City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: http://read.dmtmag.com/i/94460
Checking in with Nina Bassuk & Cornell's Urban Horticulture Institute Photos Courtesy Cornell UHI the selection, evaluation and propagation of superior plants; assessing and ameliorating site limitations; transplant technologies; and working with municipali- ties. There is a wealth of research-based information for city foresters at www.hort.cornell.edu/uhi. What's the latest? We asked UHI Director and SMA-favorite Dr. Nina Bassuk. Urban Horticulture Institute (UHI) research falls under four categories, described succinctly as: What's new on the plant selection front? Nina Bassuk: Sometimes I wish I'd been a rice research- er. We've been working on developing urban-tolerant hybrid oaks for nearly 20 years! We want oaks that can withstand alkaline soil and show more vigor, transplant- ing ease, resistance to powdery mildew, and all-around stress resistance than what's currently available on the market. First we made crosses using one of four of the maternal parents, all from the white oak group so there would be genetic compatibility: Quercus macrocarpa, Q. bicolor, Q. muehlenbergii, or Q. robur. We crossed them with pollen from all over the country, including botanical gardens and growers. Out of that breeding we have 350 or so individuals, each reflecting a unique cross. We had to allow time for them to grow. The challenge now is to move the propagation rate along. If we get ten clones from one plant, that's not enough to meet the needs of an industry/attract their interest. So we are working on accelerating propaga- tion. Next spring, we will likely be making our first selec- tions with which to go further. We should cull many of the 350 but this will be difficult, as they have become like friends after all these years. We also continue to observe new cultivars in the city of Ithaca. That's not experimental work, but provides anec- dotal insight into the performance of new introductions in an urban environment. What's happening with CU-Soil (structural soil) and porous paving? NB: Adding the porous paving piece to CU-Soil (struc- tural soil) has allowed us to further explore, how much soil do you need to support a tree? Way back in 1991 Pat Lindsey and I coauthored a paper putting forth a model method of calculating this for trees in general. Now we have ground penetrating radar (GPR) and then to really check to see if our model was correct, to find 18 Stool-bed propagation is a form of layering to produce rooted shoots, or layers, for transplanting. It has been essential for UHI's oak hybrids work. "ground truth," we've done a whole series of scans of root systems, then we dug up the root systems to see how closely the scan matched reality. This is allowing us to get close to a 1:1 reading, at which point, we'd like to put up an online calculator for soil volume. Different species have different soil volume needs, so we're look- ing to provide for that, too. When Pat Lindsey and I first came up with that soil volume calculation method, it became clear that there were many places in the city where tree roots had no way to break out into larger root volumes—say, under sidewalks and over into a front lawn. That was the rea- son for developing structural soil, to make more rooting volume under pavement. Then next step has been to explore structural soil overlain by porous asphalt to allow for maximum water infiltration. This has benefits for the tree roots but also in terms of reducing the amount of stormwater infrastructure a municipality needs. We have found that roots in structural soil under porous pavement grow very deep, to the limit of the medium (24 in/61 cm). We have also found that there 50% more roots in this condition than one would find under non- porous asphalt. The more we replicate this, the more (right) A rooted stool-bed shoot that's been potted up City Trees