干热河谷优势灌木种类的根系结构及碳氮磷元素含量特征

Root structure and element (C,N,P) content characteristics of dominant shrub species in a dry-hot valley

研究干热河谷优势灌木的根系特征,有助于了解植物根系的养分和水分吸收能力、固土作用及对恶劣环境的适应与生存策略,为干热河谷植被恢复和生态环境改善提供理论依据.选取马桑(Coriaria sinica)、坡柳(Dodonaea viscose)和苦刺(Sophora davidii)3种干热河谷优势灌木种类,对其根系的形态结构特征和碳(C)、氮(N)、磷(P)元素含量状况进行研究.研究结果表明,马桑、坡柳和苦刺的根长、根表面积、干质量以及部分径级比根长(SRL)和比表面积(SSA)无显著差异,马桑0-2 mm根系的比根长显著高于>2 mm根系,表明其0-2 mm根的养分与水分吸收能力优于>2 mm的根;坡柳和苦刺0-1 mm根系的比根长均显著高于>1 mm根系,表明其0-1 mm根的养分与水分吸收能力显著高于>1 mm的根.苦刺根系的平均C、N、P含量显著高于马桑和坡柳,不同径级的N含量均显著高于马桑和坡柳,这与苦刺为豆科植物具有较强的固氮能力有关.根据N:P判断,苦刺根系受P的限制,马桑和坡柳根系受N的限制.3种灌木的比根长和比表面积与元素含量基本不存在显著相关性,原因在于比根长和比表面积随径级变化的趋势与根系元素含量的变化趋势不同,造成两者相关性不显著.综上所述,干热河谷3种灌木的根系形态结构特征具有一定的相似性,但元素C、N、P含量以苦刺最高,该结果有助于了解当地植物对土壤养分的利用效率和适应生存策略.

Investigating root characteristics of dominant shrubs in dry-hot valleys is helpful to better understand plants ability to absorb nutrients and moisture, the soil-fixing effect of roots, and adaptations and survival strategies for harsh environments. It also provides a theoretical basis for vegetation restoration and ecological improvement in dry-hot valleys. In this paper, three dominant shrub species in dry-hot valleys(Coriaria sinica, Dodonaea viscose, and Sophora davidii) were selected to explore their morphological and structural characteristics and root element contents. There were no significant differences between root length, root surface area, dry weight, specific root length(SRL), and specific surface area(SSA) at partial diameters of C. sinica, D. viscose, and S. davidii. There was a significant difference between SRL of 0-2 mm roots and SRL of > 2 mm roots of C. sinica, indicating that the nutrient and water absorption capacity of 0-2 mm roots is better than > 2 mm roots. There were also significant differences between SRL of 0-1 mm roots and SRL of > 1 mm roots of D. viscose and S. davidii, indicating that the nutrient and water absorption capacity of 0-1 mm roots is significantly higher than roots > 1 mm. The average C, N, and P contents of S. davidii roots were significantly higher than those of C. sinica and D. viscose. The N contents of different diameter grades were also significantly higher than that of C. sinica and D. viscose. These are related to the strong nitrogen fixation of S. davidii for legumes. According to N:P, the roots of S. davidii are restricted by P, and the roots of C. sinica and D. viscose are restricted by N. The SRL and SSA of the three shrubs were not significantly correlated with elemental content. Changes in SRL and SSA with diameter level were different from changes with elemental content. In summary, root morphological and structural characteristics of the three shrubs in a dry-hot valley were similar, but the content of C, N and P are the highest in S. davidii. This result helps to understand soil nutrient utilization efficiency and survival strategies in local plants.