4.1. The differences in variation patterns of different root
traits enhance the adaptability of the root system
Interspecific variation in plant traits is the basis for coexistence of
different species in similar habitats (Diaz et al., 2004). Analogy to
leaf trait variation, interspecific variation in root system
architecture trait can partly explain the impact of habitat filtering
and interspecific competition on plant root strategies at a local scale
(Bu et al., 2017; Hajek et al., 2013; Hogan et al., 2020). In the
present study, the degree of CV inter of the six
root system architecture traits is distinct (Table 1). Among them, the
RTD is the highest, and the TI is the lowest (Table 1). The results
manifested that the RTD of annual ephemerals showed a divergent
adaptation, while the branching pattern (TI) showed a convergent
adaptation due to the combined effects of environmental filtering and
similarity constraints (Grime, 2006). The divergence adaptation of RTD
is conducive to these plants to reduce biological competition by
adopting different root resource defense strategies when dealing with
highly heterogeneous desert environments (Tjoelker et al., 2005; Lan and
Zhang, 2008; Xu et al., 2021). Meanwhile, the convergence of root
branching patterns caused by environmental filtering towards more simple
herringbone branching patterns can effectively reduce the carbon
investment cost of underground root construction, allowing annual
ephemerals to allocate more resources to the growth of the aboveground
parts (Qiu et al., 2007; Spanos et al., 2008; Tsakaldimi et al., 2009).
Intraspecific variation refers to the differences in genetic material
and phenotypic characteristics between different botany individuals from
the same species (Albert et al., 2010b). The variation of genetic
material between different individuals of the same species and the
phenotypic plasticity in response to environmental changes may cause
intraspecific variation of plant functional traits (Jung et al., 2014).
In the present study, the variation range ofCV intra in root architecture traits related to
acquisition of resources (e.g., SRL, SRA) and resistance to
environmental (e.g., RTD) interference is relatively large, showing a
certain degree of divergence (Fig. 3). This may be because the annual
ephemeral species collected in this study are all distributed in
heterogeneous desert habitats with low species richness and relatively
scarce resources, which causes some species to exhibit high plasticity
in root resource acquisition or defense traits (Siefert et al., 2015).
This may be crucial for them to adapt to desert environment, because
when resource availability changes rapidly in time and space, high
phenotypic plasticity represents that plants have certain adaptive
advantages (Hajek et al., 2013). Additionally, this divergence in the
plasticity of resource acquisition traits and defense traits of
different species may help plant individuals (even different individuals
from the same species) occupy different ecological niche, thus promoting
the coexistence of annual ephemeral plants in limited resource habitats
(Bu et al., 2017).