Responses of C∶N∶P Ecological Stoichiometry in the Leaves of Atriplex canescens to N Addition Cloning and Sequence Analysis of a Osmotin-like Protein Gene from Atriplex canescens and Its Prokaryotic Expression Effect of Different Cutting Frequencies on Biomass Accumulation and Root Vertical Distribution of Atriplex canescens(Pursh) Nutt. Effects of Activities of Protective Enzymes and Seed Germination in Atriplex canescens under NaCl and Na2CO3 Stress