NI: MAST-NET: masting responses to climate change and impacts on ecosystems

Most plants do not produce regular annual seed crops, but switch between years of bumper seed crops (known as "mast years") and years with low seed production. Intriguingly, these bumper crops occur simultaneously in plants living alongside each other, and synchronisation can extend across hundreds of kilometres. For example, we have previously shown that in 1976, 1992, 1995 and most recently in 2011, beech trees across Western Europe (including the UK, Germany, France and Poland) all produced heavy seed crops in the same year. Interestingly, 1992 and 1995 were also bumper years for pine-cone production in spruce forests in the same region.

This highly variable production of seeds is an important process in ecosystems. Producing seeds is a key step towards successfully establishing the next generation of plants. Masting is beneficial for plants because in years of bumper seed crops, seed predators cannot consume all the available seeds, which ensures that some survive to germinate the next spring. In ecosystems that are influenced by disturbance such as wildfires, windstorms and logging by humans, the timing of the next bumper seed year is also crucial to the ability of plants to regenerate. However, the importance of masting extends beyond plants. Bumper seed crops in forest trees represent a pulse of food resources, and cause population booms in small mammals (e.g. voles and mice) and seed-eating birds (e.g. woodpeckers and great tits). Low seed crops in sequential following years can eventually result in population crashes. These boom-and-bust cycles of small animals have further impacts on ecosystems. One of the most important for humans is the effect on tick numbers, which fluctuate in response to the number of host animals. Ticks act as a host for the Lyme disease pathogen, and research has shown that Lyme infection rates in humans peak two years after bumper seed crops in forest trees, including beech and oak. Masting is not just important in natural ecosystems, however. Many fruit and nut crops come from "masting" species. In agriculture, this phenomenon is usually known as "alternate cropping". Fruits grown in the UK, including apples and cherries, show this characteristic year-to-year variation in crop size, which causes variation in annual crop yield for farmers. It is also important in many other commercially valuable species, including olives, almonds and pistachios.

For these reasons, we need to be able to predict seed crops in "masting" species accurately. This information is necessary for the management of natural ecosystems and agricultural systems that rely on masting species. Furthermore, predicting bumper seed crops will allow us to forecast years of high risk from infectious diseases carried by animal feeding vectors, such as Lyme. An important question is how seed production in masting species will change in the future with changes in climate. This project is designed as the first crucial step to achieving these objectives. It will establish an international network of researchers to build the datasets necessary to understand the causes of bumper seed crops, and to predict seed production in masting species. We will draw together data from the tropics with data from boreal forests to understand how masting varies between species, and will use long-term monitoring conducted by members of the network to understand how seed production varies over time, and what triggers bumper seed years. We will also search archives and scientific literature for useful data: in a previous project we found useful data on seed crops collected by 18th century foresters, demonstrating that in some species, there is potential to develop very long records of seed production. The datasets that we will build in this project will then act as a spring-board for future research, including projects linked to public health, habitat management, and agriculture, taking advantage of the wide range of network expertise.

Overview
The scientific goal of this project is to improve our understanding of the drivers and ecosystem impacts of variable seed production in masting species. The project is mainly focused on network- and collaboration-building, and has been designed to maximise the potential long- and short-term impact of our work, including through the funding of future proposals.

The research will make contributions to society and the economy in several key areas.

Ecosystem and biodiversity management:
Masting is a key process in the functioning of ecosystems. Improved data and the development of predictive models for mast years will be valuable for the management of ecosystems, including for natural resources and biodiversity. Hacket-Pain and PP Vacchiano are developing a Royal Society International Exchanges proposal to combine MASTREE+ and ExperiMAST within an ecosystem model of carbon cycling (3D-CMCC FEM) to understand the implications of masting for carbon storage. Masting is also a key process in the dynamics of regeneration in managed habitats (including through the interplay with animals). A project to integrate the results of MAST-NET within the FORSPACE forest dynamics model is planned with Prof K. Kramer (Wageningen University, Netherlands), focusing on the predicting how future changes in masting will influence tree regeneration, forest species composition and structure. The project outline was developed with Prof. Kramer during a recent EU COST Action meeting, and will look specifically at how management options interact with masting to determine future trajectories of habitat change.

Kramer, et al. 2003. For Ecol Manag, 181:205-222.

Agriculture and forestry:
Masting characterises the annual yield of many important fruit and nut crops, but masting is also important to agriculture through the link between masting and animal-borne disease. Tanentzap has established links with CambPlants (cambplants.group.cam.ac.uk) and the Cambridge Centre for Crop Science (niab.com/pages/id/427/cambridge_centre_for_crop_science_-_3cs), which provides support for knowledge transfer in plant-related research. Together with the UoL Centre for Excellence for Sustainable Food Systems, they will facilitate the establishment of collaborations for future applied research proposals. Masting is also a key factor in determining the success of regeneration in managed forests. The timing of forestry activities in relation to mast years is of key interest where natural regeneration is part of the forest management strategy. Co-I Thomas has established research links with the UK Forestry Commission, and many of the PPs also have strong silviculture and applied-research links. These will be used to ensure that the output of MAST-NET are designed to maximise value to this sector, and will be used to identify valuable future outputs for the network.
Public health: The datasets produced by MAST-NET (particularly MASTREE+) will be of significant value to public health researchers, particularly in the development of tools to predict infection dynamics and human infection risk in animal-borne disease. This work is not a direct aim of this network-building proposal, but is a long-term objective of the network (particularly the PI). The University of Liverpool (UoL) is ideally placed to develop the long-term interdisciplinary research required to support this aim (e.g. "Infectious Disease" is a UoL headline research area: liverpool.ac.uk/research/our-research). The UoL has substantial expertise and institutional support for the application of research in this area, including through the Centre of Excellence in Infectious Disease Research (liverpool.ac.uk/research/our-research/infectious-diseases/ceidr). The PI is already engaging with this community in Liverpool (e.g. "Tick Activity Project"). This community will be invited to participate in our outward-facing event at the final network meeting (to be hosted in Liverpool to maximise engagement).