青藏高原高寒草原区工程迹地面积对其恢复过程中土壤水分和养分含量变化的影响

工程迹地面积严重影响着青藏高原受损天然草原的恢复程度。本研究测定了历经18年恢复期的不同面积的工程迹地(55、156、254、583m~2)的土壤水分、有机质和养分含量,以工程迹地附近的青藏苔草(Carex moorcroftii)+紫花针茅(Stipapurpurea)天然草原作为对照,揭示工程迹地面积对土壤持水力、养分潜力和养分供给能力恢复程度的影响。结果表明,工程迹地面积小于254m~2时,0-20cm土层土壤含水量与天然草原土壤差异不显著(P0.05),但当其增至583m~2时,土壤含水量却显著低于天然草原(P0.05);工程迹地面积小于254m~2时,0-10cm土层有机质含量显著高于天然草原,10-20cm土层有机质含量却显著低于天然草原,但它们均显著高于工程迹地面积为583m~2时的土壤有机质含量(P0.05);工程迹地为55m~2时,其土壤全氮含量和天然草原差异不显著(P0.05),但当迹地面积大于156m~2时,土壤全氮、铵态氮和硝态氮含量均显著低于天然草原(P0.05),且随工程迹地面积增加,降低幅度逐渐增加;0-10cm土层全磷含量随工程迹地面积增加先增加后降低(P0.05),在156和254m~2时较高;土壤速效磷含量却先降低后增加,在156和254m~2时较低。土壤全钾和速效钾含量随工程迹地面积增加先升高后降低,均以254m~2时最大,当工程迹地面积大于254m~2时,土壤全钾和速效钾含量低于天然草原,当其小于254m~2时土壤全钾和速效钾含量高于天然草原。土壤含水量、养分潜质和养分含量对工程迹地面积响应的结果表明,工程迹地面积小于254m~2时土壤持水量、养分潜力和养分供给力基本得到恢复。

Effect of areas of land used for engineering construction on soil moisture and nutrient in the alpine steppe regions of the Qinghai-Tibet Plateau

The area of land used for engineering construction greatly affects the restorable degree of destroyed natural steppe on the Qinghai-Tibetan Plateau.An experiment was carried out to disclose the effect of land use for engineering construction on the conservation of water,potential nutrients,and present nutrients of soil in land that had been used for engineering construction and had experienced identical restoration periods.This study showed that the soil moisture content did not different between land used for engineering construction and natural steppe when the area used for construction was below 254 m2 .Furthermore,the soil moisture of land used for engineering construction was smaller than that of natural steppe when the area used was 583 m2 (P <0.05).The organic matter content at a soil depth of 0 - 10 cm in land used for engineering construction was bigger and that at a depth of 10-20 cm was smaller than that of natural steppe when the area used for en-gineering construction was below 254 m2 .However,the organic matter content at both soil depths in land used for engineering construction was smaller when the area used was 583 m2 (P <0.05).The soil total nitrogen con-tent did not differ between land used for engineering construction and natural steppe when the area used was 55 m2 .The soil total nitrogen,ammonium nitrogen,and nitrate nitrogen contents of land used for engineering construction were significantly lower than those of natural steppe (P <0.05)when the land used for engineering construction was over 156 m2 .The amplitudes of these declines in nitrogen content correlated with the area of land used for engineering construction.The total phosphorus content at a soil depth of 0-10 cm first increased and then decreased as the area of land used for engineering construction increased (P <0.05),peaking at 156 and 254 m2 .The available phosphorus contents at soil depths of 0-10 and 10-20 cm first decreased and then increased as the area of land used for engineering construction increased,reaching nadirs at 156 and 254 m2 . The total potassium and available potassium contents in soil first increased and then decreased as the area of land used for engineering construction increased,peaking at 254 m2 .The total potassium and available potassi-um contents of land used for engineering construction were lower than those of natural steppe when the area used was over 254 m2 ,and they were bigger than those of natural steppe when the area used was below 254 m2 . These results suggested that the conservation of water,potential nutrients,and present nutrients in the soil of land used for engineering construction were similar to those of natural steppe when the area of land used for en-gineering construction was below 254 m2 ,but differed in larger areas,when all the tested areas had experienced identical restoration periods.