Fingerprints of extreme climate events in Pinus sylvestris tree rings from Bulgaria

Tree-ring studies may help better understand climate variability and extreme climate event frequency and are especially useful in regions where detailed meteorological records lack. We studied the effect of droughts and unusually cold periods on Pinus sylvestris tree-ring width and wood anatomy. Study sites were selected along an altitudinal gradient on Vitosha Mountain, Bulgaria. Drought conditions caused the formation of narrow tree rings or light rings if the drought occurred in July-August at the lower altitude sites. In years with droughts in June and the first half of July, followed by precipitation in the middle of July, intra-annual density fluctuations (IADFs) were formed. Trees in the zone with optimal growth conditions produced fewer light rings and narrow rings in years with either strongest droughts or unusually cold summers. At the timberline zone, low summer temperature triggered narrow tree rings and light rings. Frost rings were formed when there was a drop in temperatures below the freezing point in the second half of May or at the beginning of June. Our findings show that studies of tree-ring anatomy may contribute to obtain further knowledge about extreme climatic events in the Balkan Peninsula and in other regions where meteorological data lac

Fingerprints of extreme climate events in Pinus sylvestris tree rings from Bulgaria Panayotov, Zafirov, Cherubini

ISSN:0931-1890ISSN:1432-228

Dendroclimatic analysis of Pinus peuce Griseb. at subalpine and treeline locations in Pirin Mountains, Bulgaria

Tree rings are a natural archive containing valuable information about environmental changes. Among the most sensitive ecosystems to such changes are high-mountain forests. Tree-ring series from such locations are exceptionally valuable both for climate reconstructions and for studying the effects of climate changes on forest ecosystems. The objective of our study is to present new long tree-ring width chronologies of Pinus peuce Griseb. from several locations at Pirin Mountains in southwestern Bulgaria, to explore their correlation with monthly temperatures and precipitation in the research area and to assess their potential for climate reconstruction. We built three long-term index chronologies for the radial increment of P. peuce from treeline locations in the study region. The longest chronology spans 675 years. We studied the impact of monthly air temperature and precipitation on its growth for the past 86 years using multiple regression analysis. Our analysis shows that P. peuce growth is positively influenced by high temperatures at the end of the previous growing season, especially at the two sites in Banderitsa valley until the middle of the 1970s, and negatively affected by cold winters. In some of the sample plots its growth was also positively correlated with high summer temperatures. However, even at these high altitudes in some of the locations on steep slopes P. peuce showed signs of negative impact of drought during the hottest summer months (especially in August). Our chronologies contribute to the paleoclimatic record for southwestern Bulgaria, which could provide baseline information about past climate variability and improve our understanding of current and future environmental changes.24 month embargo; published online: 24 April 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Biotic factors damaging forest stands in Gornata Koria and Chuprene Reserves in Western Balkan Range, Bulgaria

AbstractAssessment and monitoring of health status in deteriorated forest stands in Gornata Koria and Chuprene Reserves in Western Balkan Range (Bulgaria) were conducted in 2017. An integrated approach (based on remote sensing technologies and terrestrial validation) was applied. A series of subsequent terrain observations were carried out in both protected areas mainly in dead or in poor health status stands. As a result, sixteen insect species were identified in Gornata Koria and nine pests in Chuprene Reserves. The predominant number of pests included bark beetles and weevils (Curculionidae), longhorn beetles (Cerambycidae), etc. Attacks caused by the European bark beetle (Ips typographus) formed the main disturbance in the Norway spruce forests in both reserves. Ten parasitic and ten saprophytic fungi were identified in the stands of the Norway spruce (Picea abies), silver fir (Abies alba) and European beech (Fagus sylvatica). Among the parasitic fungi, six species were identified as destructive (Armillaria sp., Heterobasidion annosum, Fomitopsis pinicola, Fomes fomentarius, Ramaria flava and Pholiota squarrosa)

A synthesis of radial growth patterns preceding tree mortality

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A synthesis of radial growth patterns preceding tree mortality

Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1–100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks

A synthesis of radial growth patterns preceding tree mortality

Altres ajuts: this study generated from the COST Action STReESS (FP1106) financially supported by the EU Framework Programme for Research and Innovation HORIZON 2020. And the EU Project FEDER 0087 TRANSHABITAT and LIFE12 ENV/FI/000409Tree mortality is a key factor influencing forest functions and dynamics, but our understanding of the mechanisms leading to mortality and the associated changes in tree growth rates are still limited. We compiled a new pan-continental tree-ring width database from sites where both dead and living trees were sampled (2970 dead and 4224 living trees from 190 sites, including 36 species), and compared early and recent growth rates between trees that died and those that survived a given mortality event. We observed a decrease in radial growth before death in ca. 84% of the mortality events. The extent and duration of these reductions were highly variable (1-100 years in 96% of events) due to the complex interactions among study species and the source(s) of mortality. Strong and long-lasting declines were found for gymnosperms, shade- and drought-tolerant species, and trees that died from competition. Angiosperms and trees that died due to biotic attacks (especially bark-beetles) typically showed relatively small and short-term growth reductions. Our analysis did not highlight any universal trade-off between early growth and tree longevity within a species, although this result may also reflect high variability in sampling design among sites. The intersite and interspecific variability in growth patterns before mortality provides valuable information on the nature of the mortality process, which is consistent with our understanding of the physiological mechanisms leading to mortality. Abrupt changes in growth immediately before death can be associated with generalized hydraulic failure and/or bark-beetle attack, while long-term decrease in growth may be associated with a gradual decline in hydraulic performance coupled with depletion in carbon reserves. Our results imply that growth-based mortality algorithms may be a powerful tool for predicting gymnosperm mortality induced by chronic stress, but not necessarily so for angiosperms and in case of intense drought or bark-beetle outbreaks