Soil is Not Renewable

- by Friends of the Wild Swan and Swan View Coalition

Soils are the foun­da­tion of ter­res­tri­al life. For­est pro­duc­tiv­i­ty is direct­ly tied to soil con­di­tions. Soil takes thou­sands of years to devel­op and is not “renewable“on a human time scale. Soil is an ecosys­tem in itself that must be healthy in order to pro­vide for healthy forests, grass­lands, and aquat­ic sys­tems. Actions impact­ing such com­plex sys­tems are prone to unin­tend­ed con­se­quences. Giv­en the life-sup­port role soils play, spe­cial care and pru­dence are essential. 

The Nation­al For­est Man­age­ment Act (NFMA) pro­hibits “irre­versible dam­age” to soils as well as “sub­stan­tial and per­ma­nent impair­ment of pro­duc­tiv­i­ty of land.” Loss of soil (ero­sion) and dis­place­ment clear­ly cause “irre­versible dam­age” and “per­ma­nent impair­ment of pro­duc­tiv­i­ty of land.” Loss of coarse woody debris caus­es soil dam­age that can last a cen­tu­ry or more. Soil com­paction neg­a­tive­ly impacts soil pro­duc­tiv­i­ty, over­land flow, ero­sion, stream sed­i­men­ta­tion, and late sea­son flows. Soil com­paction from log­ging can per­sist 50 – 80 years. 

Avoid­ing soil dam­age is the only option; full restora­tion of soil dam­age is not gen­er­al­ly pos­si­ble. Com­pact­ed soils are not com­plete­ly mechan­i­cal­ly restor­able. Mech­a­nized decom­paction is only par­tial­ly effec­tive at decom­pact­ing and can com­pound prob­lems by mix­ing rock and min­er­al soil with top­soil result­ing in long term reduced pro­duc­tiv­i­ty. Replac­ing erod­ed or dis­placed soil is prob­lem­at­ic. Arti­fi­cial coarse woody debris replace­ment is not prac­ti­cal over large areas such as burned clearcuts.

Tim­ber har­vest prac­tices includ­ing road build­ing, log skid­ding and slash dis­pos­al have caused most soil dam­age on for­est lands. 

Nutri­ent recy­cling is a crit­i­cal func­tion of soils that his­tor­i­cal­ly has been dam­aged by treat­ments that neg­a­tive­ly affect the amounts, types, and dis­tri­b­u­tion of organ­ic mat­ter retained on site. Many years of pil­ing and windrow­ing of slash using doz­er blades has removed not only the lit­ter plus duff lay­ers but also the thin lay­er of organ­ic rich min­er­al soil (A hori­zon) from large acreages of forest­ed lands. Guide­lines for retain­ing ade­quate coarse woody debris should be devel­oped based on the site poten­tial and be with­in the his­toric range of vari­abil­i­ty for the fire regime of the site. Coarse woody debris needs to be main­tained at nat­ur­al lev­els in the inter­face zone, with excep­tion grant­ed imme­di­ate­ly around struc­tures and residences. 

Con­trol of live­stock con­cen­tra­tion, espe­cial­ly in sen­si­tive ripar­i­an areas is essen­tial to main­tain­ing soil poros­i­ty and bulk den­si­ty. The moist soils in these areas become com­pact­ed by con­cen­tra­tions of cat­tle in only a few days. Gen­tle upland ridge tops and swales are oth­er “gath­er­ing places” for cat­tle that require spe­cial efforts to con­trol their dis­tri­b­u­tion to pro­tect soils from detri­men­tal compaction. 

The process of nutri­ent cycling on the for­est lands is pri­mar­i­ly effect­ed through fire; this recy­cling is key to for­est and grass­land ecosys­tem health. There­fore, the use of fire when treat­ing veg­e­ta­tion should be in accor­dance with the nat­ur­al fire regime for the site, and organ­ic mat­ter left on site should be with­in the nat­ur­al his­toric range of vari­abil­i­ty for the site type. 

Myc­or­rhizal fun­gi are an essen­tial com­po­nent of pro­duc­tive soil. Most regen­er­a­tion fail­ures may be due to prob­lems with myc­or­rhizae. Mon­i­tor­ing myc­or­rhizae needs to be part of soil con­di­tion assess­ments. Myc­or­rhizae are very tem­per­a­ture sen­si­tive, so soil tem­per­a­tures need to be monitored.

Mon­i­tor­ing of detri­men­tal soil dis­tur­bances needs to include: com­paction, dis­place­ment, rut­ting, severe burn­ing, ero­sion, loss of sur­face organ­ic mat­ter (espe­cial­ly coarse woody debris), soil mass move­ment, soil tem­per­a­ture, and dam­age to micro-bio­log­i­cal com­po­nents of soil (espe­cial­ly myc­or­rhizal fungi). 

Giv­en that mon­i­tor­ing has demon­strat­ed an exten­sive lega­cy of soil dam­age, it is time to include that infor­ma­tion in water­shed health assess­ments. There needs to be an inven­to­ry of where these high­ly dam­aged soils occur and the extent to which they are dam­aged. The For­est Plan needs to quan­ti­fy the acreages by water­shed and do cumu­la­tive effects analy­sis, includ­ing the road sys­tems to under­stand the full impact man­age­ment has had on water­shed health.