Climate and herbivore influence on Vaccinium myrtillus over the last 40 years in northwest Lapland, Finland

Abstract

Abstract. Annual fluctuations in the abundance of wild berries have repercussions on animals and humans who depend on this important resource. Although studies have tried to disentangle the effect of climate and herbivores on inter-annual berry yield, there are still many uncertainties as to which factors are driving productivity. In this research, we evaluated the effect of climate and predation by rodents and moths on the abundance of bilberry (Vaccinium myrtillus) flowers and berries at the Kilpisj€ arvi Biological Station in northwest Finnish Lapland. The data were collected from 1973 to 2014 in a forest and an alpine site, both undisturbed by human activities. This dataset is unique due to the length of the sampling period, the availability of flower, berry, and rodent abundance data as well as the undisturbed nature of the habitat. Previous summer temperatures, the abundance of rodents, and the presence of a moth outbreak were complementary factors explaining the abundance of flowers. Herbivores had a larger impact on flower production than climate, but both variables were important to understand reproductive effort. Contrary to results from experimental studies, warmer winters did not significantly influence reproductive success. The abundance of fruits was strongly correlated with pollinator activity; the forest site, with a larger pollinator network, had a higher reproductive success and spring conditions were linked to inter-annual variability in fruit production. Our results illustrate the importance of the location of the population within the species distribution range to understand plant sensitivity to climatic fluctuations with fruit production only influenced by current year summer temperatures at the alpine site. Finally, we observed a general increase in flower and fruit production at the alpine site, which was driven by large yields since the early 1990s. Fruit production at the forest site was comparatively stable throughout the study period.

Spatial variability in pollen and resource limitation for fruit production of two species in interior Alaska:Vaccinium uliginosumandV. vitis-idaea

“…High flower density around Vaccinium plants may lure pollinators away from the Vaccinium flower, as suggested by the floral market hypothesis, but could also draw pollinators into the area that otherwise would not have visited [37]. Pollen availability explained the most variation in Finnish bilberry (V. myrtillus) fruit production models [38]. Given the overall low pollinator availability in black spruce forests [34,39], we expected plants in neighborhoods with high total floral resources to have greater pollen loads and lower pollen limitation than those in neighborhoods with low total floral resources.…”

Direct and Indirect Effects of Overstory Canopy and Sex-Biased Density Dependence on Reproduction in the Dioecious Shrub Shepherdia canadensis (Elaeagnaceae)

“…Light availability commonly limits plant fitness by influencing the rate of photosynthetic carbon gain [59,62] and the activity of pollinators [13,29]. Ultimately, however, life history determines whether increased light availability will affect fruit production [63,64].…”

“…Light availability in other species has been correlated with flower number [19,26], thereby limiting fruit and seed formation by setting a limit on the number of fruits that can potentially mature [11]. Since light availability is correlated with air temperature and air humidity [27,28], measures of light availability may be a proxy for conditions that may also affect pollinator activity [13,29,30]. Previous studies have shown that fruit production in buffaloberry is affected by light and pollen availability [7,8], as is the case for other angiosperms [9][10][11].…”

Continuous picking may increase bilberry yields

“…For instance, forest management, history and stand age affect the abundance (Hedwall et al 2013;Eldegard et al 2019) and fruit production of bilberry (Nielsen et al 2007;Miina et al 2009). Moreover, the fruit production of bilberry is dependent on numerous climate-related factors (Selås et al 2015;Boulanger-Lapointe et al 2017), leading to a high between-year variation in bilberry yields. Intensive berry picking by rakes may cause damage by ripping and removing the biomass of bilberry comparable to herbivory.…”