Spruce Responds to River Discharge
We examined the relationship between white spruce radial growth
rates and Tanana River discharge (amount of water per unit of
time) at the Bonanza Creek Experimental Forest Long-term Ecological
Research site (LTER). We obtained cross sections of white spruce
stumps from a recent harvest, and cored more than 100 white spruce
trees growing on the Tanana River floodplain. Unlike upland trees,
floodplain spruce growth did not respond to summer temperatures
and responded less to precipitation. Although the ring-widths
did not reflect flood events, the analyses did detect a relationship
between river discharge rates and white spruce radial growth.
Discharge rates on the glacier fed Tanana River increase with
temperature as well as precipitation. Although hot dry weather
limits the growth of white spruce in upland areas, these same
weather conditions can increase river discharge, thus preventing
reduced growth rates of floodplain trees. These results suggest
that floodplain spruce sites are productive for fundamentally
different reasons than upland sites.
Phyllis Adams and Glenn Juday
White Spruce Growth is Consistent with Increased Climatic
Stress
White spruce wood sections from Bonanza Creek LTER site were
analyzed by two unconventional techniques. Passing an x-ray beam
through wood measures its density, and year-to-year variations
in density are related to the climate. Wood produced each year
incorporates different amounts of stable isotopes (chemical variants
of elements that differ only by the number of neutrons). Other
studies have established that an increase in the amount of the
carbon13 isotope ( 13 C) compared to the normal carbon12 in a
plant's tissue is a measure of moisture stress. We correlated
stable isotope and density values with Fairbanks monthly temperature
and precipitation data. While previous studies in Alaska have
established good correlations of tree-ring width with multi-year
climate indices, our results are based on correlation of wood
properties with climate in the year the ring was formed. Other
studies have demonstrated that the maximum density of late-wood
in a tree ring indicates moisture stress. The maximum density
of late-wood in the LTER sample during the period 19091981 was
highly correlated with warm May and August temperatures. Density
has reached extreme high values in the last few years measured.
13 C enrichment was negatively correlated with growth year precipitation
and positively correlated with summer temperature. Recent delta
13 C enrichment (about one part per thousand) is the highest recorded
in the 20 th century. Both density and isotope measurements establish
that since the late 1970s white spruce trees are experiencing
extreme levels of climatically driven stress.
Valerie Barber and Glenn Juday
Detecting Wildfires
We started testing three different methods for detecting actively
burning wildfires in Interior Alaska using daily Advanced Very
High Resolution Radiomenter (AVHRR) satellite data. We are using
1995/96 satellite imagery with known fire locations obtained from
the Alaska Fire Service to evaluate which method is best to use
in Alaska. Previous research on fire detection using AVHRR data
has been mostly from lower latitudes. Unique problems at high
latitudes include no darkness during the summer and reflection
in the thermal band from glacial deposits.
Steve Boles and Dave Verbyla
Modeling Landscape Level Management
Previous efforts centered on developing a water balance model
that could be applied at the landscape level by virtue of its
hierarchical structure of "segments", running from a
stream reach or link to the watershed divide, which in turn is
subdivided into "elevational zones". A watershed of
any size could be represented as coarsely as one segment and one
elevation zone, or as finely as biophysical data and computer
memory allowed. Current work is focused on translating this mainframe
Fortran program into a cross-platform personal computer format
with a convenient graphic user interface. In addition, improved
soil surface temperature algorithms are being experimented with
since surface temperature is a key controller in soil freezing
and thawing and is responsive to canopy coverage. The efforts
to link the model to a Geographic Information System have not
been successful to date but new approaches will be tried.
John D. Fox, Jr.
Estimating Growing Seasons
We started a project using 10-day .62 mile AVHRR satellite
data to develop a growing season map for the circumpolar north
portion of the globe. We will use daily AVHRR data to develop
a growing season map for arctic and subarctic Alaska. The growing
season map will be validated using weather station data, elevation
data, and other satellite data.
Heather Goldman and Dave Verbyla
Tree-ring Evidence of Climatic Warming Stress in Alaska
The radial growth history of white spruce was measured at
Fort Richardson (n = 197 trees) near Anchorage and at five stands
in Bonanza Creek LTER near Fairbanks (n= 68, 70, 40, 38, 50).
All responded to an abrupt change in climate since the late 1970s,
although the response varies according to region, stand history,
and site conditions. The spruce grew more with greater precipitation
in all stands, more with warmer summers at Fort Richardson, and
less during warmer summers and more with cooler summers in the
LTER stands. Radial growth of the Fort Richardson sample was accelerating
in response to warming when a massive bark beetle epidemic, probably
related to climatic warming, caused widespread tree mortality.
In the LTER stands monitored, snow breakage events in 1989 to
1991 triggered bark beetle attacks that occurred as tree growth
was slowing markedly due to warming and drying. A three-year radial
growth reduction from 1993 to 1995 caused by a spruce budworm
outbreak is unique in the 200-year record, supporting the view
that outbreak levels of this insect are caused by recent climate
warming. All other one and two year LTER growth reductions are
clearly correlated with climatic events.
Glenn Juday
Irrigation Changes Spruce Growth
White spruce trees growing on low elevation upland sites in
natural forests of the Tanana Valley produce smaller tree-rings
in warm summers and larger rings in cool summers. This is opposite
from what is generally expected in a cold boreal region. We tested
the hypothesis that supplying moisture would reverse this effect
and produce a pattern of larger ring-widths in warmer summers
for trees under lawn irrigation. We cored and measured tree-rings
collected on the UAF Chancellor's lawn, the Noel Wein Library,
the Fort Wainwright golf course, and a private residence. At the
first two sites, trees were irrigated for their entire lives and
had larger rings in warm summers. At the second two locations,
ring-widths for the samples were compared for at least 20 years
under irrigation and 20 years without irrigation. In nearly all
cases at the second two sites the trees went from smaller rings
in warmer summers during the period of no irrigation to larger
rings in warm summers during the period of irrigation. Nearly
all the effect of greater ring growth in warm summers under irrigation
was found in June alone. These results establish that white spruce
is severely moisture stressed in this part of Alaska. Forest management
treatments that prevent intense competition for water should especially
benefit white spruce stand growth.
Glenn Juday and Samantha Lown
Measuring Plant Productivity
Estimating the amount of plant growth on the earth is important
for earth system science and global change studies. Most of the
estimates of global production have been based on computer models
adjusted by satellite-derived Normalized Difference Vegetation
Index (NDVI) or "greenness" measurements of the difference
in light hitting the earth's surface and the light reflected off
the earth. Investigators are using several years satellite measurements
to identify trends in the year-to-year difference in satellite
readings, making it important to verify the satellite-based computer
model estimates with on-the-ground measurements. A number of non-biological
factors, such as switching among the satellites providing the
readings and time of day the readings are taken, can influence
the results. We used large-scale records of agricultural crop
production and tree-ring measurements of birch and white spruce
over the period 198290 to test model and satellite estimates of
global production. Among the four models tested, the model FASIR
adjusted NDVI readings to produce the most accurate values. The
upward trend of NDVI-based estimates of global plant production
in the model CASA have led some investigators to suggest that
global warming or carbon-dioxide enrichment of the atmosphere
have increased worldwide plant growth. Our results, however, show
that the amount of increase that CASA predicts has not been measured
on the ground. A systematic trend in the NDVI data caused by a
change in the time of day that the satellite readings are taken
must be removed to obtain accurate estimates of global production,
so global warming cannot have produced the amount of effect estimate
by some models.
Glenn Juday, Carolyn Malmstrom, Matthew Thompson, James Randerson,
and Christopher Field
Individual Tree Volume Tables
Accurate individual tree volumes is essentially for property
owners, industry, and research. Sampling of white spruce essential
was completed during 1996. A review of the sample suggests additional
trees from the eastern edge of the state is desirable. Additionally,
there is still a need to sample large trees. One stand scheduled
to be harvested in mid or late 1997 has been identified with trees
greater than 130 feet high, the manager of the land was contacted
and is agreeable to sampling. A regional set of tables for the
Kenai Peninsula is planned for summer 1997. Sampling of tree and
bark measurements for other species continues.
Edmond C. Packee
Forest Productivity
Site index curves for balsam poplar/western black cottonwood
in northern and southcentral Alaska are done. Selecting sample
sites for black spruce is completed; field sampling should be
completed in 1997.
Edmond C. Packee
Forest Products
Export markets (British Columbia, Washington, Oregon, and
Asia) for Alaska round logs have been improving since mid 1996.
New buyers have expressed interest in logs, chips, and some value-added
products. Pulp inventories remained higher than anticipated through
1996, however. The pulp mill at Ketchikan announced its intent
to close in early 1997; this removed a within state value-added
facility that included shipping round logs from the Kenai Peninsula.
The bark beetle epidemic continues to reduce the stumpage values
and end product options for spruce logs. A shortage of hardwood
fiber for pulp is predicted to hit Pacific northwest states within
the next five to 10 years; indicating potential opportunities
for marketing Alaska hardwoods in that region.
Edmond C. Packee
Silvicultural Systems
In Fall 1996, survival and growth of the Tok Levels of Growing
Stock (LOGS) were again assessed. This was the fourth year standard
assessment. Survival for white spruce, black spruce, and tamarack
continues to exceed 90%; for the three species combined, only
one seedling died. This was not the case with lodgepole pine where
more than 60% suffered damage and high mortality; detailed analysis
of the mortality will not be carried out until the 1997 assessment
is complete. The three species survival data analysis was completed
by an NRM student for a B.S. thesis. Because of damage noted in
the Bonanza Creek LOGS study, assessment procedures were changed
to be more inclusive with a full fall assessment. Preliminary
results suggest spruce gall aphid attack is less severe on some
white spruce trees than most other trees. Browsing damage to lateral
buds, occasional terminal buds, and small lateral branches was
noted on many spruce trees. Initially, this was thought to be
due to the spruce grouse, but later observations suggest that
red squirrels are the culprit. As a result of this damage pattern,
internodal distance measurements were begun on all spruce between
the fifth and tenth years.
Edmond C. Packee
Managing Forests for Biodiversity
A major concern in managing for biodiversity is how to define
biodiversity and quantify impacts on it. Disciplines, agencies,
and organizations define biodiversity differently. This creates
confusion among the public as well as land managers. During 1996
and continuing into 1997, regular weekly meetings were held under
the aegis of a non-government organization to try to reach a consensus
on what biodiversity means in Alaska. A basic division exists
as to whether the concept should be ecology based or biota-based.
The ecologic-based definition takes into account both the living
and nonliving components of an ecosystem; whereas, the biota-based
definition emphasizes almost exclusively species richness and
genetic variability and states that these are measures of the
nonliving components. For land management to effectively achieve
stated goals, the ecological definition is essential. In attempting
to measure biodiversity, it is physically impossible to inventory
every species on a site. The concepts of "keystone species,"
a species that is central to maintaining the integrity of the
ecosystem, and "indicator species", a species with such
a narrow ecological tolerance or amplitude that its presence or
absence is a reliable indicator of environmental conditions, are
essential to managing for biodiversity. The bark beetle and the
moose can be considered keystone species because if their populations
are allowed to increase and stay at very high levels, they can
significantly impact forest stand structure, processes, and other
species. The Townsend warbler, solely dependent upon dense white
spruce for nest sites, is an indicator of spruce forest health;
if the spruce are missing, the warbler will be missing as well.
Unfortunately, no one species is a keystone species or an indicator
species.
Edmond C. Packee
Reforestation Stocking Standards
A search of the literature was begun in 1996 to investigate the
effects of initial espacement on growth and yield of Alaskan spruce.
Levels-of-Growing Stock studies (plantations or spacings of natural
stands) were found for white spruce, black spruce, and Sitka spruce.
Survival curves were quite similar. Stems per acre from currently
used white spruce yield tables appear to parallel the espacement
curves. This strongly supports, for white spruce and expands to
black and Sitka spruce, the previous conclusion that currently
accepted initial stocking of 450 tree per acre is too low.
Edmond C. Packee
Forest Health
Northern forest health conditions continue to decline. The
spruce beetle has decimated entire drainages in the Copper River
Basin, including the Klutina and Chitna rivers, and has severely
impacted most of the white spruce forest on the west side of the
Kenai Peninsula including the salmon-rich Kenai River system.
Efforts during the past year emphasized the bark beetles' impact
and has involved participation in three workshops to disseminate
information. We are changing the focus from the beetle to the
impacts of the beetle, sudden and long-term defoliation and mortality
of spruce trees, and the development of approaches to ecosystem
restoration. Presentation and publication of these results are
planned for 1997. During 1996, root decay fungi became more obvious
factors in forest health; efforts were begun to emphasize that
root rot and windthrow had to be separated. Presence of root decay
infection centers must be identified so better regeneration prescriptions
can be made. Conifer root decay centers also provide a stimulus
for mixed species management.
Permanent Sample Plots
An additional 21 sample plots were established in 1996. Three
plots were established in the unthinned portion of the white spruce
seed production area at Tok. All pre-1996 data have been checked
for errors and a clean set of data now exist. During 1996, increased
effort was made to establish sample plots in pure stands and expand
the plot system into the Copper River Valley. Expansion into the
Copper River Valley has been requested by both Native and state
land managers. A grant was awarded to support this expansion over
the next two years.
Edmond C. Packee
A 40 Year Record of White Spruce
The periodic nature of white spruce cone and seed production is
well known in both the literature and forest management experience,
but the factors that trigger these infrequent cone crops is not
well documented. We developed a nearly 40 year record of white
spruce reproduction for the Fairbanks area in Interior Alaska
using overlapping cone and seed production records combined into
a derived index value. The index provides a measure of the availability
of seed for potential natural regeneration. Good to excellent
seed crops occurred up to 12 years apart and a full 28 years separate
the exceptionally large crops of 1958 and 1987. Successive year-to-year
large cone crops years did not occur in this record, although
large crops occurred in 1970 and 1972. We investigated the influence
of precipitation and temperature on critical stages and events
of the 17 to 18 month white spruce reproductive cycle throughout
the long-term seed and cone index record. Climatically initiated
drought stress appears to be an important factor in cone crop
initiation, as indicated by both weather records and radial growth
records. Other subsequent events, such as spring frost, can play
a decisive role in cone and seed crop success or abundance.
Scott Rupp, Glenn Juday, John Zasada, Leslie Viereck, and Phyllis
Adams
Image Processing With GIS
Point, line and polygon themes have been the backbone of most
Geographical Information Systems applications. Images and grids
have only recently been available for use with popular ArcView
and Arc/Info GIS systems. We completed a 12 chapter workbook to
help GIS users who want to learn how to use images from a GIS
perspective. The workbook contains ArcView and ARC/INFO exercises
on image display, 3 D surface display, map scanning, remote sensing,
map projection and datums, image rectification, unsupervised classification,
supervised classification, accuracy assessment, grid operations,
and system tips and tricks.
Dave Verbyla and Karl Chang
A Geographic Forest Ecosystem Dynamics Model Integrated
Within a GIS
Modeling the biology of forest ecosystems has been devoted
to a combination of theoretical and empirical approaches representing
the function of a forest ecosystem generally within an undefined
spatial context. Moving to a large spatial context will require
the use of theoretical representations of critical ecosystem functions
that can be represented on an individual cell basis. It should
then be possible to vary the size of the smallest cell from 10.8
square feet to 247 acres.
A forest ecosystem dynamics model was developed that is based
on the nitrogen productivity concept for forest growth; litter-fall
quality and microbial efficiency for forest floor decomposition.
Climate and ecosystem level disturbances will be handled as restricted
stochastic processes. The restriction will be based on known state
factor relationships. The state factors are used to describe a
broad scale classification of the landscape to define basic limitations
for the randomly derived driving variables used in the model.
The model has been programed as an ARC/INFO AML within the GRID
package. The current version of the model has been verified as
functional from an individual tree basis (10.8 square feet cell
size) in a number of forest types found in Interior Alaska. Verification
on a landscape scale (2.47 acres cell size) is difficult because
of a lack of detailed data that can be used from a landscape perspective.
John Yarie
N Productivity of Alaska Tree Species
The nitrogen productivity (N Productivity) concept represents
one approach for developing algorithms for expansion from the
individual tree to stand or landscape levels of estimating of
primary production across the earth's surface. A simple equation
based on the N Productivity concept can be used to estimate plant
production from the individual tree to stand level geographic
units. Maximum N Productivity equations were developed for balsam
poplar, white birch, and white spruce on an individual tree basis
for the taiga of Interior Alaska. Maximum N Productivity equations
were also developed for aspen, balsam poplar, and white spruce
on a unit area basis in square meters. A single equation for all
species sampled and individual stands was developed on a unit
area basis. The calculated productivity for test stands was in
close agreement to the measured productivity from the landscape
perspective. The set of equations presented can be used for calculation
of taiga forest productivity in a geographic model developed within
a GIS software package in which the landscape unit is an integral
part of the model structure.
John Yarie
[ Agricultural and Forestry Experiment Station | Department of Forest Sciences ]