Cranberries grow in many Wisconsin sphagnum bogs. One of the two species, the large cranberry, Vaccinium macrocarpon Alt., is among the few American fruit crops in cultivation. Most of the cultivated cranberries have been derived by selection from wild, and more recently from cultivated clones. Like the large cranberry, the small cranberry, Vaccinium oxycoccos L., is native to Wisconsin bogs and it, too, provides wildlife food, though it has not been selected for cultivation. This study examined the primary productivity of wild and cultivated cranberries (Wahlstrom 1979)

Stearns, Forest

Walstrom, Mark

English

University of Wisconsin-Milwaukee

University of Wisconsin MilwaukeeUWM Digital CommonsField Station Bulletins UWM Field StationFall 1980Primary production in wild and cultivatedcranberriesMark WalstromUniversity of Wisconsin - MilwaukeeForest StearnsUniversity of Wisconsin-MilwaukeeFollow this and additional works at: https://dc.uwm.edu/fieldstation_bulletinsPart of the Forest Biology Commons, and the Zoology CommonsThis Article is brought to you for free and open access by UWM Digital Commons. It has been accepted for inclusion in Field Station Bulletins by anauthorized administrator of UWM Digital Commons. For more information, please contact open-access@uwm.edu.Recommended CitationWalstrom, M. and F. Stearns. 1980. Primary production in wild and cultivated cranberries. Field Station Bulletin 13(2): 8-11.8PRIMARY PRODUCTION IN WILD ANDCULTIVATED CRANBERRIESCranberries grow in many Wisconsin sphagnum bogs. One of the twospecies, the large cranberry, Vaccinium macrocarpon Alt., is among the fewAmerican fruit crops in cultivation. Most of the cultivated cranberries have beenderived by selection from wild, and more recently from cultivated clones.Like the large cranberry, the small cranberry, Vaccinium oxycoccos L., isnative to Wisconsin bogs and it, too, provides wildlife food, though it has notbeen selected for cultivation.The producer of any agricultural crop is interested primarily in yield. Forcranberries this means the barrels of fruit produced per acre. However, as withany crop, the yield depends upon the ability of the plant to photosynthesizeand utilize the photosynthate efficiently for vegetative as well as reproductivegrowth. Thus, yield is related to total net productivity and the accumulation oforganic matter in a plant. This study examined the primary productivity of wildand cultivated cranberries (Wahlstrom 1979).METHODSPhotosynthetic efficiency of plants can be measured by the amount ofcarbon dioxide absorbed by the leaves. The rate reported for cranberries is con-siderably higher than that for many crop plants (40 mg C02/ dm 2/hour) (Bonn,et al. 1969). While less efficient than sweet corn, cranberries are more efficientthan most vegetables or fruit trees.The second approach to primary production is by harvesting samples,which is the method used in this study. In September, 1978, three central Wiscon-sin cranberry areas were sampled to determine peak biomass. Twelve individualbogs were chosen, and six samples were obtained in each of these bogs. Thesample bogs included young, medium and old stands (approximately 10, 20 and40 years or older). Several different cultivars were sampled, but one, "Searles,"was sampled in each of the age groups.plots were sampled with a sharpened circular sampler 5 inches in diameter(area .0127 m2). The sampler was driven through the vegetation into the sandysubstrate by hand, and the sample was removed, placed in plastic bags, and laterseparated into various components. The separated material (new leaves, oldleaves, new stems, old stems, fruit, etc.) was weighed, individually dried andweighed again to obtain dry weight. Standing crop was determined to be the sumof all plant parts, while net primary production was defined as new leaves andtwigs and fruit plus the new wood of older stems.In the wild bogs, cranberries grow less densely than in cultivation Largerquadrats of 0.1 meter square were harvested in each of 2 bogs. Monthly sampleswere obtained to follow production as the season progressed.Dry weight of plant material has served as a useful value in comparativeproductivity studies. However, the amount of stored energy represented by agram of weight may vary depending upon "le material stored (i.e. carbohydratevs. fat, etc.). A Parr bomb calorimeter was used to obtain caloric values for thevarious plant parts of wild and cultivated cranberries.9RESULTSThe stands of cultivated cranberries showed reasonably high net primaryproduction, an average value of 723g/m 2/year. This compares reasonably withvalues for agricultural crops which' range between 100 and 3500 g/m 2/year asindicated by Whittaker (1975) (average 650 g/m 2/year).Cranberry stands of different ages have different total productivity levels;younger and medium age stands are somewhat more productive than older ones(mean production 754, 751 and 658 g/m 2/year respectively). The apportionmentof photosynthate to different plant parts appears to shift with age of plant.Older cranberries apportion less to leaves than do medium-age plants. and olderplants allocate more photosynthate to fruit than do the younger plants. Thus,although total net primary production of a cranberry bog declines with age,biomass allocation to the fruit increases, and the bog maintains a relativelyconstant fruit yield. As the plants age, the unit dry weight (g/m 2) of fruit re-mains approximately the same, but the number of fruits increases suggesting thatolder plants tend to bear more but smaller fruits (Table 1). New shoot produc-tion appears to remain constant throughout the life of the plant, although theshoot length may vary with age. The water content of cranberry plant partsvaries considerably. Young cranberry leaves contain 35% water while the olderleaves have 25%, considerably less than the water content of most leaves. Incontrast, fruits are 90% water, and the whole plant average is about 59% waterfor the cultivated V. macrocarpon and 51 % for the wild V. oxycoccos.Table 1. Percentage biomass allocation to cultivated cranberry plant partsaStand age Fruit New Leaves New stems Roots Pedicels WoodYoung 17.3 30.9 17.5 2.1 1.9 30.3Medium 15.0 30.4 16.9 2.5 1.9 33.4Old 20.2 27.5 17.2 1.6 2.0 31.5a Percentages are means of24 individual samples (4 sites, 6 samples per site).In the wild bog, productivity of the small cranberry varied, but in thebetter locations, it produced 68 g/m 2. In another adjacent bog, productionwas 136.7 g/m 2. These values appear reasonable considering the dispersed natureof the wild cranberry popula tion contrasted to the dense monotypic populationin a cultivated bog.Caloric values were obtained from oven-dried samples of wild and cultivatedcranberries using standard calometric techniques. Caloric values appeared relativelyhigh in comparison to those of other plants, and the energy content of thecultivated and wild plants of V. macrocarpon was similar (Table 2). Cranberry10leaves were higher in energy content than other plant leaves which may berelated to the resinous storage products and the photosynthetic efficiencyreported previously. The relatively high levels of stored energy indicated by thecaloric values decrease slightly as the structures (leaves, stems, etc.) age (e.g. newleaves contain 5114 cal/g dry weight, old leaves 4925 cal/g). Caloric values didnot differ greatly between cultivated and wild forms of the large cranberry, v.macrocarpon, and were slightly higher in the small wild cranberry, v. oxycOCCUS.Table 2. Caloric content of cranberry plant structuresSpeciesVaccinium macrocarponAit.Cultivated cranberryVaccinium macrocarponAit.Wild, large cranberryVaccinium oxycoccos L.Wild, small cranberryplant partOld woodNew woodOld leavesNew leavesFruitRootsPedicelsNew and old woodNew and old leavesFruitOld woodNew woodOld leavesNew leavesFruitcal oric value 1/(Cal/g)4867490649255114447145055050481450194568489049395082512549111/ Each value represents the mean of two determinations11DISCUSSION AND CONCLUSIONSince knowledge of plant productivity serves to characterize growthefficiency, and information on allocation of photosynthate is useful in under-standing differences in yield, the relationships between productivity and fruitproduction should be helpful in selecting cultivars. Root productivity is alwaysdifficult to estimate, and with cranberries this was so; hence, the root weightsreported here are probably low (a ratio for below to above ground production of0.02 compared to 0.18 for several woody plants, Bray, 1963). Work in progresson natural bogs indicates that average net primary production for aU speciesvaried between 600 and 868 g/m 2, whereas that for the cultivated cranberrybogs was 723 g/m 2. The similar levels are notable since the cultivated bogs arefertilized and water is maintained at appropriate levels, while the natural bogdepends on nutrients received from the atmosphere or through recycling. Light,nutrients and competition are all involved. While production in the cultiva tedbog takes place in one stratum, production in the natural bog occurs in severallayers.Changes in biomass allocation during the existence of the cultivated cran-berry suggest that once established a cranberry bog will be productive for manyyears. This indeed appears to be the case; one bog sampled was 75 years old andstill yielded fruit at acceptable levels. It is possible that with lower total netproduction in the older bogs, less fertilizer would be needed to maintain growththan in the younger bogs. This question needs further exploration.The physiologic mechanisms of the cranberry are the result of long-termnatural selection in a complex bog community where competition for light andnutrients is often severe. This study suggests that this evolved adaptation to bogconditions and efficiency of photosynthate production has not been greatlyaltered by the hundred or more years of agricultural selection. Understanding ofplant productivity and photosynthate allocation gained in this study suggests thepotential of more extensive work for increasing yields and evaluating culturalpractices.LITERATURE CITEDBonn, B. R. Forsyth and I. V. Hall. 1969. A comparison of the rates of apparentphotosynthesis of the cranberry and the common lowbush blueberry. LeNaturaliste Canadien 96: 799-804.Bray, J. R. 1963. Root production and the estimation of net productivity. Can.J. Bot. 41: 65-72.Walstrom, Mark L. 1979. Primary production of wild and cultivated cranberries.M.S. thesis, Botany. University of Wisconsin-Milwaukee. 68 p.Whittaker, R. H. 1975. Communities and Ecosystems. 2nd. Ed. MacMillan. N. Y.Mark Walstrom and Forest StearnsDept. of BotanyThe University of Wisconsin-Milwaukee

Primary production in wild and cultivated cranberries

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Primary production in wild and cultivated cranberries

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