4.3. The coordinated changes between root system architecture
traits and RMF and LMF optimizes adaptive strategy
Plants can achieve a balance between resource acquisition and allocation
through coordinated changes in biomass allocation and morphological
characteristics (Chapin, 1991; Nicotra et al., 2010; Freschet et al.,
2018). The LMF and RMF determines their future morphological changes and
ultimately affects the way they obtain resources (Freschet et al.,
2015b; Yin et al., 2019). The LMF is closely related to the water
consumption capacity of plants, and the higher the LMF, the greater the
water consumption and demand of its leaves (Yin et al., 2019). In the
present study, LMF is significantly positively correlated with SRA and
SRL (Fig. 5cd). This indicates that plants can mitigate water and water
loss caused by high LMF by improving the absorption efficiency of root
water and nutrient (Isaac et al., 2017; Wang et al., 2018). In addition,
LMF and MRD also showed a significantly positive correlation (Fig. 5a).
This may be another ecological strategy for plants to cope with the
water consumption caused by high LMF, that is, by increasing the ability
of root systems to explore the vertical space of the soil, greatly
increasing the probability of encountering water rich areas
(Martínez-Sánchez et al., 2003; Tsakaldimi et al., 2009). Moreover, the
results of this study indicate a significant negative correlation
between LMF and RTD (Fig. 5e). This may be because RTD is closely
related to the resource conservation ability of the root system
(Bergmann et al., 2020; Carmona et al., 2021), so plants must achieve a
balance between resource conservation and consumption among organs
through the trade-off between LMF and RTD.
There may have a significant positive correlation between morphological
characteristics and biomass proportion of ephemerals (Cheng et al.,
2006; Zhang et al., 2020). In the present study, the positive
correlation between RMF and MRD is significant (Fig. 6a), which further
indicates that the exploration of soil vertical space by roots depends
on the biomass investment of plants in the roots. Furthermore, the
negative correlation between RMF and RD is significant (Fig. 6b). Roots
with high root diameters have been proven to be resource conserving
roots with slow metabolism and effective resistance to mechanical
damage, herbivores, and drought stress (Withington et al., 2006; Kong et
al., 2014; Weemstra et al., 2016). According to the functional
equilibrium hypothesis, the increase in root biomass is due to resource
constraints on root growth (Poorter et al., 2012; Freschet et al.,
2018). Therefore, when the scarcity of underground resources leads to an
increase in root biomass investment, what the root system most needs is
to increase the ability to explore resources or the efficiency of
acquiring resources, rather than conservating resource. The trade-off
between RMF and RD enables the root system to achieve the optimal
balance between resource investment and return. In addition, the
phylogenetic relationship significantly affects the relationship between
root architecture traits and the proportion of root and leaf biomass.
This indicates that the coordinated changes between root architecture
traits and the proportion of organ biomass may partly depend on the
phylogenetic relationships between species.