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  • 1
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    Emerging opportunities and challenges in phenology : a review (2016)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecosphere 7 (2016): e01436, doi:10.1002/ecs2.1436.
    Description: Plant phenology research has gained increasing attention because of the sensitivity of phenology to climate change and its consequences for ecosystem function. Recent technological development has made it possible to gather invaluable data at a variety of spatial and ecological scales. Despite our ability to observe phenological change at multiple scales, the mechanistic basis of phenology is still not well understood. Integration of multiple disciplines, including ecology, evolutionary biology, climate science, and remote sensing, with long-term monitoring data across multiple spatial scales is needed to advance understanding of phenology. We review the mechanisms and major drivers of plant phenology, including temperature, photoperiod, and winter chilling, as well as other factors such as competition, resource limitation, and genetics. Shifts in plant phenology have significant consequences on ecosystem productivity, carbon cycling, competition, food webs, and other ecosystem functions and services. We summarize recent advances in observation techniques across multiple spatial scales, including digital repeat photography, other complementary optical measurements, and solar-induced fluorescence, to assess our capability to address the importance of these scale-dependent drivers. Then, we review phenology models as an important component of earth system modeling. We find that the lack of species-level knowledge and observation data leads to difficulties in the development of vegetation phenology models at ecosystem or community scales. Finally, we recommend further research to advance understanding of the mechanisms governing phenology and the standardization of phenology observation methods across networks. With the opportunity for “big data” collection for plant phenology, we envision a breakthrough in process-based phenology modeling.
    Description: U.S. National Science Foundation Grant Numbers: PLR-1417763, DBI-959333, AGS-1005663; University of Chicago and the MBL Lillie Research Innovation Award; NEXT Program; KAKENHI (MEXT, Japan); National Science Foundation of China Grant Number: 41571103; NERC Grant Number: NE/J02080X/1
    Keywords: Cameras ; Greenness ; ILTER ; Modeling ; Phenology ; Scale ; International LTER
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Effect of growth temperature on photosynthetic capacity and respiration in three ecotypes of Eriophorum vaginatum (2018)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecology and Evolution 8 (2018): 3711-3725, doi:10.1002/ece3.3939.
    Description: Ecotypic differentiation in the tussock‐forming sedge Eriophorum vaginatum has led to the development of populations that are locally adapted to climate in Alaska's moist tussock tundra. As a foundation species, E. vaginatum plays a central role in providing topographic and microclimatic variation essential to these ecosystems, but a changing climate could diminish the importance of this species. As Arctic temperatures have increased, there is evidence of adaptational lag in E. vaginatum, as locally adapted ecotypes now exhibit reduced population growth rates. Whether there is a physiological underpinning to adaptational lag is unknown. Accordingly, this possibility was investigated in reciprocal transplant gardens. Tussocks of E. vaginatum from sites separated by ~1° latitude (Coldfoot: 67°15′N, Toolik Lake: 68°37′, Sagwon: 69°25′) were transplanted into the Toolik Lake and Sagwon sites and exposed to either an ambient or an experimental warming treatment. Five tussocks pertreatment combination were measured at each garden to determine photosynthetic capacity (i.e., Vcmax and Jmax) and dark respiration rate (Rd) at measurement temperatures of 15, 20, and 25°C. Photosynthetic enhancements or homeostasis were observed for all ecotypes at both gardens under increased growth temperature, indicating no negative effect of elevated temperature on photosynthetic capacity. Further, no evidence of thermal acclimation in Rd was observed for any ecotype, and there was little evidence of ecotypic variation in Rd. As such, no physiological contribution to adaptational lag was observed given the increase in growth temperature (up to ~2°C) provided by this study. Despite neutral to positive effects of increased growth temperature on photosynthesis in E. vaginatum, it appears to confer no lasting advantage to the species.
    Description: Division of Polar Programs Grant Numbers: 1417645, 1417763, 1418010; West Chester University, Department of Biology
    Keywords: Adaptational lag ; Eriophorum vaginatum ; Moist tussock tundra ; Photosynthetic capacity ; Respiration ; Temperature acclimation
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Relationship between leaf physiologic traits and canopy color indices during the leaf expansion period in an oak forest (2016)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecosphere 6, no. 12 (2015): 1-9, doi:10.1890/ES14-00452.1.
    Description: Plant phenology has a significant impact on the forest ecosystem carbon balance. Detecting plant phenology by capturing the time-series canopy images through digital camera has become popular in recent years. However, the relationship between color indices derived from camera images and plant physiological characters are elusive during the growing season in temperate ecosystems. We collected continuous images of forest canopy, leaf size, leaf area index (LAI) and leaf chlorophyll measured by a soil plant analysis development (SPAD) analyzer in a northern subtropical oak forest in China. Our results show that (1) the spring peak of color indices, Gcc (Green Chromatic Coordinates) and ExG (Excess Green), was 18 days earlier than the 90% maximum SPAD value; (2) the 90% maximum SPAD value coincided with the change point of Gcc and ExG immediately after their spring peak; and (3) the spring curves of Gcc and ExG before their peaks were highly synchronous with the expansion of leaf size and the development of LAI value. We suggest it needs to be adjusted if camera-derived Gcc or ExG is used as a proxy of chlorophyll or gross primary productivity, and images observation should be complemented with field phenological and physiological information to interpret the physiological meaning of leaf seasonality.
    Description: This research was funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions in the Discipline of Environmental Science and Engineering at Nanjing Forest University, Changjiang River Delta Urban Forest Ecosystem Research of CFERN (to H. Hu) and Brown University Seed Funds for International Research Projects on the Environment (to J. Tang).
    Keywords: Chlorophyll ; Greenness indices ; Leaf area index ; Leaf sizes ; Phenology ; Plant images
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Environmental controls, emergent scaling, and predictions of greenhouse gas (GHG) fluxes in coastal salt marshes (2018)
    John Wiley & Sons
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    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 123 (2018): 2234-2256, doi:10.1029/2018JG004556.
    Description: Coastal salt marshes play an important role in mitigating global warming by removing atmospheric carbon at a high rate. We investigated the environmental controls and emergent scaling of major greenhouse gas (GHG) fluxes such as carbon dioxide (CO2) and methane (CH4) in coastal salt marshes by conducting data analytics and empirical modeling. The underlying hypothesis is that the salt marsh GHG fluxes follow emergent scaling relationships with their environmental drivers, leading to parsimonious predictive models. CO2 and CH4 fluxes, photosynthetically active radiation (PAR), air and soil temperatures, well water level, soil moisture, and porewater pH and salinity were measured during May–October 2013 from four marshes in Waquoit Bay and adjacent estuaries, MA, USA. The salt marshes exhibited high CO2 uptake and low CH4 emission, which did not significantly vary with the nitrogen loading gradient (5–126 kg · ha−1 · year−1) among the salt marshes. Soil temperature was the strongest driver of both fluxes, representing 2 and 4–5 times higher influence than PAR and salinity, respectively. Well water level, soil moisture, and pH did not have a predictive control on the GHG fluxes, although both fluxes were significantly higher during high tides than low tides. The results were leveraged to develop emergent power law‐based parsimonious scaling models to accurately predict the salt marsh GHG fluxes from PAR, soil temperature, and salinity (Nash‐Sutcliffe Efficiency = 0.80–0.91). The scaling models are available as a user‐friendly Excel spreadsheet named Coastal Wetland GHG Model to explore scenarios of GHG fluxes in tidal marshes under a changing climate and environment.
    Description: National Oceanic and Atmospheric Administration Grant Numbers: NA09NOS4190153, NA14NOS4190145; National Science Foundation (NSF) Grant Numbers: 1705941, 1561941/1336911; USGS LandCarbon Program; NOAA National Estuarine Research Reserve Science Collaborative Grant Number: NA09NOS4190153 and NA14NOS4190145
    Description: 2019-01-28
    Keywords: Coastal salt marshes ; GHG fluxes ; Environmental controls ; Emergent scaling ; Modeling and predictions
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Evaluation of laser-based spectrometers for greenhouse gas flux measurements in coastal marshes (2016)
    John Wiley & Sons
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Limnology and Oceanography: Methods 14 (2016): 466–476, doi:10.1002/lom3.10105.
    Description: Precise and rapid analyses of greenhouse gases (GHGs) will advance understanding of the net climatic forcing of coastal marsh ecosystems. We examined the ability of a cavity ring down spectroscopy (CRDS) analyzer (Model G2508, Picarro) to measure carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes in real-time from coastal marshes through comparisons with a Shimadzu GC-2014 (GC) in a marsh mesocosm experiment and with a similar laser-based N2O analyzer (Model N2O/CO, Los Gatos Research) in both mesocosm and field experiments. Minimum (analytical) detectable fluxes for all gases were more than one order of magnitude lower for the Picarro than the GC. In mesocosms, the Picarro analyzer detected several CO2, CH4, and N2O fluxes that the GC could not, but larger N2O fluxes (218–409 μmol m−2 h−1) were similar between analyzers. Minimum detectable fluxes for the Picarro were 1 order of magnitude higher than the Los Gatos analyzer for N2O. The Picarro and Los Gatos N2O fluxes (3–132 μmol m−2 h−1) differed in two mesocosm nitrogen addition experiments, but were similar in a mesocosm with larger N2O fluxes (326–491 μmol m−2 h−1). In a field comparison, Picarro and Los Gatos N2O fluxes (13 ± 2 μmol m−2 h−1) differed in plots receiving low nitrogen loads but were similar in plots with higher nitrogen loads and fluxes roughly double in magnitude. Both the Picarro and Los Gatos analyzers offer efficient and precise alternatives to GC-based methods, but the former uniquely enables simultaneous measurements of three major GHGs in coastal marshes.
    Description: This study was funded by the USDA National Institute of Food and Agriculture (Hatch project # 229286, grant to Moseman-Valtierra) and a Woods Hole Sea Grant award to Moseman-Valtierra and Tang.
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Beyond leaf color : comparing camera-based phenological metrics with leaf biochemical, biophysical, and spectral properties throughout the growing season of a temperate deciduous forest (2014)
    John Wiley & Sons
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    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 119 (2014): 181-191, doi:10.1002/2013JG002460.
    Description: Plant phenology, a sensitive indicator of climate change, influences vegetation-atmosphere interactions by changing the carbon and water cycles from local to global scales. Camera-based phenological observations of the color changes of the vegetation canopy throughout the growing season have become popular in recent years. However, the linkages between camera phenological metrics and leaf biochemical, biophysical, and spectral properties are elusive. We measured key leaf properties including chlorophyll concentration and leaf reflectance on a weekly basis from June to November 2011 in a white oak forest on the island of Martha's Vineyard, Massachusetts, USA. Concurrently, we used a digital camera to automatically acquire daily pictures of the tree canopies. We found that there was a mismatch between the camera-based phenological metric for the canopy greenness (green chromatic coordinate, gcc) and the total chlorophyll and carotenoids concentration and leaf mass per area during late spring/early summer. The seasonal peak of gcc is approximately 20 days earlier than the peak of the total chlorophyll concentration. During the fall, both canopy and leaf redness were significantly correlated with the vegetation index for anthocyanin concentration, opening a new window to quantify vegetation senescence remotely. Satellite- and camera-based vegetation indices agreed well, suggesting that camera-based observations can be used as the ground validation for satellites. Using the high-temporal resolution dataset of leaf biochemical, biophysical, and spectral properties, our results show the strengths and potential uncertainties to use canopy color as the proxy of ecosystem functioning.
    Description: This research was supported by the Brown University– Marine Biological Laboratory graduate program in Biological and Environmental Sciences, Brown–ECI phenology working group, Brown Office of International Affairs Seed Grant on phenology, and Marine Biological Laboratory start-up funding for JT.
    Description: 2014-09-30
    Keywords: Green-up ; Senescence ; Phenology ; Leaf physiology ; Chlorophyll ; Vegetation spectroscopy
    Repository Name: Woods Hole Open Access Server
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  • 7
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    Carbon dioxide fluxes reflect plant zonation and belowground biomass in a coastal marsh (2017)
    John Wiley & Sons
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecosphere 7 (2016): e01560, doi:10.1002/ecs2.1560.
    Description: Coastal wetlands are major global carbon sinks; however, they are heterogeneous and dynamic ecosystems. To characterize spatial and temporal variability in a New England salt marsh, greenhouse gas (GHG) fluxes were compared among major plant-defined zones during growing seasons. Carbon dioxide (CO2) and methane (CH4) fluxes were compared in two mensurative experiments during summer months (2012–2014) that included low marsh (Spartina alterniflora), high marsh (Distichlis spicata and Juncus gerardii-dominated), invasive Phragmites australis zones, and unvegetated ponds. Day- and nighttime fluxes were also contrasted in the native marsh zones. N2O fluxes were measured in parallel with CO2 and CH4 fluxes, but were not found to be significant. To test the relationships of CO2 and CH4 fluxes with several native plant metrics, a multivariate nonlinear model was used. Invasive P. australis zones (−7 to −15 μmol CO2·m−2·s−1) and S. alterniflora low marsh zones (up to −14 μmol CO2·m−2·s−1) displayed highest average CO2 uptake rates, while those in the native high marsh zone (less than −2 μmol CO2·m−2·s−1) were much lower. Unvegetated ponds were typically small sources of CO2 to the atmosphere (〈0.5 μmol CO2·m−2·s−1). Nighttime emissions of CO2 averaged only 35% of daytime uptake in the low marsh zone, but they exceeded daytime CO2 uptake by up to threefold in the native high marsh zone. Based on modeling, belowground biomass was the plant metric most strongly correlated with CO2 fluxes in native marsh zones, while none of the plant variables correlated significantly with CH4 fluxes. Methane fluxes did not vary between day and night and did not significantly offset CO2 uptake in any vegetated marsh zones based on sustained global warming potential calculations. These findings suggest that attention to spatial zonation as well as expanded measurements and modeling of GHG emissions across greater temporal scales will help to improve accuracy of carbon accounting in coastal marshes.
    Description: NOAA National Estuarine Research Reserve Science Collaborative Grant Number: 03354; USDA National Institute of Food and Agriculture, Hatch Project Grant Number: 229286; National Science Foundation Grant Number: 1561941/1336911; NOAA NERRA Grant Number: NA09NOS4190153; National Science Foundation Experimental Program to Stimulate Collaborative Research Cooperative Agreement Grant Number: EPS-1004057
    Keywords: Biological invasion ; Blue carbon ; Emissions ; Global climate changes ; Juncus gerardii ; Methane ; Nitrous oxide ; Sea-level rise ; Spartina alterniflora
    Repository Name: Woods Hole Open Access Server
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  • 8
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    Ecotypic differences in the phenology of the tundra species Eriophorum vaginatum reflect sites of origin (2017)
    John Wiley & Sons
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    Publication Date: 2022-05-26
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecology and Evolution 7 (2017): 9775–9786, doi:10.1002/ece3.3445.
    Description: Eriophorum vaginatum is a tussock-forming sedge that contributes significantly to the structure and primary productivity of moist acidic tussock tundra. Locally adapted populations (ecotypes) have been identified across the geographical distribution of E. vaginatum; however, little is known about how their growth and phenology differ over the course of a growing season. The growing season is short in the Arctic and therefore exerts a strong selection pressure on tundra species. This raises the hypothesis that the phenology of arctic species may be poorly adapted if the timing and length of the growing season change. Mature E. vaginatum tussocks from across a latitudinal gradient (65–70°N) were transplanted into a common garden at a central location (Toolik Lake, 68°38′N, 149°36′W) where half were warmed using open-top chambers. Over two growing seasons (2015 and 2016), leaf length was measured weekly to track growth rates, timing of senescence, and biomass accumulation. Growth rates were similar across ecotypes and between years and were not affected by warming. However, southern populations accumulated significantly more biomass, largely because they started to senesce later. In 2016, peak biomass and senescence of most populations occurred later than in 2015, probably induced by colder weather at the beginning of the growing season in 2016, which caused a delayed start to growth. The finish was delayed as well. Differences in phenology between populations were largely retained between years, suggesting that the amount of time that these ecotypes grow has been selected by the length of the growing seasons at their respective home sites. As potential growing seasons lengthen, E. vaginatum may be unable to respond appropriately as a result of genetic control and may have reduced fitness in the rapidly warming Arctic tundra.
    Description: National Science Foundation Grant Numbers: 1417645, 1417763, 1418010
    Keywords: Arctic tundra ; Common garden ; Ecotypes ; Eriophorum vaginatum ; Growing season length ; Local adaptation ; Phenology ; Senescence
    Repository Name: Woods Hole Open Access Server
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