Experimentally Simulating Climate Change Effects on Trophic Interactions in Montane Meadow Systems
Diane Debinski1, Matthew Germino2 and Jill Sherwood3
1Department of Ecology, Montana State University, Bozeman, MT
2USGS Forest and Range Ecosystem Science Center, Boise Idaho
3Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa
Brief Description of Aims
Increasing evidence predicts that global climatic patterns are changing rapidly as a result of anthropogenic production of greenhouse gases, including CO2. Montane systems are some of the regions of the globe that may be most sensitive to climate change. Montane meadows are especially diverse and productive with respect to their plant communities and as such they are important food sources for a diversity of herbivores, including insects to large mammals. Temperature increases associated with climate change will likely lead to a decrease in the duration of snow cover in montane meadows and this change could have a significant effect on the ecology of the systems. Ecological effects could include advancement of spring events, shifts in species distribution patterns, and phenological changes (timing of life-history patterns such as emergence, maturity, or reproduction). Reproductive asynchrony, a phenological condition where males and females mature at different times and have a reduced opportunity to find each other and mate, is another potential effect of climate change. Observational studies of climate change responses under field conditions can require decades of research. However, experimental field manipulations can provide a window of understanding into how larger-scale climate change effects may become manifested.
The objectives of this research are to experimentally simulate predicted warmer temperatures and earlier snowmelt in a high elevation montane meadow ecosystem and to assess changes in:
- soil temperature and moisture
- timing of plant emergence, flowering, and senescence
- developmental and reproductive responses of a butterfly species, Parnassius clodius, which is dependent upon the plants in this meadow for host plants (Dicentra uniflora) and nectar sources (Eriogonium umbellatum).
Experimental sites: Twelve experimental plots were established in 2010 (3 of each of four treatments). An additional twelve plots were added in 2011
The study area for this research is a sagebrush (Artemisia sp.) meadow at an elevation of 2100 m (7000 ft) and relatively homogeneous topography located in Grand Teton National Park, WY. We established a replicated block design of snow removal and passive heating plots to examine the effects of temperature, snow removal and their potential interactions. This area has a relatively low average annual precipitation of 53 cm/yr, which comes mostly as snow. Given that spring snowpack is about 50% water by volume, removing 50 cm of the snowpack (i.e., all snow still present in early May) can reduce the annual precipitation by half. We are examining how these changes affect the phenology of Clodius Parnassian butterflies (Parnassius clodius), their host plant, Steer's head (Dicentra uniflora), and their nectar sulphur-flower Buckwheat (Eriogonum umbellatum) in the Greater Yellowstone Ecosystem. This butterfly species is relatively common in Grand Teton National Park, but several related species of Parnassiusin Europe have shown significant declines over the past few decades. Parnassius species are one of the few insect species that are easily identified in the field as having been mated. Thus, they can be used as an indicator of how climate changes may be affecting reproductive asynchrony in insect populations.
The Clodious Parnassian butterfly (photo by D. Debinki)
In 2010, we established a replicated block design of snow removal (SR) and passive heating (H+), both treatments (SR and H+) and a control (CT) to examine the effects of temperature, snow removal and their potential interactions. The snow removal treatment is a simulation of earlier snowmelt and the warming treatment is a simulation of warming soil conditions. Both of these treatments could be observed as a result of climate change in this region. Three replicates of each treatment were established in 8 x 8 ft plots. Soil temperature and moisture (at 5 and 25 cm depths), air temperature, and plant physiological data were analyzed across the growing season to determine the effects of the treatments. Volumetric water content of several species of plants was assessed in the middle of the growing season to determine whether snow removal had an effect on plant water content. Physical parameters, such as growth and timing of maturity of P. clodius larvae, E. umbellatum, and D. uniflora as well as timing of adult butterfly emergence were measured.
Snow removal + warming treatment (SR and H+) showing open-sided warming chamber in foreground, control plot in background. An average of 68 cm of snow was removed from snow removal sites in 2011.
We expect that snow removal will decrease the available soil moisture throughout most of the growing season, resulting in decreased water potential for the plants in the snow removal treatments. We expect that the passive heating will increase nighttime temperatures above the unheated plots, which will advance flowering and senescence dates for plants. The combination of snow removal and warming may compound effects on these phenological responses. Because insects are highly sensitive to variables such temperature and moisture, we expect that they will show quick responses to changes in climate, and that these responses can be easily measured in terms of emergence time, growth, and reproductive parameters. We predict that altering the timing of snowmelt will advance D. uniflora host plant emergence and senescence, resulting in decreased larval growth and increased larval mortality in Parnassius butterflies. This site is part of a larger network of warming devices arrayed along the snake river plain, into Wyoming Sagebrush and Cheatgrass communities which will allow for comparison of responses among responses among different sagebrush communities. The results will also be valuable for understanding potential climate-related trophic impacts in other ecological systems.
References of interest
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Sherwood, J.A., D.M. Debinski, P.C. Caragea, and M. Germino. 2017. Effects of experimentally reduced snowpack and passive warming on montane meadow plant phenology and floral resources. Ecosphere. Volume 8(3) Article e01745. doi.org/10.1002/ecs2.1745
Szcodronski, K. E., D.M. Debinski and R. Klaver. 2018. Occupancy modeling of Parnassius clodius butterfly populations in Grand Teton National Park, Wyoming. Journal of Insect Conservation. doi: 10.1007/s10841-018-0060-1