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Mammal-plant dynamics in forests: interactions and implications for understory plant diversity

Royo De Sedas, Alejandro (2005) Mammal-plant dynamics in forests: interactions and implications for understory plant diversity. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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In forest communities, the composition and abundance of plants in the understory is generally mediated via a complex interplay between herbivory and competition. Nonetheless, most research assesses the effect of herbivory and competition independently and rarely investigates potential interactions between the two factors. In this dissertation, I examine how herbivory and competition, alone and in concert, influence forest understory plant diversity. At one extreme, herbivory is hypothesized to reduce interspecific competition, thus allowing for greater species coexistence in the understory. In chapter one, I test this hypothesis in the herbaceous community of a tropical forest in central Panamá. I found mammals limited the abundance of the dominant herbs while simultaneously limiting the establishment of rare species. In contrast, intense herbivory may reduce the diversity of the most palatable species allowing browse-resistant species to rapidly expand and overtake the forest understory. In chapter two, I explore this alternative by reviewing the processes leading to the formation of recalcitrant understory layers worldwide and summarizing the mechanisms by which these layers inhibit tree seedling regeneration and alter forest succession. In chapter three, I experimentally examining how a recalcitrant understory layer limits tree species recruitment via direct competitive as well as indirect, apparent competitive interactions. Specifically, by providing a favorable microhabitat for small mammals, a dense understory canopy can facilitate increased granivory, thereby indirectly limiting tree recruitment. I found a dense hay-scented fern (Dennstaedtia punctilobula) understory exerts strong apparent competitive effects on the emergence of black cherry (Prunus serotina) and strong competitive effects on emergence and survival of red maple (Acer rubrum). In chapter four, I explore the potential interactions between white-tailed deer (Odocoileus virginianus) and a dense canopy of hay-scented fern. This work demonstrates that in light limited, closed-canopy forests, a dense understory layer strongly suppresses germination and survival of several shade intolerant tree species. Furthermore, I argue that century-long legacy of deer overbrowsing has resulted in a depauperate forest community that predisposes future declines in plant diversity and increased monodominance. In all, these findings stress the need to discriminate among multiple ecological factors and assess their relative importance in structuring natural communities.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Royo De Sedas,
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairCarson, Walter Pwalt@pitt.eduWALT
Committee MemberMerritt, Joseph
Committee MemberRelyea, Rickrelyea@pitt.eduRELYEA
Committee MemberHorsley, Stephen
Committee MemberTonsor, Stevetonsor@pitt.eduTONSOR
Date: 10 October 2005
Date Type: Completion
Defense Date: 27 June 2005
Approval Date: 10 October 2005
Submission Date: 4 August 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: forest understory; herbaceous; interference; plant competition; regeneration
Other ID:, etd-08042005-214212
Date Deposited: 10 Nov 2011 19:56
Last Modified: 15 Nov 2016 13:48


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