<正>在栎林中多剖面采样测定土壤体积质量、非毛管孔隙度、稳渗率、有机质、pH等土壤因子。结果表明，各因子都具有一定的空间变异性，且垂直方向的变异大于水平方向。这种空间变异性的存在决定了在开展土壤研究中必须根据误差理论确定样本容量，才能保证测定结果具有可比性。统计分析结果显示，测定土壤稳渗率需要大量的样本。而测定其他因子，则仅需要20个以下样本即可以保证95%的可靠性。

Effects of silicon addition on chlorophyll fluorescence and gas exchange of Zizyphus jujuba cv. Jinsi-xiaozao under salt stress were studied by using 2-year-grafted seedlings. Ordinary agronomic soil was selected as pot-cultured medium. Sources of sodium and silicon for experiment were sodium chloride and potassium silicate. Soil salt contents (NaC1) were planned 3 levels,i, e. 0 g/kg,3. 0 g/kg and 5. 0 g/kg. Soil silicon (Si) contents were planned 2 levels,i, e. 0 g/kg and 0. 4 g/kg. The experimental results showed that the growth in soils containing 3. 0 g/kg or 5. 0 g/kg NaC1 for 135 d salt ions had distinctively negative effects on j isi jujube plants: Chlorophyll content decreased by 12. 30% and 22. 08% respectively compared with none-salt stress, while silicon addition increased chlorophyll content by 12. 30o//oo and 22. 08% respectively compared with under the two salt stresses;Fv/Fo and Fv/Fo of PSⅡ, two important chlorophyll fluorescence parameters,decreased by 19. 96%,34. 58% and 8. 86%, 14. 10% respectively, while increased 32. 25%, 30. 71% and 11. 26%, 12. 15% respectively under silicon addition; photosynthetic rate and cellular conductance decreased by 11. 04%, 25. 32% and 26. 13%, 16. 22% respectively, while increased 10. 94%, 20. 87% and 42. 68%, 10. 85% respectively under silicon addition. The results revealed the silicon addition ameliorated salt toxicity, osmotic stress and nutrition deficit on Z. jujuba cv. Jinsi-xiaozao plant under salt stress.