Shifts in functional trait–species abundance relationships over secondary subalpine meadow succession in the Qinghai–Tibetan Plateau

Abstract

Although trait-based processes of community assembly during secondary succession invokes multiple factors that ultimately determine the presence or absence of a species, little is known regarding the impacts of functional traits on species abundance in successional plant communities. Here in species-rich subalpine secondary successional meadows of the Qinghai-Tibetan Plateau, we measured photosynthesis rate and leaf proline content that are related to plant growth and abiotic stress resistance, respectively, and seed germination rate that is closely correlated with plant germination strategy to test their influence on species abundance during succession. We used a linear mixed effects model framework to examine the shifts in trait-abundance relationships and the correlations among these three traits in successional communities. We observed significant shifts in trait-abundance relationships during succession, e.g., abundant species in early-successional meadows exhibited relatively high photosynthesis rates and leaf proline content, but showed low seed germination rates, whereas the converse were true in late successional communities. However, the correlations among the three traits were insignificant in most meadow communities. Our results show that functional traits associated with plant growth, stress resistance, and reproduction impose strong influence on species abundance during secondary subalpine meadow succession in the Qinghai-Tibetan Plateau.

Can the response of above- and below-ground traits to overgrazing vary between annual and perennial species?

“…Traits were measured from three to five mature individuals per species and detail measurement was described in Bergmann et al . (2017) and Zhang et al . (2018) and Supplementary materials.…”

“…The local vegetation in undisturbed sites is dominated by herbaceous species, such as Elymus nutans (Griseb), Kobresia pygmaea (C. B. Clarke), and Thermopsis lanceolata (R. Br) (Zhang et al ., 2015). Soils are classified as alpine meadow soils (Zhang et al ., 2018).…”

“…Finally, a principal component analysis (PCA) was employed to evaluate which of the eight above-ground and root traits play an important role in affecting species distributions between undisturbed and overgrazed meadows at all elevations. Given the unique set of traits between annual and perennial plant species (Roumet et al ., 2006; Zhang et al ., 2018), the above analyses were also performed separately for annuals and perennials to understand whether the response of above- and below-ground traits to overgrazing vary between annual and perennial species.…”

“…A global meta-analysis showed that overgrazing promotes annual species over perennial species (Díaz et al ., 2007). Conversely, without grazing pressure, perennial species are expected to dominate (Zhang et al ., 2018). This is likely due to the fact that annual species tend to have above- and below-ground traits that are associated with high resource acquisition, whereas perennial species tend to possess traits related to a resource conservation strategy (Roumet et al ., 2006, 2016; Zhang et al ., 2018).…”

“…Conversely, without grazing pressure, perennial species are expected to dominate (Zhang et al ., 2018). This is likely due to the fact that annual species tend to have above- and below-ground traits that are associated with high resource acquisition, whereas perennial species tend to possess traits related to a resource conservation strategy (Roumet et al ., 2006, 2016; Zhang et al ., 2018). As a result, the response of above-ground and below-ground traits to overgrazing may vary between annual and perennial species.…”