水文与岸滩变化对滨岸带南荻-芦苇群落适宜生境的影响——以长江武汉河段为例

建立了考虑淹没频率和淹没水深等生境因子的水动力-生境适宜度数学模型,基于三峡水库蓄水前后的长序列水文观测数据和不同时期的河道地形资料,研究了近20年来武汉河段汉口边滩南荻(Miscanthus lutarioriparius)-芦苇(Phragmites australis)群落的适宜生境变化情况,量化了不同因素的影响.结果表明:所建立的生境数值模型能较好地模拟还原南荻-芦苇群落实际空间分布情况.与2001年前的情况相比,若维持地形不变,三峡水库蓄水后的径流过程调平、年内水位变幅减小将导致群落适宜分布带向河道方向转移,且面积减小33.24%;若保持水文条件不变,岸线利用引起的地形坡度坦化将导致群落扩张,其分布面积增加69.11%;由于后者影响占主导地位,在2种因素综合影响下,南荻-芦苇群落向低滩地蔓延的同时呈现了扩张的趋势,面积增加42.53%.进一步发现,若滩地地形变化或人工建筑位于淹没频率在5%~25%区间带内,则水文变化、地形变化2种因素会对南荻-芦苇群落生境产生迭加影响,这种迭加影响甚至会大于单因素影响之和.研究表明岸滩开发等人为干扰导致滨岸滩地改变时,可能会影响滩上植被生长条件,这值得有关部门进行岸线规划、利用和进行生态保护时重点关注.

Influence of hydrological and morphological changes on the habitats of Miscanthus lutarioriparius and Phragmites australis in a river flood plain:A case study of Wuhan reach of the Yangtze River

In order to quantify the effects of hydrological conditions and topographic factors on the Miscanthus lutarioriparius and Phragmites australis (MP) in Wuhan reach. A numerical model that considers habitat factors, including submerged frequency and submerged depth, was established. Based on the long-term data of hydrological observation before and after the impoundment of Three Gorges Reservoir (TGR) and the river topography data in different periods, the suitable habitats of MP community in Hankou floodplain of Wuhan reach in recent 20 years were simulated. The results indicate that the model has greatly reproduced the spatial distribution of MP community in comparison with the observations. Due to the lower flow fluctuation and the decrease of water level at the same flow rate both resulting from the impounding of TGR, the suitable habitats of MP community narrowed and moved to the river with an area decrease of 33.24%. However, the flattening of the topographic slope caused by shoreline utilization contributed to the expansion of the MP community with an area increase of 69.11%. Due to the dominant influence of the latter, the area of MP community has increased by 42.53% compared with the case in 2001. Furthermore, it is found that, if the topography of terrain changes or artificial buildings are located in the inundation frequency with a range of 5%-25%, the two factors, hydrological change and topography change, will have an integrated impact on the habitats of MP community. This kind of integrated effect will even be greater than the sum of two impact factors. The research in this paper shows that human disturbance, such as flood land development, leads to the change of the riparian topography, which may affect the growth conditions of riparian vegetation. These findings deserve the attention of relevant departments when planning, utilizing and protecting the riverine flood plain.