Landsat Image Analysis of Tree Mortality in the Southern Sierra Nevada Region of California during the 2013-2015 Drought

Potter, Christopher S.

doi:10.4172/2157-7617.1000342

Cited by 15 publications

(16 citation statements)

References 47 publications

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“…Caspar NDVI values are near the saturation limit of approximately 0.90 [52], which may be limiting the ability to detect vegetation changes and likely contributes to the extremely low standard deviation. The lowest NDVI and EVI values for mixed rain and snow Providence and snow-dominated Bull occur during 2014-2016, coinciding with drought-related canopy water loss [53] and tree mortality [46]. In contrast, the lowest NDVI value for Caspar occurs in 2004, while the lowest EVI value occurs in 2016, which may reflect the lower sensitivity of NDVI and the higher sensitivity of EVI in regions of high biomass [52].…”

Section: Vegetation Indicesmentioning

confidence: 72%

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Recent Patterns in Climate, Vegetation, and Forest Water Use in California Montane Watersheds

Saksa

Safeeq

Dymond

2017

Forests

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California has recently experienced one of the worst droughts on record, negatively impacting forest ecosystems across the state. As a major source of the region's water supply, it is important to evaluate the vegetation and water balance response of these montane forested watersheds to climate variability across the range of rain-to snow-dominated precipitation regimes. The Standardized Precipitation Index (SPI) and the Standardized Runoff Index (SRI) were used to capture the hydrologic drought signal, and MODIS vegetation indices (i.e., the normalized difference vegetation index and the enhanced vegetation index) were used to evaluate the vegetation and evapotranspiration response in three headwater catchments. The study catchments comprised a low elevation rain-dominated site (Caspar Creek) on the northern California coast, a mid-elevation site with a mix of rain and snow (Providence Creek) in the California Sierra Nevada, and a high elevation snow-dominated site (Bull Creek) in the Sierra Nevada. Lowest SPI values occurred in the third drought year of 2014 for all sites. Lowest SRI was in 2014 for Caspar, but in 2015 for Providence and Bull, reflecting differences in snowpack-delayed runoff and subsurface storage capacity between the lower and higher elevation watersheds. The most accurate water balance closure using evapotranspiration estimates from vegetation indices was within 10% of measured precipitation at snow-dominated Bull. The rain-dominated Caspar watershed had the highest vegetation index values and annual evapotranspiration, with the lowest variability over the previous 13 years (2004-2016). Vegetation index values and annual evapotranspiration decreased with increasing elevation and snow contribution to precipitation. Both snow-influenced Sierra Nevada watersheds showed elevated vegetation and evapotranspiration responses to interannual climate variability. There remains a need for institutional support to expand long-term observations in remote forested mountain watersheds to monitor and research these changing and extreme environmental conditions in source watershed regions.

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Section: Vegetation Indicesmentioning

confidence: 72%

“…SRI is impacted by evapotranspiration that is also modified by changes in temperature and the surface energy balance. The widespread tree mortality that has occurred in the Sierra Nevada with the recent drought [46] would also impact the SRI, but those effects would not be apparent if only using SPI.…”

Section: Climate Indicesmentioning

confidence: 99%

Recent Patterns in Climate, Vegetation, and Forest Water Use in California Montane Watersheds

Saksa

Safeeq

Dymond

2017

Forests

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“…The utility of NDVI for mortality forecasting has been suggested (Huang & Anderegg, ; Vicente‐Serrano et al., ) and is consistent with known relationships between satellite‐based NDVI (or similar indices) and drought, infestations, productivity, leaf senescence and partial dieback, and mortality (Beck, Juday et al., ; Berner et al., ; Breshears et al., ; Bunn et al., ; Foster, Walter, Shugart, Sibold, & Negron, ; Kharuk, Im et al., ; Lloyd et al., ; McDowell et al., ; Meddens & Hicke, ; Spruce et al., ; Vogelmann, Tolk, & Zhu, ). However, to our knowledge these relationships have not yet been documented beyond short‐term (<5 years) associations during severe drought (Byer & Jin, ; Potter, ).…”

Section: Discussionmentioning

confidence: 95%

Detecting early warning signals of tree mortality in boreal North America using multiscale satellite data

Rogers

Solvik

Hogg

et al. 2018

Global Change Biology

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Increasing tree mortality from global change drivers such as drought and biotic infestations is a widespread phenomenon, including in the boreal zone where climate changes and feedbacks to the Earth system are relatively large. Despite the importance for science and management communities, our ability to forecast tree mortality at landscape to continental scales is limited. However, two independent information streams have the potential to inform and improve mortality forecasts: repeat forest inventories and satellite remote sensing. Time series of tree-level growth patterns indicate that productivity declines and related temporal dynamics often precede mortality years to decades before death. Plot-level productivity, in turn, has been related to satellite-based indices such as the Normalized difference vegetation index (NDVI). Here we link these two data sources to show that early warning signals of mortality are evident in several NDVI-based metrics up to 24 years before death. We focus on two repeat forest inventories and three NDVI products across western boreal North America where productivity and mortality dynamics are influenced by periodic drought. These data sources capture a range of forest conditions and spatial resolution to highlight the sensitivity and limitations of our approach. Overall, results indicate potential to use satellite NDVI for early warning signals of mortality. Relationships are broadly consistent across inventories, species, and spatial resolutions, although the utility of coarse-scale imagery in the heterogeneous aspen parkland was limited. Longer-term NDVI data and annually remeasured sites with high mortality levels generate the strongest signals, although we still found robust relationships at sites remeasured at a typical 5 year frequency. The approach and relationships developed here can be used as a basis for improving forest mortality models and monitoring systems.

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“…). Alternatively, in at least some cases, drought‐related mortality may itself reduce stand densities to levels more comparable to historical densities (Potter ).…”

Section: Discussionmentioning

confidence: 99%

“…Removing smaller trees prior to drought may even help to prevent the mortality of larger trees during drought (Thomas & Waring 2015;Van Mantgem et al 2016). Alternatively, in at least some cases, drought-related mortality may itself reduce stand densities to levels more comparable to historical densities (Potter 2016).…”

Section: Discussionmentioning

confidence: 99%

Long‐term climate and competition explain forest mortality patterns under extreme drought

et al. 2016

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Rising temperatures are amplifying drought-induced stress and mortality in forests globally. It remains uncertain, however, whether tree mortality across drought-stricken landscapes will be concentrated in particular climatic and competitive environments. We investigated the effects of long-term average climate [i.e. 35-year mean annual climatic water deficit (CWD)] and competition (i.e. tree basal area) on tree mortality patterns, using extensive aerial mortality surveys conducted throughout the forests of California during a 4-year statewide extreme drought lasting from 2012 to 2015. During this period, tree mortality increased by an order of magnitude, typically from tens to hundreds of dead trees per km , rising dramatically during the fourth year of drought. Mortality rates increased independently with average CWD and with basal area, and they increased disproportionately in areas that were both dry and dense. These results can assist forest managers and policy-makers in identifying the most drought-vulnerable forests across broad geographic areas.

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Landsat Image Analysis of Tree Mortality in the Southern Sierra Nevada Region of California during the 2013-2015 Drought

Cited by 15 publications

References 47 publications

Recent Patterns in Climate, Vegetation, and Forest Water Use in California Montane Watersheds

Recent Patterns in Climate, Vegetation, and Forest Water Use in California Montane Watersheds

Detecting early warning signals of tree mortality in boreal North America using multiscale satellite data

Long‐term climate and competition explain forest mortality patterns under extreme drought

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