绿洲荒漠过渡带不同演替阶段白刺灌丛植被和沙堆形态特征相关性分析

Analysis of the correlation between vegetation and morphological characteristics of Nitraria tangutorum Bobr. nebkhas at different succession stages in a desert-oasis ecotone

在实地调查和形态测量的基础上,应用统计学原理和方法,研究民勤荒漠绿洲过渡带4种不同演替阶段白刺灌丛沙堆植被、形态和尺度特征,分析各演替阶段主要特征间的相关关系,阐明演替过程中沙堆主要特征间的演变趋势.结果表明:白刺灌丛的整体生长状况和植被盖度均随演替的进行呈先升高后降低的态势,发育阶段植被生长状况最好,稳定阶段植被覆盖度最高,而活化阶段两者均显著最低(P<0.01);沙堆底面积和体积大小均随着水平尺度的增加而增加, 4个演替阶段沙堆体积大小排序为活化阶段>发育阶段>稳定阶段>雏形阶段;灌丛植被和沙堆形态特征间的相关性在不同演替阶段均不同:沙堆盖度与高度、生长状态之间均呈显著正相关关系,但与枯枝率呈显著负相关关系;沙堆尺度大小、迎风坡长与沙堆高度的相关性随演替逐渐增强.不同演替阶段主要指标间的回归拟合曲线均不相同,主要以直线方程、二项式和乘幂3种曲线变化为主:雏形和发育阶段沙堆水平尺度和高度之间为二项式关系,稳定和活化阶段为幂函数关系,而沙堆体积与高度之间均为幂函数关系;灌丛沙堆土壤质地的变化随沙堆的演替而逐渐退化,发育、稳定阶段沙堆土质总体良好,而活化阶段土质退化明显.各演替阶段沙堆土质的变化与地上植被的退化表观一致.

On the basis of field investigation and morphological measurement, statistical principles and methods were applied to analyze the vegetation and morphological characteristics of the Nitraria tangutorum Bobr. nebkhas in four different succession stages located at the Minqin desert-oasis ecotone, then to study the vegetation, morphological and scale characteristics of nebkhas, finally, to clarify the correlations and trends among the main indicators according to the process of succession stages of nebkhas.The results showed that: the growth status and vegetation coverage of nebkhas increased at first and then decreased with the processing succession, the vegetation growth status was the best at the developing stage while the vegetation coverage was the highest at the stable stage;the horizontal scale, bottom area and volume of nebkhas gradually increased with the increasing horizontal scale, the grade of nebkhas size in four succession stages from large to small was activating stage>developing stage>stable stage> embryonic stage. The correlation between vegetation and morphological characteristics changed with succession. There was a significant positive correlation between coverage and height or the growth status of nebkhas, but a significant negative correlation with the deadwood rate. The correlations between the horizontal scale, length of the windward and height of nebkhas were gradually enhanced with the succession.The regression fitting curves of the main indicators in different succession stages were different. In the embryonic and developing stages, there were binomial relationships between the horizontal scale and height of the nebkhas, but there were power functions, but only in the stabilization and activating stages,while the relationship between the nebkhas volume and height in each succession stage showed the trend of the power function curve. The soil texture of the nebkhas was gradually degraded with the process of different succession stages and the soil quality of developing and stabilization stages was generally good,but obviously degraded in activating stage. The soil quality of each succession stage was consistent with the degradation of the aboveground vegetation.