In July, I drove myself and a field technician to the Canyonlands Research Center where we stayed for one week as we worked to collect soil samples in Canyonlands National Park under a permit. Our task was to collect 5 samples from 60 plots of biocrust which would be used to measure the amount of biocrust that has grown back over the past two-years, naturally!
I was surprised by the amount of growth in these plots and at how long it took to properly label 300 bags (while not letting blow away in the wind). The work involved finding each plot (marked by flags on metal sticks that no longer have the flags attached), taking photos, laying out transects, taking soil samples, measuring soil stability at each location, and visually estimating growth. The goal is to measure recovery, which means we need some measure of biocrust growth. You might guess that we would use genetic tools to see how many bacterial genes are present in the soil. That would be an option, but is a little too intensive (expensive) for the question that we are asking. Instead, we simply extract all the chlorohyll a from the soil and measure its concentration (in 1 g of sample). This lets us measure how many photosynthetic microbes are in the soil at each location. Why are there photosynthetic microbes in the soil? Well, these deserts are extreme environments and are very challenging for vascular plants to grow. Instead, microbes (cyanobacteria) grow, which capture energy from the sun like a plant. This allows for other microbes to grow as well and boom - a microbial community forms. Another way to measure a biotic crust community growth is to see how much stuff they are producing. Biocrusts generally are held together by lots of sugars, produced by the cyanobacteria, which bind microbes and soil particles all together. One can extract these sugars and measure how much is in each gram of soil as well. A third way to measure growth is to visually estimate the growth of the biocrust over a certain area or the darkness of the soil surface which can relate to which microbes are present. This fall we will employ all of these tools to compare the growth in each plot. I'll follow up this work with tests to think about the dispersal method of the biocrust and the relative importance of wind, water, and lateral movement of the microbes into uncolonized areas. Analyzing the recovery process of natural biocrust communities will help us to improve restoration strategies in aridlands.
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AuthorSierra is a graduate student in the Barger Lab at CU Boulder studying microbial ecology for dryland restoration. Archives
August 2023
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