LAI Values Research Articles

MORPH PHYSIOLOGICAL TRAITS OF SAFFLOWER AS AFFECTED BY PLANT DENSITIES AND NITROGEN FERTILIZATION

This study carried out at a private farm in Elmhamid village ,Arment district , Luxor governorate, Egypt in 2016/2017 and 2017/2018 growing seasons for determine the effect of plant densities , different nitrogen sources and doses on the safflower cv. Giza (carthamus tinctorius) morphological and physiological characteristics. The experimental design was split-split plot set up with three replicates in both studied seasons was followed. The main plots were devoted to three plant densities viz, 35, 47 and 70 thousand plants/fad., and sub-plots were allotted to the three forms of nitrogen, i.e. ammonium sulphate, ammonium nitrate and urea, while the four nitrogen fertilizer levels were randomely arranged in the sub-sub-plots. The highest plant density of 70000 plants fad.-1 recorded the highest values of plant height and LAI at the growth stages i.e 65, 86 and 107 days from sowing in both seasons, while, the lowest plant density of 35000 plants/fad.-1 recorded highest values of number of green leaves plants/fad.-1 , number of branches plants-1, dry weight plants-1(gm) and leaf area plants-1in the three growth stages in both growing seasons. The nitrogenous fertilizer forms had a significant effects on plant height at 107 days in the two growing seasons, But the other studied traits not show any significant response by the studied treatments under the two growing season at any growth stages . The highest values were recorded by using urea as the best form of nitrogen fertilizer under this experiment conditions. The nitrogenous fertilizer levels had a significant effects on all studied traits at the different growth stages and the two growing seasons indicated the important of nitrogen fertilization on safflower under site of experiment. Conclusively, from these results it could be concluded that to increase the number of branches’ / plant and leaf area index should be apply 60kg/fed level of nitrogen with low plant density.

Thermal performance assessment of extensive green roofs investigating realistic vegetation-substrate configurations

Green roofing is a sustainable solution for building energy saving, urban heat island mitigation, rainwater management and pollutant absorption. The effectiveness and performance of green roofs depend on layer composition and properties. The uncertainties surrounding green roof performance modeling are mainly related to the vegetation and substrate layer, which are subjected to surrounding climatic conditions. Energy simulation software typically does not use validated models encompassing all possible combinations of vegetation layers and substrates. Therefore, the objective of this research is to investigate different extensive green roof solutions for assessing thermal performance and to provide information on vegetation and substrate layer design. Different simulations executed in EnergyPlus were carried out based on realistic literature data drawn from previous experimental tests conducted on plants and substrates. Several combinations (30 plant-substrate configurations, six vegetative species and five types of substrates) were defined and evaluated. Furthermore, indexes based on the surface temperatures of green roofs were used. Finally, a comprehensive ranking was created based on the scores to identify which extensive green roof combinations offered the highest performance. Greater plant heights, LAI values and leaf reflectivity values improve green roof energy performance in the summer more significantly than substrate modification. During the winter, thermal performance is more heavily dependent on the substrate if succulent vegetation is present, regardless of the substrate used. These results could provide designers with useful data at a preliminary stage for appropriate extensive green roof selection.

Soil water repellency decreases summer maize growth

A two-year summer maize irrigation experiment was conducted in soil lysimeters under a rain-shelter to analyze the effects of water repellency on soil moisture, evapotranspiration, crop growth, and yields. Soil water droplet penetration time (WDPT) was initially 1, 7, 9, 12 and 16 s, showing wettable or slight water repellency, denoted as the treatments CK, WR1, WR2, WR3, and WR4, respectively. Soil water storage dynamics were observed using the lysimeters. The WDPT and volumetric soil water content (θv) on surface soil was measured daily. The results revealed that WDPT values of all the five treatments increased significantly as the sowing days increased and reached peaks before the subsequent irrigation. However, the peak decreased as irrigation events increased. The maximum WDPT values of CK, WR1, WR2, WR3, and WR4 were 31, 2000, 2200, 2300 and 2355s during the entire crop growth period, and indicated more persistent water repellency than the initial conditions. During the two irrigations, θv decreased with the increase of WDPT. The daily and cumulative evapotranspiration at the early growth stage differed slightly but decreased from CK to WR4 at the later crop growth stages. Likewise, soil water storage increased. The higher water consumption of summer maize in CK resulted in lower soil water storage and good plant growth, thus in soils with higher WDPTs, the lower values of LAI, the mass of roots and leaves, and root lengths were noted. The crop growth decreased regularly with the increase in initial WDPT. The main reason was due to a decrease in soil water availability for the crop and impeded root water uptake as the initial WDPT increased. The variation in initial WDPTs had a significant impact on WUE. In conclusion, more persistent water repellent soils result in a decrease in summer maize growth.

Modeling multi-decadal mangrove leaf area index in response to drought along the semi-arid southern coasts of Iran

Leaf Area Index (LAI; as an indicator of the health) of the mangrove ecosystems on the northern coasts of the Persian Gulf and the Gulf of Oman was measured in the field and modeled in response to observed (1986–2017) and predicted (2018–2100) drought occurrences (quantified using the Standardized Precipitation Index [SPI]). The relationship of LAI with the normalized difference vegetation index (NDVI) obtained from satellite images was quantified, the LAI between 1986 and 2017 retrospectively estimated, and a relationship between LAI and SPI developed for the same period. Long-term climate data were used as input in the RCP8.5 climate change scenario to reconstruct recent and forecast future drought intensities. Both the NDVI and the SPI were strongly related with the LAI, indicating that realistic LAI values were derived from historic satellite data to portray annual changes of LAI in response to changes in SPI. Our findings show that projected future drought intensities modeled by the RCP8.5 scenario increase more and future LAIs decreased more on the coasts of the Gulf of Oman than the coasts of the Persian Gulf in the coming decades. The year 1998 was the most significant change-point for mean annual rainfall amounts and drought occurrences as well as for LAIs and at no time between 1998 and 2017 or between 2018 and 2100 are SPI and LAI values expected to return to pre-1998 values. LAI and SPI are projected to decline sharply around 2030, reach their lowest levels between 2040 and 2070, and increase and stabilize during the late decades of the 21st century at values similar to the present time. Overall, this study provides a comprehensive picture of the responses of mangroves to fluctuating future drought conditions, facilitating the development of management plans for these vulnerable habitats in the face of future climate change.

AN INSIGHT INTO THE VOLUME COMPONENT GENERATED FROM RISAT-1 HYBRID POLARIMETRIC SAR DATA FOR CROP BIOPHYSICAL PARAMETERS RETRIEVAL

Abstract. Polarimetric parameters have been extensively used for target parameters retrieval than backscattering coefficients. In previous studies, volume component generated from polarimetric SAR data has been considered as the return signal component from vegetation and intern used this for biophysical parameters retrieval. Un-polarized component of the return signal has been considered as volume component. The present study is mainly focused to analyze the volume component generated from C-band RISAT-1 hybrid polarimetric SAR data from wheat crop. Three temporal datasets acquired at ∼31° central incidence angle between Jan and Mar 2016 over parts of Bharatpur and Mathura districts located in Rajasthan and Uttar Pradesh (India) have been used in this study. Water Cloud Model with Gaps has been considered for modeling the first Stokes parameter (g0), which represents total intensity of return signal, from wheat crop using LAI and Interaction factor as vegetation descriptors. The vegetation component derived using calibrated Water Cloud Model with Gaps has been analyzed with volume component derived from RISAT-1 hybrid polarimetric SAR data. The analyses observed that a significant difference during lower LAI values and shown comparably during higher LAI values. The higher values of volume component derived from RISAT-1 SAR data than modeled vegetation component indicates that the volume component can also be generated by underneath soil. It is also observed the difference in derived un-polarized component and modeled vegetation component has shown higher correlation with underneath soil moisture than directly correlating with derived un-polarized component. This study indicates that the volume component derived from hybrid polarimetric SAR data has return signals from vegetation as well as underneath soil.

Artificial neural network models predicting the leaf area index: a case study in pure even-aged Crimean pine forests from Turkey

BackgroundLeaf Area Index (LAI) is an important parameter used in monitoring and modeling of forest ecosystems. The aim of this study was to evaluate performance of the artificial neural network (ANN) models to predict the LAI by comparing the regression analysis models as the classical method in these pure and even-aged Crimean pine forest stands.MethodsOne hundred eight temporary sample plots were collected from Crimean pine forest stands to estimate stand parameters. Each sample plot was imaged with hemispherical photographs to detect the LAI. The partial correlation analysis was used to assess the relationships between the stand LAI values and stand parameters, and the multivariate linear regression analysis was used to predict the LAI from stand parameters. Different artificial neural network models comprising different number of neuron and transfer functions were trained and used to predict the LAI of forest stands.ResultsThe correlation coefficients between LAI and stand parameters (stand number of trees, basal area, the quadratic mean diameter, stand density and stand age) were significant at the level of 0.01. The stand age, number of trees, site index, and basal area were independent parameters in the most successful regression model predicted LAI values using stand parameters (R2adj. = 0.5431). As corresponding method to predict the interactions between the stand LAI values and stand parameters, the neural network architecture based on the RBF 4–19-1 with Gaussian activation function in hidden layer and the identity activation function in output layer performed better in predicting LAI (SSE (12.1040), MSE (0.1223), RMSE (0.3497), AIC (0.1040), BIC (− 77.7310) and R2 (0.6392)) compared to the other studied techniques.ConclusionThe ANN outperformed the multivariate regression techniques in predicting LAI from stand parameters. The ANN models, developed in this study, may aid in making forest management planning in study forest stands.

Efficacy of ascorbic acid as a cofactor for alleviating water deficit impacts and enhancing sunflower yield and irrigation water–use efficiency

Ascorbic acid (AsA) is considered as one of the most important and profusely known occurring water soluble antioxidants in plants, however, it is not well known to what extent this antioxidant might contribute in alleviating the adverse effects of water deficit on plant growth, yield and irrigation water use efficiency (IWUE). In attempt to clarify whether exogenous application of AsA could alleviate the adverse effects of water deficit on sunflower plants, two seasons (2014 and 2015) of field experimentation were conducted using six combinations of two AsA levels (AsA(–) and AsA(+), i.e. zero and 450 ppm AsA, respectively) and three irrigation water amounts (I100, I85, and I70, i.e. 100, 85 and 70% of crop evapotranspiration, respectively). Under water shortage, leaf chlorophyll content increased but proline content lowered in AsA–treated plants compared to the untreated ones. Lower values of LAI, head weight, seed yield ha–1, and oil yield ha–1 were recorded with decreasing water supply, while the highest values were gained when supplying plants with sufficient water (I100) plus application of AsA (i.e. AsA(+)), i.e., I100AsA(+). Plants under the latter treatment grew well and possessed higher yields compared to that of suffering from deficit water without AsA application, i.e. I85AsA(–) or I70AsA(–). Head weight and seed as well as oil yields ha–1 produced in 2014 season under sufficient water supply without AsA application (I100AsA(–)) could be achieved under moderately water–stressed condition in conjunction with applying AsA (I85AsA(+)). Implication of AsA tends to minimize the reduction in seed yield due to insufficient water supply, where I85AsA(+) and I85AsA(–), each saved same percentage of water (15.0%) but the reduction in seed yield associated the former treatment was less than that under the latter one. On the other hand, IWUE reached the maximal values in both seasons under I100AsA(+) treatment but, however, without marked differences in comparing to those recorded I85AsA(+) in 2014 season. Moreover, the differences in IWUE values exhibited by I100AsA(–) and I85AsA(+) did not reach the P < 0.05 level of significance in 2015 season, which could reveal the positive role of AsA in alleviating water stress.

Aerodynamic properties of green gram sown in different environments in Indo- Gangetic Plains of West Bengal

Field experiments were conducted on green gram during spring-summer seasons of 2011 and 2012 with four dates of sowing and five varieties arranged in a strip-plot design to study the aerodynamic characteristics of green gram at BCKV, Kalyani, West Bengal. Micro-cup anemometers were placed at 0.5, 1.0, 1.5, 2.0 and 2.5 m above the crop canopy on a wooden mast. The zero-plane displacement (d), roughness length (Z0) and drag coefficient (Cd) were found to increase with crop age but the effect of dates of sowing was not prominent except at the final stage of growth. For a LAI value of 1.5, “d” values was 0.254 m and the “Cd” value was 0.015. Both the “Cd” and “d” increased with plant height and LAI. The “d” and “Z0” had significant positive correlation with the total dry matter and crop growth rate irrespective of dates of sowing.

Reflectance, absorbance and transmittance spectra of bermudagrass and manilagrass turfgrass canopies.

Leaves act as a primary organ for the interception of solar radiation and their spatial arrangement determines how the plant canopy interacts with light. Many studies have been carried out on the penetration of radiation into crops however to date, few results are available on turfgrasses, mainly due to the difficulties of introducing sensors into the turf without disturbing the natural position of the leaves. In the present research two warm season turfgrasses, hybrid bermudagrass (Cynodon dactylon × transvaalensis) 'Patriot' and manilagrass (Zoysia matrella) 'Zeon', were studied. The aim was to describe their canopy architecture grown with minimal disturbance to the natural arrangement of the leaves and stems, and to determine the potential effects of canopy architecture on light penetration and reflectance. Radiometric measurements were carried out at eight different profile levels of turfgrasses that were up to 12 cm tall. A LI-COR 1800 spectroradiometer with an optical fiber cable and a 7 mm diameter sensor was used. Measurements were carried out in the 390–1100 nm region at 5 nm intervals. The LAI value was higher for the manilagrass (9.0) than for the hybrid bermudagrass (5.6). The transmitted radiation was found to be closely dependent on downward cumulative LAI. Despite a more upright habit (mean insertion angle of 22.4° ±3.4), Zoysia matrella showed a higher NIR reflectance compared to Cdxt, which has a horizontal leaf arrangement (mean insertion angle 62.1° ± 9.6). The species studied showed substantial differences both in terms of phytometric characteristics and in the capacity to attenuate solar radiation.

Influence of Plant Population and Weed Control Treatments on Associated Weeds, Growth, Yield and Quality of Faba Bean

To investigate the effect of faba bean plant populations (80000, 96000 and 120000 plants/feddan) resulted from the difference between hill spacing (30, 25 and 20 cm) and the efficiency of eight weed control treatments (butralin, metribuzin, oxadiargyl, each previous herbicides followed by one hand hoeing, two hand hoeing and unweeded check) on associated weeds, growth, yield and its attributes as well as chemical analysis. Two field experiments were conducted at the Experimental farm of El-Serw Research Station, Agricultural Research Center, Damietta Governorate, Egypt during winter seasons of 2015/2016 and 2016/2017. Main findings showed that increasing plant population from 80000 to 120000 plants/fedsignificantly decreased the broadleaved, grassy and total weeds dry weight by 46.32, 33.44 and 43.77% in the first season and by 45.99, 38.10 and 44.32% in the second season, respectively after 70 days from sowing. Plant population of 120000 plants/fed produced the highest values of plant height, dry weight/plant and LAI in both seasons. Moreover, sowing faba bean at 120000 plants/fedincreased seed yield/fed by 15.46 and 5.03% in the first season and 16.33 and 7.84% in the second season compared with 80000 and 96000 plants/fed, respectively. Two hand hoeing method significantly decreased the broadleaved, grassy and total weeds dry weight by 93.58, 99.24 and 95.68% in the first season and 92.62, 98.95 and 94.89% in the second season, respectively compared with the unweeded check. The results indicated that two hand hoeing method was the most superior treatment in increasing plant height, dry weight/plant and leaf area index at 70 and 90 days from sowing as well as yield, yield attributes and chemical composition of faba bean seeds followed by applying oxadiargyl herbicide with one hand hoeing treatment. It could be recommended that growing faba bean at plant population 120000 plants/fed integrated with two hand hoeing or oxadiargyl herbicide with one hand hoeing maximized seed yield per unit area.

Growing lettuce under multispectral light-emitting diodes lamps with adjustable light intensity

Light-Emitting Diodes (LEDs) technology offers vast possibilities in plant lighting due to its ability to mix different light frequencies, high energy use efficiency and low heat production combined to long lifespan. In particular, the combined effect of the Blue:Red (B:R) ratio and other frequencies in the central part of the PAR spectrum (CGA, &lt;em&gt;i.e.&lt;/em&gt; cyan, green and amber) may be very important, though literature information is scarce. In this paper, the effects of six light spectra from LED technology were tested, &lt;em&gt;i.e.&lt;/em&gt;: (i) B:R=0.82 (&lt;em&gt;i.e.&lt;/em&gt; similar to sunlight) with CGA (treatment T0), (ii) B:R=0.82 without CGA (T1), (iii) red prevalence (B:R=0.25) without CGA (T2), (iv) blue prevalence (B:R=4) without CGA (T3), (v) red prevalence with CGA (T4) and (vi) blue prevalence with CGA (T5). The experiment was carried out in a walk-in climatic chamber with controlled temperature and relative humidity and an incident PAR photon flux density (PFD) of 300 μmol m&lt;sup&gt;–2&lt;/sup&gt; s&lt;sup&gt;–1&lt;/sup&gt; (14/10 light/dark photoperiod), generated by multispectral LED lamps with adjustable light intensity. Smooth leaved lettuce (Lactuca sativa L. cv Gentilina) was used as the test plant and biomass yield (DW, g m&lt;sup&gt;–2&lt;/sup&gt;), LAI, soil coverage proportion (SC%), energy-biomass conversion efficiency (E-BCE, kWh g&lt;sup&gt;–1&lt;/sup&gt;) and Radiation Use Efficiency (RUE, g mol&lt;sup&gt;–1&lt;/sup&gt; photons) were determined. Treatments with red predominance (T2 and T4) showed the highest SC% rates, while those with blue predominance (T3 and T5) showed the lowest. Light spectrum also affected leaf size (&lt;em&gt;i.e. &lt;/em&gt;mean leaf area). The highest DW and RUE were observed in T2 and T4, followed by T0, while biomass in T3 and T5 was significantly lower (similar to T1). LAI values were generally high, but treatments with blue predominance showed the lowest LAI values (both with or without CGA). The introduction of intermediate wavelengths (green, cyan and amber) did not bring about significant improvement in DW or RUE, but resulted in reduced energy-biomass conversion efficiency, mainly due to lower architectural efficiency of the CGA LEDs. Future research should clarify how to optimise the light spectra according to the crop growth phases. The adoption of spectra promoting fast growth is fundamental in the early growth, while the use of spectra maximising yield quality may be more important later on.

English

The growth and senescence of Urochloa brizantha cv. Marandu were analyzed under the Brazilian Cerrado conditions. The seeds were sowed in November at the beginning of the rainy season. Samples of tillers were collected. The culms, inflorescences, along with green and dead leaves were removed to obtain leaf area and dry matter measurements. The maximum leaf area index (LAI = 5.80 m2 m-2) was achieved at 97 days after emergence (DAE), the maximum above ground total dry matter (TDM = 22.8 Mg ha-1) at 151 days, and the maximum crop growth rate (CGR = 0.260 Mg ha-1) at 70 days. Leaf senescence began at 55 DAE, with less than 0.001 Mg ha-1 of dead leaves dry matter (DLDM), and reached 1.753 Mg ha-1 at 151 DAE. Between 117 and 151 DAE, in the final cycle of the plants, there was lodging of the canopy by wind. This lodging had favored the sprouting of new tillers and a sudden increase in net assimilation rate (NAR). The LAI values did not show such expressive increase during the same period, suggesting that NAR may contribute to crop growth more than LAI due to increased light penetration after the occurrence of the lodging. In this paper an equation that estimates the net photosynthetic rate from the net assimilatory rate was presented. Key words: Leaf area, dry matter, growth rate, net assimilation rate, pasture grass

Estimating the leaf area index in Indian tropical forests using Landsat-8 OLI data

ABSTRACTLeaf area index (LAI) is a key vegetation biophysical parameter and is extensively used in modelling of phenology, primary production, light interception, evapotranspiration, carbon, and nitrogen dynamics. In the present study, we attempt to spatially characterize LAI for natural forests of Western Ghats India, using ground based and Landsat-8 Operational Land Imager (OLI) sensor satellite data. For this, 41 ground-based LAI measurements were carried out across a gradient of tropical forest types, viz. dry, moist, and evergreen forests using LAI-2200 plant canopy analyser, during the month of March 2015. Initially, measured LAI values were regressed with 15 spectral variables, including nine spectral vegetation indices (SVIs) and six Landsat-8 surface reflectance (ρ) variables using univariate correlation analysis. Results showed that the red (ρred), near-infrared (ρNIR), shortwave infrared (ρSWIR1, ρSWIR2) reflectance bands (R2 > 0.6), and all SVIs (R2 > 0.7) except simple ratio (SR) have the highest and second highest coefficient of determination with ground-measured LAI. In the second step, to select significant (high R2, low root mean square error (RMSE), and p-level < 0.05) SVIs to determine the best representative model, stepwise multiple linear regression (SMLR) was implemented. The results indicate that the SMLR model predicted LAI with better coefficient of determination (R2 = 0.83, RMSE = 0.78) using normalized difference vegetation index, enhanced vegetation index, and soil-adjusted vegetation index variables compared to the univariate approach. The predicted SMLR model was used to estimate a spatial map of LAI. It is desirable to evaluate the stability and potentiality of regional LAI models in natural forest ecosystems against the operationally accepted Moderate Resolution Imaging Spectroradiometer (MODIS) global LAI product. To do this, the Landsat-8 pixel-based LAI map was resampled to 1 km resolution and compared with the MODIS derived LAI map. Results suggested that Landsat-8 OLI-based VIs provide significant LAI maps at moderate resolution (30 m) as well as coarse resolution (1 km) for regional climate models.

ESTRUTURA ARBÓREA E SAZONALIDADE DA COBERTURA DO DOSSEL EM VEGETAÇÃO FLORESTADA E ABERTA NO PARQUE NACIONAL SERRA DE ITABAIANA, SERGIPE, BRASIL

As florestas de areias brancas quartzosas constituem um tipo de ecossistema oligotrófico, cujos caracteres fitofisionômicos são afetados pela sazonalidade climática. Entre tais características está a abertura do dossel, cujas variações influenciam na distribuição espacial da luz solar no ambiente. Este estudo avaliou e comparou a estrutura da vegetação e as alterações sazonais do dossel em habitat de areias brancas do Parque Nacional Serra de Itabaiana, Sergipe. Os dados foram coletados em dois ambientes: vegetação aberta de areias brancas strictu sensu (VA) e mata fechada de vegetação ripária (MR). Para estimar a densidade arbórea utilizou-se o método quadrante, no qual foram amostradas árvores com CAP ≥ 5 cm. Para avaliar a dinâmica do dossel foram estabelecidos, em cada área, dois transectos compostos por cinco pontos equidistantes 20 m, totalizando 10 pontos por ambiente. Em cada ponto foram obtidas fotografias hemisféricas do dossel nos meses de janeiro (seca) e junho (chuva). As imagens foram analisadas pelo software Gap Light Analyzer, sendo avaliadas as variáveis abertura do dossel e índice de área foliar (IAF). A vegetação ripária apresentou densidade arbórea de 498 ind ha-1 e a vegetação aberta 296 ind ha-1. Esta última, não evidenciou variações na abertura do dossel (t = 2,0146; p &gt; 0,05) e no IAF (t = -2,0052; p &gt; 0,05) entre os períodos de chuva (52,24% ± 18,13% e 0,68 ± 0,45) e seca (67,39% ± 15,38% e 0,36 ± 0,23). Na mata ripária, a abertura do dossel (t = 7,1739; p &lt; 0,05) e o IAF (t = -5,1609; p &lt; 0,05) variou entre os períodos de chuva (13,70% ± 2,24% e 2,13 ± 0,23) e seca (21,08% ± 2,36% e 1,63 ± 0,20). As diferenças observadas destacam a heterogeneidade ambiental na Serra de Itabaiana e demonstram que as formações florestais de areias bancas respondem de maneira distinta à sazonalidade hídrica deste ecossistema. Por estar localizada em uma área de ecótono entre floresta perene e Floresta Estacional Semidecidual, a mata ripária tende a perder parte de suas folhas durante o período seco. Além disso, o padrão de distribuição das plantas pode contribuir para as diferenças entre os habitat estudados.

Yield response of ten varieties of sweet potato (Ipomoea batatas L.) cultivated on dryland in rainy season

Sweet potato is a tuber commodity and one of alternative crops in Indonesia. The demand of sweet potato in Indonesia continues to increase. However, the supply of sweet potatoes for consumption estimated is 2020 in Indonesia will be deficit. Low production of sweet potato is basically due to the decrease of land area as cultivation production and also sweet potatoes have a low yield when planted in rainy season. Based on the high utilization of sweet potato make demand for this commodities continues to increase.Therefore, several strategies to increase crop yields of sweet potato needs to be done. This study aimed to elucidate various sweet potato varieties that can cultivated on dry land in the rainy season. This study was conducted from November 2016 until March 2017 using a randomized block design with treatments of ten varieties of sweet potato consisting of (V1) Papua Solossa variety, (V2) Jago variety, (V3) Kidal variety, (V4) Antin-1variety, (V5) Sari variety, (V6) Sawentar variety, (V7) Beta-2variety, (V8) Antin-2variety, (V9) Antin-3 variety, (V10) Beta-1variety. The results showed different responses of each variety.The vegetative growth was high as shown by the LAI value of 7.23 at 90 days after planting. In conclusion, the sweet potato leaves had to be prune to boost the agronomic yield. Yields of ten varieties of sweet potato crops ranged from 8.86 to 44.76 t/ha. Some varieties such as Sari, Papua Salosa and Beta-2 varieties showed high yield although they were planted in moorland conditions in the rainy season.

Chronological Sequence of Leaf Phenology, Xylem and Phloem Formation and Sap Flow of Quercus pubescens from Abandoned Karst Grasslands.

Intra-annual variations in leaf development, radial growth, including the phloem part, and sap flow have rarely been studied in deciduous trees from drought-prone environments. In order to understand better the chronological order and temporal course of these processes, we monitored leaf phenology, xylem and phloem formation and sap flow in Quercus pubescens from abandoned karst grasslands in Slovenia during the growing season of 2014. We found that the initial earlywood vessel formation started before bud opening at the beginning of April. Buds started to open in the second half of April and full leaf unfolding occurred by the end of May. LAI values increased correspondingly with leaf development. About 28% of xylem and 22% of phloem annual increment were formed by the time of bud break. Initial earlywood vessels were fully lignified and ready for water transport, indicating that they are essential to provide hydraulic conductivity for axial water flow during leaf development. Sap flow became active and increasing contemporarily with leaf development and LAI values. Similar early spring patterns of xylem sap flow and LAI denoted that water transport in oaks broadly followed canopy leaf area development. In the initial 3 weeks of radial growth, phloem growth preceded that of xylem, indicating its priority over xylem at the beginning of the growing season. This may be related to the fact that after bud break, the developing foliage is a very large sink for carbohydrates but, at the same time, represents a small transpirational area. Whether the interdependence of the chronological sequence of the studied processes is fixed in Q. pubescens needs to be confirmed with more data and several years of analyses, although the ‘correct sequence’ of processes is essential for synchronized plant performance and response to environmental stress.

Variações da reflectância e dos índices de vegetação em função dos parâmetros da modelagem topográfica no Parque Estadual do Turvo, Rio Grande do Sul, Brasil

Remote sensing techniques have been widely used in forestry studies as they allow evaluation and monitoring of large forested areas. The Parque Estadual do Turvo (pet) (17 491 ha) is the largest remaining tract of well-preserved subtropical deciduous forest in Southern Brazil, it constitutes the northern-most portion of the Misiones forest of Argentina (10 000 km2). The area is of great environmental importance and is suitable for conducting remote sensing studies using high or even coarse-to-moderate spatial resolution data and related vegetation indices. Both, reflectance values and vegetation indices are affected by external factors that modify the spectral response of surface elements. Among the factors that can induce errors in image interpretation are topographic effects that add spectral variability to satellite products. In addition, previous studies in subtropical forests have shown that the geometry of data acquisition also affects significantly the estimates of vegetation parameters derived from images acquired at off-nadir viewing or by sensors with large field-of-view (FOV).This study aimed to evaluate the magnitude of variations in bidirectional reflectance values and in vegetation indices derived from those, as a function of local topography, using high spatial resolution data acquired by the RapidEye satellite constellation.The method included the use of a digital elevation model (dem) from the Advanced Space-borne Thermal Emission and Reflection Radiometer – Global Digital Elevation Map version 2 (aster gdem v2) and two RapidEye scenes. From the dem, topographical parameters including slope aspect (eight classes), elevation (nine classes with 120-m spacing interval) and shaded relief (shaded, intermediate and sunlit surfaces) were derived. These data provide information on areas with or without direct exposure to solar radiation, depending on topographic features. RapidEye data were acquired on June 28, 2012 and October 17, 2012, corresponding to dates when the forest shows low or high leaf area index (lai), respectively. Both scenes were acquired with a view angle close to nadir. Solar elevation angles for the June and October images were 37.93° and 71.25°, respectively. The RapidEye data were corrected for atmospheric effects using the Fast Line-of-sight Atmospheric Analysis of Hypercubes (flaash®). The next step was to perform topographic modeling in order to extract slope, aspect and elevation data. From the topographic variables and the RapidEye metadata, shaded relief was calculated for both scenes. After segmenting the scenes based on the topographic variables, we evaluated the spectral reflectance and vegetation indices, as measured by RapidEye, as a function of topographic parameters. For this purpose, we randomly sampled 1000 pixels from each topographic class. The Normalized Difference Vegetation Index (ndvi) and Enhanced Vegetation Index (evi) were calculated from the RapidEye data. The samples were averaged and analyzed using graphics and descriptive statistics. Select transects were analyzed in more detail to evaluate the effects of local topographic parameters on the remote sensing products. In addition, we conducted forest surveys in 14 plots (20x50m) to produce a floristic-structural characterization of the deciduous forest.The field inventories identified a total of 74 plant species (in 31 families) distributed in three strata and showed the presence of discontinuities within the forest. The results showed that, in addition to seasonal phenological variations, local illumination conditions caused by the relief in the pet contributed to explain the forest spectral response. The topographic variable that most importantly affected the pet spectral response, as measured by RapidEye, was slope aspect. Despite being affected by varying illumination conditions in the two dates, the reflectance and vegetation indices of the June image were most impacted by the shaded relief caused by the low solar elevation and large amount of shadows in the scene. The illumination effects were compounded by the seasonal leaf shedding in the deciduous forests, especially in the upper canopy layer. The winter time (June) scene showed more shaded relief and lower lai values. In the October scene the shade fraction was substantially reduced and leaf shedding reduced the forest canopy anisotropy. A per band analysis showed that the red and near infrared bands were the ones with the highest dependence on aspect and shaded relief. Increases in elevation caused a positive change in near infrared reflectance and a lower reflectance in the visible bands. The ndvi showed lower dependence on topographical conditions than the evi. The evi showed higher sensitivity to illumination conditions, shade and seasonal lai variations.We concluded that the analysis of remote sensing data (reflectance values or vegetation indices such as ndvi and evi) should take into account local topographic effects. In general, the spectral anisotropy in the June scene was higher than in the October scene due the combined effect of deciduousness (leaf shedding), the lower solar elevation and larger amount of shadows.

Influence of some environmental factors on maize productivity in Osun state, Nigeria

Temperature, humidity and direction of the prevailing wind are parts of significant environmental factors, which have greater impact on crop productivity, especially with the recent global climate change. These were researched into on maize seeds planted at three different furrow orientations on the field; Or. 900, Or. 600 and Or. 300 to direction of the prevailing wind on the same plot of land at three replicates A, B and C each. Temperature and humidity were measured at 8.00hr, 10.00hr for morning; 14.00h and 16.00h for afternoon each day. Temperature-Humidity Index-THI was calculated using THI equation. Leaf development was measured in terms of broadness, stem girth, length and number of leaves. Harvest Index, HI and Leaf Area Index, LAI were also calculated. The result shows that at significant level (p &lt; 0.05), effect of Or. was observed on THI values in the afternoon period, but in the morning, significant (p &gt; 0.05) effect of orientation on THI was not observed. The Or. 900 had highest HI of maize and better growth. The LAI values show that Or. 900 had higher LAI (0.775), than that of Or. 600 of value (0.770), between 40th and 70th days. It was found out that orientation of furrow of maize crops to direction of the prevailing is a function of the environmental parameters such as temperature, humidity, and the closer the orientation of furrow slice for crop leaves is towards the 900 wind direction, the better its growth and yield. Key Words: Crop productivity, Leaf Area Index, Temperature-Humidity Index, orientation, Osun State

Estimates of leaf-area index for the territory of Russia using State Forest Inventory data

The 2007 State Forest Inventory (SFI) data have been used at two scales of spatial resolution: the datasets of the forest regions (31) and the forest-management basic units (1900) to estimate the leafarea index (LAI, m2 m–2) of forests in Russia. The area and yield data on all 66 tree species recorded in the SFI offer the opportunity to obtain the wood specific gravity values U (m3 ha–1) for all these tree species. The conversion coefficients of yield to leaf phytomass per unit area (t m–3) and the projected specific leaf areas (SLAs) (cm2 g–1) are used to estimate the LAI. The obtained LAI values are similar to the average ground and remote-sensing estimates (the given review for July includes eighteen literature sources). The highest LAI values can be observed in the middle taiga subzone in the European part of Russia and in the Angara River regions. The LAI estimates may be used to compute the productivity of the forest ecosystems at different scales of analysis and to extrapolate the calibrated data acquired with remote control techniques.

Radiation budget of vegetation canopies with reflective surface: A generalization using the Markovian approach

Empirical and theoretical evidence has shown that the scattering and absorptance of a homogeneous leaf canopy with black soil can be modeled using simple algebraic combinations of two spectrally invariant parameters (the recollision probability and the canopy interceptance) and one spectrally dependent quantity (the single scattering albedo of an average phytoelement). This study generalizes such results for vegetation canopies composed of one or more types of phytoelements and with a reflective background surface also composed of one or more materials, all of which are treated as endmembers of a nonlinear spectral mixture. The conservative radiation field of a canopy is represented by a finite state Markov chain, such that for a vegetation-surface medium composed of m endmembers, the model is thereby parameterized in terms of an m-length vector of endmember interceptances and an mth-order square matrix containing probabilities of photon recollision amongst the endmembers. Comparisons of some instances of the model with radiative transfer based approximations showed how the latter may overestimate canopy reflectance and transmittance. The two-endmembers model was also compared with Monte Carlo simulations for spherically-oriented leaf canopies with reflective soil. Results indicated that the analytical model accurately describes the radiation field for a wide range of soil reflectance and LAI values. Simulations also showed that while the zenith angle of the illumination source has a small influence on the recollision probabilities, the LAI value mainly determines these through distinct functional relationships. The application of the model to estimate the canopy radiation field of two coniferous species located on the Mexico City Conservation Land is also demonstrated using airborne hyperspectral measurements.