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| Titel |
Influence of plant community structure on vulnerability to drought of semiarid pine woodlands. |
| VerfasserIn |
Cristina Moreno-Gutierrez, Giovanna Battipaglia, Paolo Cherubini, Matthias Saurer, Rolf Siegwolf, Jose Ignacio Querejeta |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042081
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| Zusammenfassung |
| The growth, water status and water use efficiency of trees are sensitive to drought. The
severity of drought experienced by trees can be magnified or diminished depending on plant
community structure and density. This is especially important in semiarid environments. In
dense afforested plantations, high inter-tree competition for soil water could increase the
water stress of trees in comparison to plants in an open woodland. On the other hand, the
shading effect of the tree canopy and the increased soil infiltration capacity in semiarid
afforested stands could prevail over competition and buffer the drought effect. Thus, in dense
afforested plantations, greater inter-tree competition but more favourable microclimatic
conditions may have opposite effects, and the prevalence of one of them could depend on
annual meteorological conditions.
To test these hypotheses, we made a long term assessment (50 years) of tree ring growth
and isotopic composition of Pinus halepensis in two nearby communities: an afforested pine
stand and an open pine woodland with under storey (shrub land), both located in semiarid SE
Spain (Murcia). We sampled 10 trees per site and we measured tree ring width. The
individual time series were detrended and the mean chronology was calculated for
each series. On selected five trees per location, the annual δ13C and δ18O were
measured on cellulose extracted from latewood. The relationships between measured
variables and meteorological (temperature and precipitation) data, provided by the
Spanish Agency of Meteorology, were statistically assessed with linear regression
analyses.
We found a strong significant correlation between the standardized mean chronologies of
pines in both communities. In both sites, the mean sensitivity of the mean chronologies was
high: 0.37 in the open pine woodland (ow) and 0.54 in the afforested stand (as), suggesting
that the individual growth series have a clear common signal. Our results show significant
positive correlations between mean chronologies and total annual precipitation (Pearson’s r =
0.52 in ow; r = 0.51 in as), total monthly precipitation in March (r = 0.40 in ow; r=
0.40 in as) and in May (r = 0.39 in ow; r= 0.31 in as), precipitation in the current
summer (r= 0.30 in ow; r = 0.36 in as) and the total amount of precipitation from
October of the previous year to April of current year (r= 0.61 in ow; r= 0.63 in as).
Precipitation seems to be the driving factor influencing growth of pines in this semiarid
environment.
When comparing the standardized mean chronologies of both communities we observe
greater growth of pines in the open pine woodland than in the afforestated stand. However, in
rainy years, pines in the afforested stand experienced relatively greater increment in
growth. Inter-tree competition for soil water seems to limit tree radial growth in
semiarid pine plantations, but the beneficial effect of more mesic microclimatic
conditions appear to prevail in more favourable years. Defoliating insect outbreaks in the
dense pine plantation could also be partly responsible for reduced radial growth of
trees.
Measurement of carbon and oxygen stable isotope composition of latewood cellulose
could provide insight into the physiological responses of trees to changes in water stress. |
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