Changes in understory light levels following a partial overstory harvest with three retention levels, combined with midstory/understory removal of selected species were examined. Overstory retention levels were set at basal areas (ba) 16.1 (BA16), 11.6 (BA11), and 6.9 (BA6) m 2 per hectare (ha). Prior to mechanical overstory removal, non-oak unmerchantable midstory/understory stems ≥ 5.1 cm were injected with an aqueous herbicide solution. Hemispherical photographs were used to calculate percent canopy closure and total understory light at 1.4 m above ground. Percent canopy closure was reduced 3, 14, 24, and 30 percent for injection only (IO), BA16, BA11, and BA6, respectfully, compared to the non-harvest control (NHC) (~95 percent canopy closure). Understory light levels for NHC, IO, BA16, BA11, and BA6 were 7–9 percent, 11–14 percent, 24–28percent, 37–46 percent, and 44–52 percent of full sunlight, respectively. Post-harvest understory light of BA16 was significantly lower than BA11 and BA6, which were similar. Understanding partial harvest impacts on canopy closure and subsequent understory light conditions will aid forest managers with regeneration harvest planning to promote oak reproduction.
References
[1]
Gottschalk, K.W. Shade, leaf growth, and crown development of Quercus rubra, Quercus velutina, Prunus serotina, and Acer rubrum seedlings. Tree Physiol. 1994, 14, 735–749.
[2]
Johnson, P.S.; Shifley, S.R.; Rogers, R. The Ecology and Silviculture of Oaks; CABI: New York, NY, USA, 2002.
[3]
Lockhart, B.R.; Hodges, J.D.; Gardiner, E.S. Response of advance cherrybark oak reproduction to midstory removal and shoot clipping. South. J. Appl. For. 2000, 24, 45–50.
[4]
Loftis, D.L. A shelterwood method for regenerating red oak in the southern Appalachians. For. Sci. 1990, 36, 917–929.
[5]
Canham, C.D.; Denslow, J.S.; Platt, W.J.; Runkle, J.R.; Spies, T.A.; White, P.S. Light regimes beneath closed canopies and tree fall gaps in temperate and tropical forests. Can. J. For. Res. 1990, 20, 620–631.
[6]
Dey, D.C.; Parker, W.C. Overstory density affects field performance of underplanted red oak (Quercus rubra L.) in Ontario. North. J. Appl. For. 1997, 14, 120–125.
[7]
Nilsen, E.T.; Lei, T.T.; Semones, S.W. Presence of understory shrubs constrains carbon gain in sunflecks by advance regeneration seedlings: Evidence from Quercus rubra seedlings growing in understory forest patches with or without evergreen shrubs present. Int. J. Plant Sci. 2009, 170, 735–747.
[8]
Hodges, J.D.; Gardiner, E.S. Ecology and physiology of oak regeneration. In Oak Regeneration, Serious Problems, Practical Recommendations; Loftis, D.L., McGee, C.E., Eds.; US Department of Agriculture, Forest Service, Southeastern Forest Experiment Station: Asheville, NC, USA, 1993; pp. 54–65.
[9]
Battaglia, L.L.; Fore, S.A.; Sharitz, R.R. Seedling emergence, survival, and size in relation to light and water availability in two bottomland hardwood species. J. Ecol. 2000, 88, 1041–1050.
[10]
Quero, J.L.; Villar, R.; Maranon, T.; Zamora, R.; Vegas, D.; Lawren, S. Relating leaf photosynthetic rate to whole-plant growth of four Quercus species. Funct. Plant Biol. 2008, 35, 725–737.
[11]
Hodges, J.D.; Janzen, G.C. Studies on the biology of cherrybark oak: Recommendations for regeneration. Proceedings of the Fourth Biennial Southern Silvicultural Research Conference, Atlanta, GA, USA, 4–6 November 1986; Phillips, D.R., Ed.; US Department of Agriculture, Forest Service, Southeastern Forest Experiment Station: Asheville, NC, USA, 1986; pp. 133–139.
[12]
Gardiner, E.S.; Hodges, J.D. Growth and biomass distribution of cherrybark oak (Quercus pagoda Raf.) seedlings as influenced by light availability. For. Ecol. Manag. 1998, 108, 127–134.
[13]
Lhotka, J.M.; Loewenstein, E.F. Indirect measures for characterizing light along a gradient of mixed-hardwood riparian forest canopy structures. For. Ecol. Manag. 2006, 226, 310–318.
[14]
Buckley, D.S.; Isenbrands, J.G.; Sharik, T.L. Practical field methods of estimating canopy cover, PAR, and LAI in Michigan oak and pine stands. North. J. Appl. For. 1999, 16, 25–32.
Beaudet, M.; Messier, C. Variation in canopy openness and light transmission following selection cutting in northern hardwood stands: An assessment based on hemispherical photographs. Agric. For. Meteorol. 2002, 110, 217–228.
[17]
Hale, S.H. The effect of thinning intensity on the below-canopy light environment in a Sitka spruce plantation. For. Ecol. Manag. 2003, 179, 341–349.
[18]
Frazer, G.W.; Fournier, R.A.; Trofymow, J.A.; Hall, R.J. A comparison of digital and film fisheye photography for analysis of forest canopy structure and gap light transmission. Agric. For. Meteorol. 2001, 109, 249–263.
