Phenology of Wild Species | Winegrapes | Detritus | Open science

 

The Temporal Ecology Lab focuses on the question: How does global change alter the temporal assembly and disassembly of communities? In particular we study how humans have fundamentally altered how organisms experience time through changes to habitat structure, disturbance cycles, and the global climate system. Our long-term goal is to better understand the mechanisms that drive global change impacts on species, communities and ecosystems so that we can reliably forecast ecological responses and aid in mitigating unwanted consequences. We are especially lucky that this goal lets us tackle a lot of interesting fundamental science.

Phenology of wild plant species

The phenology of plant invasions: How changing seasons and temporal niches assemble plant communities

NSF Postdoctoral Fellowship in Bioinformatics

Understanding why certain exotic species become invasive in particular habitats but not others is complex but important for conservation. Several common theories suggest invasive species benefit from exploiting unused resources in an ecosystem (vacant niche), establishing before native species each season (priority effects) or responding more rapidly to variability in climate (increased plasticity). This research has employed extensive phenological datasets that include a large number of species to test all three theories—in a phenological framework—at once over diverse habitats.

Read more in my paper in Frontiers here and a follow-up paper in AoB Plants here. My cross site analysis appeared in American Journal of Botany.

 

Forecasting phenology: Integrating ecology, climatology, and phylogeny to understand plant responses to climate change

NCEAS working group with Ben Cook

Understanding species responses to climate change has been a major focus of ecology in recent years. A suite of responses has been documented related to timings of life history events (phenology), with some species altering their phenology earlier or later, while other species change little. Robust explanations for this diversity of phenological responses are largely absent from the literature, but are crucial for predicting how communities and the ecosystem services they provide will change in the future. To fill this gap, we synthesized observational and experimental phenology studies across North America and Europe. Because understanding phenology is inherently an interdisciplinary problem, our working group brought together ecologists, climatologists, and phylogeneticists to address phenological responses to climate change at the species and community levels. We organized our efforts into two parts. First (1), we conducted a meta-analysis that compared short-term (most <5 years) experimental studies to longer-term (generally >20 years) observational studies. This tested how responses to shorter-term climate forcing scale up to longer term responses. Second (2), we used some of the longest plant phenology datasets from North America and Europe, spanning over 150 years, to test how well the evolutionary history of plant traits can predict species responses to climate change.

You can read more about the project here, which includes a photo of a quorum of the group and a list of all related data products and publications.

 

Predicting future springs: Reconciling experimental and observational approaches for climate change impacts

Radcliffe Exploratory Workshop with Ailene Ettinger

Following up on earlier workwhich found results obtained from observational versus experimental studies make different predictions for future plant phenology, Ailene Ettinger and I are leading a new exploratory working group on the issue. Our goal is to bring together scientists from around the world, who have experience with phenological studies and will provide diverse datasets, knowledge, and ideas to examine possible underlying causes of this discrepancy through analyses of more fine-scaled climate and phenological data.

 

Understanding diverse phenological responses in Northeastern forests: Local adaptation & plasticity in a functional trait framework

A refined knowledge of how diverse species are cued to grow and reproduce is critical for predicting future carbon storage, climate change and the shape of future plant communities, however, we lack this information for all but a handful of species. Improved predictions can come from understanding what drives phenology at the proximate (i.e., what are the underlying phenological cues) and ultimate levels. Working with a diverse set of northeastern North American trees and shrubs the lab is addressing this at the proximate level by identifying phenological cues via growth chamber and field studies. At the ultimate level, we plan to look at how (1) climate, (2) evolutionary history and (3) correlations with other traits shape phenology.

 

The phenology & future of winegrapes

Understanding phenological hyperdiversity in Vitis vinifera

Winegrapes (Vitis vinifera ssp.) are one of the world's most lucrative and important crops, and also one of the most responsive to climate, with some researchers suggesting terroir equates to climate. A major way this climate sensitivity is exhibited is through phenology---especially the timing of budburst, flowering and veraison. Winegrape varieties (e.g., Pinot Noir versus Cabernet Sauvignon) show high diversity in their phenology---and related temperature requirements for flowering and veraison.

Given their high responsiveness to climate, climate change impacts on winegrapes have the potential to be quite high, yet variation between varieties in their temperature requirements and tolerances should provide some buffering if viticulturists understand this variation and can build upon and develop it. Understanding this variation, however, requires improved studies of phenology that can tease out genetic versus environmental drivers of phenology to build better models of how temperature triggers phenological events, how these triggers vary across varieties and the underlying genetic architecture that creates the hyperdiversity in climate requirements between varieties.

Working with Dylan Burge, Kim Nicholas, and Andy Walker, we are combining phenological observations from a common garden with genetic surveys of winegrapes to (1) build robust phenological models of the diversity of temperature requirements between varieties and (2) identify the genetic regions that map to this phenological variation. Our major goal is to understand how genetic diversity predicts phenological variation in order to improve prediction and forecasting of variety-level responses to climate change, with possible implications for breeding improved varieties for novel climates.

 

Cross-continental coherency in climate forcing of wine grapes

Understanding how climate change will affect agriculture is a critical goal of modern global change research, yet progress towards this goal is stymied by disparate crops and varying agricultural practices as well as little spatially and temporally extensive data. Wine grape records represent some of the most long-term recorded data on earth (harvest records in Europe stretch back over 1,000 years) and information on differing practices is often available. Working with Kim Nicholas, and Leanne Webb (Melbourne University and CSIRO) we are compiling data to compare climate forcing of grape harvests from Australia, Europe and North America. We're forever in the early stages of getting this project off the ground, however, Kim presented some results in her talk 'Trends in Climate and Phenological Changes in California and Australia' at the American Society of Enology and Viticulture meeting (June 2011).

 

The roles of cimate change and drought in driving early harvests

Climate change has altered the timing of winegrape harvests. Across France and globally grapes mature earlier by days and weeks compared to several decades ago. Understanding the climatic drivers of these earlier harvests requires long-term records and teasing out the often intertwined drivers of fruit maturation: temperature and drought.

 

Ben Cook and I are combining long-term harvest records from across France (collated by Daux et al. 2012) with reconstructions of temperature and drought to examine the drivers of early harvest over the previous centuries and more recently.

Detritus in food webs

Field experiment: Grass invasion in coastal scrub - San Diego, California

Invasion by exotic plant species threatens biodiversity and ecosystem functioning worldwide. My PhD research combined field experiments with mathematical modeling to characterize complex interactions among abiotic and biotic factors in plant communities, thereby elucidating both impacts and mechanisms of plant invasions. Grass invasion increased both productivity and soil moisture, which enabled native and exotic plant species to co-exist, and indirectly supported larger and richer arthropod communities. Experimentally added exotic grass litter also increased soil carbon and nitrogen pools by 20% in only two years, showing that ecosystem responses to invasion can be more dynamic than previously believed. Together my findings demonstrated that field experimentation can reveal community and ecosystem impacts of invasion that differ substantially from observational studies.

Papers in Ecology, Global Change Biology, Journal of Vegetation Science, and Oecologia give detail on my findings.

 

Models & Synthesis: Brown-green omnivory across food webs

Understanding the prevalence and role of omnivory in food webs is a long-standing area of research in community ecology. Recent work suggests that multi-channel omnivory---feeding on distinctly different food sources---may structure food webs and promote trophic cascades. Collaborating with Claire de Mazancourt, Stefano Allesina and Kathy Cottingham, John Moore, Stuart Sandin, we used empirical data and modeling to test the prevalence and effect of a common type of multi-channel omnivory, feeding on both living-autotroph (green) and detritus-based (brown) webs. Considering 23 food webs spanning terrestrial, freshwater and marine systems, we found that brown-green omnivory is common across all ecosystem types, occurring most often among primary consumers. Therefore, we developed a simple four-compartment nutrient cycling model for consumers eating autotrophs and detritus. Our model results show that across terrestrial and aquatic systems, omnivorous consumption of detritus is destabilizing at high attack rates on the autotroph, and stabilizing at low attack rates on the autotroph; however, the set of conditions for stable webs with omnivory is much narrower for aquatic systems. Together our results demonstrate that brown-green omnivory is extremely common across ecosystems and may be a stabilizing force in real webs.

 

After many years our findings finally came out in late 2014 in Ecology.

Open science needed to advance global change research

Progress in global change research over the last 20 years has come alongside a distinct shift towards synthetic work. Previously, excellent ecological research was underpinned by observations, experiments, and models often conducted by the same researcher or research group. Today, however, the best work includes syntheses of these three pillars of research through time and space, combining data, methods, and insights from disparate experiments, multiple long-term datasets, and theories.

Data sharing, often mandated in other fields, is generally low in ecology, and code for models and analyses is rarely included with publications. Such a lack of transparency forces ecologists to work without key data and analytical resources, retards collaboration, and impairs research with strong conservation relevance by making most findings difficult to study in depth, build upon, or reproduce. Although ‘open ecology’ appears to have potentially large benefits for the discipline, the vast majority of ecologists have never shared their data for a variety of perceived and real issues.

Working with Mary O'Connor and Jim Regetz I put together an article that outlines and addresses the major concerns and advantages of data and code-sharing, and address the skill sets and logistical needs at the individual and lab-based level. You can download it here. Additionally I have talked about this issue in pieces at Nature here and here and Science Careers.

Temporal Ecology Lab blog
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wolkovich@fas.harvard.edu
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In Cambridge 
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