Knowledge Resource Center for Ecological Environment in Arid Area
| 沙地樟子松人工林G-SPAC系统水分动态研究 | |
| 其他题名 | The water dynamic of G-SPAC system in artificial forest of Pinus sylvestris var. mongolica on sandy land |
| 刘亚 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 阿拉木萨 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 樟子松因其耐寒、耐旱、耐贫瘠、生长迅速等优良特性在我国北方沙区得到大量推广，对我国北方沙区荒漠化防治具有重要意义。针对沙地樟子松人工林出现严重衰退的问题，前人的研究多认为水分是樟子松衰退的重要原因。本文以科尔沁沙地樟子松人工林为研究对象，从水分利用角度出发，系统分析樟子松林地下水-土壤水-植物-大气连续体（G-SPAC）系统各部分水分状况、动态变化和水分运移分配，并结合根系特征，阐述各部分水分与根系的相互作用和关系，分析樟子松衰退的水分机制。主要研究结果表明：（1） 2015年5月至9月，研究区降雨呈现小数量、低强度的特征；穿透雨、树干茎流和林冠截留分别占同期降雨量的69.28%、1.26%和29.46%；林地有效降雨补给量为117.67mm，占降雨量的70.54%。穿透雨和树干茎流发生阈值分别为0.85mm和2.44mm降雨量。降雨再分配比例受降雨等级影响，当降雨等级为15～20mm时，林内有效降雨比例最高（90.35%）。（2） 樟子松日蒸腾速率在0.95-30.38 g. (100g)-1.h-1之间，平均月蒸腾速率在4.60-21.09 g. (100g)-1.h-1。蒸腾日变化呈现先增加后减小的“单峰”特征，樟子松蒸腾速率在背阴和向阳面表现出差异，背阴面呈明显的对称性，峰值出现在正午；向阳面的峰值出现于10时左右。蒸腾月变化呈现5-7月缓慢增加、8-10月迅速降低的单峰特征，阳面呈现“增-减-增-减”的双峰特征，阴面呈现“减-增-减”特征。蒸腾速率的大小与光照和温度有关，且前者作用大于后者；温度过高可能对蒸腾有抑制作用。（3） 依据生物量和分布特征，樟子松根系可分为浅层(0-40cm)、中层（40-90cm)、深层（90-150cm)。其中，浅层和深层是根系吸收水分（和养分）主要区域。樟子松根系死亡现象严重，特别是深层根系，死根与活根的比值达到0.65。根系分布与土壤容重、紧实度、土壤粒径、深度、土壤水分等土壤物理因素有关，但影响不同类型根系分布的因素不尽相同。细根分布与生长季初期水分状况（5月土壤水分）有关，与平均土壤水分相关性未达到显著性水平。（4） 樟子松林地土壤水分在垂直方向上可以分为浅层（0-40cm）、中层（40-90cm)、深层（90-150cm）和地下水补给层（150-200cm)。各层土壤水分在空间和时间上变化规律不同：浅层土壤水分受降雨影响大，5-7月增加，7-9月减少，并随深度而减少；中层水分含量低，变化不大；深层土壤水分随时间而减小，在空间上呈先增加后减小的趋势；地下水补给层土壤水分受地下水埋深影响，5-9月持续减少，9-10月略有回升。整体而言，樟子松林地土壤水分在5-9月迅速减少，9-10缓慢增加；土壤水分随深度的增加而增加，且土壤水分状况较差。地下水埋深在5-9月迅速增加，9-10月略有减少。在生长季，地下水位最大下降97cm，地下水补给高度60-80cm。（5） 地下水埋深不改变土壤水分月变化趋势，但影响平均土壤水分含量。地下水埋深影响樟子松幼苗生物量和根系分布，樟子松幼苗总生物量、地上生物量、叶生物量均随地下水埋深的增加而减少，根系生物量和根密度则表现为先减少后增加。随着埋深的增加，幼苗根系深度和根冠比均增加，并且倾向于将生物量更多的分配到根系。综上所述，科尔沁沙地樟子松林地水分来源主要为降水和地下水，其中降水的70.54%通过穿透雨及茎流补充土壤水，地下水的水分供给是成龄樟子松长期稳定生存生长的必要条件。樟子松在利用降水的基础上，消耗地下水资源，引起地下水位迅速过度下降，导致短期内地下水对根际土壤水分补给不足，加之降雨有效补给较少，诱发深层地下水补给层土壤中根系的大量死亡，引起樟子松吸收能力下降、供水不足，在强烈的蒸腾作用耗水过程中，最终导致樟子松生理性水分亏缺，这可能是科尔沁沙地樟子松林地衰退的主要原因和过程。因此，对于科尔沁沙地樟子松人工林衰退问题，地下水位过度下降是其根本原因，根际土壤水分不足是其主要原因，根系大量死亡是其间接原因，樟子松水分亏缺是其直接原因。 |
| 英文摘要 | Due to its excellent features, such as drought-tolerance, cold-resistant, infertility-tolerance and fast-growth, Pinus sylvestris var. mongolica (MP) has been spread widely and is of significance to desertification control in sand regions, northern China. On the issues of the serious decline of MP forest, many researchers hold the opinion that the water is one of the key reason. In this paper, taking MP artificial forest in Horqin sandy land as the objection of study, we studied systematically the water status, dynamic change, and allocation, stated the interaction and relationship between water and roots, and analyzed the water mechanism of the decline of MP.The main results are as follows: (1) The rain in our study area shows features of small-amount and low-intensity. The throughfall, stemflow, and interception accounts for 69.28%, 1.26%, and 29.46% of rainfall, respectively. And the net precipitation in forest is 117.67 mm, 70.54% of total rainfall. The throughfall and stemflow occurs when the rainfall reaches 0.85 mm and 2.44 mm, respectively. Additionally, the ratio of rainfall partitioning is affected by the rainfall degree, and the ratio of net precipitation is the highest when the degree is 15-20mm. (2) The transpiration rate of MP is between 0.95 and 30.38 g. (100g)-1.h-1, and the average monthly of that is 4.60-21.09 g. (100g)-1.h-1. The daily variation of transpiration shows single-peak feature, and has a difference between shade and sunny side. The daily variation in shade have an obvious symmetry, and the peak appears at midday, while that in sunny side arises at ten clock. The monthly variation increases slowly from May to July, and decreases from August to October, while up-down-up-down in sunny side and down-up-down in shade side. The transpiration rate is related with light and temperature, and the light has more influence than temperature. What is more, higher temperature may have a negative effect on transpiration. (3) The roots of MP can be divided into three layers, superficial layer (A,0-40cm), middle layer (B, 40-90cm), and deep layer (C,90-150cm). Among those layers, A and C is the main region of absorbing water and nutrition. The phenomenon of roots death is pretty serious and bad, especially in C layer which the ratio of death root to live roots is 0.65. The root distribution is connected with soil bulk density, soil compaction, soil texture, depth, and soil moisture, and there are some distinctions in different root types. The distribution of fine roots is related with water status in the early growing season, not with average soil moisture.(4) The soil moisture of MP forest can be divided into four parts, superficial layer (A,0-40cm), middle layer (B, 40-90cm), deep layer (C,90-150cm), and groundwater-recharge layer (150-200cm). Soil water content in A layer is affected by rainfall, increases from May to July, decreases from July to October, and falls with depth. In B layer, the value is low and less change. However, in C layer, the soil moisture goes up first and then down with depth, drops with time. Moreover, soil moisture in D layer, influenced by groundwater depth, reduces linearly from May to September, and raises again on September and October. As a whole, soil water content in MP forest decreases rapidly and quickly from May to September, and raises again slowly at the end of growing season, and increases with depth. In addition, the groundwater depth drops by 97cm, and the height which groundwater can recharge is about 60-80cm.(5) groundwater depth cannot change the monthly variation trend of soil moisture, but influence the average soil water content. And it also affects the biomass and root distribution of MP seeding. The total-, above-, and leave-biomass reduce with the depth increasing, while root biomass and density goes down first and then up. With the increasing depth, the seeding root depth and ratio of root to shoot enlarges, and there are more biomass shifting to root.In conclusion, the main water resource of MP forest in Horqin sandy land is rainfall and groundwater, and only 70.54% of rainfall can replenish soil water via throughfall and stemflow. The supply of groundwater is the key requirement to support and maintain the exist and growth of MP in the long run. MP, on the basis of using rainfall, consumes the resource of groundwater, which cause the groundwater table descending rapidly and excessively and water supply from groundwater to rhizosphere soil regions. Those, adding less replenishments from rainfall, may induce lots of roots in deep layers to die, which further lower the ability of absorbing water and water supply. Less available water and more intense transpiration finally leads to physiological water deficit of MP. All of those may be the main reason and process of decline of MP artificial forest. Thus, for the issue of decline, the rapid fall of groundwater table is primary cause, rhizosphere soil moisture insufficient is main cause, root death is indirect cause, and the water deficit of MP is the direct cause. |
| 中文关键词 | 科尔沁沙地 ; 樟子松 ; 水分 ; 根系 ; 地下水 ; 降雨再分配 ; 蒸腾 |
| 英文关键词 | Horqin sandy land Pinus sylvestris var. mongolica water root groundwater rainfall partitioning transpiration |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 森林培育 |
| 来源机构 | 中国科学院沈阳应用生态研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287747 |
| 推荐引用方式 GB/T 7714 | 刘亚. 沙地樟子松人工林G-SPAC系统水分动态研究[D]. 中国科学院大学,2016. |
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