[Show abstract][Hide abstract] ABSTRACT: AimClimate change is expected to modify growth trends of forests around the world. However, this modification may vary in strength and intensity across a species' biogeographical range. Here, we study European populations of silver fir (Abies alba) across its southern distribution limits in Spain, Italy and Romania. We hypothesized that growth trends of silver fir will differ across its distribution range, with a marked decline in growth in drought-prone regions near the species' southernmost biogeographical limits.LocationEurope (Spain, Italy, Romania).Methods
We collected tree-ring data from at least 1300 silver fir trees located in 111 sites. The dataset was used to assess and model growth trends, quantified as changes in basal area increment, and to determine how growth responds to climate.ResultsWe found contrasting patterns of basal area increments among countries and sites. Populations of silver fir located outside the Mediterranean area (e.g. northern Italy, Romania) have shown a clear increase in growth over the last two decades, whereas most populations in Spain and southern Italy have displayed a marked decline in growth since the 1980s. The growth of silver fir forests at the south-western distribution limit is severely constrained by low spring–summer water availability, whereas growth of silver fir forests in non-Mediterranean areas is limited by cold conditions in late winter to early spring.Main conclusionsClimate warming is distinctly modifying growth patterns and responses to climate in silver fir across most of the species' European distribution area. In south-western Europe the reduction in growth of many populations is related to an observed increase in aridity, whereas in more temperate areas warming is enhancing growth. Our results confirm a decline in the growth of silver fir at its south-western distribution limits as a consequence of climate warming.
Journal of Biogeography 04/2015; 42(6). DOI:10.1111/jbi.12512 · 4.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Long-term data on radial increment dynamics in Mediterranean species may identify which climatic variables are the main constraints
for radial growth and at which temporal scales they act. To this end, we examined stem radial fluctuations in Quercus ilex L., the dominant evergreen oak species in the Western Mediterranean Basin, over a period of 11years (1994–2004) at a coastal
site in north-eastern Spain. We used manual band dendrometers to record girth changes in trees on north- and south-facing
slopes. Annual increments measured by dendrometers showed good agreement with annual tree-ring width. North-facing trees showed
a lower long-term cumulative radial increment than south-facing trees. The seasonal radial increment pattern of Q. ilex was bimodal, being characterized by a greater increase in May and a lesser, more variable increase peak in September. Both
phases corresponded to warm and moist climatic conditions, whereas radial increase of stems stopped in winter and occasionally
in summer. Considering the whole year, mean maximum air temperature was the main factor positively affecting radial increment
of Q. ilex from short- (5days) to- long (30days) time scales, whereas the accumulated precipitation exerted a similar effect at longer
(30days) scales, but only on south-facing trees. In summer, all trees were positively correlated with precipitation at long-time
scales (30days); however, only stem increment of south-facing trees showed a significant relation to the temperature at short-time
scales (10days). We confirmed the dominant role of temperature as the major constraint on radial increment at short time
scales, despite most previous studies were mostly biased towards precipitation effects at monthly scales.
KeywordsBand dendrometer–Drought–Mediterranean climate–Bimodal growth–Holm oak
Trees 08/2011; 25(4):637-646. DOI:10.1007/s00468-011-0540-3 · 1.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Wildfires have decimated forests of Pinus nigra in the Mediterranean Basin in recent decades, but little is known about the fire ecology of this native species. We sampled three small relict forest sites on Sierra Turmell, Castellón, Valencia, northeastern Spain, to determine forest structure and past fire events. The forest was characterized by relatively large and old trees (mean 158 year, max 362 year). Fire history was affected by obliteration of some fire scars, but we determined 11 fire dates in the past 172 years. The minimum fire-free interval was 2 years, maximum 57 years. Fire dates were not linked with dry climatic conditions, possibly due to occupational burning by pastoralists. Compared to inventory data averages for P. nigra in northeastern Spain (Catalunya), the old forest at Sierra Turmell supported over twice the basal area and over 2.5 times the biomass, with a comparable advantage in terms of carbon storage. Carbon sequestration, on the other hand, was over six times higher in the younger forests. The relict forest at Sierra Turmell provides evidence of multi-aged forest structure persisting through numerous surface fires over several centuries. This example may be useful for guiding management of younger forests and for ecological restoration of degraded areas.
[Show abstract][Hide abstract] ABSTRACT: The influence of climatic factors on tree-ring width and the formation of double rings was studied in Quercus ilex L. growing in a coppice stand left unmanaged for 22 years. Ten trees were felled and discs were taken every 30 cm from bole and dominant branches. Dendrometer bands were installed on 10 nearby trees and the data recorded were used to confirm the accuracy of our tree-ring identification. They were also used to relate the seasonal radial growth pattern to double-ring formation. Double rings were frequent and occurred consistently along the stem. Two types of double rings could be recognized according to their width: type I, with the extra growth band accounting for approximately 50% of the tree ring; and type II, with a narrow extra growth band. Type I double rings were formed when approximately 1/2 of the growing-season precipitation occurred during the second growth period of the season and after the summer drought. Type II double rings occurred when approximately 1/3 of the precipitation in the growing season occurred after the summer drought. The formation of double rings was triggered by rainfall in summer and the extra growth-band width was related to summer and autumn environmental conditions. Double rings in Q. ilex can potentially be used in dendroclimatological studies, as they are formed in response to climatic conditions within the growing season.
Canadian Journal of Forest Research 10/2007; 37:1915-1923. DOI:10.1139/X07-050 · 1.68 Impact Factor