scholarly journals Does the Normalized Difference Vegetation Index explain spatial and temporal variability in sap velocity in temperate forest ecosystems?

2019 ◽  
Vol 23 (4) ◽  
pp. 2077-2091 ◽  
Author(s):  
Anne J. Hoek van Dijke ◽  
Kaniska Mallick ◽  
Adriaan J. Teuling ◽  
Martin Schlerf ◽  
Miriam Machwitz ◽  
...  
Keyword(s):  
Temperate Forest ◽  
Vegetation Index ◽  
Forest Ecosystems ◽  
Normalized Difference Vegetation Index ◽  
Deciduous Forest ◽  
Significant Negative Correlation ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Temperate Deciduous Forest ◽  
Temperate Deciduous

Abstract. Understanding the link between vegetation characteristics and tree transpiration is a critical need to facilitate satellite-based transpiration estimation. Many studies use the Normalized Difference Vegetation Index (NDVI), a proxy for tree biophysical characteristics, to estimate evapotranspiration. In this study, we investigated the link between sap velocity and 30 m resolution Landsat-derived NDVI for 20 days during 2 contrasting precipitation years in a temperate deciduous forest catchment. Sap velocity was measured in the Attert catchment in Luxembourg in 25 plots of 20×20 m covering three geologies with sensors installed in two to four trees per plot. The results show that, spatially, sap velocity and NDVI were significantly positively correlated in April, i.e. NDVI successfully captured the pattern of sap velocity during the phase of green-up. After green-up, a significant negative correlation was found during half of the studied days. During a dry period, sap velocity was uncorrelated with NDVI but influenced by geology and aspect. In summary, in our study area, the correlation between sap velocity and NDVI was not constant, but varied with phenology and water availability. The same behaviour was found for the Enhanced Vegetation Index (EVI). This suggests that methods using NDVI or EVI to predict small-scale variability in (evapo)transpiration should be carefully applied, and that NDVI and EVI cannot be used to scale sap velocity to stand-level transpiration in temperate forest ecosystems.

scholarly journals Does NDVI explain spatial and temporal variability in sap velocity in temperate forest ecosystems?

2018 ◽  
Author(s):  
Anne J. Hoek van Dijke ◽  
Kaniska Mallick ◽  
Adriaan J. Teuling ◽  
Martin Schlerf ◽  
Miriam Machwitz ◽  
...  
Keyword(s):  
Temperate Forest ◽  
Vegetation Index ◽  
Forest Ecosystems ◽  
Normalized Difference Vegetation Index ◽  
Deciduous Forest ◽  
Significant Negative Correlation ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Temperate Deciduous Forest ◽  
Temperate Deciduous

Abstract. There is a need for a better understanding of the link between vegetation characteristics and tree transpiration to facilitate satellite derived transpiration estimation. Many studies use the normalized difference vegetation index (NDVI), a proxy for tree biophysical characteristics, to estimate evapotranspiration. In this study we investigated the link between sap velocity and 30 m resolution Landsat derived NDVI for twenty days during two contrasting precipitation years in a temperate deciduous forest catchment. Sap velocity was measured in the Attert catchment in Luxembourg in 25 plots of 20 × 20 m covering three geologies with sensors installed in 2–4 trees per plot. The results show that sap velocity and NDVI were significantly positively correlated in April, i.e., NDVI successfully captured the pattern of sap velocity during the phase of green-up. After green-up, a significant negative correlation was found during half of the studied days. During a dry period, sap velocity was uncorrelated to NDVI, but influenced by geology and aspect. In summary, in our study area, the correlation between sap velocity and NDVI was not constant, but varied with phenology and water availability. The same behaviour was found for the Enhanced Vegetation Index (EVI). This suggests that methods using NDVI or EVI to predict small-scale variability in (evapo)transpiration should be carefully applied and that NDVI and EVI cannot be used to scale sap velocity to stand level transpiration in temperate forest ecosystems.

scholarly journals Can vegetation index track the interannual variation in gross primary production of temperate deciduous forests?

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Fan Liu ◽  
Chuankuan Wang ◽  
Xingchang Wang
Keyword(s):  
Primary Production ◽  
Vegetation Index ◽  
Near Infrared ◽  
Deciduous Forest ◽  
Gross Primary Production ◽  
Growing Season ◽  
Temperate Deciduous Forest ◽  
Near Infrared Reflectance ◽  
Modis Ndvi ◽  
Temperate Deciduous

Abstract Background Vegetation indices (VIs) by remote sensing are widely used as simple proxies of the gross primary production (GPP) of vegetation, but their performances in capturing the inter-annual variation (IAV) in GPP remain uncertain. Methods We evaluated the performances of various VIs in tracking the IAV in GPP estimated by eddy covariance in a temperate deciduous forest of Northeast China. The VIs assessed included the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), and the near-infrared reflectance of vegetation (NIRv) obtained from tower-radiometers (broadband) and the Moderate Resolution Imaging Spectroradiometer (MODIS), respectively. Results We found that 25%–35% amplitude of the broadband EVI tracked the start of growing season derived by GPP (R2: 0.56–0.60, bias < 4 d), while 45% (or 50%) amplitudes of broadband (or MODIS) NDVI represented the end of growing season estimated by GPP (R2: 0.58–0.67, bias < 3 d). However, all the VIs failed to characterize the summer peaks of GPP. The growing-season integrals but not averaged values of the broadband NDVI, MODIS NIRv and EVI were robust surrogates of the IAV in GPP (R2: 0.40–0.67). Conclusion These findings illustrate that specific VIs are effective only to capture the GPP phenology but not the GPP peak, while the integral VIs have the potential to mirror the IAV in GPP.

Temperate Deciduous Forest Ecosystems of the World

1992 ◽  
Vol 19 (5) ◽  
pp. 584
Author(s):  
John R. Packham ◽  
E. Rohrig ◽  
B. Ulrich
Keyword(s):  
Forest Ecosystems ◽  
Deciduous Forest ◽  
Temperate Deciduous Forest ◽  
The World ◽  
Temperate Deciduous

Assessment of forest GPP variations in central Italy

2007 ◽  
Vol 37 (10) ◽  
pp. 1944-1953 ◽  
Author(s):  
A. Rodolfi ◽  
M. Chiesi ◽  
G. Tagliaferri ◽  
P. Cherubini ◽  
F. Maselli
Keyword(s):  
Vegetation Index ◽  
Management Practices ◽  
Forest Ecosystems ◽  
Normalized Difference Vegetation Index ◽  
Deciduous Forest ◽  
Meteorological Data ◽  
Central Italy ◽  
Mountain Forest ◽  
Italian Regions ◽  
Local Station

A debate is in progress concerning the possible effects of climate changes on the primary production of both natural and artificial ecosystems. The current investigation builds on the hypothesis that trends of increasing air temperature observed in several Italian regions should positively affect productivity of mountain forest ecosystems. Temperature rise in the Mugello valley (central Italy) in the period 1986–2001 was first confirmed by the analysis of data from a local station. The effects of this rise on the productivity of deciduous forest ecosystems (dominated by beech, Fagus sylvatica L.) were then analysed through estimates of the fraction of absorbed photosynthetically active radiation (FAPAR) derived from the US National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer satellite normalized difference vegetation index (NDVI) data. The use of a simplified parametric model (C-Fix) then allowed the combination of these FAPAR estimates with meteorological data (temperature and radiation) to produce annual values of forest gross primary productivity (GPP). Finally, validation of these GPP estimates was carried out by a comparison with dendrochronological measurements taken in the study forests. Because tree measurements were affected by external factors not exclusively related to forest GPP (stand aging, management practices, etc.), the comparison gave positive results only after applying a detrending operation to both series of annual GPP estimates and dendrochronological data. These results are a first indication that the rise in temperature that has occurred in Italy in the last decades has positively affected the productivity of mountain forest ecosystems.

scholarly journals A Spatial Relationship between Canopy and Understory Leaf Area Index in an Old-Growth Cool-Temperate Deciduous Forest

Forests ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1037
Author(s):  
Yosuke Tanioka ◽  
Yihan Cai ◽  
Hideyuki Ida ◽  
Mitsuru Hirota
Keyword(s):  
Spatial Distribution ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Deciduous Forest ◽  
Multiple Point ◽  
Spatial And Temporal Variability ◽  
Temperate Deciduous Forest ◽  
Area Index ◽  
Cool Temperate ◽  
Temperate Deciduous

Quantification of leaf area index (LAI) is essential for understanding forest productivity and the atmosphere–vegetation interface, where the majority of gas and energy exchange occurs. LAI is one of the most difficult plant variables to adequately quantify, owing to large spatial and temporal variability, and few studies have examined the horizontal and vertical distribution of LAI in forest ecosystems. In this study, we demonstrated the LAI distribution in each layer from the understory to canopy using multiple-point measurements (121 points) and examined the relationships among layers in a cool-temperate deciduous forest. LAI at each point, and the spatial distribution of LAI in each layer, varied within the forest. The spatial distribution of LAI in the upper layer was more heterogeneous than that of LAI at the scale of the entire forest. Significant negative correlations were observed between the upper- and lower-layer LAI. Our results indicate that the understory compensates for gaps in LAI in the upper layer; thus, the LAI of the entire forest tends to remain spatially homogeneous even in a mature forest ecosystem.

Palynology of the interglacial deposits at Little Oakley, Essex, and their correlation

1990 ◽  
Vol 328 (1248) ◽  
pp. 341-357 ◽  
Keyword(s):  
Temperate Forest ◽  
Deciduous Forest ◽  
Late Glacial ◽  
Sensu Stricto ◽  
Temperate Deciduous Forest ◽  
Sediment Samples ◽  
River Floodplains ◽  
Temperate Trees ◽  
Northwest Europe ◽  
Temperate Deciduous

Pollen analyses of sediment samples from five boreholes in the Little Oakley Silts and Sands provide evidence of contemporary vegetational development. Although the sequence is fragmentary, the succession can be reassembled based on the well established subdivisions of vegetational development during temperate stages in northwest Europe. The earliest vegetation represented is of late-glacial herb-dominated character. This is followed by an expansion of Betula , and subsequently Pinus , which together with Picea , Alnus , and later, Ulmus form the pre-temperate forest. After the decline in Pinus , Ulmus becomes dominant in the early temperate substage. The later expansion of Quercus and accompanied decrease in Ulmus marks the development of fully temperate deciduous forest. Other temperate trees such as Tilia and Fraxinus are rare. Throughout, the neighbouring river floodplains supported widespread herb-dominated grassland. The latter may have been maintained by alluvial aggradation and large vertebrate activity. Pollen analysis from a Megaloceros cf. dawkinsi antler base collected by S. H. Warren shows that the find dates from the early temperate substage of the interglacial. Comparison of the Little Oakley pollen sequence with others obtained from Britain, The Netherlands and neighbouring countries suggests probable correlation with the Cromerian sensu stricto of West Runton, England and ‘Interglacials III or IV ’ of the Dutch ‘Cromerian Complex’. The preceding possible late-glacial spectrum should therefore equate with the late Beestonian.

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