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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

HARDWOOD REGENERATION AND GROWTH FOLLOWING MULTIPLE SILVICULTURAL TREATMENTS IN A CENTRAL HARDWOOD FOREST

Inglis, Emily 01 May 2022 (has links)
The Central Hardwood Region (CHR) is experiencing a lack of desirable hardwood regeneration on productive sites across the landscape. To better understand what facilitates desirable hardwood regeneration, additional studies that test the interaction of multiple disturbances are needed. For this reason, a demonstration area on the north end of Trail of Tears State Forest (Union County, Illinois) was established to compare hardwood regeneration response following four treatments: (1) burn only, (2) thin/burn, (3) harvest/thin/burn, and (4) control. Treatments were implemented beginning in 2014 to determine what combination of silvicultural practices best promotes desirable hardwood regeneration among large saplings (>3.3’ in height and 1” DBH to 3” DBH), small saplings (>3.3’ in height and up to 1” DBH), and seedlings (1”- 3.3’ in height) and increases midstory Quercus alba radial growth (stems >3” DBH). Eighty plots were surveyed in the summer of 2021, and overstory, regeneration, and canopy openness data were collected. Midstory Q. alba individuals were cored to elucidate the relationship of radial growth and silvicultural treatments. There was no significant difference of Quercus spp. density among treatments for any regeneration size class. No silvicultural releases were detected in midstory Q. alba individuals since treatment application in 2014. These results indicate that either there had not been enough time since treatment application, or the management practices did not alter canopy openness enough to cause a radial growth increase. Given the absence of Quercus spp. regeneration and growth using the four treatments, I suggest managers should also consider other factors such as deer population densities, non-Quercus competition vigor, and forest floor light availability when attempting to regenerate productive forests in the CHR.
2

Succession of an Upland Oak/Hickory Forest in the Central Hardwood Region

Hoover, Nathan 01 August 2018 (has links)
For the last 9,000-10,000 years the Central Hardwood Region (CHR) has been primarily composed of a mosaic of mesophytic communities in climax and communities of successional forest types dominated by oak (Quercus Linnaeus) and hickory (Carya Nuttall). Shade intolerant oak/hickory dominated forest types have been maintained by natural disturbance processes in synergy with anthropogenic causes, resulting in a large composition of communities which are neither at climatic nor edaphic climax. Reduction in fire events, thinning, forest grazing, and other disturbance processes over the last 80-100 years have coincided with decreased regeneration of shade intolerant species due to lack of adequate light availability and recruitment of shade tolerant species of communities dominated by American beech (Fagus grandifolia L.) and maple (Acer saccharum L.) into the overstory of forests typically dominated by oak/hickory. Forest inventory data at Trail of Tears State Forest was analyzed across two separate time events (1980 and 2014) to determine compositional and structural changes which have occurred. Density, basal area, and community patterns via ordination were compared across six Ecological Land Types (ELTs) to determine topography’s effect on composition. Community trends were analyzed via NMS Ordination and between ELTs by a Mantel Test. A Multi-Response Permutation Procedures (MRRP) was also used as a nonparametric method for assessing differences between ELTs examined in the NMS. Density and basal area between years for species, ELT, and species*ELT interactions were compared. Across all ELTs, between 1980 and 2014, overstory density decreased from 218 trees/ac in 1980 to 180 trees/ac in 2014 and basal area increased from 98 ft2/ac in 1980 to 106 ft2/ac in 2014. Maple basal area increased from 5 ft2/ac to 12 ft2/ac while beech increased from 1 ft2/ac to 8ft2/ac, signifying progression of these species from the understory up into the canopy. The component of soft masting species within the forest has also decreased sharply in the last 34 years. MRPP analysis of overstory compositional gradients reported distinct species compositions between ELTs, however the trend was weak (MRPP: p < 0.001, A = 0.038). NMDS ordination graphs confirmed MRPP showing little separation among ELTs. The final stress was 18.71146 and instability was < 0.01 after 212 iterations (Table 6). Our research at TTSF is a clear example of oak/hickory succession to beech maple on an upland site among species community types as delineated by topographic moisture gradient (ELTs) within the CHR. Expansion of beech and maple onto xeric ELTs suggests a breakdown of edaphic barriers that have previously been thought to be resistant to encroachment from mesophytic species. Currently oak decline induced by lack of management is likely the number one forest health issue resulting in loss of oak/hickory and other soft masting species.

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