scholarly journals Chironomids can be reliable proxies for Holocene temperatures. A comment on Velle et al. (2010)

The Holocene ◽  
2012 ◽  
Vol 22 (12) ◽  
pp. 1495-1500 ◽  
Author(s):  
Stephen J Brooks ◽  
Yarrow Axford ◽  
Oliver Heiri ◽  
Peter G Langdon ◽  
Isabelle Larocque-Tobler
Keyword(s):  
Air Temperature ◽  
Environmental Variables ◽  
Inference Models ◽  
Ecological Complexity ◽  
Temperature Inference

Velle et al. (2010) discussed discrepancies between Scandinavian Holocene chironomid-inferred temperature estimates, which they attribute to the response of chironomids to environmental variables other than temperature and to taxonomic shortcomings. They suggest ways in which the reliability of chironomid-based paleotemperature reconstructions could be improved by taking into account ecological complexity. While we agree with many of their recommendations, based on the results of other work, we think their paper is unnecessarily pessimistic regarding the ability of existing chironomid-based temperature inference models to provide reliable estimates of past temperature. We offer a critique of the main points discussed by Velle et al. (2010) and provide evidence that chironomid-based temperature inference models can reliably reconstruct mean July air temperature in the Lateglacial and Holocene over millennial and centennial timescales.

scholarly journals Driving Forces of Circum-Antarctic Glacier and Ice Shelf Front Retreat over the Last Two Decades

2020 ◽  
Author(s):  
Celia A. Baumhoer ◽  
Andreas J. Dietz ◽  
Christof Kneisel ◽  
Heiko Paeth ◽  
Claudia Kuenzer
Keyword(s):  
Sea Ice ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Air Temperature ◽  
Environmental Variables ◽  
Sea Surface ◽  
Ice Shelf ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
The Antarctic

Abstract. The safety band of Antarctica consisting of floating glacier tongues and ice shelves buttresses ice discharge of the Antarctic Ice Sheet. Recent disintegration events of ice shelves and glacier retreat indicate a weakening of this important safety band. Predicting calving front retreat is a real challenge due to complex ice dynamics in a data-scarce environment being unique for each ice shelf and glacier. We explore to what extent easy to access remote sensing and modelling data can help to define environmental conditions leading to calving front retreat. For the first time, we present a circum-Antarctic record of glacier and ice shelf front retreat over the last two decades in combination with environmental variables such as air temperature, sea ice days, snowmelt, sea surface temperature and wind direction. We find that the Antarctic ice sheet area shrank 29,618 ± 29 km2 in extent between 1997–2008 and gained an area of 7,108 ± 144.4 km2 between 2009 and 2018. Retreat concentrated along the Antarctic Peninsula and West Antarctica including the biggest ice shelves Ross and Ronne. Glacier and ice shelf retreat comes along with one or several changes in environmental variables. Decreasing sea ice days, intense snow melt, weakening easterlies and relative changes in sea surface temperature were identified as enabling factors for retreat. In contrast, relative increases in air temperature did not correlate with calving front retreat. To better understand drivers of glacier and ice shelf retreat it is of high importance to analyse the magnitude of basal melt through the intrusion of warm Circumpolar Deep Water (CDW) driven by strengthening westerlies and to further assess surface hydrology processes such as meltwater ponding, runoff and lake drainage.

scholarly journals Model Simulation of Cucumber Yield and Microclimate Analysis in a Semi-closed Greenhouse in China

HortScience ◽  
2019 ◽  
Vol 54 (3) ◽  
pp. 547-554 ◽  
Author(s):  
Xiaotao Ding ◽  
Yuping Jiang ◽  
Dafeng Hui ◽  
Lizhong He ◽  
Danfeng Huang ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Environmental Variables ◽  
Regression Models ◽  
Model Simulation ◽  
High Yield ◽  
Total Radiation ◽  
Greenhouse Climate ◽  
Yield Forecast ◽  
Cucumber Yield

Adequate greenhouse environmental management is very important for improving resource use efficiency and increasing vegetable yield. The objective of this study was to explore suitable climate and cultivation management for cucumber to achieve high yield and build optimal yield models in semi-closed greenhouses. A fruit cucumber cultivar Deltastar was grown over 4 years in greenhouse and weekly data of yields (mean, highest and lowest) and environmental variables, including total radiation, air temperature, relative humidity, and carbon dioxide (CO2) concentration were collected. Regression analyses were applied to develop the relationships and build best regression models of yields with environmental variables using the first 2 years of data. Data collected in years 3 and 4 were used for model validation. Results showed that total radiation, nutrient, temperature, CO2 concentration, and average nighttime relative humidity had significant correlations with cucumber yields. The best regression models fit the mean, lowest, and highest yields very well with R2 values of 0.67, 0.66, and 0.64, respectively. Total radiation and air temperature had the most significant contributions to the variations of the yields. Our results of this study provide useful information for improving greenhouse climate management and yield forecast in semi-closed greenhouses.

Factors influencing the distribution of chironomids in lakes distributed along a latitudinal gradient in northwestern Quebec, Canada

2006 ◽  
Vol 63 (6) ◽  
pp. 1286-1297 ◽  
Author(s):  
Isabelle Larocque ◽  
Reinhard Pienitz ◽  
Nicolas Rolland
Keyword(s):  
Air Temperature ◽  
Latitudinal Gradient ◽  
Coefficient Of Determination ◽  
Lake Depth ◽  
Partial Least Squares Analysis ◽  
Inference Models ◽  
Temperature Changes ◽  
Detrended Canonical Correspondence Analysis ◽  
Effects Of Temperature ◽  
The One

The effect of 33 environmental variables on the distribution of chironomids was studied in 60 lakes of northwestern Quebec (Canada). A detrended canonical correspondence analysis detected linearity in the chironomid assemblages, thus redundancy analysis was used to identify the variables affecting the chironomid communities. Lake depth, dissolved organic carbon (DOC), mean August air temperature, and surface water temperature were the four variables that best explained the distribution of chironomids. Partial least squares analysis was used to develop new inference models. Among models, the one for mean August air temperature had the highest coefficient of determination (r[Formula: see text] = 0.67) and the lowest root mean square error of prediction (= 1.17 °C). The results indicated that for downcore temperature reconstructions, it might be hard to dissociate the combined effects of temperature, DOC, and depth. Changes in taxa such as Heterotrissocladius brundini-type, Heterotrissocladius subpilosus-type, Heterotrissocladius grimshawi-type, Micropsectra radialis-type, Tanytarsus lugens-type, and Microtendipes can be attributed to changes in lake depth and (or) temperature. Changes in Heterotanytarsus, Dicrotendipes, Cryptotendipes, and Cryptochironomus might be attributed to shifts in temperature and DOC. Relationships among temperature, DOC, and lake depth should be studied in a "neo-ecology" design to better understand their impact on chironomid assemblage composition.

scholarly journals Biogeography and ecology of freshwater chrysophyte cysts in Finland

Hydrobiologia ◽  
2019 ◽  
Vol 847 (2) ◽  
pp. 487-499 ◽  
Author(s):  
Sanna Korkonen ◽  
Jan Weckström ◽  
Atte Korhola
Keyword(s):  
Electrical Conductivity ◽  
Air Temperature ◽  
Environmental Variables ◽  
Principal Component ◽  
Sediment Samples ◽  
Chrysophyte Cysts ◽  
Air Temperatures ◽  
Water Ph ◽  
Good Potential ◽  
Chrysophyte Cyst

Abstract The occurrence of various chrysophyte cyst morphotypes is unknown in Finland, with the exception of a few isolated lake studies. We set out to chart which cyst types are found in Finland and what their ecological preferences are, focusing on cyst-air temperature relationships that could be further utilized in reconstructing past winter/spring air temperatures and ice-free periods from sedimentary cyst assemblages. Surface sediment samples from lakes across Finland were analysed for their chrysophyte stomatocyst assemblages. Multivariate ecological techniques (e.g. canonical correspondence analysis, principal component analysis) were used to identify the environmental variables that most strongly affected the distribution of the cysts. This survey expanded the known geographical range for several cyst types. Lake water pH and ice-free periods (surrogate for air temperature) explained the statistically significant distribution and composition of the cyst assemblages studied. The results broaden our knowledge of cyst biogeography and strengthen the findings of previous studies of the environmental factors contributing to the occurrence of cysts. Highly variable and rich chrysophyte cyst assemblages in Finland are clearly associated with temperature, pH, electrical conductivity and total phosphorus, with good potential in contemporary and retrospective environmental assessment.

scholarly journals Phytoplankton in relation to water quality of Tanguar Haor ecosystem, Bangladesh: I. Rauar station

2019 ◽  
Vol 28 (2) ◽  
pp. 131-138
Author(s):  
Mohammad Azmal Hossain Bhuiyan ◽  
SAM Shariar Islam ◽  
Abu Kowser ◽  
Md Rasikul Islam ◽  
Shahina Akter Kakoly ◽  
...  
Keyword(s):  
Water Quality ◽  
Air Temperature ◽  
Environmental Variables ◽  
Secchi Depth ◽  
Soluble Reactive Phosphorus ◽  
Organic Pollution ◽  
Quality Data ◽  
Water Quality Data ◽  
Chl A ◽  
Reactive Phosphorus

The water quality at Rauar station of Tanguar Haor, Sunamganj was assessed studying phytoplankton and associated environmental variables. The environmental variables were monitored over a period of one year, collecting samples at two months interval between March, 2017 and March, 2018. Air temperature, rainfall, and humidity ranged from 22.6 - 32.1°C, 48 - 76% and 8 - 930 mm, respectively. Air temperature showed a direct relationship with water temperature which varied from 22.4 - 31.0°C during the study period. The water transparency remained relatively constant throughout the year having a mean Secchi depth (Zs) value of 2.48 m. Total dissolved solids (TDS), conductivity, and pH of the water ranged from 51 - 85 mg/l, 60 - 110 μS/cm, and 7.2 - 9.7, respectively. In December, because of a temperature fall, the dissolved oxygen (DO) concentration of the water reached its maximum value of 6.09 mg/l. In the rest of the period, the concentration remained between 2.44 and 4.80 mg/l. The value of alkalinity ranged from 0.43 - 1.35 meq/l. Among the nutrients, soluble reactive phosphorus (SRP), soluble reactive silicate (SRS), and NO3-N ranged from 5.43 - 36.43 μg/l, 4 - 14.58 mg/l, and 0.06 - 0.31 mg/l, respectively. The concentration of NH4+ ranged from 238 - 1230 μg/l. The highest concentrations (905 and 1230 μg/l) occurred between September and December, 2017. This might be attributed to the higher density of migratory birds during that period. The phytoplanktonic biomass expressed as chlorophyll-a (Chl-a) ranged from 1.35 - 8.45 μg/l while its degraded product phaeophytin concentration ranged from 0.08 - 3.5 μg/l. The standing crop of phytoplankton ranged from 397 - 2480 × 103 individuals/l of haor water exhibiting its maximum abundance in September. This parameter showed a highly significant positive correlation with SRP. From the correlation analysis, the degradation of chl-a to phaeophytin was found to be temperature dependent. Considering the different physicochemical and biological water quality data, it could be said that the Tanguar Haor is still free from organic pollution. However, the range of soluble reactive phosphorus data (5.43 - 36.43 μg/l) show that the Haor has been passing a meso-eutrophic state. Dhaka Univ. J. Biol. Sci. 28(2): 131-138, 2019 (July)

scholarly journals MODELING THE GROWTH OF EUCALYPTUS PLANTS BASED ON THE THERMAL SUM

2017 ◽  
Vol 41 (2) ◽  
Author(s):  
Aline Santana de Oliveira ◽  
Aristides Ribeiro ◽  
Carla Raphaela Araújo Silva ◽  
Aloísio Xavier ◽  
Alex Ferreira de Freitas
Keyword(s):  
Air Temperature ◽  
Environmental Variables ◽  
Growth And Development ◽  
Production Cycle ◽  
Forest Research ◽  
Degree Days ◽  
Shoot Height ◽  
Dry Biomass ◽  
Thermal Sum ◽  
Accumulated Degree Days

ABSTRACT Among the environmental variables that affect the growth and development of plants, the air temperature is of great importance. In this context, the objectives of this work were to model the growth of eucalyptus seedlings in terms of accumulated degree-days during the production process and model validation. The study was conducted in the forest research nursery of the Department of Forestry, located in Viçosa (MG), during the periods of 08/02/2011 to 28/04/2011 and 03/08/2012 to 01/11/2012, making it possible to contemplate seasonal variations in the production cycle. The monitored variables were shoot height, stem diameter, leaf area, root length and fresh and dry biomass. Results showed that it took 1065 degree-days for the production of seedlings and sigmoidal models obtained showed high correlation and Willmott coefficients, indicating good performance for estimating the growth and development of eucalyptus seedlings. This tool has great potential for planning and monitoring the production of eucalyptus seedlings in nurseries.

Stomatal Responses to Environmental Variables in Shade and Sun Grown Coffee Plants in Mexico

1985 ◽  
Vol 21 (3) ◽  
pp. 249-258 ◽  
Author(s):  
Luis Fanjul ◽  
R. Arreola-Rodriguez ◽  
M. P. Mendez-Castrejon
Keyword(s):  
Stomatal Conductance ◽  
Air Temperature ◽  
Environmental Conditions ◽  
Vapour Pressure ◽  
Environmental Variables ◽  
Vapour Pressure Deficit ◽  
Net Photosynthesis ◽  
Stomatal Movement ◽  
Stomatal Responses ◽  
Coffee Plants

SUMMARYThe influence of air temperature (T), vapour pressure deficit (vpd), irradiance (Q) and leaf water potential (ψ) on diurnal stomatal movement of coffee plants was examined under field and controlled environmental conditions. Leaves of plants grown under shade had larger stomatal conductance (g) values than plants grown in open sun. Stomatal responses to vpd under constant temperature conditions were very strong, indicating that ambient humidity could play a major role in controlling stomatal aperture. Changes in g as vpd increased probably contributed to observed reductions in the rate of net photosynthesis (Pn), though the effect of vpd on Pn was smaller.

scholarly journals Soil mite communities (Acari: Mesostigmata) as indicators of urban ecosystems in Bucharest, Romania

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Manu ◽  
R. I. Băncilă ◽  
C. C. Bîrsan ◽  
O. Mountford ◽  
M. Onete
Keyword(s):  
Air Temperature ◽  
Soil Ph ◽  
Environmental Variables ◽  
Penetration Resistance ◽  
Soil Core ◽  
Urban Green ◽  
Soil Penetration Resistance ◽  
Green Areas ◽  
Soil Mite ◽  
Mite Communities

AbstractThe aim of the present study was to establish the effect of management type and of environmental variables on the structure, abundance and species richness of soil mites (Acari: Mesostigmata) in twelve urban green areas in Bucharest-Romania. Three categories of ecosystem based upon management type were investigated: protected area, managed (metropolitan, municipal and district parks) and unmanaged urban areas. The environmental variables which were analysed were: soil and air temperature, soil moisture and atmospheric humidity, soil pH and soil penetration resistance. In June 2017, 480 soil samples were taken, using MacFadyen soil core. The same number of measures was made for quantification of environmental variables. Considering these, we observed that soil temperature, air temperature, air humidity and soil penetration resistance differed significantly between all three types of managed urban green area. All investigated environmental variables, especially soil pH, were significantly related to community assemblage. Analysing the entire Mesostigmata community, 68 species were identified, with 790 individuals and 49 immatures. In order to highlight the response of the soil mite communities to the urban conditions, Shannon, dominance, equitability and soil maturity indices were quantified. With one exception (numerical abundance), these indices recorded higher values in unmanaged green areas compared to managed ecosystems. The same trend was observed between different types of managed green areas, with metropolitan parks having a richer acarological fauna than the municipal or district parks.

scholarly journals Daily Tall Fescue Leaf Appearance Rate in Relation to Environmental Factors

HortScience ◽  
1991 ◽  
Vol 26 (2) ◽  
pp. 114-117 ◽  
Author(s):  
L.B. McCarty ◽  
J.R. Haun ◽  
L.C. Miller
Keyword(s):  
Solar Radiation ◽  
Air Temperature ◽  
Tall Fescue ◽  
Festuca Arundinacea ◽  
Environmental Variables ◽  
Cultural Practices ◽  
Appearance Rate ◽  
Leaf Appearance Rate ◽  
Leaf Appearance ◽  
Maximum Air Temperature

Methods for detecting and mathematically regressing daily tall fescue (Festuca arundinacea Schreb.) leaf appearance on environmental variables are presented. Morphological stages of leaf development were quantified and the rate of leaf appearance was linearly regressed on environmental variables. The following model was developed to predict daily tall fescue leaf appearance and was successfully tested on unrelated data: Daily leaf appearance rate = 0.016 – (2.48 × 10-4 × solar radiation) + (0.015 × precipitation 2-day lag) + (0.117 × soil moisture 3-day lag) + (8.79 × 1 0-6 × maximum air temperature × solar radiation) - (3.61 × 10-' × maximum air temperature × age) + (0.00307 × minimum air temperature × precipitation) – (4.39 × 10-4 × precipitation × age), (R2 = 0.78). Growers of tall fescue and researchers will benefit in the identification of environmental characteristics and cultural practices that significantly influence leaf appearance rate.

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