ВОЗДЕЙСТВИЕ ТЕМПЕРАТУРЫ И ОСАДКОВ НА ЛИНЕЙНЫЙ ПРИРОСТ СОСНЫ ПОБЕРЕЖЬЯ КАНДАЛАКШСКОГО ЗАЛИВА

Позднякова Е.А.¹, Волков А.А.², Кухта А.Е.³

¹Аспирант, ²студент, ³кандидат биологических наук, ¹исполняющая обязанности младшего научного сотрудника, ²инженер, ³заведующей лабораторией, «Институт глобального климата Федеральной службы по гидрометеорологии и мониторингу окружающей среды России и российской академии наук»

ВОЗДЕЙСТВИЕ ТЕМПЕРАТУРЫ И ОСАДКОВ НА ЛИНЕЙНЫЙ ПРИРОСТ СОСНЫ ПОБЕРЕЖЬЯ КАНДАЛАКШСКОГО ЗАЛИВА

Аннотация

В статье представлена зависимость линейного прироста сосны обыкновенной (Pinus sylvestris L.), произрастающей в сухих,  свежих и влажных биотопах на территории Кандалакшского Государственного природного Заповедника и Государственного заказника «полярный круг»   Мурманской области от серии климатических факторов. Использовались стандартные дендрохронологические методы. Результаты показали, что для исследуемых древостоев не было выявлено общей зависимости линейного прироста от температуры. Таким образом температурный фактор не может рассматриваться в качестве лимитирующего для данных биотопов.  Установлено, что лимитирующим фактором линейного прироста сосны обыкновенной для сухих и влажных биотопов является содержание влаги в почве. Лимитирующий фактор  для свежих биотопов не был установлен, потому что это региональный оптимум для P. sylvestris.

Ключевые слова: сосновый подлесок, прирост, временной ход прироста, метеорологические факторы.

Pozdnyakova Е.А.¹, Volkov А.А.², Koukhta А.Е.³

¹ Postgraduate student, ² student, ³ Phd in biology, ¹Junior researcher, ²engineer, ³head of laboratory, Institute of Global Climate and Ecology of  Federal service for Hydrometeorology and environmental monitoring of Russia and Russian Academy of Sciences

EFFECT OF TEMPERATURE AND PRECIPITATION ON THE ANNUAL HEIGHT INCREMENT OF SCOTS PINE ON THE KANDALAKSHA GULF COAST

Abstract

The dependence of tree height increment on series of climatic variables during the growing season has been analyzed in Scots pine (Pinus sylvestris L.) growing in dry, mesic, and moist biotopes in the Kandalaksha State Nature Reserve and Polarny Krug (Arctic Circle) Local Nature Reserve, Murmansk oblast. Standard dendrochronological methods were used. The results showed that there was not common response of height increment to temperature across all these biotopes.  So the temperature factor was treated as not limiting in this kind of ecosystems.  Soil moisture content proved to be the main limiting factor of the tree height increment in dry and moist biotopes. Limiting factors impact in mesic biotopes were not registered because it was a regional optimum for P. sylvestris.

Keywords: pine undergrowth, height increment, time course of growth,  meteorological factors.

Introduction

The process of plant growth strongly depends climatic factors. In particular, published data provide evidence for a close dependence of shoot and root growth, photosynthesis, and production of trees on temperature and accessible moisture supply [1, 2, 3 ,4, 5]. There are numerous dendrochronological investigations and issues concerning hight and radial tree increment response to meteorological factors impact. It is shown that there is a tight connection between time course of growth characteristics and total precipitation [5, 6, 7, 8, 9].

Most dendrochronological works consider mature trees; and  the undergrowth aspect is usually not in the focus of interest of dendrologists. Our issue deals with pine undergrowth as far as it is a suitable object to collect a data massive; furthermore it does not require sample trees cutting for tree height and internodes length measuring. Resulting dendrochronological data permit to reconstruct former forest stands life conditions and trees response to climatic impacts.

The main objective of this studied to analyze the dependence of Scots pine undergrowth height increment on temperature and precipitation variability in the current and previous years and to identify climatic factors that are most important for the development of Scots pine undergrowth on Kandalaksha Gulf Coast, the White Sea (Murmansk region).

Murmansk region  in the Arctic Atlantic province and has temperate climatic belt. Its marine climate is largely formed under the effect of the warm Murman Current, which accounts for excessive moistening in the region [10]. In phytogeographic (floristic) terms, the coasts and islands of Kandalaksha Gulf lie in the Eurasian taiga zone, in the Kola–Pechora subprovince of the Northern European floristic province, at the junction of the Imandra, Varzuga, and Topozero floristic regions [11]. Northern taiga forests are the main vegetation type in the area [10, 11, 12].

Materials and Methods

The studied area  at the vicinities of Gorodetsky Ledge on Veliky Island (the Kandalaksha State Nature Reserve) in September 2000 and  at the vicinities of the White Sea Biological Station, Moscow State University (WSBS),  on Cape Kindo (the Polarny Krug Local Nature Reserve) in September 2007 (Fig. 1). Measurements of Scots pine (Pinus sylvestris L.) undergrowth height increments used procedure of our previous issues [13, 14] in moist, mesic and dry biotops of Cape Kindo and in mesic and dry biotops of Veliky Island (as far as there are not wetlands within our sample site on the island). The sampling was fulfilled in different years, the received two data bases  were quite compatible: tree chronologies conjugacy  was a usual dendrochronological method in reconstructing the climatic conditions of the past [6, 9].

Fig. 1 - Schematic map of the study region, including Veliky Island (the Kandalaksha State Nature Reserve) and Cape Kindo (Polarny Krug (Arctic Circle) Local Nature Reserve)

The pine undergrowth was the investigation object. The object trees were not older than 7 years and not above 2.5 m. All stem internodes on each sample tree were measured beginning from the apical one. The values were in millimeters. The tree height was measured too. The trees were chosen on sample plots (the plot diameter did not exceed 50 m) with the same growth conditions and sustainable pine reproduction. The route survey method was used to establish sample plots. In total 45 sample plots (225 trees, 5 trees on each plot) were  chosen in moist, mesic and dry biotops.

A procedure of annual absolute increment values divided  in 5 year moving average was used to obtain increment indices ranges. As a result of this procedure we received each tree individual chronologies. Then individual ranges were averaged by plots; so the undergrowth stand generalized characteristics for different biotops were obtained.

The statistic analysis was  used the Openoffice Calc. The relationships between increment ranges and meteorological variables were assessed by means of correlation analysis  to estimate the degree of dependence of interannual fluctuations in tree height increment on climatic factors. The Pearson correlation coefficient was calculated; the confidence level was identified according to the manual [15].

Height increment responses to climatic factors were evaluated from the degree of variability in the time course of growth. This parameter was determined by analyzing the time series of annual height increments that were smoothed by a 5-year sliding mean to eliminate the age trend. The relationships between these series and meteorological variables were assessed by means of correlation analysis to estimate the degree of dependence of interannual fluctuations in tree height increment on climatic factors. The Pearson correlation coefficient was used, and correlation significance was identified with the help of a manual [15].

Climatic factors considered in the study were anomalies of monthly average temperature and total precipitation, i.e., deviations of these parameters from long-term average values. An anomaly is a numerical value which indicates how far a measurement varies from the average. The average is determined from a period of weather observation [16]. To reveal the climatic component of variability in the time course of tree growth, analysis was made of meteorological anomalies in March, April, May, June, July, August, and September of the current and previous years. It was necessary to include in analysis meteorological data on the previous year, because the current height increment depends on the size and quality of the apical bud initiated last year and on the amount of needles formed in previous years, which have a donor function for the growing apical shoot [5, 17]. The data massive of the Federal Service for Hydrometeorology and Environmental Monitoring of Russia (Roshydromet) [18] hydrometeorological station “Kandalaksha” was used in the issue.

From the biocenotic standpoint, the studied region was characterized by a high biotope diversity, because it abounds in rock outcrops, gorges, depressions, etc. Abundant climatic moistening provides favorable conditions for waterlogging in topographic depressions (moist biotopes), while areas with elevated topography are often subject to moisture deficit (dry habitats), since a thin layer of loose deposits formed on bedrocks cannot effectively retain precipitation falling on slopes [11, 12].

A total of 175 young Scots pine trees were measured in dry, mesic, and moist biotopes characteristic of the Kandalaksha Gulf coasts. A brief description of these biotopes is given below.

Dry biotopes. Pine rock forest is the most typical forest type on rock outcrops, where the soil cover is almost absent, as well as on the tops of well-drained glacial hills and ridges and on ancient alluvial marine terraces. Since the ground vegetation layer in such forests consists mainly of reindeer lichens (often referred to as white moss), they are usually named white moss pine forests.

Mesic biotopes. Smooth plateaus and the upper parts of slopes are usually covered by cowberry pine forests, with bilberry pine forests prevailing in the middle and basal parts of the slopes. Dwarf shrubs growing under the tree canopy include cowberry (Vaccinum vitis-idaea L.), bilberry (Vaccinum mytrillus L.), and black crowberry (Empetrum nigrum L.). The soil is covered by a continuous layer of mesophytic green mosses, mostly of the genera Pleurozium, Hylocomium, and Dicranum.

Moist biotopes. Areas with excessive (but not stagnant) moisture supply (at slope bases, in depressions, around lakes and bogs, etc.) are characterized by dominance of hygrophytic mosses (mainly Sphagnum spp.) in sites with depressed microtopography, while microelevations (hummocks) are occupies by green mosses and dwarf shrubs: wild rosemary (Ledum palustre L.), bog bilberry (Vaccinium uliginosim L.), common bilberry, and, less frequently, cowberry and black crowberry. As the degree of swamping increases, Sphagnum mosses ascend the hummocks and eventually occupy their entire surface. At the same time, berry-bearing dwarf shrubs decrease in abundance and give place to typical bog species such as cloudberry (Rubus chamaemorus L.), cranberry (Oxycoccus palustris L.), purple marshlocks (Comarum palustre L.), buckbean (Menyanthes trifoliata L.), and various sedges (Carex spp.) [10, 11, 12].

Shallow depressions on rock outcrops are permanently filled with atmospheric water, which cannot flow out because the underlying rocks are impermeable to it. The vegetation developing in such micropools consists mainly of bog species, such as Sphagnum mosses, leatherleaf (Chamaedaphne calyculata L.), etc. Therefore, they are also included in the group of moist biotopes, despite their location amid cenoses characteristic of well-drained areas.

Results and Discussion

The first step of this studied to find out  what extent Scots pine stands on Veliky Island and Cape Kindo are similar  with the pattern of variability in the time course of growth. For this purpose, correlation analysis was performed for the averaged time series of height increment indices in the two areas (Figs. 2a, b). The results confirmed a significant positive correlation between these series: R = 0.496 at a 90% confidence level (hereinafter P= 0.05).

(a). Cumulative increment plots of  pine undergrowth height increment indices in moist, mesic and dry biotops as well as general averaged increment series on Veliky Island and Cape Kindo

(b). General averaged increment series on Veliky Island and Cape Kindo (two standard errors  are shown)

Fig. 2(a,b) - Averaged series of pine undergrowth height increment indices in tree stands on Veliky Island and Cape Kindo

The time series of Scots pine undergrowth height increment indices  on Veliky Island and Cape Kindo were similar to each other. In both cases, about 50%  variation  of tree growth was explained by climatic and cenotic conditions, which were almost identical in these areas. As it was mentioned earlier  the coasts and islands of Kandalaksha Gulf lie in the Eurasian taiga zone, in the Kola–Pechora subprovince of the Northern European floristic province; Northern taiga forests are the main vegetation type in the area [10, 11, 12]. Ecosystem parameters, including soil, hydrological and vegetation conditions, are homotipic in this region; properly, the plant conditions similarity was the reason that allowed to integrate these floristic aggregates  geobotanically.

On this basis, tree stands in dry, mesic, and moist biotopes on the two coasts of Kandalaksha Gulf could be regarded as structural components of the same biogeocenosis. The expected differences in their responses to meteorological factors impact appear to be due to individual variability and  local variety factors and accounted for  the complex topography area  (microclimatic and soil parameters, conditions of root competition, characteristics of insolation and surface drainage, etc). Therefore, correlation analysis was used as a method to eliminate "noise" caused by these factors and reveal the actual relationship between interannual fluctuations of tree height increment and meteorological variables.

Temperature

Moist biotopes. Table 1 shows the results of correlation analysis between the time series of height increment indices and meteorological variables.

Table 1 - Coefficients of correlation between series of height increment indices and meteorogical variables in moist biotopes on Cape Kindo

Month	Temperature		Precipitation
	current year	previous year	current year	previous year
March	0.474	0.154	0.071	0.122
April	–0.093	0.160	0.162	0.070
May	–0.011	0.078	0.135	–0.432
June	0.323	0.346	–0.686	–0.314
July	–0.034	–0.103	–0.415	0.027
August	–0.014	0.348	–0.313	–0.077
September	–0.114	0.046	0.317	0.092
October	–0.118	0.029	–0.061	–0.013

Tree height increments  have a significant positive correlation with temperature in March of the current year (R = 0.474). Significant negative correlations were revealed with precipitation in June and July of the current year (R = –0.686 and R = –0.415) and in May of the previous year (R = –0.432). These results agree with published data [5]. The positive correlation between tree increment indices and temperature anomalies in current March  was explained by the fact that heat supply to trees at the onset of the growing season must be sufficiently high for initiation of growth processes and development of vegetative organs. Negative correlations were observed between the series of height increment indices and anomalies of precipitation in the current year (at phenophases of internode growth and regeneration bud formation). This could be expected, since excessive environmental moisture is an adverse factor limiting the growth of shoots. A negative correlation was also noted for the phenophase of internode growth in the previous year. It is known that linear increments of Scots pine depend mainly on growing conditions in the previous year, whereas conditions of the current growing season can only accelerate or retard shoot growth [5, 17]. Therefore, a factor affecting the growth of internodes retards the development of next-year shoots. The results data of correlation analysis showed that excessive moisture supply is  a climatic factor in moist habitats. 3.2. Mesic biotopes. The results of correlation analysis between the time series of height increment indices and climatic variables in these biotopes are presented in Table 2.  

Table 2 - Coefficients of correlation between series of height increment indices and meteorological variables in mesic biotopes on Veliky Island and Cape Kindo

Veliky Island					Cape Kindo
Month	Temperature		Precipitation		Temperature Precipitation
	current year	previous year	current year	previous year	current year	previous year	current year	previous year
March	–0.224	0.286	–0.194	–0.060	–0.401	0.191	–0.313	0.213
April	0.333	–0.201	0.069	–0.156	0.042	0.145	–0.092	–0.002
May	0.067	0.063	0.145	0.068	–0.147	–0.320	0.120	–0.164
June	0.305	0.104	0.118	–0.291	0.206	0.027	–0.390	–0.215
July	–0.024	0.272	–0.155	–0.005	0.049	–0.116	–0.414	–0.013
August	–0.109	0.011	–0.325	0.091	–0.055	–0.126	–0.105	–0.134
September	–0.305	0.183	–0.166	0.001	–0.137	–0.267	0.241	–0.019
October	0.263	–0.096	0.072	0.209	0.431	0.398	0.013	–0.145

They show that pine stands growing in mesic biotopes on Veliky Island were characterized by a significant positive correlation of height increments with temperature anomalies in April of the current year (R = 0.333) and a negative correlation with precipitation in August (R = –0.325). On Cape Kindo, a negative correlation was revealed with anomalies of precipitation in June and July of the current year (R = –0.390 and R = –0.414).

The observed differences between the two areas in the responses of tree height increment to temperatures of the growing season  could be attributed to local variations of temperature regimes, which  were characteristic of territories with rock outcrops and a diverse spectrum of habitats.

In both studied areas, a negative correlation between the series of increment indices and anomalies of precipitation in June to August were revealed in the period of cessation of internode growth and formation of the regeneration bud. It should be noted that anomalies of precipitation in the previous growing season apparently had not effect on fluctuations in the time course of tree growth, which was evidence for a sufficient moisture supply to mesic biotopes in the region.

The relationship between fluctuations of height increment and meteorological variables in mesic biotopes of the studied region was characterized by a spectrum of parameters differing in sign and value. There was a high level of noise from indiviual variability of undergrowth and from local factors, which interferes with analysis of relevant general trends.

Dry biotopes. Probable relationships between the parameters of linear tree growth and climatic factors in dry biotopes were also evaluated by means of correlation analysis. Its results are presented in Table 3.

Table 3 - Coefficient of correlation between series of height increment indices and meteorological variables in dry biotopes on Veliky Island and Cape Kindo

Veliky Island					Cape Kindo
Month	Temperature		Precipitation		Temperature Precipitation
	current year	previous year	current year	previous year	current year	previous year	current year	previous year
March	–0.068	0.135	–0.491	0.276	–0.555	0.193	–0.162	–0.047
April	0.122	0.154	0.081	0.279	0.177	0.287	0.065	0.367
May	0.304	–0.058	–0.390	0.417	–0.115	–0.144	–0.005	–0.063
June	–0.114	0.105	–0.350	0.291	–0.008	0.090	0.243	–0.142
July	–0.485	0.127	0.184	–0.008	–0.067	–0.010	–0.207	–0.342
August	–0.184	–0.341	–0.158	–0.262	–0.031	–0.141	–0.177	–0.019
September	–0.069	0.077	–0.042	0.247	–0.179	–0.030	0.056	–0.094
October	0.106	0.216	0.063	0.289	0.295	–0.125	0.187	0.000

The time series of height increment indices in dry biotopes on Veliky Island were found to negatively correlate with monthly average temperatures in June of the current year (R = –0.485) and August of the previous year (R = –0.341). Negative correlations were revealed with anomalies of precipitation in March (R = –0.491), May (R = –0.390), and June (R = –0.350) of the current year, while the correlation with precipitation in previous May was positive (R = 0.417).

On Cape Kindo, fluctuations of height increments  of Scots pine undergrowth showed a significant negative correlation with temperature in March of the current year (R = –0.555). Coefficients of correlation with the amounts of monthly precipitation in the current year were low, indicating that this factor had not significant role in determining the pattern of annual height increments. However, a positive correlation with precipitation in previous April proved to be statistically significant (R = 0.367).

A specific feature of dry biotopes is  a rise in temperature leads to increasing moisture deficit. A negative correlation with temperature anomalies was revealed for increment indices at the phenophases of internode growth (in the current year) and regeneration bud formation (in the current and previous years).

Responsible factors of negative correlations between tree height increments and precipitation anomalies in June, July, and August of the current year remain unclear. Under conditions where moisture comes only from the atmosphere and  was in deficit, it could be expected that the corresponding correlation coefficients would be high and positive. However, it should be taken into account that conditions in dry biotopes of the studied region  were so specific  and the effects observed in them may well be unusual and even paradoxical. Thus, the soils of these biotopes are shallow and underlain by impervious rocks; therefore, most precipitation falling on their surface flows downslope and cause soil nutrient  leaching . As a consequence, the growth of internodes  was inhibited, which  was reflected in the results presented above.

The amount of moisture accessible to the vegetation on the Kandalaksha Gulf Coast depends primarily on atmospheric precipitation. Therefore, low precipitation  was stressful for Scots pine stands at any phenophase of the growing season. Success in passage through the phenophases of needle emergence and annual shoot growth largely contributes to the quality of primordial regeneration buds, which, in turn, had an effect on the growth of internodes in the next growing season. These factors apparently account for the positive correlations between the series of height increment indices and anomalies of precipitation in April and May of the previous year.

Conclusion

Studied on Scots pine undergrowth in the territories of Veliky Island (the Kandalaksha State Nature Reserve) and Cape Kindo (the Polarny Krug Local Nature Reserve) have shown that there was not common response of height increment to temperature among all tree stands studied. The results of analysis showed that the pattern of temperature dependence of tree height increment  was determined primarily by various local factors (in particular, microclimate).

The relationship between fluctuations of height increment and meteorological variables in mesic biotopes of the studied region  was characterized by a spectrum of parameters differing in sign and value. There  was a high level of noise from indiviual variability of undergrowth and from local factors, which interferes with analysis of relevant general trends. Apparently, soil moisture  was not the factor limiting tree growth in mesic biotopes. In contrast, this relationship in dry and moist biotopes  were fairly distinct: tree height increments showed statistically significant negative responses to water stress (developing at elevated temperatures) in dry biotopes and to excessive atmospheric moistening in moist habitats.

 Scots pine undergrowth condition either in sphagnum bogs or on coastal rock outcrops  were critical because of the excess of moisture in the former case and its deficit in the latter case. In such biotopes where trees  at the threshold of survival,  the  most important fractors for their growth can be revealed against the background of local noise and their relative significance can be evaluated. According to our data,  a factor for Scots pine  survive in dry and moist biotopes on the Kandalaksha Gulf coast  was atmospheric precipitation (its deficit or excess).

Acknowledgments

The author is grateful to colleagues from the Institute of Global Climate and Ecology Dr. Esther Ran'kova for the meteorological data she kindly supplied and to Alexey Volkov for the map creating.