Changes In Plant Functional Traits Research Articles

Effects of changing precipitation and warming on functional traits of zonal Stipa plants from Inner Mongolian grassland

The mechanisms driving changes in dominant plant species are the key for understanding how grassland ecosystems respond to climate change. In this study, we examined plant functional traits (morphological characteristics: plant height, leaf area, and leaf number; biomasses: aboveground, belowground, and total; and growth indices: root-to-shoot ratio, specific leaf area, and leaf mass ratio) of four zonal Stipa species (S. baicalensis, S. bungeana, S. grandis, and S. breviflora) from Inner Mongolian grassland in response to warming (control, +1.5, +2.0, +4.0, and +6.0?), changing precipitation (-30%, -15%, control, +15%, and +30%), and their combined effects via climate control chambers. The results showed that warming and changing precipitation had significant interactive effects, different from the accumulation of single-factor effects, on functional traits of Stipa species. The correlation and sensitivity of different plant functional traits to temperature and precipitation differed. Among the four species, the accumulation and variability of functional traits had greater partial correlation with precipitation than temperature, except for leaf number, leaf area, and specific leaf area, in S. breviflora, S. bungeana, and S. grandis. For S. baicalensis, the accumulation and variability of plant height, aboveground biomass, and root-to-shoot ratio only had significant partial correlation with precipitation. However, the variability of morphological characteristics, biomasses, and some growth indices, was more sensitive to temperature than precipitation in S. bungeana, S. grandis, and S. breviflora—except for aboveground biomass and plant height. These results reveal that precipitation is the key factor determining the growth and changes in plant functional traits in Stipa species, and that temperature mainly influences the quantitative fluctuations of the changes in functional traits.

Specific leaf area and hydraulic traits explain niche segregation along an aridity gradient in Mediterranean woody species

Despite growing evidence of changes in plant functional traits (FT) along environmental gradients, the way they shape species niches (i.e. how they alternatively influence the limits, width and environmental optimums of species niche) remains only partially understood. Thus, Species Distribution Models were developed and evaluated using distribution data from the Spanish Forest Inventory for 21of the most common Mediterranean woody species, and used to derive different environmental characteristics of species niche, which were then correlated against species-specific values of 14 FT and combinations of relatively orthogonal FT. Species leaf traits, and in particular Specific Leaf Area (SLA), were highly correlated with species niche characteristics regarding aridity (especially with the more arid limit). Hydraulic traits, i.e. the water potential at which a species loses 50% of xylem hydraulic conductivity due to cavitation (PLC50), and species hydraulic safety margins (SM), were better correlated with species aridity niche optimums. Overall, the best model fits, particularly regarding species’ optimum and maximum aridity limit, were obtained when SLA and hydraulic traits (either PLC50 or SM) were used in combination. The study shows how in the Mediterranean region a single trait may be able to explain broad differences in species distributions, but also that the coordination of relatively independent traits achieves a more accurate representation of their environmental limits, particularly at the dry end of the species’ range. The approach used in this study relies on the physiological limits of a species and, to a certain extent, on the mechanisms behind them, adding robustness and accuracy to predict species distribution and mortality under climate change scenarios.

Hunting alters seedling functional trait composition in a Neotropical forest.

Defaunation alters trophic interactions between plants and vertebrates, whichmay disrupt trophic cascades, thereby favoring a subset of plant species and reducing diversity. If particular functional traits characterize the favored plant species,.then defaunation may alter community-wide patterns of functional trait composition. Changes in plant functional traits occurring with defaunation may help identify the species interactions affected by defaunation and the potential for other cascading effects of defaunation. We tested the hypotheses that defaunation would (1) disrupt seed dispersal, thereby favoring species whose dispersal agents are not affected (e.g., small birds, bats, and abiotic agents), (2) reduce seed predation, thereby favoring larger-seeded species, and (3) reduce herbivory, thereby favoring species with lower leaf mass per area (LMA), leaf toughness, and wood density. We examined how these six traits responded to vertebrate defaunation caused by hunters or by experimental exclosures among more than-30 000 woody seedlings in a lowland tropical moist forest. Exclosures reduced terrestrial frugivores, granivores, and herbivores, while hunters also reduced volant and arboreal frugivores and granivores. The comparison of exclosures and hunting allowed us to parse the impacts of arboreal and volant species (reduced by hunters only) and terrestrial species (reduced by both hunters and exclosures). The loss of terrestrial vertebrates alone had limited effects on plant trait composition. The additional loss of volant and arboreal vertebrates caused significant shifts in plant species composition towards communities with more species dispersed abiotically, including lianas and low wood-density tree species, and fewer species dispersed by large vertebrates. In contrast to previous studies, community seed mass did not decline significantly in hunted sites. Our exclosure results suggest this is because reducing seed predators disproportionately benefits large-seeded species,.partially compensating for the reduction of seed dispersers at hunted sites. Our result9sdemonstrate that decreased seed dispersal and seed predation are important determinants of seedling community compositional change as a consequence of defaunation. Defaunation may also negatively impact carbon storage in tropical forests, by favoring lianas and low wood density tree species.

Plant trait variation along an altitudinal gradient in mediterranean high mountain grasslands: controlling the species turnover effect.

Assessing changes in plant functional traits along gradients is useful for understanding the assembly of communities and their response to global and local environmental drivers. However, these changes may reflect the effects of species composition (i.e. composition turnover), species abundance (i.e. species interaction), and intra-specific trait variability (i.e. species plasticity). In order to determine the relevance of the latter, trait variation can be assessed under minimal effects of composition turnover. Nine sampling sites were established along an altitudinal gradient in a Mediterranean high mountain grassland community with low composition turnover (Madrid, Spain; 1940 m–2419 m). Nine functional traits were also measured for ten individuals of around ten plant species at each site, for a total of eleven species across all sites. The relative importance of different sources of variability (within/between site and intra-/inter-specific functional diversity) and trait variation at species and community level along the considered gradients were explored. We found a weak individual species response to altitude and other environmental variables although in some cases, individuals were smaller and leaves were thicker at higher elevations. This lack of species response was most likely due to greater within- than between-site species variation. At the community level, inter-specific functional diversity was generally greater than the intra-specific component except for traits linked to leaf element content (leaf carbon content, leaf nitrogen content, δ13C and δ15N). Inter-specific functional diversity decreased with lower altitude for four leaf traits (specific leaf area, leaf dry matter content, δ13C and δ15N), suggesting trait convergence between species at lower elevations, where water shortage may have a stronger environmental filtering effect than colder temperatures at higher altitudes. Our results suggest that, within a vegetation type encompassing various environmental gradients, both, changes in species abundance and intra-specific trait variability adjust for the community functional response to environmental changes.

Changes in plant functional traits and water use in Atlantic rainforest: evidence of conservative water use in spatio-temporal scales

Key message Relationship between sap flow and functional traits changes with altitude and changes in water availability can impose a conservative water use in woody species of tropical rainforest.

Topography related habitat associations of tree species traits, composition and diversity in a Chinese tropical forest

Several studies have demonstrated that topography, as a proxy for resource availability, plays an important role in shaping tree species distribution patterns in tropical forests. Here we take a functional approach by assessing changes in plant functional traits along topographical gradients in a 20-ha forest dynamics plot in Xishuangbanna, southern Yunnan, China. We hypothesized that observed changes in trait composition and diversity along the topographic gradient should reflect tree life-history strategies linked to resource (water and nutrients) availability. We measured and compiled data of the maximum height, leaf area, seed mass and wood density of 334 tree species in 500 subplots (20×20m). We found that species composition and diversity changed significantly along the topographical gradient. This change was accompanied by increasing community average seed mass and wood density, and decreasing leaf area and tree maximum height with higher elevations and steeper slopes. Higher slopes and ridges were being dominated by tree communities that, possibly due to environmental filtering, converged on a combination of traits characteristic of slow growth and low turn-over. Lower slopes and valleys, on the other hand, were dominated by tree communities that showed high trait evenness and divergence, and tree species characterized by traits indicative of fast growth and turn-over, i.e. competition for resources may be responsible for complementary trait combinations and resource use in this habitat type. Our study shows that functional traits can provide a mechanistic understanding of the processes shaping tropical tree community assembly along topographical gradients and supplements information obtained using species composition and diversity data. Some practical outcomes of our study include: (1) plant species compositional trends in tropical forests can be predicted with GIS technology, focusing on topographical gradients; (2) forest communities on ridges may become more dominant and expand in the future due to increasing drought severity; (3) a considerable number of tropical tree species may currently be under threat of local extinction due to topographically biased deforestation trends and (4) trait based survey approaches improve our understanding of the mechanisms behind species compositional trends.