A field study on solar-induced chlorophyll fluorescence and pigment parameters along a vertical canopy gradient of four tree species in an urban environment

https://doi.org/10.1016/j.scitotenv.2013.07.024Get rights and content

Highlights

  • Urban traffic releases particulate matter which is deposited onto plant surfaces.

  • Tree location can affect deposition of magnetic particles at the whole canopy scale.

  • Tree location rather than sampling height affected some fluorescence yield indices.

  • Traffic generated leaf deposit created a shading effect and decrease of Chl a/b.

  • Fluorescence yield indices show significant correlation with total Chl and Chl a/b.

Abstract

To better understand the potential uses of vegetation indices based on the sun-induced upward and downward chlorophyll fluorescence at leaf and at canopy scales, a field study was carried out in the city of Valencia (Spain). Fluorescence yield (FY) indices were derived for trees at different traffic intensity locations and at three canopy heights. This allowed investigating within-tree and between-tree variations of FY indices for four tree species. Several FY indices showed a significant (p < 0.05) and important effect of tree location for the species Morus alba (white mulberry) and Phoenix canariensis (Canary Island date palm). The upward FY parameters of M. alba, and the upward to downward ratios at 687 and 741 nm for both species, were significantly related to tree location. It was found that not the total chlorophyll (Chl) content, but rather the Chl a/b ratio showed the strongest correlations with several of the indices applied. Chl a/b was lowest at the bottom level of the highest traffic intensity location for both species due to an increased Chl b, indicating a larger light harvesting complex related to Photosystem II (LHCII) as a response to limiting light. The leaf deposits from traffic observed at this sampling location possibly led to a shading effect, resulting further in an adaptive response of the photosynthetic system and subsequent difference of FY indices. This study therefore indicated the importance of the size of LHCII on the fluorescence emission, observed under different traffic generated pollution conditions.

Introduction

In addition to light reflected by vegetation, plants emit a weak far-red radiation better known as chlorophyll (Chl) fluorescence. Typically, Chl fluorescence competes with photosynthesis processes and heat for the use of a leaf's absorbed light. Therefore, Chl fluorescence has the advantage of being highly vegetation specific since it is only emitted by the fluorophores (e.g. Chl a). Reflectance, in contrast, is influenced by any compound that absorbs in the wavelength range observed (e.g. Chl a and b as well as green paint). Whereas reflectance based vegetation indices in remote sensing are measured since the '70s, the technology and methodology for the airborne detection of Chl fluorescence are available only quite recently (Damm et al., 2010, Guanter et al., 2013, Lichtenthaler, 1988, Mcfarlane et al., 1980, Rascher et al., 2009, Stoll et al., 1999). Chl fluorescence is emitted in the spectral range of 650–850 nm and is characterized by two peaks. One peak occurs in the red around 687 nm and the other in the far-red around 741 nm. So far, the red/far-red peak ratio of Chl fluorescence is a parameter often used for the detection of leaf and plant stress since it reveals changes in chlorophyll content due to a partial overlap of the red fluorescence peak with the absorption bands of chlorophyll (D'Ambrosio et al., 1992, Hak et al., 1990, Lichtenthaler and Rinderle, 1988). Moreover, by measuring steady-state fluorescence, changes in physiological stress can be identified before any damage and/or a detectable loss of chlorophyll occurs (Meroni et al., 2009, Van Wittenberghe et al., 2013). Despite this large potential for stress monitoring the fluorescence peak ratio is also known to become quite insensitive to Chl content above a Chl concentration of 300 mg m 2 (Gitelson et al., 1998). However, Agati et al. (1995) pointed out that the utility of the Chl fluorescence peak ratio reaches beyond the simple detection of changes in chlorophyll concentration. Since the peak ratio has been linked to the underlying mechanisms of photosynthesis, it can serve as an instant monitor of CO2 uptake by plants (Damm et al., 2010, Freedman et al., 2002, Rascher et al., 2009).

The use of Chl fluorescence as a tool of plant stress is, therefore, extremely appealing since it can be used in remote sensing applications (Agati et al., 2000, Stoll et al., 1999). Nevertheless, a better understanding of the spectral shape and variability of steady-state fluorescence emission (calculated as fluorescence yield) within whole canopies is required. Especially since different conditions of light or stressors along a tree canopy gradient may influence the photosynthetic apparatus and, therefore, the fluorescence emission, along the vertical gradient. Downward fluorescence, which is seldom taken into account, is the fluorescence that is emitted downward from the lower leaf surface when the incoming light arrives at the upper leaf surface. Due to the longer light path through the leaf, the downward fluorescence signal is shown to be a more sensitive indicator of the leaf's Chl content compared to the upward signal, and is, therefore, a better stress indicator (Van Wittenberghe et al., 2013).

The research presented here had as a main objective to investigate both the importance of within-canopy and between-canopy variation for several fluorescence yield (FY) and pigment parameters. To do so, both the effects of sampling height and tree location were investigated for four tree species. Individuals of each species were selected to represent different traffic exposures in an urban environment. Urban motorized traffic releases large amounts of particulate matter (PM), a complex mix of both liquid and solid particles of organic and inorganic substances suspended in the air. PM deposition on urban vegetation is shown to decrease by height and distance from the source, illustrated by the biomagnetic value of leaves (Hofman et al., in press, Kardel et al., 2012). Therefore, a vertical gradient in traffic pollution exposure may well exist quite regularly. Due to the previous results showing the potential of sun-induced FY parameters of lower canopy leaves as stress indicators of urban traffic (Van Wittenberghe et al., 2013), the following hypotheses were formulated:

  • (i)

    Leaf saturation isothermal remanent magnetization (SIRM) values vary along the canopy and show a decreasing dust deposition from bottom to top;

  • (ii)

    The effect of tree location might be more important than sampling height on FY indices when variation in pollution is larger among trees than within trees, and;

  • (iii)

    Within species, FY indices are rather determined by the photosynthetic pigment system than by leaf structural parameters such as specific leaf area, nitrogen content and leaf thickness.

Section snippets

Field site

The field study was conducted in the city of Valencia (39°28′ N, 0°22′ W, 15 m a.s.l., with 809,267 inhabitants in 2010). Three dicotyledonous deciduous trees Celtis australis L. (European nettle tree), Morus alba L. (White mulberry), Platanus × acerifolia (Aiton) Willd. (London plane), and one monocotyledonous evergreen tree, Phoenix canariensis Chabaud (Canary Island date palm) as well, were selected based on occurrence, morphological leaf characteristics, and absence of diseases. Due to their

Location and sampling height impact on SIRM

The highest SIRM values were obtained at the bottom canopy layer of the C. australis, P. canariensis and M. alba at traffic square (Fig. 2). The palm tree (P. canariensis) had the highest absolute SIRM values of 191 × 10 6 A, while P. × acerifolia showed comparatively low values, without distinct extremes between the three different sampling heights. To obtain an indication of the pollution exposure for each tree, we compared the SIRM values with threshold values based on previous research in the

Conclusions

The hypothesized decrease of magnetic particle deposition from bottom to top was only visible at the traffic location. Deposition of magnetic particulate matter was for all species more influenced by tree location than by sampling height, illustrating a more location dominated pollution level. We also observed that several FY indices showed a higher variation among tree individuals (significant location effect) than within tree individuals (non-significant height effect) for M. alba and P.

Acknowledgments

The research presented in this paper is funded by the Belgian Science Policy Office (BELSPO) in the frame of the STEREO II program-project BIOHYPE (SR/00/131) and partially supported by the Spanish Ministry for Science and Innovation under the project AYA 2010-21432-C02-01. The authors wish to thank Adrian Del Amo and Violeta Ortiz for their field assistance and laboratory analyses. We would also like to acknowledge Claus Buschmann for his helpful literature suggestions.

References (33)

  • G. Agati et al.

    The effect of decreasing temperature up to chilling values on the in vivo F685/F735 chlorophyll fluorescence ratio in Phaseolus vulgaris and Pisum sativum: the role of the Photosystem I contribution to the 735 nm fluorescence band

    Photochem Photobiol

    (2000)
  • L. Alonso et al.

    Sensitivity analysis of the Fraunhofer line discrimination method for the measurement of chlorophyll fluorescence using a field spectroradiometer

  • R. Bassi et al.

    Chlorophyll binding-proteins with antenna function in higher-plants and green-algae

    Photochem Photobiol

    (1990)
  • N. D'Ambrosio et al.

    Increase of the chlorophyll fluorescence ratio F690/F735 during the autumnal chlorophyll breakdown

    Radiat Environ Biophys

    (1992)
  • A. Damm et al.

    Remote sensing of sun-induced fluorescence to improve modeling of diurnal courses of gross primary production (GPP)

    Glob Change Biol

    (2010)
  • F. De Nicola et al.

    Impact of the Mediterranean urban environment on photosynthetic efficiency of Quercus ilex leaves

    Water Air Soil Pollut

    (2011)
  • Cited by (29)

    • Solar-induced chlorophyll fluorescence intensity has a significant correlation with negative air ion release in forest canopy

      2022, Atmospheric Environment
      Citation Excerpt :

      This study shows a close relationship between canopy NAI and SIF, which demonstrates the potential applicability of estimating the dynamic change process of NAI from SIF observations based on the tower base platform and shows that canopy SIF can accurately reflect the dynamic change process of NAI. This is mainly because NAI is closely related to the photosynthetic process, and SIF, as one of the important means of direct measurement of photosynthesis process (Sun et al., 2017; Ryu et al., 2019), responds very quickly to the photosynthesis process, which has proven to be an ideal probe for photosynthesis process (Amoros et al., 2008; Wittenberghe et al., 2014). Thus, SIF and NAI are, allowing changes in NAI to be tracked.

    • Evaluation of drought using satellite solar-induced chlorophyll fluorescence during crop development stage over Xinjiang, China

      2022, Measurement: Journal of the International Measurement Confederation
      Citation Excerpt :

      Overall, approximately 1% of the solar radiation absorbed by plants is discharged by chlorophyll fluorescence. This comparatively trivial volume of energy is measurable by higher phantom definition sensors [43]. Global Ozone Monitoring Experiment 2 (GOME-2) involved MetOp-A/B [19]) has been utilized worldwide for SIF measurement.

    • Re-absorption and scattering of chlorophyll fluorescence in canopies: A revised approach

      2020, Remote Sensing of Environment
      Citation Excerpt :

      The red emission comes from the excited state of PSII and the far-red band from both photosystems I (PSI) and II (PSII) (Agati, 1998; Pfündel, 1998; Franck et al., 2002; Iriel et al., 2014). The fluorescence ratio, calculated as the quotient between maximum intensities in the red and far-red (Fred/ Ffar-red), has been studied to a great extent and has been connected to vegetation health, because of its instant relationship with CO2 uptake (Freedman et al., 2002; Damm et al., 2010; van Wittenberghe et al., 2014; Rossini et al., 2016). Moreover, when light environment suffers changes (e.g. variations in irradiance intensity or spectral distribution) photosynthesis is actively regulated by different mechanisms, which results in protection of the plant from potential damage.

    • Remote sensing of solar-induced chlorophyll fluorescence (SIF) in vegetation: 50 years of progress

      2019, Remote Sensing of Environment
      Citation Excerpt :

      Later, Campbell et al. (2008) showed the contribution of CF to the apparent reflectance of corn leaves in time-resolved laboratory measurements using a solar simulator and blocking filters (which blocked incoming light in the PAR region to prevent fluorescence excitation, similarly to what was done by Zarco-Tejada et al., 2000a). This concept was extended to leaf-based assessments under ambient field conditions using a spectroradiometer coupled with a simple leaf clip (the FluoWat) having blocking filters; this approach has enabled the separation of spectral reflectance and fluorescence across the full emission spectrum for a number of species and physiological conditions (Van Wittenberghe et al., 2014, 2013). New experiments to extract chlorophyll fluorescence signals using the FLD principle with the oxygen absorption feature became possible with spectrometers able to provide sub-nanometer resolutions [Section 5] (Meroni and Colombo, 2006; Pérez-Priego et al., 2005).

    View all citing articles on Scopus
    View full text