The progress on remote sensing technology in identifying tropical forest degradation: a synthesis of the present knowledge and future perspectives

Since the launch of the first satellite in 1972, ecologists have been equipped with new tools to address the degradation of tropical forests, previously limited by field-based methods. This article is a review of the state of remote sensing technology in characterizing the degradation of tropical forest. The factors responsible for the structural and functional degradation of the tropical forest and its likely impacts are described in view of generating remote sensing based inputs. In order to assess the degradation and utility of geo-informatics tools, 32 parameters are identified. The research developments at different levels of information extraction from the historic to recent periods are elaborated, and future challenges are predicted. The article concludes that an additional momentum of research is required to answer many unresolved questions of tropical forest degradation.     

A diagnostic model using ashfall data to determine eruption characteristic and atmospheric conditions during a major volcanic event

A model is developed for estimating location of a volcano relative to sample points in an associated ashfall, cloud height during eruption, and mean wind velocity during ash deposition. The ash deposit must cover a large area and have an elongate axis. The model appears to be applicable both to recent and to unobserved ashfalls in the past, provided adequate and representative ash samples are available. The opportunity to test the diagnostic model on volcanic ashfalls is limited by sparsity of the necessary input data. From more than 20 ashfalls described in the literature, the 1947 Hekla (Iceland) eruption is the only one which includes suitable particle size analyses taken from samples related to a well-defined axis. The application of the model to the Hekla ashfall is discussed.     

A. Programmable device for simulation of tidal flux

An apparatus is described which permits precise, versatile control of simulated tidal flux in laboratory microcosms. A key component of the system, a programmable electronic control unit, can closely imitate any natural tidal function and is readily adaptable to other experimental applications that utilize timed switching capability. The programmable control unit is also cheaper and easier to operate than computer-based systems.     

柴达木盆地北缘古生代超高压带中花岗质岩浆作用

祁连南缘古生代超高压变质带 (榴辉岩年龄为 4 6 6～ 4 95 Ma)上一套中高级变质岩系 (达肯大坂片麻岩 )中存在三类花岗岩组合 : 类 :石英二长闪长岩 -花岗闪长岩 -二长花岗岩 , 类 :二长花岗岩 -二云母花岗岩-含白云母花岗岩 -正长花岗岩 , 类 :花岗闪长岩 -二长花岗岩 -黑云母花岗岩。 类岩石组合中的二长花岗岩锆石SHRIMP年龄为 4 73Ma, 类岩石组合中的正长花岗岩锆石 SHRIMP年龄为 4 4 6 Ma, 类岩石组合中的二长花岗岩锆石 SHRIMP年龄为 397Ma。从三类花岗岩组合的组成矿物来看 , 类和 类的矿物组合主要为斜长石、角闪石、石英、碱性长石、黑云母 , 类的矿物组合为钾长石、石英、白云母、黑云母、斜长石 ;从岩石地球化学特征上看 , 类和 类花岗岩为 型花岗岩 ,岩石的 Si O2 =6 1%～ 6 9% ,Na2 O/ K2 O>1,ANK<1,δEu=0 .7～ 1.0 ; 类花岗岩为 S型花岗岩 ,岩石的 Si O2 =70 %～ 76 % ,Na2 O/ K2 O<1,ANK>1,δEu=0 .1～ 0 .3;从构造环境上看 , 类花岗岩形成于岛弧环境或活动大陆边缘 , 类花岗岩形成于同碰撞 , 类花岗岩形成于碰撞后。结合区域地质特征 ,我们认为 ,早奥陶世 ,南祁连洋板块向北俯冲于祁连陆块之下 ,规模不大的南祁连洋很快闭合 ,但俯冲下去的大洋板块仍拖动柴达木陆块继续俯冲 ,俯冲     

Holocene paleoenvironmental changes inferred from diatom assemblages in sediments of Kusawa Lake, Yukon Territory, Canada

The southwest Yukon Territory, Canada, is an important region for recovering sensitive records of Holocene paleoclimatic change. More information is needed, however, to constrain the timing of the major Holocene climatic transitions, and to understand associated impacts on different ecosystems. For example, paleolimnological studies have focused on small lakes and ponds, but the history of large lakes has received little study. We analyzed diatom assemblages, species richness, valve concentrations, and biogenic silica, in the sediments of Kusawa Lake (60°16.5'N; 136°10.9'W; 671 m a.s.l.) to reconstruct the responses of this large (surface area = 142 km²), deep (Z_max = 135 m) freshwater ecosystem to Holocene climatic transitions. Diatoms colonized the lake soon after ice retreat, around 11,000 cal yr BP; assemblages throughout the record were dominated by planktonic types. Diatom concentrations and biogenic silica were high during the Holocene Thermal Maximum between 10,700 and 7300 cal yr BP, then began to decrease in response to cooling associated with orbitally driven reductions in insolation. Diatom assemblages shifted towards taxa with lower surface water temperature optima after 8300 cal yr BP, perhaps in response to abrupt and progressive cooling. Our study confirms that diatom assemblages in large lakes are sensitive to regional-scale paleoclimatic changes.     

Aussiedler migration and its impact on Braşov's ethnic German population and built environment

The expression of different ethnic identities in the landscape is a product of the creation, destruction and preservation of the built environment. This may illustrate the changing processes over the evolution of a landscape. In the case of Braşov, Romania, it is possible to see in the urban landscape a reflection of the changing nature of the relationship between the ethnic German and Romanian populations, and the German and Romanian governments. This paper will demonstrate the persistence of ethnic German culture in the built environment and social organisation of Braşov in spite of the exodus of the ethnic German population. This revised version was published online in July 2006 with corrections to the Cover Date.     

Source partitioning of anthropogenic groundwater nitrogen in a mixed-use landscape,Tutuila, American Samoa

This study presents a modeling framework for quantifying human impacts and for partitioning the sources of contamination related to water quality in the mixed-use landscape of a small tropical volcanic island. On Tutuila, the main island of American Samoa, production wells in the most populated region (the Tafuna-Leone Plain) produce most of the island’s drinking water. However, much of this water has been deemed unsafe to drink since 2009. Tutuila has three predominant anthropogenic non-point-groundwater-pollution sources of concern: on-site disposal systems (OSDS), agricultural chemicals, and pig manure. These sources are broadly distributed throughout the landscape and are located near many drinking-water wells. Water quality analyses show a link between elevated levels of total dissolved groundwater nitrogen (TN) and areas with high non-point-source pollution density, suggesting that TN can be used as a tracer of groundwater contamination from these sources. The modeling framework used in this study integrates land-use information, hydrological data, and water quality analyses with nitrogen loading and transport models. The approach utilizes a numerical groundwater flow model, a nitrogen-loading model, and a multi-species contaminant transport model. Nitrogen from each source is modeled as an independent component in order to trace the impact from individual land-use activities. Model results are calibrated and validated with dissolved groundwater TN concentrations and inorganic δ¹⁵N values, respectively. Results indicate that OSDS contribute significantly more TN to Tutuila’s aquifers than other sources, and thus should be prioritized in future water-quality management efforts.     

Marine inundated archaeological sites and paleofluvial systems: examples from a karst-controlled continental shelf setting in Apalachee Bay,Northeastern Gulf of Mexico

Underwater geoarchaeological research in Apalachee Bay, in the northeastern Gulf of Mexico off northwest Florida, has enabled the reconstruction of portions of the karst-controlled paleodrainage system, the discovery of several inundated prehistoric archaeological sites, and the exposure of sediments accumulated during the drowning of the continental shelf. Diagnostic artifacts discovered at the sites included chipped stone tools and debitage indicating Paleoindian, Early Archaic, and Middle Archaic occupation. A geoarchaeological model using terrestrial analogs was used to locate and investigate inundated sites. Methods employed include seismic profiling, vibracoring, diver tow surveys, diver collection transects, and induction dredge excavations. We document evidence for sea-level rise, related environmental succession and site formation processes for indundated prehistoric sites in the Apalachee Bay region from approximately 8000 to 6000 yr B.P. © 1997 John Wiley & Sons, Inc.