Mapping land cover and forest density in Zagros forests of Khuzestan province in Iran: A study based on Sentinel-2, Google Earth and field data

Zagros forests in western Iran have widely been destroyed because of various reasons. This study was performed to provide the land cover and forest density maps in Zagros forests of Khuzestan province using Sentinel-2, Google Earth and field data. The forest boundary in Khuzestan province was digitized in Google Earth. Sentinel-2 satellite images were provided for the study area. One 1:25000 index sheet of Iranian Mapping Organization (IMO) was selected as pilot area in the province. Sentinel-2 image of the pilot area was classified using different supervised classification algorithms to select the best algorithm for land cover mapping in Khuzestan province. In addition, to evaluate the accuracy of Google Earth data, field sampling was performed using random plots in different land covers. Field data of forest plots were applied to investigate tree canopy cover percent (forest density), as well. Classification of Sentinel-2 image in Zagros area of Khuzestan province was done using the best algorithm and the land cover was obtained. The forest density map was also obtained using a linear regression model between tree canopy cover percent (obtained from field plots) and normalized difference vegetation index (NDVI) (obtained from NDVI map). Finally, the accuracy of land cover map was assessed by some square plots on Google Earth. Results demonstrated that support vector machine (SVM) algorithm had the highest accuracy for land cover mapping. Results also showed that Google Earth images had a good accuracy in the Zagros forests of Khuzestan province. Results demonstrated that NDVI has been a good predicator to estimate tree canopy cover in the study area. Based on results, an area of 443,091.22 ha is covered by Zagros forests in Khuzestan province. Results of accuracy assessment of the land cover map showed the good accuracy of this map in Khuzestan province (overall accuracy: 91% and kappa index: 0.83). For optimum management of Zagros forests, it is suggested that the land cover and forest density mapping will be performed using SVM algorithm, NDVI, and Sentinel-2 satellite images in Zagros forests of Khuzestan province in the certain periods.     

Mono-temporal and multi-temporal approaches for burnt area detection using Sentinel-2 satellite imagery (a case study of Rokan Hilir Regency,Indonesia)

Accurate and up-to-date information about the burnt area is important in estimating environmental losses, prioritizing rehabilitation areas, and determining future planning strategies. The publicly available medium resolution optical Sentinel-2 satellite data provides a practical and effective solution for burnt area detection. In this study, we proposed two different approaches using mono-temporal and multi-temporal Sentinel-2 satellite imagery to detect burnt areas in Rokan Hilir Regency, Indonesia. The multi-temporal approaches utilized two different ensemble machine learning algorithms (Random Forest and XGBoost) and used six composite spectral indices of the differenced Normalized Burn Ratio (dNBR), differenced Normalized Burn Ratio 2 (dNBR2), differenced Normalized Difference Vegetation Index (dNDVI), differenced Soil Adjusted Vegetation Index (dSAVI), differenced Char Soil Index (dCSI), differenced Burnt area Index for Sentinel-2 (dBAIS2), and differenced Mid-infrared Burn Index (dMIRBI) as model inputs. The burnt areas are labeled by combining hotspots with confidence intervals above 95%, fire spots, and change detection methods. The XGBoost model achieved the best performance with an F1 score of 0.97 and an accuracy of 96%. Furthermore, we use the SHapley Additive exPlanations (SHAP) to quantify the contribution of each feature as well as its correlation with the target class. The dNBR, dMIRBI, and dNBR2 indices contribute the most to the XGBoost model. In comparison, this study also investigates and compares a mono-temporal approach with One-dimensional Convolutional Neural Network (CNN-1D) architecture and the performance obtained is slightly better than both machine learning models. Overall, both mono-temporal and multi-temporal approaches satisfactorily detect the burnt area.     

Satellite observation to assess dengue risk due to Aedes aegypti and Aedes albopictus in a subtropical city of Argentina

Earth observation environmental features measured through remote sensing and models of vector mosquitoes species Aedes aegypti and Ae. albopictus provide an advancement with regards to dengue risk in urban environments of subtropical areas of Argentina. The authors aim to estimate the effect of landscape coverage and spectral indices (Normalized Difference Vegetation Index [NDVI], Normalized Difference Water Index [NDWI] and Normalized Difference Built-up Index [NDBI]) on the larvae abundance of Ae. aegypti and Ae. albopictus in Eldorado, Misiones, Argentina using remote satellite sensors. Larvae of these species were collected monthly (June 2016 to April 2018), in four environments: tire repair shops, cemeteries, dwellings and an urban natural park. The proportion of landscape coverage (water, urban areas, bare soil, low vegetation and high vegetation) was determined from the supervised classification of Sentinel-2 images and spectral indices, calculated. The authors developed spatial models of both vector species by generalized linear mixed models. The model's results showed that Ae. aegypti larvae abundance was better modelled by NDVI minimum values, NDBI maximum values and the interaction between them. For Ae. albopictus proportion of bare soil, low vegetation and the interaction between both variables explained better the abundance.     

Activity-density of <Emphasis Type="Italic">Pardosa cribata</Emphasis> in Spanish citrus orchards and its predatory capacity on <Emphasis Type="Italic">Ceratitis capitata</Emphasis> and <Emphasis Type="Italic">Myzus persicae</Emphasis>

The wolf spider Pardosa cribata Simon is the most abundant ground-dwelling spider inhabiting citrus orchards in eastern Spain. However, little is known about its activity-density and its predatory role in the citrus agrosystem. Here we report on the activity-density of P. cribata monitored by pitfall traps, and on its capacity to prey on two citrus pests that appear both in the citrus canopy and the ground cover, Ceratitis capitata (Wiedemman) and Myzus persicae (Sulzer), respectively. Pardosa cribata was present in citrus orchards throughout the year, with a peak in spring and a higher peak in summer. Pardosa cribata preyed on adults and third-instar larvae but not on pupae of C. capitata. A type II functional response was obtained for teneral-like adults, with an estimated attack rate (a′) of 0.771 ± 0.213 days⁻¹ and a handling time (T _h) of 0.051 ± 0.013 days. Pardosa cribata also preyed efficiently on M. persicae, giving a type II functional response with an estimated attack rate and handling time of 2.833 ± 0.578 days⁻¹ and 0.031 ± 0.001 days, respectively. The data reported here indicate that this wolf spider could play an important role in regulating both these pests, and therefore might contribute to developing conservation biological control strategies for citrus pests. Handling Editor: Arne Jenssen.     

Abundance,interannual variation and potential pest predator role of two co‐occurring earwig species in citrus canopies

Earwigs are usually considered pest predators in orchards. Because of its worldwide distribution, most research on earwigs focuses on the European earwig Forficula auricularia Linnaeus (Insecta: Dermaptera: Forficulidae). However, very little is known of this species in Mediterranean citrus orchards. Earwigs and aphids were collected monthly during 5 years (2006–2010) from citrus canopies. Two species of earwigs were found: F. auricularia and Forficula pubescens Gené (=Guanchia pubescens), with the latter seldom cited in the literature. The goals of this study were (i) to document the abundance of these two earwig species in Mediterranean citrus canopies; (ii) to determine whether they are positively or negatively associated with each other, or randomly distributed; (iii) to measure the interannual variation of the abundance of both species during a 5‐year period and (iv) to evaluate the potential role of earwigs as pest predators in citrus canopies. As compared to colder regions, F. auricularia active period in citrus canopies in our study site lasted longer. Both species co‐occurred randomly in canopies. In 2006, both species showed approximately the same abundance, but in 2010, F. pubescens abundance in canopies was 28 times greater than that of F. auricularia. The potential role of earwigs as pest predators is higher in the Mediterranean than in other colder regions, because of the longer active period. F. auricularia is a sedentary generalist predator, already present in citrus canopies at the onset of most pest outbreaks, while F. pubescens arrived later to the canopies, but most likely was abundant enough to contribute in the control of citrus pests.     

Influence of ground beetles (Carabidae) as biological agent to control of the Mediterranean fruit fly pupae,Ceratitis capitata,in Iranian citrus orchards

Damage by Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in the northern Iranian citrus orchards has been led to spray by different chemical pesticides. The present study was conducted in the citrus orchard in Mazandaran province of Iran where with the exception of mineral oil treatments for scale insects, had not been sprayed with synthetic insecticides for six years. The purpose of this study was initially to investigate faun and seasonal activity of predaceous ground carabid beetles in the citrus orchards. Additionally, their role as predators of Ceratitis capitata (Wiedemann) pupae was evaluated under laboratory and field conditions. Predation in laboratory was evaluated by no choice feeding experiments while predation under field conditions was evaluated by molecular detection of the pest DNA in the gut contents of field-collected Carabids. A total of 3437 beetles of ten carabid species were collected from a non-chemical treatment citrus orchard. The results of the seasonal density fluctuation indicated increasing population in spring reaching the highest in September, simultaneously with the peak of fruit fly damage, and thereafter decreasing during winter when the pest was overwintering. However, three species, Harpalus rufipes, Broscus karelinii and Brachinus brevicollis were most abundant in the field collection but the results of no-choice experiments in the laboratory indicated H. rufipes, B. karelinii and Pterostichus macer were the most voracious predators on pupae. Results of gut content analysis of the voracious species indicated the positive testing for pest DNA in 79.16 % of H. rufipes, 76.92 % of B. karelinii and 75 % of P. macer of analyzed beetles. The results of the study strongly indicated that in citrus orchards where intensive spraying is eliminated, natural enemies such as Carabid beetles could play an important role in reducing pests such as medfly.     

Mapping paddy rice areas based on vegetation phenology and surface moisture conditions

Accurate and timely rice mapping is important for food security and environmental sustainability. We developed a novel approach for rice mapping through Combined Consideration of Vegetation phenology and Surface water variations (CCVS). Variation of the Land Surface Water Index (LSWI) in rice fields was relatively smaller than that in other crops fields during the period from tillering to heading dates. Therefore, the ratios of change amplitude of LSWI to 2-band Enhanced Vegetation Index 2 (EVI2) during that period were utilized as the primary metric for paddy rice mapping. This algorithm was applied to map paddy rice fields in southern China using an 8-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) in 2013. The resultant rice cropping map was consistent with the agricultural census data (r² = 0.8258) and ground truth observations (overall accuracy = 93.4%). Validation with Landsat Thematic Mapper images in test regions also revealed its high accuracy (with overall accuracy of 94.3% and kappa coefficient of 0.86). The proposed CCVS method was more robust to intra-class variability and other related uncertainties compared with other related methods in rice mapping. Its successful application in southern China revealed its efficiency and great potential for further utilization.     

Detecting changes in forest floor habitat after canopy disturbance

A massive ice storm hit northeastern North America in 1998, dropping more than 100 mm of freezing rain at its epicenter in southern Quebec, Canada. There has been extensive study of which trees and areas received the most damage, but the biodiversity consequences of this damage at landscape scales have not received much attention. We assessed the effectiveness of seven remotely sensed vegetation indices—Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index, Difference Vegetation Index, Renormalized Difference Vegetation Index, Atmospherically Resistant Vegetation Index, Green Normalized Difference Vegetation Index and Visible Atmospheric Resistant Index—for modeling the coarse woody debris (CWD) influx in an old growth forest reserve at the storm’s epicenter; NDVI was the best predictor of CWD influx. We categorized the geospatial CWD predictions from the NDVI-derived model to map the spatial distribution of sun-exposed, moist-shaded, dry-shaded and wet CWD microhabitats on the forest floor. Moist-shaded, dry-shaded and wet patches of CWD were large and well connected, but sun-exposed patches were small and sparse. Since these microhabitats affect the distribution and abundance of saproxylic insects, wood-rotting fungi, salamanders, birds, small burrowing mammals and plant species dependent on nurse-logs for establishment, the CWD influx from the 1998 ice storm may have revitalized local populations of these taxa through increased habitat availability as well as increased dispersal within the reserve.     

The effects of farming system,habitat type and bait type on the isolation of entomopathogenic fungi from citrus soils in the Eastern Cape Province,South Africa

A survey of occurrence of entomopathogenic fungi was undertaken on soils from citrus orchards and refugia on conventionally and organically managed farms in the Eastern Cape Province in South Africa. An adapted method for baiting soil samples with key citrus pest Thaumatotibia leucotreta (Meyrick; Lepidoptera: Tortricidae) and Ceratitis capitata (Wiedemann; Diptera: Tephritidae) larvae, as well as with the standard bait insect, Galleria mellonella (Linnaeus; Lepidoptera: Pyralidae), was implemented. Sixty-two potentially useful entomopathogenic fungal isolates belonging to four genera were collected from 288 soil samples, an occurrence frequency of 21.53%. The most frequently isolated entomopathogenic fungal species was Beauveria bassiana (Balsamo) Vuillemin (15.63%), followed by Metarhizium anisopliae var. anisopliae (Metschnikoff) Sorokin (3.82%). Galleria mellonella was the most effective bait insect used to isolate fungal species (χ ² = 40.13, df = 2, P ≤ 0.005), with a total of 45 isolates obtained, followed by C. capitata with 11 isolates, and T. leucotreta with six isolates recovered. There was a significantly (χ ² = 11.65, df = 1, P ≤ 0.005) higher occurrence of entomopathogenic fungi in soil samples taken from refugia compared to cultivated orchards of both organically and conventionally managed farms. No significant differences were observed in the recovery of fungal isolates when soil samples from both farming systems were compared.     

Vegetation expansion in the subnival Hindu Kush Himalaya

The mountain systems of the Hindu Kush Himalaya (HKH) are changing rapidly due to climatic change, but an overlooked component is the subnival ecosystem (between the treeline and snow line), characterized by short‐stature plants and seasonal snow. Basic information about subnival vegetation distribution and rates of ecosystem change are not known, yet such information is needed to understand relationships between subnival ecology and water/carbon cycles. We show that HKH subnival ecosystems cover five to 15 times the area of permanent glaciers and snow, highlighting their eco‐hydrological importance. Using satellite data from the Landsat 5, 7 and 8 missions, we measured change in the spatial extent of subnival vegetation from 1993 to 2018. The Landsat surface reflectance‐derived Normalized Difference Vegetation Index product was thresholded at 0.1 to indicate the presence/absence of vegetation. Using this product, the strength and direction of time‐series trends in the green pixel fraction were measured within three regions of interest. We controlled for cloud cover, snow cover and evaluated the impact of sensor radiometric differences between Landsat 7 and Landsat 8. Using Google Earth Engine to expedite data processing tasks, we show that there has been a weakly positive increase in the extent of subnival vegetation since 1993. Strongest and most significant trends were found in the height region of 5,000–5,500 m a.s.l. across the HKH extent: R² = .302, Kendall's τ = 0.424, p < .05, but this varied regionally, with height, and according to the sensors included in the time series. Positive trends at lower elevations occurred on steeper slopes whilst at higher elevations, flatter areas exhibited stronger trends. We validated our findings using online photographs. Subnival ecological changes have likely impacted HKH carbon and water cycles with impacts on millions of people living downstream, but the strength and direction of impacts of vegetation expansion remain unknown.     

Potential vectors of Xylella fastidiosa: a study of leafhoppers and treehoppers in citrus agroecosystems affected by Citrus Variegated Chlorosis

This study investigated the predominant leafhopper and treehopper (Hemiptera, Auchenorrhyncha) species in Citrus Variegated Chlorosis (CVC)‐affected citrus agroecosystems in Argentina, their seasonal fluctuation, and their potential role as vectors of Xylella fastidiosa Wells et al., using molecular methods for detection. More than 6 000 Auchenorrhyncha were collected from three citrus agroecosystems over a period of 3 years using yellow sticky traps and entomological nets. Cicadellidae and Membracidae were the most abundant families. Of the 43 species identified, five were predominant in citrus orchards, and three were predominant in weeds surrounding citrus plants. All predominant species and another four non‐predominant species tested positive for X. fastidiosa in PCR and real‐time PCR assays. In a transmission assay, Dechacona missionum (Berg), Tapajosa rubromarginata (Signoret), and Cyphonia clavigera (Fabricius) transmitted X. fastidiosa successfully. Scaphytopius bolivianus Oman and Frequenamia spiniventris (Linnavuori) populations increased once (during the summer), possibly due to favorable weather conditions, and Bucephalogonia xanthophis (Berg), Molomea lineiceps Young, and T. rubromarginata populations increased twice a year: once in summer and once in winter, coinciding with the increase in early citrus shoots (flush). Among the X. fastidiosa‐positive species, those with the higher population densities during the sprouting period, where trees are highly susceptible to infection, must be considered as most relevant vectors of CVC in the citrus‐growing areas in Argentina.     

Integrating chemical control with sterile insect releases in an integrated pest management programme for Thaumatotibia leucotreta

False codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is an important indigenous pest of citrus in southern Africa. Successful control is dependent upon integration of area‐wide sterile insect releases and other suppression methods. The aim of this work was to test pyrethroid and organophosphate‐based insecticides (tau‐fluvalinate and chlorpyrifos) for their residual effect on mortality of released irradiated T. leucotreta male moths. Both of these insecticides were effective in killing irradiated T. leucotreta for 7 days after application on leaves, after which degradation of the active ingredient resulted in a marked reduction in efficacy after 14 days and rendering them harmless. Mortality was found to be similar for irradiated and non‐irradiated male T. leucotreta after treatment. Consequently, even though these insecticides might have an effect on moths in the field, ratios of sterile:wild moths should not be altered. Supporting field data from six sites in the Sundays River Valley over a season of sterile insect releases showed the conventional chemical crop protection programme to be as effective as an integrated pest management programme in facilitating effective control of T. leucotreta through sterile insect releases. The study also confirmed that the ratios of sterile:wild male moths in the commercial citrus orchards were not affected by the application of insecticides. These findings confirm the high potential of sterile insect releases for control of T. leucotreta in citrus.     

Evaluation of mating disruption for control of lightbrown apple moth (Lepidoptera: Tortricidae) in citrus

Three large-scale mating disruption (MD) trials were conducted from 2001 to 2004 in an organic citrus orchard in inland southeastern Australia to evaluate the effectiveness of the MD dispenser Isomate LBAM Plus in controlling lightbrown apple moth, Epiphyas postvittana (Walker), in citrus. At the application rate of 364-728 dispensers per ha, the dispensers reduced pheromone trapping of E. postvittana to almost undetectable levels for approximately 6 mo in the treated area. During this period, most sentinel females in the treated area failed to mate. Infestation by E. postvittana in the treated area was reduced by >50%. If distributed in citrus orchards in late winter (August), the dispensers can be expected to remain effective until next February in southeastern Australia, covering the period when most fruit scarring caused by its larvae occurs.     

Habitat associations of an insular Wallacean avifauna: A multi-scale approach for biodiversity proxies

The endemic avifauna of Wallacea is of high conservation significance, but remains poorly studied. Identifying priority conservation areas requires a greater understanding of the habitat associations of these bird communities, and of how spatial scale of analysis can influence the interpretation of these associations. This study aims to determine which proxy habitat measures, at which spatial scales of analysis, can provide useful inferential data on the composition of Wallacean forest avifauna. Research was conducted within the Lambusango forest reserve, South-East Sulawesi, using point count surveys to sample avifauna. Habitat properties were characterised in three ways: broad classification of forest type, canopy remotely-sensed response derived from satellite imagery, and in situ measures of vegetation composition and structure. Furthermore, we examined avifauna–habitat relationships at three spatial scales: area (c.400 ha per sample site), transect (c.10 ha) and point (c.0.2 ha). Results demonstrate that broad forest type classifications at an area scale can help to determine conservation value, indicating that primary and old secondary forests are important for supporting many species with lower ecological tolerances, such as large-bodied frugivores. At the transect-scale, significant congruence occurs between bird community composition and several habitat variables derived from vegetation sampling and satellite imagery, particularly tree size, undergrowth density, and Normalised Difference Vegetation Index (NDVI) values; this highlights the importance small scale habitat associations can have on determining α-diversity. Analysis at the point-scale was ineffective in providing proxy indications for avifauna. These findings should be considered when determining future priority conservation areas for Wallacean avifauna.     

Biological control of citrus mealybug,Planococcus citri with an introduced parasite,Leptomastix dactylopii in India

Planococcus citri (Risso) is one of the major pests of citrus orchards in India. For the control ofP. citri, an encyrtid parasite,Leptomastix dactylopii How. was introduced from West Indies in 1983. The parasite was mass bred and inoculative releases were made in 2 selected citrus orchards where infestation of mealybug on fruits (sweet orange, seedless lime and acid lime) ranged from 38 to 65 per cent. Establishment of the parasite in the 2 release orchards resulted in complete control of the mealybug within 3 to 4 months. No insecticidal sprays were required subsequently for the control ofP. citri in the following seasons. Contribution No. 152/85 of the IIHR, Bangalore — 560089.     

Efficacy of pheromonal control of peachtree borer (Synanthedon exitiosa (Say)) in small‐scale orchards

The efficacy of pheromone‐based mating disruption for control of the peachtree borer Synanthedon exitiosa (Say) in small‐scale peach orchards (<0.1 ha) was evaluated in a total of six blocks at two locations in New Mexico, USA, from 2010 to 2015. In treated orchards, commercial pheromone dispensers were deployed at rates of approximately 500 or 600 per ha. Pheromone‐based monitoring traps were installed in each block (treated and untreated), and catches of male moths were recorded throughout each growing season to assess the effectiveness of pheromone treatments and to determine the pest's seasonal flight activity. Levels of larval trunk infestation were assessed twice yearly by inspecting all trees at and below soil level. Infestation levels in an unreplicated block of mature peaches at one site (Los Lunas) declined from 57.5% to 8.4% while under pheromone treatment (2010–2011). Pheromone treatments in this block were discontinued in 2012, and infestation levels subsequently increased to 16.9% by spring 2015. In a replicated study in four other peach blocks at the same site, annual application of pheromones from 2012 to 2014 resulted in a significant difference in larval infestations in treated blocks compared to untreated blocks. In addition, when a single block of infested peaches at a second site (Alcalde) was treated with pheromone dispensers for three consecutive years, trunk infestation levels declined significantly, but were not completely eliminated. These results indicate that mating disruption can help protect even very small orchards from damage by S. exitiosa. However, the technique is likely to be more effective where such orchards are relatively isolated and/or where the surrounding pest pressure is moderate or low.     

Termite mound density and distribution patterns across three land-use types in the Vhembe District of the Limpopo Province,South Africa

This study investigated the effect of land-use on density and distribution patterns of termite mounds. A total area of 12 ha was investigated using four 1 ha plots from each of three land-use types (mango orchards, maize fields and communal rangelands). A total of 297 mounds from four termite species were recorded. Plotted GIS coordinates for each mound in ArcMap showed a random distribution pattern in all land-use types. The mean number of mounds per hectare was significantly higher (p < 0.001) in communal rangelands (52.5 ± 1.21), than in maize fields (14.75 ± 3.15) and mango orchards (7.5 ± 0.87), and dominated by small-sized mounds of Trinervitermes sp. Few mounds of Odontotermes sp. were found. Mounds of the edible termites, Macrotermes natalensis and M. falciger, were found in all land-use types, with the highest density for both species being in maize fields. Although the mound height for both species was similar, mound circumference for M. falciger was significantly larger (p < 0.001) which may limit land available for agricultural use. Density of mounds was influenced by land-use which may lead to changes in termite ecosystem functioning and availability of termites as a free source of protein.     

多次释放胡瓜新小绥螨对橘园节肢动物群落多样性的影响

为了探明长期多次释放胡瓜新小绥螨(Neoseiulus(Amblyseius)cucumeris)是否会对橘园节肢动物群落的生物多样性产生影响,我们在福州马尾和晋安试验区的2个橘园分别设置生防园、自然园和化防园,连续两年每月两次在各处理橘园的树冠和地面杂草中采集并记录节肢动物的种类和数量,结果表明两个试验区的物种丰富度(S)均以生防园最高,且都显著高于相应的化防园和自然园;马尾试验区三种处理的多样性指数(H’)和均匀度指数(E)的大小依次为生防园>自然园>化防园,晋安试验区则为自然园>生防园>化防园,表明释放胡瓜新小绥螨防治柑橘害螨,减少农药的使用,能恢复或增加橘园节肢动物群落的生物多样性。此外,释放胡瓜新小绥螨未对橘园原有的捕食螨类群产生影响。     

Utilizing spectral vegetation indices for yield assessment of tomato genotypes grown in arid conditions

Tomato is among important vegetable crops cultivated in different climates; however, heat stress can greatly affect fruit quality and overall yield. Crop reflectance measurements based on ground reflectance sensor data are reliable indicators of crop tolerance to abiotic stresses. Here, we report on using non-destructive spectral vegetation indices to monitor yield traits of 10 tomato genotypes transplanted on three different dates (Aug. 2, Sept. 3 and Oct. 1) during 2019 growing season in the Riyadh region. The ten genotypes comprised six commercial cultivars–(Pearson Improved, Strain B, Valentine, Marmande VF, Super Strain B, and Pearson early) ––and four local Saudi cultivars (Al-Ahsa, Al-Qatif, Hail and Najran). Spectral reflectance data were utilized using a FieldSpec 3 spectroradiometer in the range of 350–2500 nm to calculate nine vegetation indices (VIs): Normalized Water Band Index (NWBI), Difference Water Index (NDWI), Photochemical Reflectance Index (PRI), Normalized Difference Vegetation Index (NDVI), Green Normalized Difference Vegetation Index (GNDVI), Red Edge Normalized Difference Vegetation Index, Soil Adjusted Vegetation Index (SAVI), Red Edge Normalized Difference Vegetation Index (RENDVI), Renormalized Difference Vegetation Index (RDVI), and Normalized Difference Nitrogen Index (NDNI). VIs and yield parameters (total fruit yield, harvest index) revealed that second transplanting date was optimal for all the genotypes. Valentine showed the best growth performance followed by Najran, Hail, Super Strain B and finally Pearson early. For all the three transplanting dates, Valentine recorded the highest total fruit yield. Additionally, some genotypes had no significant differences in the VIs values or the total fruit yield between the second and third transplanting dates. This study indicated that yield parameters could be linked to rapid, non-destructive hyperspectral reflectance data to predict tomato production under heat stress.     

A new synergistic approach for Sentinel-1 and PALSAR-2 in a machine learning framework to predict aboveground biomass of a dense mangrove forest

Mangroves are well-recognized for their very high carbon sequestration potential. However, studies on their role in global carbon cycling and climate change are hindered due to lack of operational methodologies to model and map their biophysical properties. This study establishes a robust methodological protocol for aboveground biomass (AGB) estimation using i) field measurements, ii) a generic (in the absence of species-specific) allometric equation, iii) multi-sensor/polarization SAR data and derived variables thereof, and iv) machine learning models; that demonstrated high prediction accuracy (R² = 0.93) and low uncertainty (mean ≤ 3% and median ≤ 1.5%) for a mangrove forest. Following stratified random sampling and on-field accessibility criteria, we laid out 314 elementary sampling points of 0.04 ha each at Bhitarkanika wildlife sanctuary (BWS), India and measured circumference at breast height (CBH) and canopy tree height for 18 species. The estimated AGB range of a generic allometric equation was 9–474 Mg/ha for BWS, with a major representation of 9–347 Mg/ha. We utilized Sentinel-1 and ALOS-2/PALSAR-2 and derived their variables for AGB prediction. Compared to single sensor-based model, we observed higher prediction accuracy for combined sensor data (R² = 0.63, 0.87, 0.93; RMSE = 66.75, 39.95, 28.35 Mg/ha; MAE = 52.63, 24.21, 19.55 Mg/ha; and Bias = 3.42, 0.22, 2.15 Mg/ha for C, L and C & L bands respectively using a Generalized Additive Model (GAM) over Random Forest (RF), Gradient Boosting Machines (GBM) and Support Vector Regression (SVR). The higher uncertainty pixels represented seasonal grassland and scrubs in the swampy areas and along the fringes of the creeks that experience diurnal tidal fluctuations. This robust methodology can be replicated for AGB estimates in other mangrove ecosystems to meet the operational carbon accounting requirements of various entities.