, specific leaf area, and seed germination. We conducted two experiments to document sources of variation in R:FR (using a LI-COR 1800 portable spectroradiometer with a cosine-corrected light sensor) in a 70- to 90-year-old natural longleaf pine woodland in southwest Georgia, USA. The first experiment compared instantaneous measurements of R:FR over a 3-day period (March) with annual estimates of canopy transmittance (using gallium arsenide phosphide photodiodes) across the range of observed overstory abundance. The second experiment examined the effect of wiregrass cover (above or below), sky condition (blue sky or overcast), and solar angle (four sampling periods between October and March) on R:FR using a multifactorial repeated measures design. We found that (1) R:FR was significantly (p < 0.0001) and strongly (R2 = 0.72) related to annual estimates of canopy transmittance (percent photosynthetic photon flux density, %PPFD); (2) R:FR and %PPFD showed significant negative relationships with increasing overstory stocking (R2 = 0.20, p = 0.028 for R:FR, and R2 = 0.87, p < 0.0001 for %PPFD); and (3) R:FR decreased with increasing solar angle from maximum zenith for the study site under blue skies, was greater under overcast skies (0.84 blue sky vs. 1.18 overcast sky), and decreased under wiregrass (Aristida stricta Michx.) canopies (1.10 above vs. 0.98 below). [ABSTRACT FROM AUTHOR]

The longevity of a single 22.4 Mg·ha−1 application of dolomitic limestone at four northern hardwood stands was evaluated over 30 years (1986–2016) to determine whether changes in soils, foliage, and tree growth were sustained on the unglaciated Allegheny Plateau in northern Pennsylvania, USA. In limed plots, soils, sampled to 45–55 cm depth, and sugar maple (Acer saccharum Marsh.) and black cherry (Prunus serotina Ehrh.) foliage had significantly (P ≤ 0.05) greater concentrations of calcium (Ca) and magnesium (Mg) through 2016 compared with samples from unlimed plots. Ca and Mg capitals (g·m−2) in the Oi through A horizons combined were greater on limed plots than unlimed plots, largely due to increases in the thickness and nutrient concentration in the A horizon. Over 30 years, sugar maple basal area increment (cm2·year−1 BAINC) was greater in limed plots (30.6 cm2·year−1 vs unlimed 13.3), American beech (Fagus grandifolia Ehrh.) BAINC was unaffected by lime application, and black cherry BAINC was reduced in limed plots compared with unlimed plots. The sustained effect of this one-time lime treatment shows the strong role of efficient nutrient cycling in forests and suggests that the benefits over a substantial portion of a stand rotation may increase the feasibility of operational liming. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor in response to comments made on the thirty years of change in forest soils of the Allegheny Plateau, Pennsylvania.

A correction to the article "Linking Environmental Gradients, Species Composition and Vegetation Indicators of Sugar Maple Health in the Northeastern United States," by Stephen B. Horsley, Scott W. Bailey, Todd E. Ristau, Robert P. Long and Richard A. Hallett, published in issue 38, is presented.

Sugar maple (Acer saccharum Marsh.) decline disease, decreased growth, and regeneration failure have been related to a low supply of Ca and Mg. There is increased interest in augmenting cation availability via liming, but there is little information on the amounts of lime required and the longevity of the lime treatment. A single application of 22.4 Mg ha-1 of dolomitic limestone in 1985 at four forested sites in Potter County, PA has shown that soil, soil water, and sugar maple foliage chemistry are significantly altered by liming and the changes in soils and foliage persist as long as 21-yr post-treatment. By 2001, only 3 kg ha-1 of lime remained undissolved while increases in exchangeable Ca and Mg, and pH continued through 2006 at depths up to 35 to 45 cm. Exchangeable Mn and Al concentrations were significantly reduced by lime application, though effects were slower to develop at deeper depths. Soil solution chemistry from 1996 was highly variable but reflected the changed soil nutrients. On limed plots, sugar maple foliage had elevated concentrations of Ca and Mg in 2006 samples, indicating the persistence of the lime treatment. Comparison of Ca/Al ratios in soil solution, soils, and foliage show inconsistencies from previous published risk thresholds. Species-specific thresholds of Ca and Mg availability in soil and foliage have better potential management application and should be more rigorously tested as stress indicators. [ABSTRACT FROM AUTHOR]

In Pennsylvania, two hypotheses compete to explain the chronic oak ( spp.) regeneration problem: excessive deer browsing and soil cation depletion. We tested these hypotheses by evaluating the effect of forest liming and deer exclosure fencing on northern red oak ( L.) seedling growth and nutrition in five oak shelterwood stands in Pennsylvania over 6 years. In each stand, four planting plots were located inside a 2.4 m high woven wire fence and another four were established outside the fence. About 225 northern red oak acorns were planted in each plot in spring 2004. Dolomitic limestone was applied to randomly selected plots at rates of 0, 4.5, 9.0, and 13.5 Mg·ha-1 during May 2004. There were no statistically significant ( P ? 0.05) growth responses to lime applications. The only significant growth responses resulted from the fence versus no-fence treatment. A significant ( P < 0.003) fence × year interaction for seedling height and root collar diameter indicates differential impacts of deer browsing. By 2009, seedlings inside fences averaged 32 cm tall, while seedlings outside the fences averaged 17 cm. Similarly, root collar diameter averaged 6.6 mm outside the fences and 9.1 mm inside fences. [ABSTRACT FROM AUTHOR]

Sugar maple (Acer saccharum Marsh.) decline disease on the Allegheny Plateau (region 1) resulted in high levels of mortality during the 1990s. Sugar maple was predisposed to decline because of an imbalance in Mg, Ca, and Mn nutrition and incited to decline by repeated defoliation. We sampled 33 stands in New York, Vermont, and New Hampshire (region 2) to determine if this model of sugar maple decline applies to a broader region. Low Ca and Mg and higher Mn levels were correlated with poorer tree health in both regions, but region 2 stands had little defoliation and few dead trees, suggesting that both unbalanced nutrition and stress are required for mortality to occur. We predict that stands with low foliar Ca and Mg and high Mn levels would incur increased mortality if stressed. In region 2, relationships between Ca, Mg, and Mn levels and dieback suggested that impacts on sugar maple may be caused by nutritional imbalance alone. Partial correlation analysis suggests that antagonism between Mg and Mn is the most important nutritional factor in region 1, while Mn supply is most important in region 2. We suggest that more research is needed on the interacting roles played by Ca, Mg, Al, and Mn in sugar maple performance. [ABSTRACT FROM AUTHOR]

Cleavitt et al. (2018, Can. J. For. Res. 48(1): 23–31, doi:10.1139/cjfr-2017-0233) report a lack of sugar maple (Acer saccharum Marsh.) regeneration in Hubbard Brook Experimental Forest (HBEF), Watershed 5 (W5), following whole-tree clearcut harvesting and purport that harvesting-induced soil calcium depletion contributed to regeneration failure of this species. In New England, clearcutting is a silvicultural strategy used to promote less tolerant species, especially birch (Betula spp.; Marquis (1969), Birch Symposium Proceedings, USDA Forest Service; Leak et al. (2014), doi:10.2737/NRS-GTR-132), which is just the outcome that the authors report. While this study reports an impressive, long-term data set, given broad interest in sugar maple and sustainability of forest management practices, we feel that it is critical to more fully explore the role of nutrition on sugar maple dynamics, both prior to and during the experiment, and to more fully review the scientific record on the role of whole-tree clearcutting in nutrient-induced sugar maple dynamics. [ABSTRACT FROM AUTHOR]

Determines the effects of lime fertilization on sugar maple in Pennsylvania. Responses of tree vitality to lime additions; Changes in foliar and soil elements; Correlation between tree growth and crown vitality.