Leaf Physiological Responses of Three Psammophytes to Combined Effects of Warming and Precipitation Reduction in Horqin Sandy Land, Northeast China

The decreasing precipitation with global climate warming is the main climatic condition in some sandy grassland ecosystems. The understanding of physiological responses of psammophytes in relation to warming and precipitation is a possible way to estimate the response of plant community stability to climate change. We selected Lespedeza davurica, Artemisia scoparia, and Cleistogenes squarrosa in sandy grassland to examine the effect of a combination of climate warming and decreasing precipitation on relative water content (RWC), chlorophyll, proline, and antioxidant enzyme activities. We found that all experimental treatments have influenced RWC, chlorophyll, proline, and antioxidant enzyme activities of three psammophytes. L. davurica has the highest leaf RWC among the three psammophytes. With the intensification of precipitation reduction, the decreasing amplitude of chlorophyll from three psammophytes was L. davurica > C. squarrosa > A. scoparia. At the natural temperature, the malondialdehyde (MDA) content of the three psammophytes under severe drought treatment was much higher than other treatments, and their increasing degree was as follows: A. scoparia > C. squarrosa > L. davurica. At the same precipitation gradient, the proline of three psammophytes under warming was higher than the natural temperature. The differences in superoxide dismutase (SOD) among the three psammophytes were A. scoparia > L. davurica > C. squarrosa. Moreover, at natural temperature, more than 40% of precipitation reduction was most significant. Regardless of warming or not, the catalase (CAT) activity of A. scoparia under reduced precipitation treatments was higher than natural temperature, while the response of L. davurica was opposite. Correlation analyses evidenced that warming (T) was significant in L. davurica and precipitation (W) was significant in A. scoparia and C. squarrosa according to the Monte-Carlo permutation test (p = 0.002, 0.004, and 0.004). The study is important in predicting how local plants will respond to future climate change and assessing the possible effects of climate change on sandy grassland ecosystems.

Chemical synthesis of nanopowder Nd2Fe14BаSiO2 of the nucleus-shell type

Nanoparticles of the alloy with the composition Nd-Fe-B were formed by the chemical method of co-precipitation reduction using a reducing agent sodium borohydride. The nanoparticle size was 35–95 nm. The silica coating was applied after stabilizing the nanoparticles with APTMS. The core of Nd-Fe-B alloy nanoparticles covered with a SiO2 shell, Nd2Fe14BаSiO2, the particle size was 35–125 nm with a shell width of 8–15 nm.

Could Artificial Downwelling/Upwelling Mitigate Oceanic Deoxygenation in Western Subarctic North Pacific?

Subpolar gyre regions such as the Western Subarctic North Pacific (WSNP) contain sluggish, low-oxygen water, and are threatened by loss of oxygen (deoxygenation). Our simulations under RCP 8.5 emission scenario suggest that installing pipes to induce artificial downwelling and upwelling (AD and AU) provides short-term solutions to combat deoxygenation in the WSNP. With no engineering, the WSNP's subsurface oxygen decreases by 30–100 mmol/m3 by the year 2100. Continuous implementation of AD and AU instead counters this declining trend, and AD is more effective than AU. The oxygenation effect is primarily a consequence of how the two engineering schemes vertically redistribute oxygen via physical processes. AD directly improves oxygen at depth via advecting surface water toward the ocean interior and subsequent enhanced pycnocline mixing, and AU does so via generating compensatory downwelling outside of the pipes. Both schemes take near 40 years to complete the oxygenation. After that, oxygen reaches a new equilibrium state in the WSNP with no further improvement by the engineering. AD and AU both strongly increase primary production surrounding the deployment sites, but lead only to weak enhancement of aerobic respiration in subsurface water and thus a minor impact on the oxygenation. Other unwanted environmental side effects are negligible compared to those caused by rapid climate change within this century, including outgassing of carbon dioxide, pH decrease, and precipitation reduction.

Impact of combined nitrogen loading and long-term drought on a semi-natural temperate grassland - achieving a process based understanding across scales

<p>Two important threats to the sustainable functioning of seminatural grasslands in temperate zones are (1) nutrient loading due to agricultural fertilization and pollution, and (2) the increase of extreme drought events due to climate change. These threats may cause substantial shifts in species diversity and abundance and considerably affect the carbon and water balance of ecosystems. The synergistic effects between those two threats, however, can be complex and are poorly understood. Here, we experimentally investigated the effects of nitrogen addition and extreme drought (separately and in combination) on a seminatural temperate grassland, located in Freiburg (South Germany). To study the grassland response, we combined eddy-covariance techniques with open gas exchange systems. Open gas exchange chambers were connected to an infrared gas analyzer and water isotope spectrometer, which allowed the partitioning of net ecosystem exchange and evapotranspiration. In addition, leaf level physiological responses, e.g. leaf gas-exchange and water potentials, as well as vegetation parameters, e.g. species richness, species abundance, leaf area index, were assessed.</p><p>Our results suggest that grassland communities, strongly weakened in their stress response by nitrogen loading, can substantially lose their carbon sink function during drought. Over the growing season (April-September), the carbon sequestration of the studied grassland was reduced by more than 60% as a consequence of nitrogen addition. Nitrogen addition in combination with precipitation reduction decreased carbon sequestration by 73%. We observed more efficient N utilization in grasses compared to forbs. However, these clearly specific responses of the different functional groups to N loading, both functional groups were able to maintain homeostasis of leaf carbon and water fluxes. Thus, strong declines in the (community) carbon sequestration and water use efficiency were not related to leaf physiological responses in assimilation and transpiration. Instead, nitrogen addition caused a significant loss in forb species (−25%) and precipitation reduction promoted a strong dominance of grass species at season start. Consequently, the resulting grass-dominated and species-poor community suffered from a strong above-ground dieback during the dry summer months, likely caused by lower water use efficiency and weaker drought adaptations of the species community. </p><p>Eutrophication can severely threaten the resilient functioning of grasslands, in particular when drought periods will increase as predicted by future climate scenarios. Our findings emphasize the importance of preserving high diversity of grasslands to strengthen their resistance against extreme events such as droughts.</p>

Precipitation Changes Regulate Plant and Soil Microbial Biomass Via Plasticity in Plant Biomass Allocation in Grasslands: A Meta-Analysis

In theory, changes in the amount of rainfall can change plant biomass allocation and subsequently influence coupled plant-soil microbial processes. However, testing patterns of combined responses of plants and soils remains a knowledge gap for terrestrial ecosystems. We carried out a comprehensive review of the available literature and conducted a meta-analysis to explore combined plant and soil microbial responses in grasslands exposed to experimental precipitation changes. We measured the effects of experimental precipitation changes on plant biomass, biomass allocation, and soil microbial biomass and tested for trade-offs between plant and soil responses to altered precipitation. We found that aboveground and belowground plant biomass responded asynchronically to precipitation changes, thereby leading to shifts in plant biomass allocation. Belowground plant biomass did not change under precipitation changes, but aboveground plant biomass decreased in precipitation reduction and increased in precipitation addition. There was a trade-off between responses of aboveground plant biomass and belowground plant biomass to precipitation reduction, but correlation wasn't found for precipitation addition. Microbial biomass carbon (C) did not change under the treatments of precipitation reduction. Increased root allocation may buffer drought stress for soil microbes through root exudations and neutralize microbial responses to precipitation reduction. However, precipitation addition increased microbial biomass C, potentially reflecting the removal of water limitation for soil microbial growth. We found that there were positive correlations between responses of aboveground plant biomass and microbial biomass C to precipitation addition, indicating that increased shoot growth probably promoted microbial responses via litter inputs. In sum, our study suggested that aboveground, belowground plant biomass and soil microbial biomass can respond asynchronically to precipitation changes, and emphasizes that testing the plant-soil system as a whole is necessary for forecasting the effects of precipitation changes on grassland systems.

Au/CeO2/g-C3N4 Nanocomposite Modified Electrode as Electrochemical Sensor for the Determination of Phenol

A convenient and simple phenol electrochemical sensor was constructed based on the Au/CeO2/ g-C3N4 nanocomposites, which were obtained by loading the gold–cerium oxide (Au/CeO2) nanoparticle on graphite-like carbon nitride (g-C3N4) through precipitation–reduction methods. The microstructure and morphology of Au/CeO2/g-C3N4 nanocomposite were verified using different techniques such as XRD, TEM, and HRTEM. Voltammetry and amperometry methods were used to study the electrochemical performance of the constructed phenol electrochemical sensors. The results demonstrated evidently that the combination of Au/CeO2 and g-C3N4 may improve sensing performances of phenol determination. The detection linear range of the sensor was 10–90 μM under the optimum parameters. The Au/CeO2/g-C3N4 based electrochemical sensor also has low detection limits (2.33 μM) and high sensitivities (0.1080 mA/μM) for phenol detection. In addition, the sensor also had considerably favorable anti-interference performance. As a consequence, the sensor demonstrated that the electrochemical system provided a promising effective strategy for detection of phenol.