沙埋对策勒绿洲-沙漠过渡带两种建群种植物特征与格局的影响

Two dominant species characteristics and spatial point pattern affected by sand burial in Cele oasis-desert ecotone

以塔克拉玛干沙漠南缘策勒绿洲-沙漠过渡带为研究区,在半固定沙地、半流动沙地和流动沙地选择了3个50 m×50 m的典型样地,分别代表轻度、中度和强度3种沙埋条件。每个样地内确定植物种类组成,测定两种建群种植物的高度和冠幅,同时对相应的灌草丛沙堆进行形态测量;利用全站仪采集所有植物的空间点坐标数据,运用Ripley’s K(t)函数点格局分析,研究沙埋对两种建群种植物特征与格局的影响。结果表明:随着沙埋强度的增加,疏叶骆驼刺和花花柴两个建群种植株数量减小,数量比例从以花花柴为主向以骆驼刺为单优势种群方向发展,死亡植株比例从半固定沙地的14.5%升高到流动沙地的40.3%;疏叶骆驼刺和花花柴植株高度和冠幅从半固定沙地到半流动沙地有所降低,但疏叶骆驼刺在流动沙地中又表现出增加趋势;对应的灌草丛沙堆体积随沙埋强度增加而变大,沙堆形态从多种类型并存向带有风影沙尾的蝌蚪形为主转变;花花柴和骆驼刺均以聚集分布应对风积沙埋的威胁,两种植物的种群间关系并不明显。总体来看,风积沙埋有碍于两种建群种植物的繁殖与生长,但骆驼刺具有更强的耐沙埋能力,特别是在流动沙地中留存下来的骆驼刺植物单体明显大于半固定和半流动沙地。集群分布的植物沙堆往往从基部合并,导致相对密集的植物分布区总与局部凸起的地形相对应,是风沙环境中植物群体与风积沙埋相互作用的结果。

In order to study the effects of sand burial on Alhagi sparsifolia Shap. and Karelinia caspia Less., two dominant species in Cele oasis-desert ecotone at the southern rim of the Taklimakan Desert, 3 sample plots with 50 m x 50 m were selected in the semi-fixed sandy land, semi-shifting sandy land and （Pall.） typical shifting sandy land, representing the slight, moderate and intensive burial conditions, respectively. In each plot the species composition and their spatial positions were investigated, the population characteristics （the number, height and crown area） of the two plant species and morphological parameters of the Phytogenic Mounds （Nebkhas） in the three plots were measured as well. Ripley＇s K （t） function was used to analyze the spatial point pattern of the plants. The results show as follows：the plant number decreased with the sand burial enhanced, as the plant density was 12.5 clump/100 ㎡ at the semi-fixed sandy land, 6.8 clump/100 ㎡ at the semi-shifting sandy land and 1.4 clump/100 ㎡ at the shifting sandy land. The percent of the dead plant increased from 14.5% at the semi-fixed sandy land to 40.3% at the shifting sandy land. The Nebkhas volume increased with increasing sand burial intensity, while the morphological types of Nebkhas changed from coexistence of 4 different types into wind shadow dune type. The plant height and crown area decreased from 56.8 cm and 8 815.2 c㎡ for A. sparsifolia and 62.9 cm and 9 976.8 c㎡ for K. caspia at the semi-fixed sandy land, to 49.3 cm and 6 464.6 c㎡ for A. sparsifolia and 48.0 cm and 5 984.0 cm2 for K. caspia at the semi-shifting sandy land, but increased to 66.4 cm and 32 065.1 cm： for A. sparsifolia at the shifting sandy land. The two dominant species show an aggregated distribution and insignificant interspecies relation in the sand burial environment, but a nearly significant positive spatial association at the small scale （〈5 m） in the semi-fixed sandy land. Generally speaking, the severe sand accumulation has negative effects on the plant reproduc tion and growth, A. sparsifolia species has a greater tolerance to sand burial. Plants in aggregated distribution are al ways corresponding to the higher topography as a result of the interaction between the plants growth and wind-blown sand activities.