Spatial characteristics of canopy disturbances in riparian old-growth hemlock – northern hardwood forests, Adirondack Mountains, New York, USA

2010 ◽  
Vol 40 (1) ◽  
pp. 13-25 ◽  
Author(s):  
Miranda T. Curzon ◽  
William S. Keeton

Gap dynamics in temperate, late-successional forests influence important riparian functions, including organic matter recruitment and light environments over streams. However, controls on gap dynamics specific to riparian forests are poorly understood. We hypothesized that (i) gaps are larger and more frequent nearer streams, (ii) gaps cluster at within-stand scales, and (iii) tree damage type and gap fraction vary among riparian landforms. All gaps within four 6–9 ha plots in riparian old-growth eastern hemlock ( Tsuga canadensis (L.) Carrière) – northern hardwood forest in the Adirondack Mountains, New York, USA, were mapped and measured. We recorded species, damage type, and diameter at breast height for gapmakers and dominant perimeter trees. Spatial distribution was assessed with Ripley’s K. Spatial autocorrelation in gap area and tree damage type were assessed using Moran’s I. Linear regression analysis defined relationships between proximity to streams and gap area and frequency. Expanded gap fraction ranged from 28.3% to 47.6%. Gaps were randomly distributed at scales ≤25 m and clustered at scales of 63–122 m. Distribution patterns were not consistent at other scales. Convergent and divergent landforms significantly influenced gap fraction, tree damage type, and species distributions. Positive correlations between convergent topography and gap area suggest an interaction between low-order riparian landforms and gap formation dynamics in late-successional forests.

2002 ◽  
Vol 32 (9) ◽  
pp. 1562-1576 ◽  
Author(s):  
Gregory G McGee ◽  
Robin W Kimmerer

The objective of this study was to assess the influence of substrate heterogeneity on epiphytic bryophyte communities in northern hardwood forests of varying disturbance histories. Specifically, we compared bryophyte abundance (m2·ha–1) and community composition among partially cut; maturing, 90- to 100-year-old, even-aged; and old-growth northern hardwood stands in Adirondack Park, New York, U.S.A. Total bryophyte cover from 0 to 1.5 m above ground level on trees [Formula: see text]10 cm diameter at breast height (DBH) did not differ among the three stand types. However, bryophyte community composition differed among host tree species and among stand types. Communities in partially cut and maturing stands were dominated by xerophytic bryophytes (Platygyrium repens, Frullania eboracensis, Hypnum pallescens, Brachythecium reflexum, Ulota crispa), while old-growth stands contained a greater representation of calcicoles and mesophytic species (Brachythecium oxycladon, Anomodon rugelii, Porella platyphylloidea, Anomodon attenuatus, Leucodon brachypus, Neckera pennata). This mesophyte-calcicole assemblage occurred in all stand types but was limited by the abundance of large-diameter (>50 cm DBH), thick-barked, hardwood host trees (Acer saccharum Marsh., Tilia americana L., Fraxinus americana L.). This study suggested that epiphytic bryophyte diversity can be sustained and enhanced in managed northern hardwood forests by maintaining host tree species diversity and retaining large or old, thick-barked residual hardwood stems when applying even-aged and uneven-aged silviculture systems.


2008 ◽  
Vol 38 (4) ◽  
pp. 667-676 ◽  
Author(s):  
Blair D. Page ◽  
Myron J. Mitchell

In the Arbutus Lake Watershed in the Adirondack Mountains, New York, two nearly adjacent catchments (14 and 15) varied significantly in volume-weighted stream water nitrate (NO3) export (54 and 17 μequiv.·L–1, respectively; P < 0.001). The most notable differences between the catchments were that Catchment 14 had significantly higher soil Ca concentrations and patches of basswood ( Tilia americana L.). We evaluated the possible contributions of basswood and soil Ca concentrations to soil water NO3 concentrations. Among the major overstory tree species, basswood leaf litter had the lowest C:N ratios, highest Ca concentrations, and among the lowest lignin:N ratios. Basswood basal area was significantly related to soil water NO3 concentrations (R = 0.46, P = 0.01). Forest floor and mineral soil Ca concentrations were positively correlated with basswood basal area and negatively correlated with American beech ( Fagus grandifolia Ehrh.) basal area. Our results suggest that a relatively low-density, calciphilic species such as basswood may create, given the proper soil conditions, hotspots with elevated soil water NO3 concentrations. These hotspots result from the convergence of high soil Ca concentrations, due mostly to soil geology, with relatively labile litter substrate available for N mineralization and nitrification.


1992 ◽  
Vol 22 (2) ◽  
pp. 139-143 ◽  
Author(s):  
Marianne E. Krasny ◽  
Mark C. Whitmore

To determine the importance of gradual tree death to gap dynamics in Allegheny northern hardwood forests, line transect surveys of gaps and gap makers were conducted in three mature forests in central New York. Of the total number of gaps, 71.7% were classified as gradual gaps, meaning they were partial openings in the canopy caused by either trees with greater than 50% branch loss or standing dead trees. Sudden gaps, caused by trees that had fallen, constituted 9.7% of the total number of gaps. Another 18.6% of the gaps had mixed causes. American beech (Fagusgrandifolia Ehrh.), which is subject to beech bark disease in the study area, was the predominant gap maker, representing 52.4% of the gap makers compared with 25.6% of the canopy trees. It is suggested that future studies of forest gap dynamics include measures of gaps forming over a period of time, particularly in forests subject to decline and biotic diseases and in other forests where gradual tree death and standing dead trees are known to be important.


2001 ◽  
Vol 31 (10) ◽  
pp. 1758-1767 ◽  
Author(s):  
Olga J Proulx ◽  
David F Greene

The response of four tree species, Acer saccharum Marsh., Acer rubrum L., Populus tremuloides Michx., and Betula populifolia Marsh., to ice storm damage was studied in the northern hardwood forest of southern Quebec. The focus of the study was the impact of ice accretion on trees as a function of damage type and species at the stand and regional scales along a gradient of ice accumulation ranging from 2 to 88 mm radial thickness and to assess the role of the combined effect of ice and wind stress. Further, we estimate the return time for death resulting from ice storms in these forests. The study showed that the magnitude of ice accumulation was the primary determinant of tree damage (measured as the mean percentage of individual tree canopy removed) and that tree size was the primary determinant of damage type (bending, snapping, or substantial branch loss). Stand position (edge versus interior) did not influence susceptibility to damage. The research demonstrated that edge and slope trees bent or snapped in the direction dictated by crown asymmetry. We have no evidence that the modest winds during this icing event played a major role. Lastly, we couple the return time for a given ice thickness with the probability of severe damage to argue that (i) canopy tree mortality from icing is primarily due to glaze accumulations of moderate rarity (around 12–35 mm of ice) rather than extraordinary events such as 1998 and (ii) ice storms are likely the greatest single source of canopy tree mortality in the hardwood forests of southern Quebec with an estimated return time for death of about 250 years.


2005 ◽  
Vol 35 (10) ◽  
pp. 2510-2514 ◽  
Author(s):  
Julie Messier ◽  
Daniel Kneeshaw ◽  
Mathieu Bouchard ◽  
André de Römer

Canopy gaps play an important role in the dynamics of old-growth forests, although it is not well known how gap dynamics differ among regions. To further our understanding of natural gap dynamics in mixedwood forests, this study compares mixed stands located in eastern (Gaspésie region) and western (Témiscamingue region) Quebec. We tested whether the gap fraction in mixedwood stands was similar in these two regions. Data from field transects were used to characterize current canopy gaps, and aerial photos were used to contrast gap characteristics before and after the most recent spruce budworm (Choristoneura fumiferana Clem.) outbreak, which occurred from 1973 to 1991 in Gaspésie and from 1972 to 1984 in Témiscamingue. The current gap fraction was found to differ between the two regions: it varied from 2% to 48% with an average of 25.6% for the Gaspésie region and from 24% to 52% with an average of 36.6% for the Témiscamingue region. While the last spruce budworm outbreak coincided with a significant increase in canopy openings in the Témiscamingue region (p = 0.047), no such effect was observed in Gaspésie. These results suggest that the temporal pattern of small-scale disturbances can vary among regions, even when similar forest types are compared.


1996 ◽  
Vol 26 (10) ◽  
pp. 1875-1892 ◽  
Author(s):  
Sally E. Dahir ◽  
Craig G. Lorimer

Trends in gap dynamics among pole, mature, and old-growth northern hardwood stands were investigated on eight sites in the Porcupine Mountains of western upper Michigan. Recent gaps (created between 1981 and 1992) were identified using permanent plot records of tree mortality, while older gaps (1940–1981) were identified using stand reconstruction techniques. Although canopy gaps were somewhat more numerous in pole and mature stands, gaps were <25% as large as those in old-growth stands because of smaller gap-maker size, and the proportion of stand area turned over in gaps was only about half as large. Gap makers in younger stands generally had mean relative diameters (ratio of gap-maker DBH to mean DBH of canopy trees) <1.0 and were disproportionately from minor species such as eastern hophornbeam (Ostryavirginiana (Mill.) K. Koch). Gap makers in old-growth stands had mean relative diameters >1.5 and were predominantly from the dominant canopy species. Even in old-growth forests, most gaps were small (mean 44 m2) and created by single trees. Based on the identity of the tallest gap tree in each gap, nearly all shade-tolerant and midtolerant species have been successful in capturing gaps, but gap capture rates for some species were significantly different from their relative density in the upper canopy. The tallest gap trees of shade-tolerant species were often formerly overtopped trees, averaging more than 60% of the mean canopy height and having mean ages of 65–149 years. Canopy turnover times, based on gap formation rates over a 50-year period, were estimated to average 128 years for old-growth stands dominated by sugar maple (Acersaccharum Marsh.) and 192 years for old-growth stands dominated by hemlock (Tsugacanadensis (L.) Carrière). While these estimates of turnover time are substantially shorter than maximum tree ages observed on these sites, they agree closely with independent data on mean canopy residence time for trees that die at the average gap-maker size of 51 cm DBH. The data support previous hypothetical explanations of the apparent discrepancy between canopy turnover times of <130 years for hardwood species and the frequent occurrence of trees exceeding 250 years of age.


Ecology ◽  
1964 ◽  
Vol 45 (3) ◽  
pp. 448-459 ◽  
Author(s):  
Edward Flaccus ◽  
Lewis F. Ohmann

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