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ABSTRACT The northeastern slope of the Andes is an area of high diversity of ferns and lycophytes. In this study we assessed the diversity patterns of ferns and lycophytes in ten 250 m x 2 m plots installed at three elevational zones, from 418 to 3447 m.a.s.l., in the Napo province of Ecuador. Floristic diversity was measured using Hill numbers and by partitioning species diversity. Three functional diversity indices were calculated from a set of five leaf traits and weighted by species abundance: functional richness (FRic), evenness (FEve) and divergence (FDiv). To disentangle functional diversity from species richness, the standardized effect size (SES) of each index was also calculated. We recorded 148 species, Polypodiaceae and Dryopteridaceae being the most representative families. Species richness continuously decreased with elevation. Floristic composition was highly heterogeneous among elevation zones, with total species turnover found between 1500 and 2000 m.a.s.l. SES-FDiv and SES-FEve were higher than the null expectation for plots at mid-elevations, suggesting that deterministic mechanisms, such as biotic or abiotic filters, could explain assemblage composition at these sites. However, SES-FEve, SES-FRic and SES-FDiv did not differ from the null expectations at low and high elevation sites, suggesting the predominance of a stochastic process. By combining floristic and functional diversity, we were able to infer the observed community patterns with the resource-use strategies of fern and lycophytes in a mountain area, an approach that can be used to understand how assemblages might react to changing environmental conditions.

Background and Aims Knowledge of plant resource acquisition strategies is crucial for understanding the mechanisms mediating the responses of ecosystems to external nitrogen (N) input. However, few studies have considered the joint effects of above-ground (light) and below-ground (nutrient) resource acquisition strategies in regulating plant species responses to N enrichment. Here, we quantified the effects of light and non-N nutrient acquisition capacities on species relative abundance in the case of extra N input. Methods Based on an N-manipulation experiment in a Tibetan alpine steppe, we determined the responses of species relative abundances and light and nutrient acquisition capacities to N enrichment for two species with different resource acquisition strategies (the taller Stipa purpurea , which is colonized by arbuscular mycorrhizal fungi, and the shorter Carex stenophylloides , which has cluster roots). Structural equation models were developed to explore the relative effects of light and nutrient acquisition on species relative abundance along the N addition gradient. Key Results We found that the relative abundance of taller S. purpurea increased with the improved light acquisition along the N addition gradient. In contrast, the shorter C. stenophylloides , with cluster roots, excelled in acquiring phosphorus (P) so as to elevate its leaf P concentration under N enrichment by producing large amounts of carboxylate exudates that mobilized moderately labile and recalcitrant soil P forms. The increased leaf P concentration of C. stenophylloides enhanced its light use efficiency and promoted its relative abundance even in the shade of taller competitors. Conclusions Our findings highlight that the combined effects of above-ground (light) and below-ground (nutrient) resources rather than light alone (the prevailing perspective) determine the responses of grassland community structure to N enrichment. [ABSTRACT FROM AUTHOR]

The data presented in this article describe 21 species that can be found in banana cropping systems: 17 cover crops species, 2 spontaneous species and 2 cultivars of banana. The cover crop species belongs mainly to Fabaceae family, but also to Poaceae, Euphorbiacea and Asteraceae. Four repetition of each species were cultivated individually, in the field, under non-limiting conditions. 40 variables were measured on whole plant, leaves and roots, at flowering or after six months of growth for longer cycle species. This dataset is made available to provide data on these species, enable comparisons between datasets and meta-analysis on cover crop or on species presented in arable fields. The data presented in this article were used in the research articles entitled “Trait-based characterisation of cover plants' light competition strategies for weed control in banana cropping systems in the French West Indies” (Tardy et al. 2015) and “Trait-based characterization of soil exploitation strategies of banana, weeds and cover plant species” (Tardy et al. 2017).

Species niches are expected to differ between different functional groups and between species with different functional traits. However, it is still unclear how functional traits contribute to niche separation between species coexisting in a community and between sites along environmental gradients., We studied seasonal changes in light partitioning among coexisting species belonging to different functional groups in moorland plant communities at different altitudes. We estimated the lifetime light absorption per unit invested leaf biomass (ΦLleafmass) as a measure of the benefit/cost ratio of light acquisition., Evergreen species absorbed more light in spring, whereas deciduous species absorbed more light in summer. A similar tradeoff was also found between short and tall species within each functional group. As a result, evergreen and shorter species had comparable ΦLleafmass values to those of deciduous and taller species. Evergreen species had higher ΦLleafmass at higher altitudes relative to deciduous species, suggesting that evergreen habit is more advantageous for the lifetime light interception at higher altitudes., Our results demonstrate that phenological tradeoffs for light partitioning can contribute to the coexistence of species with different functional traits. Our results also reveal that the most advantageous traits differ depending on environment. [ABSTRACT FROM AUTHOR]

In a dense stand, individuals compete with each other for resources, especially for light. Light availability decreases with increasing depth in the canopy, thus light competition becoming stronger with time in the vegetative phase. In the reproductive phase, on the other hand, leaves start senescing, and the light environment, particularly of smaller individuals, will be improved. To study the effect of change in light climate on reproduction of individuals, we established an experimental stand of an annual, Xanthium canadense, and assessed temporal changes in whole plant photosynthesis through the reproductive phase with particular reference to light availability of individuals. At flowering, 83% of individuals were still alive, but only 27% survived to set seeds. Most of the individuals that died in the reproductive phase were smaller than those that produced seeds. Individuals that died at the early stage of the reproductive phase had a lower leaf to stem mass ratio, suggesting that the fate of individuals was determined partly by the pattern of biomass allocation in this period. At the early stage of the reproductive phase, leaf area index (LAI) of the stand was high and larger individuals had higher whole plant photosynthesis than smaller individuals. Although light availability at later stages was improved with reduction in LAI, whole plant photosynthesis was very low in all individuals due to a lower light use efficiency, which was caused by a decrease in photosynthetic N use efficiency. We conclude that light competition was still strong at the early stage of the reproductive phase and that later improvement of light availability did not ameliorate the photosynthesis of smaller individuals. [ABSTRACT FROM AUTHOR]

The importance of light acquisition and utilization by individuals in intraspecific competition was evaluated by determining growth and photosynthesis of individual plants in a dense monospecific stand of an annual, Xanthium canadense. Photosynthesis of individual plants in the stand was calculated using a canopy photosynthesis model in which leaf photosynthesis was assumed to be function of leaf nitrogen content and light availability. The estimated photosynthetic rates of individuals were strongly correlated with the measured growth rates. Photosynthetic rates per unit aboveground mass (RPR, relative photosynthetic rate) increased with increasing aboveground mass, suggesting asymmetric (one-sided) competition in the stand. However, larger individuals had similar RPRs, suggesting symmetric (two-sided) competition. These results were consistent with the observation that size inequality over the whole stand increased with growth, but it remained stable among the larger individuals. The RPR of an individual was calculated as the product of absorbed photon flux per unit aboveground mass (Φmass) and light use efficiency (LUE, photosynthesis per unit absorbed photon flux). Φmass indicates the efficiency of light acquisition, and was higher in larger individuals in the stand, while LUE was highest in individuals with intermediate aboveground mass. LUE depends on leaf nitrogen content. At an early stage, leaf nitrogen contents of smaller individuals were similar to those that maximize LUE. Light availability to smaller individuals decreased as they grew, while their nitrogen contents did not change markedly, which decreased their LUE. We concluded that asymmetric competition among individuals in the stand resulted mainly from lower efficiencies in both light acquisition and light use by smaller individuals. [ABSTRACT FROM AUTHOR]