Doctoral Dissertations

Date of Award

8-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Natural Resources

Major Professor

Wayne K. Clatterbuck

Committee Members

David S. Buckley, Charles Kwit, Callie J. Schweitzer

Abstract

The repetitious use of diameter-limit harvesting in upland hardwoods has led to low-valued stands with understory canopy layers containing mostly shade-tolerant species. Desirable, shade intolerant reproduction is limited to regenerate these stands. This study evaluated the effectiveness of post-harvest herbicides (glyphosate and sulfometuron methyl) and application methods to accelerate the growth of natural oak advance reproduction. Treatment areas received clearcut treatments in the late winter/early spring of 2014. Six treatment units were established using banded foliar sprays, radial release sprays, pre-emergent broadcast sprays, or combinations of methods, along with an untreated control. Permanent regeneration plots were measured pre-harvest and after harvest (fall 2014) to evaluate the regeneration response. Individual white and red oak species along with yellow-poplar seedlings were measured for ground line diameter and overall height. Second measurements were taken in the winter of 2017 (two growing seasons later) to determine diameter and height growth change. Yellow-poplar and oak species reproduction per acre estimates, for the 2017 measurements, for block A, B, and C were 850, 1,900, and 233 seedlings. Shade intolerant reproduction formed a greater abundance compared to the shade tolerant species. It is proposed that the larger shade tolerant reproduction present before harvest was completely removed during the timber harvest activity. Significant differences were found between herbicide applications for absolute ground line diameter change for combined seedlings (P=0.0037), absolute height change for combined seedlings (P<0.0001), diameter growth among species (P=0.02988), height growth among species (P=0.0399), diameter change for sprout reproduction (P=0.0268), height change in new germinant reproduction (P=0.0245), height change for sprout reproduction (P<0.0001). Change in ground line diameter for yellow-poplar new germinants was significant (P=0.0161). The change in height comparisons for the species with size class found yellow-poplar sprout reproduction (P=0.0031), white oak new germinant and sprout reproduction were different (P=0.0152 and P<0.0001, respectively). Sulfometuron methyl only treatments typically had the greatest growth responses while radial treatments using glyphosate performed the poorest. A dense coverage of grasses established following herbicide applications. The emergence of grass likely reduced growth rates due to altered microenvironments as well as competition for root zone growing space, soil moisture, and nutrients.

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