Knowledge Resource Center for Ecological Environment in Arid Area
| 河西走廊绿洲边缘梭梭人工固沙植被自组织过程研究 | |
| 其他题名 | Self-organized Patterns of Haloxylon ammodendron Artificially-planted Vegetation in an oasis edge of Hexi Corridor |
| 郑颖 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 赵文智 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 干旱荒漠区，降水量稀少，植被稀疏，植被与裸地多呈斑块状镶嵌格局，这是植被长期适应水分匮乏环境的结果。为了抵御风沙侵袭，1970年代以来，在河西走廊绿洲边缘建立了大量的人工固沙植被。人工固沙植被基本以固定株行距栽植，建植初期基本规则分布，但随着植被的生长发育，土壤水分等非生物因素和生物因素的共同作用下，导致人工固沙植被经历自组织过程，形成特定的分布格局。本文以河西走廊中段临泽北部绿洲边缘梭梭（Haloxylon ammodendron (C. A. Mey.) Bunge）人工固沙植被为研究对象，研究不同时空尺度上梭梭人工固沙植被的自组织过程，探究梭梭自组织过程和主要的影响因素，以加强对河西走廊绿洲边缘及相似地区人工固沙植被演变驱动机制的认识，为降水量150 mm以下地区人工固沙植被的设计与布局提供理论支持。主要结论如下：1. 临泽北部绿洲边缘植被覆盖度时空变化从1990年至2016年，临泽北部绿洲边缘植被覆盖状况有明显好转的趋势，极低植被覆盖区（VFC ≤ 10%）面积显著减少，农田（VFC > 70%）面积一直呈稳定扩张趋势，由2246 km2增加至3527 km2，人工固沙植被（30% < VFC ≤ 70%）面积经历了一个先增加，后减小，再增加的过程，面积由1990年1171 km2增加至2016年的1781 km2。2. 梭梭人工固沙植被群落和种群特征演变种植初期，梭梭人工固沙植被的栽植密度一般为2960株.hm-2，盖度一般在30%左右。从种植初期到种植20年左右的梭梭群落，梭梭种群密度减小了60%左右，种植30年左右的梭梭群落，出现大量的天然更新幼苗，导致梭梭种群密度显著增加，随后由于梭梭幼苗和部分成年树的死亡，密度再次下降。梭梭种群特征空间异质性的拐点出现在种植30年左右的群落，种植30年左右的梭梭植株冠幅达到最大，随后由于枯死枝条增加，冠幅有所减小；株高基本保持稳定，不再增加；基径仍然呈增加趋势。随着梭梭人工固沙植被的发育，物种单一的梭梭群落逐渐演变为包括灌木层、灌木幼苗层、草本层的多层次灌草群落，草本层优势物种为一年生雾冰藜（Bassia dasyphylla (Fisch. et C. A. Mey.) Kuntze），草本植物种类、密度、盖度、生物量均显著增加。3. 梭梭人工固沙植被种群空间格局演变采用点格局分析方法研究发现，随着梭梭人工固沙植被的发育，梭梭的种群空间分布格局由最初的聚集分布经由随机分布最终向聚集分布转变。采用低空无人机航拍技术量化梭梭景观格局，结果显示种植5-30年的梭梭群落，活力强的梭梭斑块（以绿色枝条为主的斑块）的面积一直呈增加趋势，裸地斑块面积一直呈减小趋势，种植30年之后，活力强的斑块聚集度大幅减小，而活力弱的（以灰色枝条为主的斑块）斑块和裸地斑块聚集度随梭梭种植年限的增加，基本不变。4. 梭梭人工固沙植被自组织过程的影响因素土壤水分的变化是导致梭梭人工固沙植被格局变化的主要驱动因素之一。固沙植被建立初期，0-10 cm表层土壤含水量一般为1.1%-2.3%，梭梭可利用的水分主要是依靠降水补充的浅层土壤水分，不论是灌丛间裸地斑块还是灌丛下方，深层土壤含水量均高于浅层土壤含水量，土壤水分对梭梭种群格局的影响相对较小。当梭梭人工固沙植被建立20年左右时，梭梭群落的土壤水分格局发生了改变，深层土壤含水量开始逐渐下降，并且随着植被固沙年限的增加，这种趋势更加明显。当固沙植被建立40年左右时，土壤水分的格局再次发生改变，不论是灌丛间裸地斑块，还是灌丛下，深层土壤水分含量开始逐渐增加，而表层土壤水分含量开始逐渐减小。土壤水分的变化，是导致梭梭人工固沙植被生长发生分异，由规则分布的格局向斑块状格局演变的主要驱动因素。对地下水的竞争性利用也是梭梭人工固沙植被自组织的一个主要驱动因子。随着梭梭人工固沙植被的生长发育，地下水对梭梭水分来源的贡献率显著增加。土壤水和地下水是种植10年的梭梭共同的水分来源，而种植20年以上的梭梭主要的水分来源于地下水。梭梭种群中个体竞争作用明显，不同年龄梭梭可利用的水分来源不同，导致梭梭种内竞争强度会随梭梭个体水分来源的变化而改变。种植5-10年、10-20年、20-30年的梭梭，种内竞争作用可能是影响梭梭生长、存活以及空间格局演变的主导因素，种植30-40 年和种植年限大于40年的梭梭，不同径级梭梭之间的非对称竞争和非生物因素的共同作用，导致了梭梭种群空间分布格局的演变。 |
| 英文摘要 | The two-phase mosaics of vegetation alternating with bare ground，was frequently observed in arid ecosystem. Theoretical studies suggest that this range of spatial patterns is the result of self-organization as a consequence of resource redistribution. The sand-fixing vegetation system under no-irrigation condition was established in the middle of the Hexi Corridor since 1970s，where annual precipitation is about 120 mm. Haloxylon ammodendron (C. A. Mey.) Bunge is one of the important and commonly used sand-fixing species，while the mobile dunes have been effectively stabilized，H. ammodendron plantations change both in growth status and on spatial patterns，an unique self-organized pattern have has been observed. However，little information is available on the self-organization process of artificial vegetation in this area. To reveal the spatial patterns of H. ammodendron and preliminary exploring the causes of self-organization，fifteen 0.3-ha (50 m × 60 m) permanent plots were established. Point pattern analysis and unmanned aerial vehicle imagery were used to reveal pattern evolution，soil moisture and nutrients were examined，and water sources at different stand age was determined by examining stable isotopic ratios of oxygen (δ18O)，relative intensity of competition with the population growth was examined by a competition index which is called V_Hegyi index put forward by Tang Mengping. Our results showed that:(1) the H. ammodendron had been experienced significant degradation for planted about 20 years, The area of farmland in this region has been steadily expanding, From 1990 to 2016, new sand-fixing forests have been established continuously . (2) the coverage of shrub layer of the artificial sand-fixing vegetation of H. ammodendron at the initial stage of planting is generally about 30%, the density is generally 2960 per hectare. the coverage of shrub layer was maximized at 70% at about established 25 years，the herbaceous coverage had been increasing to 25% after 40 years, a large number of regenerating seedlings appeared after planted 30 years, resulting in a significant increase in the density of the H. ammodendron. The density then decreased again due to the death of seedlings and part of the adult tree. The turning point of the spatial heterogeneity of the characteristics of H. ammodendron populations occurs in the communities where the plants are planted for about 30 years, the crown of H. ammodendron reached the maximum, and then the crown was reduced. The plant height remained stable and no longer increased, and the basal diameter still showed an increasing trend. With the development of H. ammodendron community, the species of H. ammodendron community gradually evolved into a multi-level shrub-grass community including shrub layer, shrub layer and herb layer.(3) With the development of H. ammodendron community, the spatial distribution pattern of H. ammodendron population changes from the initial aggregation distribution to the aggregation distribution through random distribution. For 5-30 year-old H. ammodendron community, the area of active H. ammodendron plaques (mainly green shoots) has been increasing, the area of bare land has always been decreasing. For more than 30 year-old Haloxylon community, the clustering degree of strong vitality plaques is greatly reduced, while the degree of aggregation of weakly active plaques (gray-based patches) and bare ground patches is basically unchanged with the increase of H. ammodendron cultivation time. (4) The change of soil moisture caused the change of vegetation pattern of H. ammodendron. At the initial stage of the establishment of sand-fixing vegetation, the 0-10 cm surface soil moisture content is generally 1.1%-2.3%. The water used by H. ammodendron is mainly based on shallow soil moisture supplemented by precipitation. Whether it was bare land between shrubs or land under shrub, the deep soil water content was greater than the shallow soil moisture content, and the soil moisture had a relatively small impact on the vegetation pattern. When the artificial sand-fixing vegetation of H. ammodendron was established about 20 years, the soil moisture pattern changed. The deep soil water content began to gradually decline, and this trend became more apparent as the vegetation fixed period increased. When the sand-fixing vegetation was established for about 40 years, the pattern of soil moisture changed again. Whether it was bare land between shrubs or land under shrubs, the deep soil moisture content gradually increased, and the surface soil moisture content began to gradually decrease. The change of soil moisture is the main driving factor that causes the growth of H. ammodendron vegetation to be different, and evolution from a uniformly distributed pattern to a patchy pattern. The competitive use of groundwater is also a major driver for the self-organization of artificial sand-fixing vegetation of H. ammodendron. With the growth and development, the contribution rate of groundwater to the water source of H. ammodendron has increased significantly. Soil water and groundwater are the common source of water for the 10-year-old H. ammodendron, and the main water source of H. ammodendron that is planted for more than 20 years is derived from groundwater. The individual competition in H. ammodendron population is obvious. The different sources of available water from H. ammodendron in different ages resulted in the change of the competition intensity of the H. ammodendron population. In the 5-10 year, 10-20 year, and 20-30 year stages of H. ammodendron population, competition among individuals within the species may be the dominant factor affecting the growth, survival, and spatial pattern evolution of H. ammodendron, while the asymmetric competition between H. ammodendron of different diameters and non-biological factors, led to the evolution of the spatial distribution pattern of H. ammodendron population grown in 30-40 years and planted over 40 years.The spatial patterns evolution of H. ammodendron is a result of self-organization，the general trend is from uniform distribution to patches pattern. A major driving factor is water acquisition patterns in H. ammodendron differed with stand age. |
| 中文关键词 | 梭梭 ; 人工固沙植被 ; 绿洲边缘 ; 自组织过程 |
| 英文关键词 | H. ammodendron， artificial sand fixation vegetation， oasis edge， self-organization process |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288126 |
| 推荐引用方式 GB/T 7714 | 郑颖. 河西走廊绿洲边缘梭梭人工固沙植被自组织过程研究[D]. 中国科学院大学,2018. |
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