Elevation‐dependent responses of tree mast seeding to climate change over 45 years

Abstract

We use seed count data from a New Zealand mono-specific mountain beech forest to test for decadal trends in seed production along an elevation gradient in relation to changes in climate. Seedfall was collected (1965 to 2009) from seed trays located on transect lines at fixed elevations along an elevation gradient (1020 to 1370 m). We counted the number of seeds in the catch of each tray, for each year, and determined the number of viable seeds. Climate variables were obtained from a nearby (<2 km) climate station (914-m elevation). Variables were the sum or mean of daily measurements, using periods within each year known to correlate with subsequent interannual variation in seed production. To determine trends in mean seed production, at each elevation, and climate variables, we used generalized least squares (GLS) regression. We demonstrate a trend of increasing total and viable seed production, particularly at higher elevations, which emerged from marked interannual variation. Significant changes in four seasonal climate variables had GLS regression coefficients consistent with predictions of increased seed production. These variables subsumed the effect of year in GLS regressions with a greater influence on seed production with increasing elevation. Regression models enforce a view that the sequence of climate variables was additive in their influence on seed production throughout a reproductive cycle spanning more than 2 years and including three summers. Models with the most support always included summer precipitation as the earliest variable in the sequence followed by summer maximum daily temperatures. We interpret this as reflecting precipitation driven increases in soil nutrient availability enhancing seed production at higher elevations rather than the direct effects of climate, stand development or rising atmospheric CO2 partial pressures. Greater sensitivity of tree seeding at higher elevations to changes in climate reveals how ecosystem responses to climate change will be spatially variable.

Spatial patterns and broad‐scale weather cues of beech mast seeding in Europe

“…High temperatures in the summer before masting (MAX JUL‐1 ) have been linked to flower primordia differentiation (Wachter, ; Gruber, ; see also: Merkle et al ., for oaks, Allen et al ., ; Miyazaki et al ., ), in particular via an increase in endogenous gibberellins (Turnbull, ; Pearse et al ., ). Following this reasoning, we might expect the phenology of primordia differentiation to vary with latitude, creating a geographical gradient in the timing of the previous summer cue similar to the pattern we found in some southern European NUTS‐1 (Fig.…”

“…In particular, it is still unclear whether both gradual and abrupt (e.g. extreme events) components of climate change influence masting frequency and spatial synchrony within and across species or phylogenetic groups (Koenig et al ., ), for example through changes in resource levels (Miyazaki, ; Allen et al ., ), pollen availability (Koenig et al ., ), coexistence of species with different biomass allocation strategies (Pérez‐Ramos et al ., ), and in the interactions between the processes of resource accumulation and flower induction (Monks et al ., ).…”

Large‐scale pest control in New Zealand beech forests

“…(), Allen et al . (). During the winter of 2013, we used a model to predict the likely seedfall in 2014.…”

Altered dynamics of broad‐leaved tree species in a Chinese subtropical montane mixed forest: the role of an anomalous extreme 2008 ice storm episode

“…2013; Allen et al. 2014). Besides, it may have resulted from temporal discontinuity with mortality occurring first and thus releasing resource for recruitments of both species groups (Lloret et al.…”