An Application of a LPWAN for Upgrading Proximal Soil Sensing Systems.

In recent years, the Internet of Things (IoT), based on low-power wide-area network (LPWAN) wireless communication technology, has developed rapidly. On the one hand, the IoT makes it possible to conduct low-cost, low-power, wide-coverage, and real-time soil monitoring in fields. On the other hand, many proximal soil sensor devices designed based on conventional communication methods that are stored in an inventory face elimination. Considering the idea of saving resources and costs, this paper applied LPWAN technology to an inventoried proximal soil sensor device, by designing an attachment hardware system (AHS) and realizing technical upgrades. The results of the experimental tests proved that the sensor device, after upgrading, could work for several years with only a battery power supply, and the effective wireless communication coverage was nearly 1 km in a typical suburban farming environment. Therefore, the new device not only retained the original mature sensing technology of the sensor device, but also exhibited ultralow power consumption and long-distance transmission, which are advantages of the LPWAN; gave full play to the application value and economic value of the devices stored in inventory; and saved resources and costs. The proposed approach also provides a reference for applying LPWAN technology to a wider range of inventoried sensor devices for technical upgrading.

Comparison of crop yield sensitivity to ozone between open-top chamber and free-air experiments.

Assessments of the impacts of ozone (O3 ) on regional and global food production are currently based on results from experiments using open-top chambers (OTCs). However, there are concerns that these impact estimates might be biased due to the environmental artifacts imposed by this enclosure system. In this study, we collated O3 exposure and yield data for three major crop species-wheat, rice, and soybean-for which O3 experiments have been conducted with OTCs as well as the ecologically more realistic free-air O3 elevation (O3 -FACE) exposure system; both within the same cultivation region and country. For all three crops, we found that the sensitivity of crop yield to the O3 metric AOT40 (accumulated hourly O3 exposure above a cut-off threshold concentration of 40 ppb) significantly differed between OTC and O3 -FACE experiments. In wheat and rice, O3 sensitivity was higher in O3 -FACE than OTC experiments, while the opposite was the case for soybean. In all three crops, these differences could be linked to factors influencing stomatal conductance (manipulation of water inputs, passive chamber warming, and cultivar differences in gas exchange). Our study thus highlights the importance of accounting for factors that control stomatal O3 flux when applying experimental data to assess O3 impacts on crops at large spatial scales.

Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem.

[Effects of O3-FACE(ozone-free air control enrichment) on gas exchange and chlorophyll fluorescence of rice leaf].

O3-FACE (Ozone-free air control enrichment) platform has been established for observing the effect of elevated tropospheric ozone concentration on the gas exchange and chlorophyll fluorescence of two rice varieties (Wuyunjing 21 and Liangyoupeijiu). The results showed that high ozone concentration decreased the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of rice leaves. After 76d fumigation the decline in them for Wuyunjing 21 was as follows: 21.7%, 26.64% and 24.74% respectively, and that for Liangyoupeijiu was as follows: 25.53%, 30.31% and 25.48% respectively; however, no significant impact on leaf intercellular CO2 concentration was observed. Chlorophyll fluorescence kinetics parameters changed as can be seen by the decrease in F0 (initial fluorescence in the dark), ETR (The apparent electron transfer rate) and psiPSII (actual photochemical efficiency of PS II in the light), and the increase in NPQ (non-photochemical quenching). After 76 days of O3 treatment, the NPQ of Wuyunjing 21 and Liangyoupeijiu was enhanced by 16.37% and 11.77%, respectively. The impact of ozone on rice was a cumulative effect, and the extent of variation in the above parameters and the differences between the two varieties were enlarged as the O3 treatment time increased; At the same time because the rice leaf intercellular CO2 concentration did not significantly reduce, the inferred decrease in net photosynthetic rate was restricted by non-stomatal factors. The results of this experiment indicated that Liangyoupeijiu was more susceptible to ozone than Wuyunjing 21.

Effects of elevated ground-level ozone on paddy soil bacterial community and assembly mechanisms across four years.

It is well known that elevated ground-level ozone (eO3) poses a threat to the ecosystem. Little knowledge about the underground variables, especially on soil microorganisms, however, has been revealed. Such knowledge will tremendously help to advance our understanding of the correlation between ecosystems and climate change, as well as our ability to predict future trajectory. For this purpose, we have collected soil DNA samples (eO3 vs. Ambient, each having 36 samples) over four years. Our results have verified the temporal responses and the underlying assembly mechanisms of the paddy bacterial community to eO3. Contrary to the widespread consensus, it was found that eO3 stimulated bacterial alpha diversities. The higher complexity and the centralization of the co-occurrence network of the bacterial community suggested that this stimulation was due to a microbial survival strategy in response to the limited resources, which led to the instability of the community. Furthermore, the observed slower temporal turnover of the bacterial community composition in response to eO3 was due to the decreased deterministic processes derived from plants, which implied that eO3 disrupted the coordination between soil microorganisms and rice crop. All above phenomena provided novel insights into the adverse influences of eO3 on the soil microbial community. If O3 concentration increases continuously, the adverse effects will be aggravated and harm the related ecological functions.

Tropospheric ozone assessment report: Global ozone metrics for climate change, human health, and crop/ecosystem research.

Assessment of spatial and temporal variation in the impacts of ozone on human health, vegetation, and climate requires appropriate metrics. A key component of the Tropospheric Ozone Assessment Report (TOAR) is the consistent calculation of these metrics at thousands of monitoring sites globally. Investigating temporal trends in these metrics required that the same statistical methods be applied across these ozone monitoring sites. The nonparametric Mann-Kendall test (for significant trends) and the Theil-Sen estimator (for estimating the magnitude of trend) were selected to provide robust methods across all sites. This paper provides the scientific underpinnings necessary to better understand the implications of and rationale for selecting a specific TOAR metric for assessing spatial and temporal variation in ozone for a particular impact. The rationale and underlying research evidence that influence the derivation of specific metrics are given. The form of 25 metrics (4 for model-measurement comparison, 5 for characterization of ozone in the free troposphere, 11 for human health impacts, and 5 for vegetation impacts) are described. Finally, this study categorizes health and vegetation exposure metrics based on the extent to which they are determined only by the highest hourly ozone levels, or by a wider range of values. The magnitude of the metrics is influenced by both the distribution of hourly average ozone concentrations at a site location, and the extent to which a particular metric is determined by relatively low, moderate, and high hourly ozone levels. Hence, for the same ozone time series, changes in the distribution of ozone concentrations can result in different changes in the magnitude and direction of trends for different metrics. Thus, dissimilar conclusions about the effect of changes in the drivers of ozone variability (e.g., precursor emissions) on health and vegetation exposure can result from the selection of different metrics.

Different responses of transgenic Bt rice and conventional rice to elevated ozone concentration.

To assess the different sensitivity to ozone (O3) between transgenic Bt Shanyou63 (Bt-SY63) and its nontransgenic counterpart Shanyou63 (SY63), the leaf gas exchange, yield, grain elements, and antioxidant enzymes were investigated by performing a pot experiment under ambient O3 concentration (A-O3) and elevated O3 concentration (1.5 × A-O3, E-O3). Under A-O3, the chlorophyll content and yield of Bt-SY63 were significantly lower than those of SY63, whereas the stomatal conductance (Gs), cellular CO2 concentration (Ci), and Fe, Zn concentration showed the opposite trends. No significant difference was detected for malondialdehyde (MDA) content between two cultivars, although the antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities in Bt-SY63 tended to be higher than those in SY63. Exposure to E-O3 resulted in significant reduction for photosynthesis (Pn), yield and all grain elements (except for N) concentration in both varieties, and the extents in Bt-SY63 were much greater than those in SY63. Meanwhile, significant increases for MDA content by 30.6 and 23.7% in Bt-SY63 and SY63, respectively, were detected under E-O3. These results demonstrated that insertion of exogenous gene could induce several unintentional changes of Bt-SY63 in physiology and growth progress, compared with SY63 under ambient O3 concentration. On the other hand, the injury of Bt-SY63 caused by elevated O3 concentration was more severe than that of SY63. This study provided valuable baseline information for the commercial release and breeding strategies of Bt-SY63 under the projected future climate.

Divergent responses of methanogenic archaeal communities in two rice cultivars to elevated ground-level O3.

Inhibitive effect of elevated ground-level ozone (O3) on paddy methane (CH4) emission varies with rice cultivars. However, little information is available on its microbial mechanism. For this purpose, the responses of methane-metabolizing microorganisms, methanogenic archaea and methanotrophic bacteria to O3 pollution were investigated in the O3-tolerant (YD6) and the O3-sensitive (IIY084) cultivars at two rice growth stages in Free Air Concentration Elevation of O3 (O3-FACE) system of China. It was found that O3 pollution didn't change the abundances of Type I and Type II methanotrophic bacteria at two rice stages. For methanogenic archaea, their abundances in both cultivars were decreased by O3 pollution at the tillering stage. Furthermore, a greater negative influence on methanogenic archaeal community was observed on IIY084 than on YD6: at tillering stage, the alpha diversity indices of methanogenic archaeal community in IIY084 was decreased to a greater extent than in YD6; IIY084 shifted methanogenic archaeal community composition and decreased the abundances and the diversities of Methanosarcinaceae and Methanosaetaceae as well as the abundance of Methanomicrobiales, while the diversity of Methanocellaceae were increased in YD6. These findings indicate that the variations in the responses of paddy CH4 emission to O3 pollution between cultivars could result from the divergent responses of their methanogenic archaea.

The contrasting responses of soil microorganisms in two rice cultivars to elevated ground-level ozone.

Although elevated ground-level O3 has a species-specific impact on plant growth, the differences in soil biota responses to O3 pollution among rice cultivars are rarely reported. Using O3 Free-Air Concentration Enrichment, the responses of the rhizospheric bacterial communities in the O3-tolerant (YD6) and the O3-sensitive (IIY084) rice cultivars to O3 pollution and their differences were assessed by pyrosequencing at rice tillering and anthesis stages. Elevated ground-level O3 negatively influenced the bacterial community in cultivar YD6 at both rice growth stages by decreasing the bacterial phylogenetic diversities and response ratios. In contrast, in cultivar IIY084, the bacterial community responded positively at the rice tillering stage under O3 pollution. However, several keystone bacterial guilds were consistently negatively affected by O3 pollution in two rice cultivars. These findings indicate that continuously O3 pollution would negatively influence rice agroecosystem and the crop cultivar is important in determining the soil biota responses to elevated O3.

Apoplastic antioxidant enzyme responses to chronic free-air ozone exposure in two different ozone-sensitive wheat cultivars.

The effects of elevated ozone concentrations [O3] on two different ozone-sensitive wheat (Triticum aestivum L.) cultivars [Yangmai16 (Y16) and Yannong19 (Y19)] were investigated to determine the different apoplastic antioxidant mechanisms under O3-FACE (free-air controlled enrichment) condition. The results indicated that elevated [O3] (1.5 × ambient [O3]) induced increases in the production of superoxide anion (O2(-)), hydroxyl radical (HO), hydrogen peroxide (H2O2) and lipid peroxidation, and these results were more pronounced in the apoplasts of Y19 than in those of Y16. Apoplastic antioxidant enzymes were developmentally regulated and the effect of elevated [O3] depended on the developmental stage of wheat for both cultivars. In cultivar Y19, continuous O3 stress induced a decrease in the activity of apoplastic superoxide dismutase (SOD; EC 1.15.1.1), peroxidase (POD; EC 1.11.1.7) and ascorbate peroxidase (APX; EC 1.11.1.11) in the later growing stages, indicating Y19 appears to be the more sensitive cultivar and is prone to oxidative stress. The strategic response of antioxidant enzymes activities by Y16 in four different plant development stages (booting, flowering, filling and ripening) resulted in O3 stress-induced antioxidant defense responses, which indicated its higher tolerance to O3 stress. The same patterns of activity of apoplastic SOD and APX isozymes were observed in both Y16 and Y19 cultivars, while POD isozymes differed by cultivar in terms of the pattern of bands. The results of the present study show that O3 tolerance can be improved by regulating apoplastic ROS metabolism through the responses of apoplastic antioxidant enzymes to O3 stress in different plant development stages.

A projection of ozone-induced wheat production loss in China and India for the years 2000 and 2020 with exposure-based and flux-based approaches.

Using a high-resolution (40 × 40 km) chemical transport model coupled with the Regional Emission inventory in Asia (REAS), we simulated surface ozone concentrations ([O3 ]) and evaluated O3 -induced wheat production loss in China and India for the years 2000 and 2020 using dose-response functions based on AOT40 (accumulated [O3 ] above 40 ppb) and PODY (phytotoxic O3 dose, accumulated stomatal flux of O3 above a threshold of Y nmol m(-2) s(-1) ). Two O3 dose metrics (90 days AOT40 and POD6 ) were derived from European experiments, and the other two (75 days AOT40 and POD12 ) were adapted from Asian studies. Relative yield loss (RYL) of wheat in 2000 was estimated to be 6.4-14.9% for China and 8.2-22.3% for India. POD6 predicted greater RYL, especially for the warm regions of India, whereas the 90 days AOT40 gave the lowest estimates. For the future projection, all the O3 dose metrics gave comparable estimates of an increase in RYL from 2000 to 2020 in the range 8.1-9.4% and 5.4-7.7% for China and India, respectively. The lower projected increase in RYL for India may be due to conservative estimation of the emission increase in 2020. Sensitivity tests of the model showed that the PODY -based estimates of RYL are highly sensitive to perturbations in the meteorological inputs, but that the estimated increase in RYL from 2000 to 2020 is much more robust. The projected increase in wheat production loss in China and India in the near future is substantially larger than the uncertainties in the estimation and indicates an urgent need for curbing the rapid increase in surface [O3 ] in these regions.

A stomatal ozone flux-response relationship to assess ozone-induced yield loss of winter wheat in subtropical China.

Stomatal ozone flux and flux-response relationships were derived for winter wheat (Triticum aestivum L.) grown under fully open-air ozone fumigation. A stomatal conductance (g(sto)) model developed for wheat in Europe was re-parameterized. Compared to European model parameterizations, the main changes were that the VPD and radiation response functions were made less and more restrictive, respectively, and that the temperature function was omitted. The re-parameterized g(sto) model performed well with an r(2) value of 0.76. The slope and intercept of the regression between observed and predicted g(sto) were not significantly different from 1 to 0, respectively. An ozone uptake threshold of 12 nmol m(-2) s(-1) was judged most reasonable for the wheat flux-response relationship in subtropical China. Judging from both flux- and concentration-based relationships, the cultivars investigated seem to be more sensitive to ozone than European cultivars. The new flux-response relationship can be applied to ozone risk assessment in subtropical regions.

[Photosynthetic damage induced by elevated O3 in two varieties of winter wheat with free air controlled enrichment approach].

O3-FACE (ozone-free air controlled enrichment) platform has been established for observing the photosynthetic damage induced by elevated O3 in functional leaves of two winter wheat (Tritcium aestivum L.) varieties (Yangmai 16 and Yannong 19) during grain filling stage. The results showed that the response trend of all the parameters was similar: (1) The net photosynthetic rate (Pn) decreased gradually and after 35 days of O3 treatment, Pn decreased by 56.21% and 21.82% for Yannong 19 and Yangmai 16, respectively. (2) Chlorophyll fluorescence kinetics parameters changed as decreased in Fv/Fm (maximal photochemical efficiency of PS II in the dark), qp (photochemical quenching), Phiexe (excitation capture efficiency of PS II or intrinsic PS II efficiency), PhiPSII (actual photochemical efficiency of PS II in the light), and increased in NPQ (non-photochemical quenching); Energy distribution parameters changed as rose in % D (fraction of light absorbed in PS II that is dissipated in the PS II antenna), reduced in % P (fraction of light absorbed that is used in photochemistry), and no significant changed in % X (fraction of light absorbed that is not used or dissipated in the PS II antenna). After 35 days of O3 treatment, the actual photochemical efficiency of PS II of Yannong 19 and Yangmai 16 were reduced by 24.42% and 9.97%, respectively.(3) It was declined in Chlt/Car (total chlorophyll content/carotinoid content) while the ratio of Chla/Chlb (chlorophyll a content/chlorophyll b content) was increased. There was a growth in Mg2+, Ca2+-ATPase, activities and ATP contents in chloroplast. The extent of variation in the above parameters and the differences between the two varieties were enlarged as the O3 treatment time increasing and it could be found a more serious damage effect in Yannong 19 than that of in Yangmai 16. In conclusion, the responses of the capacities of defense and repair systems of the two varieties to elevated O3 were reflected by increase in heat dissipation, changes in contents and composition of photosynthetic pigments, and enhancement in the ATP (ATP enzyme) activities in chloroplast. With the time of O3 treatment elongating, there was an accumulation effect of 03 damage to wheat and a great different tolerance between the two varieties was observed.