Gene expression responses of paper birch (
Betula papyrifera) leaves to elevated concentrations of CO
2 and O
3 were studied with microarray analyses from three time points during the summer of 2004 ...at Aspen FACE. Microarray data were analyzed with clustering techniques, self-organizing maps,
K-means clustering and Sammon's mappings, to detect similar gene expression patterns within sampling times and treatments. Most of the alterations in gene expression were caused by O
3, alone or in combination with CO
2. O
3 induced defensive reactions to oxidative stress and earlier leaf senescence, seen as decreased expression of photosynthesis- and carbon fixation-related genes, and increased expression of senescence-associated genes. The effects of elevated CO
2 reflected surplus of carbon that was directed to synthesis of secondary compounds. The combined CO
2
+
O
3 treatment resulted in differential gene expression than with individual gas treatments or in changes similar to O
3 treatment, indicating that CO
2 cannot totally alleviate the harmful effects of O
3.
Clustering analysis of birch leaf gene expression data reveals differential responses to O
3 and CO
2.
While increased atmospheric CO₂ concentrations, increased N deposition, and changes in plant diversity have all been shown to significantly alter soil carbon (C) and nitrogen (N) dynamics, the ...effects of these factors have never been studied simultaneously and in combination. We studied the response of soil C and N dynamics to changes in atmospheric CO₂ (ambient, 560 ppm), N fertilization (0, 4 g N m⁻² yr⁻¹), plant species number (1, 4 species), and plant functional group number (1, 4 groups; all with 4 species) in a grassland field experiment in Minnesota, USA. During the fourth season of treatments, we used laboratory incubations to assess soil C pool sizes and dynamics and net N mineralization, and determined microbial C and N and total soil C and N. Elevated CO₂ increased labile C and microbial biomass, but had no effect on net N mineralization, respiration of more recalcitrant C, or total soil C and N. Nitrogen fertilization increased net N mineralization, because of faster decomposition or less immobilization by litter with higher N concentrations. In the four species plots, N fertilization also increased total soil C and N, likely because greater litter production more than offset any increases in decomposition. Increasing the species number from one to four increased C respiration that could largely be attributed to greater soil C inputs from increased biomass accumulation, but reduced net N mineralization, likely because of greater immobilization in the more productive four-species plots. An increase in functional group number did not affect any of the soil parameters measured. While elevated CO₂, N fertilization, and increased species number all increased plant biomass accumulation, they had divergent effects on soil C and N dynamics.
A field experiment was conducted to explore the effects of elevated atmospheric carbon dioxide (CO
2
) (550 ± 17 μmol mol
−1
) on nitrous oxide (N
2
O) emissions and nitrogen (N) dynamics in a ...winter-wheat (
Triticum aestivum
L.) cropping system at the free-air CO
2
enrichment (FACE) experimental facility in northern China. Compared to ambient CO
2
(415 ± 16 μmol mol
−1
) condition, elevated CO
2
increased N
2
O emissions by 21–36 % in the winter-wheat field. Under elevated CO
2
, soil total N at both 0–10 and 10–20 cm depths decreased at the ripening stage (RS) and the NH
4
+
-N content also decreased at the RS and the grain filling stage (GFS), while soil NO
3
−
-N content increased at the booting stage (BS) and RS. Elevated CO
2
increased N concentrations in stem at the GFS, and leaf sheath and glumes at the RS, but decreased N concentration in spike at the GFS. Elevated CO
2
increased N accumulations in leaf and stem at the GFS and in kernel, leaf sheath and glumes at the RS. The analysis shows that more N
2
O would be emitted from this system under the increasing atmospheric CO
2
concentration with the same N fertilizer application rates. Since our results indicate that elevated CO
2
could enhance plant N uptake and N
2
O emissions, more N is likely to be required by winter-wheat cropping systems to maintain current plant and soil N status.
Nitrogen availability in terrestrial ecosystems strongly influences plant productivity and nutrient cycling in response to increasing atmospheric carbon dioxide (CO2). Elevated CO2 has consistently ...stimulated forest productivity at the Duke Forest free‐air CO2 enrichment experiment throughout the decade‐long experiment. It remains unclear how the N cycle has changed with elevated CO2 to support this increased productivity. Using natural‐abundance measures of N isotopes together with an ecosystem‐scale 15N tracer experiment, we quantified the cycling of 15N in plant and soil pools under ambient and elevated CO2 over three growing seasons to determine how elevated CO2 changed N cycling between plants, soil, and microorganisms. After measuring natural‐abundance 15N differences in ambient and CO2‐fumigated plots, we applied inorganic 15N tracers and quantified the redistribution of 15N for three subsequent growing seasons. The natural abundance of leaf litter was enriched under elevated compared to ambient CO2, consistent with deeper rooting and enhanced N mineralization. After tracer application, 15N was initially retained in the organic and mineral soil horizons. Recovery of 15N in plant biomass was 3.5 ± 0.5% in the canopy, 1.7 ± 0.2% in roots and 1.7 ± 0.2% in branches. After two growing seasons, 15N recoveries in biomass and soil pools were not significantly different between CO2 treatments, despite greater total N uptake under elevated CO2. After the third growing season, 15N recovery in trees was significantly higher in elevated compared to ambient CO2. Natural‐abundance 15N and tracer results, taken together, suggest that trees growing under elevated CO2 acquired additional soil N resources to support increased plant growth. Our study provides an integrated understanding of elevated CO2 effects on N cycling in the Duke Forest and provides a basis for inferring how C and N cycling in this forest may respond to elevated CO2 beyond the decadal time scale.
In this paper, a model of emotions is proposed based on various neurological and psychological findings. The proposed model consists of three layers: the external/internal appraisal layer, the ...prediction/decision-making layer, and the emotional memory layer. We implement the proposed model by integrating some deep learning modules such as recurrent attention model, convolutional long short-term memory, and deep deterministic policy gradient. We set a "facial expression" task simulating mother-child interactions and verified emotion differentiation during the task. We also examine the trained model in the "still face" experiment. A claim in this study is that it is a very important step for the constructive approach to compare the proposed model with real human subjects in the same experiment that was carried out in the psychological studies.
Accelerated tree growth under elevated atmospheric CO2 concentrations may influence nutrient cycling in forests by (i) increasing the total leaf area, (ii) increasing the supply of soluble ...carbohydrate in leaf tissue, and (iii) increasing nutrient-use efficiency. Here we report the results of intensive sampling and laboratory analyses of NH4+, NO3-, PO43-, H+, K+, Na+, Ca2+, Mg2+, Cl-, SO42-, and dissolved organic carbon (DOC) in throughfall precipitation during the first 2.5+ years of the Duke University Free-Air CO2 Enrichment (FACE) experiment. After two growing seasons, a large increase (i.e., 48%) in throughfall deposition of DOC and significant trends in throughfall volume and in the deposition of NH4+, NO3-, H+, and K+ can be attributed to the elevated CO2 treatment. The substantial increase in deposition of DOC is most likely associated with increased availability of soluble C in plant foliage, whereas accelerated canopy growth may account for significant trends toward decreasing throughfall volume, decreasing deposition of NH4+, NO3-, and H+, and increasing deposition of K+ under elevated CO2. Despite considerable year-to-year variability, there were seasonal trends in net deposition of NO3-, H+, cations, and DOC associated with plant growth and leaf senescence. The altered chemical fluxes in throughfall suggest that soil solution chemistry may also be substantially altered with continued increases in atmospheric CO2 concentrations in the future.
Carbon dioxide may affect plants by changing the climate, but it can have another more subtle and quite separate influence, through its direct effects on plant physiology. Since CO2 is fundamental to ...photosynthesis, it makes sense that increasing the amount of CO2 in the atmosphere will tend to allow plants to photosynthesize faster. This then is one-half of the direct CO2 effect on plants. But there is also another less straightforward direct effect of CO2 on the water balance of plants. Why should this be?
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