Tree-ring study sites: ecology
Dendroecological studies, in which tree-ring
analyses are applied to ecological questions, have been an integral part of the
tree-ring research at WSL since the early 1970s. Such studies deal with the
assessment of a wide range of changes in the local environment, as reflected in
different tree-ring and wood-anatomical parameters.
These parameters, often
available from intra-annual to Holocene-long time-scales, enable the
reconstruction of ecological processes such as defoliation by insect outbreaks;
the effects of air, water, and soil pollution on tree growth and forest health;
the age, maturity, and successional status of forest stands; and the effects of
human disturbances and management on forest vitality.
The Dendroecology Group at WSL uses annually resolved
and absolutely dated dendrochronological and wood anatomical information to
reconstruct environmental conditions over different spatiotemporal scales. We
perform cutting-edge tree-ring research at the interface of archaeology,
climatology and ecology, and suggest expanding dendroecology beyond existing
Our timely dendrochronological and wood anatomical investigations,
centered on the emerging interdisciplinary Global Change arena, also consider
non-forested Arctic and alpine vegetation. In this regard, the team develops,
archives and analyzes globally distributed, high-resolution tree-ring datasets
that may range from intra-annual to Holocene-long time scales and cover a
variety of spatial domains.
In summary, we aim to better understand how the Earth's climate system
changed and still changes and how terrestrial ecosystems were and are responding
to such changes on various spatial and temporal scales.
following examples of dendroecological frontiers emphasize the interdisciplinary
character of our investigations.
Life at the frontier
A small (<5 cm high) Rhododendron lapponicum plant from
coastal Eastern Greenland around 71°N that contains ~240 annual rings and
contradicts the life-form paradigm. In fact, age and size are not necessarily
Schweingruber FH, Hellmann L, Tegel, W, Braun S, Nievergelt D, Büntgen U (2013) Evaluating the wood
anatomical and dendroecological potential of Arctic dwarf shrubs. IAWA Journal 34: 485-497. doi:10.1163/22941932-00000039
Reconstructing insect outbreaks
A high-resolution thin-section
from a historical larch (Larix decidua)
timber sampled in the Swiss subalpine Lötschental.
The extremely narrow ring
that consists of only one earlywood and two latewood cell rows was caused by a
severe defoliation event due to a mass outbreak of the larch bud moth (Zeiraphera
Esper J, Büntgen U, Frank DC,
Nievergelt D, Liebhold A (2007) 1200 years of regular outbreaks in alpine
insects. Proceedings of the Royal Society
B 274: 671-679. doi:10.1098/rspb.2006.0191
Illuminating the mysterious world of truffles
Click on picture to enlarge
Breaking new ground at the interface of
dendroecology and mycology:
(a) An excavation of a natural truffle (Tuber aestivum) site in southwest
(b) a nearby radius dendrometer (Ecomatik DR) measuring radial stem
growth of a possible truffle host (Fagus
sylvatica) at hourly resolution, and
(c) a microscopically magnified image
of a Tuber aestivum peridium
(surface) with mycelium extensions.
New insight on the mycorrhizal fungus-host association, expected to
emerge from combining dendrochronology and mycology, may help
disentangling biotic, abiotic and combined edaphic factors of the
mutualistic relationship between thousands of ectomycorrhizal fungi and
their perennial partners.
Büntgen U, Egli S, Tegel
W, Stobbe U, Sproll L, Elburg R, Peter M, Nievergelt D, Cherubini P, Stenseth
NC (2012) Illuminating the mysterious world of truffles. Frontiers in Ecology and the Environment 10: 462-463. doi:10.1890/12.WB.021
Intra-annual profiles of anatomical traits
Click on picture to enlarge
In the top picture of an exemplary cross-section of a tree-ring of Pinus sylvestris (Scots pine),
yellow tracheid lumina are displayed after semi-automatic quantification of xylem
anatomy using the specialized tool ROXAS. The corresponding changes in
tracheid lumen area and tracheid cell-wall thickness within an annual ring as
measured with ROXAS are shown at the bottom.
Such intra-annual profiles of
anatomical traits show the influence of environmental conditions on tree-ring
formation throughout the whole growing season. The analysis of time series of
intra-annual profiles help to establish cause-effect relationships between the
environment and tree growth. Ultimately, this improves our mechanistic
understanding of tree structure-function responses to environmental variability
von Arx G, Carrer M (2014) ROXAS - a new tool to build centuries-long
tracheid-lumen chronologies in conifers. Dendrochronologia doi:10.1016/j.dendro.2013.12.001
temperatures benefits Alpine ibex vitality
of climate change on trophic interactions and subsequent disruptions of
seasonal synchrony, together with warming-induced alternations of body size and
fitness are particularly severe in Arctic and Alpine ecosystems. Unraveling
biotic from abiotic drivers, however, remains challenging because
high-resolution animal population data are often limited in space and time.
We showed that year-to-year variation in annual horn growth (an indirect
proxy for individual fitness) of 8,043 Alpine male ibexes (Capra ibex)
is spatially well synchronized among eight disjunct colonies living in different
regions and altitudes in the eastern Swiss Alps.
Increasing March-May temperatures, controlling Alpine snowcover, plant
phenology and subsequent ibex resource consumption, not only fuelled annual
horn growth but also enhanced general body size over the past four decades.
results reveal strong dependency of local trophic interactions on large-scale
climate dynamics, and provide insight on rapid phenotypic plasticity.
Büntgen U, Liebhold A, Jenny H, Mysterud A,
Egli S, Nievergelt D, Stenseth NC, Bollmann K (2013) European springtime
temperature synchronises ibex horn growth across the eastern Swiss Alps. Ecology
Neolithic wooden well
Example of early Neolithic
craftsmanship from a well construction in Germany dating around 7200 years
before present. The picture shows timber bearing tool marks on the surface, a cogging
joint, i.e., the base frame with wedged tusk tenon joint with an interlocked
Tegel W, Hakelberg D, Elbrug R, Stäuble H, Büntgen U (2012) Early Neolithic water wells reveal the world’s
oldest wood architecture. PLoSONE
7(12): e51374. doi:10.1371/journal.pone.0051374