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Photosynthetic adaptation in terrestrial vascular plants involves a complex interaction of components that extend across a broad structural and spatial hierarchy, often functioning in concert with one another at multiple scales. Thus, understanding the evolutionary mechanisms leading to these adaptations requires evaluation across the entire spectrum of plant form from the chloroplast to the landscape. Adaptive traits across this structural/spatial hierarchy can emerge at any level and then feed-back or feed-forward to cause adaptive changes at adjacent levels. Today's sophisticated instruments enable direct measurement of photosynthesis at most of these hierarchical levels and across phylogenetic boundaries. As a result, identification of functional properties in plant form (architectural and spatial), independent of physiological processes, is becoming a reality. In this review we focus on one apparent theme across this hierarchy of organizational complexity—the impact of plant form on the distribution of incident sunlight to photosynthetic surfaces, and the transfer and processing of mass nutrients (e.g. CO2 and water). The trade-offs and net effects of these exchange processes drive photosynthetic adaptation, and appear to be related to economic efficiencies rather than simply magnitude.
Because of ongoing debate over the long term impacts of logging, we conducted a study to assess if second growth (70 ± 10 years) rich coves differ from old growth rich coves (> 125 years) in species diversity or composition. We sampled twenty-six 0.1 ha plots, representing these two age classes. We distributed the plots amongst three randomly selected mountain ranges in the southern Appalachians of North Carolina, and sampled each mountain range in separate years. We used nested subplots of 0.01 m2, 0.1 m2, 1 m2, 10 m2, 100 m2, and 1000 m2 to establish species-area relationships (SARs) for each age class. We found no significant differences between the SARs for the two age classes, nor did we find significant differences between age classes using the Simpson, Shannon-Wiener, or Sorensen indices of species diversity. However, we found that total cover of all plant species was greater in old growth rich coves, and that 10% of the tested species had lower abundance in second growth. No species were present in old growth and absent in second growth, but species with lower second growth abundance may warrant future study.
Delphinium newtonianum (Ranunculaceae) is a rare endemic of the Interior Highlands. Using a single-copy nuclear gene, genetic diversity was determined for eight populations. Genetic diversity in D. newtonianum is high (37 haplotypes were identified from 80 individuals) and haplotype diversity was 0.885 0.016. Analysis of genetic structure indicates that populations within the Ozark region do not show significant genetic differentiation due to a high level of gene flow. However, Ouachita populations have undergone genetic drift and the loss of genetic diversity relative to Ozark populations. In addition, all Ouachita populations are significantly differentiated from all other populations. A neighbor-joining tree based on p-distance identifies Ouachita populations as a monophyletic group most likely established from a single Ozark population. Ozark and Ouachita populations should be treated as two genetically distinct metapopulations and considered to be evolutionary significant units.
Cool Springs Environmental Education Center (CSEEC), owned by Weyerhaeuser Company, includes a 591 ha State Significant Natural Area. It is located in Craven County, North Carolina, in the floristically rich Atlantic Coastal Plain. A vascular flora inventory documented the occurrences of 567 species and sub-specific taxa and 303 genera in 118 plant families, including populations of the Atlantic Coastal Plain endemics Pondspice (Litsea aestivalis) and LeBlond's Coastal Goldenrod (Solidago villosicarpa). We identified twenty plant community types, including the uncommon Longleaf Pine (Pinus palustris) Woodland, Bald Cypress–Tupelo Gum (Taxodium distichum – Nyssa aquatica) Swamp, a number of small depression wetland communities, and the novel Sand Laurel Oak-Loblolly Pine (Quercus hemisphaerica – Pinus taeda) Woodland. Soils ranged from excessively drained sands to very poorly drained organics. The order of the soil mapping units according to the number of plant taxa they supported per unit area was TaB > PO > Ln > Mu > DO, MM > Se > KuB. Among five of 12 floristic study sites having positive residuals in the regression of log species richness on log area, CSEEC had the third largest residual. There was no relationship between the residuals from regressions of log species on log area and soil drainage heterogeneity on log area. The occurrences of two rare plant species, a species-rich flora, ten natural plant community types, and an assemblage of wet and dry soils in a variety of geomorphic settings are objective factors justifying the recognition of CSEEC as a State Significant Natural Area.
The Cucumber Creek Nature Preserve is located in the Ouachita Mountains of southeastern Oklahoma, a region of high plant diversity in the state. An inventory of the preserve yielded 341 taxa of vascular plants in 231 genera and 98 families. The largest families were the Asteraceae (46) and Poaceae (27). The flora consisted of 52 annuals, 1 biennial, 287 perennials, and 95 woody taxa. Sixteen exotic species were collected, representing 4.7% of the flora. Twenty-five species were present that are tracked by the Oklahoma Natural Heritage Inventory: Actaea pachypoda, Carex cephalophora, C. latebracteata, C. ouachitana, C. striatula, Castanea pumila var. ozarkensis, Chionanthus virginicus, Dirca palustris, Fraxinus quadrangulata, Galium arkansanum, Halesia tetraptera, Hamamelis vernalis, H. virginiana, Hypericum gentianoides, Ilex opaca, Iris cristata, Magnolia tripetala, Mitchella repens, Panax quinquefolius, Piptochaetium avenaceum, Polygala polygama, Ribes cynosbati, Spigelia marilandica, Stachys eplingii, and Uvularia grandiflora.