| Hille Ris Lambers Lab |
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Implications of climate change for forests in the Pacific Northwest  How will climate change affect
the abundance and distribution of tree species in the Pacific Northwest? Coniferous
forests in the Pacific Northwest are among the most productive
ecosystems in the continental U.S, cover a large geographic
extent,
and
are the home to many plants and animals of conservation
interest. Thus, understanding how climate change will affect
this biome is critical; yet efforts are hampered by our limited
understanding of i) the climatic variables that affect the population
growth of
dominant tree species and ii) the rates at which trees species can
migrate in response to climate change. To address these question,
we monitor tree demography (growth, survival, seed production) and
microclimate (temperature, snow depth, soil moisture, date of meltout)
in 18 stands located across Mt. Rainier National Park. These 18 stands are part of a large scale network of permanent
vegetation plots located across the Pacific Northwest
(established by Jerry Franklin and
colleagues). With its 4300
meters in
elevation and strong rainshadow effect, Mt. Rainier is a microcosm of
climate zones and forest types found in the western part of Oregon,
Washington and British Columbia. It is thus a perfect place
to study how Pacific Northwestern Forests will respond to climate change. We use demographic and microclimate data to determine
the sensitivity of dominant conifers to climate variables likely to be
altered by global warming, and combine this information with forecasts
of future climate regimes and seed dispersal models to estimate range
expansion rates at upper altitudinal range limits. I collaborate with Jessica
Lundquist to quantify microclimate across Mt. Rainier.Funding: National Institute for Climate Change Research (Department of Energy), University of Washington Royalty Research Fund |
| Niches and neutrality in
diverse serpentine annual communities Are species interactions critical for the biodiversity of California's wildflowers? It’s safe to say that Steve Hubbell shook up the ecological world when he introduced community ecologists to the idea that species coexistence does not necessarily result from species interactions, but may simply occur because speciation balances extinction over long time scales. Traditionally, community ecologists have focused their research on “stabilizing” processes (sensu Chesson); those which lead to more negative intra-specific interactions than inter-specific interactions (e.g. resource niches, density-dependent natural enemies, storage effects). Hubbell’s work has forced community ecologists to consider the role of “equalizing” processes, that is, competitive equivalence (i.e. random walks in population sizes when species differ little in overall fitness). Today, ecological debate centers on the relative roles of stabilizing and equalizing processes in fostering coexistence locally. I am collaborating with Jonathan Levine to experimentally determine the importance of stabilized population growth, i.e. niches, for the coexistence of California serpentine annuals. We are quantifying the relationship between frequency and per-capita growth rates for ten serpentine annual plants in experimental gardens. This is key, because frequency-dependent negat  ive population growth is
the signature of all stabilizing niche processes. We are
also calculating population growth rates in the absence of
stabilization
to predict the magnitude of fitness differences in the absence of niches. Finally, we are manipulating seed
production to remove negative frequency dependence and
compare diversity and
extinction dynamics in finite stochastic communities in the presence
and absence of niche differences. Although many theoretical
and empirical studies demonstrate that particular diversity-promoting
mechanisms operate in natural communities, few studies attempt to
disentangle the relative roles of stabilizing vs. equalizing processes
in maintaining diversity, and none (that we are aware of) have
attempted an experimental approach. Results thus far
indicate that without frequency-dependent processes (i.e. niches),
diversity plummets and a single species would dominate our experiment
within 20 years. See our project website following for more details on this experiment.Funding: National Science Foundation |
| Nutnet: top-down and
bottom-up controls over herbaceous productivity and diversity What controls the biodiversity and productivity of rare Washington Prairie habitats? Nutnet is is designed to quantify how resource limitation vs. herbivory limits plant productivity and diversity in herbaceous dominated communities. This is of ecological relevance for the following reasons; i) the generality of multiple resource limitation in plant communities is unknown and debated; as is ii) the relative importance of top-down (i.e. herbivory) vs. bottom-up (i.e. soil resources) controls on plant productivity and diversity. Instead of performing a large experiment at one field site (the general ecological MO), Nutnet comprises a series of small, identical experiments run by a multi-collaborator network in a large number of sites. There are currently over 30 sites (most in the US, some in Europe, Africa and Australia) and 50 people involved - see the NutNet project website for more details. Treat  ments include nutrient additions
(N,P,K) and herbivore exclosures, with 10 treatments and 30 plots per
site. The large number of replicate sites participating
offers
the unique possibility of generalizing
these results to multiple regions. The project is a
brainchild of Peter Adler, Elizabeth Borer (Oregon State University),
Stan Harpole (UC Irvine), John Orrock, Eric Seabloom (Oregon State
University), and Melinda Smith (Yale University).Janneke Hille Ris Lambers and Jon Bakker (College of Forest Resources, University of Washington) are Washington regional PI's for the nutnet site at Smith Prairie, with Karen Reagan and Susan Waters as participating graduate students. Besides the broader Nutnet goals, these sites will also offer valuable regional insights. Many of western Washington’s prairies have been converted to agriculture or are close to urban centers. Both these landuse changes generally come with increased inputs of soil nutrients (particularly nitrogen and phosphorus). Herbivores are probably much more abundant now than they were historically in western Washington, due to the extirpation of their major predators (wolves, bears, lynxes). Western Washington grasslands are also being exposed to novel kinds and levels of herbivory, with the introduction of nonnative herbivores like rabbits and Canada Geese. Finally, exotic plant species represent one of the biggest threats to native diversity within these systems. Thus, understanding how plant diversity and the success of exotic plant species, like Canada thistle and Tansy ragwort, are influenced by nutrient addition and herbivore exclosures might aid conservation and restoration efforts in these rare Washington habitats. Funding: National Science Foundation |
| Other
Research In addition to the projects described above, I am also involved in several ongoing collaborations. Click on the links below for website links, article pdfs or recent talks for more information. 1. Implications of bird loss on the Marianas Islands for forest community dynamics 2. Factors contributing to the invasion of California by Mediterranean annual grasses |
| Janneke Hille Ris Lambers jhrl[at]u.washington.edu |
206
543-7389 (Office) 206 543-5041 (Fax) |