자료유형  

 학위논문

Control Number  

0016931487

International Standard Book Number  

9798379778996

Dewey Decimal Classification Number  

628

Main Entry-Personal Name  

Sullivan, Megan Kathleen.

Publication, Distribution, etc. (Imprint  

[S.l.] : Yale University., 2023

Publication, Distribution, etc. (Imprint  

Ann Arbor : ProQuest Dissertations & Theses, 2023

Physical Description  

1 online resource(194 p.)

General Note  

Source: Dissertations Abstracts International, Volume: 85-01, Section: B.

General Note  

Advisor: Comita, Liza S.

Dissertation Note  

Thesis (Ph.D.)--Yale University, 2023.

Restrictions on Access Note  

This item must not be sold to any third party vendors.

Summary, Etc.  

요약Tropical forests are increasingly threatened by anthropogenic disturbance; in particular, from income-generating land uses. Selective logging is often hailed as a compromise between strict conservation and intensive land-use industries. This compromise allows for use of the forest for economic development in developing countries while leaving much of the forest canopy intact across a landscape. However, the ecological impacts of selective logging are unclear. Previous work has resulted in mixed evidence about how selective logging impacts forest structure, diversity, composition, function, timber sustainability, and ecological interactions. Direct damage from logging activities and environmental shifts from logging gaps that open up the forest canopy certainly do have immediate impacts on vegetation, and the magnitude of direct impacts of logging activities is likely related to logging intensity. However, these initial impacts could be short-lived, temporary effects or selective logging could alter the successional trajectory of forests for longer time frames, resulting in persistent or lagged effects in the forest for decades or even centuries. How these impacts play out over time is uncertain. In my dissertation, I examined the impact of selective logging on a Congo Basin tropical rainforest in different plant life stages (seedlings, saplings, and adults) across a logging chronosequence to better understand how forests will respond logging over time. The three resulting chapters are:Chapter 1: A decade of diversity and forest structure: Post-logging patterns across life stages in an Afrotropical forest: Selective logging impacts on forest structure and diversity are conflicting, likely based on variation in what is considered low logging intensities. In logging concession with very-low intensity timber harvest (0.6-2 trees per ha), we tested whether forest structure (canopy openness, stem density, basal area, and relative liana abundances) and diversity were altered in forests that had been logged one year and ten years prior, compared to unlogged forest, in seedlings, saplings, and adults. Overall, we found that selective logging has a negligible impact on basal area, some positive effects on diversity, and a potential negative impact of increasing liana loads as recovery time increases. Based on our findings, one management suggestion we have would be to implement protocols to reduce liana proliferation in forests post-logging. There does seem to be a lagged signature of selective logging (higher diversity, higher relative liana abundances) that emerges in the sapling layer a decade after logging occurs. Whether these shifts are temporary or represent a lasting change that will affect future forests requires further, long-term study.Chapter 2: Composition dissimilarity, functional trait differences, and timber species regeneration in a selectively logged forest understory: Shifts in forest structure and diversity can be better understood if we know how species composition is changing and what characteristics give trees a competitive benefit in logged forests. Our findings suggest that impacts from very low-intensity selective logging in our study area were limited to small shifts in community composition which are most notable in the forest understory community. We did not find an indication of reduced carbon storage potential and found mixed effects of selective logging on animal-dispersed species and timber species. Overall, we note that very low-intensity selective logging had modest impacts on forest composition and function across our logged forests. Further study into the explicit impacts of selective logging on animals and animal seed dispersal would help to better understand what animals and animal-dispersed trees are most strongly impacted by logging. Additionally, further study on timber species regeneration over time would help determine what sustainable timber yields are in. Future research that focuses on dynamic vegetation patterns over time would help elucidate the drivers of compositional shifts in forest understory communities. Explicit study of selective logging impacts on animals and animal seed dispersal would help elucidate which animals and animal-dispersed trees are most strongly impacted by logging. Additionally, further study on timber species would help determine what appropriate timber removal rates are to ensure successful timber species regeneration in the long term in these forests.Chapter 3: Seedling dynamics across a selectively logged forest chronosequence: Static patterns can only tell us so much about selective logging impacts. Exploring vegetation dynamics patterns in the seedlings can help us better understand what ecological processes are impacted when a forest is logged and how these impacts might differ temporally in the recovery trajectory of a forest post-logging. We use dynamic seedling data across a four-year recensus period in our logged forest chronosequence to analyze what impacts selective logging has on (i) the understory environment, (ii) how the understory environment impacts seedling performance, and (iii) how selective logging impacts seedling performance immediately after logging and over longer timeframes, and whether these impacts differ between different plant growth forms (lianas vs. trees). Selective logging affected the understory environment - logged forests had higher light levels up to four years post-logging, more branch and tree fall up to fourteen years after logging. We also saw lagged effects of selective logging on the understory environment - animal trails were more prevalent in the fourteen-year-old logged forest. The understory environment - animal trails, logging and vegetation damage, and light levels - did impact seedling performance. Animal trails negatively impacted seedling survival and positively impacted recruitment. Logging and vegetation damage negatively impacted seedling survival but had positive impacts on growth. Selective logging had a negative impact on seedling performance during active logging and for up to four years after logging. Older logged forests (fourteen years post-logging) exhibited similar seedling dynamics as in unlogged forests. Additionally, selective logging impacted some different functional groups of plants differently than others - lianas had a growth advantage in forests immediately after logging. Overall, we note that selective logging has temporary shifts (i.e., cohort effects) on seedling dynamics processes, rather than long-term or lagged impacts (i.e., forest shifts).

Subject Added Entry-Topical Term  

Environmental science.

Subject Added Entry-Topical Term  

Environmental studies.

Subject Added Entry-Topical Term  

Forestry.

Subject Added Entry-Topical Term  

Conservation biology.

Index Term-Uncontrolled  

Biodiversity

Index Term-Uncontrolled  

Functional composition

Index Term-Uncontrolled  

Managed ecosystems

Index Term-Uncontrolled  

Seedling dynamics

Index Term-Uncontrolled  

Selective logging

Index Term-Uncontrolled  

Tropical forest

Added Entry-Corporate Name  

Yale University Ecology and Evolutionary Biology

Host Item Entry  

Dissertations Abstracts International. 85-01B.

Host Item Entry  

Dissertation Abstract International

Electronic Location and Access  

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Control Number  

joongbu:642256