The canopy gap regime in a secondary Neotropical forest in Panama

Yavitt, Joseph B.; Battles, John J.; Lang, Gerald E.; Knight, Dennis H.

doi:10.1017/s0266467400008853

Cited by 61 publications

(56 citation statements)

References 25 publications

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“…High variation in turnover rates between years has been found in secondary tropical forest in Panama (Yavitt et al 1995). It is very likely that similar inter-annual variation in gap forming and filling processes exists within our study area.…”

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confidence: 63%

Long‐term fragmentation effects on the distribution and dynamics of canopy gaps in a tropical montane forest

2015

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Abstract. Fragmentation alters forest canopy structure through various mechanisms, which in turn drive subsequent changes to biogeochemical processes and biological diversity. Using repeated airborne LiDAR (Light Detection and Ranging) mappings, we investigated the size distribution and dynamics of forest canopy gaps across a topical montane forest landscape in Hawaii naturally fragmented by lava .100 yr ago. The combined effects of long-term isolation were evaluated using edge-proximity patterns in the distribution of gaps identified in year 1 (''existing gaps''). In addition, using the data from year 2, we investigated patterns in the loss of canopy (''new gaps'') and regrowth of canopy (''filled gaps''). The size distributions of the three gap types were modelled using the power-law exponent, k. We found that fragmentation has resulted in some large changes in gap dynamics, with both the total area of gaps and the relative proportion of large existing gaps increased with distance to fragment edge. In models of powerlaw distribution scaling, k estimates decreased to asymptotic values within 20 m of fragment edges for existing gaps. The size distributions of new and filled gaps were surprisingly similar. However, the total area of filled gaps was less than that of new gaps, and this difference was greatest near fragment edges. From these results, we conclude that fragmentation may be capable of continuously altering gap-phase dynamics of a forest for more than a century.

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confidence: 63%

Long‐term fragmentation effects on the distribution and dynamics of canopy gaps in a tropical montane forest

2015

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“…Conditions were modelled for the centre of a large and small square gap with tree height:gap width ratios of 1:6 and 1:1 in the dry-and wet-seasons; these sizes are typical of large and small gaps on BCI, respectively (Yavitt et al 1995). It was assumed that the soil profile started at wilting point (-1.5 MPa matric potential) or field capacity (-0.01 MPa) for the dry-and wet-season, respectively.…”

Section: Root Growth Rates In Soilmentioning

confidence: 99%

Allometric relationships between seed mass and seedling characteristics reveal trade-offs for neotropical gap-dependent species

et al. 2007

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A seed size-seed number trade-off exists because smaller seeds are produced in greater number but have a lower probability of establishment. This reduced establishment success of smaller-seeded species may be determined by biophysical constraints imposed by scaling rules. Root and shoot diameter, root growth extension rate (RGER) and shoot length at death for dark-grown seedlings are predicted to scale with the cube root of seed embryo and endosperm mass (m). We confirmed this expectation for ten neotropical gap-dependent tree species with an embryo and endosperm dry mass >1 mg. However, for nine smaller seeded species (m < 1 mg) with photoblastic germination, root and shoot diameters were larger than expected, and consequently, RQER was slower than expected. The maximum shoot thrust of seedlings from seeds with masses >1 mg was comparable to the estimated force required to displace overlying litter, supporting the hypothesis that photoblastic behaviour only occurs in seeds with insufficient shoot thrust to displace overlying leaves. Using the model soil water, energy and transpiration to predict soil drying in small and large gaps, we showed that: (1) gaps that receive a significant amount of direct sunlight will dry more quickly than small gaps that do not, (2) compared to the wet-season, soil that is already dry at depth (i.e. the dry-season) will dry faster after rainfall (this drying would most likely kill seedlings from small seeds) and (3) even during the wet-season, dry periods of a few days in large gaps can kill shallow-rooted seedlings. We conclude that the smaller the seed, the more vulnerable its seedling would be to both covering by litter and soil drying because it can only emerge from shallow depths and has a slow RGER-Consequently, we suggest that these allometrically related factors contribute to the reduced establishment success of smaller-seeded species that underpins the seed size-seed number trade-off.

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“…Recent studies have pointed out that gap composition would be constrained by species availability rather than by habitat limitations (Brokaw and Busing 2000;Lawes and Obiri 2003). In many tropical forests, a standard gap is formed by a single or double treefall event (Chandrashekara and Ramakrishnan 1994), which creates an average gap size ranging from 46 to 85 m 2 [Brokaw (1982b), Jans et al (1993), Yavitt et al (1995) and Green (1996); gaps larger than 400 m 2 are rare (Sanford Jr. et al 1986)]. As the microclimate contrast varies according to gap size (Barton et al 1989), the average gap microclimate in many tropical forests does not differ sufficiently to stimulate light dependent species (Sanford Jr. et al 1986;Brown 1993).…”

Section: Introductionmentioning

confidence: 99%

Gap disturbance regime and composition in the Atlantic Montane Rain Forest: the influence of topography

Lima

Moura

2007

Plant Ecol

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In the Atlantic Montane Rain Forest of south-eastern Brazil, a field study was carried out to describe the forest disturbance regime, analyse canopy gap composition and evaluate the influence of habitat parameters on gap tree species composition. We characterized canopy gaps considering the group of variables as follows: area, type and number of tree/ branch falls, topographic position, soil coverage and surrounding canopy trees. Gap composition was assessed at species level by measuring all individuals inside gaps higher than one meter. Mean gap area of the 42 canopy gaps analysed was 71.9 ± 9.0 m 2 (mean ± SE). Out of the studied gaps, 35.7% were created by uprooted and by snapped trees, 16.7% by dead-standing trees and 11.9% by the fall of large branches. The disturbance regime was characterized by gap openings predominantly smaller than 150 m 2 and by spatial patterning related to topography. Ridges had smaller gaps and higher proportions of gaps created by branch falls; slopes had bigger gaps generally created by uprooting events. The more abundant and frequent species were shade tolerant and the more species-rich families found inside gaps did not differ from the forest as a whole. Pioneer species were rare and restricted to medium and large size classes. The Indicator Species Analysis and the Canonical Correspondence Analysis indicated gap area, topography and the percentage of soil cover by the genera Calathea and Ctenanthe were the predominant variables correlated with woody species distribution. So, topography emerged as an important issue not only to the gap disturbance regime, but also to gap colonization. In respect to the influence of gap processes on the Atlantic Montane Rain Forest regeneration, our results support the view that canopy gap events may not be working as promoters of community wide floristic shifts.

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The canopy gap regime in a secondary Neotropical forest in Panama

Cited by 61 publications

References 25 publications

Long‐term fragmentation effects on the distribution and dynamics of canopy gaps in a tropical montane forest

Long‐term fragmentation effects on the distribution and dynamics of canopy gaps in a tropical montane forest

Allometric relationships between seed mass and seedling characteristics reveal trade-offs for neotropical gap-dependent species

Gap disturbance regime and composition in the Atlantic Montane Rain Forest: the influence of topography

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