Regional equivalent water thickness modeling from remote sensing across a tree cover/lai gradient in mediterranean forests of northern Tunisia

The performance of vegetation indexes derived from moderate resolution imaging spectroradiometer (MODIS) sensors is explored for drought monitoring in the forests of Northern Tunisia; representing a transition zone between the Mediterranean Sea and the Sahara Desert. We investigated the suitability of biomass and moisture vegetation indexes for vegetation water content expressed by the equivalent water thickness (EWT) in a Mediterranean forest ecosystem with contrasted water budgets and desiccation rates. We proposed a revised EWT at canopy level (EWTCAN) based on weekly field measurements of fuel moisture in seven species during the 2010 dry period, considering the mixture of plant functional types for water use (trees, shrubs and herbaceous layers) and a varying vegetation cover. MODIS vegetation indexes computed and smoothed over the dry season were highly correlated with the EWTCAN. The performances of moisture indexes Normalized Difference Infrared Index (NDII6 and NDII7) and Global Moisture Vegetation Index (GVMI6 and GVMI7) were comparable, whereas for biomass vegetation indexes, Normalized Difference Vegetation Index (NDVI), Modified Soil Adjusted Vegetation Index (MSAVI) and Adjusted Normalized Difference Vegetation Index (ANDVI) performed better than Enhanced Vegetation Index (EVI) and Soil Adjusted Vegetation Index (SAVI). We also identified the effect of Leaf Area Index (LAI) on EWTCAN monitoring at the regional scale under the tree cover/LAI gradient of the region from relatively dense to open forest. Statistical analysis revealed a significant decreasing linear relationship; indicating that for LAI less than two, the greater the LAI, the less responsive are the vegetation indexes to changes in EWTCAN; whereas for higher LAI, its influence becomes less significant and was not considered in the inversion models based on vegetation indexes. The EWTCAN time-course from LAI-adapted inversion models based on significantly-related vegetation indexes to EWTCAN showed close profiles resulting from the inversion models using NDVI, ANDVI, MSAVI and NDII6 applied during the dry season. The developed EWTCAN model from MODIS vegetation indexes for the study region was finally tested for its ability to capture the topo-climatic effects on the seasonal and the spatial patterns of desiccation/rewetting for keystone periods of Mediterranean vegetation functioning. Implications for further use in scientific developments or management are discussed

Применение вегетационных индексов для оценки состояния сельскохозяйственных культур

Monitoring of the state of agricultural crops and forecasting the crops development begin with aerial photography using a unmanned aerial vehicles and a multispectral camera. Vegetation indexes are selected empirically and calculated as a result of operations with values of diff erent spectral wavelengths. When assessing the state of crops, especially in breeding, it is necessary to determine the limiting factors for the use of vegetation indexes.(Research purpose) To analyze, evaluate and select vegetation indexes for conducting operational, high-quality and comprehensive monitoring of the state of crops and the formation of optimal management decisions.(Materials and Methods) The authors studied the results of scientifi c research in the fi eld of remote sensing technology using unmanned aerial vehicles and multispectral cameras, as well as the experience of using vegetation indexes to assess the condition of crops in the precision farming system. The limiting factors for the vegetation indexes research were determined: a limited number of monochrome cameras in popular multispectral cameras; key indicators for monitoring crops required by agronomists. After processing aerial photographs from an unmanned aerial vehicle, a high-precision orthophotomap, a digital fi eld model, and maps of vegetation indexes were created.(Results and discussion) More than 150 vegetation indexes were found. Not all of them were created through observation and experimentation. The authors considered broadband vegetation indexes to assess the status of crops in the fi elds. They analyzed the vegetation indexes of soybean and winter wheat crops in the main phases of vegetation.(Conclusions) The authors found that each vegetative index had its own specifi c scope, limiting factors and was used both separately and in combination with other indexes. When calculating the vegetation indexes for practical use, it was recommended to be guided by the technical characteristics of multispectral cameras and took into account the index use eff ectiveness at various vegetation stages.Аэрофотосъемку с помощью беспилотных летательных аппаратов и мультиспектральной камеры применяют для мониторинга состояния посевов и прогноза развития сельскохозяйственных культур. В результате операций со значениями различных спектральных длин волн эмпирически подбирают и рассчитывают вегетационные индексы, составляя карты. При оценке состояния посевов необходимо определять лимитирующие факторы применения вегетационных индексов.(Цель исследования) Проанализировать, оценить и выбрать вегетационные индексы для проведения оперативного, качественного и комплексного мониторинга состояния сельскохозяйственных культур и формирования оптимальных управленческих решений.(Материалы и методы) Изучили результаты научных исследований в области технологий дистанционного зондирования с использованием беспилотных летательных аппаратов и мультиспектральных камер, а также опыт применения вегетационных индексов для оценки состояния сельскохозяйственных культур в системе точного земледелия. Определили лимитирующие факторы для исследования вегетационных индексов: ограниченное количество монохромных камер в популярных мультиспектральных камерах; основные показатели для мониторинга сельскохозяйственных культур, необходимые агрономам. После обработки аэрофотоснимков с беспилотного летательного аппарата создали высокоточный ортофотоплан, цифровую модель поля и карты вегетационных индексов.(Результаты и обсуждение) Обнаружили более 150 вегетационных индексов. Не все их них создавались путем наблюдений и экспериментов. Рассмотрели широкополосные вегетационные индексы для оценки состояния посевов на полях. Проанализировали вегетационные индексы посевов сои и озимой пшеницы в основных фазах вегетации.(Выводы) Выявили, что каждый вегетационный индекс имеет свою специфическую сферу применения, ограничивающие факторы и используется как отдельно, так и в комплексе с другими индексами. Рекомендовали при расчете вегетационных индексов для практического применения руководствоваться техническими характеристиками мультиспектральных камер и учитывать эффективность применения индекса на различных стадиях вегетации

Gross primary production using related vegetation indices.

Site description; Micrometeorological and flux measurements; Hyperspectral reflectance measurements; Vegetation indexes

Estimating foliar nitrogen in Eucalyptus using vegetation indexes

Nitrogen (N) has commonly been applied in Eucalyptus stands in Brazil and it has a direct relation with biomass production and chlorophyll content. Foliar N concentrations are used to diagnose soil and plant fertility levels and to develop N fertilizer application rates. Normally, foliar N is obtained using destructive methods, but indirect analyses using Vegetation Indexes (VIs) may be possible. The aim of this work was to evaluate VIs to estimate foliar N concentration in three Eucalyptus clones. Lower crown leaves of three clonal Eucalyptus plantations (25 months old) were classified into five color patterns using the Munsell Plant Tissue Color Chart. For each color, N concentration was determined by the Kjeldahl method and foliar reflectance was measured using a CI-710 Miniature Leaf Spectrometer. Foliar reflectance data were used to obtain the VIs and the VIs were used to estimate N concentrations. In the visible region, the relationship between N concentration and reflectance percentage was negative. The highest correlations between VIs and N concentrations were obtained by the Inflection Point Position (IPP, r = 0.97), Normalized Difference Red-Edge (reNDVI, r = 0.97) and Modified Red-Edge Normalized Difference Vegetation Index (mNDI, r = 0.97). Vegetation indexes on the red edge region provided the most accurate estimates of foliar N concentration. The reNDVI index provided the best N concentration estimates in leaves of different colors of Eucalyptus urophylla × grandis and Eucalyptus urophylla × urophylla (R2 = 0.97 and RMSE = 0.91 g kg−1)

Analyse saisonniers de la vegetation de cerrado par données du capteur MODIS dans le District Fédéral (Brésil)

O presente estudo visa caracterizar o comportamento sazonal da vegetação do Cerrado por meio de índices de vegetação (NDVI e EVI) do sensor MODIS. A caracterização da sazonalidade foi realizada em áreas com e sem registro de queimadas. Para construção das séries temporais foi utilizado o produto MOD13Q1. As imagens datam do período de 2000 a 2015, com um período de amostragem a cada 16 dias. As transformações de Fourier de séries temporais mostram que os índices de vegetação do Cerrado são amplamente dominados pelo ciclo anual. O comportamento dos índices de vegetação estabelecida para o período 2000-2015 é fortemente controlado pela precipitação estabelecida em relação ao mesmo período. Em alguns anos, os índices de vegetação mostram uma dinâmica mais propagada durante a estação chuvosa (aumento prematuro e amplitude menor do que a amplitude média de climatologia), ou ao contrário, uma atividade mais tardia e mais ampla. Os diagramas de dispersões entre os índices de vegetação obtidos para os locais sem fogo contra os locais queimados, mostram uma separação de dados em três grupos distintos: os índices de vegetação da estação das chuvas, os da estação seca, e, finalmente, os índices que comportam uma assinatura relacionada com o fogo.This study aims to characterize the seasonal behavior of Cerrado vegetation through vegetation indexes (NDVI and EVI) of the MODIS sensor. The characterization of seasonality was carried out in areas with and without recorded fires. NDVI and EVI vegetation indexes from the MOD13Q1 product were used to build time series. The images date from 2000 to 2015, with a 16-day sampling period. Fourier transformations of time series show that the Cerrado vegetation indexes are largely dominated by the annual cycle. The monthly climatology of vegetation indexes established for the period 2000-2015 is strongly controlled by the rainfall monthly climatology established over the same period. In some years the vegetation indexes show a more dynamic spread during the rainy season (a premature increase and lower amplitude than the average amplitude of climatology), or on the contrary a later and more extensive activity. Dispersion diagrams between vegetation indexes obtained for sites without fire versus the burned sites show a separation of data into three distinct groups: the vegetation indexes of the rainy season, those in the dry season, and finally the indexes with a fire-related signature.Cette étude vise à caractériser le comportement saisonnier de la végétation du Cerrado par indice de végétation (NDVI et EVI) du capteur MODIS. La caractérisation de la saisonnalité a été réalisée dans les zones avec et sans registre de brûlées. Pour la construction de la série de temporelle, nous avons utilisé le MOD13Q1. Les images datent de 2000 à 2015, avec une période d’échantillonnage tous les 16 jours. La série chronologique des transformations de Fourier montrent que les indices de végétation du Cerrado sont largement dominés par le cycle annuel. Le comportement des indices de végétations établies pour la période 2000-2015 est fortement contrôlé par la précipitation sur la même période. En quelques années, les indices de végétation montrent une propagation plus dynamique pendant la saison des pluies (début prématuré et une amplitude inférieure à l’amplitude moyenne de la climatologie), ou plutôt une activité plus en retard et plus large. Les diagrammes de dispersion entre les indices de végétation obtenus pour les sites sans feu contre les sites brûlés, montrent une séparation des données en trois groupes distincts : les indices de végétation de la saison des pluies, saison sèche, et enfin les indices qui contiennent une signature liée à l’incendie

Assessment of the vegetation cover in a burned area 22-years ago using remote sensing techniques and GIS analysis (Sierra de las Nieves, South of Spain).

The study aim was to characterize the vegetation cover in a burned area 22-years ago considering the previous situation to wildfire in 1991 and the current one in 2013. The objectives were to: (i) compare the current and previous vegetation cover to widlfire; (ii) evaluate whether the current vegetation has recovered the previous cover to wildfire; and (iii) determine the spatial variability of vegetation recovery after 22-years since the wildfire. The study area is located in Sierra de las Nieves, South of Spain. It corresponds to an area affected by a wildfire in August 8th, 1991. The burned area was equal to 8156 ha. The burn severity was spatially very high. The main geographic features of the burned area are: mountainous topography (altitudes ranging from 250 m to 1500 m; slope gradient >25Remote sensing techniques and GIS analysis has been applied to achieve the objectives. Landsat 5 and Landsat 8 images were used: July 13th, 1991 and July 1st, 2013, for the previous wildfire situation and 22-years after, respectively. The 1990 CORINE land cover was also considered to map 1991 land uses prior the wildfire. Likewise, the Andalucía Regional Government wildfire historic records were used to select the burned area and its geographical limit. 1991 and 2013 land cover map were obtained by means of object-oriented classifications. Also, NDVI and PVI1 vegetation indexes were calculated and mapped for both years. Finally, some images transformations and kernel density images were applied to determine the most recovered areas and to map the spatial concentration of bare soil and pine cover areas in 1991 and 2013, respectively. According to the results, the combination of remote sensing and GIS analysis let map the most recovered areas affected by the wildfire in 1991. The vegetation indexes indicated that the vegetation cover in 2013 was still lower than that mapped just before the 1991 widlfire in most of the burned area after 22-years. This result was also confirmed by other techniques applied. Finally, the kernel density surface let identify and locate the most recovered areas of pine cover as well as those areas that still remain totally or partially uncovered (bare soil.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Mediterranean silvoarable systems for feed and fuel: the AGROFORCES project (Agroforestry for carbon sequestration and ecosystem services)

N/

AgRISTARS: Early warning and crop condition assessment. Plant cover, soil temperature, freeze, water stress, and evapotranspiration conditions

Emissive (10.5 to 12.5 microns) and reflective (0.55 to 1.1 microns) data for ten day scenes and infrared data for six night scenes of southern Texas were analyzed for plant cover, soil temperature, freeze, water stress, and evapotranspiration. Heat capacity mapping mission radiometric temperatures were: within 2 C of dewpoint temperatures, significantly correlated with variables important in evapotranspiration, and related to freeze severity and planting depth soil temperatures

Estimation of Carbon Stock Stands Using EVI and NDVI Vegetation Index in Production Forest of Lembah Seulawah Sub-District, Aceh Indonesia

This study aims to determine the distribution of the vegetation indexes to estimate the carbon stocks of forest stands in the Production Forest of Lembah Seulawah sub-district. Aceh Province, Indonesia. A non-destructive method using allometric equations and landscape scale method were applied, where in carbon stocks at the points of samples are correlated with the index values of each transformation of the vegetation indexes; EVI and NDVI. Results show that EVI values of study area from 0.05 to 0.90 and NDVI values from 0.17 to 0.85. The regression analysis between EVI with carbon stock value of sample locations equation is Y = 151.7X-39.76. with the coefficient of determination (R2) is 0.83. From this calculation, the total carbon stocks in the Production Forest area of Lembah Seulawah sub-district using EVI is estimated 790.344.41 tonnes, and the average value of carbon stocks in average is 51.48 tons per hectare. Regression analysis between NDVI values at the research locations for the carbon stack measured samples is Y = 204.Xx-102.1 with coefficient of determination (R2) is 0.728. Total carbon stocks in production forest of Lembah Seulawah sub-district using NDVI is estimated 711.061.81 tones. and the average value of carbon stocks is 46.32 tons per hectare. From the above results it can be concluded that the vegetation indexes: EVI and NDVI are vegetation indexed that have a very close correlation with carbon stocks stands estimation. The correlation between EVI with carbon stock and the correlation between NDVI with carbon stock is not significantly differen