I never met my great-grandmother, but know that one of her favorite sayings was “A stitch-in-time, saves nine.” And, this folk wisdom embodies a valuable lesson for every land manager: a little early, preventative maintenance can eliminate the need for a much larger repair job after that missing ‘stitch’ becomes a larger rip or hole.
Maintenance is every bit as important to integrity and functionality of shelterbelts, riparian and other conservation reserves as is their placement and establishment. Or as aptly put in another aphorism: a chain is only as strong as it’s weakest link.
Throughout North America many have recent experience with the awesome forces of wind or water. Torrents of rain and snow melt, accumulate and flood across the landscape, at times eroding way thousands of years of soil building in a matter of hours. And a record year for spring tornadoes is causing havoc, loss of life and property in the US mid- and south-west.
When faced with the full onslaught of natural forces, there is little to nothing you can do. A mature, deep rooted tree, is still no match for a tornado or hurricane-force wind. Likewise, the full-force flow of high-volume, fast-moving water can strip bare any riparian zone.
But outside and at the edges of these extremes are zones that are able to remain intact and functional if they are properly structured and managed. And not only will a conservation planting or reserve stand up to considerable stress, they also function to reduce the extremes experienced downstream or leeward. Trees and shrubs along riparian areas will slow water flow and absorb some of the turbulent energy in a raging torrent. Likewise, trees and shrubs in shelterbelts and conservation reserves bend and sway in the wind, absorbing energy from the airflow and deflecting the main force of strong winds away from sensitive areas.
But maintenance is critical to keep the integrity spatially over the entire shelterbelt / reserve and also through time. This is probably most acute with conservation plantings where all the individual components have been planted at the same time. If the area was not planted with a mixture of different-maturing species, the reserve will mature and die all at about the same time. In the absence of new tree or shrub recruitment, you are then faced with natural mortality over relatively short time span, greatly reducing or eliminating the effectiveness of the planting. It is therefore important to plan and plant a mix of species from the start, and take measures to protect natural regeneration or fill-plant species over time, so that the system perpetuates and renews itself.
Shelterbelts and conservation reserves established specifically for sheltering against the effects of wind, also require maintenance of the overall density of planting through pruning and/or thinning to achieve the optimal range for buffering (in the range of 50 to 70 %). Not dense enough, and a shelterbelt does not present enough of a barrier to the wind. Too dense, and they effectively become a solid barrier, creating a back flow of air when wind forces against it, over which the main air stream can lift, picking up speed and energy, and thus compounding the erosion potential.
And most problematically in riparian and conservation reserves designed to hold soil loss back from water erosion, even a small gap in these reserves can pose vulnerability to a much larger area through gully erosion. If an area is subjected to concentrated water flows, a stretch of only a few unprotected metres of bare soil can start to erode downward through the soil profile and into the subsoil. This gully can then feed itself, undercutting the rooting layer of adjacent trees and shrubs, causing them of overturn and expand the zone of vulnerability. In the process thousands of years of soil building and hundreds of years of plant community development can be swept downstream in a few days or even a few hours.
Routine inspection and corrective maintenance to identify and restore vulnerable areas in your conservation plantings, shelterbelts and riparian zones can be that ‘stitch-in-time’ to save soil and eliminate the need for a much larger restoration effort.