Infiltration is a fundamental component of the rainfall-runoff process. It was characterized through the adjustment and comparison of the Smith-Parlange, Green-Amptd, Philip, Horton and Kostiakov equations, using simu...Infiltration is a fundamental component of the rainfall-runoff process. It was characterized through the adjustment and comparison of the Smith-Parlange, Green-Amptd, Philip, Horton and Kostiakov equations, using simulated rain in poorly developed soils from three geological formations and from different ages (Marino Fm., Mogotes Fm., quaternary cover). Trials with the rainfall simulator were run in piedmont areas west of the city of Mendoza. Adjustments were performed separately for each of the trials and globally for each surface cover. The adjustment was satisfactory when the observed and the simulated infiltration velocity curves were compared using lumped parameters. The Green-Amptd model exhibited the best behavior for the three covers, while the Smith-Parlange equation was the least accurate, al- though it had little dispersion in the prediction errors. The Kostiakov and Horton equations yielded satisfactory results in view of the fact that the development of the infiltration rate curve was simulated after the impoundment time was determined with the Green-Amptd formula. The Philip model is not consistent, with the exception of the results obtained for the Marino cover. In the post-calibration procedure the parameters showed no noticeable differences with respect to those obtained during calibration. In every case the relative squared error of the infiltration curve was very satisfactory, below 5%.展开更多
绿洲城市作为绿洲系统中承载人口集聚、经济活动与公共服务功能的核心空间单元,其扩张过程不仅受绿洲生态格局的制约,也在空间上推动了绿洲的演变。系统识别绿洲与绿洲城市的演变特征,是实现干旱区生态保护与空间开发协调发展的关键基...绿洲城市作为绿洲系统中承载人口集聚、经济活动与公共服务功能的核心空间单元,其扩张过程不仅受绿洲生态格局的制约,也在空间上推动了绿洲的演变。系统识别绿洲与绿洲城市的演变特征,是实现干旱区生态保护与空间开发协调发展的关键基础。首先识别2000—2023年中国西北干旱区绿洲与绿洲城市空间面积分布,分析绿洲与绿洲城市的空间演变趋势,然后构建绿洲城市协同指数(Oasis city synergy index,OCSI),定量评估研究区绿洲与绿洲城市的协同演变特征,并进一步探究绿洲城市的扩张模式。结果表明:(1)2000—2023年研究区绿洲与绿洲城市的面积持续增长,但绿洲斑块数量有所减少,绿洲呈现“大型化、集中化”趋势。(2)绿洲城市协同演变趋势分类和OCSI计算结果发现,8个地区为趋势相似型,23个地区为趋势相反型,且2000—2023年绿洲与绿洲城市的协同度逐渐增强。(3)基于绿洲与绿洲城市协同趋势与OCSI综合评价结果得到,填充扩张与边缘扩张模式的绿洲城市协同度普遍较高,而跳跃扩张与沿河扩张模式的绿洲城市由于扩张方式分散或依水线蔓延,OCSI波动大,协同度较低。研究结果识别并揭示了西北干旱区绿洲与绿洲城市之间的空间演变关系,可为缓解干旱区绿洲人地矛盾、推动可持续发展提供理论依据与决策支持。展开更多
Most ecological studies in North Africa reveal a process of continuous degradation of rangeland ecosystems as a result of overgrazing. This degradation appears across the decreasing of perennial grass diversity. Indee...Most ecological studies in North Africa reveal a process of continuous degradation of rangeland ecosystems as a result of overgrazing. This degradation appears across the decreasing of perennial grass diversity. Indeed, the majority of steppe ecosystems are characterized by a low density of perennial grass species at present. This study evaluated the effects of temperature and water limitation on the seed germination of Stipagrostis ciliata（Desf.） de Winter, a perennial grass species. The seeds were collected from the Bou Hedma Park, Sidi Bouzid Governorate, Central Tunisia. The thermal time and hydrothermal time models were used to describe the seed germination of S. ciliata under different water potentials and temperatures. The germination response of S. ciliata seeds in darkness was evaluated over a range of temperatures（15°C, 20°C, 25°C, 30°C and 35°C） and across a wide range of osmotic potentials（0.0, –0.2, –0.6, –1.2, –1.6 and –2.0 MPa） of the polyethylene glycol（PEG6000） solutions at each temperature level. Among the tested temperatures, 25°C was found to be the optimal temperature to the germination of S. ciliata seeds. The final germination percentage（75.2%） was obtained with distilled water. The progressive decrease of osmotic potential of the PEG6000 solutions inhibited the seed germination. However, the number of days to first germination was increased with a reduction of osmotic potential. A significant positive relationship was identified between final germination percentage of S. ciliata seeds and osmotic potential of the PEG6000 solutions, with R^2 ranging from 0.5678 to 0.8761. Furthermore, a high degree of congruency between predicted and observed germination time course curves was observed. In general, S. ciliata exhibits a significant adaptation capacity for water limitation and high temperature in arid ecosystems.展开更多
文摘Infiltration is a fundamental component of the rainfall-runoff process. It was characterized through the adjustment and comparison of the Smith-Parlange, Green-Amptd, Philip, Horton and Kostiakov equations, using simulated rain in poorly developed soils from three geological formations and from different ages (Marino Fm., Mogotes Fm., quaternary cover). Trials with the rainfall simulator were run in piedmont areas west of the city of Mendoza. Adjustments were performed separately for each of the trials and globally for each surface cover. The adjustment was satisfactory when the observed and the simulated infiltration velocity curves were compared using lumped parameters. The Green-Amptd model exhibited the best behavior for the three covers, while the Smith-Parlange equation was the least accurate, al- though it had little dispersion in the prediction errors. The Kostiakov and Horton equations yielded satisfactory results in view of the fact that the development of the infiltration rate curve was simulated after the impoundment time was determined with the Green-Amptd formula. The Philip model is not consistent, with the exception of the results obtained for the Marino cover. In the post-calibration procedure the parameters showed no noticeable differences with respect to those obtained during calibration. In every case the relative squared error of the infiltration curve was very satisfactory, below 5%.
文摘绿洲城市作为绿洲系统中承载人口集聚、经济活动与公共服务功能的核心空间单元,其扩张过程不仅受绿洲生态格局的制约,也在空间上推动了绿洲的演变。系统识别绿洲与绿洲城市的演变特征,是实现干旱区生态保护与空间开发协调发展的关键基础。首先识别2000—2023年中国西北干旱区绿洲与绿洲城市空间面积分布,分析绿洲与绿洲城市的空间演变趋势,然后构建绿洲城市协同指数(Oasis city synergy index,OCSI),定量评估研究区绿洲与绿洲城市的协同演变特征,并进一步探究绿洲城市的扩张模式。结果表明:(1)2000—2023年研究区绿洲与绿洲城市的面积持续增长,但绿洲斑块数量有所减少,绿洲呈现“大型化、集中化”趋势。(2)绿洲城市协同演变趋势分类和OCSI计算结果发现,8个地区为趋势相似型,23个地区为趋势相反型,且2000—2023年绿洲与绿洲城市的协同度逐渐增强。(3)基于绿洲与绿洲城市协同趋势与OCSI综合评价结果得到,填充扩张与边缘扩张模式的绿洲城市协同度普遍较高,而跳跃扩张与沿河扩张模式的绿洲城市由于扩张方式分散或依水线蔓延,OCSI波动大,协同度较低。研究结果识别并揭示了西北干旱区绿洲与绿洲城市之间的空间演变关系,可为缓解干旱区绿洲人地矛盾、推动可持续发展提供理论依据与决策支持。
基金supported by the Tunisian Ministry of Scientific Research, especially the arid lands program
文摘Most ecological studies in North Africa reveal a process of continuous degradation of rangeland ecosystems as a result of overgrazing. This degradation appears across the decreasing of perennial grass diversity. Indeed, the majority of steppe ecosystems are characterized by a low density of perennial grass species at present. This study evaluated the effects of temperature and water limitation on the seed germination of Stipagrostis ciliata（Desf.） de Winter, a perennial grass species. The seeds were collected from the Bou Hedma Park, Sidi Bouzid Governorate, Central Tunisia. The thermal time and hydrothermal time models were used to describe the seed germination of S. ciliata under different water potentials and temperatures. The germination response of S. ciliata seeds in darkness was evaluated over a range of temperatures（15°C, 20°C, 25°C, 30°C and 35°C） and across a wide range of osmotic potentials（0.0, –0.2, –0.6, –1.2, –1.6 and –2.0 MPa） of the polyethylene glycol（PEG6000） solutions at each temperature level. Among the tested temperatures, 25°C was found to be the optimal temperature to the germination of S. ciliata seeds. The final germination percentage（75.2%） was obtained with distilled water. The progressive decrease of osmotic potential of the PEG6000 solutions inhibited the seed germination. However, the number of days to first germination was increased with a reduction of osmotic potential. A significant positive relationship was identified between final germination percentage of S. ciliata seeds and osmotic potential of the PEG6000 solutions, with R^2 ranging from 0.5678 to 0.8761. Furthermore, a high degree of congruency between predicted and observed germination time course curves was observed. In general, S. ciliata exhibits a significant adaptation capacity for water limitation and high temperature in arid ecosystems.
