A Comparison of in situ Leaf Photosynthesis and Chlorophyll Fluorescence at the Top Canopies in Rainforest Mature Trees

Abstract

The top canopy leaves of mature trees are exposed to high solar radiation, regardless of whether they are climax or pioneer trees. We compared leaf physiology and morphology at the top canopies of a climax Dipterocarpus cornutus tree and a pioneer Macaranga gigantea tree in a rainforest, East Kalimantan. The mass-based maximum net photosynthetic rate (Pn max ) and the nitrogen-based Pn max for M. gigantea were 2.3-fold and 1.6-fold greater than those for D. cornutus, respectively. However, no significant difference in the area-based Pn max between the two species was found, because of its thick lamina of D. cornutus. The dependency of net photosynthetic rate and stomatal conductance on leaf-to-air vapor pressure deficit did not differ between the two trees. Under high irradiance, effective quantum yield (∆F/Fm') of photosystem II (PSII), photochemical quenching (qP), non-photochemical quenchings (qN and NPQ), and electron transport rate in PSII were significantly higher in M. gigantea than in D. cornutus. Under moderate irradiance, a hysteresis in chlorophyll fluorescence parameters between the morning and afternoon was found especially in D. cornutus, i.e., the fraction of qP within the PSII centers decreased and that of excess energy increased in the afternoon. These data indicate low lightuse capacity and high susceptibility for excess light energy of PSII in D. cornutus. The leaf properties were different between the mature climax and pioneer trees, even if their leaves grew under similar light environments at the top canopies.

Comparing the ecophysiology of four tree species growing in the coastal temperate rainforests of Prince William Sound, Alaska

“…White and Critchley 1999;Rascher et al 2000), they nonetheless provide useful information especially when doing comparative studies such as this. Trends in fluorescence parameters measured in trees growing in different light conditions, such as those in the present study, were similar to those reported by others (e.g., Boardman 1977;Demmig-Adams and Adams 1992;Geßler et al 2005;Ishida et al 2005) and in photoacclimation studies on phytoplankton (e.g., Quigg et al , 2006 and macroalgae and seagrasses (Quigg et al 2008). Generally, ETR max and I k were greatest in trees growing in full sun and lowest in shade trees, while photoprotective down regulation was absent in trees, growing in full sun, and progressively greater in partial shade to shade plants (Table 4).…”

“…Dissipation of excess light (qN or NPQ) and light-use efficiencies (qP or DF/F 0 m ) are important for avoiding photoinhibition. Values of qP and qN reported in this study (Table 5) were similar to those measured by Ishida et al (2005) for Macaranga gigantea and Dipterocarpus cornutus rainforest trees located in the Bukit Soeharto Education Forest (East Kalimantan, Indonesia). These authors measured qP and qN in the range 0.889-0.976 and 0.283-0.6, respectively.…”

“…Fluorescence quenching coefficients are strongly dependent on the location of leaves within a canopy (Demmig-Adams and Adams 1992; Ishida et al 2005). Shade-acclimated leaves have low capacities not only for ETR (Table 4) but also for photoprotective responses such as thermal energy dissipation (Figs.…”

Perspective: Improving the accuracy of plant phenology observations and land-cover and land-use detection by optical satellite remote-sensing in the Asian tropics

“…To accurately evaluate the spatiotemporal variation of the heat, water, and carbon cycles and biodiversity in the tropics, and to understand the sensitivity of vegetation to environmental change and succession, accurate classification of PFTs and detection of their interannual variation are needed. For instance, traits of photosynthesis and evapotranspiration differ among ecosystems and tree species in the tropics (Ishida et al, 2005;Kenzo et al, 2004Kenzo et al, , 2006Kenzo et al, , 2011Kenzo et al, , 2015. The improved classification of PFTs and discrimination of tree species based on photosynthesis, leaf traits, and leaf and canopy structures are important tasks because these traits help to account for the sensitivity of the flowering, leaf-flush, and leaf-fall phenology and leaf longevity to environmental changes and succession.…”