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61.
62.
Alison C. Iles Tarik C. Gouhier Bruce A. Menge Julia S. Stewart Alison J. Haupt Margaret C. Lynch 《Global Change Biology》2012,18(2):783-796
Eastern boundary current systems are among the most productive and lucrative ecosystems on Earth because they benefit from upwelling currents. Upwelling currents subsidize the base of the coastal food web by bringing deep, cold and nutrient‐rich water to the surface. As upwelling is driven by large‐scale atmospheric patterns, global climate change has the potential to affect a wide range of significant ecological processes through changes in water chemistry, water temperature, and the transport processes that influence species dispersal and recruitment. We examined long‐term trends in the frequency, duration, and strength of continuous upwelling events for the Oregon and California regions of the California Current System in the eastern Pacific Ocean. We then associated event‐scale upwelling with up to 21 years of barnacle and mussel recruitment, and water temperature data measured at rocky intertidal field sites along the Oregon coast. Our analyses suggest that upwelling events are changing in ways that are consistent with climate change predictions: upwelling events are becoming less frequent, stronger, and longer in duration. In addition, upwelling events have a quasi‐instantaneous and cumulative effect on rocky intertidal water temperatures, with longer events leading to colder temperatures. Longer, more persistent upwelling events were negatively associated with barnacle recruitment but positively associated with mussel recruitment. However, since barnacles facilitate mussel recruitment by providing attachment sites, increased upwelling persistence could have indirect negative impacts on mussel populations. Overall, our results indicate that changes in coastal upwelling that are consistent with climate change predictions are altering the tempo and the mode of environmental forcing in near‐shore ecosystems, with potentially severe and discontinuous ramifications for ecosystem structure and functioning. 相似文献
63.
Disease effects on reproduction can cause population cycles in seasonal environments 总被引:1,自引:0,他引:1
Smith MJ White A Sherratt JA Telfer S Begon M Lambin X 《The Journal of animal ecology》2008,77(2):378-389
1. Recent studies of rodent populations have demonstrated that certain parasites can cause juveniles to delay maturation until the next reproductive season. Furthermore, a variety of parasites may share the same host, and evidence is beginning to accumulate showing nonindependent effects of different infections. 2. We investigated the consequences for host population dynamics of a disease-induced period of no reproduction, and a chronic reduction in fecundity following recovery from infection (such as may be induced by secondary infections) using a modified SIR (susceptible, infected, recovered) model. We also included a seasonally varying birth rate as recent studies have demonstrated that seasonally varying parameters can have important effects on long-term host-parasite dynamics. We investigated the model predictions using parameters derived from five different cyclic rodent populations. 3. Delayed and reduced fecundity following recovery from infection have no effect on the ability of the disease to regulate the host population in the model as they have no effect on the basic reproductive rate. However, these factors can influence the long-term dynamics including whether or not they exhibit multiyear cycles. 4. The model predicts disease-induced multiyear cycles for a wide range of realistic parameter values. Host populations that recover relatively slowly following a disease-induced population crash are more likely to show multiyear cycles. Diseases for which the period of infection is brief, but full recovery of reproductive function is relatively slow, could generate large amplitude multiyear cycles of several years in length. Chronically reduced fecundity following recovery can also induce multiyear cycles, in support of previous theoretical studies. 5. When parameterized for cowpox virus in the cyclic field vole populations (Microtus agrestis) of Kielder Forest (northern England), the model predicts that the disease must chronically reduce host fecundity by more than 70%, following recovery from infection, for it to induce multiyear cycles. When the model predicts quasi-periodic multiyear cycles it also predicts that seroprevalence and the effective date of onset of the reproductive season are delayed density-dependent, two phenomena that have been recorded in the field. 相似文献
64.
To a great extent, the cellular compartmentalization and molecular interactions are indicative of the function of a protein.
The development of simple and efficient tools for testing the subcellular location of proteins is indispensable to elucidate
the function of genes in plants. In this report, we assessed the feasibility ofAgrobacterium-mediated transformation of hydroponically grown roots to follow intracellular targeting of proteins fused to green fluorescent
protein (GFP). We developed a simple in planta assay for subcellular localization of proteins inArabidopsis roots via transient transformation and tested this method by expressing a GFP fusion of a known nuclear protein, IQD1. Visualization
of transiently expressed GFP fusion proteins in roots by means of confocal microscopy is superior to the analysis of green
tissues because the roots are virtually transparent and free of chlorophyll autofluorescence. 相似文献
65.
Palaeoecological analyses of raised peat bog deposits in northwest Europe show the naturalness, antiquity and robust response
of these ecosystems to environmental changes from c. 7800 years ago to the present. A review of the techniques used to identify
these long-term features is presented and the role of climate change, autogenic change processes and human disturbance is
discussed. Millennial records of vegetation changes recorded in peat deposits demonstrate the response (often rapid) of raised
peat bog vegetation to climatic changes during the mid-Holocene, Bronze Age/Iron Age transition and the Little Ice Age. Greenhouse
warming scenarios exceed the reconstructed Holocene record of climatic changes (c. the last 11, 500 years), and bog-water
tables may fall considerably. A combination of centennial palaeoecological analyses of bogs affected by human disturbance
and experimental manipulations have been used as analogues for the potential response of raised peat bog vegetation to these
changes. These show that possible greenhouse gas climate forcing scenarios may exceed the ability of Sphagnum- dominated raised peat bogs to respond to projected increases in summer temperature and decreases in summer precipitation.
In combination with increasing N deposition, a loss of their Sphagnum-rich vegetation and increases in the abundance of vascular plants could occur on decadal timescales. 相似文献
66.
Frédéric Barraquand Stilianos Louca Karen C. Abbott Christina A. Cobbold Flora Cordoleani Donald L. DeAngelis Bret D. Elderd Jeremy W. Fox Priscilla Greenwood Frank M. Hilker Dennis L. Murray Christopher R. Stieha Rachel A. Taylor Kelsey Vitense Gail S.K. Wolkowicz Rebecca C. Tyson 《Ecology letters》2017,20(8):1074-1092
Population cycling is a widespread phenomenon, observed across a multitude of taxa in both laboratory and natural conditions. Historically, the theory associated with population cycles was tightly linked to pairwise consumer–resource interactions and studied via deterministic models, but current empirical and theoretical research reveals a much richer basis for ecological cycles. Stochasticity and seasonality can modulate or create cyclic behaviour in non‐intuitive ways, the high‐dimensionality in ecological systems can profoundly influence cycling, and so can demographic structure and eco‐evolutionary dynamics. An inclusive theory for population cycles, ranging from ecosystem‐level to demographic modelling, grounded in observational or experimental data, is therefore necessary to better understand observed cyclical patterns. In turn, by gaining better insight into the drivers of population cycles, we can begin to understand the causes of cycle gain and loss, how biodiversity interacts with population cycling, and how to effectively manage wildly fluctuating populations, all of which are growing domains of ecological research. 相似文献
67.
该研究采用自制循环营养液系统,设置循环营养液且悬根长度为0 cm(T1)、静止营养液且初始悬根长度为0 cm(T2)、循环营养液且悬根长度为2 cm(T3)3个处理,通过测量营养液的溶解氧、pH、EC值,根系与叶片的形态学指标和生理指标,以及根系显微结构观察,以明晰根际氧环境在水培尖叶莴苣中的作用机理。结果表明:(1)尖叶莴苣幼苗的根际氧环境以T3处理最优,T2处理次之,T1处理最差,但它们营养液的pH和离子总量差异不大。(2)各处理根系和叶片的长势均表现为T3>T2>T1;其根系长度、根系表面积、根系体积、平均直径、根尖数、叶片表面积和叶片体积,以及植株茎粗、株高、根干重、地上部干重、壮苗指数、根冠比均以T3处理最大,但T3与T2间均无显著差异,而两者均显著大于T1处理,此时T3处理的壮苗指数和根冠比分别比T1显著增加了38.8%和13.4%。(3)尖叶莴苣根系维管束以及木质部的面积大小均表现为T3>T2>T1。(4)T1处理根系SOD、POD活性均高于相应的T2和T3处理,CAT活性和MDA含量均显著高于T3处理;T1处理叶片叶绿素和4种有机酸含量基本低于T2和T3,柠檬酸及琥珀酸含量以T2最大,苹果酸及丙二酸含量以T3最大。研究发现,根际低氧胁迫对水培尖叶莴苣幼苗生长、生理和品质特性均有明显抑制作用,且空气中的氧气相对于营养液中的氧气抑制作用更明显;在水培尖叶莴苣生产上设置适宜的悬根长度,可增加根系与空气接触面积,从而增加根际氧供给,解决水气矛盾,提升尖叶莴苣的产量与品质。 相似文献
68.
Response of tundra ecosystem in southwestern Alaska to Younger-Dryas climatic oscillation 总被引:3,自引:0,他引:3
F. S. HU B. Y. LEE D. S. KAUFMAN† S. YONEJI D. M. NELSON P. D. HENNE 《Global Change Biology》2002,8(11):1156-1163
Climatic warming during the last glacial–interglacial transition (LGIT) was punctuated by reversals to glacial‐like conditions. Palaeorecords of ecosystem change can help document the geographical extent of these events and improve our understanding of biotic sensitivity to climatic forcing. To reconstruct ecosystem and climatic variations during the LGIT, we analyzed lake sediments from southwestern Alaska for fossil pollen assemblages, biogenic‐silica content (BSiO2%), and organic‐carbon content (OC%). Betula shrub tundra replaced herb tundra as the dominant vegetation of the region around 13 600 cal BP (cal BP: 14C calibrated calendar years before present), as inferred from an increase of Betula pollen percentages from << 5% to >> 20% with associated decreases in Cyperaceae, Poaceae, and Artemisia. At c. 13 000 cal BP, a decrease of Betula pollen from 28 to << 5% suggests that shrub tundra reverted to herb tundra. Shrub tundra replaced herb tundra to resume as the dominant vegetation at 11 600 cal BP. Higher OC% and BSiO2% values suggest more stable soils and higher aquatic productivity during shrub‐tundra periods than during herb‐tundra periods, although pollen changes lagged behind changes in the biogeochemical indicators before c. 13 000 cal BP. Comparison of our palaeoecological data with the ice‐core dδ18O record from Greenland reveals strikingly similar patterns from the onset through the termination of the Younger Dryas (YD). This similarity supports the hypothesis that, as in the North Atlantic region, pronounced YD climatic oscillations occurred in the North Pacific region. The rapidity and magnitude of ecological changes at the termination of the YD are consistent with greenhouse experiments and historic photographs demonstrating tundra sensitivity to climatic forcing. 相似文献
69.
70.
Jian-Guo Huang Yaling Zhang Minhuang Wang Xiaohan Yu Annie Deslauriers Patrick Fonti Eryuan Liang Harri Mäkinen Walter Oberhuber Cyrille B. K. Rathgeber Roberto Tognetti Václav Treml Bao Yang Lihong Zhai Jiao-Lin Zhang Serena Antonucci Yves Bergeron Jesus Julio Camarero Filipe Campelo Katarina Čufar Henri E. Cuny Martin De Luis Marek Fajstavr Alessio Giovannelli Jožica Gričar Andreas Gruber Vladimír Gryc Aylin Güney Tuula Jyske Jakub Kašpar Gregory King Cornelia Krause Audrey Lemay Feng Liu Fabio Lombardi Edurne Martinez del Castillo Hubert Morin Cristina Nabais Pekka Nöjd Richard L. Peters Peter Prislan Antonio Saracino Vladimir V. Shishov Irene Swidrak Hanuš Vavrčík Joana Vieira Qiao Zeng Yu Liu Sergio Rossi 《Global Change Biology》2023,29(6):1606-1617
Despite growing interest in predicting plant phenological shifts, advanced spring phenology by global climate change remains debated. Evidence documenting either small or large advancement of spring phenology to rising temperature over the spatio-temporal scales implies a potential existence of a thermal threshold in the responses of forests to global warming. We collected a unique data set of xylem cell-wall-thickening onset dates in 20 coniferous species covering a broad mean annual temperature (MAT) gradient (−3.05 to 22.9°C) across the Northern Hemisphere (latitudes 23°–66° N). Along the MAT gradient, we identified a threshold temperature (using segmented regression) of 4.9 ± 1.1°C, above which the response of xylem phenology to rising temperatures significantly decline. This threshold separates the Northern Hemisphere conifers into cold and warm thermal niches, with MAT and spring forcing being the primary drivers for the onset dates (estimated by linear and Bayesian mixed-effect models), respectively. The identified thermal threshold should be integrated into the Earth-System-Models for a better understanding of spring phenology in response to global warming and an improved prediction of global climate-carbon feedbacks. 相似文献