By Dr. Ron Masters
Associate Professor of Forestry and Wildlife Specialist
(photos at bottom)
In forestry school, I was taught that care should be exercised in planting southern pines outside of their native range because of potential for ice storm damage. This was particularly the case for loblolly pine when compared to shortleaf or Virginia pine. As the story went, the shorter needles shed the ice better and had less surface area for ice to collect upon. As years passed, these teachings went by the way as the research and management literature began to emphasize short-rotation forestry and the much better growth and yield characteristics of loblolly along and north of its native range compared to the slower growing shortleaf pine. Across the south standard forest management recommendations became almost exclusively - short-rotation, even-aged, loblolly pine plantations. This was the wave of the future for both industrial and small private landowners.
The ice storm of December 1997 that hit parts of Oklahoma, Arkansas and east Texas brought me to briefly reconsider the issue of recommendations to convert native mixed pine-hardwood stands to loblolly plantations. I examined the ice damage on 2 research-demonstration areas, one Robbers Cave Forest-Wildlife Demonstration Area and the other on Pushmataha Forest Habitat Research Area in Latimer and Pushmataha counties respectively. Forestry and Wildlife Extension in the Department of Forestry at OSU monitors these areas as part of a joint project with Oklahoma Department of Wildlife Conservation and the Oklahoma Department of Agriculture-Forestry Services to examine various forest management strategies and their efficacy for private landowners with small landholdings.
To my surprise in summer 1998 when we were assessing damage on our research-demonstration areas, we found only slightly less damage to natural shortleaf versus planted shortleaf and planted loblolly (both 12-14 years old) with typically less than 10% of the trees showing significant damage. Naturally regenerated stands showed less damage than planted stands. Natural stands were more dense and also had lower height and diameters. We did have slightly greater damage in mature, native, shortleaf stands in the Pushmataha County area that had been thinned to a basal area of less than 70 square feet per acre. We ended up performing a salvage operation here and suffered no great loss. My thoughts were that maybe that the ice damage thing had been somewhat over-played back in my college days.
Then came the ice storm of December 2000! Reports from southeast Oklahoma and western Arkansas where we have projects were not good. I feared the worst for the research demonstration areas that I had established in 1982 and 1983. My first visit to these areas was in late January 2001. The first stop was Robbers Cave along with ODA Forester Mike Tooley. We were both sick. As we examined one plantation after the other the result was the same, greater than 80% of the trees, in one stand 88%, were broken or lodged such that the tree was a loss. We found no difference in planted loblolly or shortleaf (both planted in winter 1985). On our seed tree cut, we found significant damage but we were dealing with an overstocked stand to begin with.
When we walked into the selective cut shortleaf stand, we were astonished to find very little (less than 5%) of the trees had significant damage. Likewise in the control or unmanaged stand, the mature shortleaf showed little damage. Apparently the mature trees provided some protection for smaller trees in the midstory. The plantations will be salvaged as posts this summer and will be clearcut and replanted this next winter.
Next stop was the Pushmataha area. The ice storm had been less severe in this part of Pushmataha County. After summarizing plot data from 3 loblolly plantations planted in 1986, I found that average tree loss across the 3 stands ranged from 24-43% and averaged 33.1%. However, in naturally regenerated stands without fire (harvest cut was almost a clearcut) damage ranged from 4-17% and averaged 10.6% for all stands. Interestingly enough in natural regeneration stands where we have banked our regeneration using fire at 4-year intervals, we had less than 5% stem loss in each of 3 stands.
So what do we make this? First and perhaps most obvious, in severe ice storms, it doesn't matter what the pine species is in your plantation, particularly if they have been thinned in the past several years. Expect severe damage. Next it pays to have a diversity of management strategies for your forest holdings. Case in point - the selective cut. In the past I was very negative about using selective cutting as a regeneration/harvest strategy for shortleaf pine. Based on 18 years of watching this stand develop and seeing how it faired-almost no damage-in a severe ice storm, I have changed my tune. Further, economic analysis indicates a much higher rate of return under the scenario where cost-shares such as SIP and FIP are not available. Lack of cost-shares should ring a bell for some of you. Of the 6 forest management and regeneration strategies demonstrated at Robbers Cave, landowners always vote this number 1, after looking at economics and the aesthetics of the stand.
The importance of implementing several different forest management strategies was also shown on the Pushmataha area. Here with a less severe ice storm, we did see a significant difference between damage to natural shortleaf pine and plantation-grown loblolly pine. Interestingly enough, those natural stands that had been managed with periodic fire and exhibited characteristics of an uneven-aged stand (trees in 4 distinct age-classes) faired better than the even-aged naturally regenerated stands.
The take home message for this is that in light to moderate ice storms, naturally regenerated shortleaf fares better than planted loblolly pine (north of its native range). In severe ice storms, it doesn't matter. When you thin, don't thin every stand in the same year. Our observations were that recently thinned plantations were prone to greater ice damage. Here a long-term forest management plan that takes into account the potential risk associated with ice storms when targeting thinning dates, will pay out. A lot of factors influence the potential for loss in a given ice storm; storm severity, species of tree, age of stand, time since thinning, type of thinning (mid-story vs. canopy) and overall stand structure. And finally I recommend that you diversify your forest management strategy. Maintain some of your stands as even-aged stands and others as uneven-aged stands. Also maintain some natural and some plantation stands, after all, ice storms don't happen every year. Diversification is one of the oldest hedges against risk.
Robbers Cave Area
|click on photo for detailed view|