Evaluating Light Availability,Seagrass Biomass,and Productivity Using Hyperspectral Airborne Remote Sensing in Saint Joseph’s Bay,Florida

Seagrasses provide a number of critical ecosystem services, including habitat for numerous species, sediment stabilization, and shoreline protection. Ariel photography is a useful tool to estimate the areal extent of seagrasses, but recent innovations in radiometrically calibrated sensors and algorithm development have allowed identification of benthic types and retrieval of absolute density. This study demonstrates the quantitative ability of a high spatial resolution (1 m) airborne hyperspectral sensor (3.2 nm bandwidth) in the complex coastal waters of Saint Joseph’s Bay (SJB). Several benthic types were distinguished, including submerged and floating aquatic vegetation, benthic red algae, bare sand, and optically deep water. A total of 23.6 km² of benthic vegetation was detected, indicating no dramatic change in vegetation area over the past 30 years. SJB supported high seagrass density at depths shallower than 2 m with an average leaf area index of 2.0?±?0.6 m² m^?2. Annual seagrass production in the bay was 13,570 t C year^?1 and represented 41 % of total marine primary production. The effects of coarser spatial resolution were investigated and found to reduce biomass retrievals, underestimate productivity, and alter patch size statistics. Although data requirements for this approach are considerable, water column optical modeling may reduce the in situ requirements and facilitate the transition of this technique to routine monitoring efforts. The ability to quantify not just areal extent but also productivity of a seagrass meadow in optically complex coastal waters can provide information on the capacity of these environments to support marine food webs.     

The practical use of simplicity in developing ground water models

The advantages of starting with simple models and building complexity slowly can be significant in the development of ground water models. In many circumstances, simpler models are characterized by fewer defined parameters and shorter execution times. In this work, the number of parameters is used as the primary measure of simplicity and complexity; the advantages of shorter execution times also are considered. The ideas are presented in the context of constructing ground water models but are applicable to many fields. Simplicity first is put in perspective as part of the entire modeling process using 14 guidelines for effective model calibration. It is noted that neither very simple nor very complex models generally produce the most accurate predictions and that determining the appropriate level of complexity is an ill-defined process. It is suggested that a thorough evaluation of observation errors is essential to model development. Finally, specific ways are discussed to design useful ground water models that have fewer parameters and shorter execution times.     

阿尔金断裂带附近地壳结构的接收函数成像及其地球动力学意义

利用中法1995年布设在跨过阿尔金断裂剖面上的18个流动三分量地震台站记录到的近5个月的天然地震记录,经筛选得到533个高质量接收函数。通过速度分析和接收函数成像处理,得到了阿尔金断裂附近地壳结构的清晰图像。塔里木盆地的Moho界面非常清楚,近水平地位于~44km深度上。该界面以低缓的角度一直向南延伸到了阿尔金断裂附近的~70km的深度。阿尔金断裂以南柴达木盆地下面的Moho界面也十分清楚,近水平地位于~55km的深度上,在阿尔金断裂附近存在向上挠曲,并抬升到了~45km的深度上。在阿尔金断裂下方,Moho界面存在~15km的错断。塔里木盆地Moho之下还存在另一个震相,我们解释为沉积层多次波与可能来自Hales间断面转换波的复合震相。接收函数成像结果表明阿尔金断裂是一个超壳的岩石圈断裂,具有比较直立的产状和很狭窄的剪切变形带。根据这些结果,我们推测塔里木的下地壳可能要比柴达木的下地壳更硬,柴达木地壳增厚的原因可以部分归结于它有一个相对弱的下地壳,青藏高原隆升没有扩展到塔里木盆地是因为塔里木盆地具有更刚性的下地壳和岩石圈地幔。高原北部地壳变形应该是所谓青藏高原隆升的“硬”变形模式(Tapponnieretal...     

Geoarchaeology and late glacial landscapes in the western lake superior region,Central North America

The transition from full glacial to interglacial conditions along the southern margin of the Laurentide ice sheet resulted in dramatic changes in landscapes and biotic habitats. Strata and landforms resulting from the Wisconsin Episode of glaciation in the area directly west of Lake Superior indicate a context for late Pleistocene biota (including human populations) connected to ice margins, proglacial lakes, and postglacial drainage systems. Late Glacial landscape features that have the potential for revealing the presence of Paleoindian artifacts include abandoned shorelines of proglacial lakes in the Superior and Agassiz basins and interior drainages on deglaciated terrains. The linkage between Late Pleistocene human populations and Rancholabrean fauna has yet to be demonstrated in the western Lake Superior region, although isolated remains of mammoth ( Mammuthus) have been documented, as well as fluted points assigned to Clovis, Folsom, and Holcombe‐like artifact forms. Agate Basin and Hell Gap (Plano‐type) artifacts also imply the presence of human groups in Late Glacial landscapes associated with the Agassiz and Superior basins. © 2007 Wiley Periodicals, Inc.