Matching the phenology of Net Ecosystem Exchange and vegetation indices estimated with MODIS and FLUXNET in-situ observations
Balzarolo, M. ; Vicca, S. ; Nguy-Robertson, A.L. ; Bonal, D. ; Elbers, J.A. ; Fu, Y.H. ; Grünwald, T. ; Horemans, J.A. ; Papale, D. ; Peñuelas, J. ; Suyker, A. ; Veroustraete, F. - \ 2016
Remote Sensing of Environment 174 (2016). - ISSN 0034-4257 - p. 290 - 300.
Net Ecosystem Exchange (NEE) - Phenology - Plant functional types (PFT's) - Start of growing season (SGS) - Start of net carbon uptake (SGS) - Vegetation indices (VI's)
Shifts in ecosystem phenology play an important role in the definition of inter-annual variability of net ecosystem carbon uptake. A good estimate at the global scale of ecosystem phenology, mainly that of photosynthesis or gross primary productivity (GPP), may be provided by vegetation indices derived from MODIS satellite image data.However, the relationship between the start date of a growing (or greening) season (SGS) when derived from different vegetation indices (VI's), and the starting day of carbon uptake is not well elucidated. Additionally, the validation of existing phenology data with in-situ measurements is largely missing. We have investigated the possibility to use different VI's to predict the starting day of the growing season for 28 FLUXNET sites as well as MODIS data. This analysis included main plant functional types (PFT's).Of all VI's taken into account in this paper, the NDVI (Normalized Difference Vegetation Index) shows the highest correlation coefficient for the relationship between the starting day of the growing season as observed with MODIS and in-situ observations. However, MODIS observations elicit a 20-21 days earlier SGS date compared to in-situ observations. The prediction for the NEE start of the growing season diverges when using different VI's, and seems to depend on the amplitude for carbon and VI and on PFT. The optimal VI for estimation of a SGS date was PFT-specific - for example the WRDVI for cropland, but the MODIS NDVI performed best when applied as an estimator for Net Ecosystem Exchange and when considering all PFT's pooled.
Genetic diversity and linkage disequilibrium analysis in elite sugar beet breeding lines and wild beet accessions
Adetunji, I. ; Willems, G. ; Tschoep, H. ; Bürkholz, A. ; Barnes, S. ; Boer, M.P. ; Malosetti, M. ; Horemans, S. ; Eeuwijk, F. van - \ 2014
Theoretical and Applied Genetics 127 (2014)3. - ISSN 0040-5752 - p. 559 - 571.
beta-vulgaris l. - genome-wide association - yellow-vein-virus - population-structure - ssp maritima - rhizomania resistance - restorer gene - markers - map - dna
Linkage disequilibrium decay in sugar beet is strongly affected by the breeding history, and varies extensively between and along chromosomes, allowing identification of known and unknown signatures of selection. Genetic diversity and linkage disequilibrium (LD) patterns were investigated in 233 elite sugar beet breeding lines and 91 wild beet accessions, using 454 single nucleotide polymorphisms (SNPs) and 418 SNPs, respectively. Principal coordinate analysis suggested the existence of three groups of germplasm, corresponding to the wild beets, the seed parent and the pollen parent breeding pool. LD was investigated in each of these groups, with and without correction for genetic relatedness. Without correction for genetic relatedness, in the pollen as well as the seed parent pool, LD persisted beyond 50 centiMorgan (cM) on four (2, 3, 4 and 5) and three chromosomes (2, 4 and 6), respectively; after correction for genetic relatedness, LD decayed after