Gaps in a gappy forest: plant resources, longleaf pine regeneration, and understory response to tree removal in longleaf pine savannas

McGuire, John; Mitchell, Robert J.; Moser, E. Barry; Pecot, Stephen D.; Gjerstad, Dean H.; Hedman, Craig W.

doi:10.1139/x01-003

Cited by 159 publications

(92 citation statements)

References 53 publications

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“…The most xeric sites-termed pine sandhills-tend to have very low organic matter accumulation [23] and open understory [24]. Modern fire suppression from forest management or agriculture, however, has led to hardwood encroachment, the development of a woody mid-story [25] and altered cover and composition of understory vegetation [23,[26][27][28]. Without fire, litter from pines and hardwoods can accumulate as deep as 25 cm, especially near the bases of large trees [22].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Restoration Treatments on the Spatial Variability of Soil Processes under Longleaf Pine Trees

Lavoie

Mack

Hiers

et al. 2012

Forests

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Abstract:The objectives of this study were to (1) characterize tree-based spatial patterning of soil properties and understory vegetation in frequently burned ("reference state") and fire-suppressed longleaf pine forests; and (2) determine how restoration treatments affected patterning. To attain these objectives, we used an experimental manipulation of management types implemented 15 years ago in Florida. We randomly located six mature longleaf pine trees in one reference and four restoration treatments (i.e., burn, control, herbicide, and mechanical), for a total of 36 trees. In addition to the original treatments and as part of a monitoring program, all plots were subjected to several prescribed fires during these 15 years. Under each tree, we sampled mineral soil and understory vegetation at 1 m, 2 m, 3 m and 4 m (vegetation only) away from the tree. At these sites, soil carbon and nitrogen were higher near the trunk while graminoids, forbs and saw palmetto covers showed an opposite trend. Our results confirmed that longleaf pine trees affect the spatial patterning of soil and understory vegetation, and this patterning was mostly limited to the restoration sites. We suggest frequent burning as a probable cause for a lack of spatial structure in the "reference state". We attribute the presence of spatial patterning in the restoration sites to accumulation of organic materials near the base of mature trees.

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Section: Introductionmentioning

confidence: 99%

The Effect of Restoration Treatments on the Spatial Variability of Soil Processes under Longleaf Pine Trees

Lavoie

Mack

Hiers

et al. 2012

Forests

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“…However, they differ greatly in the partitioning of solar radiation intercepted in the canopy versus the forest floor. More radiation on the forest floor may have large effects on other ecological processes, such as regeneration, including the establishment and growth of seedlings [Tognetti et al, 1997;McGuire et al, 2001;Naumburg et al, 2001], or heat flow into the soil, which influences other ecosystem processes, such as decomposition and forest floor CO 2 efflux [Palmroth et al, 2005;Daly et al, 2009]. Because carbon assimilation is a canopy process, the difference in radiation interception in the canopy is reflected in the estimates of A n (Figure 7a), but a smaller difference was seen in LE, a process occurring in both the canopy and forest floor (Figure 5a).…”

Section: Discussionmentioning

confidence: 99%

“…[2] Forest canopies regulate exchanges of energy, water and carbon with the atmosphere, particularly via leaf stomata, the primary corridors for transpiration and carbon assimilation [Betts et al, 1997;Pukkala et al, 1991;Sellers et al, 1997;Tang et al, 1999;McGuire et al, 2001;Ryan, 2002;Gedney et al, 2006;Betts et al, 2007]. Among the key drivers of stomatal regulation, the light environment is highly influential because of (1) the strong vertical heterogeneity imposed by the leaf transmission and interception, and (2) the nonlinear response of both leaf stomata and photosynthesis to light.…”

Section: Introductionmentioning

confidence: 99%

Energy, water, and carbon fluxes in a loblolly pine stand: Results from uniform and gappy canopy models with comparisons to eddy flux data

et al. 2009

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[1] This study investigates the impacts of canopy structure specification on modeling net radiation (R n ), latent heat flux (LE) and net photosynthesis (A n ) by coupling two contrasting radiation transfer models with a two-leaf photosynthesis model for a maturing loblolly pine stand near Durham, North Carolina, USA. The first radiation transfer model is based on a uniform canopy representation (UCR) that assumes leaves are randomly distributed within the canopy, and the second radiation transfer model is based on a gappy canopy representation (GCR) in which leaves are clumped into individual crowns, thereby forming gaps between the crowns. To isolate the effects of canopy structure on model results, we used identical model parameters taken from the literature for both models. Canopy structure has great impact on energy distribution between the canopy and the forest floor. Comparing the model results, UCR produced lower R n , higher LE and higher A n than GCR. UCR intercepted more shortwave radiation inside the canopy, thus producing less radiation absorption on the forest floor and in turn lower R n . There is a higher degree of nonlinearity between A n estimated by UCR and by GCR than for LE. Most of the difference for LE and A n between UCR and GCR occurred around noon, when gaps between crowns can be seen from the direction of the incident sunbeam. Comparing with eddy-covariance measurements in the same loblolly pine stand from May to September 2001, based on several measures GCR provided more accurate estimates for R n , LE and A n than UCR. The improvements when using GCR were much clearer when comparing the daytime trend of LE and A n for the growing season. Sensitivity analysis showed that UCR produces higher LE and A n estimates than GCR for canopy cover ranging from 0.2 to 0.8. There is a high degree of nonlinearity in the relationship between UCR estimates for A n and those of GCR, particularly when canopy cover is low, and suggests that simple scaling of UCR parameters cannot compensate for differences between the two models. LE from UCR and GCR is also nonlinearly related when canopy cover is low, but the nonlinearity quickly disappears as canopy cover increases, such that LE from UCR and GCR are linearly related and the relationship becomes stronger as canopy cover increases. These results suggest the uniform canopy assumption can lead to underestimation of R n , and overestimation of LE and A n . Given the potential in mapping regional scale forest canopy structure with high spatial resolution optical and Lidar remote sensing plotforms, it is possible to use GCR for up-scaling ecosystem processes from flux tower measurements to heterogeneous landscapes, provided the heterogeneity is not too extreme to modify the flow dynamics.

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“…Canopy gaps, known as spatial and temporal environmental heterogeneity in forests (Denslow, 1987;Connell, 1989;Ostertag, 1998), facilitate the establishment and growth of understory vegetation (Ehrenfeld, 1980;Huenneke, 1983) by creating new open spaces and releasing resources (Gray & Spies, 1997;McGuire et al, 2001;De Chantal et al, 2003). Gaps are favorable not only for light-demanding species like bamboos and shrubs (Taylor & Qin, 1988a), but also for shadetolerant coniferous regeneration as well (Gaudio et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Effects of gap size, gap age, and bamboo Fargesia denudata on Abies faxoniana recruitment in South-western China

et al. 2015

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Aim of study: to study the effects of gap size, gap age and bamboo Fargesia denudata on natural regeneration of Abies faxoniana, both of which are the ubiquitous dominants in our research area.Area of study: subalpine coniferous forests in Wanglang Natural Reserve in Southwestern China. Material and Methods: 10 transect belts were randomly established, and a total of 97 gaps were recorded and used.Main results: (1) the number of bamboos with coverage of <17% significantly increased with increases of gap size and age, but the latter had little influence on the numbers of F. denudata with coverage of >17%. (2) F. denudata strongly inhibited A. faxoniana seedlings and saplings in small, young and old gaps, where the amount of A. faxoniana recruitment was relatively abundant, than in other types of gap. (3) The numbers of A. faxoniana seedlings in A-gaps, significantly decreased with the increases in gap size. However, in gaps where F. denudate was also present, A. faxoniana seedlings and saplings were insensitive to gap size or age. Research highlights: thick F. denudata would not be influenced by gap size or age. Because of the low occurrences of A. faxoniana seedlings and saplings, the negative effect of gap size, gap age and F. denudata on A. faxoniana recruitment was unclear

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Gaps in a gappy forest: plant resources, longleaf pine regeneration, and understory response to tree removal in longleaf pine savannas

Cited by 159 publications

References 53 publications

The Effect of Restoration Treatments on the Spatial Variability of Soil Processes under Longleaf Pine Trees

The Effect of Restoration Treatments on the Spatial Variability of Soil Processes under Longleaf Pine Trees

Energy, water, and carbon fluxes in a loblolly pine stand: Results from uniform and gappy canopy models with comparisons to eddy flux data

Effects of gap size, gap age, and bamboo Fargesia denudata on Abies faxoniana recruitment in South-western China

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