【作者】 张建彪；

【导师】 孟紫强；

【作者基本信息】 山西大学 ， 环境科学， 2011， 博士

【摘要】 目前,煤炭开采已经导致一系列的生态环境问题,如矿区土壤和植被遭到毁坏、生物多样性减少或丧失、土地生产力下降、整个生态系统的功能退化等。严重恶化的生态环境已成为制约矿区经济社会可持续发展的根本性问题。煤矿区的生态恢复和重建,对于改善矿区土壤状况,提高植被覆盖率,实现矿区生态环境的根本好转具有至关重要的意义。古交煤矿是山西省煤矸石山区生态重建的示范区。本研究地古交煤矿煤矸石山的生态重建主要包括3种模式：人工种植外来种火炬树、人工种植乡土种侧柏和自然恢复模式。分别对不同植被重建模式的群落结构、群落动态、物种多样性和土壤状况的变化规律进行分析讨论,并运用TWINSPAN、CCA等数量生态学方法分析植被梯度变化规律及其与土壤等环境因子之间的关系,阐述了影响矿区植被恢复的限制性因素。为了评价这3种模式的恢复效果,选取相邻土山的天然地带性原生群落进行了对比分析。在此基础上提出植被恢复与重建的合理模式,旨在为重建煤矸石山区结构合理、功能完善的人工生态系统提供思路和参考。在人工火炬树群落12年的恢复演替过程中,群落的层片结构、盖度及林下优势种随恢复时间均发生了明显变化。初始群落优势种以耐干旱贫瘠的先锋植物如猪毛蒿、狗尾草为主,而5年后群落向中生性植物占绝对优势的方向发展,并且形成乔、灌、草的3层结构。此后随着火炬树的萌蘖繁殖,群落郁闭度明显增加,林下光照减弱,林下植物迅速减少以至大量消失。本研究表明,火炬树具有极强的根孽繁殖扩散能力,可以迅速在群落中取得优势地位,并抑制和排斥其它物种。在演替12年后,火炬树形成几乎独占的立地,群落物种多样性急剧减少。本研究表明,光照也是影响火炬树群落演替的重要因子。火炬树是阳性先锋树种,群落内的光照不仅影响草本植物的定居存活,也影响火炬树克隆子株的萌发和分布。随着火炬树群落郁闭度增加,林下光照减少使火炬树幼苗难以萌发。所以在演替后期,火炬树的克隆子株数量大幅减少,从而影响林分演替,无法实现群落的自我更新。可见处于成熟阶段的火炬树单优种群落,是不稳定的。本研究表明,火炬树能扩散进入附近的侧柏林和达乌里胡枝子一白羊草群落,并在这些群落里迅速扩大种群和占据优势,未来很可能成为这些群落的优势种,在一定程度上抑制侧柏和灌木的生长,说明火炬树具有一定的入侵性。总体来说,本研究的人工侧柏林生长缓慢,群落的高度盖度呈现逐渐增加的趋势。TWINSPAN分类及植被演替分析表明,侧柏林群落经过14年的恢复,群落从一年生先锋植物占优势的初始阶段过渡到以白羊草和硬质早熟禾为建群种的后期演替阶段,并出现了多年生灌木。随着恢复时间的延长,侧柏群落的物种多样性呈现缓慢增加的趋势。覆土厚度是影响侧柏生长演替的重要因素。3种覆土条件下,侧柏的树高、地径、冠幅、叶片长势和林相等指标均有显著差异。当覆土厚度小于30 cm时,侧柏出现叶子干枯甚至脱落现象,枯死率高。本研究表明,煤矸石山的植被经过25年的自然恢复演替,群落从耐贫瘠的藜科和禾本科杂草逐渐向中生、中旱生植物占绝对优势的方向发展,群落生境趋于中生化。通过TWINSPAN分类及植被演替趋势分析,煤矸石山的植被在自然恢复状态下大致经历了猪毛菜、猪毛蒿、铁杆蒿、硬质早熟禾、白羊草和达乌里胡枝子6个发展阶段,优势种群的数量和种类发生了很大变化,物种多样性呈现逐渐增加的趋势。说明矿区退化生态系统可以通过自然恢复增加植被盖度和物种多样性,但这个过程比较漫长,且群落结构并不完善。总的来说,3种植被恢复模式都可以增加土壤有机质、全N、有效P和速效K的含量,减小土壤容重和pH值,对煤矸石山的土壤有一定的改良作用,尤其是侧柏的改良效果更明显。但即使在演替后期,3种恢复模式的土壤养分含量仍处于较低水平,这说明植被对土壤的改良作用十分有限。相关分析及CCA排序分析表明,土壤因子是影响群落物种多样性变化的主要环境因子,也是煤矸石山植被恢复演替的主要限制性因素。因此在煤矸石山区开展植被恢复与重建时,增加土壤养分含量,改善土壤理化性质至关重要。与相邻土山上的天然次生植物群落相比,矸石山3种植被恢复模式下群落的结构、物种组成、高度和盖度都存在显著差异。4种群落类型中,Margalef指数和Shannon-Wiener指数表现为：原生群落>自然恢复群落>侧柏群落>火炬树群落。这是由于原生群落已经处于比较高级的稳定发展阶段,所以多样性指数最高。Pielou均匀度指数表现为：自然恢复群落>原生群落>侧柏群落>火炬树群落。3种恢复模式下群落的土壤养分含量和土壤有机碳储量均显著低于原生群落,而土壤容重和pH值则显著高于原生群落。整体来讲,恢复后的植被与天然次生植被存在较大差异,改善土壤理化性质是促进植被恢复演替的有效途径。本研究表明,自然恢复的植物群落物种多样性较高,因此从理论上讲自然恢复是该区植被恢复的理想途径之一。但自然恢复速度缓慢,在短期内难以形成乔灌草的复合生态系统,不能从根本上改善生态环境。因此,人工引入乔灌树种,丰富群落层次结构,优化群落生态功能,加快退化生态系统的演替进程,无疑是十分必要的。从短期来看,矿区矸石山栽植的火炬树,生长速度快,能很快达到增加植被覆盖度的目的,5年左右群落盖度即可达到80%。但从长期来看,随火炬树林的成熟郁闭,火炬树会严重抑制其它物种的生存,林下的物种多样性呈现急剧减少和火炬树自身幼苗难以萌生的现象,在一定程度上增加了因生态胁迫而使群落退化或死亡的潜在风险。可见,演替后期的火炬树单优种群落不能发展成为一个稳定的顶级群落。所以应该把群落的盖度、物种多样性和群落演替趋势结合起来,作为植被恢复成功与否的主要指标。由此可知,在煤矸石山的植被恢复重建中,应该谨慎营造火炬树林。侧柏在覆土达一定厚度时,生长良好。所以,在煤矸石山区生态重建的实践中,应以人工种植侧柏等本土植物为主、自然恢复为辅的模式开展植被恢复。在植被恢复重建中,不仅要增加植被盖度,合理搭配乔灌草物种,恢复生物多样性,而且更要注重土壤生态功能的恢复。应该使重建生态系统的各个组分之间相互促进,构成一个有机整体,才能恢复和增强生态系统的自我调节和自我维持能力。总之,煤矸石山区的植被恢复重建是一个艰难而漫长的过程。应在尊重退化生态系统自然恢复能力的基础上,人工引入适宜的乔灌树种。根据植被演替及其与土壤等环境因子的相互作用规律,采取适当的人工措施改善土壤理化性质,促进植被的进展演替,完善生态系统的结构和功能,这是煤矸石山区退化生态系统恢复与重建的根本途径。更多还原

【Abstract】 The exploitation of coal mine has caused severe damages to the ecological environment, such as destroying farmlands and vegetation, decreasing species diversity and land productivity, and eventually destroying the structure and function of local ecosystems. The degenerated environment has put forward great challenges for sustainable economic development. Consequently, ecological reconstruction, aim at increase plant coverage and soil nutrients in coal mine area, is of great significance for improvement of local environments.Gujiao coal mine is a example of ecological reconstruction in Shanxi province, where has rich mineral resources.There were three methods used in ecological reconstruction in Gujiao coal-gangue area, including artificial restoration by planting staghorn sumac (Rhus typhina) and oriental arborvitae (Platycladus orientalis), and natural restoration. Based on the survey of vegetation and soil properties, the changes of community structure and species diversity throughtout the succession process were analyzed. Also, the interactions between vegetation succession and soil conditions were discussed using TWINSPAN classification and CCA ordination methods. In order to evaluate the results of ecological restoration, three restoration methods were compared with the regional vegetation. Further, some suggestions are put forward, which can provide a scientific basis for ecological reconstruction in the mining area.The results showed that great changes occurred in community structure, species composition and diversity, coverage after 12 years of succession of staghorn sumac. Pioneer species such as Salsola collina and Setaria viridis played dominant roles at the early stage of succession, and they were replaced by dominant species Poa sphondylodes after 5 years. Because of the fast growth rate, canopy coverage of staghorn sumac community increased quickly. In the meantime, light radiation on the forest floor evidently decreased, leading to the decrease of species number and diversity in the herb layer. Due to its vigorous sprouting reproduction, staghorn sumac could colonize the new habitat and expanded the population within a short time. After 12 years, staghorn sumac became an exclusive edificator in the community and other species were greatly depressed and disappeared.Our study showed that light intensity was an important factor affecting species diversity and succession of staghorn sumac community. At the mature stage, weak light under the community canopy restricted the sprouting and dispersion of clonal ramet of staghorn sumac, as well as the growth of herb species. Thus, as a heliophytes species, the succession process and self-renewal of staghorn sumac was impeded to a great extent. Also, staghorn sumac was able to disperse into adjacent oriental arborvitae and shrub community and quickly expanded its population. The average height of clonal ramet of staghorn sumac was higher than that of oriental arborvitae and shrub. So, it was likely that the growth of oriental arborvitae and shrub would be depressed by staghorn sumac invasion in the future.It was showed that oriental arborvitae displayed a slower growth rate, with the height and coverage increasing gradually. Based on the results of TWINSPAN, annual pioneer species such as Salsola collina and Setaria viridis firstly occurred at the beginning stage of succession, then other dominant species such as Artemisia giraldii, Artemisia vestita and Poa sphondylodes appeared in turn through the oriental arborvitae succession. After 14 years, kinds of shrub appeared in the community. Species diversity in oriental arborvitae community was also increased during the whole succession. The thickness of soil added on the coal waste piles was a main factor affecting the growth of oriental arborvitae. There were significant differences in tree height, basal diameter and canopy coverage of oriental arborvitae among three soil types. When the thickness of soil was lower than 30 cm, some leaves growed sere and falled off, leading to higher mortality in oriental arborvitae community.Based on the results of TWINSPAN, species composition and diversity in the naturally restored communities experienced great changes during the succession period, with the dominant species changing from annual to perennial and from low-class to high-class. The dominant species such as Salsola collina, Salsola collina, Artemisia sacrorum, Poa sphondyl odes, Bothriochloa ischaemun and Lespedeza bicolor occurred in turn, and made up a complete succession series. After 25 years, shrub like Lespedeza bicolor played a dominant role in the naturally restored communities. It took a longer time for the naturally restored vegetation to develop to an advanced and steady state, and the restoration rate was much slower.Soil organic matter, total N content, available P content were all improved under three restoration modes, while soil bulk density and pH value were decreased. Therefore, soil conditions could be improved by three restoration methods. However, the improvement was very limited because soil fertility at the end of the succession were at a lower level according to the soil fertility classification standards of the second national soil survey in 1980s. The analysis of correlation and CCA ordination suggested that soil conditions were main factors influencing the change of species diversity and vegetation succession. Therefore, it is necessary to improve soil condition in ecological reconstruction in Gujiao coal-gangue area.There were significant differences in community structure, species composition and diversity, coverage among regional vegetation type and restored vegetation types in the coal-gangue piles area. Margalef and Shannon-Wiener indexes of four vegetation types decreased in the order: regional vegetation> naturally restored vegetation> oriental arborvitae plantations> staghorn sumac plantations. The highest Margalef and Shannon-Wiener indexes occurred in the regional vegetation type, which could be attributed to that regional vegetation was at the advanced stage after longer succession. Pielou index decreased in the order:naturally restored vegetation> regional vegetation> oriental arborvitae plantations> staghorn sumac plantations. This was because that environmental factors distributed evenly in naturally restored vegetation due to a lack of tree stratum. Soil nutrient and soil carbon stock of three restored vegetation was significantly lower than that of regional vegetation, while soil bulk density and pH value were significantly higher than that of regional vegetation. So improving soil properties will be helpful for vegetation restoration in coal-gangue area.Among three restoration modes, species diversity index was highest in naturally restored vegetation, which can imply that natural restoration is likely an ideal way in coal mining area. However, it was difficult for natural restored communities to develop to an advanced stage within a short time. So the natural restoration method is inefficient to improve environment quality. Therefore, it is necessary to introduce tree species in ecological reconstruction in coal coal-gangue area to improve community structure and function, and eventually to accelerate the vegetation succession.In the short term, the planting of staghorn sumac could increase vegetation coverage quickly, and community could reach to a coverage of 80% after 5 years. However, in the long term, staghorn sumac depressed not only other species but also its sprouts at the mature stage, which could bring great risks of degradation to the plant community when there existed a ecological stress. Staghorn sumac community could not develop to the climax stage. So the community coverage, species diversity, soil conditions and succession tendency should be regarded as main indexes in reconstruction evaluations.Therefore, caution should be taken when planting staghorn sumac to a large extention in ecological reconstruction in coal-gangue area. Whereas, planting indigenous species such as oriental arborvitae, combined with natural restoration, would be a better choice for vegetation restoration in coal-gangue piles. In the restoration processes, enriching the community structure, increasing species diversity and vegetation coverage are all needed. Furthermore, the improvement of soil condition is also important to accelerate the vegetation succession. Because soil conditions are main limiting factors for vegetation restoration, and the interactions between these main ecologlcal components ensure the self-maintenance of the ecosystems.In sum, there is a long way to achieve the purposes of ecological reconstruction in coal-gangue area. Based on the self-restoration of ecosystem, introducing suitable tree species and improving soil condition properly are absolute needed for ecological reconstruction in coal-gangue area. According to the principle of the interactions between vegetation succession and soil properties, accelerating progressive succession of vegetation and improving the structure and function of the ecosystem are the main approaches of ecological restoration and reconstruction in coal-gangue areas.更多还原