The application of APEX images in the assessment of the state of non-forest vegetation in the Karkonosze Mountains

Abstract Information about vegetation condition is needed for the effective management of natural resources and the estimation of the effectiveness of nature conservation. The aim of the study was to analyse the condition of non-forest mountain communities: synanthropic communities and natural grasslands. UNESCO’s M&B Karkonosze Transboundary Biosphere Reserve was selected as the research area. The analysis was based on 40 field test polygons and APEX hyperspectral images. The field measurements allowed the collection of biophysical parameters - Leaf Area Index (LAI), fraction of Absorbed Photosynthetically Active Radiation (fAPAR) and chlorophyll content - which were correlated with vegetation indices calculated using the APEX images. Correlations were observed between the vegetation indices (general condition, plant structure) and total area of leaves (LAI), as well as fraction of Absorbed Photosynthetically Active Radiation (fAPAR). The outcomes show that the non-forest communities in the Karkonosze are in good condition, with the synanthropic communities characterised by better condition compared to the natural communities.

Download Full-text

Relationship between Fraction of Photosynthetically Active Radiation and Vegetation Indices, Leaf Area Index of Corn and Soybean

ACTA AGRONOMICA SINICA ◽

10.3724/sp.j.1006.2008.02046 ◽

2009 ◽

Vol 34 (11) ◽

pp. 2046-2052

Author(s):

Fei YANG

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Photosynthetically Active Radiation ◽

Vegetation Indices ◽

Area Index ◽

Active Radiation

Download Full-text

A Framework for Consistent Estimation of Leaf Area Index, Fraction of Absorbed Photosynthetically Active Radiation, and Surface Albedo from MODIS Time-Series Data

IEEE Transactions on Geoscience and Remote Sensing ◽

10.1109/tgrs.2014.2370071 ◽

2015 ◽

Vol 53 (6) ◽

pp. 3178-3197 ◽

Cited By ~ 23

Author(s):

Zhiqiang Xiao ◽

Shunlin Liang ◽

Jindi Wang ◽

Donghui Xie ◽

Jinling Song ◽

...

Keyword(s):

Time Series ◽

Leaf Area Index ◽

Photosynthetically Active Radiation ◽

Surface Albedo ◽

Time Series Data ◽

Series Data ◽

Consistent Estimation ◽

Area Index ◽

Active Radiation ◽

Absorbed Photosynthetically Active Radiation

Download Full-text

Upscaling from Instantaneous to Daily Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) for Satellite Products

Remote Sensing ◽

10.3390/rs12132083 ◽

2020 ◽

Vol 12 (13) ◽

pp. 2083

Author(s):

Siyuan Chen ◽

Liangyun Liu ◽

Xue He ◽

Zhigang Liu ◽

Dailiang Peng

Keyword(s):

Zenith Angle ◽

Photosynthetically Active Radiation ◽

Solar Zenith Angle ◽

Field Measurements ◽

Area Index ◽

Active Radiation ◽

Sensing Applications ◽

Typical Satellite ◽

Absorbed Photosynthetically Active Radiation ◽

Local Noon

The fraction of absorbed photosynthetically active radiation (FAPAR) is an essential climate variable (ECV) widely used for various ecological and climate models. However, all the current FAPAR satellite products correspond to instantaneous FAPAR values acquired at the satellite transit time only, which cannot represent the variations in photosynthetic processes over the diurnal period. Most studies have directly used the instantaneous FAPAR as a reasonable approximation of the daily integrated value. However, clearly, FAPAR varies a lot according to the weather conditions and amount of incoming radiation. In this paper, a temporal upscaling method based on the cosine of the solar zenith angle (SZA) at local noon ( c o s ( S Z A n o o n ) ) is proposed for converting instantaneous FAPAR to daily integrated FAPAR. First, the diurnal variations in FAPAR were investigated using PROSAIL (a model of Leaf Optical Properties Spectra (PROSPECT) integrating a canopy radiative transfer model (Scattering from Arbitrarily Inclined Leaves, SAIL)) simulations with different leaf area index (LAI) values corresponding to different latitudes. It was found that the instantaneous black sky FAPAR at 09:30 AM provided a good approximation for the daily integrated black sky FAPAR; this gave the highest correlation (R2 = 0.995) and lowest Root Mean Square Error (RMSE = 0.013) among the instantaneous black sky FAPAR values observed at different times. Secondly, the difference between the instantaneous black sky FAPAR values acquired at different times and the daily integrated black sky FAPAR was analyzed; this could be accurately modelled using the cosine value of solar zenith angle at local noon ( c o s ( S Z A n o o n ) ) for a given vegetation scene. Therefore, a temporal upscaling method for typical satellite products was proposed using a cos(SZA)-based upscaling model. Finally, the proposed cos(SZA)-based upscaling model was validated using both the PROSAIL simulated data and the field measurements. The validated results indicated that the upscaled daily black sky FAPAR was highly consistent with the daily integrated black sky FAPAR, giving very high mean R2 values (0.998, 0.972), low RMSEs (0.007, 0.014), and low rMAEs (0.596%, 1.378%) for the simulations and the field measurements, respectively. Consequently, the cos(SZA)-based method performs well for upscaling the instantaneous black sky FAPAR to its daily value, which is a simple but extremely important approach for satellite remote sensing applications related to FAPAR.

Download Full-text