【作者】 田青；

【导师】 曹致中； 王国宏；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2009， 博士

【摘要】 草原生态系统是草地畜牧业发展的主要物质支撑,也是保护自然生态系统的重要屏障,在维护国家食品安全和生态安全中具有十分重要的战略地位。然而,全球气候变化以及草原干旱化已导致草地退化或荒漠化的严重后果。应该采取怎样的对策才能遏制或减轻干旱胁迫的负面影响,是迫切需要回答的科学问题。回答这些问题,必须首先弄清楚草地生态系统对干旱胁迫的响应格局以及胁迫下系统功能维持的机理。目前,内蒙古地区植物性状对降雨量变化的响应及其对生态系统功能影响的研究相对缺乏。本研究以我国内蒙古典型草原为研究对象,通过人工遮雨以及增水模拟未来降雨量可能的变化趋势,以剖析典型草原植物性状对降雨量变化的响应格局以及干旱胁迫下草地系统功能的维持机制。研究地点位于内蒙古自治区锡林郭勒盟东南端的多伦县,中国科学院植物研究所内蒙古多伦十三里滩恢复生态学试验示范研究站。试验中选取了14种典型草原常见植物作为研究对象,以Cornelissen等提出的全球植物功能性状分类体系手册(Cornelissen et al.,2003)中的国际间植物性状测度的通用方法为主要依据,选择10个适用于典型草原植物的性状进行测定,模拟降雨量分别为345mm(5～8月平均降雨量增加40～50%)、115mm(5～8月平均降雨量减少40～50%)以及2004、2005年度生长季正常降雨。主要研究结果如下:1.通过对比分析不同降雨量情景下典型草原植物性状变化情况并根据其性状响应趋势进行聚类分析可以看出:(1)不同降雨量情景下典型草原植物性状变化响应趋势比较复杂,并非依据以植物生物学特征等普通植物分类学指标来刻画的功能群如:豆科、禾本科以及杂类草植物功能群进行响应变化;(2)在降雨量减少40～50%情景下,可以根据典型草原植物的10种性状特征划归为4个性状响应群组。这4个性状响应群组的植物组合分别是:①冷蒿(Artemisia frigida Willd)+马蔺(Iris lactea Pall.var.chinensis Koidzumi)+糙叶黄芪(Astragalus scaberrimus Bunge)+冰草(Agropyron cristatum(L.)Gaertner)+克氏针茅(Stipa krylovii Roshevitz)+扁蓄豆(Pocockia ruthenica(L.)P.Y.Fu)+阿尔泰狗哇花(Heteropappus altaicus(Willd.)Novopokrovsky)+小叶棘豆(Oxytropis microphylla(Pall.)DC.);②糙隐子草(Cleistogenes squarrosa(Trin.)Keng)+早熟禾(Poa annua L.)+委陵菜(Potentillachinensis B.);③二裂叶委陵菜(Potentilla bifurca L.)+星毛委陵菜(Potentilla acaulisL.);④糙苏(Phlomis umbrosa Turcz.)。(3)在降雨量增加40～50%情景下,可以根据典型草原植物的10种性状特征划归为4个性状响应群组。这4个性状响应群组的植物组合分别是:①早熟禾(Poa annua L.)+克氏针茅(Stipa krylovii Roshevitz)+马蔺(Iris lactea Pall.var.chinensis Koidz)+冷蒿(Artemisiafrigida Willd)+扁蓄豆(Pocockia ruthenica(L.)P.Y.Fu)+星毛委陵菜(Potentillaacaulis L.)+二裂叶委陵菜(Potentilla bifurca L.);②糙苏(Phlomis umbrosa Turcz.)+糙叶黄芪(Astragalus scaberrimus Bunge)+小叶棘豆(Oxytropis microphylla(Pall.)DC.)+委陵菜(Potentilla chinensis B.);③冰草(Agropyron cristatum(L.)Gaertner)+糙隐子草(Cleistogenes squarrosa(Trin.)Keng);④阿尔泰狗哇花(Heteropappus altaicus(Willd.)Novopokrovsky)。2.不同降雨量情景下,群落水平上典型草原繁殖体重量(PM)与叶片氮含量(LNC)为极显著的负线性相关(相关系数为-0.818):比叶面积(SLA)与叶片干物质含量(LDMC)为显著的负线性相关(相关系数为-0.640):与茎密度(SSD)为极显著的负线性相关(相关系数为-0.735):叶面积(LS)与叶片氮含量(LNC)为显著的线性相关(相关系数为0.544):与0cm～10cm根重(FLRM)为极显著的负线性相关(相关系数为-0.666):茎密度(SSD)与叶片干物质含量(LDMC)为显著的线性相关(相关系数为0.570):根重密度(RSD)与0cm～10cm根重(FLRM)为极显著的线性相关(相关系数为0.786)。在不同降雨量情景下,试验样地群落的最大地上生物量干重(ANPP)与群落植物性状中的比叶面积(SLA)、叶片氮含量(LNC)极显著相关,相关系数分别为0.718和0.669。群落最大地上生物量鲜重与群落植物性状中的比叶面积(SLA)、叶片氮含量(LNC)显著相关,与繁殖体重量(PM)、茎密度(SSD)显著负相关,相关系数分别为0.552、0.552以及-0.531、-0.554。就本研究探讨的10类植物性状看来,典型草原系统功能特征在很大程度上受制于植物比叶面积(SLA)、叶片氮含量(LNC)、茎密度(SSD)、以及繁殖体重量(PM),以上4类性状应是与典型草原系统功能紧密相关的植物功能性状。3.根据群落植物性状与净初级生产力相关性建立了回归模型,通过模型建立的多元线性回归方程为:y(ANPP)=-1 01.757+6.692X1(SLA)+1.549X2(LNC)+0.579X3(PH),由于在茎密度性状(SSD)、繁殖体重量性状(PM)在14种典型草原植物的测度上均出现缺失值,因此未引入模型。4.减少降雨可以明显降低样方的地上生物量而增加降雨与正常降雨量情景下地上生物量的变化无明显差异。本研究的样地尚处在群落发展的早期阶段,一些比较适应于正常降雨的物种能够占据较大比例的空间因而具有较高的地上生物量。因此,群落地上生物量不一定随降雨量增加而增加。这种在群落的初始阶段观察到的降雨量/地上生物量模式应不同于成熟群落。5.凋落物分解速率与地上生物量(干重/鲜重)以及降雨量水平极显著相关,相关系数分别为0.718,0.698和0.687。高的降雨量水平可以导致高的凋落物分解速率。就草原生态系统而言,降雨量增加将增加优势植物对内蒙古半干旱典型草原的碳循环和养分动态的贡献。更多还原

【Abstract】 Grassland ecosystems are the main material support for pastoral development.They are an important barrier for protecting natural ecosystems and play a very important role in safeguarding the national food supply and ecological security.Global climate change and drought,however,have led to grassland degradation and desertification.What measures should be taken to prevent or reduce the negative impact of drought stress is an urgent issue that needs to be explored.To discuss the possible solutions and challenges,it is necessary to first clarify the response patterns and maintenance mechanisms of ecosystem functions under drought stress.At present,the study of the responses of plant traits under rainfall disturbances and the effects on ecosystem functions in Inner Mongolia typical grassland are rarely covered.This research was conducted in a typical grassland in Inner Mongolia,China,from 2004 through 2005.Through simulation and controlled experiments,the response patterns of ecosystem functions to maintain mechanisms of grassland ecosystems was analyzed. The study site is located at the Plant Institution of the Chinese Academy of Sciences in Duolun County,southern Inner Mongolia.Samples were obtained from 14 kinds of typical, common,grassland plants and 10 plant traits from among them were selected for observation in the experiments,mainly based on the methodology introduced in A Handbook of Protocols for Standardized and Easy Measurement of Plant Functional Traits Worldwide(Cornelissen et al.,2003).Simulated rainfall was 345 mm(May to August average rainfall increased by 40～50 percent) and 115 mm(May to August average rainfall reduced by 40～50%),the May to August average rainfall in 2004 and 2005.The main findings are as follows:1.By comparing and analyzing the different plant traits and ecosystem functional characteristics under three different rainfall scenarios,the results showed:(1) The response of Inner Mongolia grassland plant traits to the ecosystem is comparatively complex and not correlated with classical plant taxonomy naturalized as Legumes,Gramineae and non-Legume and non-Gramineae forbs;(2) When rainfall was reduced by 40-50%the response could be categorized into 4 plant groups according to changes in plant traits of 10 typical steppe species: Under a 115 mm rainfall scenario,they can be categorized into four groups:①(Artemisia frigida Willd.) +(Iris lactea Pallas var.chinensis Koidzumi) +(Astragalus scaberrimus Bunge) +(Agropyron cristatum(L.) Gaertner) +(Stipa krylovii Roshevitz) + (Pocockia ruthenica(L.) P.Y.Fu) +(Heteropappus altaicus(Willd.) Novopokrovsky) + (Oxytropis microphylla(Pallas) DC.);②(Cleistogenes squarrosa(Trin.) Keng) +(Poa annua L.) +(Potentilla chinensis Bunge);③(Potentilla bifurca L.) +(Potentilla acaulis L.);④(Phlomis umbrosa Turcz.).(3) Under a 345 mm rainfall scenario,they be categorized as four groups:①(Poa annua L.) +(Stipa krylovii Roshevitz) +(Iris lactea Pall.var.chinensis Koidz) +(Artemisia frigida Willd) +(Pocockia ruthenica(L.) P.Y.Fu) +(Potentilla acaulis L.) +(Potentilla bifurca L.);②(Phlomis umbrosa Turcz.) +(Astragalus scaberrimus Bunge) +(Oxytropis microphylla(Pall.) DC.) +(Potentilla chinensis B.);③(Agropyron cristatum(L.) Gaertner) +(Cleistogenes squarrosa(Trin.) Keng);④(Heteropappus altaicus(Willd.) Novopokrovsky).2.Under different scenarios,community plant traits,such as propagule mass(PM) were significantly negatively and linearly correlated with leaf nitrogen concentration(LNC),the correlation coefficient was -0.818;The specific leaf area(SLA) was negatively correlated with leaf dry matter content(LDMC) and significantly negatively correlated with stem specific density(SSD)(the correlation coefficient was respectively -0.640 and -0.735); Leaf size(LS) was correlated with leaf nitrogen concentration(LNC) and significantly negatively correlated with the first layer root mass(FLRM)(the correlation coefficient was respectively was 0.544 and -0.666);The stem specific density(SSD) was correlated with leaf dry matter content(LDMC)(the correlation was 0.570);The root specific density was correlated with first layer root mass(FLRM)(the correlation was 0.786).The aboveground biomass(ANPP) was significantly correlated with specific leaf area (SLA) and leaf nitrogen concentration(LNC).The correlation was 0.718 and 0.669.The fresh-ground biomass was positively correlated with the SLA,LNC and negatively correlated with stem specific density(SSD) and propagule mass(PM).The correlation coefficient,was respectively 0.552,0.552,-0.531 and -0.554.In terms of the 10 types of plant traits analyzed in this research,it was found that to a large extend the systematic functional characteristics of a typical Inner Mongolia grassland are determined by SLA,LNC,SSD as well as PM.The above plant traits might be those plant functional traits of Inner Mongolia grassland plants which closely related to.3.The model of multiple linear regression equation was established with variables of community plant traits and ANPP.y(ANPP)=-101.757+6.692 X1(SLA) +1.549 X2 (LNC) +0.579 X3(PH).Due to missing values for stem specific density(SSD) and propagule mass(PM),these two plant traits were not included in this model.4.The aboveground biomass obviously decreased with a reduction in rainfall while increase in rainfall had no significant impact.The sampled site was a young grassland community at an early developmental stage.The observations reveal that some species which are more adapted to normal rainfall occupy more space and thus gain a higher aboveground biomass,which explains why an increase in rainfall did not directly lead to a rise in above ground biomass.This observation revealed a rainfall-aboveground biomass model difference between young and mature communities.5.Litter decomposition rate(LR) was significantly correlated with aboveground biomass (dry weight / fresh weight) and rainfall scenarios;the correlation respectively was as 0.718,0.698 and 0.687.A higher level of rainfall can lead to a higher litter decomposition rate.It could concluded that an increase in rainfall will increase the carbon cycle and nutrient dynamic contribution in typical Inner Mongolian grassland ecosystems.更多还原