Increased seed predation in the second fruiting event during an exceptionally long period of community-level masting in Borneo

Multi-trophic consequences of mass flowering in two bamboos (Poales: Poaceae)

Mass flowering (masting) has been hypothesized to be an adaptive strategy to satiate florivores/granivores. However, few studies have corroborated this by examining seed predation in multiple flowering patches of varying sizes across a wide geographical range over multiple years. Moreover, the trophic consequences of masting for the parasitoids of florivores/granivores and their feedback effects are poorly understood. Here, we used the nationwide masting of two bamboo species, Sasamorpha borealis var. borealis and Phyllostachys nigra var. henonis, in Japan and compared florivory and seed sets in multiple flowering patches during the masting year and the following sporadic flowering years. We found lower florivory damage in both bamboo species and higher seed set for Sasamorpha borealis var. borealis in patches with massive and spatiotemporally isolated flowering. Additionally, the relative level of parasitism of florivores increased considerably in the sporadic flowering year, particularly in large flowering patches of Sasamorpha borealis var. borealis. Our results indicate the importance of spatiotemporal isolation during masting for satiating two dipteran florivores and suggest that parasitoids might rapidly suppress the extent of florivory in the sporadic flowering years after masting. Collectively, our study highlights the importance of considering multi-trophic consequences in understanding the adaptive significance of masting.

Global patterns in the predator satiation effect of masting: A meta-analysis

Masting, or synchronous production of large seed crops, is widespread among plants. The predator satiation hypothesis states that masting evolved to overwhelm seed predators with an excess of food. Yet, this popular explanation faced few rigorous tests. We conducted a meta-analysis of studies that related the magnitude of seed production to the intensity of seed predation. Our results validate certain theoretical notions (e.g., that predator satiation is more effective at higher latitudes) but challenge others (e.g., that specialist and generalist consumers differ in the type of functional response to masting). We also found that masting is losing its ability to satiate consumers, probably because global warming affected masting patterns. This shift might considerably impair the reproduction of masting plants.

Predator satiation is the most commonly tested hypothesis that explains the evolutionary advantages of masting. It proposes that masting benefits plant reproduction by reducing the proportion of seed crop that is consumed by predators. This hypothesis is widely accepted, but many theoretical notions about predator satiation have not been subjected to a robust evaluation. To address this issue, we conducted a meta-analysis of studies that quantified seed predation in relation to mast seeding. We found evidence of both numerical (starvation between mast years) and functional (satiation during mast years) response of consumers to masting. These two effects reinforced each other. Masting satiated invertebrate but not vertebrate seed predators. Satiation was more pronounced at higher, temperate, and boreal latitudes, perhaps because masting is more effective in reducing seed losses when plant communities are less diverse. The effectiveness of masting in satiating invertebrate consumers declined over time (1972 to 2018), probably reflecting the impact of climate change on the frequency and intensity of masting. If masting ceases to reduce seed losses, a crucial advantage of this reproductive strategy will be lost, and sustainability of many tree populations will decline.

Monitoring Forest Phenology in a Changing World

Plant phenology is strongly interlinked with ecosystem processes and biodiversity. Like many other aspects of ecosystem functioning, it is affected by habitat and climate change, with both global change drivers altering the timings and frequency of phenological events. As such, there has been an increased focus in recent years to monitor phenology in different biomes. A range of approaches for monitoring phenology have been developed to increase our understanding on its role in ecosystems, ranging from the use of satellites and drones to collection traps, each with their own merits and limitations. Here, we outline the trade-offs between methods (spatial resolution, temporal resolution, cost, data processing), and discuss how their use can be optimised in different environments and for different goals. We also emphasise emerging technologies that will be the focus of monitoring in the years to follow and the challenges of monitoring phenology that still need to be addressed. We conclude that there is a need to integrate studies that incorporate multiple monitoring methods, allowing the strengths of one to compensate for the weaknesses of another, with a view to developing robust methods for upscaling phenological observations from point locations to biome and global scales and reconciling data from varied sources and environments. Such developments are needed if we are to accurately quantify the impacts of a changing world on plant phenology.