玛河流域扇缘带盐穗木土壤速效养分的"肥岛"特征

比较了玛河流域扇缘带盐穗木灌丛在单生条件下及与猪毛菜共生条件下的土壤速效养分的"肥岛"特征。结果表明,盐穗木灌丛周围土壤的"肥岛"现象主要体现在土壤表层,沿立地点向外每隔0.6m逐渐减弱,且沿土层深度增加逐渐减弱。盐穗木在单生条件下,灌丛土壤碱解氮和速效钾在立地中心有明显的富集现象。在从立地原点向外3m的表层土壤中,两种养分分别从 2.75 g/kg和56.67 mg/kg下降至1.66 g/kg和29.0 mg/kg,且沿土壤剖面向下呈现显著性降低趋势(P<0.05),但均显著性高于裸地的同类值。而速效磷含量整体呈现亏损状态,其平均值较裸地速效磷含量低25.33%,表明盐穗木种群具有促进氮和钾的富积、但消耗磷的生态功能。在盐穗木-猪毛菜共生条件下,无论是在土壤表层还是沿土壤剖面,3种速效养分的含量整体上显著性高于裸地。共生条件下土壤的碱解氮含量整体低于单生条件下的值,而速效磷和速效钾的含量则是共生大于单生。研究表明,盐穗木单一种群条件下土壤速效磷的亏损状态可在猪毛菜共生条件下出现逆转,两者具有互补效应。该结论为干旱盐碱化地区植物与土壤关系研究提供了新的理论潜力。

"Fertile Island" features of soil available nutrients around Halostachys caspica shrub in the alluvial fan area of Manas River watershed

Spatial distribution and regulatory mechanism of available soil nutrients is widely considered as an important issue in plant and soil relations in arid areas, in which the impact of interaction between different plant populations on spatial distribution of soil available nutrients has been little reported. According to Liang et al. (2010), soil-plant interactions and sustainability of eco-agriculture in arid region is a crucially important topic to address. Manas River watershed is situated at the areas between northern slope of Tianshan Mountain and south edge of Junggar watershed, where the alluvial fan area of the watershed is a severely saline and alkaline eco-agricultural region in northwest China. In this study, a comparative experiment was conducted to reveal the "fertile island" features of soil available nutrients around the halostachys (Halostashys caspica) shrub under the conditions of single population and companion population with salsola (Salsola collina) in the alluvial fan areas of Manas River watershed. The results showed that soil "fertile island" effect around halostachys shrubs was mainly focused on the soil surface, and tended to be weakened gradually at intervals of 0.6m outward the standing point, and to decrease along the soil depth. Under the condition of solitary halostachys population, there existed a clear enrichment distribution for both soil alkaline nitrogen (AN) and available potassium (AK) along with the standing center. In the surface soil of 3m outward from standing point, the concentrations of these two nutrients were gradually lowered from 2.75 g/kg and 56.67 mg/kg to 1.66 g/kg and 29.0 mg/kg, and decreased significantly along the soil profile (P<0.05), yet were significantly higher than the corresponding values of bare land. For the change in available phosphorus (AP), there was a wholly deficit status in comparison with that of bare land, whose average content of AP was lower by 25.33% than the bare land. This result indicated that the Halostachys population has the ecological function to improve the enrichment of nitrogen and potassium, but lead to the consumption of phosphorus. However, no clear variation trend was observed along with the soil profile. On the other hand, under the symbiotic conditions of Halostachys and Salsola, the concentrations of three available nutrients in either the soil surface or along the soil profile were significantly higher than those of bare land. Furthermore, the soil AN concentrations were in general lower in symbiotic condition than those of solitary condition, but the AP and AK concentrations were greater in the former than those of the latter. Halostachys as a desert plant has a significant effect on the soil fertility, and the symbiotic interaction of Salsola leads to a more extensive and complementary influence on the "fertile island" effect of Halostachys shrub. Importantly, the loss of soil AP components in simplex Halostachys population can be reversed under the symbiotic conditions with Salsola population. This founding provides a theoretical potential for understanding plant and soil relations in arid saline regions, and a new practical approach to manage saline and alkaline soil for scientists and policy makers.