Search Results - "Nilson, Tiit"

Digital photography for tracking the phenology of an evergreen conifer stand by Lang, Mait, Nilson, Tiit, Kuusk, Andres, Pisek, Jan, Korhonen, Lauri, Uri, Veiko

“…•A regular digital camera was used as an imaging radiometer.•The LinearRatio is a reliable method for tracking the phenology of canopy gap fraction and…”
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How to quantify tree leaf area index in an open savanna ecosystem: A multi-instrument and multi-model approach by Ryu, Youngryel, Sonnentag, Oliver, Nilson, Tiit, Vargas, Rodrigo, Kobayashi, Hideki, Wenk, Rebecca, Baldocchi, Dennis D.

“…Savannas are spatially heterogeneous, open ecosystems, thus efforts to quantify canopy structure with methods developed for homogeneous, closed canopies are…”
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Impact of understory vegetation on forest canopy reflectance and remotely sensed LAI estimates by Eriksson, Helena Margaretha, Eklundh, Lars, Kuusk, Andres, Nilson, Tiit

“…Forest leaf area index (LAI), is an important variable in carbon balance models. However, understory vegetation is a recognized problem that limits the…”
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Estimation of vegetation clumping index using MODIS BRDF data by Pisek, Jan, Chen, Jing Ming, Nilson, Tiit

“…The foliage clumping index quantifies the degree of the deviation of leaf spatial distribution in the canopy from the random case. It is of comparable…”
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Options for estimating horizontal visibility in hemiboreal forests using sparse airborne laser scanning data and forest inventory data by Lang, Mait, Vennik, Kersti, Põldma, Andrus, Nilson, Tiit

“…Horizontal visibility in hemiboreal forest transects was measured in the field and then predicted, both from forest inventory (FI) data and from airborne laser…”
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Responses of the reflectance indices PRI and NDVI to experimental warming and drought in European shrublands along a north–south climatic gradient by Mänd, Pille, Hallik, Lea, Peñuelas, Josep, Nilson, Tiit, Duce, Pierpaolo, Emmett, Bridget A., Beier, Claus, Estiarte, Marc, Garadnai, János, Kalapos, Tibor, Schmidt, Inger Kappel, Kovács-Láng, Edit, Prieto, Patricia, Tietema, Albert, Westerveld, Joke W., Kull, Olevi

“…The aim of this study was to evaluate the use of ground-based canopy reflectance measurements to detect changes in physiology and structure of vegetation in…”
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Seasonal reflectance trends of hemiboreal birch forests by Rautiainen, Miina, Nilson, Tiit, Lükk, Tõnu

“…MODIS, AVHRR and SPOT VEGETATION satellite images have recently been used to track coarse scale seasonal vegetation dynamics of boreal and temperate forests…”
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Assessment of MODIS NPP algorithm-based estimates using soil fertility and forest inventory data in mixed hemiboreal forests by Lang, Mait, Kõlli, Raimo, Nikopensius, Maris, Nilson, Tiit, Neumann, Mathias, Moreno, Adam

“…Optical remote sensing data-based estimates of terrestrial net primary production (NPP) are released by different projects using light use efficiency-type…”
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Simulation of the reflectance of ground vegetation in sub-boreal forests by Kuusk, Andres, Lang, Mait, Nilson, Tiit

“…To study the reflectance spectra of ground vegetation in forests a series of field measurements was performed by a GER-2600 spectrometer in Estonian and…”
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Estimating canopy cover in Scots pine stands by Rautiainen, Miina, Stenberg, Pauline, Nilson, Tiit

“…The way canopy cover is defined and measured influences the obtained canopy cover percentage. Estimates of canopy cover are needed, for example, in canopy…”
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MERIS GPP/NPP product for Estonia: II. Complex meteorological limiting factor and optimum leaf area index / MERIS’e GPP/NPP tulem Eesti jaoks: II. Kompleksne meteoroloogiline piirangutegur ja optimaalne lehepinnaindeks by Nilson, Tiit, Rennel, Mattias, Lang, Mait

“…The merits and possible problems of the light use efficiency-concept based GPP/NPP models applied together with satellite images and meteorological data to…”
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A note on meteorological variables related trends in the MODIS NPP product for Estonia / Meteoroloogilised andmed põhjustavad vigu MODISe primaarproduktsiooni hinnangutes Eesti alal by Eenmäe, Alo, Nilson, Tiit, Lang, Mait

“…The MODIS (The Moderate Resolution Imaging Spectroradiometer) yearly NPP (Net Primary Production) 1 km resolution products were collected over Estonia for…”
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Forest Reflectance Modeling: Theoretical Aspects and Applications by Nilson, Tiit, Kuusk, Andres, Lang, Mait, Lükk, Tõnu

“…Forest reflectance models are able to contribute to the interpretation of satellite images over forested areas. A multipurpose forest reflectance model, its…”
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MERIS GPP/NPP product for Estonia: I. Algorithm and preliminary results of simulation / MERIS’e GPP/NPP tulem Eesti jaoks: I. Algoritm ja mudelarvutuste esialgsed tulemused by Nilson, Tiit, Rennel, Mattias, Luhamaa, Andres, Hordo, Maris, Olesk, Aire, Lang, Mait

“…A light use efficiency (LUE) type model named EST_PP to simulate the yearly gross primary production (GPP) and net primary production (NPP) of Estonian land on…”
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Revisiting the vegetation hot spot modeling: Case of Poisson/Binomial leaf distributions by Kallel, Abdelaziz, Nilson, Tiit

“…The accuracy of spaceborne/airborne sensor measurements in the solar domain keeps increasing over time. High resolution, multi-directional and hyperspectral…”
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Metsa lehepinnaindeksi kaardistamine lennukilidari, satelliidipiltide ja maapealsete mõõtmiste abil Järvselja VALERI testalal / Leaf area index mapping with airborne lidar, satellite images and ground measurements in Järvselja VALERI test site by Kodar, Ave, Lang, Mait, Arumäe, Tauri, Eenmäe, Alo, Pisek, Jan, Nilson, Tiit

“…The aim of this study was to compile the leaf area index (LAI) map of a 3×3 km VALERI test site in Järvselja, Estonia. Canopy transmittance measurements of LAI…”
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On the correct estimation of effective leaf area index: Does it reveal information on clumping effects? by Ryu, Youngryel, Nilson, Tiit, Kobayashi, Hideki, Sonnentag, Oliver, Law, Beverly E., Baldocchi, Dennis D.

“…Effective leaf area index is routinely quantified with optical instruments that measure gap fraction through the probability of beam penetration of sunlight…”
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Comparison of methods for measuring gap size distribution and canopy nonrandomness at Järvselja RAMI (RAdiation transfer Model Intercomparison) test sites by Pisek, Jan, Lang, Mait, Nilson, Tiit, Korhonen, Lauri, Karu, Helen

“…▶ Comprehensive comparison of approaches quantifying beyond-shoot (element) clumping index. ▶ Assessed at one Silver birch and one Scots Pine RAMI stand in…”
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Diffuse sky radiation influences the relationship between canopy PRI and shadow fraction by Mõttus, Matti, Takala, Tuure L.H., Stenberg, Pauline, Knyazikhin, Yuri, Yang, Bin, Nilson, Tiit

“…[Display omitted] The Photochemical Reflectance Index (PRI) of green leaves is an indicator of photosynthetic downregulation: when the photosynthetic apparatus…”
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Simulation of statistical characteristics of gap distribution in forest stands by Nilson, Tiit, Kuusk, Andres, Lang, Mait, Pisek, Jan, Kodar, Ave

“…► Simulated standard deviations of gap fraction agree sufficiently well with the results obtained by LAI-2000 and digital hemispheric photo measurements. ► The…”
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