Butenolide. This is the chemical bond structure of the compound mentioned during our walk. It was an interesting little tidbit that native species for our area developed an interesting adaptation to natural wildfires that periodically swept across the Great Plains; their seed germination requires the application of fire, the smoke of which induces the production of butenolide. I think that fact speaks volumes about the concept presented to us through our tour of Lubbock Lake Landmark, namely that fire is a prolific and integral element to the survival of the Great Plains. It sounded weird to me hearing that, where I had previously been oriented towards grass fires as a generally negative occurrence. An interesting aside, wildfires occur on every continent but Antarctica!
Simultaneously, besides being a chemical mechanism for seed germination, fire plays an important role in managing the ecosystem. It allows for the continued growth of root systems by inhibiting the depletion of root systems from the overgrazing of livestock. This is a slow, season-by-season loss of root systems from animals consuming nutrients that are being compensated for by the root system itself. Fire also clears land of exotic plants and grasses within idled fields, allowing for the expansion of different, native plants, plants that are actually adapted to these grass fires. One way that this occurs is by removing and inhibiting the proliferation of mesquite, a water intensive plant that is considered one of the world's most problematic invasive species by the World Conservation Union.
Mesquite, while absorbing more natural resources than native grasses, also perform an important, productive role within the ecology as well, one that is not fully realized until it is removed (grass fires). Mesquite is leguminous plant (legume, e.g. beans, peas, lentils, soy, etc.) and as such has a symbiotic relationship with rhizobium, a soil bacteria, held within a legume's root system. This symbiotic relationship allows for the fixation of nitrogen, the important ecological function of removing nitrogen from the atmosphere and "fixing" it within the soil. Nitrogen is essential in the formation of amino and nucleic acids, which are used in proteins and DNA/RNA respectively.
Fixing nitrogen is itself a competitive advantage against non-nitrogen fixing plants such as grasses. Mesquite's quick acquisition of a landscape is influenced by the many factors that degrade or erode nitrogen fixed within the soil, many of which are the direct consequence of human activity. Ammonia votilization,
nitrogen changed into ammonia gas and returned to the atmosphere, occurring from the use of fertilizers that are composed of urea; denitrification of closed root-mycorrhizal systems due to high-temperatures from overexposure to the sun, a result of clearing trees or brush that provide shade; and loss of nitrogen from the overgrazing of animals or repeated agricultural harvesting of crops without allowing a field to fallow. With the combined loss of nitrogen in the soil from these sources and because nitrogen fixing legumes do not require nitrogen fixed within the soil to undergo amino and nucleic acid production, the rhizobium within their root systems produce nitrogen compounds in exchange for glucose from the legume, they are able to survive where grasses may not. However, when mesquite die, perhaps a death by wildfire, they release all the nitrogen in their root systems into the soil, replenishing depleted nitrogen and allowing for the return of grasses.
The fixation of nitrogen is doubly important to farmers and the ecology in this: farmers are not required to fertilize their crops as frequently, which saves on overhead, by using legumes as a means of returning depleted nitrogen back into fallow fields. The ecology benefits in avoiding being inundated with fertilizers which can be washed into rivers and tributaries, another important ecological niche.
Anyways, I thought that I would put up a before and after of the Netleaf Hackberry, a surprisingly beautiful tree.
