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Publications
Publications (38)
- Solar induced chlorophyll a Fluorescence (SIF), which is distributed over a relatively broad (~200 nm) spectral range, is a signal intricately connected to the efficiency of photosynthesis and is now observable from space. Variants of the Fraunhofer Line Depth/Discriminator (FLD) method are used as the basis of retrieval algorithms for estimating...
The intensity and spectral properties of solar-induced chlorophyll fluorescence (SIF) carry valuable information on plant photosynthesis and productivity, but are also influenced by leaf and canopy structure. Physically based models provide a quantitative means to investigate how SIF intensity and spectra propagate and scale from the photosystem to...
Drought‐related die‐off events have been observed throughout Europe in Scots pine ( Pinus sylvestris L.). Such events are exacerbated by carbon starvation that is, an imbalance of photosynthetic productivity and resource usage. Recent evidence suggests that optically measurable photosynthetic pigments such as chlorophylls and carotenoids respond to...
Physical model simulations have been widely utilized to simulate the reflectance of vegetation canopies. Such simulations can be used to estimate key biochemical and physical vegetation parameters, such as leaf chlorophyll content (LCC), leaf area index (LAI), and leaf inclination angle (LIA) from remotely sensed data via model inversion. In simula...
Vegetation indices (VIs) related to plant greenness have been studied extensively for the remote detection of foliar nitrogen content. Yet, the potential of chlorophyll fluorescence (ChlF) and photoprotection-based indices such as the photochemical reflectance index (PRI) or the chlorophyll/carotenoid index (CCI) for the detection of a wide range o...
The plant area index (PAI) is a structural trait that succinctly parametrizes the foliage distribution of a canopy and is usually estimated using indirect optical techniques such as digital hemispherical photography. Critically, on‐the‐ground photographic measurements forgo the vertical variation of canopy structure which regulates the local light...
The use of remote sensing in agriculture is expanding due to innovation in sensors and platforms. Uncrewed aerial vehicles (UAVs), CubeSats, and robot mounted proximal phenotyping sensors all feature in this drive. Common threads include a focus on high spatial and spectral resolution coupled with the use of machine learning methods for relating ob...
For decades, the dynamic nature of chlorophyll a fluorescence (ChlaF) has provided insight into the biophysics and ecophysiology of the light reactions of photosynthesis from the subcellular to leaf scales. Recent advances in remote sensing methods enable detection of ChlaF induced by sunlight across a range of larger scales, from using instruments...
Solar-induced Fluorescence (SIF) has an advantage over greenness-based Vegetation Indices in detecting drought. This advantage is the mechanistic coupling between SIF and Gross Primary Productivity (GPP). Under water stress, SIF tends to decrease with photosynthesis, due to an increase in non-photochemical quenching (NPQ), resulting in rapid and/or...
The escape probability of Solar-induced chlorophyll fluorescence (SIF) can be remotely estimated using reflectance measurements based on spectral invariants theory. This can then be used to correct the effects of canopy structure on canopy-leaving SIF. However, the feasibility of these estimation methods is untested in heterogeneous vegetation such...
Leaf angle distribution (LAD) is a key canopy structural parameter, playing an important role in light transfer. LAD can be estimated from fixed point of view photography, however this is time consuming and spatially limited. Recently, Terrestrial LiDAR Scanning (TLS) has been used to estimate LAD through 3D canopy space. The downside of TLS it is...
TO READ AND DOWNLOAD THIS PREPRINT; CLICK ON THE DOI, WHICH SHOULD TAKE YOU TO THE EARTHARXIV (https://doi.org/10.31223/osf.io/eayph).
The use of remote sensing in agriculture is expanding due to innovation in sensors and platforms. Drones, high resolution instruments on CubeSats, and robot mounted proximal phenotyping sensors all feature in this...
When freezing occurs in trees in the autumn living cells are able to withstand the rapid dehydration that they experience due to the chemical properties of ice that fills apoplastic spaces. Elasticity and hydraulic permeability of living tissue are important properties influencing the frost tolerance of trees, because of their effects on how rapidl...
Solar-induced chlorophyll fluorescence (SIF) has been shown to be a suitable remote sensing proxy of photosynthesis at multiple scales. However, the relationship between fluorescence and photosynthesis observed at the leaf level cannot be directly applied to the interpretation of retrieved SIF due to the impact of canopy structure. We carried out a...
Chlorophyll a fluorescence (ChlF) is closely related to photosynthesis and can be measured remotely using multiple spectral features as solar‐induced fluorescence (SIF). In boreal regions, SIF shows particular promise as an indicator of photosynthesis; in part because of the limited variation of seasonal light absorption in these ecosystems. Season...
Successful measurements of chlorophyll fluorescence (ChlF) spectral properties (typically in the wavelength range of 650–850 nm) across plant species, environmental conditions, and stress levels are a first step towards establishing a quantitative link between solar-induced chlorophyll fluorescence (SIF), which can only be measured at discrete ChlF...
Solar induced chlorophyll fluorescence has been shown to be increasingly an useful proxy for the estimation of gross primary productivity (GPP), at a range of spatial scales. Here, we explore the seasonality in a continuous time series of canopy solar induced fluorescence (hereafter SiF) and its relation to canopy gross primary production (GPP), ca...
Evergreen plants in boreal biomes undergo seasonal hardening and dehardening adjusting their photosynthetic capacity and photoprotection; acclimating to seasonal changes in temperature and irradiance. Leaf epidermal ultraviolet (UV)-screening by flavonols responds to solar radiation, perceived in part through increased ultraviolet-B (UV-B) radiatio...
At high northern latitudes in the boreal forest, winter precipitation in the form of snow has decreased and is predicted to continue to do so in the future (Jylhä et al., 2008). Reduced snow cover exposes plants to temperature fluctuations at may delay the spring recovery of photosynthesis. Such a change has potentially negative consequences for ne...
Key message
Subarctic plants in summer (subjected to continuous light) showed photosynthetic pigment contents mainly driven by PPFD (unrelated to day/night cycles) and a xanthophyll cycle responsiveness to PPFD exacerbated during night-times.
Abstract
Composition and content of photosynthetic pigments is finely tuned by plants according to a subtl...
Solar induced chlorophyll a fluorescence (SIF) has been shown to be an excellent proxy of photosynthesis at multiple scales. However, the mechanical linkages between fluorescence and photosynthesis at the leaf level cannot be directly applied at canopy or field scales, as the larger scale SIF emission depends on canopy structure. This is especially...
Leaf Optical Properties (LOPs) convey information relating to temporally dynamic photosynthetic activity and biochemistry. LOPs are also sensitive to variability in anatomically related traits such as Specific Leaf Area (SLA), via the interplay of intra-leaf light scattering and absorption processes. Therefore, variability in such traits, which may...
Accurate temporal and spatial measurements of leaf optical traits (i.e., absorption, reflectance and transmittance) are paramount to photosynthetic studies. These optical traits are also needed to couple radiative transfer and physiological models to facilitate the interpretation of optical data. However, estimating leaf optical traits in leaves wi...
Figure S1. Temperature inside enclosure immediately before closure, S200 (state of photosynthetic acclimation), monoterpene emission rate, CO2 exchange rate and maximum quantum yield of PSII (φPmax) during spring recovery periods 2009 (a), 2010 (b), 2012 (c) and 2013 (d,e). The y‐axis for temperature, S
200 and CO2 exchange rate is on the left side...
Emissions of biogenic volatile organic compounds (BVOC) by boreal evergreen trees have strong seasonality, with low emission rates during photosynthetically inactive winter and increasing rates towards summer. Yet, the regulation of this seasonality remains unclear. We measured in situ monoterpene emissions from Scots pine shoots during several spr...
Chlorophyll a fluorescence (ChlF) has been used for decades to study the organization, functioning, and physiology of photosynthesis at the leaf and subcellular levels. ChlF is now measurable from remote sensing platforms. This provides a new optical means to track photosynthesis and gross primary productivity of terrestrial ecosystems. Importantly...
Following outplanting, trees undergo a period of stress, referred to as transplant shock. Tree mortality rates are known to increase during this period, so monitoring the effects of transplant shock is key to improving the future survival rates of outplanted trees. Leaf reflectance spectra, measured by field spectrometry, can be used to derive refl...