【作者】 张慧荣；

【导师】 杨持；

【作者基本信息】 内蒙古大学 ， 生态学， 2008， 博士

【摘要】 本文通过研究不同生活型草原植物对环境变化的反应,不同干扰条件下不同生活型植物种群构件可塑性变化和再生生长,以及在群落(退化或恢复)演替中不同生活型植物种群的替代规律和补偿作用,比较了不同生活型草原植物生长差异,研究结果如下:(1)以植物单株干重作为对环境变化反应的指标,在不同的空间尺度上研究了不同生活型草原植物对环境条件变化的反应,结果表明,在大尺度上不同生活型草原植物单株重的变异系数大小依次为匍匐型＞根茎型＞丛生型＞直根型,说明匍匐型植物和根茎型植物对环境变化的反应最敏感;在中尺度上不同生活型草原植物单株重的变异系数依次为根茎型＞匍匐型＞丛生型＞直根型,反应规律与大尺度的变化基本相同;在小尺度上不同生活型草原植物单株重的变异系数依次为扁蓿豆＞冷蒿＞大针茅＞冰草＞糙隐子草＞羊草,仍然反映出匍匐型植物对环境变化最敏感的规律,但根茎型和丛生型的反应与大尺度和中尺度有差别,这是由于小尺度上环境的空间异质性小,还不足以使各种生活型植物单株重的变异性规律完全表现出来。(2)在野外自然放牧梯度上,不同生活型草原植物构件可塑性变化和生物量变化表现出不同的规律。根茎型植物羊草的地上、地下和总生物量随着放牧强度的增加而明显的降低,冰草的生物量虽然随着放牧强度的加剧有增加的趋势,但不显著;丛生型植物大针茅的地上、地下和总生物量随着放牧强度的增加而明显的降低,但分蘖数却随放牧强度的增加而增加;匍匐型植物冷蒿随着放牧强度的增加,枝条密度增加,枝条长度变短,不定根数量增多,而枝条的平均干重降低。这说明分枝密度和个体大小之间存在一定的补偿性。(3)在不同的干扰条件下,不同生活型草原植物的构件可塑性变化和生物量的变化有一定的相似性,也存在不同之处。在野外模拟放牧影响下,轻度放牧可促进根茎植物的生长,随着放牧强度的增加,株高降低,呈单峰型变化;模拟放牧对丛生型大针茅、匍匐型冷蒿和直根型植物的生长有抑制作用,随着放牧强度的增加,这些植物的植株变矮。盆栽牧草的模拟啃食实验表明,啃食干扰下,根茎型植物羊草的节间距变化不明显;丛生型植物大针茅的分蘖数随着啃食强度的增加而显著降低,这些构件变化与野外自然放牧梯度上的研究结果正好相反;匍匐型植物冷蒿的枝条变短、不定根数量增加,这些耐牧特征与野外自然放牧梯度上观测到的植物耐牧机制是一致的。(4)模拟放牧干扰下,不同生活型草原植物的再生速度表现出不同的特点。根茎型植物的再生速度均随着模拟放牧强度的增加而增加。在同一干扰强度下,生长盛期羊草的再生速度低于生长初期;丛生型植物大针茅的再生速度随着干扰强度的增加而显著的增高,生长初期的再生速度比生长盛期高;匍匐型植物冷蒿的再生速度随着干扰强度的增加而降低,放牧对冷蒿再生生长的抑制作用在生长盛期比生长初期明显。(5)群落演替(退化或恢复)过程中,不同生活型植物的替代规律明显。在群落退化过程中,地面芽植物生物量随放牧强度的加剧呈波动下降趋势,在群落中的比例却随着放牧强度的增加而上升,在中牧、重牧阶段均高于其它生活型植物。随着放牧强度的增大,地下芽植物的密度和生物量显著下降,在群落中的比例逐渐下降;地上芽植物密度和生物量却随着强度的加剧而极显著的升高,随之在群落中的作用和地位也随着干扰强度的增加而提高。显然,地下芽植物羊草在群落中的作用随着放牧强度的增加而明显的减弱,在重牧干扰下被地上芽植物替代。因此说,群落的变化主要反映在不同生活型植物种群在群落中作用大小的消长上。在群落恢复过程中,地下芽植物密度和生物量逐年增加,在群落中的比例和作用逐年增强,地上芽植物密度和生物量逐年下降,在群落中的比例和作用随之降低,地下芽植物逐渐取代了地上芽植物。说明放牧空间梯度上的群落与恢复演替时间梯度上的群落有类似的变化规律,只是方向相逆。(6)不同生活型草原植物种群在群落退化演替中的补偿作用不同。根茎型植物羊草种群在放牧干扰下不具备超补偿能力,仅冰草在轻牧下表现为等补偿,因而,根茎型植物随着放牧强度的增加逐渐被其它种群替代。丛生型植物大针茅在轻牧和中牧干扰下出现超补偿生长,糙隐子草在中牧和重牧下出现超补偿生长。匍匐型植物冷蒿在不同强度干扰下均具有超补偿生长能力,并且随着放牧强度的增加超补偿生长能力增强。因此在重牧阶段,冷蒿种群取代根茎型植物羊草,成为建群种,羊草草原退化为冷蒿小禾草草原。更多还原

【Abstract】 This dissertation studied on the growth of different life form steppe plants through the analysis of reactions of different life form steppe plants to environmental change, the analysis of growth plasticity and regeneration growth of modules of grass populations, and the analysis of displacement and compensation growth among different life form grass populations.(1) Reactions of different life form steppe plants to environmental change were researched in different spatial scales by dry weight per plant index. The results showed that, in large spatial scale, from large to small the rank of coefficient of variance (cv) of dry weight per plant of life form steppe was that stolon grass > rhizome grass> bunch grass> taproot grass, this proved that stolon grass and rhizome grass were more sensitive to environmental change; In middle spatial scale, the rank from large to small of cv of dry weight per plant of life form steppe was that rhizome grass> stolon grass > bunch grass> taproot grass, the reaction rule in middle spatial scale was similar with the reaction in large scale; In small spatial scale, the rank of cv of dry weight per plant of species was that Melilotoides ruthenica>Artemisia frigida>Stipa grandis>Agropyron michnoi> Cleistogenes squarrosa >Leymus chinensis, this also proved that stolon grass was more sensitive to environmental change than other types, but the reactions of rhizome grass and bunch grass in small spatial scale were some different with the reactions in middle scale and large scale, because the spatial heterogeneity in small spatial scale was not large enough to make the reaction rules of different life form steppe plants clearly.(2) There was a significant growth plasticity of modules of plant populations and biomass under natural grazing gradients. Aboveground weight, underground weight, and biomass of Leymus chinensis, as one rhizome grass, significantly decreased with grazing intensity increased. Biomass of Agropyron michnoi increased with grazing intensity increased, but not significant. Aboveground weight, underground weight, and biomass of Stipa grandis, one bunch grass, decreased obviously with grazing intensity increased, but tiller number increased with grazing intensity increased. With grazing intensity increased, Artemisia frigida, one stolon grass, its shoots density and adventitious roots number increased, but dry weight per shoots and shoots length decreased. This proved that there was a complemental relationship between shoots density and shoots weight.(3) Under different interferential measures, plasticity of modules and biomass variance of different life form steppe plants were similar, but in some aspects, there were some difference.In field artificial grazing measures, the growth was single peak type with grazing intensity, low grazing intensity could improve the growth of rhizome grass, and plant height reduced if artificial grazing intensity increased more. But for bunch grass Stipa grandis, stolon grass Artemisia frigida and taproot grass, the growth restrained by artificial grazing, plant height also decreased with grazing intensity increased.The results of artificial grazing experiment in pots showed that, rhizome internode length of rhizome grass Leymus chinensis did not change obviously. Bunch grass Stipa grandis’s tiller number decreased with artificial grazing intensity increased. The rules of modules of artificial grazing experiment in pots was reverse with the rules in natural field grazing gradients. But for stolon grass Artemisia frigida, adventitious roots number increased and shoots length decreased with artificial grazing increased, this was same with the results from field grazing.(4) Growth speeds of regeneration of different life form steppe plants were not same in artificial grazing experiments. Growth speeds of regeneration of rhizome grass increased with artificial grazing intensity increased. Growth speed of regeneration of Leymus chinensis during initial stage was lower than speed during flourishing stage under same grazing intensity. Regeneration growth speed of bunch grass Stipa grandis significantly increased with grazing intensity increased, and growth speed of regeneration during initial stage was higher than speed during flourishing stage. Regeneration growth speed of stolon grass Artemisia frigida decreased with grazing intensity increased, and graze influenced Artemisia frigida’s growth speed of regeneration during flourishing stage more than speed during initial stage.(5) The displacement among different life form steppe plants were obvious during community succession (degradation succession and restoration succession).During community degradation succession, hemicryptophytes biomass fluctuant decreased with grazing intensity increased, component percentage of hemicryptophytes in community increased with grazing increased, the percentage of hemicryptophytes was higher than other life form plants in moderate grazing intensity and heavy grazing intensity. Biomass and density of geophyte decreased obviously with grazing intensity increased, component percentage of geophyte decreased with grazing increased. However, biomass and density of chamaephyte increased very significantly with grazing intensity increased, chamaephyte play a more and more important role in community when grazing intensity increased. So, geophyte Leymus chinensis’?, role in community decreased obviously while grazing intensity increased, and displaced with chamaephyte species in heavy grazing intensity, community transformation was mainly reflected by the change of roles of different life form steppe plants in community.During community restoration succession, biomass and density of geophyte increased year by year, and play a more and more important role in community. On the contrary, biomass and density of chamaephyte decreased year by year, play a less and less important role in community, and chamaephyte was displaced by geophyte gradually. The evidences proved that community succession in grazing gradients was similar with that in restoration succession, but the direction was reverse.(6) There were different compensation growth of different life form steppe plants in community degradation succession. Rhizome grass Leymus chinensis population did not have the ability of over-compensatory growth under grazing influence, and the ability of compensatory growth of rhizome grass Agropyron michnoi was equal-compensation, so that rhizome grass were displaced by other populations with grazing intensity increased in degradation succession. There were over-compensation growth of bunch grass Stipa grandis under low and moderate grazing intensity, and there were over-compensation growth of Cleistogenes squarrosa under moderate and heavy grazing intensity. Stolon grass Artemisia frigida had the ability of over-compensatory growth under all grazing gradients, and the ability of over-compensatory growth increased with grazing intensity increased, so that Artemisia frigida displaced rhizome grass Leymus chinensis as constructive species in community, and Leymus chinensis steppe was degraded into Artemisia frigida short bunchgrasses steppe.更多还原