United States Department of Agriculture, Agricultural Research Service, Eastern Oregon Agricultural Research Center, Burns, OR, USA.
Environ Manage. 2011 Mar;47(3):468-81. doi: 10.1007/s00267-011-9629-0. Epub 2011 Feb 23.
Pinus-Juniperus L. (Piñon-juniper) woodlands of the western United States have expanded in area nearly 10-fold since the late 1800's. Juniperus occidentalis ssp. occidentalis Hook. (western juniper) dominance in sagebrush steppe has several negative consequences, including reductions in herbaceous production and diversity, decreased wildlife habitat, and higher erosion and runoff potentials. Prescribed fire and mechanical tree removal are the main methods used to control J. occidentalis and restore sagebrush steppe. However, mature woodlands become difficult to prescribe burn because of the lack of understory fuels. We evaluated partial cutting of the woodlands (cutting 25-50% of the trees) to increase surface fuels, followed by prescribed fire treatments in late successional J. occidentalis woodlands of southwest Idaho to assess understory recovery. The study was conducted in two different plant associations and evaluated what percentage of the woodland required preparatory cutting to eliminate remaining J. occidentalis by prescribed fire, determined the impacts of fire to understory species, and examined early post-fire successional dynamics. The study demonstrated that late successional J. occidentalis woodlands can be burned after pre-cutting only a portion of the trees. Early succession in the cut-and-burn treatments were dominated by native annual and perennial forbs, in part due to high mortality of perennial bunchgrasses. By the third year after fire the number of establishing perennial grass seedlings indicated that both associations would achieve full herbaceous recovery. Cutting-prescribed fire combinations are an effective means for controlling encroaching late successional J. occidentalis and restoring herbaceous plant communities. However, land managers should recognize that there are potential problems associated with cutting-prescribed fire applications when invasive weeds are present.
自 19 世纪末以来，美国西部的松-柏（Piñon-juniper）林地面积扩大了近 10 倍。西方刺柏（western juniper）在山艾灌丛草原的主导地位带来了几个负面影响，包括草本植物产量和多样性减少、野生动物栖息地减少，以及侵蚀和径流潜力增加。规定火烧和机械清除树木是控制 J. occidentalis 和恢复山艾灌丛草原的主要方法。然而，由于缺乏下层植被燃料，成熟的林地变得难以规定燃烧。我们评估了林地的部分砍伐（砍伐 25-50%的树木），以增加地表可燃物，然后在爱达荷州西南部的晚期演替 J. occidentalis 林地进行规定火烧处理，以评估林下植被的恢复情况。该研究在两种不同的植物群系中进行，评估了需要进行多大比例的林地预备性砍伐才能通过规定火烧消除剩余的 J. occidentalis，确定火烧对林下物种的影响，并检查火灾后的早期演替动态。研究表明，晚期演替的 J. occidentalis 林地可以在预先砍伐部分树木后进行火烧。在砍伐和火烧处理中，早期演替主要由本地一年生和多年生草本植物组成，部分原因是多年生丛生草的高死亡率。火灾后第三年，建立的多年生草本植物幼苗数量表明，两个群系都将实现草本植物的完全恢复。砍伐与规定火烧相结合是控制侵入性晚期演替 J. occidentalis 和恢复草本植物群落的有效手段。然而，土地管理者应该认识到，当存在入侵杂草时，砍伐与规定火烧应用可能存在潜在问题。
