Is the grass always greener? Land surface phenology reveals differences in peak and season‐long vegetation productivity responses to climate and management

Wood, David J. A.; Powell, Scott; Stoy, Paul C.; Thurman, Lindsey L.; Beever, Erik A.

doi:10.1002/ece3.7904

Cited by 9 publications

(13 citation statements)

References 90 publications

(197 reference statements)

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“…Similarly, that peak NDVI had the lowest variance explained by climatological changes in our models may indicate that peak NDVI is more sensitive to interannual‐to‐annual climate variability than mean NDVI or LAI, both of which were better explained by our random forest models. These differences in model responses across greening variables highlight the importance of examining multiple greening metrics to capture the various aspects of phenology when examining greening phenomena of large‐scale vegetative changes (Wood et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Large contribution of woody plant expansion to recent vegetative greening of the Northern Great Plains

Currey

McWethy

Fox

et al. 2022

Journal of Biogeography

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Aim Extensive portions of high‐latitude grasslands worldwide have recently experienced increased vegetative productivity (i.e., greening) and have undergone a rapid transition towards woody plant dominance via the process of woody plant expansion (WPE). This raises the underlying question: To what degree are WPE and greening spatiotemporally linked? Given that these vegetative changes are predicted to continue, we seek to understand how recent changes in vegetation extent and productivity have interacted under recent climate change and anthropogenic disturbance to provide insights surrounding the future trajectory of temperate grasslands broadly. Location Northern Great Plains (NGP), North America. Taxon Woody plants. Methods Greening was measured as the significant increase in three metrics between 2000 and 2019: leaf area index (LAI), annual maximum normalized difference vegetative index (NDVI) and annual mean NDVI. WPE was measured as the significant proportional increase in percent tree cover change between 2000 and 2019 in grasslands. We then examined these variables across a host of 26 potential driving variables. Results We show that average proportional greening increased by 0.2–1.3% year−1 (depending on metric), and proportional WPE increased by 6.9% year−1 since 2000 across the NGP. Both changes are largely driven by the absence of wildfire and changing climate. Furthermore, WPE was spatially coherent and positively associated with a large component of recent greening, as revealed by their coupling across 34.1%–40.6% of grassland area and as evidenced by the 9.7%–19.7% of the variability in greening explained by WPE. Main conclusions WPE and greening are spatiotemporally coupled across large portions of the NGP. Under continued climate change and wildfire suppression, WPE and greening are likely to continue across large swathes of grasslands globally. Furthermore, our results show that using a single greening metric may be insufficient to capture the large‐scale vegetative changes such as the expansion of woody vegetation.

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Section: Discussionmentioning

confidence: 99%

Large contribution of woody plant expansion to recent vegetative greening of the Northern Great Plains

Currey

McWethy

Fox

et al. 2022

Journal of Biogeography

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“…North American grassland productivity is predicted to increase due to vegetation responses to future climatic variability (Hufkens et al., 2016) despite well‐documented increases in aridity (Novick et al., 2016). Widespread greening has already been observed across the Northern Great Plains (Brookshire et al., 2020), but the growing season across many surrounding montane regions has become shorter due to hydrologic stress (Wood et al., 2021), with implications for biogeochemical cycling and ecosystem functioning. Late‐season productivity, for example, has declined by over 50% since the late 1960s at a well‐studied montane grassland site in the US Northern Rocky Mountains due to increases in aridity (Brookshire & Weaver, 2015), despite regional climate changes that are often favorable for plant growth (Bromley et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

Ecosystem Gross Primary Productivity After Autumn Snowfall and Melt Events in a Mountain Meadow

et al. 2022

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Vegetation productivity is increasing in the U.S. Northern Great Plains but decreasing in some nearby Northern Rocky Mountain grasslands due to increases in aridity. It is unclear if decreases to montane grassland productivity from drying autumns can be partly offset by late‐season green‐ups after precipitation events. These include the multiple snowfall and snowmelt periods that often characterize the summer‐to‐winter transition, but are difficult to observe due to logistical constraints. Here, we quantify changes to vegetation indices and ecosystem carbon uptake that occurs after snowfall and melt in climatological autumn in a montane grassland in Montana, USA using eddy covariance, phenological camera, and remote sensing analyses. Carbon dioxide flux follows a diurnal pattern after autumn snowmelt events despite overall ecosystem C loss, suggesting that post‐snowmelt photosynthesis helps dampen C loss during autumn and provides fresh photosynthate to support ecosystem functioning. Light‐saturated photosynthesis after three snow events was not statistically different than before snowfall (∼6 μmol CO2 m−2 s−1 in 2016 and ∼2.5 μmol CO2 m−2 s−1 in 2017). Observations are consistent with the notion that canopy photosynthesis is resistant, rather than resilient, to autumn snow. MODIS indicates that post‐snow greenups can occur, but not every year. Such events likely play a small role in the annual ecosystem carbon balance but may be disproportionately important for organisms faced with dwindling late‐season forage. Future efforts should seek to understand the community and ecosystem consequences of vegetation functioning during autumn as part of an expanded effort to understand phenological changes during this under‐studied and changing time of year.

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“…Globally, increased VPD has constrained increases in productivity (Yuan et al, 2019), and is an important driver of stomatal conductance and plant responses Zhang Q. et al, 2019;Fu et al, 2022). The factors that most strongly govern phenological aspects vary across space, and among different vegetation communities (Xia et al, 2015;Fu et al, 2017;Maurer et al, 2020;Wood et al, 2021). Furthermore, climatic controls on phenology are complex, may interact, and can be non-linear (Ponce-Campos et al, 2013;Knapp et al, 2015;Al-Yaari et al, 2020;Gao et al, 2020;Maurer et al, 2020), and ecosystems may respond to far more than just current conditions as they develop.…”

Section: Introductionmentioning

confidence: 99%

“…The U.S. Northwestern Great Plains (NWP) constitute an excellent region to study phenology, given that they contain a wide range of values for abiotic and biotic factors including climate, vegetation communities, and soils (USDA Natural Resources Conservation Service, 2006). For example, the area has large variability in productivity across years (Petrie et al, 2016); is experiencing changing seasonality (Ren et al, 2020); and has spatial and land cover variability in phenological drivers (Wood et al, 2021). The region also has experienced unique changes to climate in the last few decades (Bromley et al, 2020), and has ongoing land-use changes (Auch et al, 2011;Stoy et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Antecedent climatic conditions spanning several years influence multiple land-surface phenology events in semi-arid environments

et al. 2022

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Ecological processes are complex, often exhibiting non-linear, interactive, or hierarchical relationships. Furthermore, models identifying drivers of phenology are constrained by uncertainty regarding predictors, interactions across scales, and legacy impacts of prior climate conditions. Nonetheless, measuring and modeling ecosystem processes such as phenology remains critical for management of ecological systems and the social systems they support. We used random forest models to assess which combination of climate, location, edaphic, vegetation composition, and disturbance variables best predict several phenological responses in three dominant land cover types in the U.S. Northwestern Great Plains (NWP). We derived phenological measures from the 25-year series of AVHRR satellite data and characterized climatic predictors (i.e., multiple moisture and/or temperature based variables) over seasonal and annual timeframes within the current year and up to 4 years prior. We found that antecedent conditions, from seasons to years before the current, were strongly associated with phenological measures, apparently mediating the responses of communities to current-year conditions. For example, at least one measure of antecedent-moisture availability [precipitation or vapor pressure deficit (VPD)] over multiple years was a key predictor of all productivity measures. Variables including longer-term lags or prior year sums, such as multi-year-cumulative moisture conditions of maximum VPD, were top predictors for start of season. Productivity measures were also associated with contextual variables such as soil characteristics and vegetation composition. Phenology is a key process that profoundly affects organism-environment relationships, spatio-temporal patterns in ecosystem structure and function, and other ecosystem dynamics. Phenology, however, is complex, and is mediated by lagged effects, interactions, and a diversity of potential drivers; nonetheless, the incorporation of antecedent conditions and contextual variables can improve models of phenology.

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Is the grass always greener? Land surface phenology reveals differences in peak and season‐long vegetation productivity responses to climate and management

Abstract: This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Cited by 9 publications

References 90 publications

Large contribution of woody plant expansion to recent vegetative greening of the Northern Great Plains

Large contribution of woody plant expansion to recent vegetative greening of the Northern Great Plains

Ecosystem Gross Primary Productivity After Autumn Snowfall and Melt Events in a Mountain Meadow

Antecedent climatic conditions spanning several years influence multiple land-surface phenology events in semi-arid environments

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