United States National Phenology Network

Tucson, AZ, United States

United States National Phenology Network

Tucson, AZ, United States
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Souza L.,Oak Ridge National Laboratory | Souza L.,University of Tennessee at Knoxville | Belote R.T.,Wilderness Society | Kardol P.,Oak Ridge National Laboratory | And 2 more authors.
Journal of Plant Ecology | Year: 2010

Aims Rising concentrations of atmospheric carbon dioxide ([CO2]) may influence forest successional development and species composition of understory plant communities by altering biomass production of plant species of functional groups. Here, we describe how elevated [CO2] (eCO 2) affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility in eastern Tennessee, USA. We asked if (i) CO2 enrichment affected total understory biomass and (ii) whether total biomass responses could be explained by changes in understory species composition or changes in relative abundance of functional groups through time. Materials and methods The FACE experiment started in 1998 with three rings receiving ambient [CO2] (aCO 2) and two rings receiving eCO2. From 2001 to 2003, we estimated species-specific, woody versus herbaceous and total aboveground biomass by harvesting four 1 × 0.5-m subplots within the established understory plant community in each FACE plot. In 2008, we estimated herbaceous biomass as previously but used allometric relationships to estimate woody biomass across two 5 × 5-m quadrats in each FACE plot. Important findings Across years, aboveground biomass of the understory community was on average 25% greater in eCO2 than in aCO2 plots. We could not detect differences in plant species composition between aCO2 and eCO 2 treatments. However, we did observe shifts in the relative abundance of plant functional groups, which reflect important structural changes in the understory community. In 2001-03, little of the understory biomass was in woody species; herbaceous species made up 94% of the total understory biomass across [CO2] treatments. Through time, woody species increased in importance, mostly in eCO2, and in 2008, the contribution of herbaceous species to total understory biomass was 61% in aCO2 and only 33% in eCO2 treatments. Our results suggest that rising atmospheric [CO 2] could accelerate successional development and have longer term impact on forest dynamics.

Crimmins T.M.,United States National Phenology Network | Crimmins T.M.,University of Arizona | Crimmins M.A.,University of Arizona | David Bertelsen C.,University of Arizona
American Journal of Botany | Year: 2013

Premise of the study: Community-level flowering patterns can be characterized by onset, duration, and end as well as constancy, the degree to which species commence, cease, and reinitiate flowering within a season. In the mountainous Sky Islands region of the southwestern United States, flowering onset is clearly influenced by elevation in the spring, but much less so in the summer season. We evaluated whether these flowering metrics reflect these dissimilar patterns between distinct spring and summer seasons regarding the influence of the elevation and moisture gradient. Methods: We characterized flowering onset, end, duration, and constancy by plant functional type and their relationships to climate variables in spring and summer. We also evaluated the influence of climate on seasonal flowering patterns. Key results: Gaps in seasonal flowering occur frequently in this system in both seasons and among all plant functional types. In both seasons, annual plants exhibit the shortest flowering durations and highest constancies, and plants at low elevations, inhabiting environments with variable moisture conditions, show a greater tendency for longer flowering durations and lower constancy than high-elevation plants. Spring flowering characteristics are most influenced by the total amount of October-March precipitation as well as temperatures in these months, whereas summer flowering characteristics are influenced by the timing of summer-season precipitation, and next by the total amount of summer precipitation. Conclusions: Flowering metrics, especially constancy and duration, show similar patterns in spring and summer and vary across elevation and moisture gradients. These patterns have substantial implications for plant and animal communities. © 2013 Botanical Society of America.

Willis C.G.,Harvard University | Willis C.G.,Duke University | Ruhfel B.R.,Harvard University | Primack R.B.,Boston University | And 4 more authors.
PLoS ONE | Year: 2010

Invasive species have tremendous detrimental ecological and economic impacts. Climate change may exacerbate species invasions across communities if non-native species are better able to respond to climate changes than native species. Recent evidence indicates that species that respond to climate change by adjusting their phenology (i.e., the timing of seasonal activities, such as flowering) have historically increased in abundance. The extent to which non-native species success is similarly linked to a favorable climate change response, however, remains untested. We analyzed a dataset initiated by the conservationist Henry David Thoreau that documents the long-term phenological response of native and non-native plant species over the last 150 years from Concord, Massachusetts (USA). Our results demonstrate that nonnative species, and invasive species in particular, have been far better able to respond to recent climate change by adjusting their flowering time. This demonstrates that climate change has likely played, and may continue to play, an important role in facilitating non-native species naturalization and invasion at the community level. © 2010 Willis et al.

Ibanez I.,University of Michigan | Primack R.B.,Boston University | Miller-Rushing A.J.,United States National Phenology Network | Miller-Rushing A.J.,Wildlife Conservation Society | And 6 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

As a consequence of warming temperatures around the world, spring and autumn phenologies have been shifting, with corresponding changes in the length of the growing season. Our understanding of the spatial and interspecific variation of these changes, however, is limited. Not all species are responding similarly, and there is significant spatial variation in responses even within species. This spatial and interspecific variation complicates efforts to predict phenological responses to ongoing climate change, but must be incorporated in order to build reliable forecasts. Here, we use a long-term dataset (1953-2005) of plant phenological events in spring (flowering and leaf out) and autumn (leaf colouring and leaf fall) throughout Japan and South Korea to build forecasts that account for these sources of variability. Specifically, we used hierarchical models to incorporate the spatial variability in phenological responses to temperature to then forecast species' overall and site-specific responses to global warming. We found that for most species, spring phenology is advancing and autumn phenology is getting later, with the timing of events changing more quickly in autumn compared with the spring. Temporal trends and phenological responses to temperature in East Asia contrasted with results from comparable studies in Europe, where spring events are changing more rapidly than are autumn events. Our results emphasize the need to study multiple species at many sites to understand and forecast regional changes in phenology. © 2010 The Royal Society.

Forrest J.,University of Toronto | Forrest J.,Rocky Mountain Biological Laboratory | Miller-Rushing A.J.,United States National Phenology Network | Miller-Rushing A.J.,Wildlife Conservation Society | Miller-Rushing A.J.,National Park Service
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

Phenology affects nearly all aspects of ecology and evolution. Virtually all biological phenomena-from individual physiology to interspecific relationships to global nutrient fluxes-have annual cycles and are influenced by the timing of abiotic events. Recent years have seen a surge of interest in this topic, as an increasing number of studies document phenological responses to climate change. Much recent research has addressed the genetic controls on phenology, modelling techniques and ecosystem-level and evolutionary consequences of phenological change. To date, however, these efforts have tended to proceed independently. Here, we bring together some of these disparate lines of inquiry to clarify vocabulary, facilitate comparisons among habitat types and promote the integration of ideas and methodologies across different disciplines and scales. We discuss the relationship between phenology and life history, the distinction between organismal-and population-level perspectives on phenology and the influence of phenology on evolutionary processes, communities and ecosystems. Future work should focus on linking ecological and physiological aspects of phenology, understanding the demographic effects of phenological change and explicitly accounting for seasonality and phenology in forecasts of ecological and evolutionary responses to climate change. © 2010 The Royal Society.

Crimmins T.M.,United States National Phenology Network | Crimmins T.M.,University of Arizona | Bertelsen C.D.,University of Arizona | Crimmins M.A.,University of Arizona
International Journal of Biometeorology | Year: 2014

Within-season breaks in flowering have been reported in a wide range of highly variable ecosystems including deserts, tropical forests and high-elevation meadows. A tendency for interruptions in flowering has also been documented in southwestern US "Sky Island" plant communities, which encompass xeric to mesic conditions. Seasonal breaks in flowering have implications for plant reproductive success, population structure, and gene flow as well as resource availability for pollinators and dependent animals. Most reports of multiple within-season flowering events describe only two distinct flowering episodes. In this study, we set out to better quantify distinct within-season flowering events in highly variable Sky Islands plant communities. Across a >1,200 m elevation gradient, we documented a strong tendency for multiple within-season flowering events. In both distinct spring and summer seasons, we observed greater than two distinct within-season flowering in more than 10 % of instances. Patterns were clearly mediated by the different climate factors at work in the two seasons. The spring season, which is influenced by both temperature and precipitation, showed a mixed response, with the greatest tendency for multiple flowering events occurring at mid-elevations and functional types varying in their responses across the gradient. In the summer season, during which flowering across the gradient is limited by localized precipitation, annual plants exhibited the fewest within-season flowering events and herbaceous perennial plants showed the greatest. Additionally, more distinct events occurred at lower elevations. The patterns documented here provide a baseline for comparison of system responses to changing climate conditions. © 2013 ISB.

Miller-Rushing A.J.,United States National Phenology Network | Miller-Rushing A.J.,Wildlife Conservation Society | Hoye T.T.,University of Aarhus | Inouye D.W.,Rocky Mountain Biological Laboratory | And 2 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

Climate change is altering the phenology of species across the world, but what are the consequences of these phenological changes for the demography and population dynamics of species? Time-sensitive relationships, such as migration, breeding and predation, may be disrupted or altered, which may in turn alter the rates of reproduction and survival, leading some populations to decline and others to increase in abundance. However, finding evidence for disrupted relationships, or lack thereof, and their demographic effects, is difficult because the necessary detailed observational data are rare. Moreover, we do not know how sensitive species will generally be to phenological mismatches when they occur. Existing long-term studies provide preliminary data for analysing the phenology and demography of species in several locations. In many instances, though, observational protocols may need to be optimized to characterize timing-based multi-trophic interactions. As a basis for future research, we outline some of the key questions and approaches to improving our understanding of the relationships among phenology, demography and climate in a multi-trophic context. There are many challenges associated with this line of research, not the least of which is the need for detailed, long-term data on many organisms in a single system. However, we identify key questions that can be addressed with data that already exist and propose approaches that could guide future research. © 2010 The Royal Society.

Davis C.C.,Harvard University | Willis C.G.,Harvard University | Willis C.G.,Duke University | Primack R.B.,Boston University | And 3 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

Climate change has resulted in major changes in the phenology-i.e. the timing of seasonal activities, such as flowering and bird migration-of some species but not others. These differential responses have been shown to result in ecological mismatches that can have negative fitness consequences. However, the ways in which climate change has shaped changes in biodiversity within and across communities are not well understood. Here, we build on our previous results that established a link between plant species' phenological response to climate change and a phylogenetic bias in species' decline in the eastern United States. We extend a similar approach to plant and bird communities in the United States and the UK that further demonstrates that climate change has differentially impacted species based on their phylogenetic relatedness and shared phenological responses. In plants, phenological responses to climate change are often shared among closely related species (i.e. clades), even between geographically disjunct communities. And in some cases, this has resulted in a phylogenetically biased pattern of non-native species success. In birds, the pattern of decline is phylogenetically biased but is not solely explained by phenological response, which suggests that other traits may better explain this pattern. These results illustrate the ways in which phylogenetic thinking can aid in making generalizations of practical importance and enhance efforts to predict species' responses to future climate change. © 2010 The Royal Society.

Souza L.,University of Tennessee at Knoxville | Weltzin J.F.,United States National Phenology Network | Sanders N.J.,University of Tennessee at Knoxville
Journal of Plant Ecology | Year: 2011

Aims: In this study, we examined the effects of Solidago altissima (hereafter Solidago) and two species in the genus Verbesina, Verbesina virginica and Verbesina occidentalis (hereafter Verbesina), on the structure of an old-field plant community and establishment by an invasive plant species, Lespedeza cuneata (hereafter Lespedeza). MethodsWe removed Solidago, Verbesina and both Solidago and Verbesina from 4-m 2 plots in an intact old-field community during two growing seasons. We then quantified the effects of these removals on richness, evenness, diversity and composition of the subdominant plant community. We also measured the total aboveground biomass and the aboveground biomass of the subdominant community. To assess how these removals affected establishment by Lespedeza, we planted 20 seeds in each plot and tracked seedling emergence and survival for one growing season. Important FindingsSubdominant community evenness and Shannon diversity were higher in plots from which Solidago and Verbesina were removed relative to control plots. However, there were no effects of dominant species removal on species richness or composition of the subdominant community. Total aboveground biomass was not affected by dominant species removal, suggesting that the community of subdominant species exhibited compensation. In fact, subdominant community biomass was greater when Solidago, but not Verbesina, was removed. Light availability was also greater in plots where Solidago was removed relative to control plots throughout the growing season. In addition, removal of dominant species, in particular Solidago, indirectly reduced the emergence, but not survival, of Lespedeza seedlings by directly promoting subdominant community biomass. Taken together, our results suggest that dominant old-field plant species affect subdominant community structure and indirectly promote establishment by Lespedeza. © The Author 2010.

Cleland E.E.,University of California at San Diego | Allen J.M.,University of Connecticut | Crimmins T.M.,United States National Phenology Network | Dunne J.A.,Santa Fe Institute | And 5 more authors.
Ecology | Year: 2012

Earlier spring phenology observed in many plant species in recent decades provides compelling evidence that species are already responding to the rising global temperatures associated with anthropogenic climate change. There is great variability among species, however, in their phenological sensitivity to temperature. Species that do not phenologically "track" climate change may be at a disadvantage if their growth becomes limited by missed interactions with mutualists, or a shorter growing season relative to earlieractive competitors. Here, we set out to test the hypothesis that phenological sensitivity could be used to predict species performance in a warming climate, by synthesizing results across terrestrial warming experiments. We assembled data for 57 species across 24 studies where flowering or vegetative phenology was matched with a measure of species performance. Performance metrics included biomass, percent cover, number of flowers, or individual growth. We found that species that advanced their phenology with warming also increased their performance, whereas those that did not advance tended to decline in performance with warming. This indicates that species that cannot phenologically "track" climate may be at increased risk with future climate change, and it suggests that phenological monitoring may provide an important tool for setting future conservation priorities. © 2012 by the Ecological Society of America.

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