Increase In LAI Research Articles

Historical increases of maize leaf area index in the US Corn Belt due primarily to plant density increases

ContextLeaf area index (LAI) and leaf area distribution within the maize plant are important traits used to explain and predict light interception and thus crop productivity. ObjectivesHere we investigate breeding and plant density effects of leaf area traits. Our objectives are to 1) quantify maize breeding impacts on leaf area distribution and determine bell-shape coefficients used in crop modeling, 2) dissect the contribution of breeding from plant density, and 3) explore the relationship between LAI and crop yields. MethodsWe studied 18 hybrids released between 1983 and 2017 at two density treatments: current (8.5 pl m-2) and historical increasing density (from 4.6 to 8.5 pl m-2) in Iowa, USA. ResultsResults indicated that concurrent changes in hybrids and increases in plant density have increased LAI from 3.4 (in 1983) to 5.9 m2 m-2 (in 2017), with the highest LAI increases (>50%) to be realized in the middle canopy. At historical increasing in plant density treatment, the LAI increased by 1.6% year-1, but the individual plant leaf area decreased by 0.33% year-1 from 1983 to 2017. This trade-off indicates that new hybrids are more tolerant to higher plant populations than old hybrids. At current plant density treatment, the year of hybrid release did not affect LAI or individual plant leaf area. New hybrids had 5% narrower leaf area distributions, 23% higher optimum LAI values (5.2 vs 4.2 m2 m-2) and 19% higher grain yields compared to old hybrids. ConclusionsThe main reason for the increase in maize LAI in the US Corn Belt is plant density. However, an increase in LAI does not necessarily translate to higher grain yields as new hybrids had significantly higher grain yields than older hybrids at similar LAI values. Present results contribute to our understanding of maize canopy architecture and allow us to better calibrate crop models to accurately estimate LAI and grain yield.

Partitioning of Evapotranspiration and Its Response to Eco‐Environmental Factors Over an Alpine Grassland on the Qinghai–Tibetan Plateau Based on the SiB2 Model

ABSTRACTPartitioning evapotranspiration (ET) is challenging but essential for understanding the exchange of energy, water, and carbon between terrestrial ecosystems and the atmosphere. In this study, we applied the simple biosphere model (SiB2) to partition ET at a typical alpine grassland site on the Qinghai–Tibet Plateau (QTP). In addition, through process‐based model scenario experiments, we quantified the effects of four environmental factors on ET components and predicted their evolution under the two future carbon emission scenarios (ssp126 and ssp585). Our findings are summarized as follows: (1) The original version of SiB2, despite its simple structure, effectively simulates ET and its components. (2) The ratios of annual total transpiration (T), soil evaporation (Es), and canopy interception evaporation (Ei) to ET in the alpine grassland ecosystem were 51%, 43%, and 6%, respectively. (3) Each 100 mm increase in annual precipitation results in a significant increase in soil evaporation (2.77%). A 1°C increase in air temperature leads to a significant increase in vegetation transpiration (5.22%) and canopy interception evaporation (5.63%). Each 100 ppm increase in CO2 concentration causes a significant decrease in T (−5.43%) and ET (−2.97%). An increase in LAI (1 m2 m−2) has the largest effect on canopy interception evaporation (4.67%). (4) Under the high carbon emission scenario (ssp585), all ET components in this ecosystem show a significant growth trend, particularly vegetation transpiration and canopy interception evaporation. These findings will facilitate more precise predictions of the water cycle dynamics, reveal land‐atmosphere interaction mechanisms, and aid in the protection of the ecological environment of the QTP.

Practical LAI Estimation with DHP Images in Complex Forest Structure with Rugged Terrain

Leaf area index is a key structural parameter for biological and physical processes. Korea is planning to launch CAS500-4 in 2025, so in situ data is needed to validate the leaf area index. Unlike other networks (e.g., NEON and TERN), establishing an elementary sampling unit is difficult in Korea due to the complex forest structure and rugged terrain. Therefore, pixel-level correspondence between the satellite product and fisheye footprints is the best way to verify in complex terrain. In this study, we analyzed the spatial footprint of fisheye lenses in different forest types using terrestrial LiDAR data for the first time. The three-dimensional forest structure was analyzed at various viewing zenith angles, and the footprint radius was approximately 3 m at view zenith angle (VZA) 20° and approximately 10 m at VZA 90°. We also analyzed the Z-values from terrestrial laser data and the plant area index on leafless seasons to assess the impact of obstacles, such as tree trunks, under various viewing zenith angles. The analysis showed that the influence of woody components increases dramatically as the VZA exceeds 40°. Such factors influenced the increase in LAI and the decrease in the clumping index as the VZA increased. Overall, we concluded that narrowing VZA between 20° and 40° is appropriate for Korean forests with complex structures.

Use of marine minerals obtained through an innovative process with added silver for the cultivation and protection of Solanum lycopersicum

Research objective: The aim of this research was to evaluate the stimulating potential of (FertilTomix: a product based on minerals and organic molecules from the sea) obtained from an innovative extraction process and its ability to increase plant defence capabilities following the addition of silver to seeded Solanum lycopersicum plants. Materials and Methods: The experiments, which started in January 2023, were conducted in the CREA-OF greenhouses in Pescia (Pt), Tuscany, Italy (43°54′N 10°41′E) on Solanum lycopersicum cv “Siccagno”. The plants were placed in ø 24 cm pots; 30 plants per thesis, divided into 3 replicas of 10 plants each. The experimentation was divided into two parallel trials, one concerning the growth and biostimulation of tomato plants. The second experiment, instead, concerned the use of sprayed FertilTomix in the protection from pathogenic fungi (Phytophthora infestans, Leivellula taurica). On August 28, 2023, plant height (measured at 70 days after transplanting), plant nodes (measured at 70 days after transplanting), leaf area index, total dry biomass, fruit fresh weight and total fruit number have been evaluated. In addition, plants affected by diseases were counted. Results and Discussion: The experiment showed that the use of FertilTomix, irrespective of the extraction process, was able to significantly increase total plant growth, berry yield and weight, and reduce the mortality of Solanum lycopersicum plants. As found in the experiment in the treated theses, a significant increase in plant height and number of nodes per plant was noted, as well as a significant increase in total LAI. Differences were also noted between FertilTomix as such and FertilTomix enriched with silver; the former product worked better in the vegetative and root stimulation of the plants, while the product enriched with silver defended the plants better against attacks by Phytipthora infestans and Leivellula taurica. The use of this product is very interesting especially for those places where there is no water for irrigation and where fertilisers are scarce. The use of this product could obviate both problems. There are as yet no cost-effective technologies and processes in the world that can extract useful minerals from seawater for plant fertilisation and recycle the process water that can be used for irrigation. Conclusions: The test demonstrated a significant effect on plant growth after the application of certain extracts obtained from an innovative process of extracting minerals from seawater. In addition, it emerged that the product could also be used for plant protection when enriched with silver. This product would be very useful especially in countries where water resources and fertilisers are scarce, with the possibility of producing them on site through innovative facilities.

Path coefficient analysis of seed yield in Indian mustard [Brassica juncea (L.) Czern. & Coss.] under drought

The present investigation was carried out to assessthe components ofseed yield under droughtstress using pathcoefficient analysis. Twenty two genotypes ofIndian mustard were grown in a Randomized Complete Block Design with three replications during rabi, 2007-08. Analysis of variance indicated presence of variability in theexperimental genotypesforseed yield and other morpho-physiological characters except main shoot length, harvest index, protein content, SLW at 35 days aftersowing (DAS) and seed: husk ratio. Seed yield/plant was positively and significantly correlated at both phenotypic and genotypic levels with days to maturity, plant height, primary branches/plant, secondary branches/plant, siliquae on main shoot, LAI, CGR and biological yield/plant. Seed yield/plant had negative genotypic correlations of moderate strength with transpiration quotient at 35 and 75 DAS indicating its positive relationship with water use efficiency. TheRGRduring 35-75 DAS followed byRGRbetween 75 and 95 DAS exerted the highest direct positive effects on seed yield. Biological yield/plant, SLW at 75 DAS, TDM at 75 and 95 DAS, SCMR at 35 DAS, siliquae on main shoot, days to maturity and siliqua length also had substantial positive direct effects. The characters under study explained about 96.5% and 100% variability in the seed yield at phenotypic and genotypic level, respectively. Dry matter production, early growth and development of the crop are important under drought due to continuous decline in available soil moisture. Since LAI, LGR, CGR, RGR and NAR are the functions of dry matter production and/or leaf area, therefore, selection on the basis of high biological yield and large LAI at 50% flowering should be quite effective in improving seed yield under drought. An increase in LAI might increase radiation load resulting in to high transpiration. Therefore, genotypes having high LAI with erect leaves and low TQ should be accorded priority in the selection programme.

The Status of Posidonia oceanica at Tremiti Islands Marine Protected Area (Adriatic Sea).

Simple SummaryThe seagrass Posidonia oceanica is the most important marine phanerogam of the Mediterranean Sea due to its meadows’ complexity, persistence, and extension. These habitats provide a suite of ecosystem goods and services, being of primary importance in marine conservation. Despite their central role in the coastal ecology, P. oceanica meadows are undergoing overall deterioration and fragmentation in the basin mostly due to anthropogenic impacts at local to global scales. In the last decades, several management measures have been proposed aiming to improve the meadow health conditions, while the periodic monitoring of P. oceanica meadows allows for verifying their effectiveness. Here, we report the results of the monitoring of P. oceanica at Tremiti Islands Marine Protected Area (Adriatic Sea, Italy) carried out in 2003, 2015, and 2020. A general worsening was observed, particularly enhanced by direct anthropogenic impacts mostly related to anchoring practices, as well as by a certain level of sedimentation possibly deriving from coastal development. However, the identification of these impacts and the correct management of human activities to mitigate them produced positive results in a relatively short time span.Posidonia oceanica meadows are Mediterranean coastal habitats of great conservation importance. This study is focused on a meadow located at Tremiti Islands Marine Protected Area (Adriatic Sea, Italy), which was monitored in 2003, 2015, and 2020 to evaluate its health state over time in relation to coastal human activities, which have been highly affecting this MPA for the last 20 years. To assess any change in the physiognomy of the meadow, rhizome density, percentage coverage, and lower limit progressions and/or regression over time were evaluated by scuba diving, while the distribution and extension of the meadow were assessed through habitat mapping using a side-scan sonar. Moreover, phenological and lepidochronological analyses were performed on the collected rhizomes to assess the leaf area index (LAI, m2m−2) and the rhizome age (lepidochronological years). Our study showed a general deterioration of P. oceanica meadow from 2003 to 2020, with a significant reduction of its absolute and relative rhizome density and LAI at almost all sampling stations, absence of renovation of the meadow, and lower limit regression and overall worsening of the main conservation status indicators. However, appropriate management actions, such as the establishment of mooring buoy fields, supported the improvement of the P. oceanica status at the local scale with a significant increase in density and LAI and the presence of active stolonization processes, suggesting that mitigation actions can play a crucial role in the conservation of this habitat. On the contrary, local anthropogenic impacts, especially anchoring and coastal development, markedly affect the resilience of P. oceanica meadows to global stressors, such as climate change.

Improving water deficit tolerance of Salvia officinalis L. using putrescine

To study the effects of foliar application of putrescine (distilled water (0), 0.75, 1.5, and 2.25 mM) and water deficit stress (20%, 40%, 60%, and 80% available soil water depletion (ASWD)) on the physiological, biochemical, and molecular attributes of Salvia officinalis L., a factorial experiment was performed in a completely randomized design with three replications in the growth chamber. The results of Real-Time quantitative polymerase chain reaction (qRT-PCR) analysis showed that putrescine concentration, irrigation regime, and the two-way interaction between irrigation regime and putrescine concentration significantly influenced cineole synthase (CS), sabinene synthase (SS), and bornyl diphosphate synthase (BPPS) relative expression. The highest concentration of 1,8-cineole, camphor, α-thujone, β-thujone, CS, SS, and BPPS were obtained in the irrigation regime of 80% ASWD with the application of 0.75 mM putrescine. There was high correlation between expression levels of the main monoterpenes synthase and the concentration of main monoterpenes. The observed correlation between the two enzyme activities of ascorbate peroxidase (APX) and catalase (CAT) strongly suggests they have coordinated action. On the other hand, the highest peroxidase (PO) and superoxide dismutase (SOD) concentrations were obtained with the application of 0.75 mM putrescine under the irrigation regime of 40% ASWD. Putrescine showed a significant increase in LAI and RWC under water deficit stress. There was an increasing trend in endogenous putrescine when putrescine concentration was increased in all irrigation regimes. Overall, the results suggest that putrescine may act directly as a stress-protecting compound and reduced H2O2 to moderate the capacity of the antioxidative system, maintain the membrane stability, and increase secondary metabolites under water deficit stress.

Cotton growth model under drip irrigation with film mulching: A case study of Xinjiang, China

AbstractCrop growth depends on the cumulative temperature of the crop growing season, and growing degree days (GDD) is presently widely used as an index of the effective accumulated temperature. However, there are few reports on the relationship model between cotton (Gossypium hirsutum L.) growth and GDD. Based on meteorological data and published document from the Xinjiang region in the past 12 yr, we used GDD to replace days after sowing to establish a model for the growth of cotton under drip irrigation with film mulch in Xinjiang, China. In order to analyze the effects of temperature on cotton growth under the different regions and management measures, a correction coefficient method was proposed to obtain the uniform growth law. Then a standardized logistic model was used to analyze growth indices based on GDD, and the relationships between maximum leaf area index (LAImax), maximum dry‐matter accumulation (DMAmax), the harvest index (HI), and total irrigation amount are discussed. Finally, the irrigation amount during the whole growth period is used as an independent variable to predict seed‐cotton yield. The results showed that plant height and growth rate were highest when GDD increased to about 1,100 and 530 °C, respectively. The rates of increase in LAI and DMA were highest when GDD increased to about 900 and 1,000 °C, respectively. Maximum leaf area index was 4.65 and HI was near optimal when irrigation amount for the entire growing season was 500 mm. The GDD could thus improve the accuracy of yield prediction. This study provides an available method for the further establishment of a universal cotton model.

Spatial arrangement of maize plants aiming to maximize grain yield in the hybrid BRS-3046

The objectives of this study were to: (i) evaluate the effect of different spatial arrangements on morpho-physiological characteristics and (ii) determine the optimal spatial arrangement to maximize grain yield of the maize hybrid BRS-3046 grown in the Mid-North region of Brazil. We tested two row spacings (0.5 and 1 m) and five plant densities (2, 4, 6, 8, 10 plants m-2), which corresponded to 10 different plant spatial arrangements. Different morphophysiological variables, gas exchange rates and grain yield were measured. The increased planting density led to a linear increase in LAI, regardless of row spacing, while the net CO2 assimilation rate increased until the density of 4 and 6 plants m-2, under a row spacing of 0.5 and 1.0 m, respectively. On the other hand, we found a linear reduction in the stomatal conductance with increasing planting density. The intercellular CO2 concentration and the transpiration rate were higher in the widest row spacing. The instantaneous efficiency of carboxylation, in turn, showed a slight increase up to the density of six plants m-2, then falling, regardless of row spacing. Increasing plant density resulted in a linear increase in plant height and ear insertion height, regardless of row spacing. However, it had an opposite effect on stem diameter. Grain yield, in turn, increased up to 7.3 plants m-2 at a row spacing of 0.5 m and 8 plants m-2 at a row spacing of 1.0 m. This spatial arrangement was considered as ideal for achieving maximum yield

Forest floor temperature and greenness link significantly to canopy attributes in South Africa's fragmented coastal forests.

Tropical landscapes are changing rapidly due to changes in land use and land management. Being able to predict and monitor land use change impacts on species for conservation or food security concerns requires the use of habitat quality metrics, that are consistent, can be mapped using above-ground sensor data and are relevant for species performance. Here, we focus on ground surface temperature (Thermalground) and ground vegetation greenness (NDVIdown) as potentially suitable metrics of habitat quality. Both have been linked to species demography and community structure in the literature. We test whether they can be measured consistently from the ground and whether they can be up-scaled indirectly using canopy structure maps (Leaf Area Index, LAI, and Fractional vegetation cover, FCover) developed from Landsat remote sensing data. We measured Thermalground and NDVIdown across habitats differing in tree cover (natural grassland to forest edges to forests and tree plantations) in the human-modified coastal forested landscapes of Kwa-Zulua Natal, South Africa. We show that both metrics decline significantly with increasing canopy closure and leaf area, implying a potential pathway for upscaling both metrics using canopy structure maps derived using earth observation. Specifically, our findings suggest that opening forest canopies by 20% or decreasing forest canopy LAI by one unit would result in increases of Thermalground by 1.2 °C across the range of observations studied. NDVIdown appears to decline by 0.1 in response to an increase in canopy LAI by 1 unit and declines nonlinearly with canopy closure. Accounting for micro-scale variation in temperature and resources is seen as essential to improve biodiversity impact predictions. Our study suggests that mapping ground surface temperature and ground vegetation greenness utilising remotely sensed canopy cover maps could provide a useful tool for mapping habitat quality metrics that matter to species. However, this approach will be constrained by the predictive capacity of models used to map field-derived forest canopy attributes. Furthermore, sampling efforts are needed to capture spatial and temporal variation in Thermalground within and across days and seasons to validate the transferability of our findings. Finally, whilst our approach shows that surface temperature and ground vegetation greenness might be suitable habitat quality metric used in biodiversity monitoring, the next step requires that we map demographic traits of species of different threat status onto maps of these metrics in landscapes differing in disturbance and management histories. The derived understanding could then be exploited for targeted landscape restoration that benefits biodiversity conservation at the landscape scale.

Modeling soil-plant-water interaction

PurposeThe purpose of this paper is to numerically investigate the combined effects of canopy (leaf area index [LAI]) and root properties (root distribution function [Rdf] and root area index [RAI]) on a suction induced in soil-root composite under three different scenarios.Design/methodology/approachRichards equation coupled with sink term was solved using a commercial finite element package “HYDRUS” to investigate suction induced in soil-root composite.FindingsScenario 1 unveiled that soil-root composite induces 1 to 20 per cent higher suction than bare soil under the absence of transpiration. From Scenario 2, value of suction at depth of maximum RAI in case of linearly decreasing Rdf was found to be higher than that of other Rdfs. However, depth of suction influence zone (SIZ) for uniform Rdf and non-linear Rdf was found to be 10 and 11 per cent higher than that of linearly decreasing Rdf. Depth of evaporation dominant zone (EDZ) for uniformly decreasing Rdf and non-linear Rdf was found to be 1.08 to 3 times higher than that of linearly decreasing Rdf. From Scenario 3, influence of LAI on depth of SIZ is minimal. Depth of EDZ was found to decrease with the increase in LAI. Based on simple calculation on infinite slope stability, influence of variation in root and shoot properties was found to be significant on its factor of safety.Research limitations/implicationsNumerical constitutive model has limitations that it does not consider aging of plant. This model is only applicable for a particular set of soil conditions. A long-term study is required in this field to further quantify parameters for improving calibration and modeling performance.Practical implicationsFollowing are the practical implication: consideration of vegetation properties into engineered design of green infrastructure (slopes in this case) and selection of vegetation with appropriate characteristics in design for enhancement of stability of green infrastructure.Originality/valueContents of this paper are original, and they have not been submitted to any other journal.

Basal area growth, carbon isotope discrimination, and intrinsic water use efficiency after fertilization of Douglas-fir in the Oregon Coast Range

Many hectares of intensively managed Douglas-fir (Pseudotsuga menziesii Mirb. Franco) stands in western North America are fertilized with nitrogen (N) to increase growth rates, but only about ⅔ of all stands respond. Understanding the mechanisms of response facilitates prioritization of stands for treatment. The primary objective of this study was to test the hypothesis that the short-term basal area growth response to a single application of 224kgNha−1 as urea was associated with reduced stable carbon isotope discrimination (Δ13C) and increased intrinsic water use efficiency (iWUE) in a 20-yr-old plantation of Douglas-fir in the Oregon Coast Range, USA. Increment cores were measured to estimate earlywood, latewood, and total basal area increment over a time series from 1997 to 2015. Stable carbon isotope discrimination and iWUE were estimated using earlywood and latewood stable carbon isotope concentrations in tree-ring holocellulose starting seven years before fertilization in early 2009 and ending seven years after treatment. A highly significant (p<0.01) interaction effect between fertilization treatment and year was found for total basal area growth and earlywood basal area increment. Specifically, fertilized trees showed significant responses (p<0.05) in total basal area growth and earlywood basal area increment in the first (2009) and second (2010) growing seasons after fertilization in 2009. A marginally significant (p<0.10) fertilization effect was found for latewood basal area increment only in the first growing season after treatment. A significant treatment×year interaction was also found for Δ13C and iWUE in earlywood and latewood. Fertilization significantly reduced earlywood Δ13C and increased earlywood iWUE in the first and second growing seasons after fertilization. Only a marginally significant fertilization effect was detected for latewood Δ13C and iWUE in the second growing season after treatment. Previous studies of N fertilization of Douglas-fir forests have reported consistently increased growth and iWUE on low productivity sites treated with relatively high fertilization rates. This study suggested that these responses can also be observed on highly productive sites despite their lower frequency and apparently shorter duration. Other key mechanisms driving growth responses appear less important than iWUE, including an increase in LAI and shift from belowground to aboveground carbon allocation.

Interception of PAR and dry matter production in mungbean [Vigna radiata (L.) Wilczek] varieties sown under different dates

Dry matter production depends on the interception of radiation. In classical concept, the LAI is the principal growth index for determining the dry matter production as well as the yield of the crop. We hypothesized that sunlit leaf area index (L*) was a better index than the LAI for determining the dry matter production. Interception of PAR by mungbean [Vigna radiata (L.) Wilczek] varieties changes the sunlit leaf area index of the crop. This paper investigates the sunlit leaf area index (L*) and the interception of photosynthetically active radiation (PAR) by four mungbean varieties (V1-Pant Mung-5, V2-Bireswar, V3-RMG62 and V4-Sukumar) under three different dates of sowing (D1-15th February, D2-1st March and D3-15th March) and their relation with dry matter accumulation and leaf area index in the Gangetic plains of eastern India during the summer seasons of 2010 and 2011. The radiation interception increased with the age of crop and was found to be the highest when sown on 15th March. The interaction effect between interception of PAR and LAI showed that with the increase in LAI there was a corresponding increase in the interception of radiation which might have been due to the increased number and volume of leaves in the crop. 62.03 and 52.63% of the total variability were explained, respectively, by both dependent (interception of PAR) and independent sets (LAI). With L* and dry matter accumulation, it was seen that L* on 39 and 46 DAE significantly increased the dry matter production. It was also observed that L* increased when radiation was intercepted on 25 to 39 DAE. 67.58 and 79.55% of the total variability were explained, respectively, by both dependent (L*) and independent sets. It was evident that the mungbean might be sown during the first fortnight of March for better dry matter accumulation in this zone.

Water deficit stress tolerance in chickpea is mediated by the contribution of integrative defence systems in different tissues of the plant.

Drought induces heavy yield losses in chickpea (Cicer arietinum L.). Besides understanding the physiological and biochemical parameters contributing to drought tolerance, we need to understand the importance of one tissue in combatting drought stress-induced oxidative stress and influencing the antioxidative defence system in other tissues. The study was conducted to examine the influence of drought stress conditions on the antioxidative defence system and physiology in different tissues such as roots, leaves, nodules, pod walls and seeds at various vegetative and reproductive growth stages in two chickpea cultivars differing in rooting behaviour: ICC4958 (deep rooted) and ILC3279 (shallow rooted). The traits contributing to drought tolerance in ICC4958 were increased root area, decreased leaf area index or increase in root area, decreased leaf area; ILC3279 displayed a decrease in root area and an increase in LAI. The adaptation of ICC4958 was also accompanied by biochemical adjustments, like increases in antioxidative enzymes (superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione reductase and catalase) and nonenzymatic antioxidants (ascorbic acid, proline and stress-induced proteins). However, increases in antioxidant enzymes, nonenzymatic antioxidants and proteins in ILC3279 were lower than in ICC4958. The lower malondialdehyde content and membrane permeability index in ICC4958 might be responsible for reduced damage under drought stress. Increased H2O2 content in ICC4958 was related to enhanced antioxidative defence, emphasising its role as a signalling molecule under stress. This is the first study conducted on drought stress-induced enzymatic and nonenzymatic antioxidative defence systems in underground, aboveground vegetative and reproductive tissues in chickpea cultivars differing in rooting behaviour.

Enhancing Productivity of Dry-Seeded Rice (Oryza sativaL.) in North-West India Through Foliar Application of Iron and Potassium Nitrate

Low dry matter translocation towards grains in dry-seeded rice (DSR) during the postanthesis period is one of the causes of yield penalty in DSR especially in coarse textured soils as compared with puddle transplanted rice. This study was undertaken to evaluate the effects of KNO 3 and Fe foliar fertilization for enhanced productivity of DSR in coarse textured soils of north-west India during 2011 and 2012. Seven foliar application treatments [0, 1% Fe (twice), 1% Fe (thrice), 1% KNO 3 (single), 1% KNO 3 (twice), sequential spray of 1% Fe (twice) and 1% KNO 3 (single), sequential spray of Fe (twice) and KNO 3 (twice)] were used. The experiment was conducted in randomized complete block design with three replications. Grain yield in DSR varied from 4.5 to 7.0 and 6.1 to 8.2 t ha-1 during 2011 and 2012 respectively. During both the years, lowest grain yield was noticed in untreated control. Highest grain yield was found with sequential foliar application of Fe (twice) and KNO 3 (single) and this treatment showed superiority among all the treatments during both the years. Grain yield with sequential foliar application of Fe (twice) and KNO 3 (single) increased to the extent of 56 and 35% as compared to untreated control during 2011 and 2012 respectively. Foliar application resulted in an increase in LAI, root weight and volume that caused enhanced uptake of N, K and Fe. Grain number panicle-1 with sequential foliar application of Fe (twice) and KNO 3 (single) were found to increase by 46 and 26% as compared to untreated control during 2011 and 2012 respectively. It was concluded that sequential foliar application of Fe (twice) followed by KNO 3 (single) is beneficial to increase the sink size and finally grain yield in DSR.

Comparing an empirical crop model with a functional structural plant model to account for individual variability

Individual variability generally exists in crop fields. It increases with an increase in plant population density, water or nutrient deficiency, or spatio-temporal irregularity, and often results in a reduction in yield. As individual variability exists in a community but is expressed through individuals, we studied it by applying two models, one at the stand level and the other at the individual level.The crop model PILOTE and the functional structural plant model (FSPM) GreenLab were applied to a field of maize (Zea mays L.) to provide a numerical description of the crop at different levels. The delay and slower increase in LAI and in total dry matter at stand level compared to individual level, led us to hypothesize that uneven emergence could have an effect on variability. We derived a theoretical distribution of germination dates, which supported this hypothesis. In parallel, we used GreenLab to analyze possible sources of variability in accumulated biomass within a dynamic system, and to estimate possible parameters from experimental data.Using PILOTE and GreenLab, we successfully identified two typical types of individual variability in the maize field: variability in development over time and variability in competition for space during growth. Our method could be used in future research on the cause and influence of individual variability on performance, and to identify the link between an FSPM based on individual plants and a crop model at stand level.

Evaporative loss from irrigated interrows in a highly advective semi-arid agricultural area

Agricultural productivity has increased in the Texas High Plains at the cost of declining water tables, putting at risk the sustainability of the Ogallala Aquifer as a principal source of water for irrigated agriculture. This has led area producers to seek alternative practices that can increase water use efficiency (WUE) through more careful management of water. One potential way of improving WUE is by reducing soil evaporation (E), thus reducing overall evapotranspiration (ET). Before searching for ways to reduce E, it is first important to quantify E and understand the factors that determine its magnitude. The objectives of this study were (1) to quantify E throughout part of the growing season for irrigated cotton in a strongly advective semi-arid region; (2) to study the effects of LAI, days after irrigation, and measurement location within the row on the E/ET fraction; and (3) to study the ability of microlysimeter (ML) measures of E combined with sap flow gage measures of transpiration (T) to accurately estimate ET when compared with weighing lysimeter ET data and to assess the E/T ratio. The research was conducted in an irrigated cotton field at the Conservation & Production Research Laboratoryof the USDA-ARS, Bushland, TX. ET was measured by a large weighing lysimeter, and E was measured by 10 microlysimeters that were deployed in two sets of 5 across the interrow. In addition, 10 heat balance sap flow gages were used to determine T. A moderately good agreement was found between the sum E+T and ET (SE=1mm or ∼10% of ET). It was found that E may account for >50% of ET during early stages of the growing season (LAI<0.2), significantly decreasing with increase in LAI to values near 20% at peak LAI of three. Measurement location within the north-south interrows had a distinct effect on the diurnal pattern of E, with a shift in time of peak E from west to east, a pattern that was governed by the solar radiation reaching the soil surface. However, total daily E was unaffected by position in the interrow. Under wet soil conditions, wind speed and direction affected soil evaporation. Row orientation interacted with wind direction in this study such that aerodynamic resistance to E usually increased when wind direction was perpendicular to row direction; but this interaction needs further study because it appeared to be lessened under higher wind speeds.

Estimation of winter leaf area index and sky view fraction for snow modelling in boreal coniferous forests: consequences on snow mass and energy balance

AbstractLeaf area index (LAI) and canopy coverage are important parameters when modelling snow process in coniferous forests, controlling interception and transmitting radiation. Estimates of LAI and sky view factor show large variability depending on the estimation method used, and it is not clear how this is reflected in the calculated snow processes beneath the canopy. In this study, the winter LAI and sky view fraction were estimated using different optical and biomass‐based approximations in several boreal coniferous forest stands in Fennoscandia with different stand density, age and site latitude. The biomass‐based estimate of LAI derived from forest inventory data was close to the values derived from the optical measurements at most sites, suggesting that forest inventory data can be used as input to snow hydrological modelling. Heterogeneity of tree species and site fertility, as well as edge effects between different forest compartments, caused differences in the LAI estimates at some sites. A snow energy and mass balance model (SNOWPACK) was applied to detect how the differences in the estimated values of the winter LAI and sky view fraction were reflected in simulated snow processes. In the simulations, an increase in LAI and a decrease in sky view fraction changed the snow surface energy balance by decreasing shortwave radiation input and increasing longwave radiation input. Changes in LAI and sky view fraction affected directly snow accumulation through altered throughfall fraction and indirectly snowmelt through the changed surface energy balance. Changes in LAI and sky view fraction had a greater impact on mean incoming radiation beneath the canopy than on other energy fluxes. Snowmelt was affected more than snow accumulation. The effect of canopy parameters on evaporation loss from intercepted snow was comparable with the effect of variation in governing meteorological variables such as precipitation intensity and air temperature. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Long term and seasonal courses of leaf area index in a semi-arid forest plantation

Effective leaf area index (LAI e) in the semi-arid Pinus halepensis plantation, located between arid and semi-arid climatic zones at the edge of the Negev and Judean deserts, was measured bi-annually during four years (2001–2004) and more intensively (monthly) during the following two years (2004–2006) by a number of non-contact optical devices. The measurements showed a gradual increase in LAI e from ∼1 (±0.25) to ∼1.8 (±0.11) during these years. All instruments, when used properly, gave similar results that were also comparable with actual leaf area index measured by litter collection and destructive sampling and allometric estimates. Because of the constraint of clear sky conditions, which limited the use of the fisheye type sensors to times of twilight, the fisheye techniques were less useful. The tracing radiation and architecture of canopies system, which includes specific treatment of two levels of clumpiness of the sparse forest stand, was used successfully for the intensive monitoring. The mean clumpiness index, 0.61, is considered representative for the specific environment. Finally, the LAI e measurements at the start of each season were used to constrain phenology-based estimates of annual LAI e development, resulting in a continuous course of LAI e in the forest over the five-year period. Intra-seasonal LAI e variation in the order of 10% of total LAI e predicted by the model was also observed in the intensive TRAC measurements, giving confidence in the TRAC system and indicating its sensitivity and applicability in woodlands even with low LAI e values. The results can be important for forest management decision support as well as for use in evaluation of remote sensing techniques for forests at the lowest range of LAI e values.

Role of dynamic vegetation in regional climate predictions over western Africa

This study examines the role of vegetation dynamics in regional predictions of future climate change in western Africa using a dynamic vegetation model asynchronously coupled to a regional climate model. Two experiments, one for present day and one for future, are conducted with the linked regional climate-vegetation model, and the third with the regional climate model standing alone that predicts future climate based on present-day vegetation. These simulations are so designed in order to tease out the impact of structural vegetation feedback on simulated climate and hydrological processes. According to future predictions by the regional climate-vegetation model, increase in LAI is widespread, with significant shift in vegetation type. Over the Guinean Coast in 2084–2093, evergreen tree coverage decreases by 49% compared to 1984–1993, while drought deciduous tree coverage increases by 56%. Over the Sahel region in the same period, grass cover increases by 31%. Such vegetation changes are accompanied by a decrease of JJA rainfall by 2% over the Guinean Coast and an increase by 23% over the Sahel. This rather small decrease or large increase of precipitation is largely attributable to the role of vegetation feedback. Without the feedback effect from vegetation, the regional climate model would have predicted a 5% decrease of JJA rainfall in both the Guinean Coast and the Sahel as a result of the radiative and physiological effects of higher atmospheric CO2 concentration. These results demonstrate that climate- and CO2-induced changes in vegetation structure modify hydrological processes and climate at magnitudes comparable to or even higher than the radiative and physiological effects, thus evincing the importance of including vegetation feedback in future climate predictions.