1. Long-term basal area increment (BAI) in Abies pinsapo was studied to investigate the way density-dependent factors modulate the responses of radial growth to climatic stresses in relict stands of ...a drought-sensitive Mediterranean fir. 2. First, we verified that spatially explicit competition predicts mean A. pinsapo BAI at our study site; i.e. it modulates the degree to which the average climate-driven potential for growth is expressed. Second, we verified that the long-term pattern of temperature predicts the long-term pattern of BAI, estimated as the main trend over a time period of c. 40 years. Finally, we assessed whether the intensity of tree-to-tree competition restrains the potential improvements achieved by our model of BAI when a short-term, high-frequency stressor such as drought (inter-annual precipitation variability) is introduced. 3. We applied Dynamic Factor Analysis (DFA) to characterize regional climatic trends and to test the hypothesis that trees subjected to contrasting competition intensity may differ in their growth pattern. Significant long-term climate trends obtained by DFA were used as predictors of long-term BAI. 4. The mean BAI was mainly determined by competition, whereas growth trends obtained by DFA did not differ among dominant, suppressed and dying trees. Common trends of growth decline were strongly related to long-term, late-winter to summer temperatures, while the residuals were related to total annual precipitation, although with decreasing significance as competition increased. Our results support the contention that the reported patterns of A. pinsapo growth decline and death occur as a result of the interacting effects of both competition and climate stressors acting at long- and short-term time scales. 5.Synthesis. Long-term climatic drought stress was the main driving factor of growth decline in A. pinsapo. Moreover, trees already suffering from competition (a long-term stress) were predisposed to decline given an additional short-term stress, such as a severe drought.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
The combined effects of changes in climate and land use on tree mortality and growth patterns have rarely been addressed. Relict tree species from the Mediterranean Basin serve as appropriate models ...to investigate these effects, since they grow in climatically stressed areas which have undergone intense cover changes. The aim is to use climate, aerial photographs, stand structure and radial-growth data to explain the mortality and historical patterns of growth of Abies pinsapo in the area where this relict species was first protected. Sierra de las Nieves, West Baetic Range, southern Spain. We assessed variations of tree cover in A. pinsapo forests through image analyses of aerial photographs spanning the last 50 years. We sampled 31 stands to assess current altitudinal patterns of forest structure and mortality. We evaluated the relationships between radial growth and regional climate using linear models in three sites at different elevations. Regional warming and a decrease in precipitation were detected. Forest tree cover increased at all elevations from 1957 until 1991, but it afterwards decreased below 1100 m. Currently, the likelihood of tree mortality increases downwards and is associated with dense, closed stands with a low living basal area. In contrast to previous droughts, a sharp synchronized reduction in tree growth, not fully accounted for in linear climate-growth models, occurred at low elevations in 1994-95, but not upwards. It was preceded by a weakening of the negative association between low-elevation growth and water deficit since the late 1970s. The intense densification of A. pinsapo forests following strict protection measures in the late 1950s enhanced the vulnerability of climate-sensitive A. pinsapo forests to recent drier conditions. Such abrupt land-use changes help to explain recent patterns of mortality and growth decline in low-elevation A. pinsapo forests.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
The projected temperature rise, rainfall decrease and concentration of rainfall in extreme events could induce growth decline and die-off on tree populations located at the geographical distribution ...limit of the species. Understanding of adaptive capacity and regional vulnerability to climate change in Mediterranean forests is not well developed and requires more focused research efforts. We studied the relationships between spatiotemporal patterns of temperature and precipitation along the southwestern edge of the Betic range (southern Spain) and measured basal area increment (BAI) and carbon isotope (Δ) in tree ring series of Abies pinsapo and Pinus halepensis, two Mediterranean conifer trees with contrasting drought adaptive capacity. Climatic information was obtained from a network covering a wide range of elevations and distances from the Atlantic and Mediterranean coasts. Temperature trends were tested by the Mann-Kendall test, and precipitation was thoroughly analyzed by quantile regression. Climatic data showed a warming trend, enhanced since the 1970s, while quantile regressions revealed that drought events worsened during the course of the twentieth century. Long-term decrease of A. pinsapo BAI was related to regional warming and changing precipitation patterns, suggesting increasing drought stress on this species. Both temperature and precipitation in the summer influenced wood Δ in P. halepensis, whereas negative correlation between wood Δ and current autumn temperature was yielded for A. pinsapo. Increased intrinsic water use efficiency was inferred from wood Δ in both species; however, A. pinsapo showed sudden growth reductions under drier conditions, while pine trees were able to maintain almost constant BAI values and lower water costs under increasing long-term water stress.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Forest structure modulates Abies pinsapo climate-growth sensitivity.•Thinning may reduce Abies pinsapo decline and mortality by decreasing competition.•Thinning enhances tree-level growth and sap ...flow.•Density reduction was related to higher air temperature and soil water depletion.•Lower competition might increase soil and understory evapotranspiration.
Understanding forest responses to the current climate change requires to investigate the effects of competition, buffering or enhancing process of forests decline. Here we attempt to place intra-specific competition in a climate change context, using as experimental system the drought-sensitive fir Abies pinsapo. We conducted a decade-long (2004–2015) investigation at four permanent plots (two thinned plots and two controls), where all trees were identified, tagged and mapped. Experimental thinning was performed attempting to enhance stand structure diversity by (1) reducing tree competition, (2) increasing the equitability of size classes (i.e. diversity) and (3) randomizing tree spatial pattern. We focus on tree basal area increment and sap flow density, as regards microclimate and competition, to quantify the extent to that thinning alleviates drought in the remaining trees. The results support that lower competition fosters short- to long-term tree-level physiological responses, specifically, improved growth and water uptake in the remaining trees. Density reduction provides a promising strategy for minimizing climate change effects on drought-sensitive tree species by improving resources availability to the remaining trees. Nevertheless, our results also support a higher air temperature and soil water depletion according to density reduction, suggesting that lower competition might also increase soil and understory evapotranspiration. Adaptive management, as the experimental thinning reported here, may increase tree-level resources availability, but the long-term stand-level effectiveness of this approach at sustaining forest ecosystem functioning remains uncertain.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The current scenario of global warming has resulted in considerable uncertainty regarding the capacity of forest trees to adapt to increasing drought. Detailed ecophysiological knowledge would ...provide a basis to forecast expected species dynamics in response to climate change. Here, we compare the water balance (stomatal conductance, xylem water potential, needle osmotic adjustment) of Abies pinsapo, a relict drought-sensitive Mediterranean fir, along an altitudinal gradient. We related these variables to soil water and nutrient availability, air temperature, atmospheric water potential, and vapour pressure deficit during two consecutive years. Our results indicate that A. pinsapo closed stomata rapidly over a very narrow range of soil water availability and atmospheric dryness. This isohydric response during water stress suggests that this relict conifer relied on the plant hormone abscisic acid to maintain closed stomata during sustained drought, instead of needle desiccation to passively drive stomatal closure, needle osmotic adjustment or a plastic response of the xylem to different levels of water availability. Both the soil and foliar nutrient contents suggest that the studied populations are not limited by nutrient deficiencies, and drought was stronger in the warmer low-elevation areas.
Aim of study: Understanding small-scale patterns caused by stochastic factors or community interactions driving forest structure and diversity of Moroccan fir Abies marocana Trab.Area of study: ...Talassemtane fir forest, Talassemtane National Park, Rif Mountains, northern Morocco.Material and methods: Eight plots representative of the structural variability of A. marocana forests were selected, and all tree individuals with diameter at breast height (dbh) ≥2 cm were mapped and measured. We performed four types of spatial point pattern analyses: (1) Univariate analyses to explore the overall trees spatial pattern, (2) bivariate analyses to assess the spatial relationship between juveniles and A. marocana adults, (3) correlation between tree sizes (dbh) and distance between points pairs using the univariate mark correlation function, and (4) random labeling analyses between dominant and suppressed Moroccan fir individuals to assess competition patterns.Main results: We found a strong spatial aggregation of fir individuals and a positive intraspecific association between juveniles and adult trees. However, there were weak but significant distance-dependent effect on tree size and density-dependent effect on suppression pattern.Research highlights: Shade-tolerance, seed dispersal and/or microsite heterogeneity might play important roles in the observed fir patterns. Our results provide a basic knowledge on within-stand Moroccan fir spatial distribution, with implications for adaptive management of these relic forests, and prompting to further research to test advanced hypotheses.Additional key words: Moroccan fir; Talassemtane National Park; Rif forest; Spatial analysis; summary statistics; facilitation; aggregation.Abbreviations used: MF (Moroccan fir); Talassemtane National Park (TNP); dbh (diameter at breast height); Univariate pair-correlation function (g(r)); Heterogeneous Poisson (HP); Bivariate pair-correlation function (g12(r)); Univariate mark correlation function (kmm(r)), Mark connection function (p12(r)).
Pleomorphic adenoma is the most common salivary gland neoplasm, and it can be locally invasive, despite its slow growth. This study aimed to establish a novel cell line (AP-1) derived from a human ...pleomorphic adenoma sample to better understand local invasiveness of this tumor. AP-1 cell line was characterized by cell growth analysis, expression of epithelial and myoepithelial markers by immunofluorescence, electron microscopy, 3D cell culture assays, cytogenetic features and transcriptomic study. Expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) was also analyzed by immunofluorescence and zymography. Furthermore, epithelial and myoepithelial markers, MMPs and TIMPs were studied in the tumor that originated the cell line. AP-1 cells showed neoplastic epithelial and myoepithelial markers, such as cytokeratins, vimentin, S100 protein and smooth-muscle actin. These molecules were also found in vivo, in the tumor that originated the cell line. MMPs and TIMPs were observed in vivo and in AP-1 cells. Growth curve showed that AP-1 exhibited a doubling time of 3.342 days. AP-1 cells grown inside Matrigel recapitulated tumor architecture. Different numerical and structural chromosomal anomalies were visualized in cytogenetic analysis. Transcriptomic analysis addressed expression of 7 target genes (VIM, TIMP2, MMP2, MMP9, TIMP1, ACTA2 e PLAG1). Results were compared to transcriptomic profile of non-neoplastic salivary gland cells (HSG). Only MMP9 was not expressed in both libraries, and VIM was expressed solely in AP-1 library. The major difference regarding gene expression level between AP-1 and HSG samples occurred for MMP2. This gene was 184 times more expressed in AP-1 cells. Our findings suggest that AP-1 cell line could be a useful model for further studies on pleomorphic adenoma biology.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Climate change may affect tree-pathogen interactions. This possibility has important implications for drought-prone forests, where stand dynamics and disease pathogenicity are especially sensitive to ...climatic stress. In addition, stand structural attributes including density-dependent tree-to-tree competition may modulate the stands' resistance to drought events and pathogen outbreaks. To assess the effects of stand structure on root-rot-related mortality after severe droughts, we focused on Heterobasidion abietinum mortality in relict Spanish stands of Abies pinsapo, a drought-sensitive fir. We compared stand attributes and tree spatial patterns in three plots with H. abietinum root-rot disease and three plots without root-rot. Point-pattern analyses were used to investigate the scale and extent of mortality patterns and to test hypotheses related to the spread of the disease. Dendrochronology was used to date the year of death and to assess the association between droughts and growth decline. We applied a structural equation modelling approach to test if tree mortality occurs more rapidly than predicted by a simple distance model when trees are subjected to high tree-to-tree competition and following drought events. Contrary to expectations of drought mortality, the effect of precipitation on the year of death was strong and negative, indicating that a period of high precipitation induced an earlier tree death. Competition intensity, related to the size and density of neighbour trees, also induced an earlier tree death. The effect of distance to the disease focus was negligible except in combination with intensive competition. Our results indicate that infected trees have decreased ability to withstand drought stress, and demonstrate that tree-to-tree competition and fungal infection act as predisposing factors of forest decline and mortality.
•Forest structure modulates Abies pinsapo climate-growth sensitivity.•Thinning may reduce Abies pinsapo decline and mortality by decreasing competition.•Thinning enhances tree-level growth and sap ...flow.•Density reduction was related to higher air temperature and soil water depletion.•Lower competition might increase soil and understory evapotranspiration.
Understanding forest responses to the current climate change requires to investigate the effects of competition, buffering or enhancing process of forests decline. Here we attempt to place intra-specific competition in a climate change context, using as experimental system the drought-sensitive fir Abies pinsapo. We conducted a decade-long (2004–2015) investigation at four permanent plots (two thinned plots and two controls), where all trees were identified, tagged and mapped. Experimental thinning was performed attempting to enhance stand structure diversity by (1) reducing tree competition, (2) increasing the equitability of size classes (i.e. diversity) and (3) randomizing tree spatial pattern. We focus on tree basal area increment and sap flow density, as regards microclimate and competition, to quantify the extent to that thinning alleviates drought in the remaining trees. The results support that lower competition fosters short- to long-term tree-level physiological responses, specifically, improved growth and water uptake in the remaining trees. Density reduction provides a promising strategy for minimizing climate change effects on drought-sensitive tree species by improving resources availability to the remaining trees. Nevertheless, our results also support a higher air temperature and soil water depletion according to density reduction, suggesting that lower competition might also increase soil and understory evapotranspiration. Adaptive management, as the experimental thinning reported here, may increase tree-level resources availability, but the long-term stand-level effectiveness of this approach at sustaining forest ecosystem functioning remains uncertain.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Radial growth and xylogenesis were studied to investigate the influence of climate variability and intraspecific competition on secondary growth in Abies pinsapo Boiss., a relic Mediterranean fir. We ...monitored the responses to three thinning treatments (unthinned control –C–, 30% –T30– and 60% –T60– of basal area removed) to test the hypothesis that they may improve the adaptation capacity of tree growth to climatic stress. We also assessed whether xylogenesis was differentially affected by tree-to-tree competition. Secondary growth was assessed using manual band dendrometers from 2005 to 2007. In 2006, xylogenesis (phases of tracheid formation) was also investigated by taking microcores and performing histological analyses. Seasonal dynamics of radial increment were modeled using Gompertz functions and correlations with microclimate and radiation were performed. Histological analyses revealed it as fundamental to calibrate the dendrometer estimates of radial increment and to establish the actual onset and end dates of tracheid production. The lower radial-increment rates and number of produced tracheids were observed in the trees subjected to high competition in the unthinned plots. The growing season differed among the plots, and its duration ranged from an average of 78 days in unthinned plots to 115 days in thinned ones (T60). Variations in the beginning of the growing season (13 April to 22 May) and earlywood–latewood transition (early August) were mainly determined by the temperature pattern, while the onset and the end of the growing season were related to both annual precipitation and tree-to-tree competition. The tracheid-formation phases of radial enlargement and cell-wall thickening showed similar patterns in the trees from thinned and unthinned plots subjected to low and high competition, respectively, but the mean number of tracheids in each phase was always higher in the trees from the thinned plots. The reduction of competition through thinning induced a longer growing season and enhanced the radial growth in A. pinsapo.
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