scholarly journals Simultaneous measurements of CO<sub>2</sub> and water exchanges over three agroecosystems in South-West France

2009 ◽  
Vol 6 (1) ◽  
pp. 2489-2522 ◽  
Author(s):  
P. Stella ◽  
E. Lamaud ◽  
Y. Brunet ◽  
J.-M. Bonnefond ◽  
D. Loustau ◽  
...  
Keyword(s):  
Carbon Sink ◽  
Vapour Pressure Deficit ◽  
Weather Conditions ◽  
Pine Forest ◽  
Stand Age ◽  
Agricultural Field ◽  
Maize Crop ◽  
Simultaneous Measurements ◽  
South West ◽  
Young Forest

Abstract. During the last few decades, many studies have been performed to determine water and carbon budgets of broadleaf and deciduous forests, crops and grasslands. However, since most measurements have been made in different regions and at different periods, it is difficult to compare the results directly. In order to evaluate accurately the respective contribution of various agroecosystems to global water and carbon exchanges, it is necessary to compare data obtained in similar climatic and weather conditions. To address this question, we present the results from simultaneous measurements carried out from 31 March 2007 to 3 March 2008 over three typical agroecosystems of the Les Landes region in South-West France: an agricultural field with maize from 29 May to 18 October, a young (5 year-old) pine forest and a mature (37 year-old) pine forest. All measurements were collected as part of the Regional Experiment component of the CarboEurope-IP project. During most of the year, the agricultural field without vegetation is a source of CO2, but from late June to early September the maize crop becomes a stronger carbon sink than the forests. Over the whole measurement period the three agroecosystems behave as CO2 sinks with carbon storage of about 500, 330 and 230 gC m−2 for the young forest, the mature forest and the agricultural field, respectively. Daily Water Use Efficiencies (WUE) of the three ecosystems were evaluated and expressed as functions of the mean daily vapour pressure deficit (VPD). Similar trends were observed for the two forests, which suggests that for a given species WUE is independent of stand age. The WUE of the maize crop at maturity was also found to depend upon VPD, but it is about twice as large as for the forests, owing to the physiological advantages of C4 species.

scholarly journals Simultaneous measurements of CO<sub>2</sub> and water exchanges over three agroecosystems in South-West France

2009 ◽  
Vol 6 (12) ◽  
pp. 2957-2971 ◽  
Author(s):  
P. Stella ◽  
E. Lamaud ◽  
Y. Brunet ◽  
J.-M. Bonnefond ◽  
D. Loustau ◽  
...  
Keyword(s):  
Vapour Pressure ◽  
Gross Primary Production ◽  
Vapour Pressure Deficit ◽  
Pine Forest ◽  
Photon Flux ◽  
Stand Age ◽  
Agricultural Field ◽  
Maize Crop ◽  
Simultaneous Measurements ◽  
South West

Abstract. During the last few decades, many studies have been performed to determine water and carbon budgets of broadleaf and deciduous forests, crops and grasslands. However, since most measurements have been made in different regions and at different periods, it is difficult to compare the results directly. In order to evaluate accurately the respective contribution of various agroecosystems to global water and carbon exchanges, it is necessary to compare data obtained in similar climatic and weather conditions. To address this question, we present the results from simultaneous measurements carried out during one year over three typical agroecosystems of the Les Landes region in South-West France:~an agricultural field with maize from 29 May to 18 October, a young (5 year-old) pine forest and a mature (37 year-old) pine forest. All measurements were collected as part of the Regional Experiment component of the CarboEurope-IP project. During most of the year, the agricultural field without vegetation is a source of CO2, but from late June to early September the maize crop becomes a stronger carbon sink than the forests. Over the whole measurement period the three agroecosystems behave as CO2 sinks with carbon storage of about 335, 210 and 160 g C m−2 for the young forest, the mature forest and the agricultural field, respectively. We investigated the influence of climatic conditions on Gross Primary Production (GPP) of the three ecosystems and observed a predominant role of vapour pressure deficit (VPD) for forests and of photosynthetic photon flux density (FPP) for maize. Daily Water Use Efficiencies (WUE) of the three ecosystems were evaluated and expressed as functions of the mean daily vapour pressure deficit (VPD). Similar trends were observed for the two forests, which suggests that for a given species WUE is independent of stand age. The WUE of the maize crop at maturity was also found to depend upon VPD, but it is about twice as large as for the forests, owing to the physiological advantages of C4 species.

The CO2 balance of a boreal fen is more sensitive to drought than surrounding forests

2020 ◽  
Author(s):  
Mats Nilsson ◽  
Joshua Ratcliffe ◽  
Anne Klosterhalfen ◽  
Peng Zhao ◽  
Jinchu Chi ◽  
...  
Keyword(s):  
Boreal Forests ◽  
Vapour Pressure Deficit ◽  
Weather Conditions ◽  
Pine Forest ◽  
Extreme Weather Events ◽  
Boreal Peatlands ◽  
Weather Events ◽  
Co2 Balance ◽  
First Time ◽  
Boreal Landscape

&lt;p&gt;The boreal zone is one of the most carbon-dense biomes in the world and is comprised of a highly interconnected mosaic of forest and wetlands which are warming at a rate several times the global average with extreme weather events, such as droughts, becoming increasingly common. At the ecosystem scale, both forests and peatlands are often vulnerable to drought-induced carbon loss, however, the relative resilience of these two ecosystems within the boreal landscape is not well understood. Here we study the effect of the 2018 drought on CO&lt;sub&gt;2&lt;/sub&gt; fluxes in two boreal forests and a boreal peatland within &lt;20km radius, i.e. experiencing the same weather conditions. The peatland displayed the strongest response to the drought, with the site becoming a net annual source for CO&lt;sub&gt;2&lt;/sub&gt; for the first time in 17 years, with the CO&lt;sub&gt;2 &lt;/sub&gt;sink slow to recover after the drought broke. In contrast, the response of the forests was mixed, a&amp;#160; spruce/pine forest on glacial till remained unaffected by the drought, whereas a nearby pine forest, situated on drier sandy soil, responded strongly to vapour pressure deficit and declining soil moisture content, decreasing with CO&lt;sub&gt;2&lt;/sub&gt; uptake weakening, but still allowing the forest to function as a CO&lt;sub&gt;2&lt;/sub&gt; sink. In contrast to the bog, the pine forest CO&lt;sub&gt;2&lt;/sub&gt; sink quickly recovered following the end of the drought. We conclude that boreal peatlands are likely to be the most vulnerable component of the boreal landscape to drought and that soil type is likely to play a role in regulating the response of boreal forests.&lt;/p&gt;

scholarly journals Long-term energy and CO<sub>2</sub> flux observations over an agricultural field in southeastern Tibetan Plateau

2020 ◽  
Author(s):  
Anlun Xu ◽  
Jian Li
Keyword(s):  
Heat Flux ◽  
Tibetan Plateau ◽  
Seasonal Variations ◽  
Carbon Sink ◽  
Dominant Role ◽  
Sensible Heat Flux ◽  
Vapour Pressure Deficit ◽  
Co2 Flux ◽  
Agricultural Field ◽  
Southeastern Tibetan Plateau

Abstract. Information on the exchange of energy, momentum and mass (H2O, CO2, CH4, etc.) over complex topography is critical for determining the development of the boundary layer, carbon and water cycles, weather and climate. This information can also improve the numerical modelling of physical atmosphere-land processes. Based on a 12-year (2007–2018) eddy covariance dataset over the Dali agricultural field in the southeastern Tibetan Plateau, we analysed the diurnal, seasonal and inter-annual changes in sensible heat flux (Hs), latent heat flux (LE) and CO2 flux (Fc) and their meteorological controls on multiple timescales (half-hourly, daily, monthly, and yearly). The results show that both Hs and LE have similar diurnal and seasonal variations, but the amplitude of LE is obviously larger than that of Hs throughout the year, which indicates that the LE plays a dominant role in surface heat exchange. The Fc has a noticeable diurnal cycle, reaching its minimum around noon, and clear seasonal variations, reaching its minimum in the summer. The annual average Hs increased from approximately 6 W m−2 during 2007–2012 to 19 W m−2 during 2013–2018, while the LE decreased from approximately 110 W m−2 during 2007–2013 to 79 W m−2 during 2014–2018. The Dali observational area is a carbon sink in all years, while the magnitude of net uptake decreases significantly from approximately 739 g C m−2 yr−1 during 2007–2013 to 218 g C m−2 yr−1 during 2014–2018. The results also show that wind speed (WS) is the major control of Hs, while the product of WS and vapour pressure deficit (VPD) is the main driver of LE on different timescales. The net radiation (Rn) and soil temperature (Ts) have the largest effects on Fc from the daily to monthly timescales, while the WS has the largest impact on annual total Fc.

scholarly journals Sensing Technology Survey for Obstacle Detection in Vegetation

2021 ◽  
Vol 1 (3) ◽  
pp. 672-685
Author(s):  
Shreya Lohar ◽  
Lei Zhu ◽  
Stanley Young ◽  
Peter Graf ◽  
Michael Blanton
Keyword(s):  
Autonomous Vehicles ◽  
Weather Conditions ◽  
Climatic Conditions ◽  
Obstacle Detection ◽  
Agricultural Field ◽  
Thermal Camera ◽  
Agricultural Vehicles ◽  
Sensing Systems ◽  
Sensing Technology ◽  
Hyperspectral Sensing

This study reviews obstacle detection technologies in vegetation for autonomous vehicles or robots. Autonomous vehicles used in agriculture and as lawn mowers face many environmental obstacles that are difficult to recognize for the vehicle sensor. This review provides information on choosing appropriate sensors to detect obstacles through vegetation, based on experiments carried out in different agricultural fields. The experimental setup from the literature consists of sensors placed in front of obstacles, including a thermal camera; red, green, blue (RGB) camera; 360° camera; light detection and ranging (LiDAR); and radar. These sensors were used either in combination or single-handedly on agricultural vehicles to detect objects hidden inside the agricultural field. The thermal camera successfully detected hidden objects, such as barrels, human mannequins, and humans, as did LiDAR in one experiment. The RGB camera and stereo camera were less efficient at detecting hidden objects compared with protruding objects. Radar detects hidden objects easily but lacks resolution. Hyperspectral sensing systems can identify and classify objects, but they consume a lot of storage. To obtain clearer and more robust data of hidden objects in vegetation and extreme weather conditions, further experiments should be performed for various climatic conditions combining active and passive sensors.

scholarly journals Dry matter production and nitrogen utilization in cropping systems with grass, lucerne and maize. 2. Nitrogen yield and utilization.

1986 ◽  
Vol 34 (1) ◽  
pp. 37-47
Author(s):  
J.H.J. Spiertz ◽  
L. Sibma
Keyword(s):  
Cropping Systems ◽  
Mineral Soil ◽  
Weather Conditions ◽  
N Fertilization ◽  
N Fixation ◽  
Maize Crop ◽  
After Effects ◽  
Matter Production ◽  
After Effect ◽  
Use Efficiency

The N yield and the N use efficiency were studied in a 3-year experiment with various cropping systems of Lolium perenne, Medicago sativa and maize. N yields of L. perenne and maize were about 450 and 200 kg/ha, resp. N yields of M. sativa ranged from about 400 to 600 kg/ha depending on crop age and weather conditions. N fixation rates of M. sativa were assessed in 1982 and ranged from 107 to 507 kg/ha for high (450 kg N/ha) and no N fertilization, resp. The after-effects of 1-, 2- and 3-year crops of L. perenne, M. sativa and maize on the DM and N yields of a test crop of maize were measured. Depending on the age of the preceding L. perenne crop, annually supplied with 450 kg N/ha, the N after-effects ranged from 120 to 175 kg/ha. The after-effect of a previous cropping with M. sativa was independent of the N dressing and ranged from 140 to 175 kg/ha. For comparison, the after-effect of a preceding maize crop ranged from 90 to 110 kg/ha. Mineral soil N reserves were determined in spring and autumn. (Abstract retrieved from CAB Abstracts by CABI’s permission)

scholarly journals Effective Weed Control in Maize

2011 ◽  
Vol 68 (1) ◽  
Author(s):  
Ileana BOGDAN ◽  
Teodor RUSU ◽  
Ştefania GADEA ◽  
Ilarie IVAN ◽  
Paula MORARU ◽  
...  
Keyword(s):  
Weed Control ◽  
Control Method ◽  
Weather Conditions ◽  
Vegetation Period ◽  
Control Methods ◽  
Maize Crop ◽  
Optimal Network ◽  
Weed Seeds ◽  
Weeds Control

The paper present the results of 26 variants of weed control in maize (grouped in 6 distinctly strategies) which were tested in 2010 agricultural year in a one factorial stationary experiment. Three of the strategies were based on post emergence weed control methods, two of them – on pre-emergent weed control method and one of them – based on both methods. The main goal was establishing an optimal network weeds control in maize crop. Maize weed in Luduş area increased, due to weed seeds reserve in the arable stratum and weather conditions, which allow weeds to grow alternatively, and because of the development of problem-causing species during the maize vegetation period, when no tilling is performed.

scholarly journals Modelling short-term variability in carbon and water exchange in a temperate Scots pine forest

2015 ◽  
Vol 6 (2) ◽  
pp. 485-503 ◽  
Author(s):  
M. H. Vermeulen ◽  
B. J. Kruijt ◽  
T. Hickler ◽  
P. Kabat
Keyword(s):  
Water Uptake ◽  
Scots Pine ◽  
Water Exchange ◽  
Carbon Sink ◽  
Pine Forest ◽  
Temperature Threshold ◽  
Water Fluxes ◽  
Local Data ◽  
Deep Soil ◽  
Scots Pine Forest

Abstract. The vegetation–atmosphere carbon and water exchange at one particular site can strongly vary from year to year, and understanding this interannual variability in carbon and water exchange (IAVcw) is a critical factor in projecting future ecosystem changes. However, the mechanisms driving this IAVcw are not well understood. We used data on carbon and water fluxes from a multi-year eddy covariance study (1997–2009) in a Dutch Scots pine forest and forced a process-based ecosystem model (Lund–Potsdam–Jena General Ecosystem Simulator; LPJ-GUESS) with local data to, firstly, test whether the model can explain IAVcw and seasonal carbon and water exchange from direct environmental factors only. Initial model runs showed low correlations with estimated annual gross primary productivity (GPP) and annual actual evapotranspiration (AET), while monthly and daily fluxes showed high correlations. The model underestimated GPP and AET during winter and drought events. Secondly, we adapted the temperature inhibition function of photosynthesis to account for the observation that at this particular site, trees continue to assimilate at very low atmospheric temperatures (up to daily averages of −10 °C), resulting in a net carbon sink in winter. While we were able to improve daily and monthly simulations during winter by lowering the modelled minimum temperature threshold for photosynthesis, this did not increase explained IAVcw at the site. Thirdly, we implemented three alternative hypotheses concerning water uptake by plants in order to test which one best corresponds with the data. In particular, we analyse the effects during the 2003 heatwave. These simulations revealed a strong sensitivity of the modelled fluxes during dry and warm conditions, but no single formulation was consistently superior in reproducing the data for all timescales and the overall model–data match for IAVcw could not be improved. Most probably access to deep soil water leads to higher AET and GPP simulated during the heatwave of 2003. We conclude that photosynthesis at lower temperatures than assumed in most models can be important for winter carbon and water fluxes in pine forests. Furthermore, details of the model representations of water uptake, which are often overlooked, need further attention, and deep water access should be treated explicitly.

scholarly journals Net Ecosystem Exchange of CO2 in Deciduous Pine Forest of Lower Western Himalaya, India

Resources ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 98 ◽  
Author(s):  
Nilendu Singh ◽  
Bikash Ranjan Parida ◽  
Joyeeta Singh Charakborty ◽  
N.R. Patel
Keyword(s):  
Carbon Cycle ◽  
Carbon Balance ◽  
Net Primary Productivity ◽  
Carbon Sink ◽  
Net Ecosystem Exchange ◽  
Western Himalaya ◽  
Pine Forest ◽  
Environmental Controls ◽  
Carbon Release ◽  
The Himalaya

Carbon cycle studies over the climate-sensitive Himalayan regions are relatively understudied and to address this gap, systematic measurements on carbon balance components were performed over a deciduous pine forest with an understory layer. We determined annual net carbon balance, seasonality in components of carbon balance, and their environmental controls. Results indicated a strong seasonality in the behavior of carbon exchange components. Net primary productivity (NPP) of pine forest exceeded soil respiration during the growing phase. Consequently, net ecosystem exchange exhibited a net carbon uptake. In the initial phase of the growing season, daily mean uptake was −3.93 (±0.50) g C m−2 day−1, which maximizes (−8.47 ± 2.3) later during post-monsoon. However, a brief phase of carbon release was observed during peak monsoon (August) owing to an overcast condition. Nevertheless, annually the forest remained as a carbon sink. The understory is extensively distributed and it turned out to be a key component of carbon balance because of sustained NPP during the pine leafless period. Temperature and evaporative fraction exhibited a prime control over the seasonal carbon dynamics. Our observations could lend certain useful insights into the application of coupled climate-carbon cycle models for the Himalaya and ecological functions in the region.

Effects of surface manure application timing on ammonia volatilization

2001 ◽  
Vol 81 (4) ◽  
pp. 525-533 ◽  
Author(s):  
R. Gordon ◽  
R. Jamieson ◽  
V. Rodd ◽  
G. Patterson ◽  
T. Harz
Keyword(s):  
Ammonia Volatilization ◽  
Meteorological Parameters ◽  
Vapour Pressure Deficit ◽  
Weather Conditions ◽  
Field Trials ◽  
Dairy Manure ◽  
Manure Application ◽  
Application Timing ◽  
Total Percentage ◽  
Linear Correlations

The purpose of this study was to evaluate the influence of timing of application on ammonia (NH3) volatilization from surface-applied dairy manure. Field trials were conducted over a 2-yr period (1994 and 1995) at the Agriculture and Agri-Food Canada Research Farm in Nappan, Nova Scotia. A total of eight trials were performed in an attempt to characterize what effect the timing of application (morning vs. late afternoon/early evening) has on NH3 volatilization losses. Ammonia losses were also related to several meteorological parameters. The total percentage of NH3 volatilized in the 10 h following field spreading ranged from as low as < 2% to approximately 66%. Late-day spreading typically resulted in at least a 30% reduction in overall NH3 flux densities, primarily due to substantial reductions in NH3 losses occurring within the first 10 h after manure application. The positive benefits of late-day manure spreading were more pronounced during warm, dry weather conditions. Significant (P < 0.05) positive linear correlations were observed between NH3 volatilization in the 10 h following spreading and solar radiation (r2 = 0.56), wind speed (r2 = 0.53), temperature (r2 = 0.34) and vapour pressure deficit (r2 = 0.53). Results from this study have indicated that late day manure spreading practices can substantially reduce NH3 volatilization. Key words: Slurry, ammonia volatilization, dairy, manure application, timing

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