Microsite conditions and spatial pattern in a boreal bryophyte community

1995 ◽  
Vol 73 (4) ◽  
pp. 544-551 ◽  
Author(s):  
Katherine A. Frego ◽  
Terry J. Carleton
Keyword(s):  
Spatial Pattern ◽  
Photosynthetically Active Radiation ◽  
Vapour Pressure ◽  
Full Range ◽  
Habitat Partitioning ◽  
Pleurozium Schreberi ◽  
Species Variation ◽  
Litter Fall ◽  
Active Radiation ◽  
Dicranum Polysetum

This study addresses the hypothesis that the spatial pattern of four bryophyte species on the forest floor of boreal woodland represents habitat partitioning, corresponding to microhabitat heterogeneity. Temperature, vapour pressure deficit, photosynthetically active radiation, incident precipitation, and litter fall were monitored at locations of pure colonies of Pleurozium schreberi, Ptilium crista-castrensis, Dicranum polysetum, and Ptilidium ciliare. From May through November 1990, the species received a mean total of 51.20 ± 1.09 cm of rain and 1.034 ± 0.639 g of litter, primarily spruce needles. They experienced temperatures as high as 40 °C, vapour pressure deficits to 7.3 kPa, and photosynthetically active radiation to 3200 μmol∙m−2∙s−1. The results do not support habitat partitioning by the species on the basis of the variables examined: all four species tolerated the full range of conditions and their combinations that occurred in the study season, and experienced the same ranges during > 90% of the sampling period, with equally broad within-species variation. Although large pure colonies of P. ciliare were delimited by microsites receiving greater spruce needle litter fall and lower incident precipitation per rainfall event, smaller colonies and individual shoots were often found in mixture with other species. Overall, the spatial pattern did not correlate with microsite conditions, and we see no evidence of habitat partitioning in terms of currently occupied microsites. Key words: community structure, microclimate, Pleurozium schreberi, Ptilium crista-castrensis, Dicranum polysetum, Ptilidium ciliare.

Gas exchange processes of yellow-cedar (Chamaecyparis nootkatensis) in response to environmental variables

1991 ◽  
Vol 69 (12) ◽  
pp. 2684-2691 ◽  
Author(s):  
Steven C. Grossnickle ◽  
John H. Russell
Keyword(s):  
Stomatal Conductance ◽  
Response Surface ◽  
Photosynthetically Active Radiation ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Surface Model ◽  
Root Temperature ◽  
Active Radiation ◽  
Chamaecyparis Nootkatensis ◽  
Exchange Processes

Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) gas exchange processes were measured in response to the following primary environmental variables: photosynthetically active radiation, vapour pressure deficit, root temperature, and soil moisture. Under nonlimiting edaphic conditions, maximum stomatal conductance and maximum CO2 assimilation increased rapidly as photosynthetically active radiation increased from 0 to 200 μmol∙m−2∙s−1 and from 0 to 500 μmol∙m−2∙s−1, respectively. Thereafter, greater photosynthetically active radiation levels only resulted in minor increases in stomatal conductance and CO2 assimilation. Maximum stomatal conductance and maximum CO2 assimilation declined in a concave manner as vapour pressure deficit increased from 1 to 5 kPa. Response surface model for stomatal conductance showed vapour pressure deficit was the primary influence after light had caused initial stomatal opening. Response surface modeling approach showed CO2 assimilation increased as photosynthetically active radiation increased, but increased vapour pressure deficit resulted in a suppression of CO2 assimilation. Response surface model showed internal CO2 concentration declined sharply as photosynthetically active radiation increased from 0 to 500 μmol∙m−2∙s−1, but it remained constant with increasing vapour pressure deficit. Decreasing root temperature resulted in a continual decline in CO2 assimilation and stomatal conductance from 22 to 1 °C, while internal CO2 concentration declined from 22 to 13 °C with little change between 13 and 1 °C. As predawn shoot water potential decreased from −0.5 to −2.0 MPa, CO2 assimilation declined in a linear manner, while stomatal conductance and internal CO2 concentration declined in a concave manner. Key words: Chamaecyparis nootkatensis, CO2 assimilation, stomatal conductance, internal CO2 concentration, photosynthetically active radiation, vapour pressure deficit, root temperature, predawn shoot water potential.

Relationship between Photosynthetic Rate and Stomatal Conductance, Intercellular CO2 Concentration, Transpiration Rate, Vapour Pressure Deficit and Photosynthetically Active Radiation in Sweet Corn (Zea mays)

2020 ◽  
Vol 1 (2) ◽  
Author(s):  
Aidee Kamal Khamis ◽  
◽  
Umi Aisah Asli ◽  
Mohd Nadzreen Hidaya Sarjuni ◽  
Mohd Azlan Jalal ◽  
...  
Keyword(s):  
Zea Mays ◽  
Stomatal Conductance ◽  
Photosynthetic Rate ◽  
Transpiration Rate ◽  
Photosynthetically Active Radiation ◽  
Vapour Pressure ◽  
Sweet Corn ◽  
Vapour Pressure Deficit ◽  
Active Radiation ◽  
Development Stages

Sweet corn (Zea mays) is thethird-largest plantation crop in Malaysia. Since it is cultivated mainly for the corncobs, the reproductive and kernel development stages are critical for high yields. Photosynthesis measurement can be used as a major approach to improve photosynthetic efficiency, which can directly affect yield. Additionally, plant nutrient uptake also plays a major role in yield quantity and quality. Conventional fertilisation(chemical and/or organic) may result in excessive fertilizer input, which is detrimental to the environment. We therefore investigated the relationship between photosynthetic rate and stomatal conductance (gs), intercellular CO2concentration (Ci), transpiration rate and vapour pressure deficit based on leaf temperature (VpdL) and photosynthetically active radiation (PAR) during the growth and development stages of sweet corn. The seeds were subjected to the germination test to assess viability and were then planted at a distance of 10 cm both between plantsand rows (replicates). A total of eight subplots (2.2 m long, 60 cm wide, 30 cm high) were prepared in a randomized complete block design (RCBD). Leaf gas exchange measurements were carried out at days 10, 20, 30, 40, 50 and 60 at 9:00 a.m. in the morning and 4:00 p.m. in the evening. Three uniform plants were selected from each replicate and used for measurements throughout the experiment. At day 30, photosynthesis started to decline and was largely unaffected by the set environmental conditions, although stomatal conductance remained high. This can be attributed to the energy diversion from vegetative stages to reproductive stages. Therefore, fertilising practices should be synchronised to match the plant stages for more sustainable and efficient fertilisation and to obtain maximum yield.

scholarly journals A microbiota–root–shoot circuit favours Arabidopsis growth over defence under suboptimal light

Nature Plants ◽  
2021 ◽  
Author(s):  
Shiji Hou ◽  
Thorsten Thiergart ◽  
Nathan Vannier ◽  
Fantin Mesny ◽  
Jörg Ziegler ◽  
...  
Keyword(s):  
Stress Responses ◽  
Photosynthetically Active Radiation ◽  
Bacterial Community Composition ◽  
Light Condition ◽  
Long Distance ◽  
Active Radiation ◽  
Light Manipulation ◽  
Growth Deficiency ◽  
Dependent Growth ◽  
Control Light

AbstractBidirectional root–shoot signalling is probably key in orchestrating stress responses and ensuring plant survival. Here, we show that Arabidopsis thaliana responses to microbial root commensals and light are interconnected along a microbiota–root–shoot axis. Microbiota and light manipulation experiments in a gnotobiotic plant system reveal that low photosynthetically active radiation perceived by leaves induces long-distance modulation of root bacterial communities but not fungal or oomycete communities. Reciprocally, microbial commensals alleviate plant growth deficiency under low photosynthetically active radiation. This growth rescue was associated with reduced microbiota-induced aboveground defence responses and altered resistance to foliar pathogens compared with the control light condition. Inspection of a set of A. thaliana mutants reveals that this microbiota- and light-dependent growth–defence trade-off is directly explained by belowground bacterial community composition and requires the host transcriptional regulator MYC2. Our work indicates that aboveground stress responses in plants can be modulated by signals from microbial root commensals.

scholarly journals Intercepted Photosynthetically Active Radiation (PAR) and Spatial and Temporal Distribution of Transmitted PAR under High-Density and Super High-Density Olive Orchards

Agriculture ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 351
Author(s):  
Adolfo Rosati ◽  
Damiano Marchionni ◽  
Dario Mantovani ◽  
Luigi Ponti ◽  
Franco Famiani
Keyword(s):  
Spatial Variability ◽  
Photosynthetically Active Radiation ◽  
Temporal Distribution ◽  
High Density ◽  
Radiation Use Efficiency ◽  
Spatial And Temporal Distribution ◽  
Active Radiation ◽  
Use Efficiency ◽  
And Performance ◽  
Radiation Use

We quantified the photosynthetically active radiation (PAR) interception in a high-density (HD) and a super high-density (SHD) or hedgerow olive system, by measuring the PAR transmitted under the canopy along transects at increasing distance from the tree rows. Transmitted PAR was measured every minute, then cumulated over the day and the season. The frequencies of the different PAR levels occurring during the day were calculated. SHD intercepted significantly but slightly less overall PAR than HD (0.57 ± 0.002 vs. 0.62 ± 0.03 of the PAR incident above the canopy) but had a much greater spatial variability of transmitted PAR (0.21 under the tree row, up to 0.59 in the alley center), compared to HD (range: 0.34–0.43). This corresponded to greater variability in the frequencies of daily PAR values, with the more shaded positions receiving greater frequencies of low PAR values. The much lower PAR level under the tree row in SHD, compared to any position in HD, implies greater self-shading in lower-canopy layers, despite similar overall interception. Therefore, knowing overall PAR interception does not allow an understanding of differences in PAR distribution on the ground and within the canopy and their possible effects on canopy radiation use efficiency (RUE) and performance, between different architectural systems.

scholarly journals Estimation of Incident Photosynthetically Active Radiation from GOES Visible Imagery

2008 ◽  
Vol 47 (3) ◽  
pp. 853-868 ◽  
Author(s):  
Tao Zheng ◽  
Shunlin Liang ◽  
Kaicun Wang
Keyword(s):  
Photosynthetically Active Radiation ◽  
Terrestrial Ecosystem ◽  
New Method ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
Ecosystem Models ◽  
Surface Conditions ◽  
Active Radiation ◽  
Ground Measurement ◽  
Visible Imagery

Abstract Incident photosynthetically active radiation (PAR) is an important parameter for terrestrial ecosystem models. Because of its high temporal resolution, the Geostationary Operational Environmental Satellite (GOES) observations are very suited to catch the diurnal variation of PAR. In this paper, a new method is developed to derive PAR using GOES data. What makes this new method distinct from the existing method is that it does not need external knowledge of atmospheric conditions. The new method retrieves both atmospheric and surface conditions using only at-sensor radiance through interpolation of time series of observations. Validations against ground measurement are carried out at four “FLUXNET” sites. The values of RMSE of estimated and ground-measured instantaneous PAR at the four sites are 130.71, 131.44, 141.16, and 190.22 μmol m−2 s−1, respectively. At the four validation sites, the RMSE as the percentage of estimated mean PAR value are 9.52%, 13.01%, 13.92%, and 24.09%, respectively; the biases are −101.54, 16.56, 11.09, and 53.64 μmol m−2 s−1, respectively. The independence of external atmospheric information enables this method to be applicable to many situations in which external atmospheric information is not available. In addition, topographic impacts on surface PAR are examined at the 1-km resolution at which PAR is retrieved using the GOES visible band data.

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