【作者】 张文军；

【导师】 周心澄；

【作者基本信息】 北京林业大学 ， 生态环境工程， 2008， 博士

【摘要】 我国是世界上土地沙化危害最严重的国家之一。随着防沙治沙工程的实施，在治理和改善沙区生态环境的同时，形成了大规模的人工植被，也培育了大量的沙区生物质资源。近年来，人工植被出现了大面积退化和死亡的现象，直接影响着人工植被效益的持续发挥。因此，加强人工植被的管理与利用已成为今后一个时期需要解决的重大问题。为此，本研究以目前在科尔沁沙地广泛应用的活沙障治理流动沙丘形成的人工植被为研究对象，以现代植被生态学和恢复生态学理论为指导，采用野外调查和室内分析相结合的手段，对其植被和土壤的恢复效应进行了全面的研究，旨在全面掌握其动态规律和恢复效应，为活沙障技术的进一步应用以及制定科学的活沙障植被管理与利用措施提供理论依据。得出如下结论：(1)在流动沙丘上建植黄柳(Salix gordejevi)+羊柴(Hedysarum fruticosum)的网格(4×4m)式植物活沙障，能够收到良好的植被恢复效果。形成的沙障群落3a时间植被盖度就可达到24．7％，沙丘处于半固定状态；4a～7a的植被盖度可达到40％～70％，沙丘处于固定状态；3a～7a群落的植物种达到6～10种，生物量(鲜重)达到221．6～531．1kg／m~2；5a～7a群落的地表凋落物盖度达到了26％～49％，现存生物量达到了105．9～340．9g／m~2。(2)沙障群落在发育初期(4a前)，物种单调，结构简单，由建植沙障时人工引入群落的黄柳和羊柴垂直混交构成了群落的网格式水平结构，障间植物分布极少。随着群落的演替，在4a～5a群落中由于羊柴更新苗的出现和草本植物的入侵，障间小群落迅速发育，群落具有多种层片和多层垂直结构，并由网格状水平结构向沙障网格与“障间小群落”交互均衡分布的水平结构演变，植被得到了全面的恢复。黄柳和羊柴在群落中始终发挥着主导的作用，障间小群落的发育形成，导致群落结构质的变化。灌木层片、半灌木层片和“半灌木更新层片”(主要物种)位于沙障群落中不同的水平空间上，其盖度和生物量在水平空间上重叠较少，任何一方的波动对群落的结构、稳定性及其功能和效益的发挥都具有重要的影响。(3)4a～5a群落的物种组成及群落结构变化剧烈，同时也出现了大量的立枯生物量，半灌木层片(羊柴)的盖度和生物量也大幅下降，群落开始进入衰退阶段。表明群落一方面向着物种多样性和结构复杂化的方向演替，另一方面群落处于不稳定的发育阶段。(4)沙障群落土壤种子库也得到了初步的恢复，3a～7a群落的土壤种子库物种数量为3～6种，以禾本科和菊科的一、二年生植物为主；种子密度为33～694粒／m~2，土壤种子库与地上植被之间存在着中等程度的相似性，7a群落土壤种子库的物种数和种子密度的水平低于科尔沁沙地半固定沙丘土壤种子库的水平。(5)沙障群落根系生物量迅速恢复，3a～7a群落根系生物量达到49．31～230．88g／m~2；根系生物量结构中，细根比普遍较高，为0．5394～0．8145，反映出根系生长比较旺盛，土壤的环境条件相对适宜；细根比的垂直分布总体上呈浅层化的趋势，有利于对沙区有限降水资源的利用。不同层片植物根系的水平和垂直分布空间不同，并具有良好的互补性，有利于土壤养分资源的有效利用和保持群落的稳定性。(6)随着沙障群落的发育演替，土壤理化性状也得到了逐步的改善，表现为土壤表层(0～5cm)物理性黏粒含量的增加，0～50cm土层容重增加，总孔隙度降低，非毛管孔隙度升高，速效氮、速效磷和有机质含量增加等。(7)随着沙障群落的进展演替，土壤向着旱化的方向发展。调查期间对照的土壤含水率为3．19％，3a～7a群落含水率逐渐下降，至7a群落下降为1．9％，下降了40．44％。(8)本研究的结果表明，建植活沙障时在物种选择上要注重适应性强、造林成活率高、生长稳定的物种，并将其配置在沿沙丘等高线(垂直主风方向)上。在建植黄柳+羊柴网格式活沙障时，应当将黄柳布设在沿沙丘等高线(垂直主风方向)上。(9)按照群落结构变化和生态恢复机制制定科学的人工群落经营管理措施，对于维持群落的稳定性及其效益的持续发挥具有重要的意义。更多还原

【Abstract】 China is one of the countries suffering the most serious damage caused by land desertification in the world. Along with the implementation of sand prevention and control project, large area of artificial vegetation and large amount of biomass resources are cultivated at the same time of controlling and improving ecological environment in the sandy area. In recent years, degradation and death of large area of vegetation has exerted direct impact to the sustainable effect of the artificial vegetation. Therefore, enhancing management and utilization of artificial vegetation has become a critical issue that needs to be addressed within a period in the future. Aiming at the artificial vegetation cultivated in controlling shifting sand dunes with living sand barriers widely applied in Horqin sandy land, guided by the modern vegetation ecology and restoration ecology and adopting the means of combining field investigation and indoor analysis, we conduct this comprehensive study on the effect of vegetation and soil restoration so as to master comprehensively its dynamic law and restoration effect, providing theoretic basis for establishing scientific measures for vegetation management and utilization. The conclusion is as follows:(1) Checkerboard-like (4 x 4m) living plant sand-barriers with Salix gordejevii and Hedysarum fruticosum on shifting sand dunes can play effective role in vegetation restoration. The vegetation of the sand barrier communities would reach 24.7% within 3 years and the sand dunes would be semi-fixed. In the period from the 4th to 7th year, the coverage would reach 40%～70% and the sand dunes would be fixed. In the period from the 3rd to 7th year, the species of plant in the communities would reach 6～10 and the biomass (fresh weight) would reach 221.6～531.1kg/m~2. In the period from the 5th to 7th year, the surface litter coverage would reach 26%-49% and the stock biomass would have reached cover 105.9～340.9g/m~2.(2) In primary growth period (before 4a) of the sand barrier communities, the species is monotonous and structure simple. The checkerboard-like horizontal structure of the communities is formed by mixing vertically the Salix gordejevii and Hedysarum fruticosum introduced artificially into the communities when the sand barriers are established, there is almost not vegetation between the barriers. Along with the succession of communities and the invasion of seedlings of Hedysarum fruticosum and herbage plants in the period from the 4th to 5th year of the communities, small communities among barriers grow rapidly, forming vertical structure with multiple synusias and multiple layers, and changing from the checkerboard-like horizontal structure to the uniformly distributed horizontal structure mixed with barrier checkerboard and small communities among barriers. Then, the vegetation would be comprehensively restores.Salix gordejevii and Hedysarum fruticosum always play the leading roles in the communities. The generation and growth of small communities among barriers results in a qualitative change of the communities. Shrubbery synusia, subshrub synusia and subshrub regeneration synusia (major species) are located in different horizontal spaces in the barrier communities. There is less horizontal overlap of the coverage and biomass. Fluctuation of any party would exert significant impact to the structure, stability, function and effect of the communities.(3) The species composition and structure of the communities in the period of 4a～5a would change acutely. At the same time, large amount of standing dead biomass would appear and the coverage and biomass of Hedysarum fruticosum coverage in subshrub synusia would drop in large degree. Now, the communities are coming into the phase of decline, showing that the communities are coming into succession to the direction of species diversity and structure complication and in the unsteady development phase.(4) The soil seed band of the sand-barrier communities is also restored primarily. The number of species in the soil sand bank of the 3～7 years old communities is 3 to 6, mainly composed of one or two-annual Echinochloa crusgalli and Flos chrysanthemi. The seed density is 33～694 grains/m~2. There is a moderate comparability between soil seed bank and ground vegetation. The number of species and seed density of the soil seed bank in 7-year communities is lower than that of the semi-fixed sand dunes in Keerqin sandy land.(5) The root biomass of sand barrier communities is restored quickly. The root biomass of the 2～7-year communities reaches 49.31～230.88g/m~2. In the structure of the root biomass, specific root ratio is universally higher, 0.5394～0.8145, reflecting that the root growth is in comparative bloom and the environmental condition of the soil is comparatively comfortable. The vertical distribution of the specific roots shows a trend of shallowness at large, which is beneficial to the utilization of precipitation resource in the sand area. The plant root systems in different synusias are different in vertical and horizontal distribution spaces, well complementing each other, beneficial to utilize of soil nutrient resources effectively and keep communities stable.(6) Along with the development and succession of the sand barrier communities, the physical and chemical properties of the soil also improve gradually. The physical particle content of surface soil layer (0～5cm) has increased, the 0～50 soil bulk density increased, the total soil porosity dropped, the Non-Capillary Porosity raised and the available nitrogen, Phosphorus and organic content increased(7) Along with the development and succession of the sand barrier communities, soil is taking the trend of desiccation. In the investigation, the water content of the compared soil was 3.19%, while the water content of the 7a communities dropped to 1.9%, 40.44% lower.(8) As a result of this paper, the species that have the characteristic of good adaptability, higher survive rate and steady growth should be selected and plant them on the contour line of sand dune. When the Checkerboard-like living plant sand-barriers with Salix gordejevii and Hedysarum fruticosum to be set up, Salix gordejevi shoud be plant on the contour line of sand dune.(9) Designating scientific measures for community management according the change of community structure and the mechanism of ecological restoration is of significance for keep stability of the artificial communities and maintain sustainable development of their effect.更多还原