Responses of an evergreen shrub Sabina vulgaris to soil water and nutrient shortages in the semi-arid Mu Us Sandland in China

Physiological and morphological responses of the evergreen dominant shrub Sabina vulgaris to soil resource (i.e. water, nitrogen, phosphorus and potassium) changes were studied in the semi-arid Mu Us Sandland in China. Blade thickness and cuticle thickness showed an inverse response to soil resources. Both mesophyll cell size and vascular bundle size were strongly negatively correlated with soil water content, while net photosynthesis, night respiration and stomatal conductance were highly positively correlated with soil water content. Water-use efficiency, the ratio of substomatal CO2 concentration to atmospheric CO2 and coefficient of water loss exhibited different changes in response to soil resources. Rooting depth decreased with increasing soil water content, and the potential to share water appeared in the root system of the species. Nitrogen (N) and phosphorus (P) use efficiencies increased with increasing soil N and P availability, whereas N and P resorption efficiencies decreased with increasing soil N and P availability. Both K use efficiency and K resorption efficiency decreased with increasing soil K availability. Nutrient (i.e. N, P and K) resorption proficiency varied with the habitats.