Abstract
Plant root variations and their relations with soil moisture and nutrient supply have been well documented for many species, while effects of drought, combined with extreme poor soil nutrients, on plant roots remain unclear.Herein, we addressed root vertical distributions of two typical xerophyte semishrub species, Artemisia sphaerocephala and A. intramongolica, and their relations with soil moisture, total soil nitrogen and carbon contents in arid Hunshandake desert, China. The two species experienced similar light regimes and precipitation, but differed in soil moisture and soil nutrients.Root vertical distribution patterns (e.g., coarse root diameter, root depth and root biomass) differed considerable for the two species due to high heterogeneity of soil environments. Coarse and fine root biomasses for A. intramongolica, distributed in relatively moist fixed dunes, mainly focused on surface layers (94%); but those for A. sphaerocephala dropped gradually from the surface to 140 cm depth. Relations between root traits (e.g., diameter, root biomass) and soil moisture were positive for A. intramongolica, but those for A. sphaerocephala were negative.In general, the root traits for both species positively correlated with total soil nitrogen and carbon contents. These findings suggest that both soil moisture and poor soil nutrients were the limiting resources for growth and settlement of these two species.
Highlights
Roots fix plants to soil, and an important cycling interface of water and nutrients in terrestrial ecosystems, and relationships of root traits with soil water and nutrients can well reflect the specific adaptation and species ability to survive and settle in harsh environments
These works provide strong evidence that root production correlates with climate, soil texture, and nutrient contents (McCormack et al, 2015; Wang & Gao, 2003), but previous research in water-limited environments leaves little doubt about the relationships of plant roots with extreme poor soil nutrients combined with drought
Root diameters for A. sphaerocephala were negatively correlated with soil moisture from the surface layer to 140 cm deep (p < .01), while that for A. intramongolica were positively correlated with soil moisture but nonlinearly (p < .01, Figure 1b)
Summary
Roots fix plants to soil, and an important cycling interface of water and nutrients in terrestrial ecosystems, and relationships of root traits with soil water and nutrients can well reflect the specific adaptation and species ability to survive and settle in harsh environments (e.g., saline lands and deserts). Some studies have proven that low levels of soil water and nutrients can promote preferential production of root biomass in dry environments (Archer, Quinton, & Hess, 2002; Bai, Wang, Chen, Zhang, & Li, 2008) and hypothesis that plants preferentially allocate more resources to roots when water and nutrients become limited to growth (Garnier, 1991) These works provide strong evidence that root production correlates with climate (e.g., precipitation, aridity), soil texture, and nutrient contents (McCormack et al, 2015; Wang & Gao, 2003), but previous research in water-limited environments leaves little doubt about the relationships of plant roots with extreme poor soil nutrients combined with drought. This information is essential for formulating generalizations regarding the relationships of root traits with soil water and nutrients in dryland ecosystems
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