Interactive effects between plant functional types and soil factors on tundra species diversity and community composition

Abstract

Plant communities are coupled with abiotic factors, as species diversity and community composition both respond to and influence climate and soil characteristics. Interactions between vegetation and abiotic factors depend on plant functional types (PFT) as different growth forms will have differential responses to and effects on site characteristics. However, despite the importance of different PFT for community assembly and ecosystem functioning, research has mainly focused on vascular plants. Here, we established a set of observational plots in two contrasting habitats in northeastern Siberia in order to assess the relationship between species diversity and community composition with soil variables, as well as the relationship between vegetation cover and species diversity for two PFT (nonvascular and vascular). We found that nonvascular species diversity decreased with soil acidity and moisture and, to a lesser extent, with soil temperature and active layer thickness. In contrast, no such correlation was found for vascular species diversity. Differences in community composition were found mainly along soil acidity and moisture gradients. However, the proportion of variation in composition explained by the measured soil variables was much lower for nonvascular than for vascular species when considering the PFT separately. We also found different relationships between vegetation cover and species diversity according the PFT and habitat. In support of niche differentiation theory, species diversity and community composition were related to edaphic factors. The distinct relationships found for nonvascular and vascular species suggest the importance of considering multiple PFT when assessing species diversity and composition and their interaction with edaphic factors. Synthesis: Identifying vegetation responses to edaphic factors is a first step toward a better understanding of vegetation–soil feedbacks under climate change. Our results suggest that incorporating differential responses of PFT is important for predicting vegetation shifts, primary productivity, and in turn, ecosystem functioning in a changing climate.

Plant trait response of tundra shrubs to permafrost thaw and nutrient addition

“…Plant growth in high-latitude ecosystems is highly nutrient-limited (Billings and Mooney, 1968;Shaver and Chapin, 1980;Epstein et al, 2000). Nutrient addition releases shrubs from this limitation and promotes their growth and biomass production (Chapin and Shaver, 1996;DeMarco et al, 2014;Iturrate-Garcia et al, 2017). Nutrient addition released shrubs from growth limitation as evidenced by the plant trait changes we found, such as greater height, SLA and leaf nutrient concentration (Hudson et al, 2011;Reich, 2014).…”

“…The slightly acidic soil (pH 6) has a silty-clay texture and high organic matter content (Blok et al, 2010;Bartholomeus et al, 2012). The soil organic matter decomposition is low as indicated by the high average carbon-to-nitrogen ratio (22) and low cellulose-to-lignin ratio (2.4) (Iturrate-Garcia et al, 2016). During the mid-growing season, the mean active layer thickness is 35 cm, increasing to about 50 cm at the end of the season.…”

Water as a resource, stress and disturbance shaping tundra vegetation

“…Water as a resource proved to be the most important water aspect for the three taxonomic groups. Due to the distinct life histories and physiology of the three taxonomical groups, they have different adaptations to cope with local water conditions (Iturrate‐Garcia et al ). Generally, vascular plants are stronger competitors than mosses, but in both extremes of the soil moisture gradient, these roles may be reversed (Iturrate‐Garcia et al ).…”

“…Due to the distinct life histories and physiology of the three taxonomical groups, they have different adaptations to cope with local water conditions (Iturrate‐Garcia et al ). Generally, vascular plants are stronger competitors than mosses, but in both extremes of the soil moisture gradient, these roles may be reversed (Iturrate‐Garcia et al ). For example, mosses dominate in nearly water‐logged conditions, in which the roots of vascular plants may suffer from anoxic conditions.…”

“…Fluvial disturbance include also water‐induced erosion, which removes soil surface horizons and causes mechanical damage to sessile organisms, such as vascular plants, mosses and lichens (le Roux and Luoto ). These evolutionary and ecohydrologically diverse taxonomical groups are key components of tundra ecosystem and presumably have dissimilar tolerances to different water‐phenomena (Iturrate‐Garcia et al ). Therefore, it is imperative to study how various aspects of water influence fine‐scale species distributions, species richness and community composition in the tundra.…”