漓江水陆交错带典型灌木群落根系分布与土壤养分的关系

在漓江流域水陆交错带选取一叶萩、细叶水团花、枫杨3种典型灌木群落,对不同土层深度的根长密度,以及根长密度与土壤有机质、全氮、有效磷的相关关系进行了研究,旨在为漓江流域生态修复过程中灌木植被恢复、主要灌木植被配置、快速绿化材料选取等提供科学依据。结果表明:(1)漓江水陆交错带典型灌木群落各土层根长密度差异性显著,分布规律均为:枫杨细叶水团花一叶萩。0—10 cm到40—60 cm土层,各灌木群落根长密度均减小,但不同灌木群落根长密度的差异程度逐渐缩小,表明地形、地表植物类型及生长状况对根长密度分布的影响也随土层深度的增加而逐渐减小。(2)枫杨(25.10g/kg)灌木群落底层腐殖质层厚,有机质含量最高,分别是细叶水团花、一叶萩的1.24、1.87倍。各灌木群落全氮含量从大到小依次是枫杨、细叶水团花、一叶萩,其值分别为:3.23、2.41、1.46 g/kg。土壤有效磷分布规律为一叶萩(11.56 mg/kg)细叶水团花(5.37 mg/kg)枫杨(3.99 mg/kg);一叶萩灌木群落有效磷含量远远大于枫杨和细叶水团花,原因是漓江水长期受人为洗漱影响,导致受江水干扰大的一叶萩灌木群落有效磷含量高。(3)根长密度与有机质、全氮含量呈正相关,与有效磷含量呈负相关,说明适量增加土壤有机质、全氮含量,减少土壤有效磷,有利于土壤根系的生长。根长密度与0L≤1 mm径级的根系所占比例呈极显著正相关,与1L≤2 mm径级的根系所占比例呈显著正相关,表明根系细根越多,根长密度越大。

Root distribution in shrub communities of Lijiang ecotone and their relationship to soil properties

Studies on the relationship between roots and soil are important to determine fundamental reasons for ecological degradation of riverside belt areas. Concentrating on the problem of ecosystem degradation in the Lijiang River, this paper explored the plant''s root distribution features in degraded ecosystems of the river-land ecotone. In the repair process, characteristics of the root distribution are an important basis for the characterization of different herbs'' soil and water protection functions. Thus, there is an urgent need to carry out studies on the distribution of dominant types of herbaceous plant roots at different sites of the Lijiang River ecotone. This paper studied the root length density at different soil depths and assessed the correlation between root characteristics and soil organic matter, total nitrogen, and available phosphorus. The results show significant difference between specific root lengths within each shrub community and each soil layer. The root length density decreased from Pterocarya stenoptera to Geum aleppicum to Securinega suffruticosa. In soil layers at 0-10 cm and 10-20 cm depth, the root length density decreased for each shrub community, but the decrease was gradual, indicating that the effects of the terrain surface, types of plants, and growth conditions on the distribution of root length density gradually decrease with the increase in soil depth. Pterocarya stenoptera had high total nitrogen content and root length density 1.24-fold that of Geum aleppicum and 1.87-fold that of Securinega suffruticosa. The difference in total nitrogen content significantly decreased from Pterocarya stenoptera to Geum aleppicum to Securinega suffruticosa. The available phosphorus content decreased from 11.56 g/kg in Securinega suffruticosa to 5.37 g/kg in Geum aleppicum and 3.99 g/kg in Pterocarya stenoptera. Since the Lijiang River water has been affected by human activities for a long time, the available phosphorus content is much greater in Securinega suffruticosa than in other species. The root length density is positively correlated with organic matter and total nitrogen and negatively correlated with the available phosphorus. We can, therefore, conclude that with more soil roots, there is more organic matter and total nitrogen and less available phosphorus. Root length density is significantly positively correlated with root diameter in the class of less than 1 mm at 0.01 level (two tails), and positively correlated with root diameter in the class of 1< L< 2 mm at 0.05 level (two tails).