This is a cross-post from my Soil Microbiology class blog, which you can find here. I edited the version here to be slightly less sciencey, but read the original if you want the deets of my research.
One of my current research sites lies at the southern end of the Klamath Mountains. It’s a super cool system – the bedrock is a mica schist that’s just chock full of N and the soil is pretty minimally developed. When you dig a pit, it basically looks like a hole full of tiny rocks (lots of big rocks as well) and barely any of what we think of as soil. Outcrops of exposed bedrock litter the forest floor. And yet the Douglas firs and white firs that dominate the forest are absolutely huge. In some spots, there are large trees that are straight up growing on rocks. Looking at that forest leaves no doubt in my mind that, like phosphorus, ecosystem-available N can definitely be derived from the bedrock – you can almost see it just by looking at it. It’s totally wild.
Last week I took a trip out along with another graduate student in my lab, Scott. We planned to collect soil and mica schist bedrock for a greenhouse experiment, survey a nearby peak for geology and vegetation, plus I wanted to pick up some soil and leaf litter samples for N fixation assays and microbial community characterization. Neither of us had actually been out to the site before, but we had topo maps, multiple GPS units, and anecdotal descriptions of the site, so we felt confident about our ability to drive in, get to work, and be able to leave by dark.
After stopping to get coffee (the most important ingredient of any field trip), we headed out of Davis at 6:30 am. It’s just under four hours to the mountain, and by a little bit after 10 we turned off Highway 36 onto a tiny forest road in the Shasta-Trinity National Forest. After driving a quarter of a mile into the forest, we became suspicious that we should have made a turn onto a dirt road a little ways back. Everyone had described how crazy the road in was, and the road we were on now seemed tame (and paved!). So, we turned around and then turned left onto a narrow, muddy road going up a ridge that looked much more wild. So wild, in fact, that I took one look at the steep, deeply rutted incline ahead of me, declared that I was no longer driving, and switched places with Scott.
About halfway up, after lots of reversing, re-angling, and tricky maneuvering over mounds and ruts, we were trapped on a mound that our SUV just could not seem to make it over. We stopped the car, put the parking brake on, and got out to assess the situation and figure out a better route. We didn’t realize that this was a huge mistake until we got back in the car, and it wouldn’t come out of park. Yikes. After some discussion (and heavy Googling), we came up with several tactics to try and get moving. The transmission didn’t seem to be burned out, but we were definitely stuck. I tried to shift gears while Scott tried to push the car up the hill to take some of the pressure off of the brakes. We tried to manually override the brake lock (? Clearly I know nothing about cars, which did not help the situation). Nothing worked.
Thinking that our car was a lost cause and we were going to need to somehow get someone to winch us off the hill, we decided to hike away from the car and get some samples. We reasoned that it would take several hours for anyone to be able to get to us, and there wasn’t cell service in the spot that we were stuck at, so we might as well start walking, make a call for help when we could, and in the meantime collect as much soil and rock as we could walk around with. It was only a mile to where we wanted to start sampling – not a bad distance at all.
Our sampling went smoothly once we made it out, but we were probably not as representative of the forest as we originally wanted to be since we had to hike between all of our sampling points. This wasn’t a huge deal, since the soil was for a greenhouse experiment, but it still felt weird to know that there was a better way to sample and to not do it. We had originally intended on sampling a two-mile stretch of forest, which quickly became more like a half-mile stretch. By the end of the afternoon, I was carrying about sixty pounds of rock on my back. There was a barren area 14 miles down the road that we had originally planned on getting most of our bedrock from, but since we obviously could not make that hike before dark, we spent a lot of time wandering around the forest in search of rock outcrops. We did not make it to the other peak we had wanted to survey.
What this all comes back to is a simple reality that we seem to forget, or not know about in the first place: field sampling is hard. You can make all the plans you want about the best way to sample an ecosystem and argue about soil depths, but sometimes we are limited by how much soil we can carry on our person, and how far we are willing to hike with that. Cars break down and get stuck. Several years ago at the same site, an assistant went into anaphylactic shock and had to be carried out of the forest. At my last job, my colleague was charged by a bear while doing field work. These things happen when you work in natural systems and are part of our job as scientists.
This is absolutely not an excuse to do shoddy science, though. Within our shrunken down sampling area, Scott and I worked hard to make sure we were sampling soils under representative trees, not taking from unusually steep hills, and putting enough distance in between soil pits. But all of these efforts were carried out within the constraints imposed by our situation. I think sometimes we are critical about sampling methods because we think that sampling in any less than the perfect way will prevent us from being absolutely certain about our conclusions. I agree with this to an extent; at the same time, when I walk out into a forest, I am immediately struck with how impossible it is to be “absolutely certain” about anything. In many ways, field based science is just fancy guesswork. Yes, we are better at guessing than most, but we are dealing with complicated, messy systems that we are mostly blind about. I think there’s something really beautiful in recognizing that we are not knowers of the truth, but rather explorers of a magnificent and intricate world. We do our best to be as rigorous as possible, but an ecosystem is not a laboratory, and it is impossible to have perfectly controlled conditions. We are grabbing for nuggets of truth in the darkness, and the best we can hope for is to be more strategic, but we can never just turn the lights on. This is a challenging affair that requires constant readjustment, thinking on our feet, and constantly wondering how we can best interrogate an ecosystem. I think we sometimes undervalue this challenge, but it is significant.
In the end, some maintenance guys from the gas company drove by in a truck and saw us walking down the road with our packs full of soil and rock. They kindly offered to drag our SUV down the hill, totally unfazed that some random soil scientists were hanging around on their maintenance road. The car literally needed to be moved five inches backwards before it would get going. So much for a sticky situation.