13 research outputs found
Large-scale synchrony of gap dynamics and the distribution of understory tree species in maple-beech forests
Large-scale synchronous variations in community dynamics are well documented for a vast array of organisms, but are considerably less understood for forest trees. Because of temporal variations in canopy gap dynamics, forest communitiesâeven old-growth onesâare never at equilibrium at the stand scale. This paucity of equilibrium may also be true at the regional scale. Our objectives were to determine (1) if nonequilibrium dynamics caused by temporal variations in the formation of canopy gaps are regionally synchronized, and (2) if spatiotemporal variations in canopy gap formation aVect the relative abundance of tree species in the understory. We examined these questions by analyzing variations in the suppression and release history of Acer saccharum Marsh. and Fagus grandifolia Ehrh. from 481 growth series of understory saplings taken from 34 mature stands. We observed that (1) the proportion of stems in release as a function of time exhibited a U-shaped pattern over the last 35 years, with the lowest levels occurring during 1975â1985, and that (2) the response to this in terms of species composition was that A. saccharum became more abundant at sites that had the highest proportion of stems in release during 1975â1985. We concluded that the understory dynamics, typically thought of as a stand-scale process, may be regionally synchronized
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Long-term decline of sugar maple following forest harvest, Hubbard Brook Experimental Forest, New Hampshire
Forest harvesting can impact site quality by removing essential nutrients, exacerbating the effects of historic base cation losses associated with acid deposition. We studied the 30-year trajectory of forest recovery from clearcutting (whole-tree harvest (WTH)) in a forest originally dominated by sugar maple (Acer saccharum Marsh.). At both the watershed scale (21.9 ha) and the âdetailedâ plot scale (1 m2), a dramatic decline of sugar maple was observed, along with maintenance of American beech (Fagus grandifolia Ehrh.) and an increase in birch, mainly yellow birch (Betula alleghaniensis Britt.). Many of the âdetailedâ plots where sugar maple failed to recruit became unoccupied rather than being âwonâ by another species. The decline of sugar maple was most severe in the upper elevation zones of the watershed, where low base status (especially Ca) of the soils was a likely driver. The results support previous studies indicating that regeneration by sugar maple is severely compromised on base cation depleted soils. Lower survival of seedlings for sugar maple emphasized the importance of maintaining advance regeneration to favor desired species such as sugar maple. Foresters should consider that sites with low base saturation and exchangeable Ca are likely to exhibit regeneration failure for sugar maple in the long term, even those with initial dominance by this species
Long-term decline of sugar maple following forest harvest, Hubbard Brook Experimental Forest, New Hampshire
Forest harvesting can impact site quality by removing essential nutrients, exacerbating the effects of historic base cation losses associated with acid deposition. We studied the 30-year trajectory of forest recovery from clearcutting (whole-tree harvest (WTH)) in a forest originally dominated by sugar maple (Acer saccharum Marsh.). At both the watershed scale (21.9 ha) and the âdetailedâ plot scale (1 m2), a dramatic decline of sugar maple was observed, along with maintenance of American beech (Fagus grandifolia Ehrh.) and an increase in birch, mainly yellow birch (Betula alleghaniensis Britt.). Many of the âdetailedâ plots where sugar maple failed to recruit became unoccupied rather than being âwonâ by another species. The decline of sugar maple was most severe in the upper elevation zones of the watershed, where low base status (especially Ca) of the soils was a likely driver. The results support previous studies indicating that regeneration by sugar maple is severely compromised on base cation depleted soils. Lower survival of seedlings for sugar maple emphasized the importance of maintaining advance regeneration to favor desired species such as sugar maple. Foresters should consider that sites with low base saturation and exchangeable Ca are likely to exhibit regeneration failure for sugar maple in the long term, even those with initial dominance by this species
Conifer Presence May Negatively Affect Sugar Mapleâs Ability to Migrate into the Boreal Forest Through Reduced Foliar Nutritional Status
Human-sensitive bryophytes retreat into the depth of forest fragments in central European landscape
Bryophyte diversity in Californian grasslands in relation to substrate quality, exotic vascular plants and disturbance
Limits to reproduction and seed size-number trade-offs that shape forest dominance and future recovery
The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundation for assessing fitness in forest trees. Four major findings emerged. First, seed production is not constrained by a strict trade-off between seed size and numbers. Instead, seed numbers vary over ten orders of magnitude, with species that invest in large seeds producing more seeds than expected from the 1:1 trade-off. Second, gymnosperms have lower seed production than angiosperms, potentially due to their extra investments in protective woody cones. Third, nutrient-demanding species, indicated by high foliar phosphorus concentrations, have low seed production. Finally, sensitivity of individual species to soil fertility varies widely, limiting the response of community seed production to fertility gradients. In combination, these findings can inform models of forest response that need to incorporate reproductive potential