毛乌素沙地东南缘植被恢复中优势灌丛的保育作用研究

发布时间：2018-06-21 02:28

本文选题：优势灌丛 + 松树　；参考：《陕西师范大学》2016年博士论文

【摘要】：毛乌素沙地东南缘的生态系统受自然和人为因素的影响,荒漠化严重,植被退化迅速,致使该沙区自然恢复的可能性大大降低。在人工植被恢复工程中幼苗的定居是关键阶段,但沙区土壤水分含量低、养分贫瘠、温差大、光照强、竞争、化感、捕食和多风等多种因素却限制幼苗的定居。人们曾经采用过许多不同的植被恢复方法,但由于代价大、风险高、有时甚至成为加速植被退化的原因,恢复效果甚微。因此,该沙区迫切需要发展一种新型的、低花费的、而且有效的恢复方法来维持生态系统功能的稳定,提高植被恢复的速度。保育植物理论(nurse plant theory)是指利用植物间的保育作用,通过保育植物(nurse plant)促进目标物种(target species)的种子萌发或者幼苗定居,从而有效缩短恢复的时间。那该理论是否可应用在毛乌素沙地东南缘的植被恢复中,成为恢复沙地生态系统的一种新型而有效的方法?保育植物对目标物种存在显著的保育作用是该理论能成功应用在植被恢复中的关键。毛乌素沙地东南缘的优势植被类型是灌丛,本研究根据灌丛种的密度和生物学特性选择该沙区优势灌丛柠条(Caragana korsinskii)、沙柳(Salix psammophyila)、紫穗槐(Amorpha fruticosa)作为保育植物,(1)采用野外灌丛剪除试验,通过研究剪除与未剪除优势灌丛冠层下植物群落总地上生物量和物种多样性的差异,从群落水平上确定该沙区优势灌从对冠层下所有目标植物是否存在保育作用;(2)采用幼苗移栽试验,通过选择两年生油松(Pinus tabulaeformis)和樟子松(Pinus sylvestris)幼苗作为目标物种,将其分别种植在开阔地、柠条、紫穗槐和沙柳4种微生境下,连续3a监测油松和樟子松幼苗的存活率和主枝生长长度,从种群水平上研究优势灌丛冠层下和开阔地间两种松树幼苗存活和主枝生长长度的差异,确定优势灌丛对冠层下两种恢复树种幼苗的定居是否存在保育作用;(3)采用温室因子控制试验,模拟保育灌丛冠层下和开阔地间不同的光照及水分条件,研究两种松树幼苗的生长(苗高和基径)和生物量(根、茎、叶及总生物量)特征对光照和水分的响应机制,揭示优势灌丛保育作用形成的机理。本研究不仅能充实保育植物理论,加深对植物间促进作用的方式及机理的了解,而且还为环境恶劣和退化地区发展有效的生态恢复方法提供理论依据和实践支撑,从而加快该理论在我国植被恢复中的应用。主要研究结果和结论如下:研究结果:(1)未剪除柠条、沙柳和紫穗槐灌丛冠层下植物群落总地上生物量及物种多样性显著高于剪除优势灌从的(P0.05)。剪除优势灌从对冠层下植物群落生物量的影响要大于对多样性的影响。固氮的柠条和紫穗槐灌丛冠层下植物群落总生物量均显著高于非固氮的沙柳灌丛的(P0.05);乡土种柠条和沙柳灌丛冠层下植物群落物种多样性均显著高于外来种紫穗槐灌丛的(P0.05)。优势灌丛对豆科、禾本科和杂草植物功能群均具有显著的正效应(P0.05)。柠条和紫穗槐冠层下不同功能群间均存在显著差异(P0.05);沙柳灌丛对豆科功能群的影响显著高于禾本科和杂草功能群(P0.05)。(2)柠条、紫穗槐和沙柳冠层下油松幼苗总存活率均显著高于开阔地的(P0.05),而樟子松幼苗总存活率仅紫穗槐冠层下显著高于开阔地的(P0.05)。保育灌丛冠层下油松幼苗存活率显著高于樟子松幼苗的(P0.05)。紫穗槐冠层下油松和樟子松幼苗总存活率均最高,而且其每年的年度存活率均显著高于开阔地的(P0.05);柠条和沙柳冠层下松树幼苗年度存活率在第二个生长季开始显著低于开阔地(P0.05)。油松幼苗的主枝生长长度在优势灌丛冠层下和开阔地间无显著差异,而樟子松幼苗主枝生长长度在开阔地和紫穗槐冠层下最大(P0.05)。除光照与油松主枝长度不相关外,光照和土壤湿度均与松树幼苗的存活率和主枝长度显著正相关(P0.05)。保育灌丛高度和冠幅面积与油松和樟子松幼苗存活率呈显著正相关(P0.05)。沙柳浸提液对松树幼苗生长影响的试验证实,高浓度浸提液对松树幼苗生长有显著抑制作用(0.05)。(3)柠条、紫穗槐和沙柳冠层下光照强度、大气温度和土壤温度都显著低于开阔地(P0.05),同时优势灌丛的存在增加浅层土壤(0～20 cm)的有机质、速效钾、速效氮、pH值和土壤电导率。光照和水分对松树幼苗生长和生物量特征的影响均显示出显著的交互作用(P0.05)。遮荫条件下,松树幼苗大多数的生长和生物量指标在不同水分条件下的差异基本不明显;干旱条件下,松树幼苗大多数的生长和生物量指标在不同光照条件下也无显著差异。研究结论:(1)毛乌素沙地东南缘优势灌丛柠条、沙柳和紫穗槐在群落水平上显著增加冠层下所有植物的地上总生物量及物种多样性,在种群水平上增加冠层下油松和樟子松幼苗的存活率,而且松树幼苗主枝生长也未受到抑制;因此优势灌丛对冠层下植物群落和两种松树幼苗的定居存在明显的保育作用。(2)保育灌丛的化学效应(固氮和化感)、植株的高度、冠幅大小和结构不同时,其对冠层下植物的保育作用程度也不同。固氮灌丛(紫穗槐和柠条)对松树幼苗存活有持续的保育作用,但柠条冠幅结构紧密,可能因为对光的竞争,减弱保育作用;化感灌丛沙柳大大减弱其对冠层下松树幼苗的保育作用。因此保育植物尽可能选择固氮灌丛,避免选择化感灌丛。外来种紫穗槐植株最高、冠幅面积最大,对冠层下松树幼苗的保育作用最强,但其对物种多样性的影响却较小。保育灌丛对豆科、禾本科和杂草植物功能群均存在保育作用,但不同功能群间和同一功能群内不同物种间均存在着所受保育作用的程度差异。当保育和目标植物均是豆科固氮植物时保育效果不明显。目标物种的光适应能力不同其所受保育作用程度也不同;油松幼苗对光的适应能力强,受保育作用程度大,更适合被选作为恢复树种。(3)优势灌丛的保育作用主要是通过为冠层下植物提供适宜微环境的方式产生的,改善最明显的是光照强度和土壤湿度,其次是土壤有机质和速效氮。光照和水分间的交互作用影响着松树幼苗的生长,而且遮荫缓解了干旱的不利影响,干旱缓解了遮荫的不利影响,这也是优势灌丛对两种光适应能力不同的松树幼苗均具有保育作用的原因。总的来说,保育植物理论是可以应用在毛乌素沙地东南缘的植被恢复中,成为恢复沙地生态系统的一种新型而有效的方法。但是保育灌丛的选择要考虑乡土种还是外来种,以及灌丛的高度、冠幅大小、冠幅结构及化学效应;恢复物种的选择要考虑其自身的生物学特性及其与保育植物的相互作用;从而提高该理论应用在植被恢复中的成功率。
[Abstract]:The ecological system in the southeastern margin of the Maowusu sandy land is affected by natural and artificial factors, desertification is serious, the vegetation degradation is rapid, and the possibility of natural recovery is greatly reduced. In the artificial vegetation restoration project, the settlement of the seedlings is the key stage, but the soil moisture content is low, the nutrient is poor, the temperature difference is large, the light intensity, competition and allelopathy are strong. Many different factors such as predation and windy restrict the settlement of the seedlings. People have used many different methods of vegetation recovery, but because of the high cost, high risk, and sometimes even the cause of accelerating vegetation degradation, the recovery effect is very little. Therefore, the sand area is urgently needed to develop a new, low cost, and effective recovery method. Maintaining the stability of the ecosystem function and improving the speed of vegetation recovery. The conservation plant theory (nurse plant theory) means to use the conservation function of the plant to promote the germination of the target species (target species) or the settlement of the target species (target species) by the conservation plant (nurse plant), thus effectively shortening the time of recovery. In the restoration of vegetation in the southeastern margin of Maowusu sandy land, it is a new and effective method to restore the sandy land ecosystem, which is the key to the successful application of the theory to the restoration of vegetation. The dominant vegetation types in the southeastern margin of Maowusu are shrubs. This study is based on the shrub species. The density and biological characteristics of the sand area were selected as the dominant shrub (Caragana korsinskii), Salix (Salix psammophyila), and Sophora japonica (Amorpha fruticosa) as a conservation plant. (1) the field shrub cutting test was used to study the differences in the total biomass and species diversity of plant communities under the crown layer of the predominant shrub. From the community level, it was determined whether the dominant irrigation in the sand area had a protective effect on all the target plants under the canopy. (2) the seedling transplanting test was used to select 4 young seedlings of Pinus tabulaeformis (Pinus tabulaeformis) and Pinus sylvestris (Pinus sylvestris) as the target species, and they were planted in open land, Caragana, Sophora japonica and Salix, respectively. Under the condition of continuous 3A monitoring of the survival rate and the growth length of the seedlings of Pinus tabulaeformis and Pinus sylvestris, the difference of survival and growth length of two species of pine seedlings under the dominant shrub canopy and open land was studied from the population level, and the conservation effect of the dominant shrubs on the settlement of the seedlings of the two species under the canopy was determined. (3) the greenhouse was used in greenhouse. Factor control test, to simulate the different light and water conditions between under canopy and open land, to study the response mechanism of the growth of two pine seedlings (Miao Gao and base diameter) and biomass (root, stem, leaf and total biomass) to light and water, and to reveal the formation mechanism of the predominant irrigation. This study not only enriches the conservation of the growth of the dominant shrub, but also enriches the conservation of the seedlings. Plant theory, to deepen the understanding of the ways and mechanisms of the promoting effect of plants, and to provide theoretical basis and practical support for the development of effective ecological restoration methods in poor and degraded areas, and thus accelerate the application of this theory in the restoration of vegetation in China. The total aboveground biomass and species diversity of the plant community under the canopy of Salix and Sophora japonica were significantly higher than that of the predominant irrigation (P0.05). The effect of the removal of dominant irrigation on the biomass of plant community under the canopy was greater than that on the diversity. The species diversity of the plant communities under the crown of the native Caragana and Salix shrub was significantly higher than that of the foreign species (P0.05). The dominant shrubs had significant positive effects on the functional groups of legumes, Gramineae and weed plants (P0.05). There were significant differences between different functional groups under the canopy of Caragana and Sophora japonica. The difference (P0.05); the effect of Salix shrub on the functional group of legume was significantly higher than that of the functional group of Gramineae and weeds (P0.05). (2) the total survival rate of Pinus tabaci seedlings under the canopy of panicle and Salix was significantly higher than that in open land (P0.05), while the total survival rate of the seedlings of Pinus sylvestris was significantly higher than that in the open area (P0.05). The survival rate of Pinus tabulaeformis seedlings was significantly higher than that of Pinus sylvestris seedlings (P0.05). The total survival rate of Pinus tabulaeformis and Pinus sylvestris seedlings under the crown layer of Sophora japonica were the highest, and the annual survival rate was significantly higher than that in open land (P0.05). The annual survival rate of the seedlings under the Caragana and Salix canopy began to be significantly lower than the open land in the second growing seasons (P0.05 The growth length of the main branch of Pinus tabulaeformis seedlings had no significant difference between the dominant shrub canopy and the open area, while the growth length of the main branches of the seedlings of Pinus sylvestris seedlings was the largest under the open land and the crown of the Sophora japonica (P0.05). The light and soil moisture were significantly correlated with the survival rate and the length of the main branch of pine seedlings except for the light and the length of the main branch of Pinus tabulaeformis (P 0.05) there was a significant positive correlation between the height and canopy area of the conserved shrub and the seedling survival of Pinus tabulaeformis and Pinus sylvestris (P0.05). The effect of Salix leaching solution on the growth of pine seedlings confirmed that the high concentration extracts had a significant inhibitory effect on the growth of pine seedlings (0.05). (3) the light intensity under the canopy of the Caragana Caragana, the Sophora japonica and the Salix, and the soil temperature and soil The temperature was significantly lower than that of open land (P0.05). At the same time, the presence of dominant shrubs increased the organic matter of shallow soil (0~20 cm), available potassium, available nitrogen, pH value and soil conductivity. The effects of light and water on the growth and biomass of pine seedlings showed significant interaction (P0.05). Under shading conditions, most of the seedlings of pine seedlings were born. The difference of length and biomass under different water conditions was not obvious; under the drought conditions, most of the growth and biomass of pine seedlings had no significant difference under different light conditions. (1) the dominant shrub of the southeast margin of Maowusu sandy land, Salix and Sophora japonica increased significantly under the canopy level. The total biomass and species diversity of the plants increased the survival rate of the seedlings of Pinus tabulaeformis and Pinus sylvestris under the canopy level, and the growth of the main branches of the pine seedlings was not suppressed. Therefore, the dominant shrubs had obvious conservation effects on the settlement of the plant community and the two kinds of pine seedlings. (2) the chemical effects of the conservation shrubs (solid). Nitrogen and allelopathy, the height of the plant, the size of the crown and the structure of the plants are different. The nitrogen fixing shrubs (Sophora japonica and Caragana) have a continuous conservation effect on the survival of the pine seedlings, but the structure of the Caragana is tight, which may be due to the competition of light and weaken the conservation effect; the Salix of the alleloplastic shrub is greatly weakened. The conservation effect on the seedlings of the pine trees under the canopy. Therefore, the conservation plants should choose the nitrogen fixing shrubs as much as possible to avoid the choice of the allelopathic shrubs. The plants of the foreign species are the highest, the largest canopy area, and the best conservation effect on the seedlings under the canopy, but the effect on the species diversity is smaller. There is a conservation effect in all the groups, but there is a difference in the degree of conservation among the different functional groups and the same functional groups. When the conservation and the target plants are all nitrogen fixing plants in the leguminous family, the effect of conservation is not obvious. It has strong adaptability and high degree of conservation, and is more suitable to be selected as a restoration tree. (3) the conservation effect of dominant shrubs is mainly produced by providing suitable microenvironment for plants under canopy, and the most obvious improvement is light intensity and soil moisture, followed by soil organic matter and available nitrogen. Interaction between light and water. The growth of pine seedlings was affected, and shading alleviated the adverse effects of drought, and drought relieved the adverse effects of shading. This was the reason why the dominant shrub had a protective effect on the seedlings of two kinds of pine trees with different light adaptation ability. It is a new and effective method to restore the sandy land ecosystem. However, the selection of conservation shrubs should consider the native or exotic species, the height of the shrub, the size of the crown, the structure of the crown and the chemical effect, and the selection of the restoration species should consider its own biological characteristics and the interaction with the conserved plants. The success rate of the theory applied to vegetation restoration.
【学位授予单位】：陕西师范大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：Q948

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