【作者】 鲁为华；

【导师】 朱进忠；

【作者基本信息】 新疆农业大学 ， 草业科学， 2010， 博士

【摘要】 在气候较剧烈的变化和人为过度干扰下,广泛分布在新疆天山北坡的绢蒿荒漠草地植被的正常发展和更新演替发生了畸变,出现了大面积的退化。本研究从绢蒿荒漠地上植被群落数量及分布特征、土壤种子库数量及分布特征、种子结实规律和主要植物萌发特征等方面阐明围栏封育条件下植被的发展以及变化过程。同时,重点对绢蒿(Seriphidium transiliense,S.brotalense)在种群更新过程中的幼苗的生长发育规律、生理生态特征、种群(包括成株和幼苗)的空间分布格局等进行分析,阐明建群植物对草地更新所起到的作用。最后整合植被、种子繁殖体、土壤种子库、来年幼苗四个阶段的数量数据,探讨退化草地的植被自然更新(循环)模式,揭示绢蒿荒漠的更新恢复特征。主要研究结果如下:(1)围栏封育在短期内不会改变植被的结构组成,但对植被密度具有重要影响。同时,气候的年际波动对植被群落状态影响更为剧烈并且在决定植被状态上居于主导地位。地上植被密度总体上表现出围栏内大于围栏外,而年度间则由于气候波动表现出剧烈的波动现象。由于群落密度在围栏内外及年度间存在差异,由此引起生物量在上述条件下也发生剧烈变化。同时构成群落的物种变化属性、物种多样性特征在年度和围栏二因素的共同作用下趋于复杂化。植被在空间分布状态上总体表现为异质性较强。并且构成群落的主要物种在围栏内外的个体特征也产生了较大分异。(2)群落种子总产量较高,为植被提供了重要的现实更新基础。种子产量主要受围栏和年度气候条件两因素的影响,围栏内种子产量要明显高于围栏外,年际间种子产量的变动更为剧烈,表现为2007>2009>2008年。三种主要植物单株种子结实规律表现各异,其中绢蒿单株种子产量对围栏和年度两因素的变化都极为敏感,在围栏内外和年度间均差异极显著。而叉毛蓬和弯果胡卢巴单株种子产量和单株重量只在年度间存在显著差异。三种植物中以叉毛蓬(Petrosimonia sibirica)萌发各指标均最高,绢蒿次之,弯果胡卢巴(Trigonella arcuta)总体萌发率最低,其中绢蒿和叉毛蓬种子萌发过程对种子大小具有依赖性。(3)各退化梯度围栏内外土壤种子库萌发进程呈现明显的单峰曲线。土壤种子库中包含有大量的可萌发种子,是植被更新潜在的“更新繁殖库”。围栏内土壤种子库种子数量高于围栏外,但物种构成成分都较为简单,萌发植物物种数量在8-10种之间。围栏内土壤种子库和植被物种构成相似性随着退化程度增加逐渐减小,围栏外则表现出相反趋势。各样地土壤种子库密度均表现出随着植被密度增加,种子密度增加。土壤种子库各物种与土壤养分之间存在关联,但同一物种与土壤环境因子之间的关系由于区域不同而表现出明显差异。在水平方向上,不同退化梯度围栏内土壤种子库中各组分种子分布在小尺度上存在自相关,但各变量自相关有正有负,种子密度在空间上的分布较为复杂。不同植物种子在土壤中的分布具有明显空间异质性特征,呈现出明显的斑块状分布。(4)绢蒿幼苗在4-6月为地上部分生长的旺盛时期,随着外界环境条件的变化,幼苗则采取叶片脱落、地上部分生长速度减慢而转向根系生长,地上部分和根系生长呈现出明显的异速生长模式。在干旱胁迫条件下,绢蒿体内Fpro、Sp、MDA含量上升,可通过积累上述调节性物质应对干旱胁迫对自身造成的不利影响,从而使幼苗能够进入种群更新过程。干旱胁迫显著降低幼苗光合速率,并且随着光合有效辐射的增强光合速率增加,其具有明显的光补偿点和饱和点。同时蒸腾速率随光合有效辐射增强而逐渐增加。干旱胁迫使不同CO2浓度下绢蒿幼苗光合速率和羧化效率降低,增高了幼苗的CO2补偿点。(5)当种群密度较大时(中度退化区域),绢蒿幼苗在空间内分布主要以聚集分布为主要分布模式,但由于围栏、生境条件、时间的变化聚集强度有所差别。同时在聚集分布模式下,不同微生境条件下的幼苗发生及存活状态也明显不同,其中凋落物、植被盖度、成株绢蒿的分枝数量、退化程度对幼苗发生和存活影响较大。在种群密度较小的状态下(重度和极度退化区域),绢蒿幼苗在小尺度上分布和母株的关系较为明确,幼苗分布基本集中在距离母株50cm范围内,并且幼苗分布模式在时间和空间上总是向增加个体适合度的分布状态转换。绢蒿成株分布在三种退化梯度下,均表现出在小尺度上为聚集分布,随着尺度的增加,存在分布模式转换的节点,并由聚集分布转换为随机或均匀分布。不同大小级别成株在小尺度上具有密切关联,但随着尺度增加,关联性逐渐减弱。(6)各退化区域围栏内外植被更新过程中,植被、种子、土壤种子库、来年幼苗中所包含物种数量变化不大,在8-12种之间。中度退化区域围栏内外较低的植被密度可产生大量种子并可充实到土壤种子库中去,但围栏内种子库到幼苗的转化效率较低,围栏外转化效率有所提高。重度退化区域围栏内外则表现出高的植被密度,高的种子产量,并由此产生较多的幼苗,种子库到幼苗的转化率很高。极度退化区域围栏内外植被密度较低,但也可产生大量种子,围栏内种子产量和种子库种子密度几乎相等,围栏外种子库种子密度要高于种子产量。三种退化梯度围栏内外植被更新的主要来源是种子繁殖体。中度退化区域有相当数量绢蒿幼苗参与植被更新循环,而其他两区域主要以一年生植物为更新主体。更多还原

【Abstract】 Recently, on the pressure of change of the climate acutely and over-disturbance by the human being, the normal development and succession of Seriphidium desert grassland vegetation became abnormality, and that degraded on large area. This study focuses on seriphidium desert at northern slop in Tianshan Mountain, analyze characteristics of grassland community and characteristics of distribution, the characteristic of fecundity and three major plant seed germination behavior. Describe soil seed bank characters and distribution pattern on horizontal direction, analyze the relationship of soil seed bank varibles, aboveground vegetation and soil nutrients. At the same time, analyze growth rule of seedlings, physiology and ecology characteristic, distribution pattern of Seriphidium(S. transiliense,S.brotaliense) population (include seedling and mature individual) to clarify action of Seriphidium in vegetation regeneration process. Finally, integrate data of vegetation, seed, soil seed bank and seedling to discuss patterns of regeneration of vegetation. The results showed that:(1) In short term fencing, plant density of Seriphidium desert grassland is impacted significantly, but it can not change significantly the structure of plant communities, at the same time, climate changes effect vegetation conditions acutely. Density of aboveground vegetation in inside fence higher than outside fence, and that vegetation density changes acutely because of climate changes during three years. Biomass of community changes significantly because of density of vegetation in different years. The variational characteristics of species, biodiversity index trend to complication. Distribution pattern of vegetation has heterogeneity significantly. Individual morphological characteristics of main plant species appears differentiation.(2) High seed yield of community provide important regenerated foundation for regeneration of vegetation. Fence and climate effect seed yield of community, seed yield in inside fence is higher than outside fence significantly, and fluctuating of seed yield is more acutely in different years because climate changes, and shows 2007>2009>2008. Fecundity characteristic of three plants (Seriphidium, Petrosimonia sibirica, Trigonella arcuata) are different, Seed yield and weight of single Seriphidium seedling are very sensitive to fence and climate changes in different years. Seed yield and weight of single Seriphidium seedling have difference significantly inside and outside fence in different years. Seed yield and weight of single Petrosimonia sibirica and Trigonella arcuata have difference significantly in different years. Germination rate of Petrosimonia sibirica are the highest among three plants species, followed by seriphidium, germination rate of Trigonella arcuata is the lowest because of dormancy. seriphidium and Petrosimonia sibirica seeds germination process depend on the seed weight.(3) Seedling emergence pattern from soil seed bank samples in different plots were unimodal curve. Large numbers of germinating seeds exist in soil seed bank and provide potential“regenerate bank”for vegetation regeneration. Seed number is higher in inside of fence than outside fence in soil seed bank, but composition of plant species is very simple and plant species number is 8-10.The similarity relationship of species composition between soil seed bank and vegetation decrease with increasing of degradation inside fence, then inverse trend in outside fence. Species of soil seed bank associate with soil nutrient, but this relationship of the same species is different in different plots. On horizontal direction, distribution pattern of every component of soil seed bank appear autocorrelation in small scale, but autocorrelation of variables is positive and negative alternately. Distribution of seed density is very complicated, and that has spatial heterogeneity significantly, appear mosaic distribution pattern.(4) Accumulation of aboveground biomass of Seriphidium seedling is very quickly during Apr-Jun, and then seedlings begin desquamate leaves, accumulation of aboveground biomass decreasing and length of root increasing, growth of aboveground and underground appears allometry type. Fpro,Sp and MDA concentration increase under drought condition,so Seriphidium seedling can accumulate physiological adjustment substance to resist drought condition, and make seedling come into regeneration of population. NPn of seedling decrease under drought condition and NPn increase with increasing of Photosynthetically available radiation, and seedling has light saturation point and light compensation point. Transpiration rate increasing with increasing of Photosynthetically available radiation. Drought condition reduce NPn of seedling and velocity of carboxylase/oxygenas, increasing CO2 compensation point of seedling.(5) When population density is very high(MD), seedlings are all clumped pattern of distribution in both inside and outside the fence , but the degree of aggregation is different inside and outside of the fence due to spatial heterogeneity of the micro-environmental conditions, relationships of seedling quantity and environment indicate that number of seedlings are positively correlated with environmental factors, litter, coverage of vegetation, branch of mature seriphidium individual and degree of degradation effect emergence and survival of seedling significantly. When population density is very low(SD and MD), relationship of seedling and maternal is very clear, distance between maternal and seedling is 50cm, and distribution pattern of seedling covert in spatio-temporal to increase individual fitness. Seriphidium mature population is usually characterized by clumped distribution in small-scale in three degree of degradation, when reach to threshold of the clumped distribution then shift to random distribution with increasing of scale. According to spatial association analysis of two sizes, results showed that two size of Seriphidium population is positive association in small-scale in three degradation gradient, but association is waning with increasing of scale.(6) Plant species number of vegetation, seeds, soil seed bank and seedling is 8-12, so composition of vegetation is simple. Lower density of vegetation can produce a large number seeds and come into soil seed bank, convert efficiency of soil seed bank to seedling is very low in MDI but that is increase in MDO. There are high density of vegetation , high seed yield and can produce a large number of seedling in SDI and SDO, convert efficiency of soil seed bank to seedling is very high. Lower density of vegetation can produce a large number of seeds in HDI and HDO, seed yield is equal to density of soil seed bank in MDI, but density of soil seed bank is higher than seed yield in HDO. Resource of regeneration of vegetation is seeds in three gradient of degradation. A large number of Seriphidium seedling come into recycling of regeneration in MDI and MDO, and that annual plant species is regeneration dominating in two others gradient of degradation.更多还原