【作者】 李生；

【导师】 张守攻；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2008， 博士

【摘要】 喀斯特地貌在世界广泛分布,中国西南地区是喀斯特典型地区之一。由于脆弱的自然背景叠加了不合理的人为因素,导致土地石漠化。中国现有石漠化面积达12.96万km2,严重影响了区域生态环境与经济的可持续发展,迫切需要开展石漠化的生态治理工作。恢复地上植被是石漠化治理的有效措施,但是在开展人工造林恢复植被过程中,由于未能很好地掌握石漠化生态系统的环境特征与恢复物种的生物学特性,导致造林过程中造林成活率低,植被恢复速度与质量差,石漠化生态治理的效果不显著。本研究在石漠化典型地区广西自治区凌云县,通过野外调查和定位观测对石漠化生态系统的主要生态因子进行了调查分析,研究不同演替阶段植被组成与多样性动态变化规律、不同植被类型对环境小气候、土壤质量及水土流失的影响,分析石漠化植被恢复的限制性因子与植被的环境效应;采用室内模拟土壤水分试验,针对主要造林树种的种子与幼苗分析了水分对其生长及生理生化产生的影响,有助于掌握石漠化生态系统生态环境变化规律,明确土壤水分对造林树种的影响,为石漠化地区植被恢复物种选择与植被恢复提供参考。研究结果如下:1、喀斯特石漠化地区植被自然恢复过程可分成草丛阶段、草灌阶段、藤刺灌丛阶段、次生乔林阶段和顶级群落阶段。以空间代替时间选取典型样地,分析了各阶段群落的物种组成,应用物种丰富度、Simpson指数、Shannon指数和Pielou均匀度指数分别研究各演替阶段草本层、灌木层、乔木层和群落总体的物种多样性。结果表明,石漠化地区,植被种类单一,多样性下降,植被以草本为主。在植被演替过程中,除草本层外,各生活型物种丰富度从草丛阶段开始增加,到次生乔林阶段达到峰值。草本层物种丰富度和Shannon指数略有波动,Simpson指数和均匀度都逐渐下降,到顶级群落阶段达到最低;灌木层、乔木层和群落总体各测度指数均表现为先增加后下降的趋势,但各测度指数达到峰值的阶段不同。草丛阶段物种多样性为草本层大于灌木层;进入草灌阶段以后,灌木层多样性上升并逐渐超过草本层;当乔木出现后,乔木层多样性最低。植物多样性能增加生态系统恢复力,促进生态系统稳定性,植被恢复工作中应丰富造林物种,增加物种多样性。2、通过对5种不同植被类型样地环境的光照强度、空气温度、空气相对湿度、土壤温度、-5cm土壤含水量等5个小气候因子的观测研究,结果表明,不同植被类型地上植被的组成、覆盖度和高度不同,改变了样地的环境小气候。对小气候的改善作用整体表现为林地>灌林地>草地>农耕地>石漠化裸地。石漠化裸地光照强度强,空气温度高和土壤温度高,空气湿度和土壤含水量低,且变动幅度大,样地环境趋向于干热化演替;与石漠化裸地相比,林地、灌林地、草地、农地内的光照强度分别下降了96.4%、52.0%、17.0%、44.2%,空气温度分别下降了30.1%、20.2%、12.7%、17.8%,空气相对湿度分别提高了129.2%、57.2%、18.0%、41.2%,土壤温度分别下降了11.5%、8%、2.5%、5.5%,土壤含水量分别提高了42.6%、33.2%、15.7%、14.0%,且各因子变动幅度趋缓,样地环境趋向于凉湿化演替。3、针对农田、退耕台地、退耕坡地、草地、灌木林地、针叶林地、阔叶林地等7种不同植被类型的土壤理化性质进行调查分析,结果表明,不同利用方式样地总体间土壤容重、土壤含水量、总孔隙度、毛管孔隙度、非毛管孔隙度存在极显著的差异(p<0.01),样地总体间的变异系数分别为12.37%、29.72%、18.07%、12.66%、84.70%。有机质、全氮、全磷、全钾、速效氮、速效磷、速效钾及交换性Ca2+含量总体间差异达到极显著。土壤容重与土壤其它指标间呈负相关,土壤有机质与其他化学指标存在着较高的正相关。运用相对退化指数方法对不同利用方式条件下的土壤的定量分析表明,相对阔叶林地土壤,灌木林、针叶林、退耕台地、草地、退耕坡地、农田土壤的退化程度依次增加,其相对退化指数分别为-25.3%、-56.3%、-56.6%、-56.7%、-62.2%、-68.4%。多层综合评估结果表明农田土壤质量为最低,针叶林地、草地、退耕坡地、退耕台地土壤质量为中等,灌木林地与阔叶林地土壤质量较高。4、喀斯特石漠化地区有地表径流产生,石漠化样地水土流失显著高于有植被覆盖的样地,单次径流系数平均值在1.5～13.8%之间,年平均径流量为75.86mm。不同植被类型间年径流量差异极显著(p<0.01),农耕地产生的年径流量最大,达122.75mm,灌木林地产生的年径流量最小,达54.08mm,径流中泥沙浓度整体表现出春秋季浓度高,夏季浓度低的趋势。不同植被类型间的土壤侵蚀模数差异极显著(p<0.01),侵蚀模数平均达到45.88 t/km~2·a,属于微度侵蚀。径流中全N呈现出随时间而下降的趋势,全P、全K流失浓度呈现出春秋季高、夏季低的趋势。不同植被类型间流失全N、全P、全K总量差异极显著(p<0.01),平均年流失量全N为230.491 mg/m~2·a,全P为4.408mg/m~2·a,全K为929.050mg/m~2·a。5、采用不同浓度的聚乙二醇(PEG)对3个石漠化地区造林树种种子萌发进行人工土壤水分处理,结果表明,不同浓度PEG处理胁迫对种子的萌发均有一定的延缓作用。随着水势的下降,发芽率、发芽指数、活力指数总体呈下降趋势,不同树种变化趋势相似,但变化幅度有明显差异。3个主要造林树种任豆、银荆和滇楸种子萌发的临界PEG值分别为:30%(-1.20MPa)、20%(-0.60MPa)和10%(-0.2MPa)。6、3个主要造林树种幼苗在土壤水分胁迫条件下生长和生物量发生了明显变化。总的趋势为,随土壤含水量的减少,3个供试树种幼苗的苗高、地径、总生物量等生长指标均呈下降趋势。不同水分处理对银荆、滇楸和任豆的根系活力影响趋势也相同,各树种幼苗的根系活力随土壤含水量的减少而呈现下将趋势。但在一定的水分范围内,这3个树种的根冠比(R/S)值均随土壤干旱程度加剧而增大。7、土壤水分胁迫条件下,3个树种幼苗的Pn、Tr、Gs、WUE明显降低,Ci/CO2值和Tleaf-Tair值却明显升高,随着土壤水分胁迫的加剧,影响尤为突出。在轻度胁迫和中度胁迫下影响3个树种幼苗光合作用的因素既包括气孔因素也包括非气孔因素,但在严重和极度干旱时,非气孔因素占主导作用。8、土壤水分胁迫使滇楸、任豆和银荆的可溶性蛋白含量下降。任豆和银荆幼苗脯氨酸含量随着胁迫时间的延长,呈上升的趋势,而滇楸恰好与之相反。土壤水分下,3个树种幼苗酶活性提高的早晚不同,而且SOD和POD酶在各个树种的贡献不同;在胁迫过程中,MDA含量的变化与SOD和POD酶活性呈一定的负相关。更多还原

【Abstract】 Karst widely distributed in the world, and southwest of China was the one of the most typical area. Because the fragile nature environment and human unfit disturbances, rocky desertification was serious in these zone. The area of karst rock desertification in China has always arrived 129.6 thousands km², and such area is expanding 2 500 km² annually. For the ecology control, the main ecology factors and the effects of water stress on the recovery tree species were studied in Guangxi province, Lingyun city. The results show that:（1） The natural succession process of vegetation in Lingyun city of Guangxi province after rocky desertification appearing was divided into the herbosa stage, the stage of herbosa-shrub, the stage of vine-shrub, the stage of subaltern tree forest and the climax stage. Typical plots were set up using space instead of time. The species composition was analyzed in each stage and the species diversity in the layers of herb, shrub, tree and community at different succession stages was measured by the methods of species abundance, Simpson index, Shannon index and Pielou’s evenness index. The results showed that, with the exception of the herb layer, the species abundance in all layers rose steadily when the succession developed from the herb stage, and reached the maximum in the stage of subaltern tree forest. In the herb layer, species abundance and Shannon index fluctuated but Simpson index and evenness index decreased gradually, and reached the minimum in the climax stage. Simpson index, Shannon index and Pielou’s evenness index first increased, followed by a decline, but the stage at which the index reached its maximum was not consistent. Diversity indices of the herb layer were higher than those of the shrub layer in the stage of herbosa. When the succession entered into the stage of herbosa-shrub, Diversity indices of the shrub layer rose and exceeded those of the herb layer. Diversity indices of tree layer were the lowest from the time when arbor appeared.（2） To study the effect of different disturbance to environment microclimate diurnal dynamics in the Karst zone, five typical modes were chosen and light intensity, air temperature, air relative humidity, soil temperature, and soil water content of -5cm were measured. The results showed that different plant types observably changed the composition, coverage, and height of overground vegetation, so the environment microclimate was changed at different degree. The effect of forest was the best, then was shrub, grass, farmland, and Rocky Desertification land. In the rockland, light intensity was strongest, air temperature and soil temperature were highest, air relative humidity and soil water content were lowest, and the variations of the five factors were notable. The microclimatic conditions of rockland developed towards much more dry and hot. While, compared to rockland, in forestland, shrubland, grassland, and farmland, the light intensity 96.4%、52.0%、17.0%、44.2% respectively, air temperature decreased 30.1%、20.2%、12.7%、17.8%, soil temperature decreased 11.5%、8%、2.5%、5.5%, and air relative humidity increased 129.2%、57.2%、18.0%、41.2%, soil water content increased 42.6%、33.2%、15.7%、14.0%. The five factors fluctuations were less than rockland. Light intensity, air temperature, and soil temperature were positive correlation, and negative correlation to air relative humidity and soil water content. Air temperature and soil water content were positive correlation.（3） The soil physical and chemical properties of different plant types in the typical Karst rocky desertification zone were analyzed. The plots included 7 types, such as farmland（FL）, retired terrace farmland（RTL）, retired sloping land（RSL）, grassland （GL）, shrubland（SL）, coniferous forest land（CFL）, broadleaf forest land（BFL）. The physical properties indexes were bulk weight（BW）, water content（WC）, total porosity（TP）, capillary porosity（CP）, non-capillary porosity（NCP）. And the chemical properties consisted of pH, organic matter（OM）, total N, total P, total K, dissoluble N（DN）, dissoluble P（DP）, dissoluble K（DK）, Exchangeable Ca²⁺（EC）.The results show that different plant types did significantly effect on the soil physical and chemical properties. The difference between BW, WC, TP, CP and NCP of 7 types plant types soil was distinct（p<0.01）. Coefficients of variation between 7 types plant types soil respectively were 12.37%、29.72%、18.07%、12.66%、84.70%. The difference OM, total N, total P, total K, DN, DP, DK and EC of 7 types plant types soil was distinct（p<0.01）, too. BW was negative correlation with other indexes, while OM was positive correlation with other indexes. Relative soil quality indexes method was used to evaluated the soil quality, compared to the BFL soil, the relative soil degenerate indexes of SL, CFL, RTL, GL, RSL, FL respectively were -25.3%、-56.3%、-56.6%、-56.7%、-62.2%、-68.4%. Fuzzy multidimensional comprehensive evaluation’s result show that the soil quality of FL was the worst, CFL, GL, RSL and RTL were middle, then the SL and BFL were higher.（4） The rainfall distribution is seasonal change, mainly happened in June to September and minimum in November. There were 108 times rain in whole year, and among them there were 60 times light rain, 25 times moderate rain, 11 times heavy rain, 8 times rainstorm, 4 times heavy rainstorm. Rainstorm and heavy rainstorm mainly effected the whole year rainfall. In research area, there were 53 stages （total 211 days） no-rain-date. No-rain-date was more than rain-date.Runoff could occur in KSD zone, and the runoff coefficient of every time changed between 1.5～13.8%, and the mean runoff was 75.86mm. There was prominence difference between different vegetation types（p<0.01）, the runoff of farmland （122.75mm） was the highest. The sediment concentrations of runoff in spring and autumn were higher than in summer. The soil erosion modulus between vegetation types was prominence（p<0.01）, and the mean erosion modulus was 45.88t/km²·a, belong to slight erosion. The total N concentrations declined with time, while, total P and total K were same to the sediment concentrations change. The difference of gross total N, P, K between different vegetations was prominence（p<0.01）, and the gross was 230.491mg/m²·a, 4.408 mg/m²·a and 929.050 mg/m²·a.（5） The effects of water stress on three trees seeds from rocky desertification area was tested by the treatments with different concentrations of polyethylene glycol（PEG）. The results showed that PEG could retard the germination of stressed seeds. the germination rate, germination index vigor index decreased in total. The change tendency of different drought resistance among three trees was similar, but the changes range was different remarkably.（6） Water stress had significant effects on three seedling height growth and biomass. The main results showed that: activity of root system, shoot length increment, diameter growtgh increment and total biomass of three seedlings declinde with the declining soil moisture. But shoot-root ratio of three tree species enhance with the declining soil moisture.（7） As stress increasing and time delaying, the net photosynthesis rate, transpiration, stomata conduct and WUE were gradually decreased but CO₂ concentration in stomata, COi/CO2 and Tleaf-Tair was increased, the effects becomes severity with the declining soil moisture. The midday depression of photosynthesis under both light and heavier stress may be induced by a combination of stomatal limitation and non-stomatal factors, but under extreme drought conditions, induced mainly by the non-stomatal factors.（8） The soluble protein of all seedling content decreased with water stress strengthened. The two trees seedling proline, Zenia insignis, and Acacia dealbata, increased sharply, but Catalpa fargesii was contrary with them. It demonstrated that different trees had different available osmotic substances when they were under the force of water stress. The acivity of SOD and POD enzymes of three trees seedlings were increased with the water stress, but the time of enhancing differed each other. The content of MDA, however, showed obviously negative corrlelation with activity of protective enzyme （POD and SOD） when water stress happened.更多还原