Light partitioning among species and species replacement in early successional grasslands

Abstract

Abstract. We studied canopy structure, shoot architecture and light harvesting efficiencies of the species (photon flux captured per unit above-ground plant mass) in a series of exclosures of different age (up to 4.5 yr) in originally heavily grazed grassland in N Japan.Vegetation height and Leaf Area Index (LAI) increased in the series and Zoysia japonica, the dominant in the beginning, was replaced by the much taller Miscanthus sinensis. We showed how this displacement in dominance can be explained by inherent constraints on the above-ground architecture of these two species. In all stands light capture of plants increased with their above-ground biomass but taller species were not necessarily more efficient in light harvesting. Some subordinate species grew disproportionally large leaf areas and persisted in the shady undergrowth. Some other species first grew taller and managed to stay in the better-lit parts of the canopy, but ultimately failed to match the height growth of their neighbours in this early successional series. Their light harvesting efficiencies declined and this probably led to their exclusion. By contrast, species that maintained their position high in the canopy managed to persist in the vegetation despite their relatively low light harvesting efficiencies. In the tallest stands 'later successional' species had higher light harvesting efficiencies for the same plant height than 'early successional' species which was mostly the result of the greater area to mass ratio (specific leaf area, SLA) of their leaves.This shows how plant stature, plasticity in above-ground biomass partitioning, and architectural constraints determine the ability of plants to efficiently capture light, which helps to explain species replacement in this early successional series.Keywords: Canopy structure; Grazing; Light acquisition efficiency; Photon flux; Plant architecture; Plant size inequality; Plasticity.Nomenclature: Makino (1962);Ohwi (1965).Abbreviations: LAI = Leaf area index; LAR = Leaf Area Ratio; LMR = Leaf Mass Ratio; PPFD = Photosynthetically active photon flux density; SLA = Specific Leaf Area.

Winners and losers in herbaceous plant communities: insights from foliar carbon isotope composition in monocultures and mixtures

“…The three species showing a positive relationship between δ 13 C and transmitted light are among the low-growing subordinate species unable to establish a clear dominance in multispecies communities. Plants' abilities to capture light have been proposed to be determined in part by their stature and in part by their plasticity and biomass allocation (Anten & Werger 1996;Werger et al 2002). As lesser light availability leads to lower photosynthetic rates (Long et al 1994;Hikosaka et al 2004), we conclude that the observed correlation between δ 13 C and light availability is indicative of subordinate species being overshadowed by individuals of dominant, larger species.…”

“…Clearly, multiple factors are likely to contribute to light capturing abilities: F. ovina and R. acris, identified as clear losers in multispecies communities, did not show any correlation between δ 13 C and transmitted light. These species may be able to compensate for low light availability by greater light harvesting efficiencies, thus maintaining photosynthetic rates in mixed plant communities similar to those observed in monocultures (Anten & Hirose 1999;Werger et al 2002).…”

Does complementary resource use enhance ecosystem functioning? A model of light competition in plant communities

“…The model is a spatially implicit, height-structured model of competition for light. Complex, quantitative physiological models that incorporate light interception, canopy structure and photosynthesis have recently been developed and applied to experimental data (Anten & Hirose 1999Werger et al 2002;see Anten 2005;Hirose 2005 for reviews). Here we present a simpler model that enables us to obtain analytical results for multispecies communities while taking into account the asymmetric effect of shading of small individuals by larger individuals.…”

“…As discussed above, positive competitive relaxation occurs when species in a mixture experience less severe competition on average than in monoculture, and thus the conditions under which functional complementarity takes place should greatly overlap with the conditions under which stable coexistence occurs (Loreau 2004). Furthermore, tradeoffs are a key mechanism for multispecies coexistence (Kohyama 1993;Tilman & Pacala 1993;Anten & Hirose 1999;Werger et al 2002;Anten 2005). Thus, it seems highly probable that in natural ecosystems, in which one or more coexistence mechanisms operate, the competitive imbalance effect, and hence the corresponding selection effect, tends to be suppressed, and the complementarity effect dominates.…”

Nitrogen addition stimulated compensatory growth responses to clipping defoliation in a Northern Tibetan alpine meadow

“…At present, there are many studies on the mechanism of plant over-compensation after clipping defoliation (Belsky, 1986;Ferraro & Oesterheld, 2002;McNaughton, 1979). It is generally thought that clipping defoliation can produce more tillers (Heckathorn & Delucia, 1996;Werger et al, 2002) or change resource allocation patterns by stimulating plant photosynthesis to promote plant growth (Herrero-Jáuregui et al, 2016). In addition to the impacts of clipping intensity on forage compensatory growth, resource availability is also one of the important factors that affect plant compensatory growth (Sun, Ma, & Lu, 2018;Sun et al, 2014;Tuffa et al, 2017;Zhao et al, 2008).…”