Here is an update from our Postdoc Dr. Eugenia Bragina:
What’s new, you are asking? Everything was new for me this summer – I just started my postdoc with Scott Mills. A goal of my project is to look for the balance between endangered and game species in long-leaf pine ecosystems. It turns out, game management and endangered species management have conflicting interests sometimes.
Couple of centuries ago, long-leaf pine ecosystems were covering most of Southeastern US. Now, just 2-3% left, and those fragmented areas require careful management. In pre-settlement time, wild fires used to happen very often starting from lightnings. There was no roads or settlements at this time, and a fire, which started in Florida, could get to North Carolina not being stopped. Now, management is trying to imitate nature, doing prescribed burning every 2-5 years. Prescribed burning removes hardwood and leaves a pine forest opened. One of the species we protect in the long-leaf pine ecosystems is endangered red-cockaded woodpecker. Woodpeckers make their nest holes in the pine trees. If hardwood is too dense, they simply abandon their nesting holes. So, it’s really important to keep hardwood understory scarce. At the same time, no hardwood at all makes the forest hardly suitable for other species. For example, white-tailed deer need hardwood trees for cover and mast crop for food.
So, the question is, how much hardwood should we keep in a pine forest. In other words, how much hardwood can red-cockaded woodpecker tolerate so we can leave an understory for deer and other game species? To answer this question, we decided to develop several ‘what if’ scenarios. What if we keep 30% of hardwood? Or, for example, 70%? How many woodpeckers, Saint Francis’ satyr, deer, and turkeys are we going to have?
At the first place, I was going to use matrix population modeling to answer these questions. An idea is simple. If we know how exactly a management action affecting a survival or fecundity, we can calculate population growth rate lambda in the presence of this action. For example, let’s assume that fecundity of red-cockaded woodpecker is 20% higher on the burnt areas than on non-burnt ones. We can calculate how much population growth rate is increasing every year, and forecast a number of woodpeckers in, say, 50 years.
Well, the idea of using vital rate difference is a good one, but it requires a lot of data: we need to know survival before and burning, or on burnt and not-burnt areas. I did thorough literature search, but did not find too much information of this kind. Surprisingly enough, nobody published on survival rates of white-tailed deer in long-leaf pine ecosystems before and after burning, or on burnt versus controlled plots.
I realized that I need to use slightly different approach. It looks like the best way to go would be to combine both habitat and population modeling. In this case, we can use hardwood amount as a proxy for habitat quality and relate it to population number. So, I am going to try it now and hopefully more news is coming soon. Stay tuned!