The Effects of Wind Exposure and Disturbance on the Insulative Value of the Subnivean Space

1. Genesis Machek Winter Ecology, Spring 2010 Mountain Research Station - University of Colorado at Boulder The Effects of Wind Exposure and Disturbance on the Insulative Value of the Subnivean Space

2. Background Information • The subnivean environment – the space under the snow • Affects of small boulders and other obstructions under the snow – creating a larger subnivean space (Sanecki et al., 2006) • Wind exposure • Less interaction with environment above the snow (Taylor and Buskirk, 1996) • Implications for ability to get food • Disturbance with snow-related recreation • Causes compaction, increases density, decreases height of subnivean space (Sanecki et al., 2006; Whiteman, 2008)

3. Introduction • Question: How does wind exposure affect the insulative value of the snowpack and perhaps the viability of animals living in the subnivean environment? • Question: How does disturbance effect how insulative the snow pack is in exposed and not exposed environments? • Hypotheses: The snow pack will be more insulative in less exposed environments; however, disturbance of the snowpack will have a greater, negative effect on the insulative ability of the snow pack in less exposed environments.

4. Methods and Materials • 4 sites were chosen • 2 sites sheltered from wind exposure • 1 at 55 cm, 1 at 65 cm • 2 sites with wind exposure • 1 at 55 cm, 1 at 65 cm • 65 cm sites were visited twice over one week to see the effects of recent disturbance of the snowpack • Density and Temperature were taken at each site

5. Methods and Materials • The temperature gradient was measured – qualitatively assessing the significance of the calculated insulative value • Insulative Value was measured • Marchand’s equation to test the insulative value: • Where d = density (g/cm3), t= thickness (cm), i = layer, and TI = insulative value

6. Results

7. The insulative value of the exposed sites were consistently higher than the sheltered sites Insulative Value Data

8. The densities near the ground are all similar The sheltered areas have higher densities, while the exposed areas have lower densities Density Profiles

9. General increase in insulative value Greater increase in insulative value at the sheltered site vs. the exposed site Insulative Value Data

10. There is a large difference between the Sheltered site for week one and two The exposed site is very similar between weeks one and two Density Profiles

11. Discussion • The snowpack seems to have a greater insulative value in exposed areas, this would suggest that animals would be in a more stable environment in exposed environments. • Objections? Increase in convection due to wind exposure (Taylor and Buskirk, 1996) • Temperature gradient values disagree with these findings • The density profiles show that the density is lower at the sites where the insulative value is higher • Why? Exposure?

12. Discussion • Temperature Gradient values suggest that the sheltered sites were more insulative • Might suggest that more animals would prefer more protected sites to create their tunnels (Sanecki et al., 2006) • This might also be a suggestion of the benefits of staying in protected areas to hide from predators or to be closer to trees and thus a food source.

13. Discussion • Reversal in the trend from week 1 to week 2, which suggests that disturbance could have a greater effect on sheltered environments • less fresh snowfall in the sheltered area, causing this area to be more exposed to wind and temperature differences • More research might be done on the effects of disturbance due to snow-related recreation in different environments to see if sheltered areas are more sensitive than wind exposed areas

14. Main Points - Outline • The insulative value of the snowpack – sheltered vs. exposed and disturbed vs. un-disturbed • Insulative value: • higher in exposed areas before disturbance, higher in the sheltered area after disturbance • Effects of density • Temperature Gradient Snow • Disturbance • effects of wind exposure • Recent snowfall in site with wind exposure • higher density, more insulative snow • Future Research • Effects of snow-related recreation on sheltered vs. exposed sites • Questions??

15. References • Auerbach, N., & Halfpenny, J. (1991). Snowpack and the subnivean environment for different aspects of an open meadow in jackson hole, wyoming, USA. Arctic and Alpine Research, 23(1), 41-44. • Marchand, PJ. (1982). An index for evaluating the temperature stability of a subnivean environment. The Journal of Wildlife Management, 46(2): 518-520. • Sanecki, GM; Cowling, A; Green, K; Wood, H & Lindenmayer D. (2006). Winter distribution in relation to snow cover in the subalpine zone, Australia. Journal of Zoology 289, 99-110. • Sanecki, GM; Green, K; Wood, H & Lindenmayer, D. (2006). The implications of snow-based recreation for small mammals in the subnivean space in south-east Australia. Biological Conservation 129, 511-518. • Taylor, SL & Buskirk, SW. (1996). Dynamics of subnivean temperature and wind speed in subalpine forests of the rocky mountains. Journal of Thermodynamic Biology 21(2), 91-99. • Whiteman, J. P. (2008). Impacts of snow compaction from human recreation on the biota of snowy regions

16. AppendixTemperature Gradient Graphs

17. The trendlines show that the temperature gradients are very similar to each other. In the exposed environment the ground is colder than the snow above (ground was frozen) The sheltered environment was more insulative based on this data Week 1 Data

18. The sheltered environment is still the better insulator based on this data as well Week 1 Data

19. The exposed environment had a more consistent temperature gradient At the sheltered site the temperature gradient was not consistent and the ground was frozen According to this data, after disturbance, the exposed site was a better insulator than the sheltered site Week 2 Data