1. One-year Oak Regeneration (Quercus spp
One-year Oak Regeneration (Quercus spp.) Responses to Midstory Control and Partial Harvest Treatments
Charles H. Miles1, Andrew W. Ezell3, Heidi Renninger2, John Willis2, A. Brady Self2, Emily B. Schultz2 James C. Rainer4
Mississippi State University, Department of Forestry, 1 Graduate Research Assistant, 2 Committee Member, 3 Major Professor 4 MDWFP
Abstract
Results
Increased oak regeneration benefits timber production as well as a number of wildlife species that are found within bottomland hardwood systems. Partial harvesting and midstory control are two silvicultural operations used to increase light availability, which is essential for oak seedling survival. Oak seedlings generally require 25% available light to survive, but closed canopy hardwood forests provide less than 10% (Gardiner and Hodges 1998). In addition to the reduction due to closed canopies, available light is also limited in these systems due to dense midstory components.
Sivicultural operations such as partial harvest and midstory control may be used in conjunction to increase light availability on the forest floor. Six sites were chosen for this study to evaluate the effects of partial harvest and midstory control on light availability and oak regeneration responses. The study plan contained six treatments assigned with random residual basal areas replicated across the six study sites, which included 70ft2/ac, 60 ft2/ac, 50ft2/ac, 40ft2/ac, 30ft2/ac, and a non-treated control. Results showed a target basal area of 50ft2/ac in theory optimized oak regeneration for this study more significantly than any other treatments.
Table 1. Abundance of oak seedlings based upon 1/100th acre plots
taken in each treatment
Treatment Category
1/100th-ac plots
Total Oak Seedlings1
Oak Seedlings Per Acre1 30 25
135AB
2704AB 40 20
86B
1710B 50
318A
6365A 60 15
110AB
2193AB 70 10
125AB
2500AB
control
59B
1170B
1 Means followed by the same letter do not differ at α=.05
Considerable differences were obvious in the comparison of mean values for each treatment area shown in (Table 1.). The average quantity of oak seedlings across all regeneration plots located within the residual basal areas indicated that the 50ft2/ac treatment maximized oak regeneration. Oak regeneration averaged 59 seedlings (1,170/ac) in control areas. In comparison, there were 135 seedlings (2,704/ac) in the 30ft2/ac areas, 86 seedlings (1,710/ac) in the 40ft2/ac areas, 319 seedlings (6,365/ac) in the 50ft2/ac areas, 110 seedlings (2,193/ac) in the 60ft2/ac areas, and 125 seedlings (2,500/ac) in the 70ft2/ac areas.
Results show a target of 50ft2/ac in theory optimized oak regeneration for this study, but it was only significantly different from the control areas and the 40ft2/ac treatment areas. Partial harvesting to 50ft2/ac created more favorable conditions to support a more significant amount of oak seedlings in the understory as compared to any other treatments. The 50ft2/ac treatment increased oak seedlings by 3,661/ac when compared to the 30ft2/ac treatment. Although the residual basal area of 30ft2/ac exhibits a higher level of available light, it resulted in a significantly lower quantity of oak regeneration when compared to the 50ft2/ac treatment. Janzen and Hodges (1986) stated that partial harvest this heavy could potentially be unsuccessful due to fast growing herbaceous vegetation and more shade intolerant species dominating the site. Furthermore, the 50ft2/ac treatment had 3,865 more seedlings per acre than the 70ft2/ac treatment in this study.
Introduction
According to the review of literature a specific numerical residual target basal area needed to create these optimal results mentioned above for oak regeneration seems to still be unknown.
A lack of clear relationship between a specific target basal area and oak regeneration responses could actually be influenced by numerous factors. Some of which include: trees per acre, size of residual stems, and species of residuals. Basal area of residual stems is an efficient target that may be used in conjunction with other considerations to optimize oak regeneration in bottomland hardwood forests.
This research quantified the influence of partial harvests and midstory control on oak regeneration response.
The primary objective of this study was to evaluate oak regeneration responses one year after midstory control and partial harvest treatments were applied.
Conclusions and Discussion
Research cannot repeatedly demonstrate that a target basal area of 50ft2/ac will allow oaks to become a majority of the future stand composition. It does, however, increase their potential by allowing seedlings to develop into adequate levels of advance regeneration before complete overstory removal.
The fact that this data had only been collected one year post-treatment may also be a relevant factor. More time may be needed to observe the results that light availability has on growth and abundance of oak seedlings. Ongoing collection of data moving forward will determine the true effectiveness of these applied treatments on oak regeneration by further observation of seedling growth. Further post-treatment sampling and analysis in these areas will determine if the treatment applications did in fact increase the growth of seedlings and allow for further development into adequate stocking levels of advanced oak regeneration. As the advance regeneration ages, results will be differentiated.
Materials and Methods
Study Sites: Located in Oktibbeha, Winston, and Noxubee counties in Mississippi on the John W. Starr Memorial Forest, Sam D. Hamilton Noxubee Wildlife Refuge, and C.A. Barge Timberlands.
The study was a randomized complete block design, blocked by study site using one replication per site for a total of six replications (County Line, Ennis, Bluff Lake, GTR 2, Barge, and Barge Pig).
Each replication was a 20 acre area, which was further divided into four, five-acre treatment areas (i.e. Experimental units).
Experimental units were randomly assigned one of the six treatments defined as target residual basal areas (70ft2/ac, 60 ft2/ac, 50ft2/ac, 40ft2/ac, 30ft2/ac, or an untreated control).
All partial harvest areas received a midstory control prior to harvesting using a 20% aqueous solution of imazapyr applied by hack and squirt.
Five 1/5th acre plots were established in each five-acre treatment area prior to harvest in order to obtain inventory cruise data used to calculate pre-harvest basal area/plot.
Timber was marked in accordance with Putnam’s hardwood tree classes to achieve residual basal areas. (Residual basal areas had to be reevaluated due to storm damage that occurred in April 2011).
Five 1/100th acre plots were established to measure oak regeneration abundance/height per treatment area totaling 120 plots for the study.
Plot centers were marked by a 6 inch segment of 0.5 inch pipe (PVC). Aluminum tags were used to indicate treatment/plot information.
Plots were located inside treatment areas using a 60ft buffer from outer boundary lines to avoid any external influences on the data.
Oak seedlings were classified into height categories and recorded. Height classifications were: <1ft, 1-3ft, and >3ft.
Statistical Analysis Systems (SAS) software version 9.2 was used to determine if basal area can be used as a predictor for oak regeneration. Univariate procedure created means as values for each unit.
Acknowledgements
Gardiner, E.S., and J.D. Hodges Growth and biomass distribution of cherrybark oak (Quercus pagoda) seedlings as influenced by light availability. Forest Ecology and Management 108:
Janzen, G.C. and J.D. Hodges Development of advanced oak regeneration as influenced by removal of midstory and understory vegetation. Pages in Proceedings of the Fifth Biennial Southern Silvicultural Research Conference. USDA, Forest Ser. Gen. Tech. Rep. SO-74. Atlanta, Georgia.
Barge Forest Products Co. & C.A. Barge Timberlands, L.P.