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Preemptive and Salvage Harvesting of New England Forests: When Doing Nothing Is a Viable Alternative
Abstract: One unexpected consequence of natural disturbances in forested areas is that managers often initiate activities that may impose greater ecosystem impacts than the disturbances themselves. By salvage logging areas affected by windstorms or other impacts, by harvesting host trees in advance of insect infestation or disease, or by preemptively harvesting forests in an attempt to improve their resilience to future disturbances and stresses, managers initiate substantial changes in the ecosystem structure and function. Much of this activity is undertaken in the absence of information on the qualitative and quantitative differences between disturbance impacts and harvesting. To provide insight for such decisions we evaluated the ecosystem consequences of two major disturbance processes in New England (U.S.A.)—intense windstorms and invasive pests and pathogens—and contrasted them with impacts from preemptive and salvage harvesting. Despite dramatic physical changes in forest structure resulting from hurricane impacts and insect infestation, little disruption of biogeochemical processes or other ecosystem functions typically follows these disturbances. Indeed, the physical and organic structures produced by these disturbances are important natural features providing habitat and landscape heterogeneity that are often missing due to centuries of land use. From an ecosystem perspective there are strong arguments against preemptive and salvage logging or the attempt through silvicultural means to improve the resistance or resilience of forests to disturbance and stress. There are often valid motivations for salvage or preemptive logging including financial considerations, human safety, and a desire to shape the long-term composition and resource-production characteristics of forests. Nonetheless, there are many ecological benefits derived from leaving forests alone when they are affected or threatened by disturbances and pest and pathogen outbreaks. 相似文献
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繁茂膜海绵生物修复养殖水体中病原体的初步研究 总被引:2,自引:0,他引:2
研究繁茂膜海绵(Hymeniacidon perleve)滤食近海养殖水体中病原体细菌.海绵处理海水24 h后,海水中总大肠菌群、弧菌和总细菌分别比初始数量降低55.%~91.%、55.%~96.%和25.%~95.%.海绵滤食总大肠菌群、弧菌和总细菌速率分别在4.~105./(h·g)、1.×104~3.×104/(h·g)和2.×106~48.×106/(h·g),且滤食速率随细菌初始数量的加大而增加.当初始细菌总数在55×104~250×104/mL范围内,海绵滤食细菌的速率与细菌初始数量成线性正相关,其斜率为0.2. 相似文献
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Ferdi L. Hellweger Petr Masopust 《Journal of the American Water Resources Association》2008,44(2):509-522
Abstract: The processes affecting the fate and transport of Escherichia coli in surface waters were investigated using high‐resolution observation and modeling. The concentration patterns in Boston’s Charles River were observed during four sampling events with a total of 757 samples, including two spatial surveys with two along‐river (1,500 m length) and three across‐river (600 m length) transects at approximately 25‐m intervals, and two temporal surveys at a fixed location (Community Boating) over seven days at hourly intervals. The data reveal significant spatial and temporal structure at scales not resolved by typical monitoring programs. A mechanistic, time‐variable, three‐dimensional coupled hydrodynamic and water quality model was developed using the ECOMSED and RCA modeling frameworks. The computational grid consists of 3,066 grid cells with average length dimension of 25 m. Forcing functions include upstream and downstream boundary conditions, Stony Brook, and Muddy River (major tributaries) combined sewer overflow (CSO) and non‐CSO discharge and wind. The model generally reproduces the observed spatial and temporal patterns. This includes the presence and absence of a plume in the study area under similar loading, but different hydrodynamic conditions caused by operation of the New Charles River Dam (downstream) and wind. The model also correctly predicts an episode of high concentrations at the time‐series station following seven days of no rainfall. The model has an overall root mean square error (RMSE) of 250 CFU/100 ml and an error rate (above or below the USEPA‐recommended single sample criteria value of 235 CFU/100 ml) of 9.4%. At the time series station, the model has an RMSE of 370 CFU/100 ml and an error rate of 15%. 相似文献
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Fu LL Shuai JB Wang Y Ma HJ Li JR 《Environmental pollution (Barking, Essex : 1987)》2011,159(10):2808-2814
This study was conducted to analyze the genetic variability of Escherichia coli from domesticated animal wastes for microbial source tracking (MST) application in fecal contaminated shellfish growing waters of Xiangshan Bay, East China Sea. (GTG)5 primer was used to generate 1363 fingerprints from E. coli isolated from feces of known 9 domesticated animal sources around this shellfish culture area. Jackknife analysis of the complete (GTG)5-PCR DNA fingerprint library indicated that isolates were assigned to the correct source groups with an 84.28% average rate of correct classification. Based on one-year source tracking data, the dominant sources of E. coli were swine, chickens, ducks and cows in this water area. Moreover, annual and spatial changes of E. coli concentrations and host sources may affect the level and distribution of zoonotic pathogen species in waters. Our findings will further contribute to preventing fecal pollution in aquatic environments and quality control of shellfish. 相似文献
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Infectious Diseases and Extinction Risk in Wild Mammals 总被引:3,自引:0,他引:3
AMY B. PEDERSEN‡‡ KATE E. JONES§ CHARLES L. NUNN‡ SONIA ALTIZER 《Conservation biology》2007,21(5):1269-1279
Abstract: Parasite-driven declines in wildlife have become increasingly common and can pose significant risks to natural populations. We used the IUCN Red List of Threatened and Endangered Species and compiled data on hosts threatened by infectious disease and their parasites to better understand the role of infectious disease in contemporary host extinctions. The majority of mammal species considered threatened by parasites were either carnivores or artiodactyls, two clades that include the majority of domesticated animals. Parasites affecting host threat status were predominantly viruses and bacteria that infect a wide range of host species, including domesticated animals. Counter to our predictions, parasites transmitted by close contact were more likely to cause extinction risk than those transmitted by other routes. Mammal species threatened by parasites were not better studied for infectious diseases than other threatened mammals and did not have more parasites or differ in four key traits demonstrated to affect parasite species richness in other comparative studies. Our findings underscore the need for better information concerning the distribution and impacts of infectious diseases in populations of endangered mammals. In addition, our results suggest that evolutionary similarity to domesticated animals may be a key factor associated with parasite-mediated declines; thus, efforts to limit contact between domesticated hosts and wildlife could reduce extinction risk. 相似文献
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Maxine Zylberberg Kelly A. Lee Kirk C. Klasing Martin Wikelski 《Conservation biology》2013,27(1):103-112
Introduced disease has been implicated in recent wildlife extinctions and population declines worldwide. Both anthropogenic‐induced change and natural environmental features can affect pathogen spread. Furthermore, environmental disturbance can result in changes in stress physiology, nutrition, and social structure, which in turn can suppress immune system function. However, it remains unknown whether landscape variation results in heterogeneity in host resistance to pathogens. Avian pox virus, a pathogen implicated in avian declines and extinctions in Hawaii, was introduced to the Galapagos in the 1890s, and prevalence (total number of current infections) has increased recently in finches. We tested whether prevalence and recovery trends in 7 species of Galapagos finches varied by elevation or human land use. To do so, we used infection data obtained from 545 wild‐caught birds. In addition, we determined whether annual changes in 4 aspects of innate immune function (complement protein activity, natural antibody activity, concentration of PIT54 protein, and heterophil:lymphocyte ratio) varied by elevation or land use. Prevalence and recovery rates did not vary by elevation from 2008 to 2009. Avian pox prevalence and proportion of recovered individuals in undeveloped and urban areas did not change from 2008 to 2009. In agricultural areas, avian pox prevalence increased 8‐fold (from 2% to 17% of 234 individuals sampled) and proportion of recovered individuals increased (11% to 19%) from 2008 to 2009. These results suggest high disease‐related mortality. Variation in immune function across human land‐use types correlated with variation in both increased prevalence and susceptibility, which indicates changes in innate immune function may underlie changes in disease susceptibility. Our results suggest anthropogenic disturbance, in particular agricultural practices, may underlie immunological changes in host species that themselves contribute to pathogen emergence. Variación con el Uso de Suelo de la Función Inmune y la Prevalencia de la Varicela Aviar en Pinzones de las Galápagos 相似文献
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基于高通量定量PCR研究城市化小流域微生物污染特征 总被引:2,自引:0,他引:2
水体微生物污染(包括致病菌、病毒、寄生虫)会引起多种传染病和寄生虫病,对生产生活用水安全和人体健康造成重要威胁。本研究应用基于Taq Man探针的高通量荧光定量PCR技术对厦门市后溪流域冬季微生物污染进行检测,包含了5种粪便污染源(人源、反刍动物源、猪源、家禽源、狗源)微生物源示踪分子标记物与12种病原微生物。结果表明,该流域在上游及水库5个位点没有粪便污染,仅在其中一个水库位点检测出棘阿米巴,微生物污染极小;中下游检测出人类、反刍动物、猪、家禽、狗粪便污染,并且检测出产气荚膜梭菌、肠聚集性大肠杆菌、肠毒素型大肠杆菌、幽门螺杆菌、霍乱弧菌、副溶血弧菌、棘阿米巴、克雷伯氏肺炎杆菌等病原菌,其中流经旧城区居民生活生产区水样微生物污染严重,下游新城区微生物污染较小。这些结果暗示着城市人类活动是流域微生物污染主要来源,应从污染源头加强微生物污染控制。 相似文献