Effect of land use on carbon dioxide, water vapour and energy exchange over terrestrial ecosystems in Southwestern France during the CERES campaign

Abstract. Eddy fluxes were measured over different ecosystems, winter and summer crops, a maritime pine forest at different stages of development and grassland, from 17 May to 26 June 2005 in the southwestern region of France. During the experiment, summer crops started growing whereas winter crops and grassland achieved their senescence. Comparatively, the other ecosystems had a much slower growth emphasized by soil water deficit at forest sites. The ten ecosystems showed different partitioning of available energy. Net radiation was the highest above the maritime pine forest, followed, in decreasing order, by the crops, the vineyard and the grassland. Over the whole campaign period, the Bowen ratio (β=H/LE) was larger above the forest sites than for the other sites. The various vegetation types also showed contrasting net ecosystem exchange (NEE) dynamics following their growth status and respective behaviour in response to drought. Both the clearcut and summer crops before irrigation and plant growth behaved as sources of CO2, whereas the vineyard, the mature forest and winter crops acted as sinks. However the maize crops became substantial sinks of CO2 after the start of irrigation and canopy growth, with fluxes twice as large as for the mature pine forest. Finally, throughout the experiment, forest, grassland and crops sequestrated from about 50 gC m−2 to 230 gC m−2, while the cleacut and the beans crop rejected about 30 gC m−2. These results support the idea that converting a mature forest to a clearcut or bare soil available to agricultural use enhances the sensible heat flux and shifts the ecosystem from a sink to a source of carbon.

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Seasonal and inter annual variability of energy exchange above a boreal Scots pine forest

Biogeosciences Discussions ◽

10.5194/bgd-7-6441-2010 ◽

2010 ◽

Vol 7 (4) ◽

pp. 6441-6494 ◽

Cited By ~ 6

Author(s):

S. Launiainen

Keyword(s):

Heat Flux ◽

Scots Pine ◽

Seasonal Cycle ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Pine Forest ◽

Surface Conductance ◽

Sensible Heat ◽

Annual Variability ◽

Scots Pine Forest

Abstract. Twelve-years of eddy-covariance measurements conducted above a boreal Scots pine forest in Hyytiälä, Southern Finland, were analyzed to assess the seasonal and inter-annual variability of surface conductance (gs) and energy partitioning. The gs had distinct annual course, driven by the seasonal cycle of the Scots pine. Low gs (2–3 mm s−1 in April) restricted transpiration in springtime and caused the sensible heat flux to peak in May–June while evapotranspiration takes over later in July–August when gs is typically 5–7 mm s−1. Hence, during normal years Bowen ratio decreases from 4–6 in April to 0.7–0.9 in August. Sensitivity of gs to ambient vapor pressure deficit (D) was relatively constant but the reference value at D=1 kPa varied seasonally and between years. Only two drought episodes when volumetric soil moisture content in upper mineral soil decreased below 0.15 m3 m−3 occurred during the period. Below this threshold value transpiration was strongly reduced, which promoted sensible heat exchange increasing Bowen ratio to 3–4. Annual evapotranspiration varied between 218 and 361 mm and accounted between 50% and 90% of equilibrium evaporation. The forest floor contributed between 16 and 25% of the total evapotranspiration on annual scale. The fraction stayed similar over the observed range of environmental conditions including drought. The inter-annual variability of evapotranspiration could not be linked to any mean climate parameter while the summertime sensible heat flux and net radiation were well explained by global radiation. The energy balance closure varied annually between 0.66 and 0.95 and had a distinct seasonal cycle with worse closure in spring when large proportion of available energy is partitioned into sensible heat.

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Seasonal and inter-annual variability of energy exchange above a boreal Scots pine forest

Biogeosciences ◽

10.5194/bg-7-3921-2010 ◽

2010 ◽

Vol 7 (12) ◽

pp. 3921-3940 ◽

Cited By ~ 36

Author(s):

S. Launiainen

Keyword(s):

Heat Flux ◽

Scots Pine ◽

Seasonal Cycle ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Pine Forest ◽

Surface Conductance ◽

Sensible Heat ◽

Annual Variability ◽

Scots Pine Forest

Abstract. Twelve-years of eddy-covariance measurements conducted above a boreal Scots pine forest in Hyytiälä, Southern Finland, were analyzed to assess the seasonal and inter-annual variability of surface conductance (gs) and energy partitioning. The gs had distinct annual course, driven by the seasonal cycle of the Scots pine. Low gs (2–3 mm s−1 in April) cause the sensible heat flux to peak in May–June while evapotranspiration takes over later in July–August when gs is typically 5–7 mm s−1. Hence, during normal years Bowen ratio decreases from 4–6 in April to 0.7–0.9 in August. Sensitivity of gs to ambient vapor pressure deficit (D) was relatively constant but the reference value at D = 1 kPa varied seasonally and between years. Only two drought episodes when volumetric soil moisture content in upper mineral soil decreased below 0.15 m3 m−3 occurred during the period. Below this threshold value, transpiration was strongly reduced, which promoted sensible heat exchange increasing Bowen ratio to 3–4. Annual evapotranspiration varied between 218 and 361 mm and accounted between 50% and 90% of equilibrium evaporation. The forest floor contributed between 16 and 25% of the total evapotranspiration on annual scale. The fraction stayed similar over the observed range of environmental conditions including drought periods. The inter-annual variability of evapotranspiration could not be linked to any mean climate variable while the summertime sensible heat flux and net radiation were well explained by global radiation. The energy balance closure varied annually between 0.66 and 0.95 and had a distinct seasonal cycle with worse closure in spring when a large proportion of available energy is partitioned into sensible heat.

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Comparison of actual evapotranspiration based on lysimeter, scintillometer and bowen ratio energy balance method

10.5194/egusphere-egu2020-11054 ◽

2020 ◽

Author(s):

Veronika Forstner ◽

Matevž Vremec ◽

Matěj Orság ◽

Gabriela Pozníková ◽

Steffen Birk ◽

...

Keyword(s):

Energy Balance ◽

Land Surface ◽

Near Infrared ◽

Agricultural Research ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Vegetation Period ◽

The Other ◽

Actual Evapotranspiration ◽

Ratio Energy

Evapotranspiration is an important parameter for grassland ecosystems because the (actual) evapotranspiration explains the exchange of water and energy between soil, land surface and atmosphere. Understanding the effects of changing grassland yields on evapotranspiration rates is essential for the assessment of the water- and plant water balance of grassland sites under climate change. However, evapotranspiration is difficult to measure, and the suitability of the various methods strongly depends on the time and spatial scale considered. Thus, the aim of this work is to compare different measurements of actual evapotranspiration (ETa) at a managed alpine grassland site. The study area is located in the northern alps of Austria, at the Agricultural Research and Education Centre Raumberg-Gumpenstein (Styria). Here, the ETa data of a high resolution weighable lysimeters, are compared with ETa data measured by a scintillometer system BLS900 (Scintec, Germany). The system measures sensible heat flux integrated along the near-infrared beam of 880 nm, length of 356 m and height of 6.3 m above grassy surface. The ETa is calculated as a residual from the energy balance equation. Another independent source of ETa data is the Bowen ratio energy balance system (BREB), which is placed roughly in the middle of the scintillometer path and adjacently (few meters) to the lysimeter.During the observation period (vegetation period 2018; March-November), ETa calculated from the weighable lysimeter was 573 mm in total and showed the highest absolute value compared to the other measurements. The calculated ETa from the BREB system is 505 mm (including condensation) and 526 mm (excluding condensation).At the beginning of the vegetation growth, the scintillometer system measured lower values of ETa than the lysimeter, but higher values than the BREB system. Contrary, at the end of May, the lysimeter ETa showed the lowest values compared to the other two systems. This can be related to the fact that the grass on the lysimeter was cut three times per year, whereas the management of other areas on the experimental site was different. The same effects were observed at the second and third cut, always with the fact that the scintillometer system showed higher values than the BREB system. After two weeks of the first and second cut, the vegetation on the lysimeters was established faster than on the surrounding grassland. As a consequence, the lysimeter ETa showed again the highest values. Only after the third cut at the end of September, the vegetation was slowly growing and the scintillometer as well the BREB system showed higher ETa values till the end of the observation month in November. These results suggest that the evapotranspiration rates are strongly dependent on the management of the grassland, which needs to be considered in the selection and design of evapotranspiration measurements.

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Atmospheric reactivity of biogenic volatile organic compounds in a maritime pine forest during the LANDEX episode 1 field campaign

The Science of The Total Environment ◽

10.1016/j.scitotenv.2020.144129 ◽

2021 ◽

Vol 756 ◽

pp. 144129

Author(s):

Kenneth Mermet ◽

Emilie Perraudin ◽

Sébastien Dusanter ◽

Stéphane Sauvage ◽

Thierry Léonardis ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Pine Forest ◽

Maritime Pine ◽

Biogenic Volatile Organic Compounds ◽

Field Campaign ◽

Atmospheric Reactivity ◽

Volatile Organic

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A comparison of bushfire fuel hazard assessors and assessment methods in dry sclerophyll forest near Sydney, Australia

International Journal of Wildland Fire ◽

10.1071/wf11034 ◽

2012 ◽

Vol 21 (6) ◽

pp. 755 ◽

Cited By ~ 19

Author(s):

Penny J. Watson ◽

Sandra H. Penman ◽

Ross A. Bradstock

Keyword(s):

Hazard Assessment ◽

Assessment Method ◽

Assessment Methods ◽

Urban Fringe ◽

The Other ◽

Fuel Load ◽

Forest Sites ◽

Sclerophyll Forest ◽

Hazard Assessments ◽

Sydney Australia

Over the last decade, fire managers in Australia have embraced the concept of ‘fuel hazard’, and guides for its assessment have been produced. The reliability of these new metrics, however, remains to be determined. This study compared fuel hazard ratings generated by five assessment teams using two Australian hazard assessment methods, in two dry sclerophyll forest sites on Sydney’s urban fringe. Attributes that underpin hazard scores, such as cover and height of various fuel layers, were also assessed. We found significant differences between teams on most variables, including hazard scores. These differences were more apparent when fuel hazard assessments focussed on individual fuel layers than when teams’ assessments were summarised into an overall fuel hazard score. Ratings of surface (litter) fuel hazard were higher when one assessment method was used than when assessors employed the other; however, ratings of elevated (shrub) and bark fuel hazard were relatively consistent across assessment methods. Fuel load estimates based on the two hazard assessment methods differed considerably, with differences between teams also significant. Inconsistency in scoring fuel hazard may lead to discrepancies in a range of management applications, which in turn may affect firefighting safety and effectiveness.

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Precipitation effects on soil characteristics in tropical rain forests of the Chocó biogeographical region

Revista Facultad Nacional de Agronomía Medellín ◽

10.15446/rfna.v69n1.54749 ◽

2016 ◽

Vol 69 (1) ◽

pp. 7813-7823 ◽

Cited By ~ 4

Author(s):

Harley Quinto Mosquera ◽

Flavio Moreno Hurtado

Keyword(s):

Terrestrial Ecosystems ◽

Exchange Capacity ◽

The Other ◽

Tropical Rainforests ◽

Curvilinear Relationship ◽

Tropical Rain Forests ◽

Total N ◽

P Content ◽

Biogeographical Region ◽

Average Annual Precipitation

Average annual precipitation (AAP) is one of the principal environmental factors that regulates processes in terrestrial ecosystems. The effect of AAP on the availability of edaphic nutrients is poorly understood, especially in tropical zones with high rainfall. In order to evaluate the effects of high AAP on the availability of soil N, P, and K, physicochemical parameters were measured in soils of three tropical rainforests in the Chocó biogeographical region with different AAPs (7,500, 8,000, and 10,000 mm yr-1). Furthermore, a bibliographical review was carried out that including studies for distinct tropical Ultisols and AAP ranging from 1,800 to 10,000 mm yr-1. The evaluated soils presented extreme acidity with high contents of Al, organic matter (OM) and total N, and low quantities of P, Mg, and Ca. The K concentrations were intermediate and the effective cation exchange capacity (ECEC) was low. On the other hand, in the evaluation of the influence of the AAP on the availability of N, P, and K in the soil, contrasting tendencies were observed. On one side, a positive curvilinear relationship was found between the availability of N and the increase in the AAP. On the other side, the available P content significantly decreased with increasing AAP. In conclusion, the excessive AAP resulted in increases in total N and low availability of P, thereby altering the dynamics of the nutrients and the carbon balance of the tropical forest

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A Simulation Study of GNSS-R Polarimetric Scattering from the Bare Soil Surface Based on the AIEM

Advances in Meteorology ◽

10.1155/2019/3647473 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Xuerui Wu ◽

Shuanggen Jin

Keyword(s):

Soil Moisture ◽

Circular Polarization ◽

Soil Surface ◽

Bare Soil ◽

Satellite System ◽

Equation Model ◽

The Other ◽

Scattering Coefficients ◽

Remote Sensing Technique ◽

Transmitted Signal

In the past two decades, global navigation satellite system-reflectometry (GNSS-R) has emerged as a new remote sensing technique for soil moisture monitoring. Some experiments showed that the antenna of V polarization is more favorable to receive the reflected signals, and the interference pattern technique (IPT) was used for soil moisture and retrieval of other geophysical parameters. Meanwhile, the lower satellite elevation angles are most impacted by the multipath. However, electromagnetic theoretical properties are not clear for GNSS-R soil moisture retrieval. In this paper, the advanced integral equation model (AIEM) is employed using the wave-synthesis technique to simulate different polarimetric scatterings in the specular directions. Results show when the incident angles are larger than 70°, scattering at RR polarization (the transmitted signal is right-hand circular polarization (RHCP), while the received one is also RHCP) is larger than that at LR polarization (the transmitted signal is RHCP, while the received one is left-hand circular polarization (LHCP)), while scattering at LR polarization is larger than that at RR polarization for the other incident angles (1°∼70°). There is an apparent dip for VV and VR scatterings due to the Brewster angle, which will result in the notch in the final receiving power, and this phenomenon can be used for soil moisture retrieval or vegetation corrections. The volumetric soil moisture (vms) effects on their scattering are also presented. The larger soil moisture will result in lower scattering at RR polarization, and this is very different from the scattering of the other polarizations. It is interesting to note that the surface correlation function only affects the amplitudes of the scattering coefficients at much less level, but it has no effects on the angular trends of RR and LR polarizations.

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The Origin of Dinosaurs and the Beginning of the Age of Dinosaurs

Short Courses in Paleontology ◽

10.1017/s2475263000000817 ◽

1989 ◽

Vol 2 ◽

pp. 7-21

Author(s):

Kevin Padian

Keyword(s):

Terrestrial Ecosystems ◽

Early Jurassic ◽

The Other ◽

Late Triassic ◽

Relevant Paper ◽

The Past ◽

General Account ◽

Extensive Information ◽

The Times

What are dinosaurs? What features characterize them? Who were their closest relatives? What were the times like when the dinosaurs first evolved? How did their appearance change the balance of diversity in terrestrial ecosystems? During the past decade we have come to know much more about these topics than ever before. What follows is only a brief review. For more extensive information, readers are referred to the chapters in Padian (1986a), particularly the Introduction, on questions of the Late Triassic - Early Jurassic transition; and to Gauthier (1984, 1986) on the characteristics of dinosaurs and their relations. Because this is meant to be a general account, like the other papers in this book, it is impossible to cite every worker, discovery, or relevant paper in the field, and some personal judgments must be exercised.

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