Abrupt shifts in phenology and vegetation productivity under climate extremes

Ma, Xuanlong; Huete, Alfredo; Moran, Susan; Ponce‐Campos, Guillermo E.; Eamus, Derek

doi:10.1002/2015jg003144

Cited by 174 publications

(164 citation statements)

References 62 publications

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“…The remote sensing-based ESA is sensitive to the intensity of water stress [58], so we employed it as an indicator to represent the drought response of forests. To distinguish the normal variation in the ESA from the significant decreases in the ESA caused by water limitation stress, we focused our analysis on the forest grids where the ESA was lower than certain thresholds, calculated using Matlab (R2012b).…”

Section: Drought Intensity-related Indicatorsmentioning

confidence: 99%

Contrasting Responses of Planted and Natural Forests to Drought Intensity in Yunnan, China

Luo

Zhou

et al. 2016

Remote Sensing

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Abstract:In recent decades, the area and proportion of planted forests have increased; thus, understanding the responses of planted and natural forests to drought are crucial because it forms the basis for forest risk assessments and management strategies. In this study, we combined the moderate-resolution imaging spectroradiometer (MODIS) enhanced vegetation index (EVI), meteorological aridity indices, and standardized precipitation evapotranspiration indices (SPEI) to identify the drought responses of planted and natural forests. In particular, we used the EVI standard anomaly (ESA) as a physiological drought indicator and analyzed the applicability of SPEIs at time scales of 1-30 months, thereby determining the optimal time scale for the SPEI (SPEI opt ), i.e., the SPEI that best represents the drought responses of forests in Yunnan. Next, we employed the optimal SPEI and the ESA as indices to statistically analyze the response characteristics of planted and natural forests under different drought intensities. The results indicated the following: (1) The SPEI in June and a time scale of five months (i.e., SPEI Jun,5 ) comprise the optimal meteorological aridity indicator for forests in Yunnan Province, which had the strongest correlation with the EVI standard anomaly (ESA Jun ). (2) All forest types were affected by drought in Yunnan, but their responses varied according to the forest type, elevation, and drought intensity. In general, natural forests are more vulnerable and sensitive to drought than planted forests, especially natural coniferous forests at low (0-2000 m) and moderate (2000-4000 m) altitudes, and natural mixed forest at low altitudes (0-2000 m). (3) The remote sensing-based ESA (ESA Jun ) is sensitive to the intensity of water stress, which makes it a good indicator for drought monitoring. In addition, the forests' inventory survey revealed that 8.05% of forests were affected by drought; thus, we used this as a guide to estimate an approximate threshold to map forest responses to drought across the region. Below this approximate threshold (i.e., ESA Jun <´3.85), severe drought-induced effects on forests may occur. Given that natural forests are more vulnerable and sensitive to drought than the planted forests, natural forests need more careful management, especially in the context of projected increases in extreme drought events in the future.

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Section: Drought Intensity-related Indicatorsmentioning

confidence: 99%

Contrasting Responses of Planted and Natural Forests to Drought Intensity in Yunnan, China

Luo

Zhou

et al. 2016

Remote Sensing

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“…While the traditional definition of the term phenology as the "timing of recurrent biological events" (Lieth, 1974) is generally assumed to apply to seasonally cyclical events, such as canopy bud burst and senescence in winter-deciduous forests, a closer look at life patterns in many Australian biomes yields a more complex picture of non-seasonal, yet still periodic, events as the major drivers of phenology (Specht and Brouwer, 1975;Pook et al, 1997;Ma et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Reviews and syntheses: Australian vegetation phenology: new insights from satellite remote sensing and digital repeat photography

et al. 2016

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Abstract. Phenology is the study of periodic biological occurrences and can provide important insights into the influence of climatic variability and change on ecosystems. Understanding Australia's vegetation phenology is a challenge due to its diverse range of ecosystems, from savannas and tropical rainforests to temperate eucalypt woodlands, semiarid scrublands, and alpine grasslands. These ecosystems exhibit marked differences in seasonal patterns of canopy development and plant life-cycle events, much of which deviates from the predictable seasonal phenological pulse of temperate deciduous and boreal biomes. Many Australian ecosystems are subject to irregular events (i.e. drought, flooding, cyclones, and fire) that can alter ecosystem composition, structure, and functioning just as much as seasonal change. We show how satellite remote sensing and ground-based digital repeat photography (i.e. phenocams) can be used to improve understanding of phenology in Australian ecosystems. First, we examine temporal variation in phenology on the continental scale using the enhanced vegetation index (EVI), calculated from MODerate resolution Imaging Spectroradiometer (MODIS) data. Spatial gradients are revealed, ranging from regions with pronounced seasonality in canopy development (i.e. tropical savannas) to regions where seasonal variation is minimal (i.e. tropical rainforests) or high but irregular (i.e. arid ecosystems). Next, we use time series colour information extracted from phenocam imagery to illustrate a range of phenological signals in four contrasting Australian ecosystems. These include greening and senescing events in tropical savannas and temperate eucalypt understorey, as well as strong seasonal dynamics of individual trees in a seemingly static evergreen rainforest. We also demonstrate how phenology links with ecosystem gross primary productivity (from eddy covariance) and discuss why these processes are linked in some ecosystems but not others. We conclude that phenocams have the potential to greatly improve the current understanding of Australian ecosystems. To facilitate the sharing of this information, we have formed the Australian Phenocam Network (http://phenocam.org.au/).

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“…One reason for this particular sensitivity could be the following. As crops are meant to produce a maximum yield, they often demand high standards in nurturing and water availability and are vulnerable to sudden changes (Semenov and Shewry, 2011;Ma et al, 2015). As already discussed in the Introduction, extreme temperatures can cause substantial losses in crop yields (see, e.g., Schaap et al, 2011;Lesk et al, 2011;Moriondo et al, 2010;Wreford and Adger, 2010).…”

Section: May-junementioning

confidence: 99%

Impacts of temperature extremes on European vegetation during the growing season

et al. 2017

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Abstract. Temperature is a key factor controlling plant growth and vitality in the temperate climates of the midlatitudes like in vast parts of the European continent. Beyond the effect of average conditions, the timings and magnitudes of temperature extremes play a particularly crucial role, which needs to be better understood in the context of projected future rises in the frequency and/or intensity of such events. In this work, we employ event coincidence analysis (ECA) to quantify the likelihood of simultaneous occurrences of extremes in daytime land surface temperature anomalies (LSTAD) and the normalized difference vegetation index (NDVI). We perform this analysis for entire Europe based upon remote sensing data, differentiating between three periods corresponding to different stages of plant development during the growing season. In addition, we analyze the typical elevation and land cover type of the regions showing significantly large event coincidences rates to identify the most severely affected vegetation types. Our results reveal distinct spatio-temporal impact patterns in terms of extraordinarily large co-occurrence rates between several combinations of temperature and NDVI extremes. Croplands are among the most frequently affected land cover types, while elevation is found to have only a minor effect on the spatial distribution of corresponding extreme weather impacts. These findings provide important insights into the vulnerability of European terrestrial ecosystems to extreme temperature events and demonstrate how event-based statistics like ECA can provide a valuable perspective on environmental nexuses.

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Abrupt shifts in phenology and vegetation productivity under climate extremes

Cited by 174 publications

References 62 publications

Contrasting Responses of Planted and Natural Forests to Drought Intensity in Yunnan, China

Contrasting Responses of Planted and Natural Forests to Drought Intensity in Yunnan, China

Reviews and syntheses: Australian vegetation phenology: new insights from satellite remote sensing and digital repeat photography

Impacts of temperature extremes on European vegetation during the growing season

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