藏锦鸡儿群落土壤资源空间异质性

 在内蒙古高原, 藏锦鸡儿(Caragana tibetica)群落分布在草原向荒漠的过渡带上, 在植被区划中常作为由草原进入荒漠的指示物种。藏锦鸡儿是一种旱生垫状矮灌木, 由于其垫状生物学特性, 在地表覆沙的生境中常形成较均匀的、非常醒目的灌丛沙堆。不同大小的灌丛沙堆可对应其不同的发育阶段, 选取不同大小的藏锦鸡儿灌丛沙堆, 划分成小、中、大3组, 小、中两组灌丛沙堆对应其发育阶段, 大沙堆组对应于稳定阶段, 通过测定沙堆间、沙堆内(顶部、中部)及沙堆下的土壤有机质(Soil organic matters, SOM)、全磷(Total phosphorus, TP)和土壤质量含水量(Mass water content of soil, W_m), 分析了藏锦鸡儿群落土壤资源的特点。结果显示, 随着沙堆的发育, 沙堆内和堆下0~20 cm处的土壤有机质、全磷和土壤质量含水量的平均含量呈递增趋势, 大沙堆、中沙堆及堆下0~20 cm处的土壤有机质、全磷和土壤质量含水量的平均含量均大于沙堆间, 小沙堆的土壤有机质、堆下0~20 cm的土壤全磷和质量含水量的平均含量大于沙堆间。不同大小的灌丛沙堆, 在垂直方向上, 土壤有机质、全磷含量基本均呈先增加后减少的趋势, 土壤质量含水量呈递减趋势; 在水平方向, 随着灌丛沙堆的发育, 土壤有机质、全磷和土壤质量含水量在同一部位的同一土层基本呈递增趋势; 不同大小的沙堆表层0~20 cm 处的土壤有机质由顶部、中部、沙堆间依次呈先增加后减小的趋势; 大沙堆和中沙堆的全磷由沙堆顶部、中部、沙堆间依次呈递减趋势, 而小沙堆土壤全磷呈先增加后减少的趋势。随着灌丛沙堆的发育, 藏锦鸡儿灌丛截获的植物残体量呈增加趋势。研究显示, 藏锦鸡儿在发育过程中形成“沃岛效应”, 这种效应不仅表现在沙堆内, 也表现在沙堆下, 同时也引起土壤有机质、全磷和土壤水分的空间异质性分布。

SPATIAL HETEROGENEITY OF SOIL RESOURCES OF CARA GANA TIBETICA COMMUNITY

Aims Caragana tibetica is commonly found in the ecotone between desert steppe and desert of the Inner Mongolian Plateau. It is often used as an indicator species in vegetation regionalization. Due to its dwarf shrub characteristics C. tibetica can easily initiate nebkha (dune) formation in sand-covered habitats. The objective of the paper is to understand C. tibetica ecological adaptability by investigating soil heterogeneity of C. tibetica community. Methods Nebkhas formed by C. tibetica were classified into three size groups. Small and medium nebkhas corresponded to a development stage, and large nebkhas represented a stable stage. Soil organic mater (SOM), total phosphorus (TP) and water content (W_m) were measured at the top each nebkha, in the middle of the nebkha slope, in the interspace between nebkhas, and under the nebkhas. We then also averaged these properties for each nebkha (mean of top and middle samples) Important findings Average content of SOM, TP and W_m of nebkhas and the soil underlying them increased with nebkha age. For large and medium nebkhas and the soil underlying them these properties were higher than that in the interspaces between them. Average SOM of small nebkhas was higher than that in the interspace between them. However，average TP and W_m of the soil underlying small nebkhas were lower than in the interspace. At the top and middle of nebkhas of all sizes, SOM and TP first increased and then decreased vertically while W_m decreased gradually. Plant residues content captured by C. tibetica nebkhas increased gradually with nebkha development stage. We conclude that the “fertility island effect” formed inside and below nebkhas increases as nebkhas develop. At the same time, we found that spatial heterogeneity of SOM, TP and W_m is high.