||CULTIVATION OF LIVING FENCES
||LIVING FENCEROWS IN SONORA FOR FLOODPLAIN MANAGEMENT AND SILT CAPTURE
||Rio San Miguel, Sonora, Mexico, North America
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|Continent: North America
Site: Rio San Miguel, Sonora
Description of the local variant of the technique
In Sonora, living fence-rows are used for floodplain management along agricultural fields. They are referred to locally as "woven fences" (cercos de tejido) or "branch fences" (cercos de rama).
Living fence-rows of willow (Salix gooddingii) and cottonwood (Populas fremontii) are planted between the Rio San Miguel and floodplain agricultural fields along the river. To plant the fence-rows, tall cuttings are made from mature, previously propogated fence-row trees, and a deep trench is dug down so that the water table is reached. The cuttings are planted fairly close to each other at even intervals (0.5 - 0.75 m), with the base planted firmly below the water level. Sand and gravel is then shoveled around the plantings. Generally, more willows are planted than cottonwoods. As the trees root and mature, brush is collected and woven between the trunks. Plants used for brush include Seep willow (Baccharis glutinosa), burrobush (Hymenoclea monogyra), mesquite (Prosopis iuliflora), and groundsel (Senecio salignus).
During flood events, the soil is stabilized by the roots of the planted fence. Floodwater is still able to permeate the woven brush, but with reduced intensity, allowing the floodwater to irrigate the agricultural fields in a controlled manner. The water is slowed enough to cause a deposit of carried sediments. This process not only fertilizes the agricultural fields with nutrient-bearing silt, it actually grows the fields over time, as most sediment is deposited directly on the other side of the fence. There are many recorded instances of new fence-rows being planted as the fields expand to meet the first fence.
Erosion of agricultural land is a pervasive and debilitating issue for cultures throughout history. Using living fence-rows in floodplain agricultural fields, valuable agricultural land is not only protected from erosion, but is actually improved in size and quality. The proliferation of selected willow and cottonwood trees further created excess lumber resources for fuel or construction. The trees also house insectivorous bird populations which help to control pests in the fields.
This provides a productive and sustainable solution to riverbank erosion that would endanger the river as well as the agricultural land around it. Survival prospects are improved by sustained river health and protection and fertilization of agricultural fields