Browsing by Subject "nitrogen uptake"

Sort by: Order: Results:

Now showing items 1-4 of 4
  • Walde, Manuel; Allan, Eric; Cappelli, Seraina L.; Didion-Gency, Margaux; Gessler, Arthur; Lehmann, Marco M.; Pichon, Noemie A.; Grossiord, Charlotte (2021)
    Many experiments have shown that biodiversity promotes ecosystem functioning and stability and that this relationship varies with resource availability. However, we still have a poor understanding of the underlying physiological and ecological mechanisms driving diversity effects and how they may interact with soil nutrient availability. We collected data in a grassland experiment factorially manipulating fertilization, species richness (SR), functional composition (slow-growing vs. fast-growing species) and functional diversity in resource economic traits. We measured above-ground productivity (AP), nitrogen (N) uptake, photosynthesis and water use efficiency by combining a N-15 labelling approach with productivity, gas exchange and stable isotope measurements in 3 years differing in rainfall. We found that sown SR increased AP, N uptake and photosynthesis, suggesting that SR is the most important driver of ecosystem productivity and nutrient cycling. Similarly, photosynthesis was affected by functional composition but not by functional diversity. Water use efficiency was reduced by sown SR for communities dominated by slow-growing species but not for communities dominated by fast-growing species. Fertilization increased productivity, N uptake and water use efficiency. The positive effects of high SR on ecosystem functions were independent of fertility levels. Synthesis. Our results provide evidence that high species richness in temperate grasslands could enhance productivity and reduce the negative impacts of drought events. Multiple factors and community characteristics are important in driving enhanced ecosystem functioning in biodiverse grasslands and seem to affect functioning and stability through different mechanisms.
  • Adamczyk, Bartosz; Sietio, Outi-Maaria; Biasi, Christina; Heinonsalo, Jussi (2019)
    See also the Commentary on this article by Hattenschwiler et al., 223: 5-7.
  • Jenal, Alexander; Hueging, Hubert; Ahrends, Hella Ellen; Bolten, Andreas; Bongartz, Jens; Bareth, Georg (2021)
    UAV-based multispectral multi-camera systems are widely used in scientific research for non-destructive crop traits estimation to optimize agricultural management decisions. These systems typically provide data from the visible and near-infrared (VNIR) domain. However, several key absorption features related to biomass and nitrogen (N) are located in the short-wave infrared (SWIR) domain. Therefore, this study investigates a novel multi-camera system prototype that addresses this spectral gap with a sensitivity from 600 to 1700 nm by implementing dedicated bandpass filter combinations to derive application-specific vegetation indices (VIs). In this study, two VIs, GnyLi and NRI, were applied using data obtained on a single observation date at a winter wheat field experiment located in Germany. Ground truth data were destructively sampled for the entire growing season. Likewise, crop heights were derived from UAV-based RGB image data using an improved approach developed within this study. Based on these variables, regression models were derived to estimate fresh and dry biomass, crop moisture, N concentration, and N uptake. The relationships between the NIR/SWIR-based VIs and the estimated crop traits were successfully evaluated (R-2: 0.57 to 0.66). Both VIs were further validated against the sampled ground truth data (R-2: 0.75 to 0.84). These results indicate the imaging system's potential for monitoring crop traits in agricultural applications, but further multitemporal validations are needed.
  • Guo, Qingxue; Wu, Xiaoyi; Korpelainen, Helena; Li, Chunyang (2020)
    Plant-plant competition is a dynamic and complicated process that is strongly influenced by abiotic conditions. Drought is a critical threat to forests, particularly to young plantation forests. Temporal changes in competition combined with the effects of drought may dramatically influence the physiological traits of plants. Cunninghamia lanceolata plants exposed to intra-specific competition and no-competition conditions were investigated under two soil water levels (well-watered and drought). Changes in plant-plant competition relationships and nitrogen uptake rates were measured at different harvest times. The effects of drought and plant competition on physiological traits, for example, leaf nitrogen allocation, δ13C, and levels of abscisic acid (ABA), indole acetic acid (IAA) and jasmonic acid (JA), were also explored. Our results indicated that C. lanceolata shifted from intense neighbor competition to facilitation under well-watered conditions, whereas under drought neighbor competition became much stronger at the second harvest compared to the first harvest. Strong competition significantly decreased N uptake under drought. Leaf NH4+, NO3- and N allocation to water-soluble proteins increased under drought at the first harvest, but significantly declined under prolonged drought. Leaf, stem and root starch concentrations were enhanced by drought. However, during prolonged drought, the root starch concentrations, leaf δ13C, leaf ABA and starch content of C. lanceolata were much lower under strong neighbor competition than in no-competition conditions, which demonstrated that the combined effects of drought and strong competition were more harmful to plant growth and survival compared to single effects. Our study demonstrated that drought combined with competition strongly affected the N uptake, N allocation and physiological traits of plants. Intense competition imposed by neighbors is a great threat to the growth and survival of young C. lanceolata plantations under prolonged drought.