Sustainable management of Pinus sylvestris L. plantations under changing climatic conditions requires a comprehensive understanding of how climate variability and drought influence tree growth. This study investigates vegetation activity assessed via the Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), and radial growth variability, (EW – earlywood width, LW – latewood width, TRW – tree-ring width, and BAI – basal area increment), in a P. sylvestris plantation in central Albania. This is the first such study conducted in Albania, addressing a significant geographical gap in the southernmost natural range of this species in the Balkans. Climate-growth relationships were explored using Pearson correlation analysis with temperature, precipitation, and drought indices (SPI – Standardised Precipitation Index and SPEI – Standardised Precipitation Evapotranspiration Index). August NDVI and EVI correlated positively with LW and BAI. Both vegetation indices were positively associated with spring and autumn temperatures, while EVI with June and September precipitation. NDVI was most responsive to the 7-month SPI and SPEI in April, whereas EVI was sensitive to the 7-month SPI in September and the 4-month SPEI in June. Summer temperatures negatively impacted LW and BAI. July precipitation strongly enhanced LW, TRW, and BAI. EW showed the highest positive correlation with the 4-month SPI in August but was negatively correlated at scales longer than 14 months, in winter and spring. LW and TRW demonstrated remarkable positive associations with SPI and SPEI in July (1-month). BAI was most drought-sensitive in August (4-month for SPEI and 6-month for SPI). These findings provide critical insights into the climate sensitivity of P. sylvestris and offer a scientific basis for adaptive forest management in Mediterranean regions increasingly affected by drought and warming trends.

The sustainable management of Pinus nigra plantations under changing climatic conditions requires a comprehensive understanding of how tree growth dynamics and climate-growth relationships are influenced by site orientation and tree social status. This study investigates growth parameters in two P. nigra plantations situated on contrasting slopes in central Albania: northwest (NW) and southeast (SE). Trees were classified into dominant (Dom) and suppressed (Supp) social classes. Radial growth responses to temperature, precipitation, and drought measured via the Standardized Precipitation Evapotranspiration Index (SPEI), were assessed using Pearson correlation analyses. The results revealed Dom trees exhibiting greater growth than Supp individuals, and overall higher growth observed at the SE site. Trees at the SE site were more responsive to summer temperature and precipitation than those at the NW site. Radial growth responses to SPEI were most pronounced in latewood, with the strongest effects observed in Dom trees at NW and Supp trees at SE. The highest correlations were found with the 1-month SPEI in July at NW, and the 4-month SPEI in August at SE. These findings offer valuable insights for the development of adaptive forest management strategies under increasingly warm and arid conditions.

To understand and manage Mediterranean forested ecosystems under a changing climate, forest managers require improved knowledge of forest plantations ability to adaptat to drought stress. This paper analyses the radial growth dynamics (earlywood width, EW; latewood width, LW; tree-ring width, TRW; basal area increment, BAI) and vegetation activity (normalized difference vegetation index, NDVI; enhanced vegetation index, EVI) of Pinus nigra plantations growing on two sites (lower, upper) with contrasting edaphic conditions, in eastern Albania, and evaluates the growth responses to climate (temperature and precipitation) and drought (standardized precipitation index, SPI; standardized precipitation evaporation index, SPEI). P. nigra plantations showed pronounced differences in growth and response to climate (drought) and soil variations between sites. Trees at the lower site, located on poor soils, showed lower growth rates and higher response to June-July precipitation, August temperatures and drought index SPI (< 8 months) in summer as compared to trees at the upper site distributed on rich soils which remained more buffered. At the upper site, the high vegetation activity in July (EVI) and August (NDVI) affected considerably the radial growth rate, whereas at the lower site, only July EVI showed significant relationship with EW, LW and TRW. Vegetation indices at the lower site showed the strongest association with drought. We conclude that future management of P. nigra plantations should be properly adapted to modulate variations in climate and to sustain tree growth and productivity, triggered by local site conditions.

In the context of changing climate conditions, it is crucial to understand how trees maintain resistance and resilience to and recover from drought stress and management-related disturbances, and how management (intensive/extensive) modulates tree growth responses to climate. Dendrochronological methods were used to examine radial growth rates, to reconstruct disturbance history and to evaluate growth resistance and resilience to and recovery from disturbance events identified by pointer year analysis in two coexisting Quercus species (Q. macrolepis Kotschy and Q. trojana Webb). Moreover, a dendro-ecological approach was used to quantify climate-growth relationships, including a drought index, the Standardised Precipitation Index (SPI). Q. trojana/Q. macrolepis showed major/moderate growth releases and moderate growth suppression. Q. trojana demonstrated statistically lower growth recovery than Q. macrolepis. The climatic drivers of radial growth in Q. macrolepis were May, June, September precipitation, July temperatures and the SPI accumulated since the previous year (up to 18 months); whereas Q. trojana responded significantly to May and June precipitation, July temperatures and the SPI at mid-time scales (< 8 months). Under intensive management, both species were more responsive to precipitation, temperature and short to mid-time scale SPI than during the extensive management period where they showed loss of sensitivity to spring-summer precipitation, temperature and SPI. These results are relevant to understand species vulnerability to climate and management/ human-related disturbances, and the effects of intensive/extensive management in modulating climate (drought)-growth relationships in Q. macrolepis and Q. trojana trees.

Assessment of forest areas affected by wildfire is crucial for designing appropriate management strategies to support post-wildfire restoration. This study integrates Remote Sensing and GIS data to map burned areas and severity, and regeneration of vegetation in a Mediterranean forest type ecosystem (National Park "Dajti Mountain", NPDM), in Albania. Landsat 8 satellite imagery was employed to calculate various spectral indices such as the Normal Burn Ratio Index (NBR), NBR2, the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI). Burn severity levels were defined by using the dNBR thresholds developed by Key and Benson (2006). The accuracy of burn severity map produced was evaluated by relating field-based Composite Burn Index (CBI) and satellite-derived metrics (dNBR) from Landsat-8. By means of dNBR and dNBR2 we detected and mapped several burned forest areas within the NPDM, at the sites of Shkallë, Qafëmolle, Ibë, Tujan, Derje, Selbë, Surrel and Dajt, which were affected by wildfire during the year 2017. The dNBR produced the best results for burned areas mapping and burn severity assessment (91.7%) over the dNBR2 (89.8%). The dNBR and dNBR2 index maps showed that a total of 103.59 and 105.72 hectares of forests was affected by wildfire. Areas with different levels of burn severity were detected: 17.29 and 23.80% unburned, 43.36 and 45% low, 15.11 and 12.13% moderate, 24.93 and 21.2% high. Overall, the dNBR2 index produced lower percentages of wildfire-affected areas at high and moderate rates compared to the dNBR index while for unburned areas the dNBR2 index resulted in higher percentages. Vegetation recovery during the subsequent growing season was generally good as revealed by the high dNDVI and dEVI values, indicating the reactivation of photosynthetic activity. This information is useful for forest managers/specialists to design relevant strategies for the proper rehabilitation/management of burned forest areas in the future.

Warmer and drier climatic conditions are projected for the 21st century; however, the role played by extreme climatic events on forest vulnerability is still little understood. For example, more severe droughts and heat waves could threaten quaternary relict tree refugia such as Circum-Mediterranean fir forests (CMFF). Using tree-ring data and a process-based model, we characterized the major climate constraints of recent (1950-2010) CMFF growth to project their vulnerability to 21st-century climate. Simulations predict a 30% growth reduction in some fir species with the 2050s business-as-usual emission scenario, whereas growth would increase in moist refugia due to a longer and warmer growing season. Fir populations currently subjected to warm and dry conditions will be the most vulnerable in the late 21st century when climatic conditions will be analogous to the most severe dry/heat spells causing dieback in the late 20th century. Quantification of growth trends based on climate scenarios could allow defining vulnerability thresholds in tree populations. The presented predictions call for conservation strategies to safeguard relict tree populations and anticipate how many refugia could be threatened by 21st-century dry spells.

Contrasted response of Quercus macrolepis growth to climate conditions during summer months indicated increased climate-related control of tree growth at high elevation site modulated by topographic characteristics and tree age.

Improved knowledge of the time scales at which drought stress mostly influences tree growth is crucial for the early detection of forest dieback. This study aimed to evaluate the impact of climate (temperature and precipitation) on vegetation activity (normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI)) of Pinus halepensis Mill. and Pinus pinea L. mixed forest located in western Albania and to assess the drought impact (standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI)) calculated at different time scales (1–12 months) on radial growth (earlywood width, latewood width, and tree-ring width) and vegetation activity of these species. Both vegetation indices showed a negative response to August temperatures, and the EVI responded positively to September precipitation. NDVI and EVI were significantly affected by the SPI in spring and late summer. All tree-ring features in P. halepensis were positively related with EVI in August, whereas P. pinea latewood width showed a significant and positive relationship with NDVI in September. Radial growth of P. halepensis responded significantly to both drought indices in late summer and early autumn, particularly the latewood width. Contrastingly, in P. pinea, only earlywood width showed vulnerability, mostly to the summer SPEI drought indices. These results are relevant to understand the impacts of increased drought intensity and frequency on tree radial growth and vegetation activity in a region that is vulnerable to climate variability.

In this study are presented chronologies of earlywood (EW), latewood (LW) and tree-ring widths (RW) of a Pinus halepensis (P. halepensis) and Pinus pinea (P. pinea) natural forest stand growing in western Albania. Bootstrapped correlations and pointer year analysis were combined in a dendroclimatological study to evaluate climate-growth relationships in both pine species as well as to assess the spatial outreach of our chronologies evaluating them with those of the same species from other Mediterranean countries. We found that both species responded positively to precipitation and Indexed Percentage Average Precipitation (% AvP) in late summer-early autumn, particularly the LW, whereas summer temperatures constrained the growth of P. halepensis tree-ring features. Current January temperature and Potential Evapotranspiration (PET) showed positive relationship with P. pinea LW and RW. The same association was observed when considering PET in spring and P. halepensis LW and RW. Pointer year analysis showed that inhibitory climatic drivers of radial growth for both species were low precipitation from previous winter and current summer, associated with low temperatures during autumn. Our P. halepensis chronology showed a wider spatial outreach than that of P. pinea when compared to those from other Mediterranean countries. We conclude that current January temperatures and September precipitation are very important for P. pinea growth influencing both EW and LW growth whereas P. halepensis is mostly affected by the summer-early autumn climate conditions.

The long-term radial growth responses to drought and climatic variability of less-studied species such as Abies borisii-regis (Mattf.) remain poorly understood.We tested the hypothesis that severe short-term drought conditions during summer months will impact the radial growth of A. borisii-regis (Mattf.) trees and such impact will have a more pronounced effect on latewood (LW) than earlywood (EW) width.Correlation analysis was employed to investigate the impact of climatic drivers (temperature, precipitation) and drought, using the Standardized Precipitation Evapotranspiration Index (SPEI) calculated at cumulative time scales (1-12 months), on EW, LW and tree-ring width (TRW) in A. borisii-regis (Mattf.) trees from South-Eastern Albania.We found that EW width was positively correlated with precipitation in July and previous September, while the LW width and TRW was enhanced by the current June-July precipitation. Previous autumn and current summer high temperatures constrained the radial growth in A. borisii-regis (Mattf.) trees, particularly the LW and TRW. All the tree-ring widths components showed the highest significant response to drought at short cumulative time scales (<4 months) mainly during July, August and September. The highest impact of drought was observed for the LW width.Under a future reduction of summer precipitation and temperature increase, the A. borisii-regis (Mattf.) may show a decrease in EW formation, causing a decline of radial growth, leading to a reduction in hydraulic conductivity and carbon uptake in these forests. (C) 2014 Elsevier GmbH. All rights reserved.

We lack information regarding the main factors driving growth responses to drought in tree species with different vulnerability against this stressor and considering sites with contrasting climatic conditions. In this paper, we identify the main drivers controlling growth response to a multi-scalar drought index (Standardized Precipitation Index, SPI) in eight tree species (Abies alba, Pinus halepensis, Quercus faginea, Pinus sylvestris, Quercus ilex, Pinus pinea, Pinus nigra, Juniperus thurifera). We sampled forests growing across a pronounced climatic gradient under Mediterranean conditions in north-eastern Spain. To summarize the patterns of growth responses to drought, we used principal component analysis (PCA). To determine the main factors affecting growth responses to drought, correlation and regression analyses were carried out using a set of abiotic (climate, topography, soil type) and biotic (Normalized Difference Vegetation Index, Enhanced Vegetation Index, tree-ring width, diameter at breast height) predictors and the PCs loadings as response variables. The PCA analysis detected two patterns of growth responses to drought corresponding to xeric and mesic sites, respectively. The regression analyses indicated that growth responses to drought in xeric forests were mainly driven by the annual precipitation, while in mesic sites the annual water balance was the most important driver. The management of Mediterranean forests under the forecasted warmer and drier conditions should focus on the main local factors modulating the negative impacts of drought on tree growth in xeric and mesic sites.

We evaluated the response of the Earth land biomes to drought by correlating a drought index with three global indicators of vegetation activity and growth: vegetation indices from satellite imagery, tree-ring growth series, and Aboveground Net Primary Production (ANPP) records. Arid and humid biomes are both affected by drought, and we suggest that the persistence of the water deficit (i.e., the drought time-scale) could be playing a key role in determining the sensitivity of land biomes to drought. We found that arid biomes respond to drought at short time-scales; that is, there is a rapid vegetation reaction as soon as water deficits below normal conditions occur. This may be due to the fact that plant species of arid regions have mechanisms allowing them to rapidly adapt to changing water availability. Humid biomes also respond to drought at short time-scales, but in this case the physiological mechanisms likely differ from those operating in arid biomes, as plants usually have a poor adaptability to water shortage. On the contrary, semiarid and subhumid biomes respond to drought at long time-scales, probably because plants are able to withstand water deficits, but they lack the rapid response of arid biomes to drought. These results are consistent among three vegetation parameters analyzed and across different land biomes, showing that the response of vegetation to drought depends on characteristic drought time-scales for each biome. Understanding the dominant time-scales at which drought most influences vegetation might help assessing the resistance and resilience of vegetation and improving our knowledge of vegetation vulnerability to climate change.

Assessing the risk, the severity and the likely evolution of droughts are key tasks for improving preparedness of regions prone to drought conditions, and mitigation of drought consequences. The access to real‐time and high‐quality climatic information is essential for this purpose. Different climatic databases are being developed and made available on real time by climatic research institutions, but their capability for quantifying droughts characteristics including severity, or spatio‐temporal variability, is uncertain given their low spatial resolution. In this study, we assessed the capability of three databases with contrasted spatial resolution for measuring spatial and temporal variability of drought occurrence. The standardized precipitation index, calculated for each database, showed that the low resolution datasets allow an acceptable measurement of the magnitude, intensity and duration of droughts, while failing mostly in detecting the spatial patterns of the specific drought episodes. Moreover, the capability of the datasets for assessing the impacts of droughts on surface hydrology and tree growth was examined. Results confirmed the usefulness of the drought index for assessing drought impacts on water resources and forest ecosystems even when low resolution databases are used. Copyright © 2012 Royal Meteorological Society

Short- and long-term growth responses to drought and climatic influences still remain poorly understood. In this study, we investigated the impact of climatic drivers (temperature, precipitation) and drought, using the Standardized Precipitation Index (SPI) calculated at different time scales (1–48 months), on earlywood (EW) and latewood (LW) widths in Pinus halepensis. Nine forests subjected to dry summer conditions were sampled in Mediterranean semi-arid areas from north-eastern Spain. In addition, we explored the seasonal dynamics of cambial activity and wood formation in relation to short-term climate variability. We found two peaks of tracheid cell production corresponding to EW (May–June) and LW (mid-July–August) growth phases, associated with a sharp decrease in enlarging cells in early July in response to low water availability. In the period of analysis (1970–2005), EW growth was positively correlated with precipitation in previous December and current January, April, May and June, while it was negatively correlated with temperature in June and July. LW was correlated positively with minimum temperatures in January. Probably this was an indirect relationship as a consequence of increased EW width at higher January temperatures. Drought affected more negatively EW than LW formation as evidenced the higher SPI-EW correlation (r = 0.72) than the SPI-LW one (r = 0.54). The strongest EW response to drought was observed in July, whereas the highest LW response to drought occurred in September; and this seasonal pattern matched the phases of lowest EW and LW tracheid production. Under a future reduction of winter and spring precipitation, the studied forests may show a decrease in tracheid cell production, causing a decline of radial growth, a reduction in hydraulic conductivity and, indirectly, a hampered carbon uptake in such semi-arid woodlands.