{"id":79,"date":"2019-04-06T21:46:19","date_gmt":"2019-04-07T01:46:19","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/?post_type=chapter&p=79"},"modified":"2020-10-31T00:18:49","modified_gmt":"2020-10-31T04:18:49","slug":"topic-6-5-forests-on-extremely-nutrient-poor-soils","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/chapter\/topic-6-5-forests-on-extremely-nutrient-poor-soils\/","title":{"raw":"Topic 6.5: Forests on Sites with Extreme Conditions","rendered":"Topic 6.5: Forests on Sites with Extreme Conditions"},"content":{"raw":"To the extent that all trees and other forest plants require the same resources for regeneration and growth (e.g., light, water, and nutrients), silvicultural treatments for increasing stocking and growth rates are fairly generalizable.\u00a0 But there are many forests which require special attention due to extreme edaphic conditions, flooding frequencies, steep slopes, or high elevation.\r\n

Forests on extremely nutrient-poor soils<\/h1>\r\nHarvesting timber entails removal of nutrients and physical disturbances that affect rates of nutrient mineralization, leaching, and erosion.\u00a0 Where soils are extremely nutrient poor (=oligotrophic), special care must be taken to avoid further depleting nutrient reserves and thereby jeopardizing future site productivity and commercial yields.\u00a0 On many oligotrophic sites, most of the nutrient reserves are in the living biomass and soil organic matter.\u00a0 Whatever silviculture techniques are employed on such sites, they must protect these nutrient reserves.\u00a0 The best general approach is to treat the forest very gently.\u00a0 Open only small gaps, leave the relatively high nutrient content bark and branches on site, and restrict the harvest intensity so as to reduce the removal of nutrients from the forest.\r\n

Forests on steep or otherwise erosion-prone sites<\/h1>\r\nErosion is a problem on all but the flattest and best drained sites, but some forests are extremely prone to erosion by flowing water.\u00a0 Erosion a particular concern in forests in critical watersheds, even if the site is not especially erosion-prone.\u00a0 The likelihood and severity of erosion is a function of soil structure, vegetative cover, rainfall intensity, and slope steepness and length.\u00a0 As natural forest management is relegated to poorer and poorer sites, foresters will increasingly have to contend with steep slopes and the suite of associated problems.\u00a0 Also, with increasing scarcity of forest resources, forests in watersheds that should be completely protected will be under increasing pressure for harvesting.\r\n\r\nThe best way to avoid soil erosion is to prevent development of the conditions that favor it.\u00a0 For example, forests on very steep slopes (>35o<\/sup>) should not be harvested.\u00a0 Forests on more modest slopes (20-35o<\/sup>) might be harvestable using aerial extraction methods (e.g., helicopters on skyline systems), but not with ground based yarding.\u00a0 Harvesting should be suspended during rainy periods and machines and methods designed to reduce soil compaction (e.g., wide-tracked skidders using well-planned skid trails) should be employed.\r\n\r\nForests on steep slopes differ from those on level ground in several ways.\u00a0 Where soils are at all unstable, curved boles and other basal stem deformities tend to be more common on slopes.\u00a0 Forests on slopes are also usually very dynamic due to frequent treefalls, soil slumping, and larger landslides.\r\n\r\nThe costs and difficulties of timber harvesting generally increase with increasing slope.\u00a0 Because the crowns of trees on slopes tend to be better developed on the downhill side, directional felling is difficult unless the trees are climbed and winched uphill.\u00a0 Such an effort might be cost effective considering the likelihoods of bole damage and excessive disruption of the residual forest when trees are felled downhill. If forests on steep slopes must be harvested, the role of trees in soil stabilization should be kept constantly in mind.\u00a0 Removal of too many trees will destabilize slopes and increase the risk of landslides.\u00a0 Road and skid trail construction on slopes also increases landslide risks by disrupting water infiltration into the soil, impounding water, and creating local slopes steeper than their angle of repose.\u00a0 Machine traffic near the headwaters of small streams is of particular concern because these areas are naturally unstable and are the sources of much sediment in even undisturbed water catchments.","rendered":"

To the extent that all trees and other forest plants require the same resources for regeneration and growth (e.g., light, water, and nutrients), silvicultural treatments for increasing stocking and growth rates are fairly generalizable.\u00a0 But there are many forests which require special attention due to extreme edaphic conditions, flooding frequencies, steep slopes, or high elevation.<\/p>\n

Forests on extremely nutrient-poor soils<\/h1>\n

Harvesting timber entails removal of nutrients and physical disturbances that affect rates of nutrient mineralization, leaching, and erosion.\u00a0 Where soils are extremely nutrient poor (=oligotrophic), special care must be taken to avoid further depleting nutrient reserves and thereby jeopardizing future site productivity and commercial yields.\u00a0 On many oligotrophic sites, most of the nutrient reserves are in the living biomass and soil organic matter.\u00a0 Whatever silviculture techniques are employed on such sites, they must protect these nutrient reserves.\u00a0 The best general approach is to treat the forest very gently.\u00a0 Open only small gaps, leave the relatively high nutrient content bark and branches on site, and restrict the harvest intensity so as to reduce the removal of nutrients from the forest.<\/p>\n

Forests on steep or otherwise erosion-prone sites<\/h1>\n

Erosion is a problem on all but the flattest and best drained sites, but some forests are extremely prone to erosion by flowing water.\u00a0 Erosion a particular concern in forests in critical watersheds, even if the site is not especially erosion-prone.\u00a0 The likelihood and severity of erosion is a function of soil structure, vegetative cover, rainfall intensity, and slope steepness and length.\u00a0 As natural forest management is relegated to poorer and poorer sites, foresters will increasingly have to contend with steep slopes and the suite of associated problems.\u00a0 Also, with increasing scarcity of forest resources, forests in watersheds that should be completely protected will be under increasing pressure for harvesting.<\/p>\n

The best way to avoid soil erosion is to prevent development of the conditions that favor it.\u00a0 For example, forests on very steep slopes (>35o<\/sup>) should not be harvested.\u00a0 Forests on more modest slopes (20-35o<\/sup>) might be harvestable using aerial extraction methods (e.g., helicopters on skyline systems), but not with ground based yarding.\u00a0 Harvesting should be suspended during rainy periods and machines and methods designed to reduce soil compaction (e.g., wide-tracked skidders using well-planned skid trails) should be employed.<\/p>\n

Forests on steep slopes differ from those on level ground in several ways.\u00a0 Where soils are at all unstable, curved boles and other basal stem deformities tend to be more common on slopes.\u00a0 Forests on slopes are also usually very dynamic due to frequent treefalls, soil slumping, and larger landslides.<\/p>\n

The costs and difficulties of timber harvesting generally increase with increasing slope.\u00a0 Because the crowns of trees on slopes tend to be better developed on the downhill side, directional felling is difficult unless the trees are climbed and winched uphill.\u00a0 Such an effort might be cost effective considering the likelihoods of bole damage and excessive disruption of the residual forest when trees are felled downhill. If forests on steep slopes must be harvested, the role of trees in soil stabilization should be kept constantly in mind.\u00a0 Removal of too many trees will destabilize slopes and increase the risk of landslides.\u00a0 Road and skid trail construction on slopes also increases landslide risks by disrupting water infiltration into the soil, impounding water, and creating local slopes steeper than their angle of repose.\u00a0 Machine traffic near the headwaters of small streams is of particular concern because these areas are naturally unstable and are the sources of much sediment in even undisturbed water catchments.<\/p>\n","protected":false},"author":656,"menu_order":5,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-79","chapter","type-chapter","status-publish","hentry"],"part":70,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/chapters\/79","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/wp\/v2\/users\/656"}],"version-history":[{"count":4,"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/chapters\/79\/revisions"}],"predecessor-version":[{"id":355,"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/chapters\/79\/revisions\/355"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/parts\/70"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/chapters\/79\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/wp\/v2\/media?parent=79"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/pressbooks\/v2\/chapter-type?post=79"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/wp\/v2\/contributor?post=79"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/fode014notebook\/wp-json\/wp\/v2\/license?post=79"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}