Deer are Important to Forests
When most people think about deer, it could be about the cute animal in the movie Bambi, a prized possession for a gamesman, or something to look out for while driving near wooded areas. Whatever the case, this animal generally does not strike people as having a large impact on the forest, its normal habitat.
Well, this can now be added to the repertoire of people’s thoughts on this hoofed mammal. Deer have now been documented to bring about a positive affect on the forest’s plant species. In fact, there is data to provide a hard-to-argue correlation of species richness increasing with a larger number of deer present in a specific area of the woods. Norwegian scientists have shown this correlation through a designed study that took place over a ten-year period.
(Stel, Jeroen. Red Deer. 2011. Jeroen Stel. Photograph. Sept 24, 2013.)
When deer consume a large quantity of the woody species around them, they tend to help the plants by dispersing their seeds and allowing the plant to diversify – especially lower growing species of plants. However, if the deer decide to not eat a certain type of species of plant, it could face being displaced as being the dominant species in that area, which could cause that plant’s diversity and dispersal to fall.
To understand this relationship, the scientists decided to test one specific location of forest and one type of plant to best model the behavior of all plants in that area. Bilberry, which to most could be easily confused with blueberries, provide the researchers to observe a low to the ground growing plant that is commonly eaten by deer in a large part of the year. Because of its popularity in taste for the deer, it is easy to track for data collection.
In seven different areas around the forest, one-by-one meter plots were set down on the ground next to an even larger permanent macroplot, which closely resembles a wire cage. Despite its frightening appearance, apparently it does not affect the deer’s eating patterns as they go right up to it to forage. These plots provide evidence of the number of different plant species, which the scientists then classify into groups.
From 2001-2011, 3 equally spaced out samples were taken from these plots to see what exactly the deer were allowing to grow where they eat. Based on the amount of bilberry consumed in each location, a scaled number was attributed to each site to signify how much grazing had taken place.
The Norwegians decided to use a theory called the intermediate disturbance hypothesis, which is fancy jargon for stating that there is a relationship formed when the level of disturbance is at an intermediate level. At this intermediate level of disturbance there will be the highest level of species found. As it turns out, this theory provided a good basis for the experiment as it nearly perfectly described their findings.
Hegland, Lilleeng, and Moe found that the low-growing species in the woods had a clear advantage in its ability to have more species richness than compared to the higher growing species. Furthermore, increasing the amount of deer present in the area to forage only further helped to diversify and spread the lower growing species. Unfortunately, for the higher growing species, the increase in deer had little benefit for their species.
The increase in number of deer (to a certain level), like the researchers predicted, brought along an increase in the total species richness with a large increase in species richness of low-growing plant species. When the number of deer present became artificially excessive, which was the case on breeding farm, it was found that there was a decrease in species richness – excluding itself from the normal trend.
Ultimately, the take home message is that when deer are present in a large quantity in any certain forest area, expect the lower growing species to have an advantage over the higher growing plants. This does beg the question, if hunting deer were discontinued, would this provide the most elaborate low-growing species to disperse in the woods? Perhaps, it s a bit overkill, not to mention it is never going to happen; but it does provide an interesting imaginative scenario. It could possibly reshape the way the ground level of forests look with different species of plants.
Hegland, S., Lilleeng, M., & Moe, S. (2013). Old-growth forest floor richness increases with red deer herbivory intensity. Forest Ecology and Management, 310(15 Dec), 267-274. Retrieved from http://www.sciencedirect.com/science/article/pii/S0378112713005586