This article was downloaded by: [Stony Brook University]On: 19 October 2014, At: 07:11Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK

GranaPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/sgra20

Trends of some airborne tree pollen in the Nordiccountries and Austria, 1980—1993Siegfried Jäger a , Siwert Nilsson b , Britt Berggren b , Anna-Mari Pessi , MarjoHelander a & Hallvard Ramfjord da ENT Clinic, University of Vienna , Vienna, Austriab Palynological Laboratory, Swedish Museum of Natural History , S-104 05,Stockholm, Swedenc Department of Biology , University of Turku , Aerobiology Unit, Turku, FIN-20014,Finlandd Department of Botany , University of Trondheim , Dragvoll, N-7055, NorwayPublished online: 01 Sep 2009.

To cite this article: Siegfried Jäger , Siwert Nilsson , Britt Berggren , Anna-Mari Pessi , Marjo Helander & HallvardRamfjord (1996) Trends of some airborne tree pollen in the Nordic countries and Austria, 1980—1993, Grana, 35:3,171-178, DOI: 10.1080/00173139609429078

To link to this article: http://dx.doi.org/10.1080/00173139609429078

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensorsmake no representations or warranties whatsoever as to the accuracy, completeness, or suitabilityfor any purpose of the Content. Any opinions and views expressed in this publication are the opinionsand views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy ofthe Content should not be relied upon and should be independently verified with primary sources ofinformation. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands,costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial orsystematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution inany form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Grana: 35: 171-178, 1996

Trends of some airborne tree pollen in the Nordic countries and Austria, 1980-1 993 A comparison between Stockholm, Trondheim, Turku and Vienna

SIEGFRIED JAGER, SIWERT NILSSON, BRITT BERGGREN, ANNA-MAR1 P E W , MARJO HELANDER and HALLVARD RAMFJORD

JBger, S., Nilsson. S., Berggren, B., Pessi, A.-M., Helander, M. & Ramfjord, H. 1996. Trends of some airborne tree pollen in the Nordic countries and Austria, 1980-1993. A comparison between Stockholm, Trondheim, Turku and Vienna. - Grana 35: 171-178 ISSN 0017-3134.

Long term trends in the occurrence of airborne pollen might help in elucidating the probability or unlikelihood of developments which have been predicted in theory such as global warming or forest decline.

We have investigated and compared the trends over a 14 year period (1980-1993) of five selected common tree pollen types (Abiur, Corjliu, Betula, Piniu, and Ulnius) from three sites in North Europe (Stockholm, Trondheim, Turku) and one in Central Europe (Vienna) in terms of the start, peak, end, and duration of the season, peak values and annual totals, using data from the European pollen data bank. The existence of trends has been investigated by calculating correlation against years and the statistical significance of the regression lines has been examined at the 5% probability level (pt0.05).

A consistent trend in the earlier commencement of the flowering season is observed in all cases, as well as an earlier incidence of peak days. A marked trend to an earlier end of the season was also found in the majority of cases. In most cases, the length of the season showed a trend towards prolongation although this was not significant. Both the peak values and the annual totals exhibit clear trends towards higher values.

Since both the start of the season and peak days are primarily temperature-depcndant. the clear trends towards an earlier start and peak day in practically all the pollen types and sites examined supports the theory of global warming or, at least, a temporary rise in air temperature over the seasons covered by this investigation. The same conclusion can be drawn from the fact, that most of the trends of pollen frequency show an increase in the number of airborne pollen grains. It was not possible to comment on the possibility of forest decline, as there is insufficient knowledge on the influence of environmental factors on pollen production. Our material shows no trends which are distinct and consistent enough in terms of either decreasing or increasing annual totals or peak values to throw light on the question of forest decline. Sieg/ried Jciger, ENT Clinic, University of Vienna, Vienna, Atutria; Siwert Nilsson and Britt Berggren. Palynological Laboratory, Swedish hfiiseuni of Natural History, 9104 05 Stockliolni, Sweden; Anna- Afari Pessi and Afarjo Helander, Aerobiology Unit, Departnient of Biology, University of Turku, FIN- 20014 Turku, Finland; Hallvard Raiilfjord, Departnient of Botany, University of Trondlieini, N-7055 Dragroll, Norway. (Mamiscript accepted 4 Jiine 1996)

Since the European pollen data bank in Vienna contains a large amount of recent pollen data from many European sites, it is possible to make comparisons between different regions in terms of medium range trend analyses. In this study an attempt is made to detect trends for the start of the season, annual totals, peak days, time of maximum occur- rence and annual totals for five tree pollen taxa at four localities, Trondheim, Stockholm, Turku and Vienna. The questions of potential forest decline and global warming influenced the choice of taxa: Alnirs, is a common and widespread genus in central and northern Europe, and shows a wide variation with regard to flowering time and pollen production. The same is true of Curyltrs and Bettila. For these three genera the start of the pollen season is strongly influenced by temperature and their annual productivity seems to undergo a fairly distinct biennial fluctuation. Ultiius

is known for its vulnerability to parasitic diseases causing death. Pitrirs is significant in forest decline. With the exception of Pitius, all these taxa are also of allergological interest. Previous studies (Jager 1989, 1990, Jager et al. 1991) have shown that, to some extent, significant trends are to be expected.

MATERIAL AND METHODS

The location of the sampling sites and their elevation are shown in Fig. 1. At every site sampling was by means of Burkard traps. The distribution and frequency of the taxa is summarized in TableI. Daily pollen counts for Alnus, Coryliis, Betufa. Ulniiu and Pinus for the period 1980-1993 from Stockholm, Trondheim, Turku and Vienna, were extracted from the European pollen data bank by means of the European Aeroallergen Network Server (EANS). Annual totals and peak amounts have been calculated. The peak

0 1996 Scandinavian University Press. ISSN 0017-3131 Gram 35 ( I 996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

172 S. Jager et al.

Sampling sities:

Stockholm 59'21" 18'03'E 20 m a s I. Trondheim 63' 26' N 10" 26' E 58 rn a s I. TurLu 60' 32' N 22' 28' E 40 m a.s.1. Vienna 48' 14' N 16" 22' E I70 m a s 1.

a I 1. - abbe .m Ic\cl; a p. - P ~ C ground

Fig. 1. Sampling sites.

2Omag 4 m a g

I S m a g 2 0 m a g

day, i.e. the day with the highest value was also considered. In case of multiple peaks of equal height for the same taxon in the same year at a single station, the first occurrence was chosen as the peak day. The beginning of the pollen season (main pollen season) has been defined in different ways by different authors (Lejoly-Gabriel 1978, MuIIenders et al. 1972, Nilsson & Person 1981, Pathirane 1975). In this study, the onset of the pollen season was defined as the first day with a pollen amount exceeding 1% of the annual total, providing this was not followed by more than six consecutive days with zero values.

The end of the season was defined as the number of the day upon which 95% of the annual total was reached. The duration of season is the difference in days between the start and the end of the season.

In 1982, 1989 and 1990 sampling was started late in Trondheim. For this reason Aliiw, Corjlus and to some extent Ulnius are excluded from the Trondheim calculations for those years. Corylus occurs in very low quantities in Turku. It was not possible, therefore to determine the start of the season date for Corylus at that site in 1981, 1982, 1983, 1985 and 1988. In addition no Corylus pollen was trapped in Turku in 1988 which led to the elimination of this year from the calculation of the trends of the peak day for Corylus at that site. All other data sequences were complete and contained a full data sequence for 14 pars.

A simple correlation of the pollen values against the year was made, following the correlation coefficient evaluation described by Henryson (1957). The statistical significance was calculated to an error level of less than 5% (Table I). The slope coefficient (b) of the regression equations was tested for its Significant difference from 0 in order to verify the trends. These calculations were performed using SAS statistical software (Table 11).

The graphs have been constructed using a commercial graphic software package named FREE-LANCE.

RESULTS AND DISCUSSION

The trends selected include: (1) the beginning of the pollen season, (2) the time of the first peak day, (3) the end of the pollen season, ( 4 ) peak concentrations, (5) annual totals.

Grana 35 (1996)

Table I. Distribution and frequency of taxa.

***common**usual*rare (*)occasional

Taxa. Stockholm Trondheim Turku Vienna

* ** ** ** *** - *** *** Alnus incana

A. ghrtinosa A. viridis - -

C. coluriia - - Betula huinilis - B. pendula B. pubescens B. nana (*I Pinus cembra (*I

P. nigra (*I P. sylvestris t**

U h u s glabra ** t ** t

U. l a d s (*I U. minor (*I

.according to Ehrendorfer (1973) & Hrimet-Ahti et al. (1989)

(*)

(*I

(*I (*I (*I - - (*I (*I

(*I (*I +**

* *** (*I Corylio avellana ** ** *

- - *** *** *** *** *** *** ***

* * P. mugo - *** t** **

* *

- * - -

Trends in general

Corylus (Fig. 2). - The annual totals rise slightly in Stockholm and Turku and significantly in Vienna, although the annual totals for Coryliu are numerically very low in Turku. No distinct trend is seen in the Trondheim material. The peak concentrations follow these trends, but are not statistically significant. In Trondheim a slight trend towards lower peak values is even observed. There is a distinct trend towards a n earlier start of the season, which is statistically significant in Stockholm and Trondheim (note that values for five of the fourteen years are missing due to the low amount of Corylus pollen in Turku and Trondheim). Peak days show a trend towards occumng earlier in the year a t all the sites, this being significant in Stockholm and Turku. In Vienna, this trend is less pronounced. In correspondence with the trends towards a n earlier start and peak day, the end of the season also shows a trend towards occurring earlier in the year. Again, in Stockholm and Turku this trend is significant. The duration of the season consistently shows a slight trend towards prolongation, although this is not statistically significant.

Abzirs (Fig. 3). - The annual totals show n o mutual trend at all. A slight increase is observed in Vienna, while in Turku a faint trend decrease is detected. The peak concentration shows a slight downward trend in Turku but this is not significant. The onset of the season became significantly earlier during the period 1980 to 1993 in Stockholm, Trondheim and Turku, but this trend is not significant in Vienna. The peak day shows a similar trend towards the beginning of the year and this is statistically significant in Stockholm and Trondheim. The trend for the end of the season is towards occurring earlier in Trondheim, Stockholm and Vienna (the slope of the regression coefficient is very close t o being significant). In Turku the trend is similar t o that of the other sites but very weak. A trend towards an earlier end of the season is significant in Stockholm. In the

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

Pollen trena!s in Scandinavia and Vienna 173

Table 11. Trends in airborne tree pollen, 1980-1993. Significant trends (pt0.05) p-value for slope coefficient different from 0 0 ) the trend for the end of the Abiils season in Vienna was very close to significance (p=0.0502)

Sampling stations

raxa Trondheim Stockholm Turku Vienna

4biw total peak value start *p=O.O266 *p = 0.01 26 *p=0.0171 peak day *p =0.0449 *p = 0.0074 end *p=0.0386 0

Forjlus

3etula

total peak value start peak day end

total peak value start peak day end

total peak value start peak day end

'inw total peak value start peak day end

*p=0.0453

*p = 0.0224 *p =0.0298 *p=0.0333 *p=0.0361 *p = 0.0035

*p =0.0058

*p = 0.0267

*p=0.0203 *p=0.0161

*p=0.0687

*p = 0.0442

Jordic countries a weak trend towards a lengthening of the :ason is detected, whereas in Vienna a trend towards a horter season is found, though this is not significant.

Betirla (Fig. 4). -No significant trends exist with the single xception of a trend to an earlier end of the season in Vienna. .nnual totals show increasing trends in Scandinavia but no *end at all in Vienna. Relatively distinct, but not significant .ends are observed in higher peak values at all sites. The art of the season shows uniform trends to earlier in the :ar, this being more pronounced in the Nordic countries llthough still not significant) than in Vienna. A weak trend wards earlier peak days is seen in Stockholm and Vienna, hile in Trondheim and Turku no trend at all is visible. The id of the season inclines slightly towards a later date in rondheim and, more distinctly, towards an earlier date in tockholm, Turku, and Vienna. The Betula season obviously LOWS a trend towards longer duration in the Nordic coun- ies and towards shorter duration in Vienna.

Ulmtrs (Fig. 5). - The annual totals show no trend, or ily a slight trend,. towards lower values in Trondheim and .ockholm, and a trend towards higher values in Turku and ienna. Of these, the trend in Vienna is significant. The peak

days show exactly the same trends, with the exception, that the trend in Vienna is no longer significant. The onset of pollen dispersal reveals a general trend towards an earlier commencement of flowering, which is significant in Trondheim. The trends of the peak day show exactly the same pattern. There is no trend for the end of season in Trondheim, but there is a significant trend based on the correlation with an earlier end to the season in Stockholm. However, this has no significance for the regression slope (p =0.0687). This is the only occasion where the two methods showed different results. Weak trends have been detected in the same direction in Turku and Vienna. No distinct trends with regard to the duration of season are visible, with the exception of Trondheim, where a trend towards a longer season is obvious, but not significant.

Pinirs (Fig. 6). - The annual totals remain stable in Trondheim, there is a slight decrease in Stockholm, and a distinct increase in Turku and Vienna. The trend in Vienna is significant. With the exception that it is not significant, the peak concentration shows exactly the same pattern. Generally, a slight trend towards an earlier start to the pollen season is found. This is more pronounced in Vienna than elsewhere. Slight, but not significant trends for earlier peak

Gram 35 (1996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

corylus trends in start of semn

120

rm . . . .

...

. . . t ... -I--**-&- .---- __-__ .. ...... --..... -. .....-...... 1 ........-_ a o-..o-- .. -b .... ..... --o ...... +. -: ... 0 ... . *... ............... ..........

- 0 . 20 .... .. -- . ._ .............

A

, B trends in peak dayr im

. . .- ................... I

p ........... .............. a.. ......+*=.EL-..

103 .............. ............ -*----- .......... .

- - . .~ _______ __ 0

........ D ... _.

0

yew

T- E?i?zP J*.. %:: --.- beom

Fig. 2. Corjlus. (A) Beginning of pollen season. (B) Peak days. (C) End of pollen season. (D) Peak concentrations. (E) Annual totals.

Alnus A trends in start of reason

(20,

.......... ....................................... I " m 1 ......... e - . . . . . . *-.-~ ---. .. y ... s

, c trends in end of season im

.................. ....................

.... ......... ...........

.............

s m ........... .. ~- . -

;.; .-.. -.-.- a m .... ... _....

o m P u . . m ~ u

yew

TEz3 EZ!? 2% .I%?.. tudl rm *Mm*

Fig. 3. A~JUS. (A) Beginning of pollen season. (B) Peak days. (C) End of pollen season. (D) Peak concentrations. (E) Annual totals.

Gram 35 ( 1 996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

Betula kcnds in start of s e w n

1 0 I

4.m

A

,.-.- ............. . .*-. . .. ._I F.-

/--

E

, B trends in peak days 1 0 ,

........ .. ...... --• a

........ .. ... 0

l : : : r l j - - l _____. !.--L--;--

Kg .... .> -~ ....... -*--- ...... 2-• ~~. .... . ....l.... --%- --A ....... ............... l a u m " O I p y

Fig. 4. Berulu. (A). Beginning of pollen season. (B) Peak days. C) End of pollen season. (D) Peak concentrations. (E) Annual otals. totals.

Fig. 5. Ulntus. (A) Beginning of pollen season. (B) Peak days. (C) End of pollen season. (D) Peak concentrations. (E) Annual

Gram 35 (1996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

176 S. Jager et al.

Pinus A trends in start of selton

im I 1

h,, ..... . . . 3 ................... 0 .

0 ........

. B trend3 in peak day 1 9 0 , . . . . . . . . . . . . . . . . . ..I

................ .... ... .P - ........ . . . . . .

P Y I U D ~ I 110

ye= 1MWn-1lm Tuhl VLm -c -c ---* ..... 0 ....

8.-& M C f l 4

C trends in end of season

.......

I

year T W i SaxkWm Tuhl V m * * * -c - -.* ...........

-.m m- @<OW

Fig. 6. Pinits. ( A ) Beginning of pollen season. (B) Peak days. (C) End of pollen season. (D) Peak concentrations. (E) Annual totals.

days are found in all four stations. A similar weak trend towards an earlier end of season is observed in Stockholm and Vienna, while a trend in the opposite direction is observed in Turku. The duration of the season shows no trend in Trondheim and Stockholm but a slight trend towards longer seasons in Turku and Vienna.

DiJJerettces betweeti the satitpliiig sites. - For Trondheim, the trends towards an earlier start of the seasons for Coryhrs, Alniis and U h t a as well as for earlier peak days of A ~ J C I S and Ultittis were significant. For Stockholm, the trends towards an earlier start, peak day, and end of the season for Altitrs and Coryhis proved to be significant, as well as a trend towards an earlier end of the season for Ultiiia. For Turku, significant trends have been detected for the start of the Altttis season, and for an earlier peak and end of the season for Coryltis. For Vienna, the trends towards higher totals of Coryhrs, Ultiiiis, and Pittiis, and an earlier end of the Betirla season were significant.

Items ewliiated. - Of the 120 trends examined, nineteen proved to be significant. With respect to annual totals,. a significant upward trend is observed for Corylia, Pinus, and Uhiits. The peak concentration shows no significant trend at all. The start of the pollen season shows a gradient towards earlier occurrence for the period 1980 to 1993 at all sites and for all the pollen types investigated, where the trends for A h i s in all the Nordic countdes, Coryltis in Stockholm and Trondheim, and Uliiiris in Trondheim were significant. Similarly, the peak day was significantly earlier for Aliius in Trondheim and Stockholm, for Coryltts in Stockholm and Turku, and for Ulimis in Trondheim. The end of the season showed significant trends towards an earlier occurrence for Alms in Stockholm, for Corylirs in Stockholm and Turku, for Bettila in Vienna, and for Ultinrs in Stockholm. The majority of the trends evaluated showed an increase in the length of the season, but none were significant.

Specific trends

Begittttitlg of the pollen sensoti (Fig. 7). - The early springs and mild winters, especially for the years 1988 to 1990 and 1992 to 1993 probably affected the onset of the pollen season and the incidence of the peak days, but not the annual totals

1980-1 993 I

T'Lf;L%M Tr$,T," VI Tb:$$ Tr St Tu vi Trail; VL Bettila

Tr=Trondheim SL=Stockholm Tu=Turku Vi-Vienna I . . . . . . . . . . . . . . . . . . . . . . . . . .

Fig. 7. Trends: beginning of pollen season.

1

0.5 . E $

o ! 4 c 8

4.5

1

Grana 35 ( I 996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

Pollen trends iii Scamfirinvia arid Vierilia

1980-1 993

...... . _-. . - . . . . . . . . . . . . . . . ..- . -. .... -

~~ ... _.- ..........

Tr Anus tTuM TrLTEM T r & p TrlffftT&I I . . . . . . . . . . . . . . . . . . . . . . . . . . .

Tr=Trondheirn St=StoCkhOlm Tu=TurkU M=Vienna

Fig. 8. Trends: time of peak days.

1980-1 993

1980-1 993

TrSt CcryTUs u M Tr St Tu M Betuia Tr $t TuM

Plnur . . . . . . . . . . . . . . . . . . . . . . . . . . Tr=Trondheirn St=Stockhotm TumTurku Vi-Vienna

Fig. 10. Trends: peak concentrations.

1980-1 993 -1 1 0.5 ..

Tgii2W TcFT Tr&&M T r p T t M I . . . . . . . . . . . . . . . . . . .

Tr=Trondheim St=Stockholm Tu-Turku M=Menna

Fig. 9. Trends: end of season.

nor the peak concentrations. Time will show whether these trends will continue or not. In some cases there is a clear tendency towards an earlier start of the pollen season, e.g., for Alms in Stockholm, Trondheim and Turku, for Coryliis in Stockholm, and for Ulriitrs in Trondheim.

Peak days (Fig. 8). - In general it is no surprise that a clear trend towards an earlier start of the season also results in earlier peak days. As for the start of the season, five of the 20 trends examined for the occurrence of the peak day were significant, with only slight differences in the day of commencement. The trends for Alriirs in Trondheim and Stockholm, Coryhis in Stockholm and Turku, and Uhitis in Trondheim were significant. The weakest trends towards earlier peak days were observed for Betiila at all stations. Perhaps a mild winter has a greater effect on the peak days of those species which flower early, e.g. AI~iirs and Corylirs than on Betiila which starts to flower at least one or two months later.

Elid of the pollen season (Fig. 9). - There seems to be a general tendency for the season to finish earlier with a few exceptions, e.g., Alriits and Piritis in Turku, Betiila in Trondheim. The trends for Abirrs in Stockholm, Coryliis in Stockholm and Turku, Betrila in Vienna, and Ulriiiis in Stockholm, were significant, but no clear trends towards an earlier end of the season have been found for Piriiis. The main pollen season for Coryliis, Altiiis and Ultiiiis ends earlier

. . - - I -- Tr&,cM T&s&k? Tr&Tg" TrStTuM Tr tTuW

Tr=Trondheim St=Stockholnl Tu=TUrku M=Menna

Rnus &lU* 1 . . . . . . . .

Fig. 11. Trendr annual totals.

177

1

0.5

E i

o ! .Q

I E 8

4.5

1

1

0,s

E P O I

f c 8

4.5

1

in Stockholm, over the years, but this does not mean that the season is shorter. In Turku the Corylus season both ends and begins earlier, but we would like to point out that 1988 has been omitted from these calculations, since no Coryhis pollen occurred in Turku in that year. The Betirla season terminates earlier in Vienna. In Turku A h i s and Pilitis show a slight trend in the opposite direction, as does Betiila in Trondheim.

Dirratiori of the S E ~ S O I I . - Although we observed a clear trend towards an earlier start and peak day and a less pronounced trend towards an earlier end of the season, the duration of the seasons is not significantly longer. Most of the trends are towards a prolonged season, but particularly Betiila and Alms in Vienna show trends towards shorter pollen seasons. Nevertheless, a slight trend towards a longer season is generally noticeable.

Peak concentrations (Fig. 10). - It is to be expected that peak values should show similar patterns and characteristics as annual totals and in the majority of cases they do. However, there is no significance in these trends. An increase was found particularly for Betiila, for Coryhrs (Turku, Vienna), Piriiis and Ulr~iirs (Turku, Vienna). A decrease was observed for Alniis in Turku.

Atiriiral totals (Fig. 11). - There is almost no trend visible in the case of Alms, whereas Corylirs, Piriiis and Ultiiiis show

Grana 35 (1996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4

178 S. Jdger et al.

increasing trends of annual totals over the fourteen year period, the trends in Vienna being significant. Maybe a general warming of the atmosphere can be considered to cause this phenomenon.

The relatively early onset of the Coryliis season in Turku seems to contribute to the high annual pollen totals. On the other hand, the number of Coryliis pollen grains recorded is rather low and so these trends may not be real.

Beiiila does not reveal any significant trend in annual totals, probably due to its biennial periodicity in pollen production in Scandinavia.

The downward trend for the Piiiiis and Ulrntis totals in Stockholm is remarkable, and may be due to local effects (compare with Poaceae in Leiden, Jager et al. 1991), either urbanisation, a successive forest decline caused by air pollu- tion or local cutting. Piriiis shows clear trends to higher annual totals in Turku and Vienna.

While Ulriiiis shows noticeable upward trends in Turku and Vienna, extremely high Ulriius values have been reported from Erfurt for 1991 (H. Winkler: personal communication). The subsequent death of the elms was suggested as a possible reason (stress effects) for this phenomenon. In Turku the increase seems to be caused by cultivated park trees.

CONCLUSIONS

A trend towards an earlier start of the pollen season is clear for all taxa at all stations, and is statistically significant for Altiiis in Trondheim, Stockholm and Turku; for Coryhis in Stockholm and for Ulrntis in Trondheim. The incidence of peak days is, in general, earlier for all taxa at all stations, being significant for Coryhis, Alniis and Ultiitis in Scandinavia. The pollen season mostly ends earlier for all taxa at all stations. This is statistically significant in Stockholm (Coryltis, Alrttis, Ulriiiis), Turku (Coryliis), and Vienna (Behila). No significant trend in peak concentrations was found. In most cases there is an increase in pollen amounts

with the followving exceptions: Coryliis and Ulrnus (Trondheim), Altius (Turku), Ulriziis and Pittiis (Stockholm).

significant increase in Vienna over the period investigated. A h i s shows a downward trend in Turku as do Ulrittis and Piniis in Stockholm, and Ulriiiis in Trondheim.

5. The annual totals of Coryliis, Ulriitis and Pititis show a

ACKNOWLEDGEMENTS

We are grateful to Ing. W. Gedlicka, Vienna, for calculating the p-values and to Professor H. B. J. Birks, Bergen for his valuable help concerning the statistical analysis.

REFERENCES

Ehrendorfer, F., (Ed.). 1973. Liste der Gefisspflanzen Mittleleuropas. - G. Fischer, Stuttgart.

Henrysson, S. 1957. Elementar statistik. - Almquist & Mksell & Gebers, Stockholm.

Hamet-Ahti, L., Palmtn, A., Alanko, P. & Tigerstedt, P. M. A. 1989. Suomen puu - ja pensaskasvio. (Woody Flora of Finland). - Yliopistopaino, Helsinki.

Jager, S. 1989. Trends in the frequency of different pollen types in Vienna from 1976 to 1989. - Aerobiologia 5: 9-16.

Jager, S. 1990. Tageszeitliche Verteilung und langjlihrige Trends bei allergiekompetenten Pollen. - Allergologie 13: 159-182.

Jager, S., Spieksma F. Th. M. & Nolard, N. 1991. Fluctuations and trends in airborne concentrations of some abundant pollen types, monitored at Vienna, Leiden and Brussels. - In: 4th Int. Conf. Aerobiol. Stockholm 1990. Proc. Vol. 2 (ed. M. Hjelmroos), pp. 309-312. - Scand. Univ. Press, Oslo-Stockholm.

Lejoly-Gabriel, M. 1978. Recherches kologiques sur la pluie polli- nique en Belgique. - Acta Geographica Louvaniensia 13: 1-279.

Mullenders, W., Dirickx, M., van der Haegen, D., Bastin-Servais, Y. & Desair-Coremans, M. 1972. La pluie pollinique A Louvain- Heverlee en 1971. - Louvain Medicine 91: 159-176.

Nilsson, S. & Persson, S. 1981. Tree pollen spectra in the Stockholm region (Sweden) 1973 1980. - Grana 2 0 179-182.

Pathirane, L. 1975. Graphical determination of the main pollen season. - Pollen et Spores 17: 609 610.

Grana 35 (1996)

Dow

nloa

ded

by [

Ston

y B

rook

Uni

vers

ity]

at 0

7:11

19

Oct

ober

201

4