ESA Symposium, Portland 2004

Functional Significance of Mountain Biodiversity

Tuesday, August 3, 1:30 to 5 pm, Oregon Ballroom 204

Sponsors

Physiological Ecology Section and Global Mountain Biodiversity Assessment

Principal Organizer

Bill Bowman, Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, bowman@spot.colorado.edu

Description

The symposium will bring together scientists working in a variety of ecological disciplines to present their research linking the role of biodiversity to the functioning of mountain ecosystems. The symposium is part of a series of thematic workshops supported by the Global Mountain Biodiversity Assessment, a program within DIVERSITAS and GCTE. The goal of the workshop is to provide a framework to better understand the role of biotic factors controlling ecosystem processes in climatically severe mountain environments.

The role of biodiversity in ecosystem function continues to be debated, although the role of individual species or functional groups is well established. Mountain ecosystems are particularly important to this debate for several reasons. Mountains contain high levels of biodiversity relative to surrounding lowlands, due in part to higher climatic and edaphic heterogeneity. Mountains are also highly susceptible to direct (e.g. land use intensification) and indirect (e.g. climate change, atmospheric deposition) environmental impacts from human activities. The role of biodiversity in buffering these changes, or in reinforcing the changes (e.g. positive feedbacks to nitrogen deposition) have been suggested. The symposium will focus on the role of biodiversity as a response variable to environmental change, as well as a factor determining the system's response. The focus will be primarily on species diversity influences on ecosystem function.

The mountain theme is also appropriate as it relates to the overarching theme of the ESA meeting: the journey of Lewis and Clark and their discoveries of the wealth of biodiversity in mountain ecosystems.

Schedule of speakers

Tuesday, August 3, 1:30 PM to 5:00 PM, Oregon Ballroom 204.

1:30 PM Introduction: W. Bowman and Ch. Körner.

1:35 PM Seasonal dynamics of soil organisms: Implications for understanding the functioning of alpine systems
Steven Schmidt, Allen Meyer, Chris Schadt, David Lipson, David Oline, Diana Nemergut, Andrew Martin, Elizabeth Costello.

2:00 PM Linkages between aboveground and belowground biodiversity in mountain ecosystems
Richard Bardgett.

2:25 PM Ecosystem effects of biodiversity manipulations in European grasslands
Eva Spehn, Andy Hector, Jasmin Joshi, Michael Scherer-Lorenzen, Bernhard Schmid.

2:50 PM Break.

3:05 PM Plant diversity and alpine slope stability
Christian Körner.

3:30 PM Mechanisms influencing alpine plant diversity and the control on ecosystem function
William Bowman.

3:55 PM Effects of a climate-induced shift in plant community composition on ecosystem processes in a subalpine meadow
Molly Smith, John Harte.

4:20 PM Glacier forelands as a model for high alpine colonization and community assembly
Rüdiger Kaufmann, Brigitta Erschbamer, Leopold Füreder, Martin Kirchmair.

4:45 PM Conclusions: W. Bowman and Ch. Körner.

Full Abstracts

Seasonal dynamics of soil organisms: Implications for understanding the functioning of alpine systems.
Steven Schmidt1, Allen Meyer1, Chris Schadt2, David Lipson3, David Oline4, Diana Nemergut1, Andrew Martin1, Elizabeth Costello1
1 University of Colorado, Boulder, 2 Oak Ridge National Lab, Oak Ridge, Tennessee, 3 San Diego State University, San Diego, California, 4 Southern Oregon University, Medford
I will present our recent efforts to construct a complete library of rRNA sequences for all below-ground life in a tundra (Kobresia myosuroides) meadow in Colorado. To our knowledge this is the most intensive effort to date to catalogue all soil organisms in one site using molecular techniques. In order not to bias our work towards any one group, we used separate primer sets for the three domains of life: Bacteria, Archaea and Eucarya. In addition we sampled during the three most dynamic periods for microbial activity in alpine systems (under snow, snow melt and summer). Our results demonstrate a staggering diversity of microbial life in these soils. Many of our sequences represent deeply-divergent microbial lineages that have not been previously described. For example, we found 3 new fungal groups that are divergent at the subphylum or class level. We also found that the diversity of microbes changed dramatically on a seasonal basis. Most surprising was our discovery of a large and deeply-divergent group of Ascomycetes that is only detected under the snow or during snow melt. The implications of these seasonal shifts in diversity will be discussed.
 
Linkages between aboveground and belowground biodiversity in mountain ecosystems.
Richard Bardgett
Institute of Environmental and Natural Sciences, Lancaster, Lancashire, United Kingdom
It is becoming increasingly recognised that feedbacks between the producer and decomposer subsystems operate as a major driver of ecosystem functioning. In this talk, I will discuss recent advances in our understanding of the functional importance and nature of links between these two subsystems in mountain ecosystems, and of the potential roles of plant and soil diversity in their operation. The importance of these feedbacks will be illustrated using selected examples from studies done in mountain regions of the United Kingdom, especially in grassland and regenerating woodland of the Scottish Highlands. First, I will illustrate the general importance of soil organisms and their interactions as regulators of plant nutrient supply and nutrient retention in high mountain ecosystems. Specifically, I will show how soil microbes act as major sinks for nutrients in these nutrient limited ecosystems and how partitioning of nutrients between the plant and microbial pool varies temporally. I will then consider how variations in the diversity and composition of the plant community might impact on these processes of nutrient cycling, and how variations in the diversity of microbial-feeding soil animals might influence plant nutrient supply through their impact on soil microbes. Finally, the importance for nutrient cycling of these aboveground-belowground linkages will be considered in the context of other components of mountain ecosystems, namely large mammalian herbivores.
 
Ecosystem effects of biodiversity manipulations in European grasslands.
Eva Spehn1, Andy Hector2, Jasmin Joshi2, Michael Scherer-Lorenzen3, Bernhard Schmid 2
1 Institute of Botany, University of Basel, CH-4056 Basel, Switzerland, 2 Institute of Environmental Sciences, University of Zurich, CH-8057 Zurich, Switzerland, 3 Institute of Plant Sciences, CH-8092 Zürich, Switzerland
We present a multisite analysis of the relationship between plant diversity and ecosystem functioning within the European BIODEPTH network of plant diversity manipulation experiments. We report the responses of fifteen ecosystem process variables, measured across three years in plots of varying plant diversity at eight different European grassland fieldsites. All the aspects of diversity and composition we examined, both numbers and types of species, produced significant impacts on ecosystem processes. In general, communities with higher diversity were more productive and utilized resources more completely by intercepting more light, taking up more nitrogen and occupying more of the available space. Diversity had significant effects through both increased vegetation cover and more efficient nitrogen uptake when this resource was abundant through nitrogen fixed by legumes. However, additional diversity effects remained even after controlling for differences in vegetation cover and for the presence of legumes in communities. Diversity effects were stronger on above- than belowground processes. Ecosystem effects of plant diversity varied between sites, between years or with both. However, in general, diversity effects were lowest in the first year and stronger later in the experiment, indicating that they were not transitional or due to community establishment.
 
Plant diversity and alpine slope stability.
Christian Koerner
Institute of Botany, Basel, Switzerland
In steep terrain, slopes need engineering forces to stay in place and facilitate sustained ecosystem functioning. A closed plant cover, deep roots, strong rhizomes, and massive root stocks are the tools provided by nature to ensure the persistence of biota in steep alpine terrain. How much variability among plant taxa is needed to fulfill this function in an ever changing environment? How does human land use interfere with these functions? I will present case studies from the European Alps and the Central Caucasus to illustrate the significance of biodiversity and plant cover type for the integrity of alpine ecosystems. For instance, a dwarf shrub cover of >10 % reduces run-off substantially, and water infiltration rates become almost doubled in shrub-dominated plots. Since dwarf shrub cover above 40 % has been shown to increase erosion risk, the observed changes in run-off might explain the high frequency of land slides on abandoned pastures with shrub encroachment. Increasing cover by vascular plants significantly reduced surface run-off. Hence, both cover and plant functional types (biodiversity) affect the stability of steep alpine slopes. Land use can have positive and negative effects on erosion and hydrology, and there is no systematic difference between grazing and mowing with respect to the resultant species diversity in the lower alpine belt. References: Koerner C (2002) Mountain biodiversity, its causes and function: an overview. In: Koerner C, Spehn EM (eds) Mountain biodiversity, a global assessment. The Parthenon Publishing Group, Boca Raton, p 3-20 Koerner C (2003) Alpine plant life. Springer, Berlin, 2nd ed.
 
Mechanisms influencing alpine plant diversity and the control on ecosystem function.
William Bowman
University of Colorado, Boulder, Colorado
The alpine is characterized by high species density relative to other herbaceous communities, with a high turnover of species across the landscape. Microclimatic heterogeneity contributes significantly to patterns of diversity, yet biotic interactions also play a role in determining species presence and abundance. Facilitation, through climatic amelioration and N2-fixation, and competition have been suggested as significant factors determining species composition, despite the selective pressures for traits conferring tolerance of low resource availability and climatic stress. The high spatial variability in resource supply results in high functional diversity of alpine plants. This in turn results in the potential for directional changes in the environment (climate change, N deposition) to elicit large changes in ecosystem properties due to biotic feedbacks. In particular, rates of soil N cycling, and the interannual variability in production are sensitive to changes in plant functional types. Changes in functional diversity have the potential to exaggerate or buffer ecosystem responses to environmental change. This biotic control is particularly important in mountains where the diversity of plant functional types is high.
 
Effects of a climate-induced shift in plant community composition on ecosystem processes in a subalpine meadow.
Molly Smith, John Harte
University of California at Berkeley, Berkeley, CA
Human impacts on ecosystems have resulted in dramatic declines in plant diversity via activities such as habitat destruction, nitrogen deposition, and intentional or accidental exotic invasions. Future changes due to anthropogenic climate warming are expected to exacerbate the rate of diversity loss. Results from our on-going 13-year warming experiment in a subalpine meadow ecosystem in the Rocky Mountains of Colorado suggest that the productivity of deep-rooted forb species is either promoted or unaffected by warming, whereas shallow-rooted forbs respond with lower annual production and lower flowering success. Analysis of spatial patterns in these meadows suggests that plant species richness is reduced under conditions of early snowmelt or enhanced nitrogen availability. Because manipulated climate warming advances snowmelt, reduces soil moisture in surface soil layers, and increases nitrogen availability, the loss of shallow-rooted plant species from this subalpine meadow ecosystem can be anticipated under future warming. To examine the ecological consequences of this warming-induced change in plant community composition, we removed shallow-rooted forb species from otherwise intact subalpine meadow plots and monitored changes in plant productivity, ecosystem carbon storage, nitrogen cycling and ecosystem responses to nitrogen fertilization.
 
Glacier forelands as a model for high alpine colonization and community assembly.
Rüdiger Kaufmann, Brigitta Erschbamer, Leopold Füreder, Martin Kirchmair
University of Innsbruck, Innsbruck, Austria
Glacial retreat over the last 150 years in the European Alps has created chronosequences representing natural experiments on colonization and succession under high alpine conditions. The foreland of Rotmoos glacier in Austria is particularly well studied with respect to plant, animal, and fungal communities. In all organism groups species richness and abundance increase rapidly within 50 years of deglaciation with a high rate of species turnover. At this time, with plant cover around 50%, invertebrate surface activity (spiders and beetles) and soil fauna abundance (mesofauna, diptera) have attained levels similar to those of mature alpine grasslands nearby. Changes in diversity, abundance, and species composition slow down in later successional stages. Seed rain and seed bank indicate an additional species input by plant fragments from the surrounding slopes. Herbivores become abundant after 40 years and decomposers after 100 years in agreement with ecosystem development. Paradoxically, however, the initial communities are dominated by predators in the absence of a supporting local food web. Allochthonous input of windblown insects may be important, but presence of collembolans also indicates some local productivity. Quantitative data are still inconclusive, similar results from other colonizer communities are currently debated. In the early stages, faunal community changes observed over several years deviate from the trends deduced from the chronosequence pattern. Model calculations using long-term climate records showed that this discrepancy may be explained by a high sensitivity of initial colonization to climate fluctuations and the rate of glacial recession. Zoobenthos of the glacial stream follows a succession of a totally different kind governed by physico-chemical conditions favorable in winter but extremely harsh during glacial ablation in summer. Only a few specialized chironomids are able to cope with the silt load at the glacier front. Farther downstream spring fed tributaries improve conditions and serve as safe sites during summer.
 

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