Institutional Repository of Xishuangbanna Tropical Botanical Garden
| 西双版纳土地覆被变化下的水土流失及其主要影响因素 | |
| Alternative Title | Water and Soil Losses and Its Main Influencing Factors Under Land Cover Change in Xishuangbanna, SW China |
朱习爱
| |
| Thesis Advisor | 刘文杰 |
| 2020 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 中国科学院西双版纳热带植物园 |
| Degree Name | 理学博士 |
| Degree Discipline | 生态学 |
| Keyword | 水土流失，植被覆盖，凋落物，土壤条件，橡胶种植模式 |
| Abstract | 人类对水土资源的不合理利用可能会导致了生态系统严重的水土流失。水土流失是一个发生在地表伴随着能量和物质分散的复杂水文过程，已受到来自生态学、土壤学和水文学等领域科学家的广泛关注。自上世纪60年代以来，西双版纳地区大面积的热带雨林被改种成橡胶林，单一的橡胶种植模式给当地带来经济效益的同时也导致了明显的土壤侵蚀、土地退化和水资源短缺等一系列生态环境问题。为了改善这些负面的环境影响，近年来相关政府和科研机构在该地区建立了不同的胶农复合种植模式，以寻找合理的可持续土地利用方式。本研究通过选取位于中国科学院西双版纳热带植物园内的热带季节雨林、人工雨林、次生林、单层橡胶林及不同胶农复合系统（橡胶/茶叶、橡胶/大叶千斤拔、橡胶/萝芙木和橡胶/可可）为研究对象，采用径流小区和染色示踪等研究方法，分别对不同橡胶种植模式下和对照样地内的土壤溅蚀、水土流失现状及其主要影响因子（植被、土壤和枯落物等）进行了相关研究，探讨西双版纳地区不同橡胶种植模式下的土壤侵蚀特征，揭示土地利用变化对坡面水土流失的影响，阐明凋落物在调控生态系统中的生态水文过程中的作用，为构建可持续利用的环境友好型胶园提供科学依据。结果表明：（1）橡胶树叶片的叶尖滴水大小（3.47 mm）显著低于热带季节雨林树种（3.78 mm）和胶农复系统中的间作植物（4.24–4.54 mm），且叶尖滴水大小与叶尖发育程度呈正相关，相关性强弱因植物种类不同存在差异。热带季节雨林转变为橡胶林，其林内的雨滴动能升高4.8倍，极大增加土壤侵蚀风险；橡胶树间作低矮的经济作物后，林内雨滴动能降低34–75%，对缓解雨滴溅蚀至关重要。（2）与原始热带季节雨林相比，单层橡胶林的土壤孔隙度、持水量、入渗能力、有机质含量、凋落物现存量、植被盖度和叶面积指数明显下降，冠层高度、穿透雨动能显著增加，季节雨林和单层胶林的土壤溅蚀分别为3.79 g、184.29 g；胶农复合系统土壤、植被和凋落物条件得到的改善，土壤溅蚀量减少86–97%。与保留凋落物相比，剔除地表凋落物之后，土壤溅蚀增加了2–12倍。（3）单层橡胶林的地表径流量分别是热带季节雨林和胶农复合系统的33.2倍、2.6倍，热带季雨林、单层橡胶林和胶农复合系统的土壤侵蚀量分别为0.04、11.54、2.73 t ha−1 year−1。土地利用/覆被变化通过改变植被结构和土壤条件影响坡面水土流失，热带雨林转变为单层橡胶林之后，植被条件和土壤性质有不同程度的退化，地表凋落物覆盖减少，这些负面效应加剧坡面水土流失。与单层橡胶林相比，胶农复合系统的植被和土壤条件都得到了不同程度的改善，从而有效地缓解水土流失。仅从控制土壤侵蚀和提高胶园可持续性而言，橡胶林间作一些冠层较低（< 5 m）、凋落物产量较高的多年生经济作物（如：茶树、大叶千斤拔、可可）是十分必要的.（4）单层橡胶林的凋落物组成单一、叶面积小，革质的蜡膜和低孔隙结构特征导致其凋落物的亲水能力较低，季节雨林凋落物的最大持水能力、降雨截留能力和截留率分别是单层橡胶林的1.40倍、1.25倍、1.38倍。胶农复合林的凋落物组成较丰富，其持水能力和降雨截留率均有不同程度的提高（尤其是橡胶/大叶千斤拔系统），潜在降低复合系统的坡面产流量。（5）凋落物年产量表现为热带次生林>人工林>热带季节雨林>橡胶/可可>橡胶/茶叶>橡胶/大叶千斤拔>橡胶/萝芙木>单层橡胶林，凋落物产量的高峰期均出现在雾凉季，降水量和气温对热带季节雨林、热带次生林枯落物产量的影响较明显。季节雨林转变为次生林、人工林后，其枯落物产量、养分归还量均显著升高，但转变为纯橡胶林后则均显著下降，橡胶林间作其他植物后，凋落物产量和现存量明显增加。在退化土地上构建和人工抚育多层多种的次生植物群落或在老龄橡胶林中引进适宜的本土植物，是一种行之有效的可持续利用和管理模式。（6）茶树间作区和橡胶种植区的Ks分别为0.37 cm min−1、0.14 cm min−1，优先流比例分别为49.3%、28.7%。橡胶树和茶树间作通过改善土壤理化性质、促进土壤生物活动（如蚯蚓）、增加凋落物的输入和地表覆被条件，提高了胶茶复合系统中茶树间作区的土壤水分入渗能力和优先流，有效地促进不同土壤层的水分交换和再分配，有利于干旱季节为植物生长发育提供充足的水分供应。当地表径流流经茶树间作区时，水分大量渗入土壤，从而减少坡面产流及土壤侵蚀。 |
| Other Abstract | Unreasonable utilization of water and soil resources by human beings may cause serious soil erosion in the terrestrial ecosystems. Soil erosion is a complex physical and hydrological process that occurs on the earth’s surface with the dispersion of energy and matter. It has been widely concerned by scientists from the fields of ecology, soil science, and hydrology. A large area of tropical rain forest has been transformed into rubber forest in Xishuangbanna region since the 1960s. Rubber plantations with monoculture structure have brought economic benefits for local people, but also led to a series of ecological and environmental problems, such as excessive water and soil loss, land degradation, and water shortage. In order to alleviate these negative environmental effects, the local government and relevant scientific research institutions have established different rubber-based agroforestry systems to search sustainable land use models in recent years. In this study, tropical seasonal rainforest (TSR), tropical anthropogenic forest (TAF), tropical secondary forest (TSF), rubber monoculture (RM), rubber/tea agroforestry (RCS), rubber/F. macrophylla agroforestry (RFM), rubber/R. verticillata agroforestry (RRV), and rubber/cocoa agroforestry (RTC) in the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences were selected as the study sites. Runoff micro-plots and dye tracer experiments were used to measure splash erosion, water and soil losses and its main influencing factors (e.g., vegetation, soil and litterfall characteristics) in different study sites. This study attempted to reveal the effects of land use/cover change on soil erosion in the Xishuangbanna, and to clarify the role of litter layer in the eco-hydrological process of forest ecosystems. Our results are expected to provide important references for the reductions in water loss and soil erosion and the construction of environmentally friendly rubber garden in Xishuangbanna region. The results show: (1) The driptip size of rubber leaves (3.47 mm) was significantly lower than that of TSR tree species (3.78 mm) and intercropping species (4.24–4.54 mm). There was a positive correlation between the driptip size and the development of the leaf tips. The conversion of TSR to RM increased raindrop kinetic energy by 4.8 times under the canopy, which may increase the potential risk of soil splash erosion. After the intercropping of low cash crops in the RM, the raindrop kinetic energy in rubber-based agroforestry systems decreased by 34–75%. In order to alleviate the soil splash erosion, intercropping may be a promising measure for soil and water conservation in rubber plantations. (2) Soil porosity, water holding capacity, infiltration capacity, organic matter content, stand litter, vegetation cover, and leaf area index (LAI) were lower in the RM than in the TSR. The canopy hieght and throughfall kinetic energy were higher in the RM than in the TSR. The splash erosion in the TSR and RM was 3.79 g, 184.29 g, respectively. Favorable soil properties, vegetation traits, and litterfall conditions in rubber-based agroforestry systems decreased the soil splash erosion by 86–97%. In addition, soil splash erosion under the litter removal increased by 2–12 times compared to the retained litter (natural condition). (3) The runoff volume from RM was 33.2- and 2.6- times higher than that of the TSR and rubber-based agroforestry systems, respectively. In general, the sediment yield from the TSR, RM, and agroforestry systems was 0.04, 11.54, and 2.73 t ha−1 year−1, respectively. These trends suggested that the conversion of TSR to RM caused excessive runoff and sediment yield. Compared with the RM, rubber-based agroforestry systems could more effectively reduce water and soil losses. Overall, the sediment yield was significantly negatively correlated with LAI, canopy cover, stand litter, and saturated water capacity, while positively correlated with BD and runoff volume. Solely from the point of erosion control, we recommend that local governments and farmers should consider intercropping perennial cash crops (e.g., F. macrophylla and cacao trees) with low canopy (< 5.00 m) and high litterfall input within RM plantations. (4) The plant litter in the RM was characterized by single composition, small leaf area, leathery wax film and low pore structure. Such litter features led to a low hydrophily. Thus, the water holding capacity and rainfall interception rate of the RM litter were significantly lower than that of TSR litter. Specifically, the maximum water holding capacity and rainfall interception rate of the TSR litter were 1.40 and 1.38 times higher than that of the RM litter. Compared with the RM, the rubber-based agroforesty systems had more diversified litter composition that improved water holding capacity and rainfall interception rate, potentially reducing the runoff and soil erosion. (5) Annual litterfall production followed the order of TSF > TAF > TSR > RTC > RCS > RFM > RRV > RM. The litterfall peak occurred in the fog-cool season (dry season) for all sites. Precipitation and temperature obviously affected the litterfall production of forests with multi-layer and multi-species (e.g., TSR and TSF). The variation trend of stand litter among forest types was similar to that of litterfall production. In general, the litterfall production and related nutrient return increased significantly after the conversion of TSR to TSF and TAF, but decreased significantly after the conversion to RM. The litterfall production and stand litter increased obviously after the intercropping of rubber trees with other cash crops, potentially enhancing the rainfall interception capacity of litter layer in rubber-based agroforestry systems. Establishing a multi-layered community on degraded tropical lands or introducing native species into ageing rubber forests offered a promising way to maintain the sustainable use and management of local forest resources. (6) The Ks of tea planting zone and rubber planting zone was 0.37 cm min−1, 0.14 cm min−1; preferential flow was 49.3%, 28.7%, respectively. Intercropping tea trees in the RM improved soil physical and chemical properties, promoted soil organism activities (e.g., earthworms), increased litterfall input and surface cover, thereby increasing soil water infiltration capacity and preferential flow. Differences in the soil hydraulic properties among different zones could optimize the spatial redistribution of surface and belowground water, increasing water availability for various species with different root systems. This mechanism can not only reduce runoff generation and erosion risk, but also provide adequate water supply for plant growth during the long dry period. Key Words: Water and Soil Losses, Vegetation Cover, Litterfall, Soil Condition, Rubber Planting Pattern |
| Pages | 189 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | https://ir.xtbg.ac.cn/handle/353005/11708 |
| Collection | 西双版纳热带植物园毕业生学位论文 |
| Affiliation | 1.中国科学院大学; 2.中国科学院西双版纳热带植物园 |
| Recommended Citation GB/T 7714 | 朱习爱. 西双版纳土地覆被变化下的水土流失及其主要影响因素[D]. 中国科学院西双版纳热带植物园. 中国科学院大学,2020. |
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