三峡库区消落带落羽杉(Taxodium distichum)与柳树(Salix matsudana)人工植被对土壤营养元素含量的影响

落羽杉与柳树被认为是三峡库区消落带植被修复的适生树种。2012年7月(T1)及2013年7月(T2)在消落带人工基地取样,研究了消落带人工植被(处理组)及裸地土壤(对照组)的营养元素含量,并对植被生长情况进行调查。结果表明:(1)对比处理组与对照组养分含量发现,T1时除土壤p H值外,其他养分含量在处理组与对照组间均存在差异。T2时只有p H值、磷(包括有效磷AP、全磷TP)、速效钾(AK)含量在处理组与对照组中差异显著。(2)对同一植被类型而言,T2时落羽杉土壤p H值与土壤有机质含量(OM)均显著低于T1,同样,T2时柳树实生土壤OM也显著降低;处理组土壤中碱解氮(AN)、AP、全钾(TK)含量极显著的低于淹水前,而TP含量却显著升高;与T1相比,T2时裸地土壤除AN含量降低、AK含量显著升高外,其它养分含量均未呈现显著差异。(3)相关性分析表明,土壤p H值与TP含量呈现极显著负相关,而OM与AN、AP、TK分别呈现出极显著正相关。AN、AP分别与TP表现出极显著负相关关系,而与TK表现出极显著正相关关系。TK与TP也呈现极显著的负相关关系。此外,植物高度、基径与冠幅三项生长指标与土壤中的p H值、OM、AN、AP(高度除外)、TK呈现出负相关的现象。研究表明,落羽杉与柳树人工植被对土壤养分的影响主要出现在水淹之前,进一步证实在三峡库区消落带开展科学的植被修复与重建值得提倡和肯定。

Effects of Taxodium distichum and Salix matsudana on the contents of nutrient elements in the hydro-fluctuation belt of the Three Gorges Reservoir Area

The purpose of this study was to examine the dynamics of the chemical properties of soil in the water level fluctuating zone of the Three Gorges Reservoir (TGR) region. In addition, the potential impact of vegetation reconstruction on water quality was investigated. Bald cypress (Taxodium distichum) and Chinese willow (Salix matsudana) are the two dominant species in the riparian zone of the TGR area. Soil samples were taken from vegetation planted below either T. distichum, S. matsudana (treatments), or bare soil (control) in July 2012 (T1) and July 2013 (T2), before flooding and after water flooding respectively. The following parameters were measured:soil pH, organic matter (OM), alkali hydrolysable nitrogen (AN), available phosphorus (AP), available potassium (AK), total nitrogen (TN), total phosphorus (TP), total potassium (TK), and plant growth. The results showed that:(1) At T1, the treatment and control soil nutrient contents were significantly different, whilst pH did not differ between these groups. In contrast, at T2, only the pH, AP, TP, and AK showed significant differences between the treatments and control. (2) The pH value and OM content of T. distichum in T2, as well as OM content in S. matsudana in T2, were significantly lower than those in T1. After flooding (T1), although AN, AP, and TK contents below the experimental vegetation were significantly lower than the control, TP content was significantly increased. In contrast, at T2, besides an obvious decrease of AN content and a significant increase in AK, the other nutrient elements did not have any notable differences. (3) Correlation analysis showed that pH values were negatively correlated with TP, and OM showed a positive correlation with AN, AP, and TK. Furthermore, AN and AP were negatively correlated with TP and positively correlated with TK. TP and TK had a strong negative relationship. The three growth indices including height, diameter at breast height (DBH), and canopy cover were negatively correlated with soil nutrient elements, including pH, OM content, AN, AP (except height), and TK, while the height showed a positive correlation with TP. In conclusion, this study suggests that the effects of artificially vegetating soil appear only before flooding (T1), but no tafter water flooding (T2). Soil chemical properties under different treatments were homogeneous, which further confirms that artificial revegetation can improve the soil ecological environment with a low chance of eutrophication of the water body. However, there is the potential risk of phosphorus being released from the revegetation soil under S. matsudana, and therefore the detection of water phosphorus content is an important factor to take into consideration.