While
we see fire as a destructive force, fire is a necessary part of many
environments and ecosystems. Fire often drives plant diversity, is responsible
for the germination of plant seeds, clears away debris, and puts nutrients and
minerals back into the soil. As such, understanding the role of fire
disturbance in natural landscape dynamics is essential for park and land
management. Fire dynamics, however, are not completely understood (Bergeron et al. 2002.) Moreover, the effect of
prescribed burns varies according to a variety of factors.
Kennard
and Gholz (2001) investigated the effect of fire intensity on soil quality and
nutrient availability in a Bolivian forest. Their study aimed to test the
difference between high and low intensity fires, as determined by “fuel loads”
or the amount of woody debris present, in terms of: 1.) how they affected the
soil itself and 2.) how it affected the growth of a particular plant, Anadenathera colubrine. They conducted
their burns in plots and looked at soil pH, organic matter concentrations, and
mineral concentrations (such as phosphorus, nitrogen, and magnesium).
The
study found that high intensity fires led to significantly higher mineral
concentrations that the other treatments, but they led to a significantly lower
concentration of organic matter in the soil. The amount of organic matter in
the soil affects how well soil accepts and holds water. Less soil organic
matter suggests that the soil is now worse at accepting and retaining water,
and also can lead to greater water evaporation from soil and surface run-off.
Meanwhile, while the low-intensity burns also led to higher mineral
concentrations than the control plots, they did not decrease soil organic
matter. As for the effect of burn intensity on the growth of A. colubrine, the seedlings grew the
tallest after high intensity burns; however, as Kennard and Gholz (2001) note,
the effects of the high intensity burns may not last in the long term. The soil
structure will takes years to recover after these high intensity burns, so the
researchers conclude that the low intensity burns may be the safer, more
beneficial route.
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While
experiments and research into the effect of burn intensity are rare, they may
be incredibly useful to consider when developing fire regimes. A burn intensity
experiment is on-going in South Africa’s Kruger National Park, where large
patches of the landscape have been burned twice at high or low intensities,
this time determined by the time of year and season, over the span of five
years. These experimental burns were ultimately conducted to inform future fire
regimes in the savannas of KNP, fire driven systems. For my proposed research,
I am interested in looking at how plant diversity, specifically growth under
large trees, differs between the high and low intensity burn sites. Kruger
National Park’s experimental burns also have to address the issue a declining
population of large trees due to an increasing population of elephants. This
research will help explore fire – herbivory interactions, and which type of
fire may be more beneficial in promoting greater plant diversity. Moreover, it
has the added conservation impact, as developing fire regimes that will cause
the least damage to already vulnerable large trees is in the best interest of
the savanna ecosystem. The Kennard and Gholz (2001) study is a useful study to
consider because it looks at the biogeochemical aspects of prescribed fire
intensity. Similar to their predictions and conclusions, I believe that the low
intensity burns will ultimately yield the most diversity while also being the
least damaging.
Works Cited
Kennard, D. K., and H. L. Gholz. 2001. Effects of high- and
low-intensity fires on soil properties and plant growth in a Bolivian dry
forest. Plant and Soil 234: 119 –
129.
Bergeron, Y., A. Leduc, B. D. Harvey, and S. Gauthier.
2002.Natural Fire Regime: A guide for sustainable of the Canadian boreal
forest.
You said that you wanted to study plant diversity responses to high and low intensity burns. Will you be looking at a few species found under large tree growth or will you be looking at ALL the plant diversity found?
ReplyDeleteHow will looking at the diversity of the growth under large trees tell you about what will cause the least damage to large trees? Do the trees and the growth under trees have a mutualism relationship type? Is there something else that you are measuring to assess damage on large trees?
ReplyDelete