قطع کردن درختان با حفاظت از درخت دانه در جنگل های کاج قرمز همراه با افزایش جمعیت مرغ شبانه پشه خوار مشرق امریکا (ج ش)

ABSTRACT Clearcut with seed trees in red pine forests associated with increased occupancy by Eastern Whip-poor-wills

Over the past half century early-successional forests have declined in certain regions of northeastern North America (Askins, 2001). In the US Great Lakes states the proportion of timberlands in the seedling–sapling stage declined from 50–60% in the 1950s to 28% in the 1990s (Trani et al., 2001). Similar declines in early-successional forests occurred in most other northeastern US states and adjacent Ontario, Canada (Askins, 2000; Blancher et al., 2007). For instance, mature forests increased at the expense of early-successional forests in New Hampshire from 47% in 1880 to 87% in 1980 (Litvaitis, 1993), while mature forests increased in Ontario south of the Canadian Shield from 10% in 1920 (Larson et al., 1999) to 29% in 2006 (OMNR, 2006). The causes of declines in early-successional forests depend on various regional pressures (DeGraaf and Yamasaki, 2003). In most of the northeastern US declines are attributed mainly to reforestation of abandoned farms, cleared originally in the 1800s and early 1900s (e.g., Litvaitis, 1993). By contrast, in parts of central Ontario where agriculture has always been largely absent (e.g., Algonquin Provincial Park), declines are attributed mainly to fire suppression (Williams, 2009; Tozer, 2012). Other causes leading to declines in early-successional forests in certain areas include fewer disturbance-creating floods due to storm water management and fewer meadow-creating beavers due to trapping and protection of property (DeGraaf and Yamasaki, 2003). Early-successional forests have always been present on the landscape due to disturbance, reaching their highest rate of occurrence following European land-clearing for settlement and prior to widespread fire control (Riley, 2013). Evidence suggests, however, that early-successional forest habitats have since declined to a point below their natural rate of occurrence in some regions of northeastern North America (Lorimer and White, 2003). For instance, the current extent of early-successional forests in pine dominated areas in central Ontario is closer to natural levels now than following European settlement and prior to fire suppression, but the extent may have fallen below the natural rate of occurrence by more than a quarter (Elkie et al., 2013)