Workshop Image Gallery

Changes in water content drive forest changes at diurnal (inner ring), seasonal (middle ring), and decadal (outer ring) timescales. Across decadal-scale responses, declines in VWC can lead to mortality and/or fire. VWC will also increase in concert with successional dynamics. Across dry and wet seasons, forest VWC evolves through both phenology and de-/rehydration. Lastly, VWC has a strong diurnal cycle driven by the diurnal cycle of ET.

Image credit: Keck Institute for Space Studies / Kara Skye Gibson and Victor Leshyk.

Vertical distributions of tissue-specific water retention properties (RWC – Ψ curves), biomass, and sensor penetration depth determine remotely sensed water content and its temporal variation. Several hypothesized curves delineating gradients of capacitance, defined as the change in relative water content relative to that of water potential (C = ΔRWC/ΔΨ) are shown. Therefore, temporal variation in remotely sensed metrics of VWC will be determined not only by temporal variation in Ψ, but by differences in the exchangeability of water in response to changes in Ψ across different plant tissues, and the response of sensor penetration depth to changes in water content.

Image credit: Keck Institute for Space Studies / Kara Skye Gibson and Victor Leshyk.

Microwave remote sensing is able to observe water content in forests. The canopy layers represented in each measurement (the penetration depth) varies across different microwave frequency bands (and thus different wavelengths), as shown through different red and blue electromagnetic waves. Observations represent deeper areas of the canopy as wavelengths increase (and frequencies decrease) from Ku-band across X-, C-, and L-bands to P-band. Higher frequencies are most sensitive to leaves and branches while lower frequencies also have increasing sensitivity to trunks and soils.

Image credit: Keck Institute for Space Studies / Kara Skye Gibson and Victor Leshyk.