Knowledge Resource Center for Ecological Environment in Arid Area
| 准噶尔盆地南缘柽柳（Tamarix）、梭梭（Haloxylon ammodendron） | |
| 其他题名 | ‘Fertile island’ effect of Tamarix and Haloxylon ammodendron shrubs in south margin of Junggar Basin |
| 李君 | |
| 出版年 | 2007 |
| 学位类型 | 博士 |
| 导师 | 赵成义 |
| 学位授予单位 | 中国科学院新疆生态与地理研究所 |
| 中文摘要 | 在干旱半干旱区，土壤资源在生物、非生物过程作用下富集于灌丛周围，使土壤资源由灌丛覆盖区向灌丛间地逐步递减，从而形成灌木“肥岛（fertile island）”现象。灌木“肥岛”是全球干旱生态系统中的普遍现象，其发生和发展对干旱灌木、草原生态系统的结构和功能都具有重要影响，因此在干旱区生态领域深受关注。\n本文首先从灌木“肥岛”的土壤特征、形成机制和生态效应三个方面分析了有关灌木“肥岛”的研究现状，发现“肥岛”中土壤资源的聚集不仅与物种有关，其形成与发育也与特定的环境条件有关。为此，以准噶尔盆地南缘对准噶尔盆地南缘柽柳（Tamarix spp.）和梭梭（Haloxylon ammodendron）这两种不同地表形态灌木的灌木为对研究对象，探讨了灌木“肥岛”现象的物种效应，从柽柳和梭梭群落不同生境土壤水分、养分的季节动态深入分析了柽柳和梭梭“肥岛”的发育过程。\n对柽柳和梭梭群落中不同生境土壤养分的研究结果表明：1）柽柳和梭梭都存在“肥岛”现象，主要表现在土壤表层，其土壤性状与“岛”外土壤的差异随土壤深度增加而减弱；2）生物性限制土壤养分由“岛”内向外梯度递减，而非生物性限制土壤要素可能高于、也可能低于“岛”外土壤，或者两者无显著差异；3）从“肥岛”的空间尺度来看，柽柳“肥岛”的水平范围可能超出了本身冠幅覆盖区，而梭梭“肥岛”要小于本身冠幅覆盖区，其深度亦小于柽柳“肥岛”；4）相对于不同土壤要素而言，即使是同一物种，其“肥岛”也具有不同的空间范围。总的来看，研究区灌木“肥岛”的发育具有明显的物种效应，相对梭梭而言，柽柳“肥岛”发育更广、更深，养分聚集更明显，其原因主要是柽柳的半球型树冠更利于保护和捕获凋落物，而较多的凋落物输入与土壤结构和土壤养分间的正反馈机制使柽柳冠下加速的生物地球化学循环能达到更广、更深的范围。\n春季雪融水对准噶尔盆地南缘梭梭荒漠具有重要的意义。研究表明雪融水的空间分布在植物个体、群落和典型地貌样带尺度上存在多尺度的分异，其结果使大量雪融水从梭梭基茎周围渗入深层沙土。融雪过程中释放的养分伴随雪融水输入梭梭冠下土壤，是特殊环境下一种独特“肥岛”发育的机制。\n通过对柽柳和梭梭群落中不同生境土壤水分、养分的季节变化以及不同生境土壤水和养分变化过程的对比，结果表明：1）梭梭群落中表层土壤水分从融雪后的自相关格局到旱季后演变为随机分布格局，柽柳冠下土壤水分始终高于灌丛间地，但干旱季节土壤表层都极干燥；2）柽柳群落中冠下和灌丛间地土壤养分变化过程差异明显，而梭梭冠下土壤养分的变化过程和灌丛间地基本一致，冠下土壤C、N水平冬、春季最高，春季融雪后逐步递减，到积雪前的秋季达到谷值；3）无论是柽柳和还是梭梭群落，冠下和灌丛间地土壤养分的差异在冬、春季最明显，夏、秋季差异相对较小。这些结果表明，研究区灌木“肥岛”的土壤养分聚集过程主要发生在冬、春季。夏、秋干旱季节灌木“肥岛”的养分聚集作用不明显，主要在于极干燥的土壤表层限制了凋落物的分解，从而制约了土壤养分资源的输入；另一方面夏、秋季植物吸收又增加了土壤养分资源的输出。由此说明，冬、春季的积雪覆盖下的土壤养分循环过程以及融雪过程对灌木“肥岛”的养分聚集具有重要意义。然而，野外调查表明，积雪覆盖对柽柳和梭梭“肥岛”养分聚集的作用机制却不尽相同：冬季柽柳冠幅热保护作用下加速的生物地球化学循环过程对对柽柳“肥岛”的发育具有重要意义；对梭梭而言，融雪过程中释放的养分随雪融水的多尺度分异而渗入梭梭冠下深层沙土，这种养分的物理运移机制可能对梭梭“肥岛”的发育更重要。 |
| 英文摘要 | That soil resources are enriched under shrub canopies by a combination of biotic and abiotic processes, thus forming a gradient of resources from the canopied areas toward the interspaces between shrubs, the so-called ‘fertile island’, is a common feature worldwide in arid and semiarid regions. Since the development of shrub ‘fertile island’ greatly influences the structure and function of the arid ecosystems, it is of great interest in ecology. \nThe features, development mechanisms and ecological effects of the ‘fertile island’ were reviewed. Previous studies showed that the soil resource enrichment under shrub canopies were not only species-dependent, but also related to the given environment. Therefore, the present study explored the shrub species effect on the ‘fertile island’ development by two dominant shrub species (i.e., Tamarix spp. and Haloxylon ammodendron) with different above-ground appearance in south margin of Junggar Basin, Xinjiang, China. Furthermore, ‘fertile island’ development processes for the two shrub species were probed by comparing soil moisture and nutrient dynamics at the different microhabitats in the shrub communities.\nTo examine the species effect on this phenomenon, soils were sampled from canopied area, vertically projected limit of crown margin and interspaces between shrubs in Tamarix spp. and H. ammodendron communities for physical and chemical analyses. The results indicate that 1) ‘fertile islands’ develop both under Tamarix and H. ammodendron shrubs, with the differences of soil properties between ‘islands’ and interspaces decreasing with depth; 2) there are gradients in biologically-limiting nutrients from ‘islands’ toward interspaces, whereas the biologically-unlimited elements are more or less or equally distributed in ‘islands’ relative to interspaces; 3) in terms of the spatial scale, ‘islands’ of Tamarix spp. may extend out of the canopied area while ‘islands’ of H. ammodendron are relatively smaller and more shallow than that of Tamarix spp.; 4) spatial sizes of the ‘islands’ for different soil indices vary even for the same shrub species. In conclusion, Tamarix ‘islands’ have more nutrients enriched, larger area and greater depth in comparison to that of H. ammodendron. These differences are greatly due to the different morphologies of the two species, with the hemispheroidal crowns of Tamarix spp. more efficiently capturing and maintaining litter than the Y-shaped H. ammodendron crown. As a result, the positive feedbacks among higher litter input, soil structure and nutrient storage make the accelerated biogeochemical cycling reach a greater spatial extent under Tamarix shrubs.\nSnowmelt in spring is of importance for the H. ammodendron desert in south Junggar Basin. The results indicate that the heterogeneity of snowmelt distribution occurs at the shrub individual, community and typical topography transect scale, leading more snowmelt infiltrating to the deeper sand layer around H. ammodendron stem. Accompanying the snowmelt movement, nutrients released from snowpack are enriched under H. ammodendron canopies, which is a particular mechanism for the H. ammodendron ‘fertile island’ development in the given environments.\nSoil moisture and nutrient seasonal dynamics at different microhabitats and their comparisons between microhabitats show that 1) spatial distribution of soil moisture in upper layer in H. ammodendron community evolve from the autocorrelation pattern in spring, when soil moisture is relatively higher after snow-thawing, to the stochastic pattern in the dry summer and autumn, whereas in the Tamarix community, soil moisture under canopies is always higher than the interspaces between shrubs; 2) soil nutrient dynamics under Tamarix canopies differ from that of interspaces, while soil nutrient dynamics are similar between the two microhabitats in H. ammodendron community, with the soil C and N level higher in winter and spring, gradually decreasing after snow-thawing and lower in autumn before snow cover occuring; 3) the soil nutrient differences between microhabitats are greater in winter and spring than in summer and autumn, regardless of shrub species. These results suggest that the soil resource enrichment under canopies occurs to a great extent in the winter and spring. That the soil enrichment process under canopies in dry season is not so significant as in cool season is mainly resulted from the extremely dry top soil layer, which restricts the decomposition of litter over the soil surface, thus decreasing the soil C, N input. Another reason may be the higher nutrient uptake of plants in summer and autumn that increase the soil nutrient output. These evidences suggest that the soil nutrient cycle under snowpack in winter and spring plays a significant role for the soil resource enrichment of the shrub ‘fertile island’ in the study area. However, the field observations indicate that the winter snowpack influence the soil nutrient enrichment in different mechanisms for Tamarix and H. ammodendron ‘fertile island’. For, the Tamarix shrubs, the ‘fertile island’ development may rely to a great extent on the heat-protection effect of their crowns promoting the accelerated biogeochemical cycle under them in winter. Whereas for the H. ammodendron ‘fertile island’ development, the physical transport mechanism that nutrients released from snowpack are concentrated under canopies might be more important. |
| 中文关键词 | 荒漠 ; 积雪 ; 三工河流域 ; 生境 ; 土壤水分 ; 土壤养分 ; 异质性 |
| 英文关键词 | Desert Heterogeneity Microhabitat Sangong River Basin Snowpack Soil nutrient Soil moisture |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286585 |
| 推荐引用方式 GB/T 7714 | 李君. 准噶尔盆地南缘柽柳（Tamarix）、梭梭（Haloxylon ammodendron）[D]. 中国科学院新疆生态与地理研究所,2007. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [李君]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [李君]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [李君]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
