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Spremljanje toka ogljika v kraških ekosistemih z mikrometeorološkimi metodami
Full text linkKljub intenzivnim raziskavam o kroženju ogljika so nekateri ekosistemi na tem področju še vedno slabo raziskani. Eni takšnih so tudi kraški ekosistemi. Raziskave predstavljene v tem delu so bile narejene na ravnini Podgorskega Krasa (400 - 430 m.n.v.) v sub-mediteranski regiji Slovenije. Na zaraščajočem območju sta bili izbrani dve ploskvi: pašnik in površina v zaraščanju. Na obeh ploskvah so bile v juliju 2008 vzpostavljene mikrometeorološke meritve po metodi Eddy covariance (EC) na višini 15 m (zaraščanje) in 2 m (pašnik). Prav tako so bile v okviru ploskev izvajane meritve dihanja tal z mikrometeorološko metodo zaprtih in odprtih komor ter vse potrebne spremljajoče meteorološke meritve. V preučevanem obdobju od 1. 7. 2008 do 30. 11. 2012 ni bilo med obema ploskvama zaznati večjih razlik v zračni temperaturi in količini padavin. Kar se tiče kvalitete podatkov pridobljenih po metodi EC, smo uporabili 59,7 % podatkov na ploskvi zaraščanje in 33,7 % podatkov na ploskvi pašnik. Ploskev zaraščanje je v preučevanem obdobju delovala kot ponor ogljika (NEE = -184 Ž 19 gCm-2leto-1), medtem ko je bila ploskev pašnik vir (NEE = 293 Ž 34 gCm-2leto-1) ogljika. Na podlagi mikrometeoroloških meritev po metodi EC lahko zaključimo, da zaraščanje pašnikov vpliva na povečano ponorno aktivnost ekosistema za ogljik. Ko smo na podatke NEE aplicirali B4 korekcijo, ki je potrebna zaradi samogretja merilne opreme, je ploskev zaraščanje delovala kot šibak ponor ogljika (NEE = -28 gCm-2leto-1), medtem ko je pašnik deloval kot vir (NEE = 456 gCm-2leto-1) ogljika. Ob aplikaciji korekcije NEE zaradi samogretja merilne opreme, ki je bila razvita na podlagi lastnih meritev (SISC), je ploskev zaraščanje delovala kot ponor ogljika (NEE = -127 gCm-2leto-1), medtem ko je pašnik deloval kot vir (NEE = 362 gCm-2leto-1) ogljika. Meritve so pokazale, da je potrebna tovrstna korekcija tudi v naših razmerah in ne le v hladnejših (Burbaet al., 2008), vendar mora biti uporabljena korekcija razvita na podlagi lastnih meritev. Kar zadeva meritev dihanja tal smo v študiji pokazali, da lahko avtomatski sistem za tovrstne meritve močno prispeva k večji časovni gotovosti meritev. Kombinacija meritev temperature in vlage tal skupaj z ročnimi meritvami dihanja tal pa močno prispeva k prostorki gotovosti meritev.Despite intensive research, carbon cycle is still under-investigated and not fully understood for many ecosystems, especially the ones which are of minor direct importance in terms of food and wood production. Karst ecosystems can be included in this group of ecosystems. The study was conducted at the Podgorski Kras plateau (400 - 430 m.a.s.l.), which was in the past subjected to agriculture land abandonment, in the sub-mediterranean region of Slovenia (SW Slovenia). Within the study area two study sites were chosen: grassland and forest succession. At both sites, in July 2008, an open-path Eddy covariance (EC) was installed at 15 m and 2 m height for Succession site and Grassland site, respectively. Also Rs and other auxiliary measurements were performed. For the observed period (July 1th 2008 - November 30th 2012) no major differences were measured between Grassland site and Succession site concerning air temperature and precipitation. Concerning the EC data quality for the observed period, 59.7% and 33.7% of expected data have not been discarded for Succession site and Grassland site, respectively. On the average annual basis Succession site was net sink of carbon (NEE = -184 Ž 19 gCm-2y-1) while Grassland site was a source of carbon (NEE = 293 Ž 34 gCm-2y-1). Based on the eddy covariance measurements it can be concluded that overgrown area increased sink activity compared to the extensive grassland in observed period. After B4 correction was applied on our datasets cumulative NEE fluxes changed. For observation period Succession site shifted to weak sink (-28 gCm-2y-1) of carbon, while the Grassland site remained a source (456gCm-2y-1). Applying SISC correction NEE changed to -127 gCm-2y-1 and 362 gCm-2y-1 for Succession site and Grassland site, respectively. Our measurements showed the need for self-heating correction also for our ecosystems. It is more appropriate to use site specific self-heating correction based and developed on own measurements than those suggested by Burba et al. (2008). Concerning the Rs measurements it can be concluded that knowledge of temporal variability can be greatly improved with an automatic system. Corresponding measurements of soil temperature and moisture together with manual Rs measurements, improved the knowledge about spatial variability of Rs
Estimation of solar radiation in forest from digital hemispherical photographyin suboptimal conditions
Full text linkEcosystem carbo-dynamic research-development potentials of the laboratory of Electronic Devices
Full text linkEstimation of carbon fluxes from eddy covariance data and satellite-derived vegetation indices in a karst grassland (Podgorski Kras, Slovenia)
No full textMestrado MEDfOR - Mediterranean Forestry and Natural Resources Management - Instituto Superior de AgronomiaThe Eddy covariance method is a widespread method used for measuring carbon fluxes between the atmosphere and the ecosystem. It provides a high temporal resolution of measurements, but it is restricted to an area around the tower called footprint, and other methods are usually used in combination with eddy covariance data in order to estimate carbon fluxes for larger areas. Spectral vegetation indices derived from increasingly available satellite data can be combined with eddy covariance data to estimate carbon fluxes outside of the tower footprint. Following that approach, the present study attempted to model carbon fluxes for a karst grassland in Slovenia. Three types of model were considered: (1) a linear relationship between NEE or GPP and each vegetation index, (2) a linear relationship between GPP and the product of a vegetation index with PAR, and (3) a simplified LUE model assuming a constant LUE. We compared the performance of several vegetation indices from two sources (Landsat and SPOT-Vegetation) as predictors of NEE and GPP, based on three accuracy metrics (R², RMSE and AIC). Two types of aggregation of flux data were explored, midday average fluxes and daily average fluxes. The Vapor Pressure Deficit was used to separate the growing season in two phases, a greening phase and a dry phase, which were considered separately in the modelling process, in addition to the growing season as a whole. The results showed that NDVI was the best predictor of GPP and NEE during the greening phase, whereas water related vegetation indices, namely LSWI and MNDWI were the best predictors during the dry phase, both for midday and daily aggregates. Model type 1 (linear relationship) was found to be the best in many cases. The best regression equations obtained were used to illustrate the mapping of GPP and NEE for the study areaN/
Ecosystem carbo-dynamic research-development potentials of the laboratory od electronic devices
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Estimation of carbon fluxes from eddy covariance data and satellite-derived vegetation indices in a karst grassland (Podgorski Kras, Slovenia)
No full textMestrado MEDfOR - Mediterranean Forestry and Natural Resources Management - Instituto Superior de AgronomiaThe Eddy covariance method is a widespread method used for measuring carbon fluxes between the atmosphere and the ecosystem. It provides a high temporal resolution of measurements, but it is restricted to an area around the tower called footprint, and other methods are usually used in combination with eddy covariance data in order to estimate carbon fluxes for larger areas. Spectral vegetation indices derived from increasingly available satellite data can be combined with eddy covariance data to estimate carbon fluxes outside of the tower footprint. Following that approach, the present study attempted to model carbon fluxes for a karst grassland in Slovenia. Three types of model were considered: (1) a linear relationship between NEE or GPP and each vegetation index, (2) a linear relationship between GPP and the product of a vegetation index with PAR, and (3) a simplified LUE model assuming a constant LUE. We compared the performance of several vegetation indices from two sources (Landsat and SPOT-Vegetation) as predictors of NEE and GPP, based on three accuracy metrics (R², RMSE and AIC). Two types of aggregation of flux data were explored, midday average fluxes and daily average fluxes. The Vapor Pressure Deficit was used to separate the growing season in two phases, a greening phase and a dry phase, which were considered separately in the modelling process, in addition to the growing season as a whole. The results showed that NDVI was the best predictor of GPP and NEE during the greening phase, whereas water related vegetation indices, namely LSWI and MNDWI were the best predictors during the dry phase, both for midday and daily aggregates. Model type 1 (linear relationship) was found to be the best in many cases. The best regression equations obtained were used to illustrate the mapping of GPP and NEE for the study areaN/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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