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Understanding how plant communities of the past have responded to disturbance events can provide valuable insights when managing our natural resources and assessing human impacts on ecosystems. The geologic record has the potential to reflect these responses through the analysis of functional traits, which relate directly to plant function and ecosystem strategy. There is currently little evidence of how functional traits measurable in fossil leaves vary across succession in different forest types. Because of this, there is a limited ability to identify disturbance as the primary driver of vegetation change within the fossil record. To improve this ability, this study analyzes the carbon stable isotopic composition (δ 13C) of bulk organic matter sampled at the community-scale across successional gradients in a temperate deciduous forest (North Carolina, USA) and compares them against values from a previous study across succession in a tropical evergreen forest (Malaysian Borneo). Leaf δ13C is representative of a plant's water use efficiency (WUE), an important axis of ecological strategy representing the carbon assimilated per water lost in a plant during photosynthesis. Leaf δ13C as a functional trait has the advantage that it is often preserved during leaf fossilization and, integrated across a plant community, can be informative about prevalent ecological strategies, functional diversity , and community assembly dynamics. In Borneo, the community-weighted mean of leaf δ13C to be highest in early-succession plots, indicative of a higher WUE in plant communities closely following a disturbance event. Old growth plots were found to have a lower δ13C, and thus a more conservative WUE. This study will further investigate if this trend is followed within temperate forests, which is important as many mid-late Cenozoic plant assemblages come from what would have been temperate regions. Developing a method of identifying disturbances within the geologic record, will improve the ability to discern drivers of plant community change in the past. This improved knowledge will help guide management decisions across a range of ecosystems.
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Fossil fern rhizomes as a model system for exploring epiphyte community structure across geologic time: evidence from Patagonia
BackgroundIn extant ecosystems, complex networks of ecological interactions between organisms can be readily studied. In contrast, understanding of such interactions in ecosystems of the geologic past is incomplete. Specifically, in past terrestrial ecosystems we know comparatively little about plant biotic interactions besides saprotrophy, herbivory, mycorrhizal associations, and oviposition. Due to taphonomic biases, epiphyte communities are particularly rare in the plant-fossil record, despite their prominence in modern ecosystems. Accordingly, little is known about how terrestrial epiphyte communities have changed across geologic time. Here, we describe a tinyin situfossil epiphyte community that sheds light on plant-animal and plant-plant interactions more than 50 million years ago. MethodsA single silicifiedTodea(Osmundaceae) rhizome from a new locality of the early Eocene (ca. 52 Ma) Tufolitas Laguna del Hunco (Patagonia, Argentina) was studied in serial thin sections using light microscopy. The community of organisms colonizing the tissues of the rhizome was characterized by identifying the organisms and mapping and quantifying their distribution. A 200 × 200 µm grid was superimposed onto the rhizome cross section, and the colonizers present at each node of the grid were tallied. ResultsPreservedin situ, this community offers a rare window onto aspects of ancient ecosystems usually lost to time and taphonomic processes. The community is surprisingly diverse and includes the first fossilized leafy liverworts in South America, also marking the only fossil record of leafy bryophyte epiphytes outside of amber deposits; as well as several types of fungal hyphae and spores; microsclerotia with possible affinities in several ascomycete families; and evidence for oribatid mites. DiscussionThe community associated with the Patagonian rhizome enriches our understanding of terrestrial epiphyte communities in the distant past and adds to a growing body of literature on osmundaceous rhizomes as important hosts for component communities in ancient ecosystems, just as they are today. Because osmundaceous rhizomes represent an ecological niche that has remained virtually unchanged over time and space and are abundant in the fossil record, they provide a paleoecological model system that could be used to explore epiphyte community structure through time.
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- PAR ID:
- 10127322
- Publisher / Repository:
- PeerJ
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 7
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- Article No. e8244
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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