围封年限对沙质草地土壤理化性质的影响

Effects of Enclosure Year on Soil Physicochemical Properties of Sandy Grassland

以腾格里沙漠南缘未围封和围封3,10,18,55年的沙质草地为研究对象,采用野外采样和实验室分析相结合的方法,研究围封年限对沙质草地土壤理化性质的影响。结果表明:(1)0-40cm,围封3,10,18,55年草地的平均土壤容重较未围封草地分别降低15.91%,21.59%,11.36%,10.80%;非毛管孔隙度较其分别增加28.46%,56.10%,19.51%,3.25%,总孔隙度分别增加31.13%,34.69%,23.04%,1.18%,最大持水量分别增加55.37%,71.54%,38.74%,12.80%;围封3,10,18,55年草地的土壤养分均高于未围封草地,并具有明显的表聚现象;0-20cm,未围封,围封3,10,18,55年草地的土壤全N含量较20-40cm分别增加28.58%,19.61%,47.62%,38.67%,3.85%,全P含量分别增加18.75%,16.67%,15.38%,14.29%,全K含量分别增加23.58%,3.58%,8.23%,8.39%,2.46%,有机碳含量分别增加79.45%,27.16%,89.12%,175.22%,198.47%;土壤有机碳密度表现为10Ex(7.06kg/m2)>3Ex(5.39kg/m2)>18Ex(5.20kg/m2)>55Ex(4.90kg/m2)>0Ex(2.83kg/m2);(2)随着围封年限的增加,土壤容重呈"V"形变化,围封10年达到最小值,群落植被特征、土壤孔隙度、土壤持水量、土壤养分,土壤有机碳密度及储量均呈倒"V"形变化,围封10年达到最大值,之后降低,但均好于未围封草地,围封后,草地的地表覆盖度增加,土壤理化性质有所改善,土壤固碳能力有所提高,但围封年限并非越长越好,本研究区的生态环境极其脆弱,土壤贫瘠,完全恢复需要较长的时间,10年围封并不能使该区完全恢复,适宜其完全恢复的时间还有待于继续研究。

The effects of enclosure year on soil physicochemical properties of sandy grassland were studied by using the method of combination field survey with laboratory analysis, and non-enclosure and enclosure sandy grasslands in 3, 10, 18, 55 years were chosen to study in southern edge of the Tengery Desert. The results showed： （1）Compared with non-enclosure grassland, the soil average bulk density of enclosure grassland in 3, 10, 18, 55 years in 0--40 cm soil layer decreased by 15.91%, 21.59%, 11.36%, 10.80%, and soil non- capillary porosity increased by 28. 46%, 56. 10%, 19. 51%, 3. 25%, soil total porosity increased by 31.13%, 34.69%, 23.04%, 1.18%, maximum soil water-holding capacity increased by 55.37%, 71.54%, 38.74%, 12.80%. Soil nutrients of enclosure grassland in 3, 10, 18, 55 years were all higher than that of non-enclosure and mostly distributed in surface soil layer, compared with the soil nutrients in 20--40 cm soil layer, soil total N content of non-enclosure and enclosure grassland in 3, 10, 18, 55 years in 0--20 cm soil layer increased by 28. 58%, 19. 61%, 47. 62%, 38. 67%,3. 85〉, and soil total P content increased by 18.75G, 16.67%, 15.38%, 14.29%, soil total K content increased by 23.58%, 3.58%, 8.23 %,, 8.39%, 2.46〉%, soil organic carbon content increased by 79.45%, 27. 16%, 89. 12%, 175.22%, 198.47%. The order of soil organic carbon density was 10Ex（7.06 kg/m2 ）3Ex（5.39 kg/m2） 〉18Ex（5.20 kg/m2） 55Ex（4.90 kg/m2） ）0Ex（2.83 kg/m2）. （2）With the increase of enclosure years, soil bulk density showed a ＂V＂ shape change and got the minimum when sandy grassland was enclosed 10 years. Characteristics of community vegetation, soil porosity, soil water-holding capacity, soil nutrient, soil organic carbon density and storage showed inverting ＂V＂ shape change and got the maximum when sandy grassland was enclosed 10 years, then they decreased, but all of them were better than non-enclosure grassland. After enclosing, the surface coverage of grassland increased, soil physicochemical properties improved and sequestration carbon capacity enhanced. However, enclosure year was not the longer the better. The ecological environment of this study area was extremely fragile, it would take a long time to restore completely. Enclosure in 10 years did not make the area fully recovery, the suitable time for the grassland fully recovery needed continue to study.