【作者】 李雄华；

【导师】 田大伦；

【作者基本信息】 中南林业科技大学 ， 生态学， 2013， 博士

【摘要】 在当前人类有组织的所有活动中,矿物开采对自然生态系统的影响最为深远。采矿后形成的矿区废弃地,生态系统结构解体,功能严重退化,生态风险与环境威胁突出,需要进行土地复垦和生态系统修复。目前,发达国家矿区生态恢复和土地复垦率平均达到了55%～65%,美、英、澳等矿产大国更达85%。据国土资源部统计,我国矿区土地复垦率已从1988年的2%上升到了2012年的15%左右。但是,矿区复垦速度仍远落后于损毁速度,矿业废弃地以每年3.3万～4.7万hm2的速度递增。我国现有1500个各类矿区占用和损坏的土地估计达200万hm2。加强矿区土地复垦和生态恢复研究与技术推广应用,是生态学研究人员面向社会生产实际的重点工作。本研究以已有近100年开采历史、形成时间已达40余年的湘潭锰矿区废弃地为对象,以森林生态学、景观生态学和恢复生态学为理论依据,通过对矿区废弃地的土壤理化性质、现有定居植物生态特性等进行分析,盆栽试验筛选出能够适应矿区废弃地恶劣条件的地带性乡土树种,在矿区废弃地进行示范造林,通过分析示范基地的林分特征、水土特性和矿物元素生物循环状况,确定了矿区生态恢复的基本技术措施。研究结果表明：(1)湘潭锰矿区废弃地土壤质地以石质粗砂土或砂粉土为主,物理性砂粒(1～0.01mm)在85%以上,物理性粘粒(<0.01mm)在15%以下,土壤调节水、肥、气、热的能力差,可耕性差。限制矿区废弃地土壤肥力的主要因子有：砾石含量、水分状况、有机质含量以及全N含量、全P含量。矿区地下水除pH值和溶解氧低于对照外,主要重金属污染元素和NH4+、NO3-、PO4-3、SiO3-2等离子的含量都超过了对照,有机污染和重金属污染严重。土壤中Mn、Zn、Cu、Fe、Pb、 Ni、Cd和Co的平均含量高,分别是湖南省土壤背景值的179、7、3、6、2、3、3、71倍,以对照区、湖南省土壤背景值、全国土壤重金属元素平均值为标准,矿区废弃地的土壤综合污染指数分别为13.82、75.72和98.05,为重污染等级。矿区废弃地中Cd、Mn潜在生态危害指数分别为2419.75、373.83,矿区重金属综合潜在生态危害指数高达2949.16,都于极强生态风险等级。说明矿区废弃地土壤质量严重下降,重金属Mn、Cd污染严重,是植被恢复的主要限制因子。(2)矿区废弃地经过40余年的自然演替,共有28科53种定居植物,其中草本植物36种,乔木和灌木17种。矿区整个生态系统现正处于向亚热带常绿阔叶林演替的草灌丛初阶段。经盆栽实验,筛选出栾树和杜英两个乡土树种在重金属元素含量高、未改良或仅简单改良的矿区废弃地基质土壤中正常生长,成活率高、长势旺盛,可作为矿区废弃地生态恢复的首选植物。(3)在矿区基质土壤不同处理中(①W1：25%矿区废弃地土壤+75%自然土；②W2：50%矿区废弃地土壤+50%自然土；③W3：75%矿区废弃地土壤+25%自然土；④W4：100%矿区废弃地土壤；⑤对照(CK)为100%自然土),栾树和杜英都生长较好。从夏秋两季各处理中树种的平均地径生长量来说,栾树平均地径增长量大小顺序是W3>W4>CK>W2>W1,可见重金属浓度低时对栾树生长有一定的抑制作用,当浓度增高时则抑制作用可能减弱；杜英平均地径的增长量大小顺序则是CK>W2>W1>W3>W4,可见不同重金属土壤掺和浓度下对杜英生长都有一定的抑制作用,并且随着浓度的增加抑制作用越明显。(4)矿区废弃地生态恢复树种的净光合速率随着土壤对比试验方案(W4、 W3、W2、W1)的不同,表现出不同的差异性。对于栾树而言,各处理的夏季净光合速率(Pn)平均值随矿区废弃地重金属污染土壤掺合量的增加而增加,W3最大,W1最小；秋季各处理的净光合速率(Pn)变化趋势有所改变,随着污染土壤掺和量的增加,只平均值呈先增加再减少再增加趋势,W2最大,W3最小；夏秋两季的只均高于对照。对杜英而言,在夏季,随着矿区废弃地重金属污染土壤掺合量的增加,各处理净光合速率(Pn)平均值先增加后降低,W2最大,W4最小；在秋季,各处理的Pn平均值为W1最大,W4最小；在两个生长季,所有处理的只都低于对照(CK)。试验结果还表明矿区废弃地的重金属元素对栾树的光合作用有一定的促进作用,对杜英的光合作用则有一定的抑制作用。(5)栾树净光合速率(只)与Mg、Fe、Mn、Zn等重金属元素都呈正相关关系,与叶片N、P、K(全量)、叶绿素含量则呈负相关关系,其中N、Mn、Zn元素含量及叶绿素含量和净光合速率(Pn)的相关性达到了显著水平。杜英的净光合速率(Pn)与P、K、Zn含量都呈正相关关系,与N、Mg、Fe、Mn、叶绿素含量则呈现负相关关系,净光合速率与所有矿质元素的相关关系都没达显著水平。(6)在矿区废弃地选取0.67hm2的示范基地,按2行栾树、1行杜英进行生态恢复营林试验,共种植栾树1440株,杜英720株。在矿区废弃地极端的生境条件下,栾树、杜英混交林幼龄阶段一年内生物量可增加1192.48kg/hm2,表现出适应性强,生产潜力大的特征,可作为矿区废弃地生态修复的适宜方案。并且,重金属元素主要积累在树枝、树叶和根部(仅树叶积累量就占70.7%),生物量大、主要被利用的树干积累重金属元素最少(仅占4.45%),可以避免重金属元素因木材利用而再次大量地向环境中扩散,有利于生态恢复区域的林业生产。(7)对林分生长的环境状况、林分的矿质元素含量分布及生物循环特征进行分析,结果表明,林分自身对元素的利用率高,归还量多,周转期短,有利于林地生产力维持。植被恢复5年后,矿区废弃地土壤有机质和营养元素含量增加,含水量增加,土壤碱性减弱。示范基地中杜英根际土、栾树根际土、林内非根际土的有机质含量分别为106.793g/kg、45.50g/kg、37.875g/kg,都要高于林外对照土壤的18.86g/kg,主要重污染元素Mn、Ni、Cd、Zn等的下降幅度达到70%以上,Cu的下降幅度也有40%,说明生态恢复对土壤的化学性质及重金属元素有着明显的改善作用。经过植物修复后的矿区废弃地,土壤营养条件和生态环境得到了改善,基本实现了对矿区废弃地进行生态恢复的研究与示范目的。更多还原

【Abstract】 Mining is the most profound human activities impacted on the natural ecological system now. There are large of lands been wasted by the mining. In these mining wasted land, ecological risks and environmental stresses are very prominent while the structure of ecosystem dissolved and the function degenerated. Land reclamation and ecosystem restoration of the wasteland educed by the mining have become an important and interest issue because the wasteland not only occupied the vast tillable lands but also caused serious environment pollution. After nearly a century of research and technology applications, the proportion of mining land reclamation has reached an average of55%to65%; meanwhile, it has reached85%in the United States, Britain, Australia and other mining giants. According to the ministry of land and resources statistics, the proportion of the mining area land reclamation in China has increased from2%in1988to around15%in2012. But now the mine land increases at an annual rate of33000to47000hm2for the mine reclamation speed far behind the damage in China. At a conservative estimate, there are1500mining areas have occupied or damaged land of2million hm2.The object of this study was the wasteland educed for more than40years in Xiangtan manganese mine which had mined for100years. The basic technical measures had determined for the mining area ecological restoration based on the forest ecology, landscape ecology and restoration ecology. Two native tree species was selected by pot experiment after analyzing the soil physical and chemical properties, the characteristics of settle existing plants, which photosynthetic characteristics had been analyzed. The forest conditions, soil characteristics and mineral biological cycle of the demonstration forest base in the mining wasteland had been analyzed. The result showed that:1. The soil texture of the wasteland is mainly coarse sandy or silt. The proportion of physical sand (1-0.01mm) in the soil is over85%, and physical clay (<0.01mm) is below15%. The total soil fertility index is lower in the wasteland than in the Chinese fir forestland. It is found that the main factors limiting soil fertility in the wasteland were percentage of sandy grain(1～0.01mm), soil organic matter content, soil concentrations of N and P. The groundwater in mining area is polluted seriously which high levels of in heavy metal and NH4+, NO3-, PO4-3, SiO2, addition to the pH value and dissolved oxygen is lower than the contrast. The concentration of Mn(52924.0mg/kg), Zn(396.70mg/kg), Cu(42.30mg/kg), Fe(29782.0mg/kg), Pb(354.10mg/kg), Cd(4.37mg/kg) and Ni(40.30mg/kg) in the wasteland are179,7,3,6,2,3,3and71times of those in the Hu’nan province land, respectively. In comparison with the mean values of soil heavy metal elements recorded in the control site, Hu’nan province and national level, the syntheses pollution indexes of the six6heavy metal elements(Mn, Cu, Pb, Zn, Cd and Ni) in the wasteland are13.82,75.72and98.05, respectively, which all exceeded the heave pollution standard. The potential ecological risk index of Mn, and Cd are2419.75and373.83respectively that indicate the environmental risk are at the highest level, as so as the heavy metal potential ecological comprehensive risk. On the individual element basis, the elements on Mn and Cd exceeded heave pollution standard. It is indicated that mining of Manganese result in serious environment pollution and tillable land degradation.2. There are53species settled in the mining area after40years of natural succession. They are belonging to28families with herbs36species,17kinds of trees and shrubs. It is indicated that the current local communities are dominated by perennial shrub and grass, which are at the primary stage of succession towards subtropical evergreen broadleaved forest. It is a must that ecological restoration needs to give preference to these native tree species which have certain resistance, fast growth, and high economic value and ecological benefits, through the analysis of the characteristics of settle existing plants. The plotted plant test results show that Koelreuteria paniculata Laxm is the preferred plant for the ecological restoration in the slag wasteland, which grows and adapts strongly in the slag wasteland.3. By using the slag wasteland soil in Xiangtan Manganese Mine, five different mixed soil treatments by which potted plant tests are conducted, five treatments are as follows:CK:100%untreated soil; W1:25%slag wasteland soil+75%untreated soil; W2:50%slag wasteland soil+50%untreated soil; W3:75%slag wasteland soil+25%untreated soil; W4:100%slag wasteland soil. Survival rate and height growth rate of Koelreuteria paniculata Laxm are lower than those of Elaeocarpus decipens. height growth rate of Koelreuteria paniculata Laxm each treatment (exceptW3) is higher than that in fall; the average diameter growth in order is W3>W4>CK>W2> W1,W1and W2are less than the contrast, while W3and W4are larger than the contrast. It means that low concentration inhibits diameter growth, while high concentration promotes it. Elaeocarpus decipens grow fast and well, height growth rate in summer is far higher than that in autumn. The average diameter growth in order is CK> W2> W1> W3> W4, all are lower than the contrast, heavy metal treatments in the soil inhibits diameter growth, and with the increase in the concentration of heavy metal, the inhibitory effect gets more obvious.4. Focused on net photo synthetic rate (Pn) of the two species in Summer and Autumn, the results showed that the average net photosynthetic rate (Pn) of both two species in summer are higher than in fall, and the relationship among all treatments (W1、W2、W3、W4) of the average net photosynthetic rate (Pn) has changed in autumn. For Koelreuteria paniculata Laxm, the average value of (Pn) of W3is the largest, W1is the minimum, While in autumn, the average value of (Pn) of W2is the largest, W3is the minimum. For Elaeocarpus decipens, the average value of (Pn) of W2is the maximum, while W4is the minimum in Summer; the average value of (Pn) of W1is the largest,while W4is the minimum in Autumn.5. For Koelreuteria paniculata Laxm Relevances among Pn and heavy metals Mn、Cu、Zn、Pb、Ni、Co、Cd contents in soil all fail to meet the significant level, while Relevances among Pn and Pb、Cd contents in soil reach negative significant level of Elaeocarpus decipens. Relevances among Pn and N、Chlorophyll content in leaves reach significant negative level,while Pn among Zn and Mn contents in leaves of Koelreuteria paniculata Laxm reach positive significant level; For Elaeocarpus decipens, among Pn and N、P、K、Mg、Ca、Fe、Mn、Zn and Chlorophyll in leaves all fail to meet the significant level.6. In the selection of0.67ha demonstration base in the mining wasteland, there are planted by1440Koelreuteria paniculata Laxm and720Elaeocarpus decipens while press2line Koelreuteria paniculata Laxm,1line Elaeocarpus decipens for the ecological restoration experiment. The stand biomass increased by1192.48kg/hm2in a year. Under the extreme habitat condition of mufu, Koelreuteria paniculata Laxm and Elaeocarpus decipens have preliminarily showed strong adaptability, high patience, and great production potential. It is indicated the mixed forest is appropriate, that can be used as a restoration mean in mining area to improve ecological environment. Main heavy metals are accumulated in the branches, leaves (the accumulation of leaves alone accounts for70.7%), and roots, the accumulation of heavy metals (only4.45%) in the mainly used trunk is very lower. It is very outstanding to avoid heavy metal spread in the environment for using timber and conducive to forestry production in the ecological restoration area.7. Of stand growth environmental conditions, the mineral elements content of forest distribution and biological cycle characteristics are analyzed, and the results show that the forest has high utilization of elements, the return amount is much, cycle time is short. It is conducive to maintaining forest productivity. Five years after ecological restoration, soil organic matter, nutrient element content and moisture content are increases, with soil alkaline weakening. The organic matter in rhizosphere soil of Koelreuteria paniculata Laxm and Elaeocarpus decipens reach106.793g/kg and45.50g/kg, respectively. Those of non-rhizosphere soil in the stand reach37.875g/kg. They are more than18.86g/kg of controlled soil out of the stand. Contents of main polluting element as Mn, Ni, Cd, decline of70%or more, and those of Cu decreased40%. It is concluded that ecological restoration has obviously improved the soil chemical properties and decline heavy metal contents. In the restoration area, soil nutrient condition and ecological environment has improved, basically achieved the mining wasteland ecological restoration research and demonstration purposes.更多还原