Wednesday, November 16, 2011

Big Cedars

People wonder why I spend so much time removing Eastern Red Cedars from the prairie and then leave the largest cedar trees in place. My management decisions in this case are driven by two primary considerations; 1 – The supposed historical composition of the Adams County prairie openings and 2 – The effects realized by the presence or absence of the cedars in question. Early descriptions of these small prairie landscapes often include the presence of scattered large cedars surrounded by prairie type vegetation.

A single large cedar can usually exist without producing enough shade to completely eliminate the neighboring prairie vegetation. The most noticeable impact of a large cedar is the change of moisture regime in the surrounding soil. A large percentage of rain falling on a cedar is funneled by the branches in towards the trunk. The water follows the trunk to the ground and forms a high moisture collar that may be several inches wide. This seems to produce an ideal nursery for germination of seeds and growth of new plants. The rest of the area beneath the tree canopy tends to be excessively dry because of the loss of direct rainfall, as well as the rapidity at which the shallow cedar roots pull moisture from the soil.

The upper reaches of a large cedar is a prime nesting location for various hawks and a preferred roost for owls. Many bird species flock in to feed on the massive quantities of berries that ripen in the fall. This tree lost a large branch to an ice storm several years ago, opening up a window into the normally hidden interior.

A grouping of large cedars can produce enough shade to change the vegetation pattern, but most of the plants are still prairie associates. A few of the species even seem to benefit by the arrangement. I think the relationship between the cedars and the prairie flora and fauna deserves more study. I know that the diversity of a site is enhanced by the presence of the cedars, but I suspect there to be some interrelationships in play that are unique to this ecosystem.

On sites that were historically used to graze livestock, it’s not unusual to find large cedars with smooth trunks unmarred by dead branch stubs. In the early 1900’s, this area would have been used as pasture and it’s a good bet that the pasture was severely overgrazed by cattle. It’s also likely that there were a couple of horses or mules in the mix. 1938 aerial photos clearly show these large cedars already well established in the fields, so the livestock would have been interacting with what were probably medium sized cedars at the time. Cattle would have used the cedars for shade and rubs and if forage conditions were really bad, would have even nibble the branches. Horses or mules would have browsed the small branches from the cedars for as high as they could reach. The result is a nice, smooth trunked cedar.

Above the bare trunk is a profusion of branches. The fact that these trees are so clearly visible on early aerial photos helps me accurately match early land features with those that exist today.

Behind these two large cedars is a developing forest of medium sized cedars. An excess of cedars produces enough shade to effectively eliminate the prairie vegetation. I’m actively working to remove these medium cedars. I take enough out each year to maintain adequate sunlight for the prairie plants. I limit my cutting to the capability of the existing brush piles to receive new material. Once I’ve increased the height of the brush pile to its practical limit, I move on and clear cedars somewhere else. It makes for a lot of small, manageable projects that keep with my philosophy of making gradual change.

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