TITLE:
Impact of Tree Stump Harvesting on Soil Carbon and Nutrients and Second Rotation Tree Growth in Mid-Wales, UK
AUTHORS:
Elena I. Vanguelova, Rona Pitman, Sue Benham, Mike Perks, James I. L. Morison
KEYWORDS:
Forest Bioenergy, Stump Harvesting, Soil Carbon, Soil Nutrients, Tree Growth, UK
JOURNAL NAME:
Open Journal of Forestry,
Vol.7 No.1,
January
20,
2017
ABSTRACT: The drive to develop
renewable energy is increasing the interest in energy forestry. Woody biomass
from forest residues has the potential to make a significant contribution to
greenhouse gas emission reduction through fossil fuel substitution. However,
there is a danger of operational practice running ahead of the understanding of
the environmental impacts of such activities. Consequently, there is an urgent
requirement for scientifically underpinned guidance on the best management practices to ensure soil and water
protection, including sustaining forestry’s key role in carbon capture. This
study addresses the main issues associated with stump harvesting practices and
their impacts on soil carbon and nutrient capital and effects on the second rotation tree growth. It reports results from
a clearfell site in the UK where experimental stump harvesting was carried out
in 2005 before replanting with Sitka spruce Picea
sitchensis (Bon.)Carr. Both stump harvested and conventional harvested areas (Control) were studied in
2009 and 2010, five years after harvesting, on the two distinct soil types at
the site: podzolised brown earth and peaty gley soils. Results show impacts of
stump harvesting on soil carbon and nitrogen stocks, residual water, base
cations (K+, Ca2+ and Mg2+) concentrations and
stocks and bulk density in both soil types. The organic peaty gley soil showed
larger and deeper profile changes after stump harvesting compared with the
podzolised brown mineral soil, where some of the negative changes in C, N and
base cations in the top soil were compensated by increases at depth. Tree assessment
showed positive effect of stump harvesting on K and Ca uptake by young seedlings, but N and P nutrient
status was reduced on the peaty gley soils. The overall results support the
current UK forestry guidance for stump harvesting which identifies that soil
type is the most important site factor determining the sustainability of the
practice.