Environmental Engineering Reference
In-Depth Information
depending on soil physical properties, fertility, topographic position, crop type, and management
history. For example, Dabney et al. (2004) found that removal of corn residues doubled erosion
rates in conventional and no-till tillage systems on silt loam soils in northern Mississippi. However,
Lafond et al. (2009) were unable to find a significant long-term (50-year) correlation between reten-
tion of above-ground residues in wheat (
Triticum
spp.) cropping systems and soil organic matter
or organic nitrogen under conventional tillage on more level terrain in the thin-black soil zone of
Saskatchewan, Canada.
In managed forests, logging slash (i.e., branches and nonmerchantable bole wood; Figure 6.2) and
dead standing and down trees are often collectively referred to as forest “residues.” Small nonmer-
chantable trees left after harvest, which are undesirable as future growing stock, may also be included
in this category. Estimates suggest that 2.7 million t of forest residues may be available annually in
Michigan alone (Froese 2007). Most of the current discussion related to the sustainability of harvest-
ing this material stems from concerns regarding the depletion of soil nutrients and site productivity
(Mann and Tolbert 2000), especially on coarse textured soils or under very short rotations. Available
research contrasting contemporary stem-only with whole-tree harvesting systems has failed to find
lasting effects on site productivity unless harvesting activities result in significant disturbance to
the forest floor (Johnson 1992; Johnson and Curtis 2001). However, on some sites, there is a strong
potential for calcium depletion (Boyle et al. 1973; Mann et al. 1988; Federer et al. 1989), which may
require remediation possibly with ash fertilization (Vance 1996). Less attention has been given to the
role of these materials as wildlife habitat and substrates for plant establishment.
FIGure 6.2
Logging residues (tops, branches, and nonmerchantable bole wood) left after a partial harvest
of a mixed stand of aspen (
Populus
spp.) and conifers. If managed sustainably, this material may provide an
important source of biomass for bioenergy from traditional forest management activities. (From Janowiak,
M.K. and Webster, C.R.,
J Forestry
, 108, 16-23, 2010.)
