Chlorophylla of size-fractionated phytoplankton at a temporary hypersaline lake     

F. Guerrero  M. C. Castro 《International Journal of Salt Lake Research》1996,5(3):253-260

The size-fractionated distribution of chlorophylla was studied in a temporary hypersaline lake situated in the south of Spain during an annual hydrological cycle characterized by low levels of rainfall. The contribution of each size class to the total chlorophylla concentration indicates that ultraplankton (size class <5m) was the most important fraction of phytoplankton biomass during this year.  相似文献   

热气球飞越泰山气象条件分析及预报     

刘清洵 《气象》1998,24(12):51-54

分析了热气球飞行的气象条件及泰山对热气球飞行的影响。利用１９８８－１９９５年９－１０月历史资料,对适宜热气球飞越泰山的气象条件进行了统计分析,在总结天气形势特征的基础上,针对热气球飞越泰山受诸多气象要素影响的特点,分析素选取相关性较好的因子,分别建立天空状况,低空风向,地面风速预报方程,最后制作综合预报。经１９９６年,１９９７年９－１０月试报效果较好。  相似文献   

低层不稳定大气边界层中的地形阻力   总被引：5，自引：2，他引：3  

刘辉志  洪钟祥  桑建国 《大气科学》1998,22(6):881-895

采用两层大气模式,通过求解线性化大气动力学—热力学方程组,得到在上层稳定层结覆盖的不稳定大气边界层中,简单三维地形引起的地形波及其波动阻力的解析表达式。讨论了地形及大气条件对地形波及波动阻力的影响。结果表明:即使在大气低层为不稳定边界层时,三维地形引起的波动在大气动量平衡中仍可起明显作用。  相似文献   

The influence of heat conduction on evaporation from sunken pans in hot, dry environment     

I. M. Oroud 《Journal of Hydrology》1998,210(1-4):1-10

Lateral heat conduction across a large circular sunken pan located in a hot, dry environment is evaluated using a numerical procedure. Heat flow across the sunken pan–adjacent soil boundary is calculated using a two-dimensional soil plane. Calculations show that a large temperature differential across the pan–substrate boundary develops during the entire diurnal cycle during January and July, leading to consistently positive heat flow from the soil towards the sunken pan. Heat conduction across the pan–substrate boundary represents 10 and 34% of net radiation over the sunken pan during July and January, respectively. This additional heat source, which is not available for shallow lakes, increases annual evaporation from the sunken pan by about 5–8% in July and January, respectively. In hot arid environments, a sunken pan will overestimate evaporation from a nearby shallow lake/dam due to a larger surface roughness and consistently positive conduction heat flow across the pan–substrate boundary.  相似文献   

苏南孔山地区人为坡面草本植被的自然恢复     

张振克 《山地学报》1998,(3)

发现苏南孔山地区小型人为裸露坡面草本植被自然恢复过程受地形、母质、气候和周围植被覆盖等因素的影响,据此提出我国南方山地人为裸露坡面水土流失的防治要坚持边开发边治理原则,最大程度地降低人为造成的水土流失．  相似文献   

Benthic macroinvertebrates of the northern Caspian Sea during recent rises in water-level     

L.V. Malinovskaja  A.A. Filippov  V.F. Osadchikh  N.V. Aladin 《International Journal of Salt Lake Research》1998,7(3):211-233

Data on benthic macroinvertebrates of the northern Caspian Sea in 1980–1991 were collected by the Caspian Fishery Research Institute. During the initial period of the water-level rise, the main trends in benthic macroinvertebrates were increases in the biomass of the main groups and decreases in the relative abundance of species of Mediterranean origin. There was no significant alteration in species composition. The increased abundance was due to improved trophic conditions and a decrease in the numbers of benthos-feeding fish. Some decrease in the relative abundance of species of marine origin was related to a decrease in water salinity.  相似文献   

Anthropogenic perturbations to the trophic structure in a permanent hypersaline shallow lake: La Salada de Chiprana (north-eastern Spain)   总被引：1，自引：0，他引：1  

P. Díaz  M.C. Gerrero  P. Alcorlo  A. Baltanás  M. Florín  C. Montes 《International Journal of Salt Lake Research》1998,7(3):187-210

The changes in the trophic state in the Salada de Chiprana (north-eastern Spain) over two quite different seasonal cycles (1989, 1994/95) were studied. During the former cycle, the lake was permanently stratified, and was biogenically meromictic, and in the latter, showed no apparent stratification. The main variables related to the physico-chemical changes observed can be attributed to the effect caused by the increase in the nutrient loading. The large amounts of nutrients (total-N and total-P) and organic matter are due to the use of the lake as a reservoir for water discharged from irrigation. Two remarkable effects of the change are the permanent mixing of the water column and the immobilization of phosphorus in the form of ionic species and solid phases that are not available to the biota especially primary producers (phytoplankton, periphyton, microbial mats). The results of the present study emphasize the fragility of (hyper) saline ecosystems to anthropogenic disturbances such as increases in freshwater inflow and nutrient inputs. Likewise, the study reveals the failure of conservation criteria that have been used to manage this lake, especially those which refer to the control of freshwater, nutrient-rich influents.  相似文献   

Changes in the structure and function of biological communities in the Aral Sea, with particular reference to the northern part (Small Aral Sea), 1985--1994: A review     

N.V. Aladin  A.A. Filippov  I.S. Plotnikov  M.I. Orlova  W.D. Williams 《International Journal of Salt Lake Research》1998,7(4):301-343

The construction of a dam between the Small and Large Aral Sea in 1993 has had an effect on biological communities. From field and laboratory investigations and analysis of the literature, the structure and function of the main plant and animal communities in the northern (Small) Aral Sea are described and discussed, first, for the period before 1985, and, second, between 1985 and 1994. A prognosis for future changes is provided.  相似文献   

Utilization and sustainable development of island mountains in China     

张耀光  杨荫凯 《中国地理科学(英文版)》1998,8(1):58-66

ＵＴＩＬＩＺＡＴＩＯＮＡＮＤＳＵＳＴＡＩＮＡＢＬＥＤＥＶＥＬＯＰＭＥＮＴＯＦＩＳＬＡＮＤＭＯＵＮＴＡＩＮＳＩＮＣＨＩＮＡ①ＺｈａｎｇＹａｏｇｕａｎｇ（张耀光）ＹａｎｇＹｉｎｋａｉ（杨荫凯）ＩｎｓｔｉｔｕｔｅｏｆＭａｒｉｎｅＲｅｓｏｕｒｃｅｓ,Ｌｉａｏ...  相似文献   

A weighted-averaging regression and calibration model for inferring lakewater salinity from fossil diatom assemblages in saline lakes of the Vestfold Hills: a new tool for interpreting Holocene lake histories in Antarctica     

D. Roberts  A. McMinn 《Journal of Paleolimnology》1998,19(2):99-113

The relationship between surface sediment diatom assemblages and measured limnological variables in thirty-three coastal Antarctic lakes from the Vestfold Hills was examined by constructing a diatom-water chemistry dataset. Previous analysis of this dataset by canonical correspondence analysis revealed that salinity accounted for a significant amount of the variation in the distribution of the diatom assemblages. Weighted-averaging regression and calibration of this diatom-salinity relationship was used to establish a transfer function for the reconstruction of past lakewater salinity from fossil diatom assemblages. Weighted-averaging regression and calibration with classical deshrinking provided the best model for salinity reconstructions and this was applied to the fossil diatom assemblages from one of the saline lakes in the Vestfold Hills in order to assess its potential for palaeosalinity and palaeoclimate reconstruction.  相似文献