Project reports
1.
Dating the invasion of bark beetle
2. Impact of peat-bog drainage on tree growth
3. The response of Pinus rotundata tree rings to soil
instability
4. Age structure of a marginal bogpine population
5. Climate and tree rings
6. Dating historical structures
DATING THE INVASION OF BARK BEETLE
Group leaders: Monika Kroupová (Czech Republic), Tomáš
Tichý (Czech Republic)
Members: Alexandra Artz (Germany), Hana Blíziková (Czech
Republic), Daniel Bonk (Germany), Jürgen König (Germany), Jiří Souček (Czech
Republic), Wibke Strate (Germany), Christian Welscher (Germany).
Objective: Dating the invasion of bark beetle using methods
of dendrochronology.
Study area: Mountain plateau Kvildské pláně, Šumava
Mountains.
Vast peat bogs are typical for the area, protected as zone 1 of the
Šumava National Park.The peat bogs are usually surrounded by a spruce monoculture. Strict
regime of protection of the above mentioned zones makes man intervention impossible,
including protective measures against bark beetle (i.e. sanitation of attacked trees).
Site: Bark beetle focus.
Plot of about 0,25 ha of dead standing trees situated in the spruce
monoculture, close to the peat bog of Zhůřská slať. Elevation of the plot - 1 139 m
above sea level. Exposition - flat plain. Trees have died owing to bark beetle infestation
but the year of tree death was unknown.
Material and methods: The bark beetle focus was first mapped
out by a simple method and the plan of the plot drafted. Then the transects defined in N-S
and W-E direction. Along the transects two cores have been taken from each tree. Total of
22 dead standing trees were sampled. The sample trees were mapped out and registered in
the plan. Besides the dead trees the cores were taken also from 10 living healthy trees
close to the plot.
The cores were mounted onto wooden holders. Part of cores was cut
down by razor and measured by KUTSCHENREITER DIGITALPOSITIOMETER. The second part was
sanded and measured using WINDENDRO system. Skeleton plots were recorded for all cores,
both from living and dead trees. Skeleton plots of the living trees were summarized in the
master plot.
The year of tree death was determined by two methods:
1. using ring width measurements - particular chronologies of dead
trees were cross-dated with mean chronology (master chronology) of living trees (see fig.
1),
Fig. 1: Dating using ring width measurements
2. using skeleton plots - particular skeleton plots of dead trees
were compared with master plot of living trees.
Results:
Ring width measurement: The following negative pointer years
were identified during the measurement: 1913, 1948, 1996. Having in mind high
precipitation in the region it can be supposed that the temperature is the limiting factor
of the tree growth, mainly low temperatures during the vegetation period.
Skeleton plot analysis: Pointer years 1912, 1948, 1996 were
identified. Here is a diference between skeleton plot analysis and ring width measurement.
The year 1912 was identified during skeleton plot analysis as a pointer year because of
typical structure of the ring - ring width is normal but whole ring has light colour and
latewood is very narrow.
Dating of the tree death: Besides one tree which was broken
and have died in 1987, all trees along the transects within the plot have died during two
years of bark beetle infestation: 1995 and 1996 (see fig. 2). Then the infestation
stopped. The number of trees attacked during the first year of infestation was similar to
that of the second year. It is interesting that our estimate of the centre of bark beetle
focus corresponds to the real centre.
Fig. 2: Result of the dating of tree death.
Impact of weather on spreading of bark beetle:
Data of close situated meteorological station Churáňov were used to answer
this question. Temperature and precipitation measurements of the years 1955 – 1998 were
at disposal. The season of bark beetles is from March to September when they are the most
active. The sum of precipitation and the average temperature were computed for this season
of each year 1955 - 1998. The mean, minimal and maximal values are listed in the table
Tab. 1 bellow.
Tab. 1: The measurements of meteorological station Churáňov,
1955 – 1998.
| Churáňov 1955 – 1998 (March – September) |
|
Mean |
Min |
Max |
| Average temperature [°C] |
7,5 |
5,2 |
9,6 |
| Sum of precipitation [mm] |
702 |
505 |
1006 |
As mentioned above the analysed trees have died during the years
1995 – 1996. The graph at fig. 3 shows the meteorological conditions of the years 1995
– 1996. Optimal conditions for bark beetles are high temperature and low precipitation,
so this two years were not favourable for them. That is why the year 1994 was added to
this comparison. Average temperature in the season March - September of this year was the
maximal one of whole period 1955 – 1998 and also the sum of precipitation was quite low.
This could have been the reason of the expansion of bark beetle population, which caused
the calamity in next two years.
Fig. 3: Comparison of weather conditions 1994 – 1996
with 1955 - 1998.
Conclusion: Most of dead trees (90%) has been cross-dated
successfully. Both methods of determination of tree death using tree ring width
measurement and skeleton plots are suitable for this purpose. Ring width measurement is
more accurate when it is necessary to distinguish very narrow rings. The main advantages
of skeleton plots are simplicity and fast results. It is possible to use this method
directly in the field during the taking the cores.
We can conclude that the methods of dendrochronology are suitable
for studying of bark beetle infestation, mainly when it is long-term repeated infestation
of vast area, as it is in Šumava Mountains.
IMPACT OF PEAT-BOG DRAINAGE ON TREE
GROWTH
Group leader: John Francuz (Switzerland)
Members: Muriel Bendel
(Switzerland), Wolfgang Bischoffl (Switzerland), Richard Lutzl (Switzerland)
Objectives:
1 - Impact of Peat-Bog drainage on Tree growth
2 - Drainage effect on the radial growth of trees
growing in the transition zone from wetter areas nearer the ditch to the more dryer zones
further from the trench
It was also hoped that the observations, insights and
conclusions gained during the process of answering these questions would also serve as
useful advice to the authorities in aiding future management and conservation policies of
the bog area.
Location and Methods: Our study area was located
in the south-easterly region of the Mala niva Bog. There, in the lag zone, we found a
series of man-made ditches each of about 1m. wide and 50 cm in depth (See photo). We
selected an area running approximately 80 metres in length along one of the ditches and up
to 15 metres, mainly, on one side of the ditch. A total of 26 Trees were sampled
consisting of 14 Picea abies ( Spruce) and 12 Pinus sylvestris (Scots Pine). These were
taken from various intervals along the sides of the drainage ditch (0 metres) and at
distances of 1, 5, 10 and 15 metres away from the ditch (see Fig 1). The height and girth
(breast height) was recorded for each tree. Two 5 mm cores were taken at breast height:
One extracted from the ditch-facing side of the tree and the other from the side facing
away from the ditch. The cores were then mounted onto wooden holders and sanded to expose
the growth-rings. These were carefully checked for event years which were subsequently
plotted onto skeletal plots. Each group of plots were then averaged onto one Master Plot.
Thus allowing five master plots for comparison at 0,1,5,10,and 15 metres from th ditch.
(Fig. 2).
Observations: From the master plot a clear abrupt increase in
growth from the year 1943 is seen on trees growing directly at the ditch (0 metres). The
other plots, from trees growing at distances up to 10 metres from the trench, reacted one
year later. Trees sampled from approximately 15 or more metres away do not show any clear
growth changes. About 9-15 years after the 1943 increases gradual decreases in growth are
to be observed, the narrowest rings being recorded at around 1965-1973. From 1974 onwards
growth increases are again to be observed.
Discussion: The strongest reaction to the drainage made in
1943 show in those trees that were growing nearest to the ditch: They show a sudden
increase in growth which can be seen as very wide tree-rings compared to the narrow ones
before the drainage. This is due to the lower water-table, allowing more air to the roots
and an increase in nitrogen availability. After about 10 more years a slow decrease in
growth can be observed. Different explanation are possible for this:
- The ditches were not cleaned, therefore a natural refilling took
place. As a consequence the water-table became higher once again, less nitrogen became
available and, because of these worsening conditions, the tree-rings got narrower.
- Competition between the trees began to get stronger because of the
increased growth; the closing of the canopy and the resulting decrease of light
availability to the lower regions below may have become a limiting factor. In our research
plot hardly any regeneration was to be observed. Because of light availability the
shrub-layer was too dense for allowing successful growth of seedlings.
- After a certain period of time the peat quality changes and
becomes more dense. This makes it less favourable for the trees to grow.
From the year 1974 we found another increase in growth, especially
in trees next to the ditch. This could be due to the cleaning of the trench.
Peat-bogs were often regarded as wasted land and drainage channels
were constructedto increase tree-growth: This method allowed more wood to be harvested
within a certain time. During World War I and II large quantities of wood were especially
needed. In this context our dating of 1943 for the construction of the drainage trenches
makes sense.
Each and every peat-bog is different and reacts individually to
disturbances. In our research-plot the reaction to the drainage trench could only be seen
on ring-width growth in trees up to a distance of 10 metres from the trench. However, in
other peat-bogs trees at a distance of 150 metres have still been seen to be affected.
Conclusions:These results indicate that the consequences of
the drainage are faster growth of the Stand, which, as the canopy increases, allows less
light to filter down to the lower ground vegetation. This latter situation causes an
increase in Vaccinum but an inhibition of germination and regeneration of tree-species. It
would seem that regeneration may only be possible when a tree dies, thus allowing more
light into an area for germination to take place. We conclude that the result of drainage
would most likely cause the development of a homogenetic forest, that is, a forest with
similar species of approximately the same age, having a cyclic dynamics.
An alternative would be to allow nature to govern the situation. The
drainage ditches could be filled in with peat, thus restoring the area to its original
condition. In time, this may allow a more heterogenous stand to develop, both in species
and age. However, before this latter proposal would be undertaken it is recommended that
more information, e.g., concerning density, water capacity etc., of the peat layer should
be researched.
THE RESPONSE OF PINUS ROTUNDATA
TREE RINGS TO SOIL INSTABILITY
Group leader: Jaroslav
Dobrý (Czech Republic)
Members: Ivo Moravec (Czech Republic), Cressida
Whitton (United Kingdom)
Objective: To determine events and
periods of anomalous growth in diameter indicating the impact of unstable peat-bog soil
upon tree growth.
Study site:
South-east
corner of Malá Niva (“Small Floodplain”) peat bog near Soumarský most, Šumava
National Park, South Bohemia. Protected natural reserve of the 1st category.
Peat depth: 1-1.5 meter.
Study species: Pinus rotundata - tree species adapted to the growth on
deeper peat bog.
Methods: Increment cores were extracted from leaning trees. Cores were taken
at the side of pressure and at the opposite side of a stem. After extracting, the cores
were attached to wooden supports and coded (e.g., SN1011 = Small Niva, Sub-site #1, tree
#01, core #1). The orientation of the cored tree and of the trees growing around was
noted, and a sketch of the shape of the tree (trees) was made. After drying up at the
supports, the cores were glued and sanded. Cross-dating of tree rings was done under a
binocular microscope. The method of skeleton plots was used. Event years and periods of
abrupt growth changes with or without reaction wood were indicated in diagrams.
Results: The response of wood structure at the
opposite side of pressure (lean) was typical of coniferous trees. The reaction wood
strengthened the side that was being stressed. This way the events causing leaning of
trees and periods of stress could accurately be dated.
Case #1 - single trees: Leaned trees, not supported by
other trees, showed when the loss of balance occurred and the period of stress (mostly up
to present).
Case #2 - groups of trees: In this more complicated case,
we were able to determine series of successive events. For example, episodes of
compression wood formed due to the leaning of a tree, or pushing by other tree, the
stabilization of a tree by “hung up”, etc.
Conclusion: Tree rings of Pinus rotundata
proved to be a good indicator of soil instability at peat-bog soil. The events and periods
of growth disturbances could easily be dated, and this way stand structure dynamics of the
bog pine could be studied.
AGE STRUCTURE OF MARGINAL BOGPINE
POPULATION
Group leader: Jan Jenik
(Czech Republic)
Members: Jitka
Dvorska (Czech Republic), Stan Schymanski (Germany), Pascal v. Sengbusch (Germany)
Objectives:
1. What is the pattern of regeneration? Continuous or wavelike
pine recruitment?
2. Is the correlation of height and circumference
linear?
3. Does a homogenous height of a stand reflect a
homogenous age structure?
4. Is the average treeringwidth of the oldest trees
influenced by the drainage?
Study site: All investigations were carried out in the Mala Niva-Peatbog (Soumarsky
Most, ~ 5 km west of Volary), Sumava Mountains
Study species: Pinus rotundata - tree species
adapted to the growth on deeper peat bog.
Description of vegetation structure: The marginal
bogpine stand has a tree canopy with an obviously high diversity of height and a scattered
occurrence of dead and oblique trees. In the plots the field layer has a cover of dwarf
shrubs (Vaccinium uliginosum, V. myrtillus) of app. 30 - 40 % with prevailing Eriophorum
vaginatum. The percentage of Sphagnum spec. in the moss layer is 50-60%.
Methods & study design:
A. Three plots were chosen in a marginal bogpine
stand in close vicinity to the spruce belt.
In each plot a tree was defined as plot centre and the
surrounding 10 trees were chosen to be examined. Two cores were taken from each tree, the
age of pine shrubs was estimated by the number of whirls and bud scars.
The following parameters were recorded from each tree:
- Height of the tree
- Circumference of the trunk
- Distance of the tree from the plot centre
- Angle of tree / plot centre in relation to North
B. Three
plots were chosen along a transect from the lagg towards the centre of the bog. 10 cores
were taken in each plot and the height and circumference were recorded.
Results "Age Structure":The data were
depicted in age classes of 0-21, 21-40, 41-50,....All plots show a predominance of younger
trees with an age below 60 years. The older age classes are represented just by a few
trees with an age of 120 - 309 years. This may reflect a continuous pattern of
regeneration in the marginal zone since 1930. In the drained bogs in the Black Forest, in
contrast, the older age classes are prevailing.
Results "Circumference / Height": Up to a
height of 8 m a linear correlation of circumference and height is likely (R2=0,90).
Beyond a circumference of 50 cm there is only a moderate increase in height. Thus, the
whole data set can be characterised by a logarithmic correlation (R2=0,90). In
respect of the latter, we suggest that a tree-layer, homogenous in height, may not reflect
a homogeneous age structure.
Results "Bog Transect": The age structure
of the central plot does not correspond to what it is supposed to be. According to Robert
Neuhäusl's suggestion (Neuhäusl 19 ), a loose, original stand of bogpine should be
characterised by a heterogeneous age structure (cyclic succession) with all age classes
being represented. In contrast to this, the oldest trees reach no more than 80 years. This
may be due to the small sample of 10 trees.
The lagg shows only sparse regeneration, which may be due
to the dense tree and shrub layer.
Results "Average Treeringwidths": The
average treeringwidths of the 12 oldest Pinus rotundata stems show an increase from
1943 until the late 50ies.
Conclusion: In view of the existence of old drainage
ditches, the marginal pine stands have a surprisingly loose tree canopy. The ecological
conditions have obviously been favorable for pine recruitement since 1930, which is
exactly the period of the drainage of the bog. The sparse shrub layer and the high
percentage of Eriophorum vaginatum and Sphagnum nemoreum agg. can be interpreted as
indicators for a watertable being not too far below the surface. Thus, we drew the
conclusion, that there was only a slight impact of the drainage on the hydrology of the
investigated stand. A transient improvement of oxygen and nitrogen supply
CLIMATE AND TREE RINGS
Group leaders: Vanessa Winchester
(United Kingdom), Bob Lofgren (USA)
Members: Iouri Djanseitov (Russia), Eliane
Jäggi (Switzerland), Elzbieta Kuchnicka (Poland), Marcela Mácová (Czech
Republic), Baatarbileg Nachin (Mongolia), Julia Savva (Russia), Pavla Štěpánková
(Czech Republic), Adomas Vitas (Lithuania), Matthias Zesiger (Switzerland).
Objective: To investigate whether tree rings
could be used to date climatic events in the forests around Babůrek in the Šumava
mountains, Czech Republic (near Vimperk at 490 02'N 130 47'E). The
problem was to separate the climatic influences from the environmental and genetic ones
since these latter factors can obscure the climatic responses of individual tree rings.
Introduction: The growth of tree rings reflects both
seasonal variations in precipitation and temperature as well as environmental influences
including: site exposure, wind, snow, soil type, ground cover, light availability,
competitive influences and forest management. In addition, the genetically controlled
adaptive potential of individual trees also varies and affects ring growth. The goal of
the study was
Study area: The forests around Babůrek, growing
between 800-1300 m above sea level, were formerly of beech and mountain ash, but are now
dominated by spruce, with some fir, larch, and regeneration of beech and oak. The annual
average temperature, according to the records from the local meteorological station at
Churanov, is between 3.5-50 C and total annual precipitation varies from
1,000-1,200 mm.
Field methods: Three areas were investigated:
On Day 1 the group divided and one half went to HRB (Site 1), a high point at 1,070
m, 1 km northeast of Babůrek where the spruce forest cover is broken by rocky outcrops;
the other half of the group went to a poorly drained valley 1 km south of Babůrek at 850
m (Site 2), where the forest margin, flanked by a bog and open fields, initially
runs north-south then curves westwards across a small stream. These two sites were
selected in an attempt to separate tree growth response to precipitation from that of
temperature. At Site 1 it was assumed that growth would be equally affected by both
factors whereas Site 2, facing a southerly slope and backed by forest, could provide a
hollow where sinking cold air would be ‘ponded’ and form a frost pocket in the colder
winter months with growth here thus showing greater sensitivity to temperature.
On Day 2 the whole group (accompanied by Mr Chaoying Liao)
walked 5 km southwest from Babůrek to Přilba at 1,219 m (Site 3). The group
divided into four sub-groups and cored down slope along transects running north,
northeast, southeast and south. The north and south transects were almost exclusively of
spruce while there was some oak regeneration to the southeast and beech and mountain ash
regeneration in the northeast transect.
We collected a total of 80 cores from the three sites,
usually 2 from each tree, from the largest (mostly straight) undamaged spruce trunks in
each study area. At Site 2 (on Day 1) a selection of different sized trees were cored on
the forest margin and in open positions. Field notes were made of each individual tree’s
growing characteristics and environmental conditions: core identification number, site
position, tree species, tree height, core height, trunk circumference, average distance to
nearest 4 trees, canopy contact with neighbouring trees, slope angle, aspect, soil type,
surrounding vegetation species, and percent cover, and any other factors peculiar to the
tree. The cores were glued, sanded and dated.
Analytical methods: Analysis of the data was carried
out on two levels: all the cores were examined using a ‘low technology’ approach based
on skeleton plots aimed at dating extreme climatic events and a ‘high technology’
approach based on computer digitised ring-width measurements and meteorological data was
used in a detailed examination of 10 selected cores from HRB and PŘILBA . In addition,
data from bent trunks were examined to show how environmental signals can obscure climatic
signals.
Skeleton plots were constructed for trees at the three
sites recording only the most marked ‘event years’ where individual rings were
exceptionally narrow or wide or showed very faint or very dark latewood growth. A single
Masterplot showing pointer years was derived from the three Site skeleton plots.
Using the ‘Cofecha’ and ‘Arstan’ programmes, cores
were crossdated and graphs produced showing standard chronologies running from 1883-1998
for HRB, and from 1841-1998 for PŘILBA. Detrending was applied to the two graphs to
eliminate ring width changes due to increases in trunk circumference. Climate data from
Churáňov was collated with ring-width measurements and climate and ring-width data were
then combined to derive a response function for growth in relation to temperature and
precipitation for the previous and current years.
Results: The Site skeleton plots from
Sites1 and 2 show eighteen and four event years respectively; from Site 3 nine event
years. The Masterplot for all three sites show 25 pointer years with the strongest
positive signals for 1933 and 1998 and the strongest negative signals given for 1948, 1976
and 1996 (Figure 1). HRB and PŘILBA show opposite growth reactions in 1997. Ring-width
measurements taken from bent and damaged trunks showed no correlation with climate.
The standard detrended chronologies for HRB and PŘILBA
agree over maximal growth in 1928, 1963, 1989 and 1998 and minimal growth in:1948,1976 and
1996 (Figure 2). The response function graph shows generally weak correlation coefficients
(less than 0.2 and -0.2) between growth, temperature and precipitation, with the exception
at HRB where the correlation coefficient for temperature in March of the current year was
0.3. At PŘILBA there was a coefficient of -0.35 in November of the previous year (Figure
3).
Conclusions: Both skeleton plot and computerised
approaches showed an encouraging agreement on tree-ring growth around Babůrek over their
dating of the extremely cold event years of 1948, 1976, and 1996; agreement on positive,
warm (wet?) years was limited to 1963 and 1998. The skeleton plot approach also showed a
generally low period of growth between 1975 - 1979. However, using the software programmes
there was only time to process 10 cores and this limitation is likely to have affected the
‘high tech.’ results.
The investigation of the growth response function suggested
that the decision to core trees at the low elevation site in a ‘frost hollow’ was
justified, since tree growth in this area was shown to be sensitive to low temperatures in
November of the preceding year. However, the abundance of water at the site resulted in
generally complacent ring growth and consequently the low number of extreme events shown
by the cores at that site.
None of the cored trees on the three sites was affected by
wind or snow. In addition, the sampling strategy showed that, when climate data is
required, coring should be carried out on trees having straight, undamaged trunks. The
study effectively showed that large numbers of cores can be quickly and accurately
processed using the relatively subjective skeleton plot method.
Methodological recommendations arising from the work are:
that the most rewarding sites for temperate climate studies where environments are
unstressed are likely to be those with cold, dry conditions, and that tree sampling should
be restricted to straight trunks of healthy, undamaged trees.
The overall conclusion as regards the study’s main goal
of ‘whether tree rings can be used to date climatic events in the forests around
Babůrek’ is that only the most extreme weather years can, unambiguously, be
distinguished from the environmental background ‘noise’ affecting the growth of
individual trees and forest stands.
DATING HISTORICAL BUILDINGS
Group leader: Tomáš Kyncl (Czech
Republic)
Members: Jaromír Beneš (Czech Republic),
Peter Hoare (United Kingdom), Liao Chaoying (China), Nicolien Mac Gillavry (The
Netherlands), Donald McGraw (USA), Hanuš Vavrčík (Czech Republic)
Objective: To date three examples of historical wooden
construction in Šumava region. We chose the most important buildings in the close
environs of chalet Baburek:
- roof-frame of St. Jacob’s church in Prachatice
- roof-frame of Vlček’s tower in Vimperk castle
- wooden house in Stachy
Material: Altogether 19 samples were taken from roof frame of
St. Jacob’s church - 11 from the nave roof and 8 from the presbytery roof. Only elements
with presence of assembly marks were sampled. All timbers sampled in the nave roof were
spruce, the presbytery roof frames were constructed from fir. From the Vlček’s tower in
the Vimperk castle only 6 samples were taken and all of them were spruce. Six timbers from
walls construction were sampled in wooden house in Stachy (5 spruce and 1 fir).
Methods: The samples were collected with increment borer.
Each core was stick on wooden mounts and sanded with gradual grid of sand paper. The ring
width were measured with accuracy of 0,01 mm. Each ring-width curve was plotted on
transparent paper and crossdated visually. The crossdating was checked later using Cofecha
program and average floating site chronology was produced. Each floating chronologies were
matched against master chronologies and absolutely dated.
Results and Conclusions:
St Jakub’s church
The site chronology compiled from eight of 19 series, when compared
against the regional master chronology (Fig.1), suggests that the cutting of roof timbers
occurred in 1509. Since it is very likely that these timbers were used ‘green’, it is
probable that they were employed within a few years of this suggested felling date. Our
conclusions fit well with (1) the historical evidence of “the big fire" of 1507,
(2) the earlier assumption based upon architecture that the structure is typical of Late
Gothic/Early Renaissance craftsmanship and (3) the known completion of reconstruction
dating to 1516.
Fig. 1: Comparing the average site chronology of St. Jacob’ s church
in Prachatice with the master fir chronology for South of Bohemia.
The Stachy House
Our evidence from the timbers used in the construction of the Stachy
house suggests that they were felled in 1820. They may have been used shortly thereafter.
Such a precise date is useful since (1) the style of architecture spans a lengthy period
from about 1500 to the 19th century and (2) the date of construction of such vernacular
houses is rarely mentioned in historical documents.
The Vlček’s tower in the Vimperk castle
The site chronology produced from 3 samples was matched against the
spruce master chronology (Fig. 2). The bark rings of all timbers were dated to the same
year - 1857. This results did not confirm the expectation, that roof frame survive the
fire in 1854 and is of medieval origin.
Fig. 2: Synchronization of Vlček’ s tower spruce chronology with the
master spruce chronology.
The End