内蒙古高原半干旱地区草地早熟禾草坪水分耗散特征及其节水机制研究

No matter on the landscape or the function, turf is indispensable in urban landscaping. However, the frequency irrigation in the dry seasons makes the turf look like "wasting water" and limits its application severely in the semi-arid area of Inner Mongolia plateau.In order to ameliorate the arbitrary water timing and the water amount, we want to use the kentucky bluegrass which is common seen in Hohhot and Baotou, and to semulate different conservation levels by natural precipitation and controling irrigation. We are going to use the dissipation theory to study the dynamic law and the feature of kentucky bluegrass turf's cycle system during the turfgrass-soil-atmosphere. We also want to research the physiological water demand mechanism of the turf by the experiment of controling water and drought stress. By comparative analysising the dynamic model of turf's water consuming and physiological water demanding, we want to clear the model of the kentucky bluegrass turf's water gain or loss 's dynamic, especially the time of water deficient during the year, how long the time lasting and how strength the drought affect, the water requirement of the turf's physiological limit, the effective range of the turf's water circulation system and the least supplementary irrigation water. We want to provide theoretical basis of the turf's water-saving Irrigation System which can meet the normal requirements on the landscape and the function. And the result will influence the water using of the turf in our North country's semi-arid area deeply.

草坪是城市园林绿化中不可缺少的景观元素和功能要素，但草坪非雨季频繁灌溉造成的"耗水"之说严重限制了其在内蒙古高原半干旱地区的应用。为解决草坪灌溉时间的随意性和灌溉量的盲目性，拟针对呼包地区城市绿化中普遍使用草地早熟禾（Poa pratensis L.）建植的草坪，采用自然降水和控水方式进行互补试验，模拟不同养护水平，运用耗散理论系统研究自然降水条件下草地早熟禾草坪草-土壤-大气间水循环体系运行的动态规律和特征，利用控水抗旱耐力试验研究草坪草生理需水机理。以此通过草坪耗水动态模型和草坪草生理需水动态模型的比对分析，摸清并确定草地早熟禾草坪水分供需盈亏动态模式，尤其是全年亏水时间节点和时段、各节点持续时长与胁迫强度、草坪草生理极限需水量、草坪水循环体系需水量有效区间和经济灌溉补水量。旨为满足正常景观和功能要求的草坪制定节水灌溉制度提供理论依据，其成果对我国北方半干旱地区草坪节水将产生深远影响。

本研究立足内蒙古半干旱地区常见草地早熟禾（Poa pratensis L.）草坪，采用实地和盆栽方法，于2015年至2018年对不同修剪高度草坪及其不同土层土壤水分的蒸散规律进行了研究。主要成果：①在半干旱地区气候条件下，草地早熟禾草坪的蒸散量主要由草坪草蒸腾作用发生，坪床土壤的蒸发量因被草坪草完全覆盖而可以忽略不计；0～30cm层位的坪床土壤含水量与草坪蒸散量密切相关，0～15cm层位更为密切，30cm以下层位的影响明显减弱，直至45cm时消失；修剪高度对草坪蒸散量有比较大影响，随着修剪高度降低，草坪水分的蒸散量也降低，3cm处理显著低于其他高于3cm修剪高度的处理，12cm处理显著高于其他低于12cm修剪高度的处理。②本研究证实，灌溉量达到田间持水量80%时的维持草坪功能时长与100%田间持水量时的时长并无显著性差别，由此认为经济灌溉量应以达到田间持水量80%为上限；品种间因对亏水的敏感程度和忍耐程度不同，导致发生萎蔫的进程有很大差异，生理上耐受坪床土壤的含水量约为田间持水量的16.5%～20.6%，功能上耐受坪床土壤的含水量约为田间持水量的38.97%～60.95%，这也就是说生理有效水阈值的下限与经济灌溉量的下限不同；掌握了草坪草的需水机理和草坪的节水机制，则实施经济灌溉制与传统灌溉制相比可至少节约14.93%～17.87%的灌溉量。③在整个绿色期，草坪生态系统中的水循环往往入不敷出，主要靠灌溉补水维持草坪的功能显示，除雨季短暂连雨和非雨季零星散雨外，多数时间显示了灌溉的频率密集，年灌溉次数约24～26次，其中修剪高度12cm处理的草坪年灌溉次数高达29次；每次灌溉起始时间以丧失功能特征率达到50%时开始为好，这就是萎蔫的半衰期，此时的坪床土壤含水量即为经济灌溉量的下限。④影响草坪蒸散的因子很多，主要有地上枯落物、地上生物量、根层0～15cm土壤含水量及大气温度.