The growth and productivity of British Columbia’s interior forests is largely
limited by soil nutrient availability. Fertilization has been shown to be an effective
silvicultural tool for increasing the development of immature stands throughout the
region. This has lead to increased interest in long-term, repeated fertilization as a means
of addressing timber-supply shortfalls as a result of the current mountain pine beetle
(Dendroctonus ponderosae) outbreak. However, there is little information related to the
impacts of repeated fertilization on the cycling of nutrients in many of these stands. This
study makes use of a long-term (13-15 year) fertilization experiment in two lodgepole
pine (Pinus contorta Dougl. var. latifolia Engelm) and two interior spruce (Picea glauca
[Moench] Voss and Picea engelmannii Parry) forests in the central interior of British
Columbia subject to two levels (periodic and annual) of nitrogen(N)-based fertilization.
The primary goal of the project was to examine the effects of different fertilizer regimes
on aspects of soil chemistry. Specifically, this project was concerned with the impacts of
repeated fertilization on: 1) soil carbon (C) and N cycling, and 2) soil base cation (e.g.,
Ca, Mg & K) availability. Soil and foliar nutrient regimes were quantified throughout the
2008 and 2009 growing seasons using ion-exchange membrane (IEM) plant root
simulator (PRS) probes and traditional soil and foliar analyses. Fertilization increased N
cycling at all sites, with generally elevated soil and foliar N and significant soil-foliar N
relationships in several cases. Nitrate (NO3
-) increased in the fertilized plots in several
cases; however, there was minimal evidence of NO3
- leaching. Greater than 90% of
fertilizer-N inputs were retained onsite, suggesting these forests are not N-saturated. Soil,
tree and total ecosystem C generally increased in response to fertilization, with the spruce
sites exhibiting greater C accrual per unit of fertilizer N than the pine sites. Further,
significant linear relationships between soil C and N were evident at all sites. At sites
with poorly buffered soils (pH < 4), fertilizer treatments generally led to increased soil
acidification and decreases in soil and foliar Ca. Decreases in soil Ca may have been due
to significant increases in sulfate leaching; whereas foliar Ca decreases appear to be
related to compromised uptake systems, potentially from increased soil aluminum.
Buffering capacities, rather than forest type, appear to be the best predictor of soil and
foliar Ca responses to fertilization. Despite significant changes in soil chemistry at all
four sites, it does not appear that current fertilization rates are detrimentally affecting tree
growth. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3615 |
| Date | 18 October 2011 |
| Creators | Harrison, Daniel |
| Contributors | Maynard, Douglas George, Niemann, K. O. |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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