Agricultural and Food Science in Finland 253 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 253–257. © Agricultural and Food Science in Finland Manuscript received February 2000 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 253–257. Research Note Influence of changes in crop cultivation areas on pollen contents of honey Anna-Liisa Varis Department of Applied Zoology, PO Box 27, FIN-00014 University of Helsinki, Finland Pollen counts were done on honey collected by a Finnish honey corporation in late summer 1997 from the entire beekeeping area of Finland. The most common pollen type was Brassicaceae pollen, which was represented by 60% of the grains counted. It was followed by Salix spp. (10%), Trifolium repens + T. hybridum (10%) and T. pratense + T. medium (6.5%) species. Pollen grains of Phacelia spp, Filipendula ulmaria, Apiaceae, Sorbus aucuparia, Malus domestica, and Rubus idaeus were also numerous. These pollen types constituted 96% of all the pollen examined. These results and those of the earlier pollen counts in Finland were compared with the cultivation areas of the most important nectariferous crops. In the 1930s white clover was the most important honey source in Finland and its pollen was very dominant in honey. Since the 1950s oilseed crops have been grown in increasing rates and pure timothy-meadow fescue pastures and hay stands with heavy N applications have decreased the share of Trifolium species. The proportion of Brassicaceae pollen has continuously increased with the increase of the growing area of turnip rape Brassica rapa ssp. oleifera and rape, B. napus ssp. oleifera. At the same time the proportion of T. repens + T. hybridum pollen has decreased so that their mutual relationships are now reversed compared to the beginning of the 1960s. Changes in land use were thus very clearly to be seen in the pollen content of honey. Key words: pollen analysis, land use, agricultural crops, Finland Introduction Pollen analytical studies have mainly been used to provide some idea of the geographical origin of honey and forage crops of bees and they have also been used to describe historical changes in the vegetation of the landscape (e.g. Hall 1997). In the latter case pollen grains have been taken from peat or mud sediments. Several studies of the pollen content of Finn- ish honey have been done during the last few decades. Martimo (1945) analysed 21 honey samples dating from the year 1937 and discussed their botanical origin. Aario (1961) studied 85 honeys in order to describe the regional condi- 254 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Varis, A.-L. Changes in crop cultivation areas and pollen contents of honey tions of beekeeping. Purokoski and Forsius (un- published) analysed 120 samples in 1962–1963, their main interest being their chemical compo- sition. In 1977 and 1978 Varis et al. (1982) stud- ied 160 samples to describe the average pollen spectrum of Finnish honey and to analyse the most important factors responsible for its varia- tion. During the last 60 years great changes have taken place in the agricultural practices and in the acreages of crops. Because of this the sup- ply of honeybee forage plants has also dramati- cally changed. Most of all, the cultivation of oilseed crops has increased and the growing area of clovers has decreased. The purpose of this paper was to describe changes in agriculture during the last six decades through pollen ana- lysis. Material and methods Pollen counts were made from honey samples taken from the containers of a Finnish corpora- tion (Oy Hunajayhtymä Ab) in the autumn of 1997. The corporation purchased honey from individual beekeepers throughout the entire bee- keeping area in Finland at the end of the season. When one container was full, the next one was started. There were five containers, each with a capacity of 50,000 litres. Before sampling the honey was stirred by means of electrically operated steel mixers. Two samples of 300 grams were taken from each container in glass jars at the end of September. The samples were thoroughly mixed and two subsamples of 10 g were taken from each sam- ple for pollen analysis. Pollen counts were per- formed as described in Varis et al. (1982). The results of these and those of the earlier pollen counts in Finland were compared with the cul- tivation area of the main nectariferous crops (Central Statistical Office of Finland 1962, 1981). Results and discussion A total of 30 pollen types were identified either on the species or generic levels, and two were identified at the family level. The means and standard deviations of the pollen types represent- ing cultivated plants are given in Table 1. These pollens represented 81% of the pollen counted. The most common pollen type was Brassicaceae pollen, which represented 60% of the grains counted, followed by Trifolium species (16%). Of the other pollen types Salix species (10%) were the most numerous, followed by Filipen- dula ulmaria (2%), Apiaceae species (2%) and Sorbus aucuparia (1%). Pollens of Brassicace- ae, Trifolium repens + T. hybridum, T. pratense + T. medium and Salix spp. were present in all the samples. Comparison of these results and those of the earlier pollen counts with the cultivation area of the main nectariferous crop are given in Fig. 1. In 1937 Brassica oilseed crops were not grown in Finland, and Brassicaceae pollen was not found in honey. Then. by far the most com- mon pollen type was Trifolium repens pollen. It was represented in all samples, and its percent- age in half of the samples was as much as 85– 100% (Martimo 1945). White clover was grown especially in pastures, often together with other clovers. Later, its proportion diminished. Since the 1950s oilseed crops have been grown in in- creasing rates. Table 1. Counts of pollen types representing agricultural and horticultural crops (N=20). Plant species Mean Standard deviation Brassicaceae 192.5 54.5 Trifolium repens + T. hybridum 31.6 23.2 Trifolium pratense + T. medium 20.7 6.3 Phacelia spp. 6.8 6.5 Malus domestica 3.6 3.9 Rubus idaeus 3.2 3.0 Fragaria spp. 0.2 0.6 255 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 253–257. In the beginning of the 1960s the proportion of T. repens + T. hybridum pollen was approxi- mately 42% of total pollen (Aario 1961, Purokos- ki and Forsius (unpublished)). In Finland T. hybridum has been the most important forage legume after red clover and its seeds were main- ly taken from mixed clover-timothy stands (Valle 1960). About 6,000 ha of oilseed crops were under cultivation (Central Statistical Office of Finland 1962) and the proportion of Brassicaceae pollen averaged 12%. At the end of the 1970s the growing area of oilseed crops had increased up to 30,000 hec- tares (Central Statistical Office of Finland 1981) due to a new subsidy policy, and the percent- ages of Brassicaceae pollen counts were about 30 (Varis et al. 1982). The proportion of T. repens + T. hybridum pollen was less than 10%. Chang- ing over from mixed clover-grass stands to pure graminaceous stands with heavy N application had diminished the role of clover in pastures and hay fields. The cutting of forage crops is also done earlier, generally before flowering. The decrease in cattle farming has also reduced the pasture areas. In 1997 oilseed crops were grown in 61,000 hectares (Maa- ja metsätalousministeriön tie- topalvelukeskus 1998). The percentage of Brassicaceae pollen was 60% and that of T. re- pens + T. hybridum 10% (present study). There are many wild Brassicaceae plants growing in the fields and meadows but compared with cultivated crucifers their role seems to be marginal. The amount of land used to cultivate other honeybee forage plants (Table 1) is small and local, and the proportions of their pollen varied according to the samples. No comparison could be made of any changes that might have occurred to them during the study period. Of these plants Phacelia spp. is cultivated by some beekeepers in the neighbourhood of beehives and in set-aside fields. In spite of the decrease of the seed produc- tion areas of red clover (Table 2, information given in a letter from the Ministry of Agricul- ture and Forestry) the role of its pollen was high- er in the 1970s and 1990s than in the 1960s. In the 1930s there were no special seed production Fig. 1. Average proportion of Brassicaceae pollen in honey sam- ples and the growing area of Brassica oilseed crops (Central Statistical Office in Finland 1962, 1981, Maa- ja metsätalousminis- teriön Tietopalvelukeskus 1998). Observations from 1937 by Mar- timo (1945), from 1960 by Aario (1961), from 1962 and 1963 by Purokoski and Forsius (unpub- lished), from 1977 and 1978 by Varis et al. (1982), and from 1997 (this study). Table 2. The red clover seed production areas (Information given in a letter from the Ministry of Agriculture and For- estry) and the roles of Trifolium pratense + T. medium pol- len in the study years. Year Seed production area Pollen % 1937 – – 1960, 1962–1963 6 717 1–2 1977–1978 2 950 5.4 1997 no statistics available *) 6.5 *) but considerable smaller than in 1977–1978, the harvested area was only 706 ha. 256 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Varis, A.-L. Changes in crop cultivation areas and pollen contents of honey areas but the seeds were produced together with timothy and T. hybridum as has been done to some extent later. The flowers of red clover have a long corol- la which restricts the ability of honeybees to penetrate them. In the past, by far the most com- mon bee race in Finland was the Black bee (Apis mellifera mellifera) but since the 1970s the role of the Italian bee (Apis mellifera ligustica) has increased so that it comprised in 1988–1989 about 70% of the bee colonies, the role of the Black bee being 5–10% (Peltotalo 1990). The tongue of the Italian bee is considerably longer, being 6.3–6.6 mm than that of the Black bee, which is 5.7–6.4 mm long (Ruttner 1975). The number of bee colonies has also increased from 15,000 in the 1930s (Tuomainen 1931) to 45,000 in the 1990s (Peltotalo 1990). The colonies are now also more often moved to the flowering plants than earlier. These facts may partly ex- plain the increased role of red-clover pollen in the later counts. Because the containers were filled randomly in the order of the arrival of honey batches from different regions of the country, there were dif- ferences between the samples, but on the whole a good overview was obtained of the present pollen composition of Finnish honey. Although the pollen spectrum alone is not a reliable index of the botanical origin of honey, the changes in pollen spectrum very well reflected the changes in the acreages of main honeybee forage crops. Hjelle (1999) found that the pollen assem- blages of surface moss polsters reflected the lo- cal vegetation. Gradients were found in the pol- len assemblages relating to land-use practices as well as geographical regions. According to Kenyon and Rutherfurd (1999) analysis of pol- len in floodplain sediments provided a technique for identifying major historical changes in veg- etation. The present study shows that changes in ag- ricultural policy which have changed the agri- cultural systems and land use are to be seen in the pollen content of honey. Acknowledgements. I am grateful to Mrs Silja Mäkelä for her technical assistance and to Mr Erkki Ruohonen for sup- plying the honey samples. References Aario, R. 1961. Mehiläishoidon levinneisyys ja sen maata- loudelliset edellytykset Suomessa. Mimeogr. 70 p. (Available at Department of Geography, University of Helsinki, Finland). Central Statistical Office of Finland 1962. Statistical Year- book of Finland 1962. 477 p. – 1981. Statistical Yearbook of Finland 1981. 517 p. Hall, V. 1997. The development of the landscape of Ire- land over the last two thousand years; fresh evidence from historical and pollen analytical studies. Chro- nion 1, 1: 1–22. Hjelle, K.L. 1999. Modern pollen assemblages from mown and grazed vegetation types in western Norway. Review of Palaeobotany & Palynology 107: 55–81. Kenyon, C. & Rutherfurd, I.D. 1999. Preliminary evidence for pollen as an indicator of recent floodplain accu- mulation rates and vegetation changes: The Barmah- Millewa Forest, SE Australia. Environmental Manage- ment 24: 359–367. Maa- ja metsätalousministeriön Tietopalvelukeskus 1998. Lopulliset satotulokset vuosina 1997 ja 1998. 1 p. Martimo, M. 1945. Suomalaisen hunajan ominaisuuksis- ta ja alkuperästä. Maataloustieteellinen Aikakauskir- ja 17: 157–169. Peltotalo, P. 1990. Selvitys mehiläistarhauksesta ja hu- najan markkinoinnista Suomessa osa II. Mehiläinen 6:165–171. Ruttner, F. 1975. Races of bees. In: The Hive and the Honey Bee. Dadant & Sons, Hamilton, IL. p. 19–38. Tuomainen, L. 1931. Lyhyt mehiläishoidon opas. Porvoo. 86 p. Valle, O. 1960. Alsikeapilan siementuotantomahdolli- suuksista Suomessa. Summary: Possibilities of alsike clover seed production in Finland. Maatalous ja Koetoiminta 14: 118–127. Varis, A.-L., Helenius, J. & Koivulehto, K. 1982. Pollen spectrum of Finnish honey. Journal of the Scientific Agricultural Society of Finland 54: 403–420. 257 A G R I C U L T U R A L A N D F O O D S C I E N C E I N F I N L A N D Vol. 9 (2000): 253–257. SELOSTUS Viljelyalojen muutosten vaikutus hunajan siitepölysisältöön Anna-Liisa Varis Helsingin yliopisto Syksyllä 1997 otettiin hunajanäytteet viidestä Oy Hunajayhtymä Ab:n 50 000 litran vetoisesta säiliös- tä, joihin oli vastaanotettu hunajaa mehiläishoitajilta ympäri maata. Näytteistä tehtiin siitepölymääritykset ja tuloksia verrattiin aikaisemmin Suomessa tehtyjen siitepölymääritysten tuloksiin ja tärkeimpien mehi- läiskasvien viljelypinta-aloissa tapahtuneisiin muu- toksiin. Yleisin siitepölylaji oli ristikukkaiskasvien siite- pöly, jonka osuus oli 60 % kaikista lasketuista siite- pölyistä. Seuraavina olivat pajut (10 %), valko- ja al- sikeapila (10 %) sekä puna- ja metsäapila, 6,5 %. Hunajakukan, mesiangervon ja muiden sarjakukkais- ten, pihlajan, omenan ja vatun siitepölyjä esiintyi myöskin melko lukuisasti. Yhteensä näiden siitepö- lylajien osuus oli yli 96 % koko aineistosta. Varhaisimmat hunajan siitepölymääritykset maas- samme ovat 1930-luvun lopulta. Valkoapila oli sil- loin tärkein hunajakasvi ja sen siitepöly hunajassa oli dominoiva. 1950-luvulta lähtien ristikukkaisten öljy- kasvien viljely yleistyi. Samanaikaisesti nurmet muuttuivat heinävaltaisiksi ja apilan osuus väheni. Rypsin ja rapsin viljelyn lisääntyessä ristikukkaissii- tepölyn osuus hunajassa on jatkuvasti lisääntynyt ja apiloiden vähentynyt. Suomalaisen hunajan siitepö- lykoostumus on tärkeimpien lajien osalta näin muut- tunut aikaisempaan verrattuna täysin päinvastaisek- si. Vaikka siitepölysisältö yksin ei ole luotettava hu- najan botaanisen alkuperän mittari, tärkeimpien me- hiläiskasvien viljelyaloissa tapahtuneet muutokset heijastuivat erittäin selvästi hunajaan. Title Introduction Material and methods Results and discussion References SELOSTUS