腾格里沙漠东南缘不同年代固沙区根系分布

2010年8月,选择腾格里沙漠东南缘1964年、1981年和1990年建立的人工固沙区为对象,以流动沙丘和邻近的天然植被区为对照,利用根钻取样法研究了不同年代固沙植被区根系的3.0m剖面的分布特征.结果表明:单位土地面积上＜1 mm的活根、全部活根、＜1 mm的死根和全部死根的重量密度和长度密度在不同样地间存在着显著差异(p＜0.05)；流沙、1990年、1981年、1964年固沙区和天然植被区全部活根重量密度分别为2.9±2.2、164.7±46.5、461.3±83.6、440.4±81.8g.m-2和350.0±132.5 g·m-2,5个样地全部死根重量密度分别为4.9±2.8、58.7±15.8、390.9±57.9、492.5±252.2 g·m-2和214.4±29.9 g.m-2；根长密度也表现为相似的变化趋势.单位土壤体积的根系重量密度和长度密度随着土层加深而递减,植被区0～1.0 m土壤层活根的累积重量密度和长度密度在全部活根中的比例均超过70.0％,其中以天然植被区最大,流沙区则不超过25％；死根也表现为相似的趋势,只是比例有所降低.根鞘占全部根系生物量的比例非常不稳定,流沙区的最大,为94.3％,而1981年植被区的只有0.5％,1964年、1990年固沙区和天然植被区分别为29.9％,70.3％和58.9％.

Root Distribution of Sand-Binding Vegetation in the Southeastern Tengger Desert, China

The main objective of the present study was to assess the root system distribution in 0-3.0 m profile at revegetated areas established in 1964, 1981 and 1990 at the southeastern edge of the Tengger Desert, respectively. The experiment was conducted in August, 2010. We chose moving sand dune and the nearby natural vegetation area as control. Soil core was used for collecting roots. Significant difference were found in root weight density and root length density of total live roots, live fine roots (<1 mm), total dead roots and dead fine roots (<1 mm) per unit land area (m2) between different vegetation areas. The root weight density and root length density of total live roots in moving sand area, the revegetated areas that were established in 1990, 1981, 1964 and natural vegetation area were 2.9±2.2, 164.7±46.5, 461.3±83.6, 440.4±81.8 g·m-2 and 350.0±132.5 g·m-2, respectively. Meanwhile, the root weight density and root length density of total dead roots were 4.9±2.8, 58.7±16.8, 390.9±57.9, 492.5±252.2  g·m-2 and 214.4±29.9 g·m-2, respectively. The root length density showed the similar tendencies. The root weight density and root length density per unit soil volume (m3) decreased with soil depths. Proportion of accumulated weight density and length density of live roots and live fine roots (<1 mm) in 0-1.0 m soil layer to the total live roots exceeded 70.0% in vegetation areas. The maximum proportion appeared in the natural vegetation area, while the smallest proportion was in the moving sand area with a value less than 25%. Similar trend has also been observed in the proportion of dead roots, however, the proportion slightly decreased. Proportion of rhizosheath to the total root biomass was instable. The maximum value was 94.3% in the moving sand area and minimum value was only 0.527% in the revegetated area established in 1981. The values in the revegetated areas established in 1964 and 1990 and the natural vegetation area were 29.9%, 70.3% and 58.9%, respectively.