Hydrothermal Regime Variation and Ecological Effects on Fish Reproduction in the Yangtze River

Water temperature, as one of the important water environment impact factors, has a significant impact on the survival and development of aquatic organisms. We selected water temperature data (1959–2017) from four key hydrological stations in the Yangtze River: Cuntan, Yichang, Hankou, and Datong. We analyzed the characteristics and variability of the Yangtze River hydrothermal regime by the Mann-Kendall method, wavelet analysis, and by the IHA-RVA method to analyze hydrothermal regime variations of the Yangtze River, and the response mechanisms of fish to variations in hydrothermal regimes were explored. The results show that (1) The annual average water temperature of the Yangtze River is warming, and Cuntan Station, Yichang Station, Hankou Station, and Datong Station have a sudden increase in temperature in 2002, 1995, 2003, and 2004, and the periodicity analysis demonstrates that Cuntan, Yichang, and Datong stations all have main periods of 24~32 years; (2) The overall variations of 32 hydrothermal indicators at Cuntan Station and Yichang Station reached 65% and 61%, which are close to the height variation; (3) With the construction of the Three Gorges Dam, the stagnant cooling effect caused the arrival date of the upper reproduction water temperature of “The four major fish species” to be delayed by about 23 days, and the stagnant heat effect caused the arrival date of the Chinese sturgeon reproduction upper limit water temperature to be delayed by about 30 days.

Application of a dynamic model for regulating the hydrothermal regime in early potato cultivation in the Volgograd region

The article presents the results of research on the dynamics of development and water consumption of early potatoes, obtained from field observations in a multi-factor experiment, which formed the basis of the initial database of water adaptive regulation, temperature and food regimes based on simulation. The dynamic simulation model “POTATO” developed on this basis is aimed at displaying the processes of phenological development of potatoes and predicting crop yields during irrigation and fertigation. The model provides a forecast of the timing of the early potato development phenological phases, its yield depending on specific soil and weather conditions, as well as irrigation modes (sprinkling, drip and combined ones) and the level of mineral nutrition. The forecast of the dynamics of the culture phenological development allows to adjust the schedule of reclamation measures to regulate water and temperature regimes, taking into account current and forecast meteorological information. The simulation model allows to perform operational management of the hydrothermal and food regime of the agrocoenosis in order to obtain the planned yields. The developed method of regulating the hydrothermal regime based on the “POTATO” simulation model makes it possible to implement operational irrigation management and choose the optimal and cost-effective irrigation strategy.

Impact of weather conditions and sowing method on seed performance of meadow clover in the Middle Urals

Seed production of perennial leguminous herbs, including meadow clover (Trifolium praténse), is complicated due to the natural and climatic conditions of the region. In Middle Urals, only two to three years out of ten are favorable for seed production. Estimation of influence of the hydrothermal regime of the growing season and the sowing method has been carried out in the experimental crop rotation of the Udmurt Research Institute of Agriculture, UdmFRC Ural Branch of the RAS with the seed grass stand of meadow diploid clover varieties Pelican and Trio, tetraploid variety Kudesnik It has been revealed that seed productivity of meadow clover on sod-podzolic medium loamy soil was more dependent on the prevailing hydrothermal regimes of vegetation periods, as well as on the variety’s ploidy. A relatively high seeds yield of the Pelican variety (2n) 444-593 kg/ha and Kudesnik variety (4n) 101-116 kg/ha was formed under conditions of insufficient and optimal moisture supply of the vegetation period with a hydrothermal coefficient of 0.67-1.41. With increase in hydrothermal coefficient p to 1.56-1.69, the seeds yield of the Trio variety (2n) decreased to 251-328 kg/ha, of the Kudesnik variety (4n) - to 77-91 kg/ha. Under the same conditions, according to the hydrothermal regime of vegetation, the Kudesnik clover variety formed a relatively larger number of stems and heads, however, the heads productivity was significantly inferior to diploid varieties, which ultimately affected its seed productivity. Sowing diploid varieties of meadow clover Pelican and Trio in the usual ordinary way (15 cm), tetraploid variety Kudesnik in a wide-row way (30 cm) allowed increasing seeds yield and thereby neutralizing the negative impact of weather factors. Sstudy of the seed formation features of meadow clover varieties differing in ploidy in contrasting agrometeorological conditions may be of interest in developing methods for optimizing their seed productivity.

Assessing the simulated soil hydrothermal regime of the active layer from the Noah-MP land surface model (v1.1) in the permafrost regions of the Qinghai–Tibet Plateau

Extensive and rigorous model intercomparison is of great importance before model application due to the uncertainties in current land surface models (LSMs). Without considering the uncertainties in forcing data and model parameters, this study designed an ensemble of 55 296 experiments to evaluate the Noah LSM with multi-parameterization (Noah-MP) for snow cover events (SCEs), soil temperature (ST) and soil liquid water (SLW) simulation, and investigated the sensitivity of parameterization schemes at a typical permafrost site on the Qinghai–Tibet Plateau (QTP). The results showed that Noah-MP systematically overestimates snow cover, which could be greatly resolved when adopting the sublimation from wind and a semi-implicit snow/soil temperature time scheme. As a result of the overestimated snow, Noah-MP generally underestimates ST, which is mostly influenced by the snow process. A systematic cold bias and large uncertainties in soil temperature remain after eliminating the effects of snow, particularly in the deep layers and during the cold season. The combination of roughness length for heat and under-canopy (below-canopy) aerodynamic resistance contributes to resolving the cold bias in soil temperature. In addition, Noah-MP generally underestimates top SLW. The runoff and groundwater (RUN) process dominates the SLW simulation in comparison to the very limited impacts of all other physical processes. The analysis of the model structural uncertainties and characteristics of each scheme would be constructive to a better understanding of the land surface processes in the permafrost regions of the QTP as well as to further model improvements towards soil hydrothermal regime modeling using LSMs.

Hydrothermic regime management of the irrigated field while growing early potatoes in the arid zone

<p>The problem of obtaining consistently high yields of early potatoes while minimizing the cost per unit of production is very serious. Improving the technology of growing potatoes in the dry steppe zone with the integrated irrigation and fermentation systems is aimed not only at meeting the needs of the population in these products in the region, but also at reducing the demand for the purchase of potatoes abroad.</p><p>The dynamics of the main factors of plant life associated with the state of the environment, and the needs of plants at different stages of development may differ significantly from each other, which leads to a decrease in the intensity of the production process and yield. Regulation of the hydrothermal regime of crop during the critical periods of plant vegetation can be a useful agrotechnical method in managing the water regime and productivity of potatoes in the conditions of the dry steppe zone.</p><p>The use of digital technology for regulating the water-thermal regime of irrigated crops with using simulation models is caused not only by the specifics of the problem being solved, but also by the requirements for updating irrigation and drainage systems based on the modern technical advances and fundamental knowledge in order to implement highly efficient and environmentally friendly farming on reclaimed land.</p><p>Results of multifactor experiments on potatoes cultivation under drip irrigation and finely divided sprinkling in the conditions of the Volgograd region did not allow us to identify optimal technological parameters with apply of statistical methods. In addition to the small number of field experiments over a number of years, the high variation of weather conditions was the dominant factor, that is leading the shifts in vegetative growth period duration and the most significant stages of potato growing.</p><p>The prospect to solve this problem is recognized in application of a dynamic model for the potato crop growing that considers the ability to control soil moisture in the root zone and temperature regime of the vegetation cover and simulate them depending on the emerging weather conditions and the actual state of the plants. Using the J. Richie algorithm to determine evaporation and transpiration, it is easy to reconcile the design scheme with soil moisture distribution under drip irrigation, and also consider the agrocenosis water balance with periodic fine dispersion water sprinkling when the set air temperature is exceeded in the hottest hours of the day. Preliminary numerical experiments, based on the retrospective data of earlier field experiments, indicate sufficient flexibility of the model in terms of the formed water-temperature regime simulation and its influence on potato growth processes.</p><p>In 2019, the technology of growing early potatoes was tested using a dynamic model in the Ryazan region for the temperate climate of the forest-steppe area. The model showed adequate results of its application to control the hydrothermal regime in irrigation by sprinkling.</p><p>The research is carried out under the Grant of the RFBR 19-416-343004 р_мол_а with the support of the Committee for Economic Policy and Development of the Volgograd Region.</p>