【作者】 陈海军；

【导师】 王明玖；

【作者基本信息】 内蒙古农业大学 ， 草业科学， 2011， 博士

【摘要】 2008年和2009年,以内蒙古荒漠草原短花针茅、冷蒿和无芒隐子草主要植物种群为研究对象,采用野外“随机固定样线样方法”和室内分析相结合的方法,分析和探讨了不同载畜率水平下主要植物种群繁殖性状、资源分配、营养分配以及生态化学计量特征的变化及其对放牧干扰的响应与适应,综合比较分析了荒漠草原的适宜载畜率水平,为今后荒漠草原放牧管理提供理论依据。试验样地具有连续7年的放牧历史,采用完全随机区组设计,共设4个载畜率水平,分别为0、0.91、1.82和2.71羊单位/公顷/半年,分别代表对照区(CK)、轻度(LG)、中度(MG)和重度(HG)放牧强度,每个载畜率水平设3次重复,供试羊只为2岁蒙古细毛羯羊。短花针茅种群繁殖性状主要包括绝对高度、株丛密度、株丛面积、营养枝与生殖枝数量及长度、营养枝基径、成熟种子性状(种子长度、直径和千粒重)、芒柱性状(芒柱长度、柔毛长度、膝曲回数以及膝曲点位置)、根系性状(根系数量、平均长度、平均直径、根长密度、比根长以及根面积指数)和根系生物量(主根和侧根生物量);资源生物量分配主要包括颖果生物量(成熟种子、成熟种子芒柱以及未成熟种子和芒柱生物量)、茎生物量(营养枝茎、生殖枝茎和茎总生物量)、叶总生物量(营养枝叶、生殖枝叶和叶总生物量)、营养枝和生殖枝总生物量、地上总生物量以及根系生物量(主根、侧根和根系总生物量)。冷蒿和无芒隐子草种群繁殖性状主要包括绝对高度、株丛密度、株丛面积、营养枝与生殖枝数量及长度、营养枝基径、根系生物量(主根和侧根生物量);资源生物量分配则包括地上部分(茎、叶和茎叶总生物量)和地下根系生物量(主根、侧根和根系总生物量)。短花针茅、冷蒿和无芒隐子草营养分配主要包括上述各构件全N和全P的分配。生态化学计量比包括各构件的C∶N、C∶P和N∶P计量特征。主要研究结果如下:(1)生长旺季(7月和8月),随着载畜率的增加,短花针茅、冷蒿和无芒隐子草种群绝对高度和根系总生物量降低,枝条总密度增加。其中,短花针茅营养枝密度和比根长增加,生殖枝密度、根系数量和根表面积指数减少(降低);冷蒿种群营养枝密度和不定根密度增加。(2)放牧显著降低了短花针茅6月结实的种子长度、直径、粒重(500粒)以及芒柱重(500根)(P<0.05),对9月成熟种子性状无显著影响(P>0.05)。6月和9月成熟种子芒柱性状均在LG达到最大值,且9月成熟种子芒柱长度、芒柱柔毛长度、数量以及密度显著高于6月成熟种子芒柱(P<0.05)。(3)短花针茅成熟种子芒柱膝曲点位置表现为6月成熟种子芒柱二回膝曲>9月成熟种子芒柱一回膝曲>6月成熟种子芒柱一回膝曲,彼此间差异显著(P<0.05)。6月成熟种子芒柱一回和二回膝曲点位置均随载畜率的增加而降低,9月成熟种子芒柱一回膝曲点位置受放牧的影响不明显(P>0.05)。(4)随着载畜率的增加,短花针茅株丛地上部分及营养枝资源分配比例、未成熟种子与芒柱资源分配比例增加;生殖枝生物量分配比例、成熟种子和芒柱资源分配比例降低;株丛整体、营养枝和生殖枝生物量向叶的分配比例增加,向茎的分配比例减少。株丛中营养枝分配比例显著高于生殖枝分配的比例(P<0.05)。(5)放牧增加了冷蒿和无芒隐子草种群茎资源分配比例,而降低了叶资源分配比例,致使茎叶比增加;放牧显著降低了冷蒿种群主根与侧根资源分配比例(P<0.05),而增加了无芒隐子草主根和侧根资源分配比例,且侧根分配比例在LG达到最大值,LG促进了无芒隐子草根系的生长。(6)短花针茅各构件全N含量均在LG达到最大值;6月成熟种子全N和全P含量最高,主根全N含量次之,生殖枝叶全P含量最低;营养枝茎和叶全N(P)含量分别高于生殖枝茎和叶,茎高于叶;种子全N(P)含量高于芒柱;主根全N(P)含量高于侧根。冷蒿各构件全N和全P含量变化顺序为叶>茎>主根>侧根;无芒隐子草各构件全N和全P含量变化顺序为叶>茎>侧根>主根。(7)短花针茅种群营养枝茎和叶以及6月与9月成熟种子均受N限制;生殖枝茎在CK和LG下受N限制,在MG和HG下则受P限制;生殖枝叶受P限制。冷蒿茎、主根和侧根均受N限制,叶在CK受P限制,而在LG、MG和HG下受N和P共同限制。无芒隐子草茎和主根均受N限制;叶受N和P共同限制;侧根在CK受P限制,在LG、MG和HG下受N和P共同限制。总之,从种群繁殖资源分配和营养分配角度而言,LG为内蒙古短花针茅荒漠草原适宜的载畜率水平。其中,短花针茅株丛整体资源分配格局为叶>茎>颖果>根;地上部分>地下根系;营养枝>生殖枝;营养枝叶>生殖枝叶;营养枝茎>生殖枝茎;主根>侧根。冷蒿资源分配格局为茎>主根>叶>侧根;地上部分>地下根系。无芒隐子草资源分配格局为茎>主根>叶>侧根;地上部分>地下根系。短花针茅种群地上部分在CK、LG和MG下受N限制,在HG下受P限制;地下根系受P限制;种群整体在CK和LG下受N和P共同限制,在MG和HG下受P限制。冷蒿和无芒隐子草种群整体、地上部分和地下根系均受N限制。更多还原

【Abstract】 The effects of stocking rates on plant population reproductive characteristics, resource allocation, nutrient allocation and stoichiometric characteristics of Stipa breviflora, Artemisia frigida and Cleistogenes songorica in Inner Mongolia desert steppe were measured and analyzed in 2008 and 2009, through the method of combining the fixed sampling quadrat randomly outside with analysis inside. The optimal stocking rate in desert steppe was analysed synthetically in order to provide theoretical basis for the grazing management in desert steppe in the future.The experimental site had been grazing for over 7 years, and was designed with random blocks completely. The experimental treatments were composed of 4 stocking rate levels (0, 0.91, 1.82, and 2.71 sheep hm-2half year-1), and denoted control (CK), light grazing (LG), moderate grazing (MG), and heavy grazing (HG), respectively. Each stocking rate level included three replications. The experimental livestock was two years old Mongolian wether with fuzz.The population reproductive characteristics of Stipa breviflora included absolute height, bunch density, bunch area, quantity and length of forage and reproductive branch, basal diameter of forage branch, characteristics of mature seed (length, diameter and thousand seed weight), awn characteristics (length of awn and pubescence, knee number and knee bending point position), root characteristics (root number, average length and diameter, root length density, specific root length and root area index) and root biomass. The resource biomass allocation including caryopsis biomass (mature seed and its awn, green seed & awn biomass), stem biomass (stem of forage and reproductive branch and total stem biomass), leaf biomass (leaf of forage and reproductive branch and total leaf biomass), total biomass of forage and reproductive branch, aboveground biomass and root biomass (taproot, lateral root and total root biomass).The population reproductive characteristics of Artemisia frigida and Cleistogenes songorica included absolute height, bunch density, bunch area, quantity and length of forage and reproductive branch, basal diameter of forage branch, root biomass (taproot, lateral root and total root biomass). The resource biomass allocation including aboveground (stem, leaf, and total biomass of stem & leaf) and root biomass (taproot, lateral root, and total root biomass).The nutrient allocation of Stipa breviflora, Artemisia frigida and Cleistogenes songorica were composed of total N and P contents, and stoichiometric rate included the characteristics of C∶N, C∶P and N∶P in each module.The main results were as following:(1) In the peak growing season(July and Auguest), with the stocking rate increasing, the absolute height and total root biomass of Stipa breviflora, Artemisia frigida and Cleistogenes songorica decreased, and branch density increased. Meanwhile, the forage branch density and specific root length of Stipa breviflora increased, and reproductive branch density, root number and root area index decreased. However, the forage branch density and indefinite root density of Artemisia frigida increased with the stocking rate increasing.(2) Grazing treatment negatively affected on the seed characteristics mature in June significantly(P<0.05), such as length, diameter, thousand seed weight, and awn weight, while had no significant influence on the seed characteristics mature in September (P>0.05). However, the peak value of seed awn occurred in LG plots involving both mature in June and in September. And the mature seed awn length, pubescence length, number, and density which mature in September were significantly higher than that of mature in June (P<0.05).(3) As for Stipa breviflora mature seed, the second awn knee point in June was significantly higher than the first awn knee point in September and significantly higher than the first awn knee point in June (P<0.05). And grazing treatment decreased the first and second awn knee point in June, but had no significant effect on the first awn knee point in September (P>0.05).(4) With the stocking rate increasing, the resource allocation proportion of aboveground, forage branch, green seed & awn resource allocation increased, and reproductive branch biomass allocation, mature seed and awn resource allocation proportion decreased; and the biomass allocation proportion from bunch, forage and reproductive branch to leaf increased, that of to stem decreased. The resource allocation proportion of forage branch was significantly higher than that of reproductive branch in bunch (P<0.05).(5) Grazing treatment accelerated the stem resource allocation of Artemisia frigida and Cleistogenes songorica, but diminished the leaf resource allocation, so the ratio of stem to leaf increased. Grazing treatment also reduced the taproot and lateral root resource allocation of Artemisia frigida, however, increased that of Cleistogenes songorica, and the peak value of lateral root resource allocation proportion appeared in LG plots, so LG accelerated the root growth.(6) As for Stipa breviflora, the total N content of each module were peaked in LG plots. And the total N and P content were highest in seed mature in June, the total N content in taproot was secondary, and total P content in reproductive branch was least. The total N and P in stem and leaf of forage branch were higher than that of reproductive branch, and that of stem were higher than that of leaf. The total N and P in seed and taproot were higher than that of awn and lateral root, respectively. As for Artemisia frigida, the total N and P content in leaf were higher than that of stem, and than that of taproot, and than that of lateral root. As for Cleistogenes songorica, the total N and P content in leaf were higher than that of stem, and than that of lateral root, and than that of taproot.(7) It was limited by N that the stem and leaf of forage branch and seed matured in June & September of Stipa breviflora. The stem of reproductive branch was limited by N in CK and LG plots, and limited by P in MG and HG plots, and the leaf was limited by P. The stem, taproot and lateral root of Artemisia frigida were limited by N, and the leaf was limited by P in CK, while limited by both N and P in LG, MG and HG plots. The stem and taproot of Cleistogenes songorica were limited by N, and the leaf was limited by N and P, and the lateral root was limited by P in CK, while limited by both N and P in LG, MG and HG plots.In a word, so far as reproductive resource allocation and nutrient allocation be concerned, LG was the feasible stocking rate in Inner Mongolia desert steppe. According to reproductive resource allocation pattern, the capability of pattern of Stipa breviflora was leaf>stem>caryopsis>root, aboveground>root, forage branch>reproductive branch, leaf and stem of forage branch>that of reproductive branch taproot higher>lateral root, respectively. The capability of the allocation pattern of Artemisia frigida and Cleistogenes songorica were both stem>taproot>leaf>lateral root and aboveground>root.The aboveground of Stipa breviflora was limited by N in CK, LG, and MG, and limited by P in HG. And the root was limited by P. The whole population of Stipa breviflora was limited by N and P in CK and LG plots, and limited by P in MG and HG plots. The whole population, aboveground and root of Artemisia frigida and Cleistogenes songorica were limited by N.更多还原