Fire Risk in Revegetated Bunchgrass Communities Infested with Bromus tectorum     

Steven O. Link  Randal W. Hill  Sheel Bansal 《Strength and Conditioning Journal》2019,72(3):539-541

In rangeland ecosystems, invasive annual grass replacement of native perennials is associated with higher fire risk. Large bunchgrasses are often seeded to reduce cover of annuals such as Bromus tectorum L. (cheatgrass), but there is limited information about how revegetation reduces fire risk over the long term. We assessed how revegetated community composition influences fire risk at three sites in Columbia National Wildlife Refuge in Grant County, Washington that were revegetated with large bunchgrasses 8 ? 18 years before the study. At each site, five replicates of 10 plots (10 × 10 m) were established. Fire risk was determined as the probability that a plot would completely burn following ignition at a randomly located point in each plot (i.e., if 8 of 10 plots burned, then fire risk was 80%). Preignition, cover of bunchgrasses, cheatgrass, forbs, and surface characteristics were determined for each plot. Fire risk was < 100%. However, fire risk was still relatively high around 73% and did not differ significantly among sites despite differences in cheatgrass and bunchgrass cover, which may have been attributable to other characteristics, such as high total fuels cover (> 80% at all sites) and unvegetated gap cover (soil and soil cryptogams, < 17%). This information can provide guidance for future studies with larger ranges of cover characteristics to develop robust fire risk models, which ultimately will be used to aid rangeland managers who need to specify reduction of fire risk after reestablishing large bunchgrasses in rangelands infested with cheatgrass.  相似文献   

Effect of competition between Vicia faba and Camelina sativa as a model weed in breeding for organic conditions          下载免费PDF全文

L Ghaouti  A Schierholt  W Link 《Weed Research》2016,56(2):159-167

Weeds can have a detrimental effect on faba bean (Vicia faba) crops in organic farming. Breeding for competitive cultivars is one option for weed control in organic conditions. The aim of this study was to analyse the impact of heterozygosity and heterogeneity levels and plant height on the competitive ability of faba bean genotypes. A set of 24 genotypes, classified as genotype groups (eight inbred lines, eight polycross progenies, two inbred line bulks, two hybrid bulks and four controls), was tested under two treatments: with and without a model weed. Each group of genotypes was equally composed of tall and short genotypes. The competitive ability of the faba bean genotypes was tested with Camelina sativa (false flax) as the model weed in two German locations over the course of 2 years. Yield loss due to weed competition, as recorded per faba bean genotype, was mainly dependent on the heterozygosity level of the genotypes; hybrid bulks were the most competitive genotype group with an average loss of yield of only 6%, whereas the inbred lines were the least competitive genotype group and recorded an average yield loss of 35%. Within the genotype group, no correlations were found between either the yield performance of the genotypes or their plant height and their competitive responses. The competitive ability of faba bean against weeds was mainly determined by their level of heterozygosity; thus, highly heterozygous cultivars should be promoted for breeding.  相似文献   

Conventional and contemporary approaches for drought tolerance rice breeding: Progress and prospects     

C Anilkumar  Rameswar Prasad Sah  Radha Beena  Muhammed Azharudheen TP  Awadesh Kumar  Sasmita Behera  NC Sunitha  SK Pradhan  KR Reshmi Raj  Parameswaran C  BC Marndi  Anil Kumar Singh 《Plant Breeding》2023,142(4):418-438

Drought is becoming a major threat to rice farming across the globe owing to the depletion of water tables in rice-growing belts. Drought affects rice plants at multiple stages, causing damage at morphological and physio-biochemical levels, leading to severe losses that exceed losses from all other stresses. The amalgamation of conventional breeding methods with modern molecular biology tools and biometrical methods could help accelerate the genetic gain for drought tolerance in rice. Many drought-tolerance traits with genetic determinants have been identified and exploited for tolerance rice variety breeding. The integration of genome-wide association study and genomic selection tools with speed breeding shortened the breeding cycle and aided in rapid improvement of genetic gain. In this review, we emphasized the progress made through classical breeding as well as the limitations and usefulness of current genomic methods in improving drought tolerance. We briefly addressed methods for identifying genetic determinants for drought tolerance and deploying them through genomics-assisted breeding programmes to develop high-yielding drought-tolerant rice cultivars.  相似文献   

Trophic role of Atlantic cod in the ecosystem     

Jason S. Link  Bjarte Bogstad  Henrik Sparholt  & George R. Lilly 《Fish and Fisheries》2009,10(1):58-87

As the world's oceans continue to undergo drastic changes, understanding the role of key species therein will become increasingly important. To explore the role of Atlantic cod ( Gadus morhua Gadidae) in the ecosystem, we reviewed biological interactions between cod and its prey, predators and competitors within six ecosystems taken from a broad geographic range: three are cod-capelin ( Mallotus villosus Osmeridae) systems towards cod's northern Atlantic limit (Barents Sea, Iceland and Newfoundland–Labrador), two are more diverse systems towards the southern end of the range (North Sea and Georges Bank–Gulf of Maine), and one is a species-poor system with an unusual physical and biotic environment (Baltic Sea). We attempt a synthesis of the role of cod in these six ecosystems and speculate on how it might change in response to a variety of influences, particularly climate change, in a fashion that may apply to a wide range of species. We find cod prey, predators and competitors functionally similar in all six ecosystems. Conversely, we estimate different magnitudes for the role of cod in an ecosystem, with consequently different effects on cod, their prey and predator populations. Fishing has generally diminished the ecological role of cod. What remains unclear is how additional climate variability will alter cod stocks, and thus its role in the ecosystem.  相似文献   

Nutrient concentration dynamics in an inland Pacific Northwest watershed before and after timber harvest     

J.A. Gravelle  G. Ice  T.E. Link  D.L. Cook 《Forest Ecology and Management》2009

The nutrient loads of water draining forested watersheds are generally lower than the loads in water draining basins with other dominant land uses. Commercial forest management activities including timber harvesting, site preparation, road construction, and maintenance can alter the chemical properties of headwater forest streams, and there are concerns this can result in cumulative effects at downstream locations. Monthly water samples were collected from 1992 to 2006 in the Mica Creek Experimental Watershed (MCEW) in northern Idaho. This period of record included a pre-treatment time interval from 1992 to 1997; post-road construction period from 1997 to 2001; and post-harvest period from 2001 to 2006. Samples were analyzed for total Kjeldahl nitrogen (TKN), total ammonia nitrogen (TAN), nitrate + nitrite (NO₃ + NO₂), total phosphorus (TP), and orthophosphate (OP). Statistically significant increases (p < 0.001) were observed in NO₃ + NO₂ concentrations following both clearcut and partial cut harvest practices. Downstream of the clearcut harvest activity, mean monthly increases of 0.29 mg-N L⁻¹ were observed. Statistically significant increases were also observed at sites further downstream, but changes were smaller than those immediately below the harvest sites and reflected dilution and possibly instream processing and/or uptake. Continued monitoring at these sites will help evaluate nutrient concentration trends during stand regrowth and hydrologic recovery.  相似文献   

Cold air drainage and modeled nocturnal leaf water potential in complex forested terrain     

Hubbart JA  Kavanagh KL  Pangle R  Link T  Schotzko A 《Tree physiology》2007,27(4):631-639

Spatial variation in microclimate caused by air temperature inversions plays an important role in determining the timing and rate of many physical and biophysical processes. Such phenomena are of particular interest in mountainous regions where complex physiographic terrain can greatly complicate these processes. Recent work has demonstrated that, in some plants, stomata do not close completely at night, resulting in nocturnal transpiration. The following work was undertaken to develop a better understanding of nocturnal cold air drainage and its subsequent impact on the reliability of predawn leaf water potential (Psi(pd)) as a surrogate for soil water potential (Psi(s)). Eight temperature data loggers were installed on a transect spanning a vertical distance of 155 m along a north facing slope in the Mica Creek Experimental Watershed (MCEW) in northern Idaho during July and August 2004. Results indicated strong nocturnal temperature inversions occurring from the low- to upper-mid-slope, typically spanning the lower 88 m of the vertical distance. Based on mean temperatures for both months, inversions resulted in lapse rates of 29.0, 27.0 and 25.0 degrees C km(-1) at 0000, 0400 and 2000 h, respectively. At this scale (i.e., < 1 km), the observed lapse rates resulted in highly variable nighttime vapor pressure deficits (D) over the length of the slope, with variable impacts on modeled disequilibrium between soil and leaf water potential. As a result of cold air drainage, modeled Psi(pd) became consistently more negative (up to -0.3 MPa) at higher elevations during the night based on mean temperatures. Nocturnal inversions on the lower- and mid-slopes resulted in leaf water potentials that were at least 30 and 50% more negative over the lower 88 m of the inversion layer, based on mean and maximum temperatures, respectively. However, on a cloudy night, with low D, the maximum decrease in Psi(pd) was -0.04 MPa. Our results indicate that, given persistent cold air drainage and nighttime stomatal opening, serious errors will result if Psi(s) is estimated from Psi(pd).  相似文献   

Overview on the review articles published during the past 30 years relating to the potential climate change effects on plant pathogens and crop disease risks     

P. Juroszek  P. Racca  S. Link  J. Farhumand  B. Kleinhenz 《Plant pathology》2020,69(2):179-193

From 1988 to July 2019 more than 100 review articles were published, including opinion papers and book chapters, that focused on potential climate change effects on plant pathogens and the future crop disease risks. Therefore, an overview of them is presented herein, particularly helpful for beginners and non-experts in climate change biology research. Specifically, this overview contributes to a faster and more convenient identification of appropriate review articles, for example, related to a certain crop, pathogen, plant disease or country of interest. However, not all important crops, pathogens, diseases and countries are considered specifically and in-depth in any of these review articles, suggesting that there are still research gaps prevalent, which are also highlighted herein. Nevertheless, the overview suggests that researchers are increasingly busy and successful in summarizing the fragmented information spread throughout the international literature. Consequently, they are providing ‘step-by-step’ a comprehensive, in-depth, and continuously updated knowledge platform on potential climate change effects on plant pathogens and the respective crop disease risks in the future, although some aspects will, by nature, be repeated.  相似文献   

Effect of dietary zinc supplementation and phytase pre-treatment of soybean meal or corn gluten meal on growth, zinc status and zinc-related metabolism in rainbow trout, Oncorhynchus mykiss   总被引：1，自引：0，他引：1  

L. Ramseyer  D. Garling Jr.  G. Hill  J. Link 《Fish physiology and biochemistry》1999,20(3):251-261

Rainbow trout, Oncorhynchus mykiss, were fed diets containing untreated or phytase-treated soybean meal and corn gluten meal with or without 50 mg supplemental zinc kg–1 to determine if dietary phytate caused a zinc (Zn) deficiency. Fish fed diets containing untreated soybean meal and corn gluten meal without supplemental Zn (basal diet) showed no signs of a Zn deficiency after 170 d of weight gain. Weight gain, carcass protein content, total bone Zn, and alkaline phosphatase and carboxypeptidase B activities were not significantly altered in fish fed the basal diet. Dietary phytate removal and supplemental dietary Zn were not required to prevent Zn deficiency in rainbow trout fed a plant-based diet. Although bone Zn concentrations were reduced in fish fed the basal diet, total bone Zn increased in all fish regardless of dietary treatment. Future assessments of Zn status of fish should be based on changes in Zn-dependent metabolism or total bone Zn rather than on bone Zn concentration.  相似文献   

水稻突变群体的构建及功能基因组学   总被引：17，自引：3，他引：17  

江树业 《分子植物育种》2003,1(2):137-150

随着水稻基因组全序列的测定完成，功能基因组学已成为重点研究内容。功能基因组学主要研究生物有机体内各基因的生物学功能进而了解所有基因如何协调发挥作用完成一系列的生长发育过程。目前已经发展了多种分析鉴定基因功能的方法，其中最直接最有效的方法是构建饱和的基因突变群体，通过突变体分析鉴定基因功能。本文主要阐述了各种构建方法及其优缺点以及在功能基因分离鉴定上的应用。自发突变的频率极低，且自发突变基因的分离难度比较大，只能作为突变群体构建的辅助方法。利用EMS等化学诱变剂可以在短时间内构建大量点突变群体，并可用TILLING进行突变检测，但多位点的点突变使突变表型难以鉴定。由快中子等物理诱变也可以在短时间内构建大量缺失突变体，且可用Ddeteagene系统进行检测；但多基因缺失、多位点缺失和内含子缺失等使突变表型的分析可能无法进行。利用T—DNA、转座子和反转录转座子等构建插入突变体已经成为突变库构建的主要方法。T—DNA插入已成功应用于水稻大规模突变体的构建，但只限于转基因效率较高的品种；T—DNA在基因组中整合的复杂性以及转基因过程中由组织培养等引发的突变等，增加了突变体表型和分子分析的难度。Tos17是目前应用最为成功的反转录转座子，但多拷贝的插入使突变体的表型鉴定和分子鉴定较为困难，因为只有10％左右的突变性状是由Tos17插入引起的。理论上，Ac／Ds双因子系统是目前最理想的水稻插入突变库构建体系，Ds的单拷贝插入，大大方便了突变体的表型分析和分子鉴定；Ds的回复突变，可以验证突变表型是否由Ds插入引起；但在血转座酶驱动下Ds可能发生的多次跳动所形成的痕迹(footprint)也可能影响突变表型的分析。RNAi可以有效地使目标基因沉默，但并不是所有基因均可被RNAi沉默；对多因一效基因或同源性较高的基因家族，RNAi会同时作用这些基因，沉默表型很难鉴定。可见，每一种方法都有各自的优缺点，但不同的方法是可以互补的，通过各种方法是能够构建成理想的水稻突变库的。  相似文献   

Strong fisheries management and governance positively impact ecosystem status          下载免费PDF全文

Alida Bundy  Ratana Chuenpagdee  Jennifer L Boldt  Maria de Fatima Borges  Mohamed Lamine Camara  Marta Coll  Ibrahima Diallo  Clive Fox  Elizabeth A Fulton  Ayse Gazihan  Astrid Jarre  Didier Jouffre  Kristin M Kleisner  Ben Knight  Jason Link  Patroba P Matiku  Hicham Masski  Dimitrios K Moutopoulos  Chiara Piroddi  Tiit Raid  Ignacio Sobrino  Jorge Tam  Djiga Thiao  Maria Angeles Torres  Konstantinos Tsagarakis  Gro I van der Meeren  Yunne‐Jai Shin 《Fish and Fisheries》2017,18(3):412-439

Fisheries have had major negative impacts on marine ecosystems, and effective fisheries management and governance are needed to achieve sustainable fisheries, biodiversity conservation goals and thus good ecosystem status. To date, the IndiSeas programme (Indicators for the Seas) has focussed on assessing the ecological impacts of fishing at the ecosystem scale using ecological indicators. Here, we explore fisheries ‘Management Effectiveness’ and ‘Governance Quality’ and relate this to ecosystem health and status. We developed a dedicated expert survey, focused at the ecosystem level, with a series of questions addressing aspects of management and governance, from an ecosystem‐based perspective, using objective and evidence‐based criteria. The survey was completed by ecosystem experts (managers and scientists) and results analysed using ranking and multivariate methods. Results were further examined for selected ecosystems, using expert knowledge, to explore the overall findings in greater depth. Higher scores for ‘Management Effectiveness’ and ‘Governance Quality’ were significantly and positively related to ecosystems with better ecological status. Key factors that point to success in delivering fisheries and conservation objectives were as follows: the use of reference points for management, frequent review of stock assessments, whether Illegal, Unreported and Unregulated (IUU) catches were being accounted for and addressed, and the inclusion of stakeholders. Additionally, we found that the implementation of a long‐term management plan, including economic and social dimensions of fisheries in exploited ecosystems, was a key factor in successful, sustainable fisheries management. Our results support the thesis that good ecosystem‐based management and governance, sustainable fisheries and healthy ecosystems go together.  相似文献