Tropical deforestation and habitat fragmentation in the Amazon: satellite data from 1978 to 1988

Landsat satellite imagery covering the entire forested portion of the Brazilian Amazon Basin was used to measure, for 1978 and 1988, deforestation, fragmented forest, defined as areas less than 100 square kilometers surrounded by deforestation, and edge effects of 1 kilometer into forest from adjacent areas of deforestation. Tropical deforestation increased from 78,000 square kilometers in 1978 to 230,000 square kilometers in 1988 while tropical forest habitat, severely affected with respect to biological diversity, increased from 208,000 to 588,000 square kilometers. Although this rate of deforestation is lower than previous estimates, the effect on biological diversity is greater.     

Land-use allocation protects the Peruvian Amazon

Disturbance and deforestation have profound ecological and socioeconomic effects on tropical forests, but their diffuse patterns are difficult to detect and quantify at regional scales. We expanded the Carnegie forest damage detection system to show that, between 1999 and 2005, disturbance and deforestation rates throughout the Peruvian Amazon averaged 632 square kilometers per year and 645 square kilometers per year, respectively. However, only 1 to 2% occurred within natural protected areas, indigenous territories contained only 11% of the forest disturbances and 9% of the deforestation, and recent forest concessions effectively protected against clear-cutting. Although the region shows recent increases in disturbance and deforestation rates and leakage into forests surrounding concession areas, land-use policy and remoteness are serving to protect the Peruvian Amazon.     

Selective logging in the Brazilian Amazon

Amazon deforestation has been measured by remote sensing for three decades. In comparison, selective logging has been mostly invisible to satellites. We developed a large-scale, high-resolution, automated remote-sensing analysis of selective logging in the top five timber-producing states of the Brazilian Amazon. Logged areas ranged from 12,075 to 19,823 square kilometers per year (+/-14%) between 1999 and 2002, equivalent to 60 to 123% of previously reported deforestation area. Up to 1200 square kilometers per year of logging were observed on conservation lands. Each year, 27 million to 50 million cubic meters of wood were extracted, and a gross flux of approximately 0.1 billion metric tons of carbon was destined for release to the atmosphere by logging.     

The Discovery of America: The first Americans may have swept the Western Hemisphere and decimated its fauna within 1000 years

I propose a new scenario for the discovery of America. By analogy with other successful animal invasions, one may assume that the discovery of the New World triggered a human population explosion. The invading hunters attained their highest population density along a front that swept from Canada to the Gulf of Mexico in 350 years, and on to the tip of South America in roughly 1000 years. A sharp drop in human population soon followed as major prey animals declined to extinction. Possible values for the model include an average frontal depth of 160 kilometers, an average population density of 0.4 person per square kilometer on the front and of 0.04 person per square kilometer behind the front, and an average rate of frontal advance of 16 kilometers per year. For the first two centuries the maximum rate of growth may have equaled the historic maximum of 3.4 percent annually. During the episode of faunal extinctions, the population of North America need not have exceeded 600,000 people at any one time. The model generates a population sufficiently large to overkill a biomass of Pleistocene large animals averaging 9 metric tons per square kilometer (50 animal units per section) or 2.3 x 10(8) metric tons in the hemisphere. It requires that on the front one person in four destroy one animal unit (450 kilograms) per week, or 26 percent of the biomass of an average section in 1 year in any one region. Extinction would occur within a decade. There was insufficient time for the fauna to learn defensive behaviors, or for more than a few kill sites to be buried and preserved for the archeologist. Should the model survive future findings, it will mean that the extinction chronology of the Pleistocene megafauna can be used to map the spread of Homo sapiens throughout the New World.     

珠江三角洲冲积平原土壤镉高含量区形成原因

通过现场采样及室内分析方法,研究了珠江三角洲冲积平原土壤Cd高含量区形成的原因。调查发现,在西江和北江冲积平原存在Cd的高含量分布区。Cd高含量区仅分布于第四纪海陆交互相,从地表至深部含量变化不大,为珠江三角洲形成过程中,富含Cd的西江和北江冲积物质在珠江三角洲沉积而成。Cd高含量区空间分布特征明显,控制因素显著,属于由地质作用引起。这一结论与多数研究者认为是人为因素引起的具有根本差别。     

Earthquake-caused landslides: a major disturbance to tropical forests

Earthquakes occasionally denude large areas of tropical forest: for example, 54 square kilometers in Panama in 1976 and 130 square kilometers in New Guinea in 1935. Earthquake rates in New Guinea, but not in Panama, are sufficiently high so that substantial areas of disturbed, nonclimax forest may accumulate. In New Guinea, earthquake-caused landslides are as important as tree falls in the disturbance regime.     

近30年铁岭县地表覆盖时空变化特征

地表覆盖变化已成为全球变化研究的核心领域和热点问题之一。以Landsat系列卫星影像为主要数据源,提取铁岭县1990-2020年地表覆盖变化图斑,构建土地利用变化转移矩阵,对铁岭县地表覆盖变化情况进行时空分析,识别土地利用变化热点区域。结果表明：近30年铁岭县地表覆盖面积呈现 “四增两减”特征,其中增加和减少最多的地表覆盖类型分别是建设用地(增加了85.27km2)和林地(减少105.39km2),其他几种类型动态变化不明显。近30年区域地表覆盖类型受人类活动的影响较为明显,对于揭示地表覆盖变化规律和可持续发展具有重要意义。     

福建运材汽车燃料经济性评价指标的研究

本文分析研究了运材汽车燃料经济性评价指标及其主要影响因子,在道路试验和理论分析的基础上提出了“百吨公里”新油耗指标和计算式,并与旧指标相比较。单车《百吨公里》油耗指标为Qv=10.75kg/(100km·t),拖挂为Qv=4.82kg/(100km·t);而原指标各为Qs=21.5kg/100km和Qs=29.5kg/100km。显然,新指标具有明显的经济性和生产性,有利于提高企业管理水平和生产能力。计算式可用来进行不同等级林区道路的油耗计算;提出了一些方法措施,以提高新指标的里程利用系数和载重利用系数,降低燃油耗量,节约能源。     

Destruction of Pacific Corals by the Sea Star Acanthaster planci

Acanthaster planci, a coral predator, is undergoing a population explosion in many areas of the Pacific Ocean. Data on feeding rates, population movements, and stages of infestation were collected along coral reefs of Guam and Palau. Direct observations on destruction of Guam's coral reefs indicate that narrow, fringing reefs may be killed as rapidly as 1 kilometer per month. In a 2(1/2)-year period, 90 percent of the coral was killed along 38 kilometers of Guam's shoreline.     

福建酸竹低效林的改造效应

对福建省建瓯市野生福建酸竹低效林实施松土、施肥等低效改造抚育措施,比较分析改造前后竹林立竹密度、地径、林龄结构及笋产量的变化情况,结果表明:与对照区相比,2007年改造区竹林立竹密度增加5021株.km-2,平均地径提高0.3 cm,Ⅰ-Ⅲ度竹所占比例提高42%,产笋量增加433 kg.km-2,经济效益明显,低效改造基本成功。     

基于meff指数的多尺度景观破碎化空间特征研究——以宁国市为例

采用CBC算法计算的m_(eff)指数,基于GIS技术,以宁国市、乡镇、1 km~2格网3种不同空间尺度区域为报告单元,选取城市建设区域、道路、农田、采矿区、采伐区、水体6类景观破碎因子组成景观破碎几何量度,研究宁国市景观破碎空间分布特征。结果表明,基于3种报告单元的m_(eff)值为0~422.92 km~2;宁国市景观破碎空间分布特征明显,破碎程度较重区域空间上呈"人"字形分布,城区破碎化水平最高,市域西北部、南部部分地区破碎程度相对较轻。     

Pleistocene glaciation on st. George, pribilof islands

A small ice cap (covering about 12 square kilometers) and at least two-probably four-cirque glaciers (each covering less than 1 square kilometer) occurred on St. George Island, Pribilof Islands, probably during the Illinoian; Glaciation. Snowbanks persisted during a later cold cycle, probably during the Wisconsin Glaciation, with no glaciers existing. We found no evidence of glaciation on other Pribilof islands.     

A budget for continental growth and denudation

Oceanic crustal material on a global scale is re-created every 110 million years. From the data presented it is inferred that potential sialic material is formed at a rate of about 1.35 cubic kilometers per year, including hemipelagic volcanic sediments that accumulate at a rate of about 0.05 cubic kilometer per year. It is estimated that the influx of 1.65 cubic kilometers per year of terrigenous and biogenic sediment is deposited on the deep ocean, and this represents continental denudation. Because all this material is brought into a subduction zone, continental accretion rates, which could include all this material, may be as high as 3.0 cubic kilometers per year with a potential net growth for continents of 1.35 cubic kilometers per year.     

Accelerated uplift and magmatic intrusion of the Yellowstone caldera, 2004 to 2006

The Yellowstone caldera began a rapid episode of ground uplift in mid-2004, revealed by Global Positioning System and interferometric synthetic aperture radar measurements, at rates up to 7 centimeters per year, which is over three times faster than previously observed inflation rates. Source modeling of the deformation data suggests an expanding volcanic sill of approximately 1200 square kilometers at a 10-kilometer depth beneath the caldera, coincident with the top of a seismically imaged crustal magma chamber. The modeled rate of source volume increase is 0.1 cubic kilometer per year, similar to the amount of magma intrusion required to supply the observed high heat flow of the caldera. This evidence suggests magma recharge as the main mechanism for the accelerated uplift, although pressurization of magmatic fluids cannot be ruled out.     

太湖地区农村生活垃圾管理模式与处理技术方式探讨

为探索太湖地区区域农村生活垃圾可行的管理模式,依托宜兴市大浦镇2个行政村示范运行的生活垃圾收集系统,对该区域农村生活垃圾的产生状况和管理背景进行调查,并结合当地可能的物流消纳去向对其处理技术方式和管理模式进行了分析。结果表明,研究区域的农村现状生活垃圾产生率为0.15～0.27kg·人-·1d-1,产生密度为0.17t·km-·2d-1,均远低于周边城市。生活垃圾组成以可堆肥物和废品为主,废品类垃圾中可通过现有回收市场分流的占17%。农村生活垃圾不适合填埋和焚烧处理,宜通过源头分拣(废品回收)和后续的堆肥农肥化,利用现有物流容量条件消纳。生活垃圾收集成本为3.4元·户-·1月-1,可利用村民的支付意愿筹集平衡;后续处理成本为455元·t-(1农肥),有可能通过产品出售平衡,使处理设施的企业化运行具有可行性。     

NEAR at eros: imaging and spectral results

Eros is a very elongated (34 kilometers by 11 kilometers by 11 kilometers) asteroid, most of the surface of which is saturated with craters smaller than 1 kilometer in diameter. The largest crater is 5.5 kilometers across, but there is a 10-kilometer saddle-like depression with attributes of a large degraded crater. Surface lineations, both grooves and ridges, are prominent on Eros; some probably exploit planes of weakness produced by collisions on Eros and/or its parent body. Ejecta blocks (30 to 100 meters across) are abundant but not uniformly distributed over the surface. Albedo variations are restricted to the inner walls of certain craters and may be related to downslope movement of regolith. On scales of 200 meters to 1 kilometer, Eros is more bland in terms of color variations than Gaspra or Ida. Spectra (800 to 2500 nanometers) are consistent with an ordinary chondrite composition for which the measured mean density of 2.67 +/- 0.1 grams per cubic centimeter implies internal porosities ranging from about 10 to 30 percent.     

Free-drifting icebergs: hot spots of chemical and biological enrichment in the Weddell Sea

The proliferation of icebergs from Antarctica over the past decade has raised questions about their potential impact on the surrounding pelagic ecosystem. Two free-drifting icebergs, 0.1 and 30.8 square kilometers in aerial surface area, and the surrounding waters were sampled in the northwest Weddell Sea during austral spring 2005. There was substantial enrichment of terrigenous material, and there were high concentrations of chlorophyll, krill, and seabirds surrounding each iceberg, extending out to a radial distance of approximately 3.7 kilometers. Extrapolating these results to all icebergs in the same size range, with the use of iceberg population estimates from satellite surveys, indicates that they similarly affect 39% of the surface ocean in this region. These results suggest that free-drifting icebergs can substantially affect the pelagic ecosystem of the Southern Ocean and can serve as areas of enhanced production and sequestration of organic carbon to the deep sea.     

Wadi howar: paleoclimatic evidence from an extinct river system in the southeastern sahara

Field research into the climatic history and shifting of the East Saharan desert has furnished evidence that during Quaternary time the present extremely arid western part of Upper Nubia (northern Sudan)was temporarily linked to the Nile by way of a hitherto unknown 400 kilometer long tributary. From about 9500 to 4500 years ago, lower Wadi Howar flowed through an environment characterized by numerous ground water outlets and freshwater lakes. Savanna fauna and cattle-herders occupied this region, which today receives at most 25 millimeters of rainfall per year. At that period the southern edge of the eastern Sahara was some 500 kilometers further north than today and ground water resources were recharged for the last time.     

Lowland forest loss in protected areas of Indonesian Borneo

The ecology of Bornean rainforests is driven by El Ni?o-induced droughts that trigger synchronous fruiting among trees and bursts of faunal reproduction that sustain vertebrate populations. However, many of these species- and carbon-rich ecosystems have been destroyed by logging and conversion, which increasingly threaten protected areas. Our satellite, Geographic Information System, and field-based analyses show that from 1985 to 2001, Kalimantan's protected lowland forests declined by more than 56% (>29,000 square kilometers). Even uninhabited frontier parks are logged to supply international markets. "Protected" forests have become increasingly isolated and deforested and their buffer zones degraded. Preserving the ecological integrity of Kalimantan's rainforests requires immediate transnational management.     

Crustal Layer of Seismic Velocity 6.9 to 7.6 Kilometers per Second under the Deep Oceans

Refraction measurements made in the deep ocean between the Marshall and Hawaiian islands reveal a layer of seismic velocity 7.3 kilometers per second between the 6.8 kilometer per second oceanic crustal layer and the mantle. This layer, normally masked as a second arrival, is revealed by continuous air gun refraction data. The layer may be widespread in the deep oceans.