Effects of intensive forest management on stand and landscape characteristics in northern New Brunswick, Canada (1945-2027).

摘要

Historical and future projected landscape patterns and changes caused by harvesting and silviculture were evaluated for a 189,000 ha, intensively managed forest in New Brunswick, Canada. We compared changes in species composition, age classes, and patch characteristics (area, size, density, edge, shape, and core area) between 1945, 2002, and projections to 2027 (based on the landowner's spatial forest management plan). In 1945, the landbase was 40% softwood, 37% mixed hardwood-softwood, 10% hardwood, and 9% softwood-cedar. From 1945 to 2002 and 2027, respectively, softwood forest area increased by 2 and 11%, mixedwood decreased by 19 and 20%, and hardwood area increased by 15 and 14%, and softwood-cedar increased by 6% and then decreased by 7%. In 1945, forest >70 years old comprised 85% of the landscape, but declined to 44% in 2002 and was projected to encompass 41% in 2027. Increased area harvested, decreasing harvest patch size, and protection against natural disturbances resulted in progressively smaller mean and less variable patch sizes from 1945 to 2002. Based upon the 25-year forest management plan, this trend was projected to continue, with the exception of nine patches >1000 ha created by 2027, eight of which were softwood plantations. Stand type successional dynamics were highly variable in both harvested and non-harvested areas, and in some cases were unexpected. Few of the 1945 stand types remained static by 2002, with 42 and 35% of mixedwood shifting to softwood as a result of harvesting, and to hardwood as a result of both harvesting and spruce budworm (Choristoneura fumiferana Clem.) outbreaks in the 1950s and 1970s. This study demonstrates the strong cumulative effect of forest management on landscape patterns, especially the socially mandated drive for smaller clearcuts resulting in the loss of large patches..