蒸散视角下护坡植被滴灌技术评价

为探明以复合型人造土壤为边坡种植土的植物蒸散对于高陡边坡生态恢复评价体系制定及水资源利用的重要意义,以黑麦草、高羊茅、早熟禾和“黑麦草+高羊茅+早熟禾”混合草种为研究对象,采用壤中滴灌技术,通过改进后的Penman-Monteith公式研究草本植物实际蒸散量与作物系数,以此评价壤中滴灌技术的生态效益。结果表明:高羊茅的作物实际蒸散量和作物系数最大,黑麦草其次,早熟禾最小,拟合的决定系数不小于0.847;养护初期各植物蒸散量相差较小,均保持在4.2 mm/d左右;养护结束后混合草种的蒸散量最大,早熟禾最小,分别约6.2、5.7 mm/d;养护前20 d,除早熟禾外,黑麦草、高羊茅、混合草种实际蒸散量均差异不显著,养护20 d后黑麦草、早熟禾、混合草种开始发生显著变化;30d后各草种蒸散量均差异不显著;4类草本植物蒸散量差值随时间递增,前期混合草种蒸散量低于黑麦草、高羊茅,后期有明显的提升,50 d起混合草种作物系数大于单草种作物系数。以30 d为界,30 d作物系数相近;生长初期的作物系数变幅最明显,且月增幅随时间呈下降趋势,但黑麦草和高羊茅的作物系数在任意时段均相近。边坡模型试验前期,以坡面喷灌方式灌溉的植物生态值较高,植物生长情况优于壤中滴灌方式,但自养护中期开始,壤中滴灌技术在生态效益上凸显优势,比坡面喷灌技术高出40.7%~1 444.0%的生态值。

Co-existence thresholds in the dynamics of the plant-herbivore interaction with Allee effect and harvest

In the interaction between plants and herbivores that live in the same ecosystem, understanding the conditions in which co-existence equilibrium occurs answers a major question in Ecology. In this interaction, plants serve as food for herbivores on the food chain. Then the livelihood of herbivores highly depends on the availability of food, in this case the availability of plants. Moreover, the abundance of the plant density alone does not guarantee the non-extinction of the herbivore population as they are assumed to reproduce sexually. With this motivation, in this paper a predator-prey mathematical model is reformulated such that the death rate of the herbivore population is dependent on the plant density and their emergence is also governed by the Allee effect. Using the mathematical theory of dynamical system, threshold conditions are obtained for the non-extinction of the herbivore population and a trapping region is obtained to ensure co-existence of the population. Moreover, it has been shown that the dynamics of the population is significantly sensitive to the feeding rate and the harvest rate of the herbivore population.