不同荒漠草原植被根际与非根际土壤养分及碳库管理指数特征

Soil nutrients and carbon management indexes in the rhizosphere versus non-rhizosphere area of different plant species in desert grassland

通过对宁夏荒漠草原恢复工程主要植被柠条、沙蒿、短花针茅和蒙古冰草根际与非根际表层(0~5cm)、亚表层(5~10cm)和深层(10~15cm)土壤养分、土壤总碳(soil total organic carbon,Cr)、活性有机碳(active organic carbon,CA)、碳库指数(carbon pool index,CPI)及碳库管理指数(carbon pool management index,CPMI)特征进行分析研究,探讨不同植被恢复对土壤养分、CPMI变化特征的影响。结果表明:1)4种植被土壤养分均随土壤深度增加呈降低趋势,根际大于非根际,柠条群落根际和非根际表层速效钾(AK)含量高达130.81和111.96mg/kg,相对于亚表层和深层分别高6.87、31.65mg/kg和23.57、61.44mg/kg,随土层深度增加,根际表层,亚表层和深层比非根际土壤分别高18.84、35.55和48.63mg/kg,表现出了荒漠草原特殊的"肥岛"聚集效应,不同群落间差异显著(P<0.05);2)4种植被类型土壤总有机碳Cr含量在2.09~17.11g/kg范围内,土壤碳库管理指数CPMI均表现为根际大于非根际,Cr和CA含量在土壤垂直剖面中的分布相似,具有一定的"聚表效应",柠条和蒙古冰草群落表层比亚表层碳库活度分别增加了38.41%和29.54%,不同植被类型之间碳库活度表现为蒙古冰草>沙蒿>柠条>短花针茅,植被恢复显著改善了土壤有机质分布状况和土壤碳库质量,明显增强荒漠草原土壤碳汇功能;3)荒漠草原土壤CPMI与土壤养分含量显著相关(P<0.05),pH与Cr、CA、CPI和CPMI呈显著负相关(P<0.05),相关系数分别为-0.661、-0.437、-0.661和-0.410,与其他土壤养分指标呈显著或极显著正相关(P<0.05;P<0.01),土壤氮(N)、磷(P)、钾(K)促进了土壤碳库循环周转速率,显著提高土壤质量和生产力。CPMI能够用来作为评价土壤质量和土壤管理措施的有效指标。

The main plant species used in the Ningxia Desert Grassland Vegetation Restoration Project are Caragana korshinskii 9 Artemisia ordosica ^ Stipa breviflora ^ and Agropyron mongoLicum. The aim of this study was to explore the effects of different types of vegetation restoration on soil nutrients and carbon pool manage-ment index （CPMI） characteristics. We collected rhizosphere and non-rhizosphere soil from the surface （0-5 cm） , subsurface （5 -10 cm） , and deep （10 -15 cm） soil layers, and determined soil total carbon （Cr） , active organic carbon （CA）,carbon pool index （CPI） and CPMI. For all four plant species,soil nutrients decreased with increasing soil depth, and these decreases were greater in the rhizosphere soil than in the non-rhizosphere soil. The content of available potassium （AK） in the rhizosphere and non-rhizosphere of the C. korshinskii community was 130. 81 and 111. 96 mg/kg, respectively. The soil AK content showed a i（fat island^ aggrega-tion effect on the desert steppe, and showed significant differences among the different communities （P 〈C 0. 05）. 2） The total organic carbon content in soil ranged from 2. 09 to 17. 11 g/kg, and was higher in the rhi-zosphere soil than in the non-rhizosphere soil. The vertical distributions of Cr and CA in the soil profile were similar, and showed a “poly table” effect. The carbon pool activity in the surface layer of the C. korshinskii and A. mongolicum community was 38. 41 % and 29. 54% higher, respectively, than that in the deep layer.The four vegetation types could be ranked, from highest carbon pool activity to lowest, as follows： A. mongo- licum^〉A. ordosica）〉C. korshinskii〉S？ breviflora. Vegetation restoration significantly improved the distribu-tion of soil organic matter and the quality of the soil carbon pool, and increased the soil carbon sink function of the desert grassland. 3） The soil CPMI was significantly correlated with soil nutrient content in the desert grassland, and pH was negatively correlated with Cr, CA , CPI, and CPMI （correlation coefficients of -0.661,-0.437,-0. 661, and -0.410, respectively）. The soil CPMI was significantly or extremely significantly pos-itively correlated with other soil nutrients （P〈0 . 05; P〈0 . 01）. Higher soil N, P, and K contents promoted the soil carbon pool turnover rate, and significantly improved soil quality and productivity. These results show that CPMI serves as an effective index when evaluating soil quality and soil management practices.