Agroforestry is the broad term used to describe the model where trees and/or shrubs are integrated with other means of agricultural production. Drilling into this term a little further, we encounter two main approaches to agroforestry:
- Silvopasture: the integration of trees with livestock grazing systems (or vice-versa).
- Silvoarable: the integration of trees with agricultural or horticultural crops.
The Agroforestry Research Trust (UK) has a great website, which goes into a lot more detail about the various approaches to agroforestry.
The main benefits of incorporating trees within pastures are…:
- Microclimates – when positioned strategically, permanent pasture & buildings are protected from prevailing weather conditions; animal performance is improved, while mortality due to exposure is greatly reduced.
- Improved water cycle – various studies, including the work at Pontbren, have shown that water infiltration rates beneath shelterbelts & hedgrerow can be up to 60 times greater in comparison to neighbouring grassland. In addition to this, trees are nature’s water pumps. Through their natural transpiration, certain water-loving species will re-balance the local water cycle in otherwise water-logged areas, thus improving pasture quality.
- Improved mineral cycle – The roots of maturing & mature trees access deeper soil horizons than most pasture species. In the case of deciduous systems, minerals & nutrients from these deeper horizons accumulate within the biomass of leaves, then become available at the soil surface during the annual leaf drop, in autumn.
Here at ACD, tree systems are managed & established in the following ways:
Existing woodland pockets:
Existing pockets of woodland currently account for 12% of the land area under management. Most of these are relatively small areas & localised to steep terrain, where grazing pressure has been less intense, or sprawling hedgerows. Almost all of these areas have gone unmanaged for a number of decades, but are otherwise healthy.
New woodlots / extension planting:
A core objective of the An Caora Dubh Farm project is to increase native woodland cover in my locality; primarily for the purposes of biodiversity enhancement, but also for the additional benefits of shelter creation, improvements in water & mineral cycling & also as a resource for firewood, construction/craft product & broader amenity. The vision is to increase the proportion of the farm under native woodland from it’s current 12% to somewhere in the region of 50%. This will be achieved through a combination of planting greenfield sites in remote parts of the farm, planting on the periphery of existing pockets of woodland & the creation of extensive riparian buffers.
Riparian buffer zones:
Linear planting along waterways. These strips act to buffer run-off from adjacent land, thus protecting water quality. They also serve to prevent bank erosion and act as wildlife corridors.
Positioned to shelter areas of permanent pasture from the extremes of prevailing weather conditions.
Productive tree lines area laid out across the landscape to delineate grazing corridors. Contour planting acts to intercept overland water flow & cause it to “slow & soak” into the soil. Other variations of this strategy include “keyline” & “off-contour” patterning [which are not the same thing…!] to help redistribute water more efficiently across a landscape.
Discrete belts of woodland, newly planted, which connect existing and otherwise isolated pockets.