Abstract
The herb layer plays a significant role in maintaining forest functions, and its community composition is determined by various abiotic factors and biotic interactions. This study attempted to investigate the interspecific plant–plant biotic interactions using a functional traits approach. Specifically, the effects of a dominant species coverage on the functional diversity of coexisting species in the temperate forest understory were studied. Species coverage and soil moisture data were collected using a 1 m2 quadrat couplet (2 × 1 m2) from six sites alongside a 20 m linear transect encompassing a cover gradient of Allium ursinum in southwest Hungary. Major plant functional dimensions i.e., aboveground, and clonal functional traits were considered. Linear and nonlinear mixed models to quantify the effects of biotic interaction on the functional diversity of every single trait and multiple traits were employed. Both aboveground traits and clonal traits of persistent clonal growth organs responded positively to the A. ursinum L., cover gradient. The coexistence of understory species in the presence of a monodominant species seems to be mainly influenced by aboveground traits as compared to the clonal traits suggesting, a role of niche differentiation. The consistent impact of A. ursinum coverage on coexisting species dynamics highlights a need for similar in-depth studies in various forest settings.
Highlights
The understorey of temperate forest ecosystems has a significant impact on forest regeneration and conservation of biodiversity [1,2]
We focused on these key informative traits on different ecological functions such as resource economics, competitive ability, sexual reproduction [43,44], the clonal traits related to space occupation and resource foraging [47]
As a response to A. ursinum cover gradient, the standardized effect size index of functional diversity (SES-FD) of the aboveground traits resulted in a significant effect only for nonlinear components of the model (Table 1)
Summary
The understorey of temperate forest ecosystems has a significant impact on forest regeneration and conservation of biodiversity [1,2]. Owing to certain ecophysiological effects (nutrient richness, or high soil moisture content etc.) the abundances of some species might exceed the natural fluctuations (in this case they are defined as an “expansive species”; [11,12,13]), which subsequently can lead to the loss of biodiversity [14,15]. It might serve as an early warning sign for urgently taking measures in the conservation of a given ecosystem [16,17,18,19]
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