Which ecological processes do we capture when we sample phenology and what have we learned so far from different methods?
Welcome by the Royal Society
Chair’s session overview and introduction to speakers: What long term tropical phenology could contribute to understanding ecosystems: possibilities and obstacles
Dr Katharine Abernethy, University of Stirling, UK
The A-Z of litter-trapping methods
Dr Yu-Yun Chen, National Donghwa University, Taiwan
Monitoring plant phenology pattern has a long history nonetheless most studies focused on a few species. In recent years, several forest sites, such as Barro Colorado Island (Panama), Pasoh (Malaysia), Fushan (Taiwan), applied seed trap method to monitor flower and seed production. This design contains a substantial number of seed traps and three seedling plots adjacent to each trap in large, stem-mapped forest plots. Weekly collection and sorting of samples captured by traps provides phenological information for many plant species in the forests. Flower/seed data with high temporal resolution and large spatial scale offer opportunities to investigate community-wide phenology patterns, its association with climate, and to quantify seed availability and seed dispersal distance. In addition, hypotheses regarding community assembly can be tested combining data from seed traps and adjacent seedling plots. However, trap efficiency and representation are yet examined. Professor Yu-Yun uses long-term seed trap data from three forest sites to address these questions. Preliminary results indicate that the rate of species accumulation in traps slows down quickly when number of traps increases. However, adding more traps largely increases average number of individual per species. Census interval greater than 2 weeks is not recommended due to disproportional loss of phenology information.
Quantifying phenology data through observations: what does the data mean for different questions?
Professor Colin Chapman, McGill University, Canada
Phenological patterns represent the rhythms of plant production and as such play a central role in regulating access to resources for animals, many of which are now endangered. In biodiverse tropical forests, factors that influence phenology are complex, involving climatic, edaphic, and biotic variables. As such long-term data it needed to unravel the interactions among variables and many of the long-term data sets involve information derived from direct or indirect observation of trees made over decades. Thus, a critical question that must be asked to advance theory and conservation is: What does observational phenology data mean when addressing particular questions? Professor Chapman considers questions that have often been ignored in the past including; How can patterns differ if trees are considered as fruiting or not or if a magnitude of fruiting is considered? What is the magnitude of interobserver variation? How do the observation of trees vary with data collected with fruit traps? What do short-term data (i.e., a few years) that is often collected by researchers studying particular animal species, contribute to our knowledge of changing phenological patterns? When considering how change in phenological patterns drive population size of endangered species, what do we consider food? Addressing these questions over many geographical locations and different time scales, will help advance our quantification of phenological patterns and help comprehend how climate change will impact the future of tropical forests and the animals they support.
State of the art of digital camera methods for phenology
Ms Bruna Alberton, Phenology Lab, São Paulo State University (UNESP), Brazil
The application of digital cameras to monitor the environment is becoming global and changing the way of phenological data collection. Digital cameras monitoring vegetation phenology (“phenocams”) have an important role by filling the “gap of observations” between satellite monitoring and the traditional on-the-ground phenology. The technique of digital repeated photographs has increased due to its low-cost investment, reduced size, easy set up installation, and the possibility of handling high-resolution near-remote data. The use of imagery data over the traditional phenological observations allows simultaneous multi-sites and long-term monitoring, collecting high-frequency data (daily, hourly), and reduced human labor fieldwork for data acquisition. Phenocams have potential applications for conservation as to document disturbances and changes on vegetation structure, such as deforestation, fire events, flooding and the vegetation recovery. The association of a long-term imagery data with local sensors (e.g., meteorological stations and surface-atmosphere flux towers) allows a wide range of studies, especially linking phenological patterns to climatic drivers; and the impact of climate changes on plant responses. Phenocam networks are growing globally and represent a potential tool for monitoring tropical phenology, for conservation biology and foster networking, as it provides hourly to daily information of monitored systems spread over several sites, ecosystems, and climatic zones, aggregating invaluable information of wide use from phenology to ecosystem dynamics and changes over space and time.
Tropical forest phenology observations from satellites: challenges & opportunities
Professor Alfredo Huete, University of Technology Sydney, Australia
Space offers a unique vantage point from which to observe the ‘timing’ of recurring phenological phases across Earth’s ecosystems, along with the biotic and abiotic drivers of their timing, and their responses and shifts to climate and environmental change. Satellite sensors are highly calibrated, sophisticated optical instruments that are launched into space to monitor the earth. Satellite data are available at hourly to monthly temporal frequencies; meter to kilometer spatial grids; and include measures of vegetation chlorophyll, fluorescence, air & canopy temperatures, laser scanning, total water storage, active radar and microwave emissions. Through synoptic views, access, and repetitive sampling they generate key measurements that are of immense value in understanding ecosystem functioning. In this talk, Professor Huete will discuss the key challenges and opportunities of satellite based phenological observations across tropical forests. Descriptions of satellite data products, algorithms, data compositing, and quality control/analysis (QA/QC) tools are presented to gain a better understanding of data complexities and improve their utilisation over tropical areas. We further highlight past and current controversies in satellite phenology applications in the tropics and show how they've advanced our knowledge and improved utilisation of satellite data. Case studies of Amazon greening in the dry season and the confounding influences of seasonality in aerosol loadings from biomass burning, dry and wet season cloud contamination, and seasonal sun angle trajectories are emphasised, all of which can augment forest canopy phenology. Satellite phenology studies of tropical forests are optimised with the use of multiple sensors and in conjunction with ground measurements.
Wrap-up synthesis: comparative assessment of methods
Ms Emma Bush, University of Stirling, UK
There are many different ways to observe and record phenology and the current suite of established, long-term, tropical phenology datasets reflects this methodological diversity. Information on the functioning of tropical ecosystems is sparse, and therefore the data recorded in each of these long-term studies is highly valuable. However, the question remains: How can we combine phenology data from different studies to enable meta-analysis of tropical ecosystem function? In this wrap-up talk, Emma Bush will give a comparative assessment of four major methods of phenology data collection - litter-trapping, canopy observations, digital-photography and remote sensing – summarizing for each, the geographic spread across the tropics, the development of protocols and “best practices” for compatibility and the specific ecological information sampled. The major aims of this talk will be to assess which ecological hypotheses can be tested using which data and to identify both opportunities and challenges in combining data for cross-disciplinary, large-scale analyses of tropical ecosystems.
Chair’s final remarks
Dr Katharine Abernethy, University of Stirling, UK