Earlier springs decrease peak summer productivity in North American boreal forests
TL;DR: In this paper, the authors analyzed nearly three decades (1982?2008) of observational records and derived products, including satellite microwave and optical imagery as well as upscaled ecosystem flux observations, to better understand how shifts in seasonality impact hydrology and productivity in the North American boreal forests.
Abstract: In the northern high latitudes, alternative hypotheses with regards to how warming-related shifts in seasonality influence ecosystem productivity exist. Increased plant growth associated with a longer growing season may enhance ecosystem productivity, but shifts to earlier springs may also negatively influence soil moisture status and productivity during the peak of the growing season. Here, we analyzed nearly three decades (1982?2008) of observational records and derived products, including satellite microwave and optical imagery as well as upscaled ecosystem flux observations, to better understand how shifts in seasonality impact hydrology and productivity in the North American boreal forests. We identified a dominant adverse influence of earlier springs on peak summer forest greenness, actual evapotranspiration and productivity at interannual time scales across the drier western and central sections of the North American boreal forests. In the vast regions where this spring onset mechanism operates, ecosystem productivity gains from earlier springs during the early portion of the growing season are effectively cancelled through corresponding losses in the later portion. Our results also indicate that recent decadal shifts towards earlier springs and associated drying in the midst of the growing season over western North American boreal forests may have contributed to the reported declines in summer productivity and increases in tree mortality and fire activity. With projections of accelerated northern high-latitude warming and associated shifts to earlier springs, persistent soil moisture deficits in peak summer may be an effective mechanism for regional-scale boreal forest dieback through their strong influence on productivity, tree mortality and disturbance dynamics.
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TL;DR: Wang et al. as mentioned in this paper proposed a hybrid generalized additive model (HGAM) method to extract peak photosynthesis timing (PPT) using the VPM-based gross primary production (GPP) product, and examined the dynamics, drivers, and consequences of PPT changes in temperate and alpine grasslands in China over 2000-2016.
64 citations
Cites background from "Earlier springs decrease peak summe..."
...Specifically, advances in the leaf-out period can lead to premature soil moisture losses (Buermann et al., 2013; Fu et al., 2018)....
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...In contrast, a relationship between an earlier peak and less production has been observed in some North American boreal forests and some temperate regions, mainly in water-limited ecosystems, where the PPT does not occur at the usual time due to water stress in summer, consequently influencing the peak and annual production (Angert et al., 2005; Buermann et al., 2013; Wang et al., 2018b; Wolf et al., 2016)....
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TL;DR: In this article, the authors apply a multivariate anomaly detection approach to a set of hydrometeorological variables, and then to multiple biospheric variables relevant to describe the Russian heatwave.
Abstract: . Combined droughts and heatwaves are among those compound extreme events that induce severe impacts on the terrestrial biosphere and human health. A record breaking hot and dry compound event hit western Russia in summer 2010 (Russian heatwave, RHW). Events of this kind are relevant from a hydrometeorological perspective, but are also interesting from a biospheric point of view because of their impacts on ecosystems, e.g., reductions in the terrestrial carbon storage. Integrating both perspectives might facilitate our knowledge about the RHW. We revisit the RHW from both a biospheric and a hydrometeorological perspective. We apply a recently developed multivariate anomaly detection approach to a set of hydrometeorological variables, and then to multiple biospheric variables relevant to describe the RHW. One main finding is that the extreme event identified in the hydrometeorological variables leads to multidirectional responses in biospheric variables, e.g., positive and negative anomalies in gross primary production (GPP). In particular, the region of reduced summer ecosystem production does not match the area identified as extreme in the hydrometeorological variables. The reason is that forest-dominated ecosystems in the higher latitudes respond with unusually high productivity to the RHW. Furthermore, the RHW was preceded by an anomalously warm spring, which leads annually integrated to a partial compensation of 54 % (36 % in the preceding spring, 18 % in summer) of the reduced GPP in southern agriculturally dominated ecosystems. Our results show that an ecosystem-specific and multivariate perspective on extreme events can reveal multiple facets of extreme events by simultaneously integrating several data streams irrespective of impact direction and the variables' domain. Our study exemplifies the need for robust multivariate analytic approaches to detect extreme events in both hydrometeorological conditions and associated biosphere responses to fully characterize the effects of extremes, including possible compensatory effects in space and time.
63 citations
Cites background from "Earlier springs decrease peak summe..."
...…and (2) the evolution of the summer impacts should consider potential carry-over effects of positive GPP anomalies during spring, as earlier studies showed that earlier spring onset and increased spring GPP may negatively influence soil moisture and thus GPP during summer (Buermann et al., 2013)....
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...In summary, comparing these two Hovmöller diagrams shows that (1) the affected latitudinal range of the negative GPP anomaly is much smaller than the positive temperature anomaly and (2) the evolution of the summer impacts should consider potential carry-over effects of positive GPP anomalies during spring, as earlier studies showed that earlier spring onset and increased spring GPP may negatively influence soil moisture and thus GPP during summer (Buermann et al., 2013)....
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...Buermann et al. (2013) showed that warmer springs going hand in hand with earlier vegetation activity negatively affect soil moisture in summer, and thereby vegetation activity....
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...In particular, Buermann et al. (2013) show for North American boreal forests that earlier springs are followed by reduced productivity in summer because of water constraints....
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...Increased GPP in spring due to warm temperatures can negatively influence soil moisture and thus GPP during summer (Buermann et al., 2013; Wolf et al., 2016; Sippel et al., 2017)....
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TL;DR: In this paper, satellite observations of the contrasting response of trees and grasses to variations in water availability were used to study the effect of water availability on tree and grass growth in the Amazon basin.
Abstract: Published in: Geophysical Research Letters This is the peer reviewed version of the following article: Reference: Walther, S., Duveiller, G., Jung, M., Guanter, L., Cescatti, A., & CampsValls, G. (2019). Satellite observations of the contrasting response of trees and grasses to variations in water availability. Geophysical Research Letters, 46(3), 1429-1440. doi:10.1029/2018GL080535 which has been published in final form at: Web link: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080535 This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
56 citations
Cites background from "Earlier springs decrease peak summe..."
...…(see Figures S7 and S8 and a detailed discussion in supporting information Text S4; Allen et al., 2010; Angert et al., 2005; Barr et al., 2002; Buermann et al., 2013; Buermann et al., 2018; Ciais et al., 2005; Dass et al., 2016; le Maire et al., 2010; Peng et al., 2011; Piao et al., 2014;…...
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TL;DR: Wang et al. as mentioned in this paper extracted start of season (SOS) dates using five standard methods from satellite-derived Normalized Difference Vegetation Index (NDVI) data in temperate China from 1982 to 2015 and explored the spatio-temporal variation in vegetation growth and its linkages to spring phenology and climatic factors.
55 citations
TL;DR: Findings suggest that both climatic factors and spring phenology should be incorporated into autumn phenology models in order to improve prediction accuracy under present and future climate change scenarios.
Abstract: Vegetation phenology plays a key role in terrestrial ecosystem nutrient and carbon cycles and is sensitive to global climate change. Compared with spring phenology, which has been well studied, autumn phenology is still poorly understood. In this study, we estimated the date of the end of the growing season (EOS) across the Greater Khingan Mountains, China, from 1982 to 2015 based on the Global Inventory Modeling and Mapping Studies (GIMMS) normalized difference vegetation index third-generation (NDVI3g) dataset. The temporal correlations between EOS and climatic factors (e.g., preseason temperature, preseason precipitation), as well as the correlation between autumn and spring phenology, were investigated using partial correlation analysis. Results showed that more than 94% of the pixels in the Greater Khingan Mountains exhibited a delayed EOS trend, with an average rate of 0.23 days/y. Increased preseason temperature resulted in earlier EOS in most of our study area, except for the semi-arid grassland region in the south, where preseason warming generally delayed EOS. Similarly, EOS in most of the mountain deciduous coniferous forest, forest grassland, and mountain grassland forest regions was earlier associated with increased preseason precipitation, but for the semi-arid grassland region, increased precipitation during the preseason mainly led to delayed EOS. However, the effect of preseason precipitation on EOS in most of the Greater Khingan Mountains was stronger than that of preseason temperature. In addition to the climatic effects on EOS, we also found an influence of spring phenology on EOS. An earlier SOS led to a delayed EOS in most of the study area, while in the southern of mountain deciduous coniferous forest region and northern of semi-arid grassland region, an earlier SOS was often followed by an earlier EOS. These findings suggest that both climatic factors and spring phenology should be incorporated into autumn phenology models in order to improve prediction accuracy under present and future climate change scenarios.
54 citations
Cites background from "Earlier springs decrease peak summe..."
...Second, earlier springs may result in soil water losses via increases in snow sublimation and evapotranspiration in the early part of the growing season; thus, summer and autumn drought duration may increase, leading to earlier EOS dates [71]....
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01 Jan 2007
TL;DR: The first volume of the IPCC's Fourth Assessment Report as mentioned in this paper was published in 2007 and covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
Abstract: This report is the first volume of the IPCC's Fourth Assessment Report. It covers several topics including the extensive range of observations now available for the atmosphere and surface, changes in sea level, assesses the paleoclimatic perspective, climate change causes both natural and anthropogenic, and climate models for projections of global climate.
32,826 citations
Book•
01 Jan 2007
TL;DR: In this article, the authors present a historical overview of climate change science, including changes in atmospheric constituents and radiative forcing, as well as changes in snow, ice, and frozen ground.
Abstract: Summary for policymakers -- Technical summary -- Historical overview of climate change science -- Changes in atmospheric constituents and radiative forcing -- Observations: atmospheric surface and climate change -- Observations: changes in snow, ice, and frozen ground -- Observations: ocean climate change and sea level -- Paleoclimate -- Coupling between changes in the climate system and biogeochemistry -- Climate models and their evaluation -- Understanding and attributing climate change -- Global climate projections -- Regional climate projections -- Annex I: Glossary -- Annex II: Contributors to the IPCC WGI Fourth Assessment Report -- Annex III: Reviewers of the IPCC WGI Fourth Assessment Report -- Annex IV: Acronyms.
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United States Geological Survey1, University of Arizona2, University of Batna3, Oregon State University4, Los Alamos National Laboratory5, Centre national de la recherche scientifique6, Swiss Federal Institute for Forest, Snow and Landscape Research7, Natural Resources Canada8, University of California, Berkeley9, University of Granada10, Northern Research Institute11, Forest Research Institute12, Food and Agriculture Organization13, University of Montana14, Northern Arizona University15
TL;DR: In this paper, the authors present the first global assessment of recent tree mortality attributed to drought and heat stress and identify key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system.
5,811 citations
TL;DR: In this article, a new climatic drought index, the standardized precipitation evapotranspiration index (SPEI), is proposed, which combines multiscalar character with the capacity to include the effects of temperature variability on drought assessment.
Abstract: The authors propose a new climatic drought index: the standardized precipitation evapotranspiration index (SPEI). The SPEI is based on precipitation and temperature data, and it has the advantage of combining multiscalar character with the capacity to include the effects of temperature variability on drought assessment. The procedure to calculate the index is detailed and involves a climatic water balance, the accumulation of deficit/surplus at different time scales, and adjustment to a log-logistic probability distribution. Mathematically, the SPEI is similar to the standardized precipitation index (SPI), but it includes the role of temperature. Because the SPEI is based on a water balance, it can be compared to the self-calibrated Palmer drought severity index (sc-PDSI). Time series of the three indices were compared for a set of observatories with different climate characteristics, located in different parts of the world. Under global warming conditions, only the sc-PDSI and SPEI identified an...
5,088 citations