Molecular Soil Biology 2024, Vol.15, No.4, 172-182 http://bioscipublisher.com/index.php/msb 175 al., 2020). For instance, European beech and Norway spruce show species-specific root adaptations, with beech producing thin, ephemeral fine roots that have high specific root area and respiratory activity, facilitating rapid resource exploitation (Nikolova et al., 2020). Additionally, root system architecture, including the number and length of main and lateral roots, can be remodeled under drought conditions, driven by various phytohormones and signaling pathways (Ranjan et al., 2022). 4.2 Mycorrhizal associations Symbiotic relationships between tree roots and mycorrhizal fungi play a crucial role in improving water uptake efficiency under drought conditions. Arbuscular mycorrhizal fungi (AMF) enhance root morphological traits such as root length, surface area, and volume, which are critical for water absorption (Zou et al., 2017; Chandrasekaran, 2022). These fungi also increase the density and length of root hairs, further aiding in water uptake (Zou et al., 2017). Moreover, mycorrhizal associations can improve root hydraulic conductivity and nutrient acquisition, which indirectly supports better water relations in trees (Lehto and Zwiazek, 2011; Calvo-Polanco et al., 2016). For example, mycorrhizal associations in spruce help maintain high respiratory activity in absorptive roots during drought, indicating a reliance on these symbiotic relationships for drought resistance (Nikolova et al., 2020). 4.3 Osmotic adjustment and root hydraulics Physiological changes in tree roots, such as osmotic adjustment, are vital for retaining water during droughts. Roots can accumulate osmolytes like non-structural carbohydrates, which help maintain cell turgor and protect root tissues from dehydration (Nikolova et al., 2020). Additionally, the expression of aquaporin genes, which regulate water transport across cell membranes, can be modulated under drought conditions to enhance root hydraulic conductivity. For instance, olive plants inoculated with mycorrhizal fungi from different soils showed varied root hydraulic conductivity, highlighting the role of aquaporins in drought adaptation (Calvo-Polanco et al., 2016). These physiological adjustments enable roots to maintain water uptake and sustain tree growth even under prolonged dry conditions. 5 Ecological Significance of Root-Soil Water Dynamics 5.1 Contribution to ecosystem stability Tree root systems play a crucial role in maintaining ecosystem resilience during periods of water stress. Roots are capable of various adaptive responses to drought, such as adjusting root biomass, altering anatomical structures, and undergoing physiological acclimations. These adaptations help trees to avoid and tolerate drought stress, thereby supporting the stability of forest ecosystems (Brunner et al., 2015; Kou et al., 2022). For instance, the ability of roots to access deep water sources during drought conditions ensures the continued survival and functioning of trees, which in turn maintains the overall health and stability of the ecosystem (David et al., 2013; Mackay et al., 2019). 5.2 Tree species-specific adaptations Different tree species exhibit unique root-based adaptations to drought conditions. For example, Mediterranean evergreen oaks like Quercus suber have a dimorphic root system that allows them to access both shallow and deep water sources, thereby maximizing water uptake during dry periods (David et al., 2013). Similarly, tropical Eucalyptus species develop deep root systems that enable them to tap into deep soil water reserves, which is particularly beneficial during prolonged dry spells (Christina et al., 2017). These species-specific adaptations highlight the diversity of strategies employed by trees to cope with water stress, emphasizing the importance of understanding root dynamics in different ecological contexts (Bourbia et al., 2021; Ranjan et al., 2022). 5.3 Soil erosion and water conservation Tree roots significantly impact soil erosion prevention and soil water retention. The extensive network of fine roots and root hairs increases the soil's structural integrity, reducing the likelihood of erosion (Nirala et al., 2019). Additionally, roots contribute to soil water conservation by enhancing the soil's ability to retain moisture. This is particularly important in preventing soil degradation and maintaining soil health during drought conditions. The role of roots in hydraulic redistribution, where water is moved from wetter to drier soil layers, further aids in
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