Abstract
AbstractVegetation indices are widely used as model inputs and for non‐destructive estimation of biomass and photosynthesis, but there have been few validation studies of the underlying relationships. To test their applicability on temperate fens and the impact of management intensity, we investigated the relationships between normalized difference vegetation index (NDVI), leaf area index (LAI), brown and green above‐ground biomass and photosynthesis potential (PP). Only the linear relationship betweenNDVIandPPwas management independent (R2 = 0·53).LAItoPPwas described by a site‐specific and negative logarithmic function (R2 = 0·07–0·68). The hyperbolic relationship ofLAIversusNDVIshowed a high residual standard error (s.e.) of 1·71–1·84 and differed between extensive and intensive meadows. Biomass andLAIcorrelated poorly (R2 = 0·30), with high species‐specific variability. Intensive meadows had a higher ratio ofLAIto biomass than extensive grasslands. The fraction of green to total biomass versusNDVIshowed considerable noise (s.e. = 0·13). These relationships were relatively weak compared with results from other ecosystems. A likely explanation could be the high amount of standing litter, which was unevenly distributed within the vegetation canopy depending on the season and on the timing of cutting events. Our results show there is high uncertainty in the application of the relationships on temperate fen meadows. For reliable estimations, management intensity needs to be taken into account and several direct measurements throughout the year are required for site‐specific correction of the relationships, especially under extensive management. UsingNDVIinstead ofLAIcould reduce uncertainty in photosynthesis models.
Highlights
Vegetation characteristics and productivity are important inputs for various statistical as well as process-oriented models, leading to an increasing demand for non-destructive measurement methods and estimations on a national or global scale
Faster spring growth at intensive meadows was reflected in plant area index (PAI) values (Figure 1b)
Intensively managed parcels exhibited a high normalized difference vegetation index (NDVI), while it was considerably lower on extensive meadows
Summary
Vegetation characteristics and productivity are important inputs for various statistical (empirical) as well as process-oriented models, leading to an increasing demand for non-destructive measurement methods and estimations on a national or global scale. The relationships between the indices and vegetation characteristics are known to be ecosystem specific (Knyazikhin et al, 1998). Investigations of these relationships on both intensively and extensively managed temperate fen grasslands are, to our knowledge, still lacking. Non-destructive estimations of vegetation characteristics can help to improve understanding and modelling of the carbon balance of these ecosystems. We investigated the relationships between common vegetation indices and vegetation characteristics
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