Variability in Tree-ring Width and NDVI Responses to Climate at a Landscape Level

Abstract

Inter-annual climatically driven growth variability of above-ground biomass compartments (for example, tree stems and foliage) controls the intensity of carbon sequestration into forest ecosystems. However, understanding the differences between the climatic response of stem and foliage at the landscape level is limited. In this study, we examined the climate-growth response of stem and leaf biomass and their relationship for Pinus sylvestris (PISY) and Picea abies (PCAB) in topographically complex landscapes. We used tree-ring width chronologies and time series of the normalized difference vegetation index (NDVI) derived from high-resolution Landsat scenes as proxies for stem and leaf biomass, respectively. We then compared growth variability and climate-growth relationships of both biomass proxies between topographical categories. Our results show that the responses of tree rings to climate differ significantly from those found in NDVI, with the stronger climatic signal observed in tree rings. Topography had distinct but species-specific effects: At moisture-limited PISY stands, stem biomass (tree rings) was strongly topographically driven, and leaf biomass (NDVI) was relatively insensitive to topographic variability. In landscapes close to the climatic optimum of PCAB, the relationship between stem and leaf biomass was weak, and their correlations with climate were often inverse, with no significant effects of topography. Different climatic signals from NDVI and tree rings suggest that the response of canopy and stem growth to climate change might be decoupled. Furthermore, our results hint toward different prioritizations of biomass allocation in trees under stressful conditions which might change allometric relationships between individual tree compartments in the long term.

Vegetation Index Research on the Basis of Tree-Ring Data: Current Status and Prospects

“…In addition, the NDVI values were calculated using high-resolution 30 m Landsat data to analyze and compare the climate signals of the leaf biomass and stem biomass under complex terrain. Compared with the NDVI data with a 250 m spatial resolution, the NDVI data with a 30 m spatial resolution did not enhance the correlation between the tree-ring width and NDVI, which indicates that the NDVI data with a 250 m spatial resolution may be sufficient to study the correlation between the tree-ring parameters and NDVI [66]. In addition to remote sensing observation data, phenological cameras and drones, as near-surface observation technologies, have also become new sources of vegetation data information [67].…”

“…The tree-ring parameters are more closely related to climate factors than the NDVI. This might be affected by changes in biomass allocation during drought, the spectral distortion of remote sensing data, and the effects of different meteorological conditions on the stem and crown [66]. The relationship between the annual forest growth and NDVI were quantified in different forest types and regions.…”

Short-Term Tree-Ring Series of Pinus hartwegii Lindl. Taken at Ground Level Correlate to Normalized Difference Vegetation Index Series

“…Some authors have reported weak and divergent correlations between the NDVI and tree-ring measurements of coniferous and deciduous species [38][39][40], but they used data from sensors of lower spatial resolution, which may explain this lack of significance. Mašek et al [13] reported that tree rings and the NDVI were decoupled for Pinus sylvetris and Abies picea; however, they suggested that topography is very important in explaining NDVI variation and tree growth. This is in agreement with our results, and explains why, when our data were grouped by elevation and aspect, better dendrochronological parameters could be identified.…”

“…The series of annual tree rings provide information on radial growth rates, and their correlation with vegetation indices is possible because, if the vegetation shows good vigor, it is likely that there are favorable conditions for tree growth and therefore tree rings are wider [11,12]. However, topographic variation in sites and their climatic conditions also influence the degree of correlation between rings and vegetation indices [13]. The Normalized Difference Vegetation Index (NDVI) is a well-known vegetation index that was developed by Rouse et al (1973) and that has been shown to be reliable in representing vegetation vigor variation [12,14,15].…”

Cutting the Greenness Index into 12 Monthly Slices: How Intra-Annual NDVI Dynamics Help Decipher Drought Responses in Mixed Forest Tree Species

“…An alternative recently pursued by the scientific community is the integration of dendroecological data with remote sensing [12][13][14], assuming an interconnection between tree structures explained by the rates of increase recorded in the growth rings and vegetation indices. However, testing these connections has been challenging due to several inconsistencies that require further research [15].…”