scholarly journals Multiple resource limitations explain biomass-precipitation relationships in grasslands

2021 ◽  
Author(s):  
Siddharth Bharath ◽  
Peter B. Adler ◽  
Philip A. Fay ◽  
Eric W. Seabloom ◽  
Yann Hautier ◽  
...  
Keyword(s):  
Nutrient Availability ◽  
Nutrient Addition ◽  
Plant Performance ◽  
Resource Limitations ◽  
Herbivore Exclusion ◽  
Grassland Ecosystems ◽  
Proportional Change ◽  
Increased Sensitivity ◽  
Multiple Resource ◽  
A Site

AbstractInterannual variability in grassland primary production is strongly driven by precipitation, nutrient availability and herbivory, but there is no general consensus on the mechanisms linking these variables. If grassland biomass is limited by the single most limiting resource at a given time, then we expect that nutrient addition will not affect biomass production at arid sites. We conducted a distributed experiment manipulating nutrients and herbivores at 44 grassland sites in 8 regions around the world, spanning a broad range in aridity. We estimated the effects of 5-11 years of nutrient addition and herbivore exclusion treatments on precipitation sensitivity of biomass (proportional change in biomass relative to proportional change in rainfall among years), and the biomass in the driest year (to measure treatment effects when water was most limiting) at each site. Grazer exclusion did not interact with nutrients to influence driest year biomass or sensitivity. Nutrient addition increased driest year biomass by 74% and sensitivity by 0.12 (proportional units), and that effect did not change across the range of aridity spanned by our sites. Grazer exclusion did not interact with nutrients to influence sensitivity or driest year biomass. At almost half of our sites, the previous year's rainfall explained as much variation in biomass as current year precipitation. Overall, our distributed fertilization experiment detected co-limitation between nutrients and water governing grasslands, with biomass sensitivity to precipitation being limited by nutrient availability irrespective of site aridity and herbivory. Our findings refute the classical ideas that grassland plant performance is limited by the single most limiting resource at a site. This suggests that nutrient eutrophication will destabilize grassland ecosystems through increased sensitivity to precipitation variation.

scholarly journals Different Roles of Top-Down and Bottom-Up Processes in the Distribution of Size-Fractionated Phytoplankton in Gwangyang Bay

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1682
Author(s):  
Yoonja Kang ◽  
Yeongji Oh
Keyword(s):  
Nutrient Availability ◽  
Fast Response ◽  
Nutrient Addition ◽  
The Other ◽  
Zooplankton Grazing ◽  
Top Down ◽  
Bottom Up ◽  
Phytoplankton Distribution ◽  
Summer Bloom ◽  
Gwangyang Bay

The interactive roles of zooplankton grazing (top-down) and nutrient (bottom-up) processes on phytoplankton distribution in a temperate estuary were investigated via dilution and nutrient addition experiments. The responses of size-fractionated phytoplankton and major phytoplankton groups, as determined by flow cytometry, were examined in association with zooplankton grazing and nutrient availability. The summer bloom was attributed to nanoplankton, and microplankton was largely responsible for the winter bloom, whereas the picoplankton biomass was relatively consistent throughout the sampling periods, except for the fall. The nutrient addition experiments illustrated that nanoplankton responded more quickly to phosphate than the other groups in the summer, whereas microplankton had a faster response to most nutrients in the winter. The dilution experiments ascribed that the grazing mortality rates of eukaryotes were low compared to those of the other groups, whereas autotrophic cyanobacteria were more palatable to zooplankton than cryptophytes and eukaryotes. Our experimental results indicate that efficient escape from zooplankton grazing and fast response to nutrient availability synergistically caused the microplankton to bloom in the winter, whereas the bottom-up process (i.e., the phosphate effect) largely governed the nanoplankton bloom in the summer.

scholarly journals Differences in growth-economics of fast vs. slow growing grass species in response to temperature and nitrogen limitation individually, and in combination

BMC Ecology ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Claudia Colesie ◽  
Zsofia Reka Stangl ◽  
Vaughan Hurry
Keyword(s):  
Nutrient Availability ◽  
Nitrogen Availability ◽  
Global Environmental Change ◽  
Performance Outcomes ◽  
Plant Performance ◽  
Grass Species ◽  
Growth Responses ◽  
Fast Growing ◽  
Environment Temperature ◽  
Slow Growing

Abstract Background Fast growing invasive alien species are highly efficient with little investment in their tissues. They often outcompete slower growing species with severe consequences for diversity and community composition. The plant economics trait-based approach provides a theoretical framework, allowing the classification of plants with different performance characteristics. However, in multifaceted background, this approach needs testing. The evaluation and prediction of plant performance outcomes in ecologically relevant settings is among the most pressing topics to understand and predict ecosystem functioning, especially in a quickly changing environment. Temperature and nutrient availability are major components of the global environmental change and this study examines the response of growth economic traits, photosynthesis and respiration to such changes for an invasive fast-growing (Bromus hordaceus) and a slow-growing perennial (Bromus erectus) grass species. Results The fully controlled growth chamber experiment simulated temperature—and changes in nitrogen availability individually and in combination. We therefore provide maximum control and monitoring of growth responses allowing general growth trait response patterns to be tested. Under optimal nitrogen availability the slow growing B. erectus was better able to handle the lower temperatures (7 °C) whilst both species had problems at higher temperatures (30 °C). Stresses produced by a combination of heat and nutrient availability were identified to be less limiting for the slow growing species but the combination of chilling with low nutrient availability was most detrimental to both species. Conclusions For the fast-growing invader B. hordeaceus a reduction of nitrogen availability in combination with a temperature increase, leads to limited growth performance in comparison to the slow-growing perennial species B.erectus and this may explain why nutrient-rich habitats often experience more invasion than resource-poor habitats.

Rapid adjustment of leaf angle explains how the desert moss, Syntrichia caninervis, copes with multiple resource limitations during rehydration

2014 ◽  
Vol 41 (2) ◽  
pp. 168 ◽  
Author(s):  
Nan Wu ◽  
Yuan-ming Zhang ◽  
Alison Downing ◽  
Zachary T. Aanderud ◽  
Ye Tao ◽  
...  
Keyword(s):  
Light Availability ◽  
Morphological Characters ◽  
Ultrastructural Changes ◽  
Leaf Angle ◽  
Resource Limitations ◽  
Syntrichia Caninervis ◽  
Relative Water ◽  
Rapid Adjustment ◽  
Multiple Resource ◽  
Water Gain

Although the desert moss Syntrichia caninervis Mitt. is extremely desiccation tolerant, it still requires water and photosynthates for growth. The ecological significance of the leaf angle in maintaining a balance between water and light availability is critical to its survival. Active leaf repositioning balances water and light availability following rehydration. S. caninervis can adjust leaf angles from a steep (84–69°) to a stable level at 30° within 7 s after rehydration, obtaining maximum net photosynthetic gain at a shoot relative water content of ~60%. Leaf morphological characters, (leaf hair points, surface papillae and costal anatomy) and ultrastructural changes (chloroplast reordering and loss of lipid reserves as shown by changes in osmiophilic globules) were linked to rapid leaf spreading, water gain and sunlight reflectivity of leaves during rehydration. The high 377.20 ± 91.69 (cm2 g–1) surface area to mass ratio was a major factor in facilitating the rapid response to rewetting. Hyaline cells of the leaf base absorbed water, swelled and forced the leaf away from the stem as soon as rehydration commenced. Loss of leaf hair points retards leaf angle adjustment during rehydration.

scholarly journals Reversion of the M184V Mutation in Simian Immunodeficiency Virus Reverse Transcriptase Is Selected by Tenofovir, Even in the Presence of Lamivudine

2003 ◽  
Vol 77 (2) ◽  
pp. 1120-1130 ◽  
Author(s):  
Jeffrey P. Murry ◽  
Joanne Higgins ◽  
Timothy B. Matthews ◽  
Victoria Y. Huang ◽  
Koen K. A. Van Rompay ◽  
...  
Keyword(s):  
Reverse Transcriptase ◽  
Simian Immunodeficiency Virus ◽  
Rhesus Macaques ◽  
Serial Passage ◽  
K65r Mutation ◽  
Immunodeficiency Virus ◽  
Increased Sensitivity ◽  
A Site ◽  
Emergence Of Resistance ◽  
M184v Mutation

ABSTRACT The methionine-to-valine mutation in codon 184 (M184V) in reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) or simian immunodeficiency virus (SIV) confers resistance to (−)-2′-deoxy-3′-thiacytidine (3TC; lamivudine) and increased sensitivity to 9-[2-(phosphonomethoxy)propyl]adenine (PMPA; tenofovir). We have used the SIV model to evaluate the effect of the M184V mutation on the emergence of resistance to the combination of 3TC plus PMPA. A site-directed mutant of SIVmac239 containing M184V (SIVmac239-184V) was used to select for resistance to both 3TC and PMPA by serial passage in the presence of increasing concentrations of both drugs. Under these selection conditions, the M184V mutation reverted in the majority of the selections. Variants resistant to both drugs were found to have the lysine-to-arginine mutation at codon 65 (K65R), which has previously been associated with resistance to PMPA in both SIV and HIV. Similarly, in rhesus macaques infected with SIVmac239-184V for 46 weeks and treated daily with (−)-2′-deoxy-5-fluoro-3′-thiacytidine [(−)-FTC], there was no reversion of M184V, but this mutation reverted to 184 M in all three animals within 24 weeks of treatment with (−)-FTC and PMPA. Although the addition of PMPA to the (−)-FTC therapy induced a decrease in virus loads in plasma, these loads eventually returned to pre-PMPA levels in each case. All animals receiving this combination developed the K65R mutation. These results demonstrate that the combination of PMPA with 3TC or (−)-FTC selects for the K65R mutation and against the M184V mutation in SIV RT.

scholarly journals Studies on Aminoglycoside Susceptibility Identify a Novel Function of KsgA To Secure Translational Fidelity during Antibiotic Stress

2018 ◽  
Vol 62 (10) ◽  
Author(s):  
Jin Zou ◽  
Wenwen Zhang ◽  
Hongjie Zhang ◽  
Xiaohua Douglas Zhang ◽  
Bo Peng ◽  
...  
Keyword(s):  
Site Directed Mutagenesis ◽  
Dna Glycosylase ◽  
Cold Sensitivity ◽  
Ribosomal Biogenesis ◽  
Translational Fidelity ◽  
Content Type ◽  
Root Cause ◽  
Increased Sensitivity ◽  
K 12 ◽  
A Site

ABSTRACTAntibiotic resistance has become a global crisis. Studies on the mechanism of bacterial tolerance to antibiotics will not only increase our conceptual understanding of bacterial death but also provide potential targets for novel inhibitors. We screened a mutant library containing a full set of in-frame deletion mutants ofEscherichia coliK-12 and identified 140 genes that possibly contribute to gentamicin tolerance. The deletion ofksgAincreased the inhibition and killing potency against mid-log-phase bacteria by aminoglycosides. Initially identified as a 16S rRNA methyltransferase, KsgA also has additional functions as a ribosomal biogenesis factor and a DNA glycosylase. We found that the methyltransferase activity of KsgA is responsible for the tolerance, as demonstrated by a site-directed mutagenesis analysis. In contrast to the mechanism for cold sensitivity, the decreased tolerance to aminoglycoside is not related to the failure of ribosomal biogenesis. Furthermore, the DNA glycosylase activity of KsgA contributes minimally to kanamycin tolerance. Importantly, we discovered that KsgA secures protein translational fidelity upon kanamycin killing, in contrast to its role during cold stress and kasugamycin treatment. The results suggest that the compromise in protein translational fidelity in the absence of KsgA is the root cause of an increased sensitivity to a bactericidal aminoglycoside. In addition, KsgA in the pathogenicAcinetobacter baumanniicontributes not only to the tolerance against aminoglycoside killing but also to virulence in the host, warranting its potential application as a target for inhibitors that potentiate aminoglycoside therapeutic killing as well as disarm bacterial virulence simultaneously.

Compensatory growth of three herbaceous perennial species: the effects of clipping and nutrient availability

2000 ◽  
Vol 78 (6) ◽  
pp. 759-767 ◽  
Author(s):  
Samantha Hicks ◽  
Roy Turkington
Keyword(s):  
Boreal Forest ◽  
Nutrient Availability ◽  
Soil Nutrient ◽  
Field Studies ◽  
Plant Performance ◽  
Natural Soil ◽  
Fertility Level ◽  
Perennial Species ◽  
Study Sites ◽  
Herbaceous Perennial

The continuum of responses model (CRM) and the growth rate model (GRM) make conflicting predictions about the effects of soil nutrient availability on the resilience of plants to herbivory. A factorial experiment was conducted in the understory of the boreal forest to examine the effects of fertilization and simulated herbivory on the rate and amount of regrowth of three herbaceous perennial species (Achillea millefolium L., Festuca altaica Trin., and Mertensia paniculata (Aiton) G. Don.). As clipping intensity increases various measures of plant performance decrease. Fertilization reduces the ability of clipped plants to compensate for biomass loss regardless of species and growth measure. Under natural soil fertility levels in this study, M. paniculata is more likely to compensate for leaf loss than A. millefolium and F. altaica. Contrary to the findings of previous field studies, the compensatory responses of the three species studied were most consistent with the predictions of the GRM. Plants in our study sites grow in nutrient-poor soils, whereas the majority of compensatory studies have been carried out on herbaceous or woody plants in temperate regions. Resources are generally more abundant in temperate zones than in boreal forest zones, and the GRM may be a better predictor of compensatory ability of plants growing in naturally nutrient-deficient soils.Key words: herbivory, regrowth, fertility level, clipping intensity, compensation.

scholarly journals Low-glutathione mutants are impaired in growth but do not show an increased sensitivity to moderate water deficit

2019 ◽  
Author(s):  
Sajid A.K. Bangash ◽  
David Solbach ◽  
Marcus Jansen ◽  
Fabio Fiorani ◽  
Markus Schwarzländer ◽  
...  
Keyword(s):  
Shoot Growth ◽  
Reduced Glutathione ◽  
Plant Performance ◽  
Water Withdrawal ◽  
Wild Type ◽  
Allelic Series ◽  
Dwarf Phenotype ◽  
Drought Conditions ◽  
Moderate Drought ◽  
Increased Sensitivity

AbstractGlutathione is considered a key metabolite for stress defense and elevated levels have frequently been proposed to positively influence stress tolerance. To investigate whether glutathione affects plant performance and the drought tolerance of plants, wild-type Arabidopsis plants and an allelic series of five mutants (rax1, pad2, cad2, nrc1, and zir1) with reduced glutathione contents between 21 and 63 % compared to wild-type glutathione content were phenotypically characterized for their shoot growth under control and water-limiting conditions using a shoot phenotyping platform. Under non-stress conditions the zir1 mutant with only 21 % glutathione showed a pronounced dwarf phenotype. All other mutants with intermediate glutathione contents up to 62 % in contrast showed consistently slightly smaller shoots than the wild-type. Moderate drought stress imposed through water withdrawal until shoot growth ceased showed that wild-type plants and all mutants responded similarly in terms of chlorophyll fluorescence and growth retardation. These results lead to the conclusion that glutathione is important for general plant performance but that the glutathione content does not affect tolerance to moderate drought conditions typically experienced by crops in the field.

Solar Chimney Power Plant Performance Analysis in the Central Regions of Iran

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
A. Asnaghi ◽  
S. M. Ladjevardi ◽  
A. Haghparast Kashani ◽  
P. Saleh Izadkhast
Keyword(s):  
Power Plant ◽  
Performance Analysis ◽  
Solar Radiation ◽  
Power Plants ◽  
Plant Performance ◽  
Solar Chimney ◽  
Electrical Grid ◽  
Central Regions ◽  
Solar Chimney Power Plant ◽  
A Site

In the current study, the performance analysis of a solar chimney power plant expected to provide off-grid electric power demand for villages located in Iranian central regions is presented. High annual average of solar radiation and available desert lands in the central parts of Iran are factors to encourage the full development of a solar chimney power plant for the thermal and electrical production of energy for various uses. The interested is in Kerman where solar radiation is much better than other areas of Iran. The obtained results clear that solar chimney power plants having 244 m diameter can produce from 25.3 to 43.2 MW h of electricity power on a site like Kerman during different months of a year, according to an estimation calculated from the monthly average of sunning. This power production is sufficient for the needs of the isolated areas and can even used to feed the main electrical grid.

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