【作者】 徐炳成；

【导师】 山仑； 黄占斌；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2003， 博士

【摘要】 草地畜牧业是黄土高原半干旱地区的传统主导产业之一，也是发展该地区农村经济的基础。当前，在半干旱黄土丘陵区，作为发展畜牧业物质基础之一的人工草地建设相当薄弱，除干旱与社会经济因素外，一个很重要的原因就是对牧草在该地区不同立地条件下生态适应性的认识不足。通过比较不同牧草以及牧草与作物、灌木的生产力及生态适应性，阐明牧草在该地区生长发育的适宜程度与条件，对于明确牧草的地位与作用，以及该地区在西部开发中农业结构调整和生态环境建设中植物的合理布局具有重要指导意义。 选用该地区人工草地建设中具有代表性的栽培牧草（苜蓿、沙打旺和红豆草，无芒雀麦）、本土牧草栽培种（白羊草和达乌里胡枝子）和引种牧草柳枝稷，分别从种子萌发、苗期生长和田间生产力与水分利用等方面进行比较研究，并与不同立地条件下作物谷子及灌木沙棘和柠条的生产力与生态适应性进行比较，主要结果如下： 1 豆科牧草种子的发芽势高于禾本科；种子萌发阶段谷子的抗旱性＞柠条≥草木樨＞柳枝稷；水分胁迫的加剧使得柠条种子吸水速率降低而延长其发芽时间。 2 生长箱内在不同土壤水分下[高水（80％FC-14.72％）与高降、低水（50％FC-9.2％）与低降及降后复水]分别对单播的苜蓿和沙打旺；单播柳枝稷和白羊草；豆禾混播苜蓿／白羊草及沙打旺／柳枝稷苗期的水分利用与根冠生长进行比较： 2．1 土壤水分保持不变：苜蓿的生物量显著大于其它牧草，特别在高水条件下；与高水相比，沙打旺对低水的适应性强于苜蓿，白羊草强于柳枝稷；低水下沙打旺和柳枝稷混播的WUE_B（全部干重生物量）较单播提高；苜蓿／白羊草混播的WUE_B与单播苜蓿接近，混播时苜蓿的WUE_L（叶片水分利用效率）较单播下降，白羊草的WUE_L较单播提高。 2．2 土壤水分自然降低：豆科植物的土壤水分下降速率大于禾本科，说明在相同条件下豆科植物更易遭受严重干旱胁迫；高降过程中苜蓿维持高水势的土壤含水率最低，表明其耐旱性最强；高降过程中气孔关闭是导致植物叶片光合速率（Pn）降低的主要因素，而低降过程中Pn下降主要受非气孔因素作用；土壤水分降低后豆科植物根冠比增加幅度大于禾本科。 2．3 混播植物中苜蓿／白羊草当土壤水分保持不变特别是高水时，B_DW（全部生物量干重）和WUE_B均较沙打旺／柳枝稷高，当土壤水分变化时，其B_DW和WUE_B均低于后者。 2．4 低降后复水禾本科植物谷子、柳枝稷与白羊草在B_DW与WUE_B方面产生补偿效应，豆科植物沙打旺和苜蓿的均没有表现出补偿。 2．5 不同土壤水分下禾本科植物生物量根冠比变化较小，豆科植物随着土壤水分减少而增大，其中谷子的根冠比最小、WUE_B最高，柳枝稷的根冠比最大、WUE_B最低。 3 连续两年（2001-2002）在安塞对山地与川地不同植物生产力和水分利用研究表明：西北农林科技大学博士学位论文一半干旱黄土丘陵区牧草生产力与生态适应性研究（中文摘要） 3.1混播生产力形成取决于混播牧草产量组成和生长速率，柳枝樱与红豆草混播生产力形成呈双峰曲线，与沙打旺混播的生产力形成呈单一增长曲线。 3 .2受植物生产力和生长状况的影响，不同立地条件下不同植物的耗水量及其效率差别与变化较大。在川地，l年生植物中首稽与柳枝樱的wuEy（生产力水分利用效率）较高，但均低于谷子;2年生植物中单播豆科植物耗水量均高于禾本科，豆禾混播耗水量均高于单播各植物，效率因植物类型而异，其中柳枝樱/沙打旺混播耗水效率较单播高，而柳枝翟/红豆草混播较单播低，首蓓的耗水量较高但WUEy最低。在山地，谷子的wUEy两年均较高，首稽与无芒雀麦的最低，2年生柳枝樱/沙打旺混播耗水效率也较单播提高。 3.3总体分析表明，所有植物在川地生产力显著高于山地;植物耗水量和水分利用效率呈线性关系，在川地牧草的优势要强于谷子，山坡地则低于谷子。 3.4人工栽培可显著提高白羊草与达乌里胡枝子的生产力，高生产力也会导致土壤干燥化，其中胡枝子的生态适应性特征为加大生殖器官生物量分配（30一。%），而白羊草采用根茎与结实相结合生殖方式以及生活周期具有避旱性特征;柳枝樱的生产力在山地与谷子相当，在川地与沙打旺相当，影响其在l力地生产力提高的因素是土壤养分贫乏和种植密度较小;无芒雀麦与沙打旺混播可显著提高无芒雀麦生产力（是单播的5倍），对沙打旺生产力影响较小，不会导致上壤水分过快消耗和难以恢复。 3.5坡地沙棘生产力高于柠条，二者生产力均低于坡地人工草地;柠条的水分利用特征为高Pn、高Tr（蒸腾速率）和低wuEL且水分条件改善对其影响较小，沙棘为高Pn、低Tr和高WUEL并随水分条件改善而提高;沙棘对土壤水分的利用能力较柠条强;柠条的抗早适应性为形态御旱性（发达根系和早生结构）与高水势延迟脱水的耐早性，沙棘为形态（发达根系和旱生结构）以及生理御旱性（高wUEL）和低水势忍耐脱水耐早性，表明沙棘的抗旱适应方式比柠条更积极主动。 3，6测定不同植物在自然条件下光合生理与水势日变化特征，根据Pn、Tr与WUEL的大小将谷子与7种牧草植物分别划?更多还原

【Abstract】 Stockbreeding is one of the traditional dominant industries on Loess Plateau, and it is also the foundation to develop the country economy in Northwest China. In arid and semi-arid area such as the loess hilly-gully region, one of the material bases for the animal husbandry-the artificial grassland construction is quite weak. Besides drought and the social and economic factors, lack understanding of the eco-adaptability of grasses to the environment is one of the most important reasons. It is meaningful for agricultural framework regulation and plants layout in vegetation construction through comparing or contrasting the productivity and eco-adaptability among grasses, and with crops and shrubs in the area, to know which one is the most adaptive and what is most suitable condition for the grasses.The representational grasses species, which are the pulse family plants such as Astragalus adsurgens, Sainfoin (Onobrychis viciaefolia Scop.) and alfalfa (Medicago saliva), smooth brome grass (Bromus inermis) as the grass family, the native plants Lespedeza davurica and Old World bluestems (Bothriochloa ischaemum), which belong to he pulse and grass family respectively; and the introduced grass switchgrass (Panicum viegatum) were chosen, the seeds emergence and seedling growth and water use characteristics were compared in different water level, also their productivities and water use were compared with the shrubs Cargana korshinskii and seabuckthorn (Hippophae rhamnoides) and the crop foxtail millet(Setaria italica) in the field, the main results are as follows:1 The pulse plants’ seeds emergent faster than grasses; the drought tolerance order of seed emergence is foxtail millet>C. korshinskii>Melilotus a/6us>switchgrass (P. viegatum); the cumulative water that C. korshinskii seed absorbed decreases as the stress increases.2 Comparing the seedling root and aboveground growth and water use characteristics of alfalfa and A. adsurgens sole-cropped, switchgrass and B. ischaemum sole-cropped, the inter-copped alfalfa/B, ischaemum and switchgrass/ A. adsurgens in the growth chamber with one another under different water level treatments which are high water level(HW) (80%FC-14.72%) and drying from that, low water level (LWX50%FC-9.2%)and drying from that and then rewatered.2.1 Soil water kept stable: Alfalfa sole-cropped grows faster and has better WUEB (biomass dry weight water use efficiency) planted in HW than other treatments, the biomass and WUEB of A. adsurgens sole-cropped decrease less than alfalfa under LW as to HW, that’salso to B. ischaemwn than switchgrass; the WUEB of alfalfa and B. ischaemum inter-cropped under HW or LW is corresponded to alfalfa sole-cropped but can improve the latter’s WUEL (leaf water use efficiency), switchgrass/A. adsurgens has bigger WUEB than each sole-cropped under LW.2.2 Soil drying: The pulse plants’ soil water decreases more quickly than grasses when the irrigation ceased; when soil drying from the HW treatment, the threshold value of leaf potential drops steeply where the soil water content of alfalfa is the least means alfalfa is the most drought tolerant specie among them; the cause of photosynthetic rate (Pn) decrease from the HW is stomotal limitation, and that from the LW is non-stomotal limitation; the root/shoot increase extent of the pulse plants are bigger than the grass after the irrigation is ceased.2.3 Foxtail millet has the biggest WUEB under all treatments which mainly dues to its lowest stomotal conductance; only the grass family plants have compensation effects of biomass and WUEB after soil drying from LW and then rewatered; swithgrass seedling growth has some characteristics similar to the pulse plant such as high transpiration rate (Tr) and bigger root/shoot ratio.2.4 The switchgrass/ A. adsurgens inter-cropped has better adaptability to the soil water changes such as under LW or during soil drying comparing to HW than alfalfa/5, ischaemum.3 The productivity and soil water use of different plants were determined during 2001-20更多还原