Biology subjects

Kotzur, I.

Publications and source records attributed to Kotzur, I..

3 recordsLinked to original sources

bioRxiv2025

Forests and woodlands resistant to drought revealed in remotely sensed foliar moisture content using probabilistic models

Foliar moisture content (FMC) is of primary importance in many biological and ecological processes of forests and woodlands, including herbivory and fire dynamics. The role of FMC, which is the mass of moisture on a dry matter basis, in such processes is increasingly important due to changes in length and severity of climate extremes, like drought. Here we studied the sensitivity of forest and woodland FMC to climatic water balance, i.e. Standardised Precipitation and Evapotranspiration Index (SPEI), across five landscapes in temperate and sub-tropical south-eastern Australia. To do this we used copula-probabilistic modelling, including consideration of drought (i.e. SPEI) length. We used an FMC dataset over eight years of Sentinel-2 satellite reflectance (2015-2023), based on the inversion of a radiative transfer model at 20m resolution. We found the spatial variation of FMC within landscapes to be large and that the spatial variation in response to drought was very large, particularly within the more arid landscapes. The areas of lesser response to extreme drought are revealed to be drought resistant forests and woodlands that are potential climate refugia for animals, and natural breaks in the contiguity of fire fuels.

ecology↗

bioRxiv2025

Diel foliar moisture content recovery time occurs soon after midnight in Eucalyptus species of koala (Phascolarctos cinereus) habitats

Many herbivores are reliant on the foliar moisture content (FMC, the water mass as a percentage of the dry matter mass), of feed tree leaves, which may vary through the diel cycle. This includes koalas (Phascolarctos cinereus), who have heightened reliance on FMC during high temperatures. However, it is unknown how, and to what degree, FMC varies through the 24-hour period. In this experiment we measured live leaf FMC every three hours over the diel period by calibrating a near-infrared spectroscopy (NIRS) model from leaf-surface reflectance, for tree species associated with koala habitat. Coinciding with reflectance measurements, trees in a glasshouse were exposed to normal and extreme climatic conditions including heatwaves and a drought, while collecting concurrent climate variables and soil moisture content. Our analysis of FMC timeseries of glasshouse trees found the diel range of leaf FMC was 23 % dry weight (DW, i.e. 19 % fresh weight) on average, between a minimum and maximum diel range of 10 %DW and 46 %DW, as predicted by an accurate spectral regression model (r2=0.96, RMSE=9.29 %DW). Overall, FMC minima occurred at 13:30 and FMC had recovered to initial levels (7:30) by 1:30 the following morning, though near-recovery levels were reached earlier by 19:30. This result shows that during a single day and night koala tree species may vary the proportion of leaf moisture by about one fifth, on average, and the timing of canopy moisture recovery may discourage foraging in the evening on temporarily dry species, during hot conditions.

ecology↗

bioRxiv2025

Monitoring Forest Foliar Moisture Using Sentinel-2 Reflectance and Radiative Transfer Model Inversion

Foliar moisture content (FMC) of forests canopies is important for understanding biodiversity, including animal habitat quality for forest-dependent fauna and forest fire risk. In this study, we modelled spatiotemporal variation in FMC using optical remote sensing. We inverted the PROSPECT and GEOSAIL Radiative Transfer Models (RTM) on Sentinel-2 satellite reflectance data of 20 m ground resolution to retrieve FMC, and then predicted FMC at sub-continental scales using a random forest (RF) regression emulation of the RTM model. An RTM look-up-table, from earlier work, was filtered by ecological criteria from 24 sites sampled along precipitation and canopy cover gradients and was inverted by using the spectral angle, as a merit function. The RF emulator allowed efficient computation and presentation of an extensive and fine-scale forest FMC data cube of interest in animal, fire and plant ecology. Our RTM-based, predictions of forest and woodland FMC had a root mean square error (RMSE) of 19.9% of dry matter content and explained more than 60% of variance (r2 = 0.62). This represents an improvement over previous models using reflectance data of coarser spatial resolution, particularly in terms of explained variance (r2=0.17 and RMSE=32%). The emulator model achieved similar performance to the RTM with slightly larger error (RMSE = 21.77%) and smaller explained variance (r2 = 0.54). Overall, both models performed best in forests, and woodlands of moderate to high canopy density (> [~]0.75 LAI). This study demonstrates that FMC can be monitored at spatial resolutions that allow intra- or inter-landscape patterns to be resolved surpassing previous capabilities. Index TermsFoliar moisture content, FMC, remote sensing, radiative-transfer, forest, inversion, Sentinel-2, emulator, koala

ecology↗