A review of light interception in plant stands from leaf to canopy in different plant functional types and in species with varying shade tolerance

Abstract

Changes in the efficiency of light interception and in the costs for light harvesting along the light gradients from the top of the plant canopy to the bottom are the major means by which efficient light harvesting is achieved in ecosystems. In the current review analysis, leaf, shoot and canopy level determinants of plant light harvesting, the light‐driven plasticity in key traits altering light harvesting, and variations among different plant functional types and between species of different shade tolerance are analyzed. In addition, plant age‐ and size‐dependent alterations in light harvesting efficiency are also examined. At the leaf level, the variations in light harvesting are driven by alterations in leaf chlorophyll content modifies the fraction of incident light harvested by given leaf area, and in leaf dry mass per unit area (MA) that determines the amount of leaf area formed with certain fraction of plant biomass in the leaves. In needle‐leaved species with complex foliage cross‐section, the degree of foliage surface exposure also depends on the leaf total‐to‐projected surface area ratio. At the shoot scale, foliage inclination angle distribution and foliage spatial aggregation are the major determinants of light harvesting, while at the canopy scale, branching frequency, foliage distribution and biomass allocation to leaves (FL) modify light harvesting significantly. FL decreases with increasing plant size from herbs to shrubs to trees due to progressively larger support costs in plant functional types with greater stature. Among trees, FL and stand leaf area index scale positively with foliage longevity. Plant traits altering light harvesting have a large potential to adjust to light availability. Chlorophyll per mass increases, while MA, foliage inclination from the horizontal and degree of spatial aggregation decrease with decreasing light availability. In addition, branching frequency decreases and canopies become flatter in lower light. All these plastic modifications greatly enhance light harvesting in low light. Species with greater shade tolerance typically form a more extensive canopy by having lower MA in deciduous species and enhanced leaf longevity in evergreens. In addition, young plants of shade tolerators commonly have less strongly aggregated foliage and flatter canopies, while in adult plants partly exposed to high light, higher shade tolerance of foliage allows the shade tolerators to maintain more leaf layers, resulting in extended crowns. Within a given plant functional type, increases in plant age and size result in increases in MA, reductions in FL and increases in foliage aggregation, thereby reducing plant leaf area index and the efficiency of light harvesting. Such dynamic modifications in plant light harvesting play a key role in stand development and productivity. Overall, the current review analysis demonstrates that a suite of chemical and architectural traits at various scales and their plasticity drive plant light harvesting efficiency. Enhanced light harvesting can be achieved by various combinations of traits, and these suites of traits vary during plant ontogeny.

Do soil fertilization and forest canopy foliage affect the growth and photosynthesis of Amazonian saplings?

“…If sunlight availability is the primary factor restraining sapling growth at the forest understory (Niinemets, 2010;Gommers et al, 2013), increasing nutrient availability should only result in marginal (if any) real enhancement in plant growth. Adaptation to low fertility soils is often accomplished by several mechanisms including enhanced nutrient use effi ciency (e.g.…”

Generality of relationships between leaf pigment contents and spectral vegetation indices in Mallorca (Spain)

“…Changes in chlorophyll a to b ratio can also reflect multiple adjustments in response to light quality and quantity. Ratio of two photosystems (PSI and PSII) as well as the size of light-harvesting antenna complexes modify chlorophyll a to b ratio (Hansen et al 2002;Kitajima and Hogan 2003;Fan et al 2007;Niinemets 2010a). Apart from changes in incident light availability, there is also important light gradient within the leaf, associated both with changes in carotenoid to chlorophyll ratio and chlorophyll a to b ratio (Terashima and Hikosaka 1995 for a review).…”

Interaction between invasive and potentially invasive shrub species does not influence relationships between their ecological success and distance from propagule sources

“…Introduction of coniferous species, which are ecologically alien (according to potential natural vegetation) and in most cases geographically alien, is also an introduction of alien species, which resulted in changes of ecosystem properties (transformers sensu Richardson et al 2000). Although we did not measure this transformation, there are a lot of studies describing how coniferous trees planted in habitats of broadleaved forests affect light conditions (e.g., Knight et al 2008;Niinemets 2010;Mueller et al 2016) or soil chemistry (e.g., Binkley and Valentine 1991;Reich et al 2005;Mueller et al 2012), which generally facilitated invasion of alien species (Obidziński and Symonides 2000;Chmura 2004Chmura , 2014Zerbe and Wirth 2006;Paritsis and Aizen 2008). Both species studied coexist in the arboretum, similar to their native range (Burns and Honkala 1990;Coladonato 1994).…”

“…Due to the longevity and size of woody species (Richardson and Rejmánek 2011;Rejmánek 2014), as well as their strong ability to modify habitat (transformers species sensu Richardson et al 2000), invasive woody species can be especially damaging to the environment. Tree species (both alien and native) influence light availability (Knight et al 2008;Niinemets 2010), mineral nutrient cycling (Augusto et al 2002;Reich et al 2005;Dauer et al 2007;Mueller et al 2012), soil acidity (Binkley and Valentine 1991;Binkley and Giardina 1998;Mueller et al 2012), decomposition rate (Hobbie et al 2006(Hobbie et al , 2010, fine root and leaf lifespans (Withington et al 2006), ectomycorrhizal infections (Dickie et al 2006;Trocha et al 2012), and soil biota (Mueller et al 2015(Mueller et al , 2016. Modifying effects of invasive woody species on habitat was also reported from several biomes across the world (e.g., Vitousek 1990; Ehrenfeld 2003;Stohlgren and Rejmánek 2014;Castro-Díez et al 2014;Menge and Chazdon 2016).…”