基于植被数量分类的排水疏干影响下若尔盖高原沼泽退化特征

2009年，在对若尔盖高原沼泽的生态特征、环境质量考察和排水疏干沼泽样带生态调查的基础上，采用TWINSPAN分类方法，将研究区20个典型沼泽样地划分为原始沼泽、长期排水退化沼泽和短期排水退化沼泽3种类型，每类退化沼泽包含轻度退化、中度退化和重度退化3个退化等级，研究不同程度退化沼泽的植被和土壤退化特征.结果表明: 若尔盖高原沼泽退化主要受排水方式、排水强度和土壤水分梯度的驱动.植物群落退化过程较土壤退化过程变化明显.其中，植物群落水分生态型的结构变化最显著，在长期排水和短期排水的影响下，沼生植物重要值由0.920分别下降至0.183和0.053，中生植物重要值由0.029分别上升至0.613和0.686.土壤对沼泽退化的响应具有滞后性，其理化性质呈一定的变化规律，但差异尚未达到显著水平.土壤水分和氮、钾等养分含量是影响若尔盖高原排水疏干退化沼泽植物物种分布的关键因素.

Degradation characteristics of swamps in Zoige Plateau induced by drainage based on quantitative classification of vegetation

Based on the field survey of swamp ecological characteristics and environmental quality and the ecological investigation of drained swamp transects in Zoige Plateau of Tibet in 2009, twenty typical swamp plots in the Plateau were classified into three types by TWINSPAN, i.e., primary swamp, long-term drained degraded swamp, and short term drained degraded swamp, and each type of the degraded swamps was divided into three degradation grades, i.e., light degradation, moderate degradation, and severe degradation, with the degradation characteristics of vegetation and soil along the swamp degraded gradient studied. The swamp degradation in the Plateau was mainly driven by drainage pattern, drainage intensity, and soil moisture gradient, and the vegetation degradation was more obvious than the soil degradation. In the vegetation degradation, the structural change of hydro-type functional assemblage was most obvious, e.g., the importance value of helophytes under the stress of long-term drainage and short-term drainage decreased from 0.920 to 0.183 and 0.053, while that of mesophytes increased from 0.029 to 0.613 and 0.686, respectively. The soil response to the swamp degradation was in hysteresis, i.e., the soil physical and chemical properties presented definite variations but the differences were not significant among the swamps with different grades of degradation. The results of CCA indicated that soil moisture and nitrogen and potassium contents were the most important factors affecting the plant species distribution in drained degraded swamps in Zoige Plateau.