The goal of research is to understand cause and effect relationships and how an ecosystem works or is assembled. Research is generally focused on answering a specific question about a particular area, organism, or ecosystem. Analyses may fully answer the question, or reveal new relationships and processes to explore. Highlighted below are just a few recent or ongoing research questions being investigated in Denali National Park and Preserve – some of which were developed by observing species around the Park during plant and soil inventories, and others that were developed while browsing preliminary data from vegetation monitoring projects (the same data used extensively in creating the maps, plots, and charts you will encounter while browsing species in the Ecological Atlas).
When is Green-up? Tracking Aspen Phenology
In 2005, park botanists began monitoring the phenology (or timing) of flowering, leaf-out, and senescence in aspen (Populus tremuloides), a widely distributed species in Alaska. Evidence from similar studies across North America indicates that climate change is advancing the timing of flowering and green-up, thus extending the growing season. This trend is especially apparent at northern latitudes and high elevations, so tracking phenological timing of aspen in Denali and other central Alaskan parks may reveal important trends. Changes in the phenology of flowering and leaf-out have significant consequences on many aspects of the ecosystem including plant growth, plant reproduction, and plant and animal interactions. Initial findings from Denali suggest that warmer spring temperature is the biggest driver of advanced green-up and extended growing seasons. Long-term phenology monitoring will provide insight on what environmental factors trigger phenology and how phenology may be affected by climate change. Identical monitoring of aspen phenology also occurs in Yukon-Charley National Rivers Preserve and Wrangell-St. Elias National Preserve, allowing for comparisons across gradients of elevation and latitude.
- Plant Phenology Resource Brief (274 KB PDF). National Park Service, Inventory and Monitoring Program, Central Alaska Network.
Understanding Relationships Between Temperature and Elevation
Together Denali National Park and Preserve, Yukon-Charley Rivers Preserve, and Wrangell-St. Elias National Park and Preserve span a vast area of interior Alaska. As you travel between them, one prominent difference you may notice is the elevation at which woody vegetation ceases to dominate the landscape. For example, treeline, shrubline, and tundraline are 200 to 400 meters higher in Wrangell-St. Elias and Yukon-Charley than in Denali! In order to understand and explain these differences, researchers began collecting data on air and soil temperatures, depth of living material, depth of organic layer in the soil, and vegetation characteristics in all three regions in 2010. Preliminary results indicate that while air temperature varies greatly between the three parks soil temperatures remain largely consistent and are closely related to the overlying vegetation type – important information when considering how predicted climatic warming may affect land cover change.
The Cyclical Nature of White Spruce Reproduction
Monitoring of white spruce (Picea glauca) in Denali National Park and Preserve began in 1992 and has produced one of the longest records of seed production and viability in Alaska. Park botanists measure diameter growth, cone production, seed production, and seed viability at permanent plots set in the forest and at treeline. Results from this data suggest that spruce cone production occurs on approximately 3 year cycles, cone production does not equate to viable seed production, and that seed fall and seed viability are determined by regional and local climatic conditions of the previous years. Understanding the limitations and cyclical nature of spruce reproduction is critical to understanding and predicting the conversion of shrub- and tundra-dominated landscapes to forested ones.
- Roland, C.A., J.H. Schmidt, and J. Johnstone. 2014. Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests. Oecologia 174: 665-677.
The World’s Rarest Lichen?
Denali National Park and Preserve is home to a lichen species considered one of the most endangered in the Northern Hemisphere! In 2007, while conducting the nonvascular plant inventory, Park botanists discovered several populations of the globally rare boreal felt lichen (Erioderma pedicellatum) in the moist mixed conifer-deciduous forests on the southern slopes of the Alaska Range. Following this discovery, researchers set out to describe the species occupancy patterns and abundance and found that the boreal felt lichen was relatively common in a wide range of spruce forest conditions found within the Park! In fact, Denali’s estimated population increases the previously known world population ten-fold! Although apparently healthy, Denali’s boreal felt lichen populations may be monitored in the future as changes to regional air quality or climate may threaten their health as has occurred in other locations.
- Nelson, P.R., J. Walton, and C.A. Roland. 2009. Erioderma pedicellatum (Hue) P.M. Jørg, New to the United States and Western North America, Discovered in Denali National Park and Preserve and Denali State Park, Alaska. Evansia 26: 19-23.
- Stehn, S.E., P.R. Nelson, C.A. Roland, and J.R. Jones. 2013. Patterns in the occupancy and abundance of the globally rare lichen Erioderma pedicellatum in Denali National Park and Preserve, Alaska. Bryologist 116(1): 2-14.
To the Alpine! – Where Species Diversity is Highest
Recent research on elevational gradients of vascular and non-vascular plant diversity in Denali produced some surprising and unique insights with global relevance. Plant species diversity of the three main functional groups – vascular plants, mosses, and lichens – is highest in alpine tundra and other sparsely vegetated areas of the park, and lowest in the more productive and less ‘harsh’ environs of the boreal lowlands there. The relationship between elevation and diversity has been studied a great deal by botanists across the globe, and Denali is one of few places such a pattern has been reported. Other studies show either a steep decline of plant diversity with increasing elevation, or else maximum diversity occurring in intermediate landscape positions where lowland and alpine species mix.
Our work suggests that Denali’s unique pattern of vascular diversity reflects the strong influence of glacial advance and retreat that has occurred over the past 2 million years. Boreal plant communities such as conifer and birch forest are relatively recent phenomena in Denali relative to the long duration of tundra and sparse vegetation communities that has persisted here through both glacial and interglacial periods in the past – and so there is a larger number of vascular species available that are adapted to alpine environments than to the more widespread and hospitable boreal lowlands.
One of the National Park Service’s primary missions is to manage and conserve native biodiversity in lands they manage, thus it is important to understand the patterns and processes that have produced and will sustain this biodiversity.
- Roland, C.A. and J.H. Schmidt. 2015. A diverse alpine species pool drives a ‘reversed’ plant species richness–elevation relationship in interior Alaska. Journal of Biogeography 42: 738-750.
- Roland, C.A., S.E. Stehn and J.H. Schmidt. 2017. Species richness of multiple functional groups peaks in alpine tundra in subarctic Alaska. Ecosphere 8(6):e01848.
- Stehn, S.E. and C.A. Roland. 2018. Concordant community similarity patterns across functional groups in subarctic plant assemblages. Ecosphere 9(4):e02181.
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