scholarly journals Environmental control on water vapour and energy exchanges over grasslands in semiarid region of Brazil

2015 ◽  
Vol 19 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Patrícia S. de S. Gondim ◽  
José R. de S. Lima ◽  
Antonio C. D. Antonino ◽  
Claude Hammecker ◽  
Renan A. B. da Silva ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Water Vapour ◽  
Environmental Control ◽  
Abiotic Factors ◽  
Diurnal Variations ◽  
Energy Partitioning ◽  
Area Index ◽  
Seasonal And Diurnal Variations

A micrometeorological experiment was conducted over grasslands in a semi-arid region of north-eastern Brazil (São João, Pernambuco) from January to December 2011, using the Bowen ratio energy balance method, to improve the current understanding of energy partitioning and water vapour exchange over this ecosystem in this region. The objectives of the present study were to quantify the seasonal and diurnal variations in energy and water vapour exchanges over grasslands and understand the biotic and abiotic factors controlling the energy partitioning of this ecosystem. In the dry period, the low stored soil water limited the grass production and leaf area index, and as a consequence of these conditions, most of the annual net radiation (58%) was consumed in sensible heat flux. During the course of the study the evaporative fraction was linearly related to the leaf area index. The total annual evapotranspiration and its daily maximum were 543.8 mm and 3.14 mm d-1. The seasonal and diurnal variations in energy partitioning and evapotranspiration were controlled by soil water availability and leaf area index.

A simulation model of kenaf for assisting fibre industry planning in northern Australia. III. Model description and validation

1992 ◽  
Vol 43 (7) ◽  
pp. 1527 ◽  
Author(s):  
PS Carberry ◽  
RC Muchow
Keyword(s):  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Leaf Growth ◽  
Biomass Accumulation ◽  
Fibre Industry ◽  
Model Description ◽  
Northern Australia ◽  
Area Index ◽  
Extractable Soil

NTKENAF (Version 1.1) is a computer model which simulates the growth of kenaf (Hibiscus cannabinus L.) under rainfed conditions in tropical Australia. In daily time-steps, the model simulates the phenology, leaf area development, biomass accumulation and partitioning, soil water balance and dry matter yields of kenaf plants based on climatic and management inputs. The model assumes adequate nutrition and no effect of pests and diseases. The model uses daily maximum and minimum temperature, solar radiation and rainfall. The duration from sowing to flowering is predicted using temperature and photoperiod. Leaf growth is described as a function of node production (as determined by temperature), leaf area per node and leaf area senescence. Potential daily biomass is predicted from leaf area index, the light extinction coefficient and radiation use efficiency, and partitioned to the economic stem yield. Soil evaporation is predicted using a two-stage evaporation model, and plant transpiration is predicted from the daily biomass accumulation, a transpiration efficiency coefficient and predicted daily vapour pressure deficit. Plant extractable soil water is dependent on the available soil water range for each depth increment, the extraction front velocity, and the extent of water extraction at each depth. Daily transpiration and leaf growth are decreased below potential values once the fraction of available soil water declines below a threshold value. NTKENAF V1.1 has been validated against observed data from kenaf experiments conducted at two sites (lat. 13�48'S. and 14�28'S.) in northern Australia. The predictive accuracy of the model was good over a range in above-ground biomass up to 25 000 kg ha-1 (n = 40, r2 = 0.94, root mean square deviation = 1716 kg ha-1). Validations were also undertaken for predictions of the core and bark stem components, leaf area index and plant extractable soil water contents. The development of NTKENAF has provided a tool which can greatly aid assessment of the feasibility of a fibre industry based on kenaf in northern Australia.

Validate the DSSAT Model on Winter Wheat under Conservation Tillage Treatments in the West Henan, China

2014 ◽  
Vol 522-524 ◽  
pp. 699-708 ◽  
Author(s):  
Xiang Hui Lu ◽  
Hua Bai ◽  
Hui Ying Liu
Keyword(s):  
Water Balance ◽  
Winter Wheat ◽  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Conservation Agriculture ◽  
Soil Water Balance ◽  
The West ◽  
Area Index ◽  
Straw Mulching

Crop growth simulation models can be useful in evaluating the impacts of different tillage and residue management operations on the changes in land productivity and soil-water balance components. They offer a potentially valuable set of tools for examining questions related to performance of conservation agriculture. This can be both to improve our understanding or conceptualization of processes and to improve quantitative predictions for use by agronomists, growers, policy makers or others. We applied the new Decision Support System for Agro-technology Transfer (DSSAT) version 4.5, an improved crop growth simulation model, to three conservation agriculture treatments and one conventional tillage treatment data from a field-scale study in west Henan region of China to predict winter-wheat yield, leaf area index and soil-water balance. The sites average annual precipitation is 632mm and it had a winter wheat-fallow-winter wheat rotation. There winter wheat planting in October and harvesting in next year June. The model was calibrated using 2005-2006 winter-wheat crop data from field experiments of the four treatments. The treatments were: (1) decreased tillage (DT): mulching of 10-15cm height straw and one ploughing operation to 25cm depth on July 1st; (2) zero tillage (ZT): zero tillage with 35-40cm height straw mulching; (3) subsoiling (SS): 35-40cm height straw mulching and subsoil to 40cm depth on July 1st; (4) conventional tillage (CT): 10-15cm height straw mulching and two ploughing operations 20cm deep on July 1st and October 1st. The DSSAT satisfactorily simulated the four treatments variations in winter-wheat yield, leaf area index and soil-water balance. There was better agreement between observed and predicted yields (the error absolute values were less than 3.95% and the error mean absolute values were less than 2.78%). The mean value of root mean square errors (RMSE) for simulated leaf area index (LAI) and soil water storage were 0.41cm2·cm-2 and 0.08cm3·cm-3 for DT, ZT, SS and CT, treatment respectively. The predicted water use efficiency for the four treatments were 15.85, 15.40, 16.58 and 15.81kg·mm-1·ha-1, respectively. These values were close to the values calculated from field measured data (16.82, 14.44, 16.86 and 15.66kg·mm-1·ha-1, respectively). Although the analysis results show us that the DSSAT V4.5 is well suited for simulating winter-wheat growth in the West Henan region of China, these results are preliminary and based on only one year of experimental data and four treatments and further long-term analyses need to be carried out for improving the understanding of the conservation agriculture cropping systems in the west Henan region of China.

scholarly journals DIEBACK, LEAF AREA INDEX AND YIELD OF YOUNG EUCALYPT CLONES PLANTATION IN THE BRAZILIAN SAVANNAH REGION

2018 ◽  
Vol 41 (3) ◽  
Author(s):  
Geraldo Gonçalves dos Reis ◽  
Frederico de Freitas Alves ◽  
Maria das Graças Ferreira Reis ◽  
Felippe Coelho de Souza ◽  
Diogo Sena Baiero ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Water Deficit ◽  
Tree Height ◽  
Low Fertility ◽  
Limiting Factor ◽  
Soil Water Deficit ◽  
Area Index ◽  
Brazilian Savannah

ABSTRACT Eucalypt has been widely planted in Brazil, in the savannah region, which is characterized by high soil water deficit and low fertility. Dieback, leaf area index (LAI) and yield of young stands of 16 eucalypt clones were studied in Vazante, MG, Brazil (17º36’09"S and 46º 42’02"W). It was determined for each clone: a) the proportion of the tree height with dieback symptoms in the apical terminal (HWD%) and the proportion of trees with dieback (NWD%), at 13 months (end of the first dry season); b) the LAI at 13 and 21 months, and c) the yield at the age of 13, 19 and 25 months. HWD% reached 5-9%, and NWD%, 50-80%, for the five most susceptible clones, when the soil water deficit reached 508 mm in the year. LAI varied from 0.61 to 1.56, at 13 months, and from 2.31 to 3.48 at 21 months, presenting inverse relationship with dieback. The least susceptible clones to dieback achieved the highest yield up to 25 months of age. There was interaction between dieback and fertilizer levels only for three clones. There was a positive correlation (p < 0.001) between the LAI at the age of 13 months and the periodic monthly increment from 0 to 11 months, and from 11 to 19 months. The difference in dieback susceptibility among clones allows the selection of genotypes for regions where the soil water deficit is a major limiting factor.

scholarly journals Rule-based analysis of throughfall kinetic energy to evaluate biotic and abiotic factor thresholds to mitigate erosive power

2016 ◽  
Vol 40 (3) ◽  
pp. 431-449 ◽  
Author(s):  
Philipp Goebes ◽  
Karsten Schmidt ◽  
Werner Härdtle ◽  
Steffen Seitz ◽  
Felix Stumpf ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Kinetic Energy ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Abiotic Factors ◽  
Tree Height ◽  
Abiotic Factor ◽  
Area Index ◽  
Biotic And Abiotic Factors ◽  
Optimal Set

Below vegetation, throughfall kinetic energy (TKE) is an important factor to express the potential of rainfall to detach soil particles and thus for predicting soil erosion rates. TKE is affected by many biotic (e.g. tree height, leaf area index) and abiotic (e.g. throughfall amount) factors because of changes in rain drop size and velocity. However, studies modelling TKE with a high number of those factors are lacking. This study presents a new approach to model TKE. We used 20 biotic and abiotic factors to evaluate thresholds of those factors that can mitigate TKE and thus decrease soil erosion. Using these thresholds, an optimal set of biotic and abiotic factors was identified to minimize TKE. The model approach combined recursive feature elimination, random forest (RF) variable importance and classification and regression trees (CARTs). TKE was determined using 1405 splash cup measurements during five rainfall events in a subtropical Chinese tree plantation with five-year-old trees in 2013. Our results showed that leaf area, tree height, leaf area index and crown area are the most prominent vegetation traits to model TKE. To reduce TKE, the optimal set of biotic and abiotic factors was a leaf area lower than 6700 mm2, a tree height lower than 290 cm combined with a crown base height lower than 60 cm, a leaf area index smaller than 1, more than 47 branches per tree and using single tree species neighbourhoods. Rainfall characteristics, such as amount and duration, further classified high or low TKE. These findings are important for the establishment of forest plantations that aim to minimize soil erosion in young succession stages using TKE modelling.

Modelling Site Productivity of Eucalyptus globulus in Response to Climatic and Site Factors

1997 ◽  
Vol 24 (6) ◽  
pp. 831 ◽  
Author(s):  
Michael Battaglia ◽  
Peter Sands
Keyword(s):  
Water Use Efficiency ◽  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Water Use ◽  
Eucalyptus Globulus ◽  
Area Index ◽  
Site Fertility ◽  
Closed Canopy ◽  
Use Efficiency

A simple model, PROMOD, predicts the growth of a forest following canopy closure, i.e. under conditions in which the foliage biomass has attained a steady state. The principal output from PROMOD is peak mean annual increment. However, additional output available includes the closed-canopy leaf area index, evapotranspiration and water use efficiency. In addition, an indication of biomass partitioning around the time of peak MAI and the relative effects different environmental factors play in limiting production can be obtained. PROMOD is based on a generalisation of a simple forest growth model which predicts biomass production and partitioning at the stand level with a daily or annual time step. The minimum level of inputs required by PROMOD are of a quality and quantity that forest managers can readily and cheaply obtain for screening prospective plantation sites: the latitude, longitude, altitude, slope and aspect of the site and a classification of the soil depth, texture, stoniness, drainage and a rating of site fertility. However, PROMOD can be run using daily inputs of weather data and hence predict the seasonal variation of production. The closed-canopy leaf area index is calculated from the mean annual rainfall and temperature at the site, and a simple rating of site fertility. Annual production is calculated as the sum of daily production and takes diurnal temperature variation and possible seasonal photosynthetic acclimation into account. A simple soil water balance model is included in which water use is based on a crop factor which is a function of soil water content and a water use efficiency which is a function of vapour pressure deficit. The model was developed on the basis of data from nine plots of Eucalyptus globulus in south-eastern Tasmania and in Western Australia, and was validated using data from 19 plots in northern Tasmania.

Evaporative Flux from Irrigated Cotton as Related to Leaf Area Index, Soil Water, and Evaporative Demand 1

1978 ◽  
Vol 70 (6) ◽  
pp. 912-917 ◽  
Author(s):  
S. Al‐Khafaf ◽  
P. J. Wierenga ◽  
B. C. Williams
Keyword(s):  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Evaporative Demand ◽  
Area Index ◽  
Evaporative Flux

scholarly journals Assimilation of Leaf Area Index and Soil Water Index from Satellite Observations in a Land Surface Model in Hungary

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 944
Author(s):  
Helga Tóth ◽  
Balázs Szintai
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Leaf Area Index ◽  
Soil Water ◽  
Leaf Area ◽  
Weather Prediction ◽  
Regional Scale ◽  
Surface Model ◽  
Area Index ◽  
Water Index

In this study, a Land Data Assimilation System (LDAS) is applied over the Carpathian Basin at the Hungarian Meteorological Service to monitor the above-ground biomass, surface fluxes (carbon and water), and the associated root-zone soil moisture at the regional scale (spatial resolution of 8 km × 8 km) in quasi-real-time. In this system the SURFEX model is used, which applies the vegetation growth version of the Interactions between Soil, Biosphere and Atmosphere (ISBA-A-gs) photosynthesis scheme to describe the evolution of vegetation. SURFEX is forced using the outputs of the ALADIN numerical weather prediction model run operationally at the Hungarian Meteorological Service. First, SURFEX is run in an open-loop (i.e., no assimilation) mode for the period 2008–2015. Secondly, the Extended Kalman Filter (EKF) method is used to assimilate Leaf Area Index (LAI) Spot/Vegetation (until May 2014) and PROBA-V (from June 2014) and Soil Water Index (SWI) ASCAT/Metop satellite measurements. The benefit of LDAS is proved over the whole country and to a selected site in West Hungary (Hegyhátsál). It is demonstrated that the EKF can provide useful information both in wet and dry seasons as well. It is shown that the data assimilation is efficient to describe the inter-annual variability of biomass and soil moisture values. The vegetation development and the water and carbon fluxes vary from season to season and LDAS is a capable tool to monitor the variability of these parameters.

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