Investigating the relationship between climate, stand age, and temporal trends in masting behavior of European forest trees

Abstract

Masting—temporally variable seed production with high spatial synchrony—is a pervasive strategy in wind‐pollinated trees that is hypothesized to be vulnerable to climate change due to its correlation with variability in abiotic conditions. Recent work suggests that aging may also have strong effects on seed production patterns of trees, but this potential confounding factor has not been considered in previous times series analysis of climate change effects. Using a 54 year dataset for seven dominant species in 17 forests across Poland, we used the proportion of seed‐producing trees (PST) to contrast the predictions of the climate change and aging hypotheses in Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus petraea, and Quercus robur. Our results show that in all species, PST increased over time and that this change correlated most strongly with stand age, while the standardized precipitation–evapotranspiration index, a measure of drought, contributed to temporal trends in PST of F. sylvatica and Q. robur. Temporal variability of PST also increased over time in all species except P. sylvestris, while trends in temporal autocorrelation and among‐stand synchrony reflect species‐specific masting strategies. Our results suggest a pivotal role of plant ontogeny in driving not only the extent but also variability and synchrony of reproduction in temperate forest trees. In a time of increasing forest regrowth in Europe, we therefore call for increased attention to demographic effects such as aging on plant reproductive behavior, particularly in studies examining global change effects using long‐term time series data.

Continent-wide tree fecundity driven by indirect climate effects

“…Of course, a tree observed to bear seed, now or in the past, is known to be mature now. However, failure to observe seed does not mean that an individual is immature because there are detection errors and failed crop years 41 , 64 .…”

Effects of Sitka spruce masting on phenology and demography of siskins Spinus spinus

“…Climate change models predict drier summers and wetter winters in the north and west of Scotland 34 , which comprises the core breeding range for siskins in Britain and Ireland. Climate change may influence masting 14 – 17 , and may also affect management decisions for plantation forestry 35 – 37 . Given the current large areas of Sitka spruce plantations, such changes are likely to result in reduced Sitka spruce coverage and, consequently, reduced availability of Sitka spruce seeds.…”

“…Most of the area was planted between 1952 and 1976, and most of the Sitka spruce was therefore of cone-bearing age when the study started in 2005 36 . Tree age has been shown to have a strong influence on seed production, even in mature trees 17 , and given that very little felling occurred in the area up to 2020, cone production was likely to have increased throughout the study period (2005–2020). Other major habitats within this radius include freshwater (Loch Lomond), ancient woodland dominated by oak, regenerating woodland dominated by birch, open moorland with scrub, and rural village gardens.…”

“…Sitka spruce shows masting seed production, with years of high cone production synchronous throughout Britain, interspersed with years of low cone production 13 . Masting is thought to be controlled by climate, and is thus susceptible to climate change 14 – 17 . Siskins start to breed earlier in years with high production of Sitka spruce cones 18 .…”

Measuring temporal patterns in ecology: The case of mast seeding

“…(2011) had already warned the masting community about the potential of CV to be a poor metric for measuring the temporal variability of reproductive efforts and that interpreting CV should be considered in context. To date, only a few studies analyzed their data sets using D or PV (Bogdziewicz, Fernández‐Martínez, et al., 2020; Fernández‐Martínez et al., 2017, 2019; Koenig et al., 2020; Pesendorfer et al., 2020; Vergotti et al., 2019) after our first warning about the problems linked to using CV for masting was published (Fernández‐Martínez et al., 2018). Ascari et al.…”