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Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 ISSN 0392-0534
© Museo Tridentino di Scienze Naturali, Trento 2007
Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project
Jonathan G.A LAGEARD1, Nicola LA PORTA2, Peter A. THOMAS 3 & Neil J. LOADER4
1
Department of Environmental & Geographical Sciences, Manchester Metropolitan University, John Dalton Building,
Chester Street, Manchester M1 5GD, UK
2
Istituto Agrario di San Michele all’Adige, Via E. Mach 1, 38010 San Michele all’Adige (TN), Italy
3
School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK
4
Department of Geography, University of Wales, Swansea SA2 8PP, UK
SUMMARY - Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project- Sampling and analyses
for dendroecological and dendrochemistry studies have been carried out in forests of Trentino, south-eastern Italian
Alps, to complement the extensive speleothem database and recognize tools for cross-correlation of the two archives.
Dendroecological data will be compared with the series of winter temperature and anthropogenic sulphate concentration
trend obtained from three stalagmites sampled at the Grotta di Ernesto cave. The main objective of the investigation
is to analyse different aspects of anthropogenic impacts recorded by the tree-ring series, such as variability in the
load of pollutants and land use changes, and discriminate them from natural phenomena. We also aim at recognizing
ecosystem storage of sulphur, which has been recognised in speleothem studies. Sampling was carried out for trees
growing within 1000 m radius around the cave. We selected trees which had a minimum of 50 and 150 annual rings, a
requirement for both computer assisted dendrochronology and isotope analysis. 85 trees belonging to the species Fagus
sylvatica, Larix decidua, Picea abies and Abies alba were sampled through Pressler coring. Planned analyses included
traditional dendrochronology, dendroclimatology (measuring carbon and oxygen isotopes and blue light reflectance)
and dendrochemistry (extraction of sulphur). The dendroecological data obtained by the study will be compared and
correlated with meteorological series from 5 permanent stations dating back to 1812. The tree-ring data will be also
compared with isotope values extracted from growth annual laminae developed from the year 1900 to the year 2000
AD in stalagmites from Grotta di Ernesto.
RIASSUNTO - Dendroecologia e dendrochimica in Trentino: il progetto Grotta di Ernesto - Un campionamento a
scopi dendroecologici e dendrochimici su anelli di accrescimento annuali degli alberi è stato effettuato in vicinanza
della Grotta di Ernesto (Grigno, TN) per confronto con serie di temperature medie invernali e di concentrazione
di solfato antropogenico ottenute da tre stalagmiti della grotta. Il principale obbiettivo dello studio era analizzare i
diversi aspetti delle trasformazioni antropogeniche registrate nelle serie degli anelli degli alberi dovute a inquinamento
ambientale o cambiamento dell’uso dei suoli, e distinguerle da fattori naturali. Di particolare interesse è riconoscere
fenomeni di immagazzinamento nell’ecosistema di zolfo da emissioni antropogeniche. All’inizio furono identificati
alberi che crescevano entro un raggio di 1000 m dalla Grotta di Ernesto. Tra questi furono selezionate piante con
un minimo di 50 e 150 anelli annuali, richiesti rispettivamente per analisi dendrocronologiche computerizzate e
per analisi isotopiche. Ottantacinque piante appartenenti alle specie Fagus sylvatica, Larix decidua, Picea abies e
Abies alba furono campionate con una Trivella di Pressler. Le analisi programmate includevano dendrocronologia
tradizionale, dendroclimatologia (misurando isotopi di carbonio e ossigeno) e dendrochimica (estrazione di zolfo).
I dati dendroecologici ottenuti in questo studio saranno confrontati con archivi di dati da 5 stazioni meteorologiche
permanenti, poste a diverse distanze dalla grotta. Gli anelli legnosi saranno in futuro confrontati con i valori isotopici
ottenuti dalle lamine di crescita delle stalagmiti della Grotta di Ernesto dal 1900 al 2000.
Key words: dendroecology, dendrochemistry, sulphur, Grotta di Ernesto
Parole chiave: dendroecologia, dendrochimica, zolfo, Grotta di Ernesto102 Lageard et al. Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project
1. AIMS OF THE DENDROECOLOGY for the isotope work envisaged here, as there is an age
STUDIES NEAR GROTTA effect clearly discernable in the isotopic records of
DI ERNESTO SITE tree-rings. A climate signal cannot be found in young
trees and therefore the isotopic records for the first 40
The current palaeoclimate and environmental stud- years growth of individual trees are discounted from
ies, in particular for the past few centuries, require climatic reconstructions. In an ideal world, tree-ring
archives of proxy data with annual to sub-annual records of at least 200 years are desirable for tracing
resolution. In the Trento Province both tree ring and environmental impacts related to changing climate
speleothem proxy records have made substantial new and to industrial development in northern Italy. Field
contribution to our understanding of natural climate sampling took place between 11th and 20th July 2005
variability and the effects of anthropogenic forcing. In from the excellent base of the Albergo San Marco in
particular, the Grotta di Ernesto cave is one of the key Enego and with assistance of the Borgo Valsugana
sites for palaeoclimate and environmental research in Forest District of the Forest Service of Provincia
the Alps (Frisia et al. 2003, 2005). Speleothems from Autonoma of Trento (PAT).
this cave are temperature-sensitive in their growth rate, An exploratory field investigation in 1997 had
and encode in their chemical properties information identified a number of species that might be suitable
about atmospheric sulphur load. The forest trees near for this project: Fagus sylvatica (Beech), Larix decid-
Grotta di Ernesto, therefore, would allow for multi- ua (European Larch), Picea abies (Norway Spruce)
parameter comparison of tree rings and speleothem and Abies alba (Silver Fir). In that pilot study, larch
proxy data at least over the past 150 years, which is seemed to have a good response to temperature. A
the time interval that is better constrained in the an- search was then undertaken for mature/old trees in
nually laminated speleothems (Frisia et al. 2003). In the area above and adjacent to Grotta di Ernesto. As
particular, Frisia et al. (2003) not only found evidence can be seen in figure 1, the entrance to the cave is
for correlation of speleothem growth rate and tem- on the upper slope of Valsugana to the west of the
perature, but also identified the 11-year sunspot cycle, village of Martincelli. Many dendroecological stud-
which was related to ecosystem response to solar forc- ies have shown that the growth response of trees
ing. A dendroclimatological study has the potential located on slopes can often mask meteorological
to cast better insight on the interannual variations of signals (Urbinati et al. 1997; Oberhuber et al. 1998;
climate parameters and how modes of variability have Oberhuber & Kofler 2000; Oberhuber 2004) and
changed through time. It is important, here, to remind therefore another important consideration was to find
that while tree rings are an excellent proxy for the tem- trees rooted on flat or only gently sloping ground.
perature in the growing season, speleothems, at Grotta The circle drawn in figure 1 describes a 1 km radius
di Ernesto, preferentially record the cold season. centred on the entrance to the Grotta di Ernesto and
The present study builds its rationale from the clearly illustrates why the search for suitable trees
premise that tree-ring samples collected from trees focused to the west and south of the cave.
in the vicinity of Grotta di Ernesto could be used to A further restriction on sampling is the extensive
monitor tree response to climatic variables and to area of tree-less pastures. The word “malga” is a com-
anthropogenic pollution over the previous 150 years mon prefix for mountains meaning cattle-shed and can
and provide data complementary to speleothem data. be found in many localities on the plateau within circa
Planned analyses included traditional dendrochronolo- 6 km to the west/north-west of the cave (M. Aveati,
gy, dendroclimatology (measuring carbon and oxygen M. Vacchetta, M. Val Capertadi Sotto, M. Campo di
isotopes and blue light reflectance as climatic proxies) Sopra, M. Val d’Antenne), indicating areas that have
and dendrochemistry (extraction of sulphur). been pasture for some considerable time.
The mixed forests in the area are predominantly
of Picea abies, with Abies alba, Larix decidua and
2. SAMPLING Fagus sylvatica. Mean stand density is typically 250
2
trees per ha and tree basal area is about 25-30 m per
Sampling of tree-rings was governed by a num- ha (Virgilietti 1998). Many stands over the last 40
ber of criteria in order to provide suitable samples years have been managed under a silvicultural system,
for the analyses identified above. Initially, it was “taglio di curazione”, which is similar to “naturalistic”
important to identify trees species growing in the silviculture or a selection system (Ferrari 1984).
area immediately surrounding Grotta di Ernesto, This semi-natural conifer forest with beech under-
which would provide ring series suitable for basic storey is characteristic of this zone of Trentino at 1000-
dendrochronology and, more importantly, ring series 1500 m a.s.l. in the Valsugana (Ferrai & Mazzucchi
of sufficient length to facilitate isotopic analyses. At 1974). Large old beech trees are present scattered in
least 50 annual rings are required for computer-as- some parts of the forest, the remains of seed-producing
sisted dendrochronology, and 150 rings are needed trees that were present in former beech coppices (LossStudi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 103
Fig. 1 - Location of Grotta di Ernesto on the northern, upper
slopes of the Valsugana.
Fig. 1 - Ubicazione della Grotta di Ernesto, verso la sommità Fig. 2 - Open pasture area with evidence of sparse re-
del fianco settentrionale della Valsugana. colonization. The whole plateau was once mostly exploited
as summer grazing pastures.
Fig. 2 - Pascolo aperto con segni di giovane ricolonizzazione
& Ferrai 1984), or some were possibly just isolated da parte della foresta. L’altopiano era un tempo sfruttato
trees in the pasture. These beech growing together principalmente come pascolo estivo.
with larch are mostly found in private forests. Public
forests are dominated by almost solely by Picea ab-
ies and Abies alba. This major distinction in the forest World War. Ruins of trenches are still to be seen and
is the result of the intensive silvicultural management it is not infrequent to find in tree stems with the pres-
that was practiced in the beech coppices and the inten- ence of splinters of bursting shells (G. Messina pers.
sive grazing under larch trees on private lands. There comm.).
are also the remnants of charcoal pits where charcoal Today these areas, formerly kept open due to inten-
was made from beech wood and the waste wood from sive summer grazing (Fig. 2), are still being re-colo-
conifers. nised by the forest, as it is generally the case in many
This forest had been affected quite regularly by mountain regions in the Alps (Piussi & Pettenella
disturbance and significant regeneration occurred 2000). As a result, large areas of the plateau are cov-
only after 1920 (Motta et al. 2002). Before the war ered by forest younger than 100 years (Fig. 3).
the land had been exploited as pasture, as was quite
common in such regions (Backmeroff 1996; Piussi
2002), especially where the slope was not excessive.
A forest management plan from the ’20s (stored in the
Borgo Valsugana Forest District Archives) reveals that
people exerted a large influence on the forest. Forest
management plans for the Grigno area were useful in
the interpretation of the data obtained through earlier
dendroecological research, although events defined
in the tree-rings did not always correspond with data
from the management plans (yearly thinning, felling,
wind-throw damage) as stand-level details were al-
ways missing from the plans. These plans dealt with
areas of several hectares (Motta et al. 1999).
Despite these limitations, the information included
in the management plans is of crucial importance in
studying stand history, and only by using all sources
of information it is possible to delineate and to identify
the most important natural and human features of the
history and disturbance that affected the origin and Fig. 3 - Forest re-colonisation of the plateau near Colle Dei
subsequent growth of the forest stands. Meneghini.
In addition to the culture impacts discussed above, Fig. 3 - Ricolonizzazione forestale dell’altopiano vicino al
the area was also particularly affected by the First Colle dei Meneghini.104 Lageard et al. Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project
Fig. 4 - Location of large larch trees. Sampling a larch using
a Pressler-type increment corer.
Fig. 4 - Ubicazione dei larici con diametro del tronco largo. Fig. 6 - Location of wood piles sampled at 2 km (WP1) and
Campionamento di un larice con un carotiere tipo Pressler 4 km (WP2) from the Grotta di Ernesto.
a incrementi. Fig. 6 - Ubicazione delle cataste di legna campionate a 2 km
(WP1) e 4 km (WP2) dalla Grotta di Ernesto.
Due to topographic restrictions and the generally
youthful nature of the forest, detailed local knowledge
of surviving older trees was essential to the success of
the isotope part of the project.
Foresters from the Forest Service of PAT took the
sampling team to areas where there were large larch
(Fig. 4) and beech trees (Fig. 5). Even the largest larch
trees, such as the one shown in figure 4, were gener-
ally only around 90 years old. Beech trees, such as the
one illustrated in figura 5, were either standing or dead
and fallen, all with central rot making them difficult
to core and even more difficult to measure. Although
there was strong beech regeneration in parts of the area
indicated in figure 5a, there was no scope for bridging
the dendrochronological gap between the living and
dead trees. Fig. 7a - The wood pile WP1. See figure 6 for its geographic
Attention turned to Norway spruce and Silver fir. location.
As with the larch, it proved very difficult to find any Fig. 7a - La catasta di tronchi WP1. Si veda la figura 6 per
la sua localizzazione geografica.
living individuals over 100 years old. The forest-
ers, however, knew of wood piles composed of trees
thought to be old, which had been felled in the winter
Fig. 5 - Location of old beech trees. Sampling a dead Fig. 7b. - Inspecting trunk cross-sections at WP2 to check
beech. for century-old trees.
Fig. 5 - Ubicazione di vecchi faggi. Campionamento di un Fig. 7b - Ispezione delle sezioni trasversali di tronchi nella
faggio morto. catasta WP2 per trovare tronchi centenari.Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 105
of 2004-2005. Two wood piles were inspected, one impossibility of coring some trunks lodged within
less than 2 km from the cave (WP1) and the other 4 the centre of the wood pile. Another drawback was
km (WP2) (Fig. 6). Trees piled at each had not been that bark was sometimes missing from the visible
transported far after felling and the wood piles also portion of the trunk and species identification could
permitted easy viewing of stem cross sections (Fig. only be confirmed later by microscope examination
7a). Quick ring counts helped to identify a number of of the wood structure. In tangential sections, the rays
trees of around 150 years and older. Large diameter of spruce are seen to be comparatively small – 10-
trees were not always the old ones (Cherubini et al. 15 (25) cells high – with included resin canals while
1996; Rozas 2003; Jimenez et al. 2003) so being able the rays of fir are 15-25 (40) cells high without resin
to see the cross-sections saved much trial and error canals.
coring. This sampling advantage was offset by the Increment cores, 5 mm and 12 mm diameter cyl-
inders of wood, were removed using hand-operated
Pressler-type corers (Figs 8a-d and Tab. 1). A few
replicate disks were also removed using a chainsaw
a (Fig. 8e).
c
Fig. 8a - Peter Thomas removing 5 mm and 12 mm cores using
a Pressler-type increment borer at one of the wood piles.
Fig. 8a - Peter Thomas sta campionando con un carotiere
Pressler un tronco in una delle cataste.
b
d
Fig. 8b - Jonathan Lageard coring a conifer in life position.
The most critical part of the coring is hitting the centre of Fig. 8c and d - Peter (8c) begins coring a large trunk from
the tree, which allows to obtain the age of the tree. one of the woodpiles. Jonathan (8d) has reached the centre
Fig. 8b - Jonathan Lageard mentre carota una conifera in of a smaller trunk.
posizione di vita. La parte più critica del campionamento Fig. 8c e d - Peter (8c) inizia a carotare un tronco piuttosto
è centrare l’asse di crescita dell’albero per ottenere l’età largo nella catasta. Jonathan (8d) ha raggiunto il centro di
dell’individuo. un tronco più piccolo.106 Lageard et al. Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project
a
e
b
Fig. 8e - Sampling with a chainsaw to obtain a whole section
of a tree.
Fig. 8e - Campionamento di una rotella di legno con una
sega elettrica per ottenere l’intera rotella di legno.
Fig. 9 - Site chronologies E1_35 from wood pile WP1 and
E1_4 from WP2. a. Raw ring-widths, b. detrended.
Tab. 1 - Increment cores collected in 1997 and 2005. Fig. 9 - Cronologie E1-35 da campioni provenienti dalla
Tab. 1 - Carote campionate nel 1997 e nel 2005. catasta di tronchi WP1 e E1-4 costruita da campioni
provenienti dalla catasta WP2. In (a) i dati grezzi di spessore
degli anelli di accrescimento degli alberi. In (b) I dati dopo
Species No 5 mm cores No 12 mm cores
elaborazione (de-trending).
Fagus sylvatica 5 0
Larix decidua 16 0
Picea abies 23 10
Abies alba 24 5 ly made for trees from both wood piles E1_35 (WP1
– 12 trees) and E1_4 (WP2 – 3 trees) – see details in
figure 9. A comparison of these chronologies with
records from living trees confirmed that the last ring
3. LABORATORY ANALYSES present in both chronologies was laid down in 2004.
Twelve mm diameter samples and disks were
Increment cores were taken to the Dendrochronology kept for isotope analyses and are currently being
Laboratory at Manchester Metropolitan University analysed at the University of Wales in Swansea, in the
(UK), where they were mounted on wooden channels Dendrochronology Laboratory. These cores will also
and sanded using coarse through to fine grit sandpapers be subject to blue light reflectance analysis which acts
to clearly reveal tree-ring wood structure and in par- as a surrogate measurement of ring density, which
ticular the boundaries between rings. Tree ring-width is known to correlate well with climate data. Other
measurements were then made for each sample using a samples are undergoing trials for sulphur extrac-
measuring stage, binocular microscope and specialist tion at the Geography Department of the University
computer software. Measurement started with the in- of Birmingham. A successful application has been
nermost ring (ring closest to the centre of the tree/pith) made to the European Synchrotron Facility (ESRF) in
and followed by a series of consecutive rings towards Grenoble to analyse the molecular state of sulphur via
the bark edge. X-Ray near edge absorption spectroscopy (XANES)
technique at ID 21, which allow to discriminate sul-
phate and sulphide. Other elements will be also ana-
4. INITIAL RESULTS lysed at ID 21 and at very high resolution by means
of micro X-Ray fluorescence spectroscopy within
A ring-width record was made for each core and in- individual tree-rings and we expect to obtain also very
dividual records were crossmatched (that is compared detailed maps. This technique has been commonly ap-
with others for similarity). Using t-value correlations plied to archaeological wood, and will be here applied
it was possible to combine contemporaneous series to for the first time for comparison with speleothem data
form site chronologies. Chronologies were successful- obtained with the same method (Frisia et al. 2005).Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 107
Data produced from all the afore-mentioned analy- Cherubini P., Piussi, P., Schweingruber & F.H., 1996 -
ses will be compared to meteorological data (monthly Spatiotemporal growth dynamics and disturbances in a
and annual means) from meteorological stations listed subalpine spruce forest in the Alps: a dendroecological re-
in table 2 and data obtained from analyses of the spe- construction. Canadian J. Forest Res., 26 (6): 991-1001.
leothems from Grotta di Ernesto. Ferrai S. & Mazzucchi M., 1974 - Improving the forests in
Valsugana: improvement fellings in the coppice stands
and high forest. Monti e Boschi, 25 (6): 11-19.
Tab. 2 - Meteorological data available for comparison with Ferrari L., 1984 - Forests and forestry in Trento Province,
tree-ring data. Italy. Schweizer. Zeit. Forstwesen, 135 (7): 547-612.
Tab. 2 - Dati meteorologici disponibili per il confronto con i Frisia S., Borsato A., Preto N. & McDermott F., 2003 - Late
dati degli anelli degli alberi. Holocene annual growth in three Alpine stalagmites
records the influence of solar activity and the North
Meteorological Station Data coverage (years AD) Atlantic Oscillation on winter climate. Earth Plan. Sci.
Lett., 216: 411-424
Milan 1812-2004 Frisia S., Borsato A., Fairchild I.J. & Susini, J., 2005 -
Trento 1875-2004 Variations in atmospheric sulphate recorded in stalag-
Bieno 1924-2004 mites by synchrotron micro-XRF and XANES analyses.
Lavarone 1921-2004 Earth Plan. Sci. Lett., 235: 729-740.
Jimenez J., Kramer H. & Aguirre O., 2003 - Individual tree
Pieve Tesino 1963-2004
growth in an uneven aged mixed coniferous stand based
on stem analysis. Allgemeine Forst- und Jagdzeitung,
174 (9): 169-175.
5. FUTURE OBJECTIVES Loss A. & Ferrai S., 1984 - Coppice forests in Trentino:
silvicultural and management aspects. Schweizer. Zeit.
Forstwesen, 135 (7): 585-597.
There is an exciting future for sulphur analyses in
Motta R., Nola P. & Piussi P., 1999 - Structure and stand
tree-rings of specimens collected near a site for which
development in three subalpine Norway spruce (Picea
increasing sulphur concentration trends have been de-
abies (L.) Karst.) stands in Paneveggio (Trento, Italy).
tected for the past 100 years from the speleothem archive.
Global Ecol. Biogeog., 8 (6): 455-471.
It is envisaged that ring-width chronologies already built
Motta R., Nola P. & Piussi P., 2002 - Long-term investiga-
will be strengthened and it may also be possible to work
tions in a strict forest reserve in the eastern Italian Alps:
up tree-ring chronologies for larch and for fir. The tree- spatio-temporal origin and development in two multi-
ring team is looking forward to collating the results from layered subalpine stands. J. Ecology, 90 (3): 495-507.
the range of analyses and to drawing conclusions about Oberhuber W., 2004 - Influence of climate on radial growth
past climate in the hinterland of Grotta di Ernesto and of Pinus cembra within the alpine timberline ecotone.
about the links Sulphur forges between natural and hu- Tree Physiol., 24 (3): 291-301.
man modified systems above and below ground. Oberhuber W. & Kofler W., 2000 - Topographic influences
on radial growth of Scots pine (Pinus sylvestris L.) at
small spatial scales. Plant Ecology, 146 (2): 231-240.
ACKNOWLEDGEMENTS Oberhuber W., Stumbock M. & Kofler W., 1998 - Climate
tree-growth relationships of Scots pine stands (Pinus
This work is a part of the project AQUAPAST sylvestris L.) exposed to soil dryness. Trees-Structure
financially supported by the Provincia Autonoma of and Function, 13 (1): 19-27.
Trento. The authors wish to thank Dr. Giorgio Messina Piussi P., 2002 - Spontaneous reforestation and post-agricul-
and several other foresters of the Forest Service of the tural development. Monti e Boschi, 53 (3/4): 31-37.
Provincia Autonoma di Trento for the very helpful as- Piussi P. & Pettenella D., 2000 - Spontaneous afforestation
sistance in finding the trees and in collecting samples, of fallows in Italy. Weber N. (ed.), EFI Proceedings, 35:
and Dr. Silvia Frisia, who coordinated the project and 151-163.
revised the manuscript. Rozas V., 2003 - Tree age estimates in Fagus sylvatica and
We thank the UK NERC for research support (NE/ Quercus robur: testing previous and improved methods.
C511805/1 and NE/B501504/1). Plant Ecology, 167 (2): 193-212
Urbinati C., Carrer M. & Sudiro S., 1997 - Dendroclimatic
response variability of Pinus cembra L. in upper timber-
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