Phenology

Richard Smithers (richardsmithers@woodland-trust.org.uk) & Nick Collinson, Woodland Trust

Phenological responses may have wide ranging implications for interactions between species: annual release of gridded baseline climate data, and adoption of UKPN protocols by others at sites where a wide range of variables and other biological responses are also recorded, could enable projection of the future impact of phenological change.

Phenology is the study of the timing of recurring natural events, particularly in relation to climate. The UK Phenology Network (UKPN) is run jointly by the Woodland Trust and the Centre for Ecology and Hydrology. It was started as a pilot scheme in 1998. The website was the first of its kind worldwide (www.phenology.org.uk) and is being developed for use by other networks around the world including members of the European Phenology Network. We now have over 21,000 online and paper-based recorders distributed right across the UK. The database includes a large number of historic datasets extending back to 1736.

The first three months of 2001 were, on average, only 0.03 degrees C warmers than the 30-year average (1961-1990 Central England Temperature). This near-average temperature allows us to presume that phenological timing in spring 2001 was also close to a '30-year norm' with which we can compare other results. Spring 2002, by contrast, was very warm, with temperatures in the three months February- April being on average 2.6 degrees C above the 30-year average. As expected in a warmer spring, all events were considerably earlier in 2002 but there were considerable differences between taxa (e.g. bird activity was on average 6 days earlier than 2002, while plant and insect activity were on average 13 and 18 days earlier respectively) and within taxa, with early spring events seemingly responding to rising temperatures the fastest. Such responses have the potential to cause problems for the life cycles of individual species (e.g. frogspawning was recorded before Christmas in 'spring 2005'), loss of synchrony between interdependent species, and changes in competitive advantage leading to shifts in community composition).

Phenological studies have focused historically on the important relationship with temperature. However, phenological events are likely to be influenced by a number of climatic factors; for example, analysis of UKPN data for autumn leaf tint has revealed relationships with rainfall and sunshine hours. An exploratory analysis of the UKPN database has been undertaken recently to try and relate phenological data gridded by 5km square with climatic databases produced on the same grid by the UK Met Office and UK Climate Impacts Programme (UKCIP). The intent was to explore the relationships between the phenology of species and a range of climate variables, singly and in combination, using mass observation and long-term datasets, then seek to project future phenological events using the UKCIP02 scenarios and consider potential consequences for community composition. The analyses were constrained by the gridded baseline climatology, which is only currently available to 2000. This is unfortunate as there has been significant growth in UKPN records in recent years. Many other research projects make use of baseline climate data and given the rate of climate change, there may be burgeoning demand for this dataset to be updated annually rather than every ten years.

A greater understanding of the potential future impact of phenological change could be developed if UKPN protocols would be adopted at sites where a wide range of variables and other biological responses are also recorded. This would enable any analysis of data in relation to such sites to be extrapolated across the UKPN dataset as a whole thereby greatly increasing its power.