I have spent a couple more weeks in Vinnitska Oblast since my last post, and have learned even more about forest-steppe oak and the challenges of managing it. I took a great field trip with my colleague from the Agricultural University, Evgeniia Kremenetska. She is trying to demonstrate new silvicultural methods in the region, and has plots in Krizhopil in the south of oblast. In this region Quercus petraea naturally dominates, while Q. robur makes up a lesser component.
Krizhopil got slammed by the same ice storm that I described in my last post. Nearly 100% of the management unit was effected, and most tree crowns sustained heavy damage. The foresters told me right off that this crown damage made natural regeneration of oak (which they already consider really hard) next to impossible. I was skeptical, especially when we saw a clearcut from last year that had abundant Q. petraea regen mixed between the planted rows of Q. robur. But then we visited a mature stand that is slated for salvage clearcutting. We found two beautiful petraea that still had good crowns, and the ground was absolutely covered in acorns. (We did a little measuring and found that 50% of them were viable). I thought, "see, you could regenerate this naturally!" But when we walked around the rest of the stand pulling back the leaf litter we could barely find another viable acorn. When you looked up the oak crowns were just a bunch of broken branches and watersprouts. We repeated this experience in several more stands and I started to believe that the regenerative potential of these stands was really compromised by the storm. Whether these crowns could recover to acorn-producing quality with more time is another question...
The solution in Krizhopil has mostly been to salvage these damaged stands (often several decades before rotation age) and to establish plantations of Q. robur (it is really hard to grow petraea in nurseries, so all artificial regen here is the other oak species). When they can get some good post-clearcut natural regeneration, that's icing on the cake. But they aren't going to rely on it. Here Evgeniia is experimenting with underplanting oak seedlings before the final harvest, in the hope that they will be more established and competitive after a few years in the understory than seedlings planted post-harvest. If they are, it might be necessary to do less intensive cleaning treatments, because the oak will be more capable of competing with the hardwood brush and ruderals. We saw nice rows of seedlings growing beneath a lightly thinned canopy. The next stage of the experiment will be to see whether it is possible to protect these seedlings during harvesting.
My impression from Krizhopil was a bit sad - in response to the ice storm damage, a large area of natural forest (albeit highly modified natural forest) is going to be converted to intensive oak plantations. This would have happened anyway as rotation age was reached, but the storm greatly accelerated the process. The foresters do not have any realistic alternative to salvage-plant (both due to the natural challenges and a dearth of research on natural regen). What makes this sadder is that the storm basically pounded the region where Q. petraea is dominant. The area of petraea forests in Ukraine was already shrinking; now it will contract even faster.
I think there should be some measures taken to maintain a significant acreage of natural petraea forests, since the Ukrainian forest-steppe population is isolated and genetically unique. Even damaged forests could be important for maintaining this species, but of course conserving these areas would entail a major sacrifice for the forest management units. I imagine a survey of existing petraea forests in Vinnitska and Odeska Oblasts, in which the healthiest and most viable stands are identified and excluded from conversion. Perhaps even individual trees could be conserved, like those good acorn producers we saw in Krizhopil.
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