The influence of climate and soil properties on calcium nutrition and vitality of silver fir (Abies alba Mill.)

Environmental Pollution 137 (2005) 596e602

www.elsevier.com/locate/envpol

The influence of climate and soil properties on calciumnutrition and vitality of silver fir (Abies alba Mill.)

Nenad Poto�cic a,*, Tomislav Cosic b, Ivan Pilas a

a Forest Research Institute, Jastrebarsko, Cvjetno naselje 41, 10450 Jastrebarsko, Croatiab Faculty of Agriculture, University of Zagreb, Svetosimunska 25, 10002 Zagreb, Croatia

Received 10 December 2004; accepted 31 January 2005

Dry years, especially in combination with calcium-poor soils, have astrong negative effect on the Ca status of silver fir trees.

Abstract

As a part of a broader research into the nutrition of silver fir (Abies alba Mill.), the variation of calcium concentrations was

investigated in needles and soil in two subsequent, climatologically diverse years. Statistically significant differences between plotswere determined in Ca concentrations in soils. Concentrations of Ca in needles were statistically different regarding plot, defoliationclass, sampling date within the same year and also between years. Fir trees on acid-rock based soils had lower, often inadequateconcentrations of Ca in needles; the opposite was true for trees growing on Ca-rich soils. Trees of lower vitality generally exhibited

poor Ca nutrition. Drought in the second year of research caused poor absorption of Ca on all plots and in all defoliation classes,but the combined influence of climate and soil properties affected especially trees of low vitality on acid-rock based soils.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Calcium; Silver fir; Defoliation; Drought; Soil properties

1. Introduction

Silver fir (Abies alba Mill.) is a species with a longhistory of dieback throughout Europe. A widespreadsymptom of damage of silver fir in the central andnorthern Europe is crown defoliation resulting fromboth an above-average loss of older sets of needles andan insufficient branching (Gruber, 1994). It was firstrecorded in France, Slovenia and Croatia in the year1900, with repeated reports until the present day (Bati�c,1930; Safar, 1951; Androic and Klepac, 1969; Kri�zaj,1997 etc.). Silver fir is the most widely distributed andimportant coniferous species in Croatia: it participates

* Corresponding author. Tel.: C385 1 6273027; fax: C385 1

6273035.

E-mail address: [email protected] (N. Poto�cic).

0269-7491/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.envpol.2005.01.045

with 9.4% in the growing stock of all the croatian forests(Mestrovic, 2001). Due to its major ecological andeconomical importance, the deteriorating health statusof silver fir in the recent years is a matter of greatconcern. The share of moderately to severely damagedtrees (crown defoliationO 25%) has gone up from51.8% in the year 1999 to 70.1% in 2000, and has sinceremained at around 70% (Seletkovic and Poto�cic, 2004).In the same period, the average for Europe has beenmuch lower at about 50% of moderately to severelydamaged silver fir trees (UNeECE and EC, 2003).

Calcium is an essential macronutrient responsible forthe structural and physiological stability of plant tissuesand regulation of metabolic processes at cellular andtissue level (Bergmann, 1992). Fertilization with Caimproves needle retention of silver fir trees (Bonneauet al., 1990). The specific circumstances that explain this

597N. Poto�cic et al. / Environmental Pollution 137 (2005) 596e602

positive Ca effect remain to be clearly identified (Land-mann et al., 1995). Huettl (1989, 1990) states that allsymptoms of dieback of forest trees are linked toa certain degree to nutrient deficiencies, with lowavailability of nutrients in forest soils a predisposingfactor. The links of defoliation to the levels of exchange-able cations, especially calcium, are reported by Seidling(2000). Stefan (1993) and Werther and Havranek (1999)state that nutrient-poor soils and drought cause thedeterioration of forest condition. Trees exposed todrought decreased the needle amount in the study ofNilsson and Wiklund (1992). Nutritional and physio-logical disturbances caused by rainfall deficits areconsidered to be the reason for the decay of Pyreneansilver fir stands (Fromard et al., 1991). Drought periodsare stressed as one of the major damaging factors for thehealth status of silver fir (UNeECE and EC, 2003).

The aim of this research was to assess the influence ofsoil chemistry and unfavourable climatic conditions onthe calcium status of silver fir trees and to compare theresponse of healthy, damaged and severely damagedtrees.

2. Materials and methods

2.1. Plot description

The research was conducted on five plots (Fig. 1,Table 1), 100! 100 m each, characterized by differentparent rock and soil types (FAO, 1998): plot Sljeme (SL)with dystric umbric cambisol on greenschist parent rock,plot Belevine (BE) with umbric skeletic podzol andsandstone parent rock, plot Kupja�cki vrh (KV) with

Fig. 1. Map of Croatia with the locations of experimental plots.

luvic cromic cambisol on limestone, plot Leska S (LS)with spodic luvisol on sandstone and plot Leska D (LD)with luvisol skeletic soil type on dolomite parent rock.

2.2. Climatological data

The data from Delnice COB meteorological station(established 1993) of the State Meteorological andHydrological Service were used to describe the climateproperties in the two experimental years, 1999 and 2000,and the period 1993e2000.

2.3. Field work

Defoliation of fir trees (Kraft classes 1, 2 and 3) onthe research plots was assessed according to PCC(1988). The trees were then assigned to defoliationclasses (!25% defoliation e healthy, 26e60% edamaged, O60% e severely damaged). Nine trees ineach defoliation class were randomly selected forsampling, 27 trees per plot. Current-season andprevious-season shoots were sampled monthly fromthe upper third of the crown, June to October 1999 and2000, and pooled into a composite sample for eachdefoliation class. In 1999, samples for June and Julywere taken together.

From June to October 2000, three soil cores weresampled from the depths of 0 to 30 cm and 30 to 60 cmin the center and in the four corners of every plot andcombined into composite samples, giving a total of fivecomposite samples per plot for each depth.

2.4. Laboratory analyses

Needles were dried (105 �C, 48 h), finely ground andwet digested using concentrated sulfuric acid withHClO4 as catalyst. Ca was determined from the filtrateby AAS (AOAC, 1996) on a dry-matter basis.

Exchangeable Ca2C in the composite soil sampleswas determined according to Thomas (1982).

2.5. Data analyses

Data were analysed with the help of Statistica 5.5(StatSoft, Inc., 1995) statistical package. Since theobtained data were time series and therefore notfollowing normal distribution, non-parametric tests(KruskaleWallis ANOVA by Ranks and Median test)were used for statistical analysis of plot differences anddefoliation-class differences.

For evaluation of foliar Ca concentrations, wecompared them to a limit value (lowest adequate value)of 4.0 mg/g dry matter (Bergmann, 1992; Landmannet al., 1995).

598 N. Poto�cic et al. / Environmental Pollution 137 (2005) 596e602

Table 1

Experimental plots e basic data

Plot Altitude (m) Latitude Longitude Forest type

Sljeme 950 45 54# 57$ N 15 59# 39$ E Beech and fir forest

Belevine 800 45 23# 07$ N 14 52# 08$ E Fir forest

with hard fern

Kupja�cki vrh 980 45 24# 31$ N 14 53# 04$ E Beech and fir forest

Leska S 690 45 24# 01$ N 14 38# 60$ E Fir forest

with hard fern

Leska D 710 45 26# 25$ N 14 39# 30$ E Beech and fir forest

3. Results

3.1. Climate properties

Climate diagrams (Fig. 2) following the design byWalter and Lieth (1960) show the differences in climateproperties between the two experimental years. Al-though the sum of precipitation in the year 2000(Fig. 2c) was above average for the period 1993e2000(Fig. 2a), the pattern of precipitation was different,resulting in a period of drought in August 2000. Thedata on precipitation in the growing season for the years1999 and 2000, when compared to the mean for theperiod 1994e2000, further confirm the unfavourableclimatic conditions in the year 2000 (Table 2).

3.2. Exchangeable Ca concentrations

Significant plot differences ( p! 0.01) were estab-lished in soil Ca concentrations for both 0e30 cm and30e60 cm sampling depths (Fig. 3). The lowest ex-changeable Ca was found in the soil cores from plotsBelevine (BE) and Leska S (LS), highest on plotsKupja�cki vrh (KV) and Leska D (LD), while the soil onplot Sljeme (SL) had intermediate Ca concentrations.The variations in exchangeable Ca concentrations werehighest on plot LD.

3.3. Needle Ca concentrations

3.3.1. Sampling timeAs expected, the variation of Ca concentrations is

more pronounced with current-season needles, whereasthe concentrations are higher in previous-season nee-dles. Year 2000 was unfavourable for Ca nutrition: thevariation of concentrations was much less pronouncedthan in 1999. Accumulation of Ca was insignificant(compare Fig. 4a and b).

3.3.2. Defoliation classThe differences in needle Ca concentrations of fir

trees belonging to different defoliation classes are muchlarger with previous-season needles than with current-season needles. In the year 1999 these differences aresignificant on plots BE and LD at p! 0.05, with Caconcentrations higher in lower defoliation classes(Fig. 5a,b). With other three plots these differences existbetween lowest and highest defoliation class.

With values very low in all defoliation classes, nosignificant differences were found in Ca concentrationsin the year 2000. Still, the same trend can be observed,especially on plots BE and LD (Fig. 5c, d).

3.3.2. Plot differencesCurrent-season needles of fir trees are Ca deficient in

the year 1999 on plots with low exchangeable Ca, BE

Fig. 2. Climate diagrams, meteorological station Delnice COB, (a) years 1993e2000, (b) year 1999 and (c) year 2000.

599N. Poto�cic et al. / Environmental Pollution 137 (2005) 596e602

and LS (Fig. 6a). While on plot BE trees with lowdefoliation (0e25%) accumulated Ca above the set limitvalue, on plot LS the nutrition of all trees wasinadequate. In previous-season needles, plot differencesare significant at p! 0.05. Nevertheless, needle Caconcentrations are satisfactory on all plots and evendamaged trees on plots BE and LS have reachedadequate needle Ca concentrations (Fig. 6b).

Regardless of plot soil properties, in the followingyear severely damaged trees were only able to reachconcentrations not higher than limit value in current-season needles (Fig. 6c). In previous-season needles, lowvitality trees (O60% defoliation) on 3 out of 5 plotsexhibited very low Ca concentrations (Fig. 6d), reachingsatisfactory values late into the growing season. Cauptake was minimal on all plots, with values not muchhigher than in current-season needles in 1999.

4. Discussion

Calcium is fairly immobile in plants, therefore Cadeficiency symptoms can be first observed in thegrowing tips and youngest leaves. General chlorosis isfollowed by necrosis of needles, especially at branch tips,and in severe cases, death of terminal bud and topdieback. Typical features of senescence are similar tothose of Ca deficiency and can be retarded by Ca2C

(Mengel and Kirkby, 1987).

Table 2

Precipitation (mm/m2) in the period AprileSeptember, meteorological

station Delnice COB

Year April May June July August SeptemberP

1994e

1998

170.7 151.0 144.2 91.0 130.7 199.4 887.0

1999 296.2 153.4 74.1 191.0 37.3 133.0 885.0

2000 70.8 55.2 40.2 163.1 5.3 165.7 500.3

The availability of calcium to plants is mainlydetermined by the amounts of Ca2C ions held inexchangeable form (Vanmechelen et al., 1997). Differentsoil types on our research plots are characterized bysignificantly different concentrations of exchangeableCa. The lowest concentrations were established in thesandstone-based soils of plots BE and LS. On plot KV,the concentrations of Ca are higher in the 30e60 cmsample depth due to the shallow limestone parent rock.Large differences in Ca concentrations regarding thesample depth were established in deep luvisol of LD plotdue to the variability of parent rock position in the soilprofile.

Inadequate Ca nutrition in the year 1999 wasrecorded in the current-season needles on plots BEand LS, characterized by Ca-poor soils. Kaupenjohannet al. (1989) report that calcium needle concentrations insilver fir needles at sites with acid soils are significantlylower than those on calcareous soils. Similar to theresearch of Komlenovic and Cestar (1981) and Land-mann et al. (1995) on silver fir, Fernandez et al. (1990)on balsam fir and red spruce and Helmisaari (1992) onScots pine, we observed an increase in Ca concentrationsover the growing season in both current and previous-season foliage, reflecting the accumulation of Ca duringprogressive maturation of needles. Vitality-related dif-ferences in Ca concentrations were discernible incurrent-season needles, but trees of different defoliationclasses were clearly differentiated by Ca concentrationsin previous-season needles. A correlation of needle lossand low Ca concentrations in the foliage of silver fir isalso reported by Komlenovic et al. (1991), Komlenovicand Rastovski (1992), and for Norway spruce byKatzensteiner et al. (1992) and Frey and Frey (1993).The effect of vitality on Ca status is apparent from thestatistical analysis of plot-related differences: the differ-ences were significant for tress in defoliation classes 26e60% and over 60%, whereas healthy trees had adequateCa concentrations regardless of the edaphic conditions.

Min-MaxMedian value

PLOT

mg/

kg

0

400

800

1200

1600

2000

2400

SL

a

BE KV LS LDMin-MaxMedian value

PLOT

0

400

800

1200

1600

2000

2400

mg/

kg

b

SL BE KV LS LD

Fig. 3. Exchangeable Ca concentrations in the soil cores, (a) depth up to 30 cm (KruskaleWallis test: pZ 0.0002), (b) depth 30e60 cm (Kruskale

Wallis test: pZ 0.0005).

600 N. Poto�cic et al. / Environmental Pollution 137 (2005) 596e602

Min-MaxMedian value

a

MONTH

mg/

g

0123456789

101112

XVI_VII VIII IX

mg/

g

Min-MaxMedian value

b

MONTH

0123456789

101112

XVIIIVIIVI IX

Fig. 4. Variation of previous-season needle Ca concentrations, defoliation 0e25%, all plots, (a) year 1999, (b) year 2000.

The variation of needle Ca concentrations in thefollowing, dry year was less pronounced, and theconcentrations were generally lower. Barely adequateCa concentrations in current-season needles werereached late into the season. According to Bergmann(1992), the uptake of Ca is negatively affected byirregular water supply and, in particular, prolonged dryperiods. This is in contrast with research results of Stefanand Gabler (1998) who found that drought had the

opposite effect in Norway spruce, and points to the needfor further research. The sequence of drought-inducedphysiological disturbances that lead to the dieback oftrees is largely unresolved (Landmann et al., 1995). Apossible interpretation is that extreme climatic incidentsset off the decline, while natural variation in the localenvironment acts as a catalyst for the severity of thedecline (Strand, 1997). The Ca concentrations in silver firneedles were again lower on the plots with Ca-poor soils,

Min-MaxMedian value

a

DEFOLIATION

mg/

g

0123456789

101112

>60%<25% 26-60%

mg/

g

Min-MaxMedian value

c

DEFOLIATION

0123456789

101112

>60%<25% 26-60%

mg/

g

Min-MaxMedian value

b

DEFOLIATION

0123456789

101112

>60%<25% 26-60%

mg/

g

Min-MaxMedian value

d

DEFOLIATION

0123456789

101112

>60%<25% 26-60%

Fig. 5. Ca concentrations in previous-season needles, different defoliation classes: (a) plot BE, year 1999 (KruskaleWallis test: pZ 0.0252), (b) plot

LD, year 1999 (Median test: pZ 0.0498), (c) plot BE, year 2000, (d) plot LD, year 2000.

601N. Poto�cic et al. / Environmental Pollution 137 (2005) 596e602

Fig. 6. Plot-related differences of Ca concentrations: (a) year 1999, current-season needles, defoliation O 60%, (b) year 1999, previous-season

needles, defoliationO 60% (KruskaleWallis test: pZ 0.0134), (c) year 2000, current-season needles, defoliationO 60%, (d) year 2000, previous-

season needles, defoliationO 60% (KruskaleWallis test: pZ 0.0213).

but plot-related differences were restricted to the severelydamaged trees, indicating the higher drought-resistancecapacity of healthier silver fir trees. Due to theexceptionally low Ca concentrations, defoliation class-induced differences were no longer present, but in-adequate Ca nutrition was most pronounced in the leastvital trees, as was in the previous year. According toSimon and Wild (1998), if the concentration of a certainelement remains in the normal range, the decrease inmineral nutrition should be regarded more as a conse-quence than the cause of damage. If, on the other hand,the concentrations are inadequate, we can suspectnutrition to be the cause of damage.

The experimental data presented here show that dryperiods greatly influence the Ca status of silver fir. Itseems that silver fir trees need a relatively high Casupply to maintain healthy growth (Komlenovic andCestar, 1981). Acting as a counterpart to potassium,calcium plays a key role in the stomatal movement andregulation of water balance of trees (Marigo and Peltier,1996; Raghavendra, 1998). It is now well established theaction of ABA on stomatal closure depends on thecalcium concentrations in the leaf epidermis (Atkinsonet al., 1990). This makes an adequate calcium nutritiona necessity, even more so during dry periods.

5. Conclusions

In this study soil and climate properties have beenidentified as the decisive factors determining the Castatus of silver fir trees, the combination of drought andCa-poor soils having the strongest negative effect. Thedifferences in climate properties between years werestrongly reflected in silver fir calcium nutrition. Droughtcaused low needle Ca concentrations on all plots andin all defoliation classes, but dry conditions affectedespecially trees of low vitality on acid-rock based soils.

Acknowledgements

Our thanks go to the State Meteorological andHydrological Service for the use of their data and thestaff of the Pedological laboratory of the Forestryfaculty, University of Zagreb, Croatia, for the help inpreparation of soil samples.

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