Evaluating drought response of Southern Cape Indigenous Forests, South Africa, using MODIS data

Hope, Allen; Fouad, Geoffrey; Granovskaya, Yelena

doi:10.1080/01431161.2014.930205

Cited by 11 publications

(11 citation statements)

References 19 publications

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“…NDMI differs from the more widely used NDVI in its reliance on the MIR band, for which absorbance is primarily determined by vegetation water content [60]. Other remotely-sensed vegetation indices have also been used to monitor drought effects in forests, including NDVI, TCT, and the Enhanced Vegetation Index (EVI) [49,61,62]. Among these indices, however, NDMI had the strongest relationship to field measurements of leaf-area index and canopy-gap fraction in a semi-arid forest [51], two forest metrics that are responsive to drought-induced physiological stress and mortality.…”

Section: Landsat Imagesmentioning

confidence: 99%

“…Refugia were conceptualized as locations within each forest type for which forest responses to drought and MPB infestation were substantially less than for the surrounding landscape. Forest responses to these disturbances were quantified using anomalies from the reference period 1985-2000, following similar approaches in previous studies [49,62]. For the drought years 2001 and 2009, anomalies were calculated as:…”

Section: Identification Of Refugiamentioning

confidence: 99%

“…Forest responses to drought even in the absence of insect infestation may vary by stand composition. A common approach is to normalize anomalies by dividing by reference (baseline) standard deviation [62] to enable analysis of anomaly values across spatial gradients, including across different vegetation types. In this study, however, use of absolute (not normalized) anomalies enabled explicit comparisons between different forest types, such as between MPB host versus non-host forest types.…”

Section: Identification Of Refugiamentioning

confidence: 99%

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Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest

Cartwright

2018

Forests

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Droughts and insect outbreaks are primary disturbance processes linking climate change to tree mortality in western North America. Refugia from these disturbances—locations where impacts are less severe relative to the surrounding landscape—may be priorities for conservation, restoration, and monitoring. In this study, hypotheses concerning physical and biological processes supporting refugia were investigated by modelling the landscape controls on disturbance refugia that were identified using remotely sensed vegetation indicators. Refugia were identified at 30-m resolution using anomalies of Landsat-derived Normalized Difference Moisture Index in lodgepole and whitebark pine forests in southern Oregon, USA, in 2001 (a single-year drought with no insect outbreak) and 2009 (during a multi-year drought and severe outbreak of mountain pine beetle). Landscape controls on refugia (topographic, soil, and forest characteristics) were modeled using boosted regression trees. Landscape characteristics better explained and predicted refugia locations in 2009, when forest impacts were greater, than in 2001. Refugia in lodgepole and whitebark pine forests were generally associated with topographically shaded slopes, convergent environments such as valleys, areas of relatively low soil bulk density, and in thinner forest stands. In whitebark pine forest, refugia were associated with riparian areas along headwater streams. Spatial patterns in evapotranspiration, snowmelt dynamics, soil water storage, and drought-tolerance and insect-resistance abilities may help create refugia from drought and mountain pine beetle. Identification of the landscape characteristics supporting refugia can help forest managers target conservation resources in an era of climate-change exacerbation of droughts and insect outbreaks.

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Section: Landsat Imagesmentioning

confidence: 99%

Section: Identification Of Refugiamentioning

confidence: 99%

Section: Identification Of Refugiamentioning

confidence: 99%

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Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest

Cartwright

2018

Forests

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“…We conducted this study in select Southern Mistbelt Forests within the provinces of KZN (28.5˚S, 30.9˚E) (Kokstad and Creighton) and the Eastern Cape (32.3˚S, 26.4˚E) (Nqadu, Mhlahlane and eLangeni forests), South Africa (Figure 1). Eastern Mistbelt forests are naturally fragmented and patchily distributed as a result of biogeography and paleoclimate (Moll and White 1978) and form part of the Southern Mistbelt Forest group which occurs from the Eastern Cape to KZN (Hope et al 2014). The Mistbelt forms an irregular band through the KZN Midlands, extending from Weza in the south-west to Ngome in the north-east (Mucina et al 2006a,b, Wilson et al 2017.…”

Section: Study Areamentioning

confidence: 99%

Occupancy of two forest specialist birds in the Southern Mistbelt Forests of KwaZulu-Natal and Eastern Cape, South Africa

Gumede

Smith

et al. 2020

Bird Conservation International

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Summary Establishing the specific habitat requirements of forest specialists in fragmented natural habitats is vital for their conservation. We used camera-trap surveys and microhabitat-scale covariates to assess the habitat requirements, probability of occupancy and detection of two terrestrial forest specialist species, the Orange Ground-thrush Geokichla gurneyi and the Lemon Dove Aplopelia larvata during the breeding and non-breeding seasons of 2018–2019 in selected Southern Mistbelt Forests of KwaZulu-Natal and the Eastern Cape, South Africa. A series of camera-trap surveys over 21 days were conducted in conjunction with surveys of microhabitat structural covariates. During the wet season, percentage of leaf litter cover, short grass cover, short herb cover, tall herb cover and saplings 0–2 m, stem density of trees 6–10 m and trees 16–20 m were significant structural covariates for influencing Lemon Dove occupancy. In the dry season, stem density of 2–5 m and 10–15 m trees, percentage tall herb cover, short herb cover and 0–2 m saplings were significant covariates influencing Lemon Dove occupancy. Stem density of trees 2–5 m and 11–15 m, percentage of short grass cover and short herb cover were important site covariates influencing Orange Ground-thrush occupancy in the wet season. Our study highlighted the importance of a diverse habitat structure for both forest species. A high density of tall/mature trees was an essential microhabitat covariate, particularly for sufficient cover and food for these ground-dwelling birds. Avian forest specialists play a vital role in providing ecosystem services perpetuating forest habitat functioning. Conservation of the natural heterogeneity of their habitat is integral to management plans to prevent the decline of such species.

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“…Multispectral sensors have spectral bands from the visible and infrared wavelengths that can be combined into vegetation indexes [29,30]. Several vegetation indexes (VI) have been used in disturbance and drought studies [10,31,32], many of which utilize the NIR and red bands. The normalized difference vegetation index (NDVI) is the most widely used vegetation index to document and monitor drought and related impacts in forests [26,33,34].…”

Section: Introductionmentioning

confidence: 99%

Spatial Upscaling of Tree-Ring-Based Forest Response to Drought with Satellite Data

Fang

Zhou

et al. 2019

Remote Sensing

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We have integrated the observational capability of satellite remote sensing with plot-scale tree-ring data to upscale the evaluation of forest responses to drought. Satellite data, such as the normalized difference vegetation index (NDVI), can provide a spatially continuous measure with limited temporal coverage, while tree-ring width index (RWI) provides an accurate assessment with a much longer time series at local scales. Here, we explored the relationship between RWI and NDVI of three dominant species in the Southwestern United States (SWUS) and predicted RWI spatial distribution from 2001 to 2017 based on Moderate Resolution Imaging Spectroradiometer (MODIS) 1-km resolution NDVI data with stringent quality control. We detected the optimum time windows (around June–August) during which the RWI and NDVI were most closely correlated for each species, when the canopy growth had the greatest effect on growth of tree trunks. Then, using our upscaling algorithm of NDVI-based RWI, we were able to detect the significant impact of droughts in 2002 and in 2011–2014, which supported the validity of this algorithm in quantifying forest response to drought on a large scale.

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Evaluating drought response of Southern Cape Indigenous Forests, South Africa, using MODIS data

Cited by 11 publications

References 19 publications

Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest

Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest

Occupancy of two forest specialist birds in the Southern Mistbelt Forests of KwaZulu-Natal and Eastern Cape, South Africa

Spatial Upscaling of Tree-Ring-Based Forest Response to Drought with Satellite Data

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