The ecological response of lianas to habitat fragmentation of a tropical rainforest
Campbell, Mason James (2016) The ecological response of lianas to habitat fragmentation of a tropical rainforest. PhD thesis, James Cook University.
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Abstract
More than half of the pre-industrial cover of tropical forest has been lost. Tropical forests are the pinnacle of terrestrial diversity, and thus their destruction threatens global biodiversity more than any other contemporary human practice. As forests are cleared, isolated fragments of the original vegetation are left, surrounded by new habitat types. This forest fragmentation is occurring on an immense scale throughout the tropical regions of the world, with estimates suggesting that fragments now comprise as much as 46% of the remaining tropical forested area. Furthermore, as tropical deforestation and land-use conversion continue unabated the proportion of tropical forests in fragments will increase.
After deforestation, fragmentation likely poses the biggest threat to global diversity. Fragmentation threatens diversity as it alters the environmental and ecological characteristics of tropical forests, degrading their ability to support biodiversity. Moreover, fragmentation degrades the complex system of ecological interactions that occur within tropical forests. Yet, despite this, forest fragments preserve many rare and endangered species and threatened ecosystems and are thus valuable for biodiversity conservation. However, if the conservation values of tropical forest fragments are to be maximized they must not only be retained but their internal ecological interactions must be effectively managed.
Determining how lianas (woody vines) interact with trees and other flora within fragmented tropical forests is important for effective biodiversity conservation. Lianas threaten tree diversity within fragments as they can proliferate and infest trees causing their host structural stress whilst competing with them for resources. Liana infestation can also lead to decreased tree seedling recruitment, damage to saplings, decreased tree growth and fecundity, and increased tree mortality. Consequently, lianas can have fragment-wide impacts that can result in the decline or extirpation of vulnerable tree species or guilds leading to a depauperate tree community. Within this thesis I examined the ecological mechanisms underlying the detrimental interaction between lianas and their tree hosts, the drivers of the positive liana (sensu lato) response to forest fragmentation and the ecological impacts of lianas on other members of the vegetative community of forest fragments. This study occurred within the intact and fragmented forests of the Atherton Tableland, northeastern Queensland, Australia.
First, to assess liana abundance and tree infestation rates I examined the relationship between these parameters and their environmental and ecological drivers at a landscape level (comparing fragmented to intact forest) and within forest fragments (23-58 ha). Within these sites, I also examined the response of the liana climbing guild composition to fragmentation. Fragmentation increased liana abundance and altered liana-host tree interactions and the composition of liana climbing guilds. I found that the increased disturbance of fragment edges and in particular the increase in light and climbing trellis availability within fragments, was significantly related to the increase in liana abundance. However, the rate of liana infestation of trees was not only positively related to liana abundance but also liana size (diameter at breast height), with large lianas predominantly occurring within less disturbed areas of fragments. As such, an alleviation of liana impacts upon forest fragments could occur through effective management of the disturbance of fragment edges and large liana management (i.e. cutting).
Second, very little research exists on the impact of lianas on non-tree life forms of the vegetative community of tropical forests. Epiphytes comprise a significant component of tropical forest diversity and provide resources for a diverse community of resident species. To assess the impact of lianas on epiphytic ferns within fragments I compared their respective abundances and spatial arrangements to that of the resident trees. I found that lianas compete intensely with epiphytes on the edges of forest fragments for the structural hosts (trees) needed by both life forms. This competition imperils epiphytic ferns and the reliant diversity of fauna they support. As the first study of its kind, my finding of lianas negatively impacting Old World epiphytic ferns should focus research on liana-epiphyte interactions both within the region and throughout the tropics.
Third, rattans (climbing palms) are arguably the world's most important non-timber forest product and emblematic of the Old World climbing plant community. Yet, rattan species of many regions are threatened with extinction through forest conversion, landscape modification and unsustainable harvesting. Though monocotyledonous rattans are included as lianas (sensu lato) within landscape ecological studies, it is unknown whether they respond similarly to fragmentation and ecological and environmental drivers. I examined how fragmentation has impacted rattan abundance and demography. I found a strong proliferation of rattans and in particular adult rattans in response to fragmentation. Again this proliferation is due to the increased disturbance of forest fragments and the subsequent decreased canopy cover. My findings also provide new insight into the world of climbing plant competition, with rattan proliferation possibly occurring at the expense of lianas due to rattans superior inter-host colonization ability which allows them to infest more widely-spaced tree hosts in heavily-disturbed forest fragments. This hypothesis provides a basis for future research whose outcomes could influence stocking densities of rattans allowing for maximization of rattan output whilst minimizing liana management costs.
Fourth, the vast majority of the liana literature provides almost constant reminders of the negative impact lianas have on trees, forest dynamics and forest functioning. As our understanding of lianas increases it is becoming clear, however, that lianas are a diverse and integral component of a functioning tropical forest. Consequently, for the first time, I synthesized information from across diverse topics dealing with lianas to provide a focused assessment of the potential for lianas to expedite rain forest recovery. The restoration practices I and my colleagues suggested are the first time an explicit list of potential liana uses within restoration has been constructed. Moreover, the listing of these suggested practices allows for field trials by restoration practitioners.
The findings reported in this thesis further our understanding of the ecological responses of lianas (sensu lato) to tropical forest fragmentation. In particular, they provide information on liana ecology within the fragments of the World Heritage listed tropical forests of northeastern Australia. This information will be informative to rain forest managers of the region, who are tasked with conserving these exquisite and irreplaceable forests. The results corroborate the literature on many fundamental points of liana ecology and forest dynamics, while providing new insights into the relationship among the lianas, rattans, trees and epiphytes of forest fragments.
| Item ID: | 49720 |
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| Item Type: | Thesis (PhD) |
| Keywords: | Atherton Tablelands, biodiversity, climate change, competition, disturbance, ecological response, ecophysiology, edge effects, ferns, forest fragmentation, fragmentation, fragmented forest landscapes, fragmented tropical forests, large tree mortality, liana abundance, lianas, logging, plant-plant interactions, point-pattern analysis, rattans, vines, Wet Tropics of Queensland World Heritage Area, Wet Tropics |
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| Additional Information: | For this thesis, Mason Campbell received the Dean's Award for Excellence 2017. Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 1: Campbell, Mason, Laurance, William F., and Magrach, Ainhoa (2015) Ecological effects of lianas in fragmented forests. In: Schnitzer, Stefan A., Bongers, Frans, Burnham, Robyn J., and Putz, Francis E., (eds.) Ecology of Lianas. Wiley-Blackwell, Hoboken, NJ, USA, pp. 443-450. Chapter 2: Campbell, Mason, Magrach, Ainhoa, and Laurance, William F. (2015) Liana diversity and the future of tropical forests. In: Parthasarathy, N., (ed.) Biodiversity of Lianas. Sustainable development and biodiversity, 5 . Springer International Publishing, Cham, pp. 255-274. Chapter 4: Magrach, Ainhoa, Rodríguez-Pérez, Javier, Campbell, Mason, and Laurance, William F. (2014) Edge effects shape the spatial distribution of lianas and epiphytic ferns in Australian tropical rain forest fragments. Applied Vegetation Science, 17 (4). pp. 754-764. Chapter 5: Campbell, Mason J., Edwards, Will, Magrach, Ainhoa, Laurance, Susan G., Alamgir, Mohammed, Porolak, Gabriel, and Laurance, William F. (2017) Forest edge disturbance increases rattan abundance in tropical rain forest fragments. Scientific Reports, 7. pp. 1-12. Chapter 6: Campbell, Mason J., Edwards, Will, Odell, Erica, Mohandass, Dharmalingam, and Laurance, William F. (2015) Can lianas assist rainforest restoration? Tropical Conservation Science, 8 (1). pp. 257-273. |
| Date Deposited: | 30 Jul 2017 23:38 |
| FoR Codes: | 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050102 Ecosystem Function @ 50% 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 35% 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050104 Landscape Ecology @ 15% |
| SEO Codes: | 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960505 Ecosystem Assessment and Management of Forest and Woodlands Environments @ 50% 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960806 Forest and Woodlands Flora, Fauna and Biodiversity @ 35% 96 ENVIRONMENT > 9613 Remnant Vegetation and Protected Conservation Areas > 961306 Remnant Vegetation and Protected Conservation Areas in Forest and Woodlands Environments @ 15% |
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