In our studies, we used tree-rings as indirect archives of climate changes and environmental pollution in 20th and 21st century. In Poland the highest levels of pollutants were recorded in 1980s (Boden
The climate changes and industrial pollutant emissions occur during physiological processes responsible for plant growth and also can influence stable isotope composition of wood and its components (Craig, 1954; Farquhar and Lloyd, 1993; McCarroll and Loader, 2004; Sensuła, 2015). There has been much discussion about the biological effects of pollutant pressure on trees, which concerned yearly variation of stable isotope concentration in tree rings and needles (Craig, 1954; Farquhar and Lloyd, 1993; Field
According to the NOAA (2016), the average global atmospheric CO2 concentration has risen from 331 ppm in 1975 to 393 ppm in 2012. The observed anthropogenic impact on the carbon cycle is mainly related to various global industrial activities (Boden
The aim of our studies was to investigate the sensitivity of the pine populations to various climatic factors (such as the air temperature, the precipitation, the humidity and the sunshine duration) in the area influenced by the industrial pollution. The variation of the annual radial growth was used as an indicator of the tree’s response to climate factors during the period of time since 1951–2012, when strong increase of industrial activities in the investigated area were observed. The sampling sites were located in different distance and in different geographical directions from industrial factories (Sensuła
The mass spectrometric analysis of the carbon and oxygen stable isotope composition of cellulose extracted from the pine population growing in the most polluted site was complementary to dendrochronological studies. The isotopic composition of pine tree-rings was used to study the climatic changes in the industrialized area in the past to better understand future consequences of ecosystem changes (Schweingruber, 1996; De Vries
The objectives of this study were to analyze: (1) the record of climate changes and (2) the biological adaptation to pollution of pine growing nearby chemical and nitrogen factories in Kędzierzyn-Koźle during the period of industrial development and implementation of proecological policy in Poland. There is still a lack of data concerning the environmental changes in the most industrialized part of Poland over the last century. In these studies, we determined the stable carbon and oxygen isotopes concentration in annual tree rings of pine growing in close proximity to chemical factories in Kędzierzyn-Koźle during the period of industrial development and implementation of pro-ecological policy in Poland.
Kędzierzyn-Koźle (50°20 ′N; 18°13′E) is located near two factory complexes (
The period from 1951 to 2012 AD was characterised in the regional climate records by an annual average temperature of about 9°C (data range from 6.7 to 10.6°C), and a mean annual sum of precipitation of around 610 mm (data range from 359 to 868 mm/year); mean annual number of sunshine hours is approx. 1530 (data range from 1108 to 1978), relative humidity around 80% (data range from 75 to 86%). The lowest precipitation was observed between mid-1980s and mid-1990s (
Scots pine (
All sites were classified as fresh mixed broadleaved forests. In order to avoid different dendroecological reaction of juvenile wood, an attempt was made to select pine stands aged between 80 (site A) and 100 years (sites C, B, N, S and T) which is the felling age of Scots pine. The pine trees were dominant or co-dominant individuals.
One increment core from each tree was taken at a height of 1.3 m above ground. Tree-ring widths were measured to the nearest 0.01 mm. The tree-rings were dated and rechecked using the COFECHA program (Holmes, 1983). Each tree-ring width series was standardized to remove non-climatic trends due to age and growth effects. Therefore, in each year the annual sensitivity index (si) was calculated according to the formula:
where xi is the tree-ring width in year
The mean change of the tree-ring width for the 1951–2012 period was evaluated by the mean sensitivity (MS). MS indicates interannual changes of the trees’ sensitivity to climate factors (Fritts, 1976). The site sensitivity chronology was constructed on the basis of series sensitivity. The site sensitivity chronology exposed the short-term variance due to variation of climatic factors. The similarity of short-term incremental reactions of trees in each pine populations was evaluated by calculating the mean between-tree correlation (rbt). The calculated index EPS enables an assessment of the representativeness of the constructed site chronologies (Wigley
The principal component analysis (PCA) was applied to identify the short-time factors affecting tree-ring widths. The identification of PC1 and PC2 was based on an analysis of the component scores. The variables (n=52) were site sensitivity chronologies. The cluster analysis (CA) based on Ward’s method and 1-r Pearson’s distance has been used to analyse similarity of the response of each pine population to climate elements in the 1951–2012 period. The variables (n=52) were correlation coefficients between the site sensitivity chronologies and monthly temperature, precipitation, relative humidity and sunshine duration from the prior September to the current September. Response function analysis (Fritts, 1976; Holmes and Lough, 1999) was used to identify the climatic factors that determined the PC1 and PC2. These results were verified by analyzing the correlation between site sensitivity chronologies and the climate parameters.
The analysed samples covered the period 1975–2012 AD. The α-cellulose samples were extracted from increment cores of ten representative trees growing in the C sampling site. The pines growing in this sampling site were characterized by the highest level of tree ring width reduction in the period of time between 1958–1991.
The absolutely dated annual tree-rings were manually separated as thin slivers and pooled and homogenized. The α-cellulose samples were extracted by applying the procedures based on the Green’s method (1963) used in The Mass Spectrometry Laboratory of the Silesian University of Technology (Pazdur
The initial stage of the process involved cutting of annual rings from the cores in the sample producing fine shavings <0.5 mm thick, cut from wood with a knife. Afterwards, the samples were treated with a toluene-ethyl alcohol mixture (in proportion 1:1, at 80°C, over 4 hours), ethyl alcohol (at 80°C, over 4 hours), distilled water (at 80°C, over 1 hour). The reaction was performed in a Soxhlet apparatus. Afterwards, the samples were dried overnight. The dried and weighed samples were placed into the glass test-tubes. The next step was bleaching with NaClO2 and CH3COOH solution (175 ml of distilled water, 2.5 g of NaClO2 and 1.7 ml of CH3COOH was added per 1g of each sample) at 70°C, over 1 hour in order to remove lignin and to extract cellulose. This process was repeated 5 times. In the next step the solution was removed by decanting. The samples were rinsed with boiling distilled water and then with cold distilled water up to neutral pH. Afterwards, the samples were treated with 50 ml of 10% NaOH solution (at 70°C, over 45 minutes). Afterwards the solution was removed and samples were rinsed with cold distilled water. Then the samples were treated with 17% NaOH solution (at room temperature for 45 minutes). The solution was then removed from the tubes and samples were rinsed with distilled water. At the end of the extraction process the samples were treated with 10 ml of 1% HCl solution and rinsed up to neutral pH. The obtained α-cellulose was dried on a hot plate at 60°C overnight. To ensure homogeneity the chemical pre-treatment was carried in an ultrasonic bath.
In order to determine the δ13C values, the samples (0.060 mg) were loaded into tin capsules and combusted at a temperature of 1100°C, CO2 was separated in a gas chromatography column of the elemental analyser (EuroVector). In order to determine the δ18O values, the samples (0.095 mg) were loaded into silver capsules. To displace moisture-containing air in the cellulose samples, the samples were heated over 24 hours in a vacuum line (60°C) and after that they were put into a special air-filled dry box before stable isotope ratio determination (Sensuła
The stable oxygen and carbon isotope compositions of the samples were determined using an Isoprime continuous flow isotope ratio mass spectrometer (GV Instruments, Manchester, UK) at the Mass Spectrometry Laboratory of the Silesian University of Technology.
The relative deviation of the isotopic composition is expressed, in parts per thousand (‰), as δ=(Rsample /Rstandard −1)⋅ 1000, Where Rsample and Rstandard are the ratios of the heavy to the light isotope concentration in the sample and in the standard, respectively. The δ13C results are reported in values relative to VPDB (Vienna Pee Dee Belemnite), whereas the δ18O results are reported in values relative to VSMOW (Vienna Standard Mean Ocean Water). In these measurements, wood (C-5) and α-cellulose (C-3) reference materials from IAEA were used.
The isotopic discrimination in photosynthesis was calculated according to the model of Farquhar and Lloyd (1993):
where Ci is intercellular CO2 concentration, Ca is ambient CO2 concentration,
Each of the pine chronologies constructed in this study is a local growth pattern of the pine population. These isotopic records are the result of the response of the trees to variations of various environmental factors: climatic drivers and human activities. For the statistical calculation, Statistica 12 software (StatSoft, Inc., 2014) was applied.
The average width of the radial increment of the studied pine populations ranged from 1.31 mm to 2.20 mm (
Statistical characteristics of the site chronologies for the 1951–2012 period. TRW – mean tree-ring width; TRI – mean tree-ring index; MS – mean sensitivity; rbt – the mean correlation of standardized series of trees – the signal strength of the chronology, EPS – the expressed population signal is a statistic for examining the common variability in a chronology.Site Lat. N, Lon. E Elevation (m) TRW (cm) TRI MS rbt EPS A 50°19’ ,18°15’ 192 2.20 1.0 0.23 0.42 0.93 B 50°20’ ,18°18’ 209 1.81 1.0 0.26 0.52 0.95 C 50°20’ ,18°19’ 218 1.31 1.0 0.28 0.49 0.95 N 50°22’ ,18°23’ 218 1.80 1.0 0.21 0.39 0.93 S 50°18’ ,18°20’ 215 1.48 1.0 0.22 0.46 0.93 T 50°18’ ,18°17’ 207 1.77 1.0 0.26 0.49 0.95
In the 1970s the pines strongly reduced their radial increments (
It is interesting that the year-to-year sensitivity of trees remained at a similar level throughout the analysed period (
Short-term changes of radial increments of the pine populations differed. This diversity is indicated by the location of the site sensitivity chronologies in relation to component loadings of PC1 and PC2 (
Climate determines the short-term variance of incremental reaction of trees. This kind of variance is illustrated by sensitivity chronologies. It can therefore be assumed that the two main components – PC1 and PC2 – depict the climate factors that had a significant impact on the variance of radial increments of pines. This is confirmed by the results of cluster analysis. It was found that a series of correlation coefficients for the populations B, C, N and T formed a single cluster, while the series of populations A and S differed significantly (
With the response function analysis, the climate features described by PC1 and PC2 were identified (
In 3 cases PC1 and PC2 were significantly correlated with the same climate parameters. This applies to relative humidity, rainfall and sunshine duration in May of the year of ring formation (
The results were similar in the case of rainfall of the previous September and of current May and July. The similar sensitivity of 6 pine populations to the amount of sunshine duration in April, May and August was also discovered. Similar patterns are connected with the effect of relative humidity of the previous September, and current February, March and April (
The results of response function analysis performed for PC2 were also confirmed. It turned out that the incremental sensitivity of pine populations A and S to the temperature of the previous September and December and current June and July was different. It also differed from the sensitivity of the remaining pine populations (B, C, N and T) (
The impact of rainfall, sunshine duration and relative humidity in the May of the ring formation year on pine radial increments was specific. On the one hand, the conditions above have had a similar effect on the incremental reactions of pines in all populations, as monthly values of these elements significantly correlate with PC1. On the other hand, they differentiate the incremental rhythm of each population, as they significantly correlate with PC2 (see
Analysis of stable isotope fractionation in annual tree rings of pines, growing in the sampling site where the strongest reduction of tree ring width was noted, is the complemental analysis to dendrochronological method. The pine tree-ring isotopic chronologies constructed in this study is a local grown pattern of the partial pine population (site C). These isotopic records (
δ18O values varied between 27.4‰ to 31.8‰ (
The analysis of combined measurement of carbon and oxygen isotopes ratio (
To describe the variation of the carbon and oxygen isotope composition of cellulose in annual tree-rings of pine caused by climate changes and human activities we used a model (Sensuła and Pazdur, 2013a, 2013b) based on multiple regressions (
where M is the month (from April to September), b is the regression coefficient for the following variables: T (mean of the monthly maximum temperatures), P (monthly precipitation sum), S (monthly hours of sunshine duration), H (mean of the monthly relative humidity), whereas ba corresponds to the interdependences between the monthly climate factors and other environmental changes.
The regression coefficient (Eq. 3.1) for the following variables: T (mean of the monthly maximum temperatures), P (monthly total precipitation), S (monthly hours of sunshine duration), H (mean of the monthly relative humidity). bi – multiple regression parameters. The test of significance gives a p-value (n=38).Variables Units δ13Ccor δ18O bi pi bi pi ba ‰ −15.85 0.004 −34.53 0.267 TApr ‰ / °C −0.028 0.133 −0.103 0.391 TMay ‰ / °C −0.043 0.156 0.421 0.043 TJun ‰ / °C 0.037 0.106 0.026 0.857 TJul ‰ / °C −0.007 0.817 0.306 0.129 TAug ‰ / °C 0.047 0.110 0.219 0.247 TSep ‰ / °C −0.019 0.352 −0.001 0.993 PApr ‰ / mm 0.001 0.556 0.004 0.755 PMay ‰ / mm −0.003 0.079 0.004 0.693 P Jun ‰ / mm −0.001 0.596 −0.007 0.588 PJul ‰ / mm −0.001 0.592 −0.009 0.270 PAug ‰ / mm 0.002 0.148 −0.002 0.797 PSep ‰ / mm −0.001 0.652 0.002 0.872 SApr ‰ / hours of sunshine −0.003 0.179 0.020 0.124 SMay ‰ / hours of sunshine 0.001 0.521 −0.021 0.110 SJun ‰ / hours of sunshine 0.007 0.003 −0.008 0.541 SJul ‰ / hours of sunshine −0.006 0.045 0.029 0.107 SAug ‰ / hours of sunshine 0.003 0.125 −0.007 0.497 SSep ‰ / hours of sunshine −0.006 0.013 0.019 0.205 HApr ‰ / % −0.044 0.104 0.290 0.106 HMay ‰ / % 0.040 0.090 −0.237 0.128 HJun ‰ / % 0.088 0.009 −0.150 0.446 HJul ‰ / % −0.064 0.104 0.474 0.071 HAug ‰ / % −0.009 0.672 −0.038 0.782 HSep ‰ / % −0.090 0.001 0.120 0.374
The value of the correlation coefficient between the measured and modelled δ13C in α-cellulose is equal to 0.93, whereas the value of the correlation coefficient between the measured and modelled δ18O in α-cellulose is equal to 0.78.
Diffuse air pollution (carbon dioxide) caused the variation in the ratio of water used in plant metabolism to water lost by the plant through transpiration (WUE). In the period of time from 1975 and 2012, according to NASA (2016) the global concentration of mid-tropospheric carbon dioxide ranged from
Site chronologies of radial increment sizes represent incremental patterns of pines from partial populations. They illustrate the specific response of pine trees to various environmental factors, including the climate factor. It should be emphasized that in the years 1951–2012 the size of radial increments of the studied pine population changed. In the 1970s pines strongly reduced their radial increment. The reason for the reduction was a strong increase in industrial pollution. Despite this fact, pines in the area preserved their high year-to-year sensitivity to short-term impulses from the environment. It turned out, however, that the year-to-year rhythm of radial increments in particular populations was different. The reason was their different sensitivity to particular elements of the climate. In particular, two pine populations (S and A) were different in this respect – both, from each other and from the other four populations. They are located away from the main flow of air masses carrying pollutants from local factories. It is therefore assumed that the differences in the relations between climate and radial increments were the result of the varying pressure of pollution on the studied populations of trees. However, the influence of other factors, such as unrecognized differences in habitat conditions and the age of the trees cannot be excluded. Site A pines were in fact younger than others by approx. 20 years.
The differences in sensitivity of pines from A and S populations to the climatic elements described by PC2 were confirmed by the analysis of site chronology correlations. The Principal component analysis (PCA) is therefore an effective method of recognizing the similarities and differences in the sensitivity of trees to the climatic factor.
Interpretation of the modifying effect of pollutants on the relation between climate and tree increments is difficult. The influence of pollutants depends on the distance of trees from the emitters, the position of sites in relation to the direction of wind carrying pollutants, the age of trees and habitat conditions in which trees grow (Carrer and Urbinati, 2004; Yu
A significant influence of the climatic conditions of the current and previous year on pine radial increments was observed. This is confirmed by numerous dendroclimatic studies on Scots pine (Vaganov, 1990; Lührte, 1991; Richter
A strong positive correlation of site chronologies with the first main component indicates that pines showed similar sensitivity to climatic influences of PC1. Their role in shaping thickness increment of pines was independent of other elements of the environment. The results indicate that a cool, humid and rainy September meant that all the pine populations increased their increments in the following year. High temperatures and low air humidity in the autumn has a positive effect on the flowering of female flowers in the following year (Andersson, 1965; Fober, 1976). This has a negative impact on incremental growth of trees (Eis
The determination of properties of tree-rings is crucial for many applications in the investigation of local and global environmental changes. Since the beginning of the 20th century, there has been much discussion about how external environmental factors, including climate changes and anthropogenic effects affect the physiological processes that control tree growth (Schweingruber, 1996; DeVries
The carbon isotopic composition (δ13C) of trees has been influenced by carbon isotopic composition of atmospheric CO2, diffusion of CO2 through stomata, and enzymatic discrimination during the irreversible step of CO2 fixation (Roden
Trees grown at the higher level of CO2 concentration had a more negative δ13C than trees grown at the lower concentration. In pine, CO2 usually limits photosynthesis and, thus, an increase in CO2 results in greater photosynthetic rates. Raw δ13C data can be corrected to a preindustrial atmospheric δ13Ccor base value of 6.4% using the data from McCarroll and Loader (2004), due to decreasing δ13C in the air and the biosphere is associated with the increasing of anthropogenic CO2 in the atmosphere (Craig, 1954; Farquhar and Lloyd, 1993; Field
Researchers have used correlation analyses to determine which environmental parameters (precipitation, sunshine, humidity, and temperature) might be recorded in the isotopic composition of cellulose extracted from the annual growth rings (Schiegl, 1974; Gray and Thompson, 1976; Epstein and Yapp, 1977; Burk and Stuiver, 1981).
According to the scientific literature, the carbon isotopic composition in plant can vary with water stress and solar radiation and can be correlated with amount of rainfall, vapour pressure deficit, canopy position and hydraulic conductivity associated with tree height (Dongmann
According to models (Farquhar and Lloyd, 1993; Scheidegger
A negative δ18O-δ13C relationship could be regarded as an indication that plants have stomata with a limited operational range (Scheidegger
Spatial variability and temporal trends in water-use efficiency of European forests up until 2000AD has been studied in several tree species. Experimental results show that plants are able to increase their water-use efficiency (WUE) as CO2 levels rise (Ehlelinger
The studied populations of Scots pine showed sensitivity to a wide range of meteorological factors occurring in a climate window covering the previous and current ring-forming year. Although pine is a boreal species, cold and long winters have a negative impact on its incremental activity. This relationship holds over the entire geographical range where pines can be found. Industrial pollution caused a reduction in the incremental growth of pines, but this fact does not have a significant impact on its short-term incremental sensitivity. Thanks to the above, a clear climate-radial increment relation was observed.
However, incremental rhythm of the studied pine populations was not identical. This was due to their different sensitivities to some factors of the climate. It was not possible, however, to unambiguously specify the factor that modified the relationship between climate and incremental growth in trees on particular sites. A different degree of the pollution pressure on trees might possibly be a factor shaping their different sensitivity to particular meteorological factors. These could also be other environmental factors. In order to obtain a reliable model based on the relationship between climate and incremental growth for this species, many different subpopulations should be studied on a given area. The principal component analysis proved to be an effective tool in identifying climate factors having a similar and different impact on the incremental rhythm of the studied pines.
The isotopic records in tree-rings can be a sensitive bio-indicators of the way that the components of air and water have been changed by the trees in response to the environments in which they grown. The carbon isotopic composition of trees has been influenced by carbon isotopic composition of atmospheric CO2. Also, the impact of weather conditions on the isotopic concentration in pine has been observed. The most significant climate factors influencing δ13Ccor are the monthly humidity and sunshine in summer. Whereas the most significant climate factors influencing δ18O in the investigated area was the mean of the May monthly maximum temperatures.
Based on measurements of δ18O and δ13C in two periods of time (1) prior to 1990s (where high pollution also recorded in tree ring width reduction) in and (2) after 1990s’ (when the pollution was reduced). Only in the period of time between 1990–2012, δ13C and δ18O showed a positive significant correlation that indicated a strong stomatal reaction, whereas Amax was relatively unaffected. It has been observed that water use efficiency might be strongly correlated with variability of the global surface temperature due to increase of global CO2 emission. The analysis of the influence of variability of the global surface temperature due to the increase of global CO2 anthropogenic emissions on WUE will be a subject of future study.