Plant limitations and Growth, Where are all the plants? Options

[John_Sode]

July 25, 2005

Another question we are trying to answer involves plant growth and development. Why are plants found only in the stripes? Why are there vast areas without vegetation? Why are plants the size they are? We know that vast temperature differences can exist within a few inches of the ground surface, but are other factors involved?

We are also interested in microbial activity since microbes decompose (breakdown) organic material to enrich the soil. Also, this activity requires energy so the microbes are undergoing respiration. This means that they are releasing carbon dioxide into the atmosphere or soil. We are attempting to collect information both photosynthesis, which removes carbon dioxide from the atmosphere, and respiration. One of the challenges of conducting research in the Arctic is protecting the instruments used to gather measurements and data.



This experiment is measuring the effect of phosphorous and nitrogen on plant growth. Phosphorous and nitrogen are two major ingredients of fertilizer. These substances have been found to be limiting agents in many plant systems—the amount of nitrogen or phosphorous present determines the rate, and amount, of growth. Too much of either and the system, especially aquatic systems, might choke to death. Too little of either and the system struggles to survive.

In the Arctic, phosphorous is often bound (chemically combined) with the abundant calcium to form calcium phosphate. In this form it is not readily available to plants. Nitrogen, although present in the atmosphere, does not have a means to enter the biological systems and so it, to, is often not available to plants. Remember how the dovekeys, through their droppings, eliminated this problem in the Green Valley and the dramatic effect on plant growth that occurred?

In this experiment various levels of nitrogen, phosphorous, or nitrogen and phosphorous are being added to random patches of vegetation to observe the effects of these minerals on plant growth. The results are dramatic. In the second growing season following fertilization there is abundant growth in terms of vegetative cover, plant size, and even species distribution (what plants are growing in the plot). Does this mean that nutrients may be as much as, or even more important than temperature in determining plant growth? Does temperature affect different aspects of plant growth, such as size, than nitrogen and phosphorous levels?