Today I finished my winter fieldwork. I must admit, I'm more than a little bit sad. For the last three years I've been studying alpine invertebrates that are active during the winter - beneath the snow. For me, it's the most fun and interesting part of my PhD work.
But let me backtrack a bit. Why am I interested in snow in the first place? Well, for starters, skiing is great fun! But, more seriously, snow has a really important role in sub-alpine and alpine ecosystems. It defines the length of the growing season and provides a source of water in spring and early summer. When I was up in the mountains today, there were millions (literally) of aphids, dead on the snow surface. Small insects get carried on wind currents, up to the tops of mountains where they are trapped on the snow. They promptly die, providing a "feast for crows" and other birds that migrate up into the mountains in the spring. Snow in Australia is fairly unreliable though. The year that I started this project, the snowpack on Mt Stirling completely melted out twice over the course of the winter. The depth and duration of snow is predicted to decline considerably in the coming decades.
When snow falls, it gets held up by vegetation, which creates a small gap between the base of the snow and the surface of the ground. In this space, the temperature is just above zero right through the winter. Why? Snow is a really amazing insulator. This means that while we might be freezing standing above the snow or, alternatively, wandering around in shorts and a t-shirt (like many of the people up on the mountain in the last couple of weeks), animals that live beneath the snow get a nice constant temperature all through the winter. But, to be able to make use of this, animals need to be able to function at temperatures near zero.
In Australia, we know very very little about the invertebrates that stay active during the winter, using the space beneath the snow. We also have no idea how they will respond if the snow cover changes. This is where my project fits in. This year, I've been working at Mt Stirling, in Victoria. I have 16 sites set up near the top of the mountain and I've been keeping snow off half of these (by shovelling) throughout the winter. A typical trip goes something like this: drive to the mountain, try and sneak a ride up the mountain with the ski patrol, ski/snowshoe/hike up the mountain when/if that last step fails, shovel snow, check traps, ski down the mountain, drive home. Out of curiosity, I did a little tally: ~60 m^3 of snow shovelled throughout the winter, which adds up to something around 18,000 kg. I'm pretty happy with that effort :D
It's been really interesting to see what's out there, under the snow. I found 18 major taxonomic groups represented, and springtails, mites, beetles and spiders make up about 90% of everything that I catch. Other cool things include pseudoscorpions, copepods, aphid, flies and tiny native wasps. And...no ants!! Anybody who's hiked up in the Australian mountains in summer knows how horrendous the ants can be...well, if you happen to be hanging out under the snow in winter, you don't have to worry about them.
So far, it seems that the inverts at Mt Stirling don't respond much to changes in snow cover. This is pretty different to what I found last year when I did the experiment near Mt Kosciuszko. Different years? Different locations? It's too early to tell...more years are needed! One thing that was really clear though, was that the inverts from the two locations are very different. So, perhaps it's not all that surprising that they respond differently to environmental changes.
With the final winter collection today, the skis have been taken out of the car, the snow shovels have been packed away and my little car is going to take a well-earned 1-week rest. The job for tomorrow is to see what's in the traps I just picked up and then...analyse the data! The great thing about this project is that I have no idea what I will find - and everything that I find is new and exciting!