Identifying saltcedar with hyperspectral data and support vectormachines     

Reginald S. Fletcher  James H. Everitt  Chenghai Yang 《国际地球制图》2013,28(3):195-209

Saltcedar (Tamarix spp.) are a group of dense phreatophytic shrubs and trees that are invasive to riparian areas throughout the United States. This study determined the feasibility of using hyperspectral data and a support vector machine (SVM) classifier to discriminate saltcedar from other cover types in west Texas. Spectral measurements were collected with a ground-based hyperspectral spectroradiometer (spectral range 350–2500 nm) in December 2008 and April 2009. Spectral data consisting of 1698 spectral bands (400–1349, 1441–1789, 1991–2359 nm) were subjected to a support vector machine classification to differentiate saltcedar from other vegetative and non-vegetative classes. For both dates, a linear kernel model with a C value (error penalty) of 100 was found optimum for separating saltcedar from the other classes. It identified saltcedar with accuracies ranging from 95% to 100%. Findings support further exploration of hyperspectral remote sensing technology and SVM classifiers for differentiating saltcedar from other cover types.  相似文献   

Restoration of palatable grasses: A study case in degraded rangelands of central Argentina     

Roberto A. Distel  Julin Pietragalla  Ricardo M. Rodríguez Iglesias  Nilda G. Didon  Romina J. Andrioli 《Journal of Arid Environments》2008,72(10):1968-1972

Restoration of palatable grasses on degraded rangelands dominated by unpalatable grasses in central Argentina is limited by low availability of seeds and safe sites for seedling establishment. The objective of our study was to determine how mechanical disturbance of unpalatable grasses (Stipa spp.) in combination with seeding of a palatable grass (Poa ligularis) influenced species composition in a degraded rangeland excluded from livestock grazing. In April 2001 10 blocks were uniformly distributed on a previously burned site dominated by unpalatable grasses, and treatments applied in 8 m×8 m experimental plots. Treatments were ‘disked and seeded’ and control (no disking, no seeding). Perennial plant cover and end-of-season standing crop, at species or species group level, were assessed in December 2002/2003 and in December 2004/2006, respectively. P. ligularis out-competed both tillers of unpalatable grasses that survived mechanical disturbance and seedlings of unpalatable grasses established after mechanical disturbance. The cover and end-of-season standing crop of unpalatable grasses was higher in the control than in the ‘disked and seeded’ treatment, whereas the cover and end-of-season standing crop of P. ligularis was higher in the latter than in the former treatment. Our results suggest that a rapid transition from a state dominated by unpalatable grasses to a state dominated by palatable grasses can be achieved by mechanical disturbance of unpalatable grasses in combination with seeding of palatable grasses in semiarid rangelands of central Argentina.  相似文献   

Feeding ecology of whelks on an intertidal sand flat in north‐eastern New Zealand     

M. J. Stewart  R. G. Creese 《新西兰海洋与淡水研究杂志》2013,47(5):819-831

The dispersion patterns and feeding behaviour of intertidal whelks were investigated in north‐eastern New Zealand. Aggregations of whelks feeding on clams occurred regularly, with an average of 15–20 individuals per aggregation. Death of clams was attributable to predation in up to 50% of the aggregations, although scavenging of dead and moribund animals was the main activity of whelks. Laboratory and field studies showed that Lepsiella scobina (generally not considered a soft shore species) was the main whelk predator at Lews Bay, Whangateau Harbour, drilling a small neat hole through the clam shell. The distinction between Cominella spp. as predators or scavengers is not so clear. Reseeding of intertidal clams, Austrovenus stutchburyi, has been proposed as a technique for reestablishing populations in some degraded New Zealand estuaries. The impact of whelk predation has many implications for A. stutchburyi reseeding. Both L. scobina and Cominella adspersa may potentially prey on newly reseeded clams as they preferentially attacked small clams in the laboratory. On‐growing to a larger size before reseeding may be advantageous although large size was not found to protect prey from predation. Additionally, no seasonal trend in whelk activity was found.  相似文献   

盐水处理对沙拐枣气体交换特征、光合色素和可溶性糖含量的影响   总被引：3，自引：2，他引：1  

王伟华  张希明  闫海龙  梁少民  马建兵  杨小林 《干旱区地理》2009,32(4)

通过对室外不同浓度盐水(0、4、12、20、28 g/L粗盐)灌溉的桶栽沙拐枣(Calligonum spp.)气体交换参数、光合色素和可溶性糖含量随时间变化情况的分析结果表明:随着盐处理时间的延续,(1)低盐(4～12 g/L)处理条件下沙拐枣光合作用先逐渐增强,后又因非气孔因素限制而下降;高盐(20～28 g/L)处理条件下植株前期受气孔因素限制,后期受非气孔因素限制,光合作用严重下降.(2)不同盐处理条件下沙拐枣叶绿素a(chla)、叶绿素b(chlb)、总叶绿素(chl)含量均下降,类胡萝卜素(car)、chla/b、car/chl先增加后下降,但低盐处理较高盐处理变化小.(3)低盐处理对沙拐枣可溶性糖含量变化不大,而高盐处理下其极显著增加.因此,短期低盐处理促进沙拐枣光合作用,但长期盐处理亦使植物光合作用下降;高盐处理抑制沙拐枣生长,长期处理将导致植物死亡.  相似文献   

Bactericidal Activity of Ag Nanoparticles Decorated TiO2 Microspheres and Effects of Water Composition and Extracellular Polymeric Substances          下载免费PDF全文

Yi Li  Haixia Ding  Kai Mao  Dawei Wang  Qing Wang  Wenlong Zhang 《洁净——土壤、空气、水》2015,43(4):512-520

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Biodegradation of Petroleum Hydrocarbons by Pseudomonas putida Strain MHF 7109     

Dipty Singh  Madhusudan H. Fulekar 《洁净——土壤、空气、水》2010,38(8):781-786

Pseudomonas putida MHF 7109 has been isolated and identified from cow dung microbial consortium for biodegradation of selected petroleum hydrocarbon compounds – benzene, toluene, and o‐xylene (BTX). Each compound was applied separately at concentrations of 50, 100, 250, and 500 mg L^?1 in minimal salt medium to evaluate degradation activity of the identified microbial strain. The results indicated that the strain used has high potential to degrade BTX at a concentration of 50 mg L^?1 within a period of 48, 96, and 168 h, respectively; whereas the concentration of 100 mg L^?1 of benzene and toluene was found to be completely degraded within 120 and 168 h, respectively. Sixty‐two percent of o‐xylene were degraded within 168 h at the 100 mg L^?1 concentration level. The maximum degradation rates for BTX were 1.35, 1.04, and 0.51 mg L^?1 h^?1, respectively. At higher concentrations (250 and 500 mg L^?1) BTX inhibited the activity of microorganisms. The mass spectrometry analysis identified the intermediates as catechol, 2‐hydroxymuconic semialdehyde, 3‐methylcatechol, cis‐2‐hydroxypenta‐2,4‐dienoate, 2‐methylbenzyl alcohol, and 1,2‐dihydroxy‐6‐methylcyclohexa‐3,5‐dienecarboxylate, for BTX, respectively. P. putida MHF 7109 has been found to have high potential for biodegradation of volatile petroleum hydrocarbons.  相似文献   

海水网箱养殖大黄鱼病原菌研究   总被引：42，自引：3，他引：39  

林克冰  周宸  刘家富  周胜利  曾志南  陈木 《海洋科学》1999,23(4):58-62

从福建宁德地区患病大黄鱼肝、肾、脾等组织分离出３株病原菌,进行纯化培养、人工感染、药敏试验及菌种鉴定等研究,根据形态及生理生化特征,其中２株致病菌归为哈维氏弧菌,另一株为腐败假单胞菌。药敏实验的结果表明,氟哌酸、环丙氟哌酸、氯霉素、庆大霉素和复方新诺明等对致病菌有较强的抑制作用。  相似文献   

Relative change in stream discharge from a tropical watershed improves predictions of fecal bacteria in near-shore environments     

Ayron M. Strauch 《水文科学杂志》2017,62(9):1381-1393

Statistical models poorly predict bacteria in near-shore environments of tropical islands due to inaccuracies in runoff and discharge characterization of storm events. Intense, short duration storms on small, steeply sloped watersheds produce high rates of runoff, resulting in rapid pulses of discharge that influence the physical and physiological conditions of the fate and transport of pathogens. As such, increasing rates of discharge are expected to have a different influence on sediment transport and pathogen load compared to decreasing rates of discharge. Regression modeling was used to examine the affect of antecedent streamflow on the interaction between environmental parameters and two fecal indicator bacteria, enterococci and Clostridium perfringens. Including the relative change in discharge incorporates a proximate representation of the energy available to transport particulates, improving predictions of near-shore water quality. Understanding factors that influence pathogen loads improves management of watersheds and protects public health.  相似文献   

Intercellular localization of nitrogenase in a non-heterocystous cyanobacterium (cyanophyte), <Emphasis Type="Italic">Trichodesmium</Emphasis> sp. NIBB1067     

Kaori Ohki 《Journal of Oceanography》2008,64(2):211-216

The nitrogenase activities of cyanobacteria of the genus Trichodesmium are strictly light-dependent, although they do not develop heterocysts. Recently, the development of heterocyst-equivalent cells (diazocytes) was suggested in Trichodesmium spp. However, no cells with a similar appearance to diazocytes could be found in Trichodesmium sp. NIBB1067. An immunocytochemical analysis of nitrogenase in individual cells was performed using polyclonal antibodies generated from DNA fragments of genes encoding the Fe-protein and the α-and the β-subunit of the MoFe-protein of nitrogenase of Trichodesmium sp. NIBB1067. Visualization of the antibody binding was carried out using a horseradish peroxidase-conjugated secondary antibody and a chromogenic substrate, 3,3′-diaminobenzidine, to avoid the masking effects caused by the bright autofluorescence emitted by Trichodesmium cells. Nitrogenase proteins were detected in almost all the cells (always higher than 95% of total cells) grown under nitrogen-limited conditions. These results indicate that Trichodesmium sp. NIBB1067 does not differentiate heterocyst-equivalent cells.  相似文献   

网箱养殖石斑鱼病毒性神经坏死病流行调查   总被引：1，自引：0，他引：1       下载免费PDF全文

苏亚玲 《海洋科学》2008,32(9):52-56

厦门海水网箱养殖石斑鱼春、夏季节暴发性疾病经过流行病学调查和病原检测，确认主要病原为病毒性神经坏死病毒，病鱼外观表现典型的神经异常症状。应用逆转录聚合酶链式反应（RT—PCR）技术检测5种石斑鱼：赤点石斑鱼（Epinephelus akaara）、青石斑鱼（E．awoara）、云纹石斑鱼（Emoara）、紫石斑鱼（E．lanceolatus）、马拉巴石斑鱼（E．malabaricus）.检测76条石斑鱼，检出率90％；病鱼的脑、视网膜、肾脏、肝脏、脾脏等组织均能检出神经坏死病毒（NNV），以脑和视网膜检出率最高，肾脏次之，肝脏、脾脏检出率较少，鳃未检出。  相似文献