Biochemical Characteristics of Saint Mary’s Thistle Varieties (<i>Silybum marianum</i>L. <i>Gaertn.</i>) under Soil-Climate Conditions of the Khorezm Region

This article deals with the biochemical characteristics of varieties of Saint Mary’s Thistle such as Panacea, Debut and Samaryanka. Based on the studies, it was found that the highest oil content was found in the species Debut (26%). The lowest oil content was observed in the variety Samaryanka (19%). The highest protein content and the sum of total amino acids in the seeds of St. Mary’s Thistle varieties were found in the variety Debut (131.1), and the lowest indication was observed in the species Samaryanka (79.2). By the number of replaceable amino acids existing in the seeds of the species of St. Mary’s Thistle, it was found in the Varieties Debut (126.3), and the lowest indication was observed in the variety Samaryanka (112). Based on the results of studies and the noted biochemical characteristics and varietal differences of the St. Mary’s Thistle, the possibility and expediency of expanding the crops of this species in the soil and climatic conditions of the Khorezm region are suggested. The research was conducted 2017-2019 y.

Variation of Soil CO_2 Flux and Carbon Density in Three Apline Meadows

Three alpine meadows were chosen from the eastern margin of the Qilian Mountain：Polygonum viviparum meadow（P）,Stipa capillata grassland（S）and Rhododendron simsii shrub meadow（R）;LI-8100 A soil CO2 flux auto-monitoring system and lab analysis were applied to analyze the soil organic carbon density,dynamics of carbon flux,and their relationship with environmental factors.The results showed that different vegetations varied greatly in soil organic carbon density：R 〉 S 〉 P,and the soil carbon density reduced with the increasing depth;soil CO2flux：S 〉 P 〉 R,and sample plot P and S showed unimodal changes.The peak values appeared at 14：00-15：00 p.m.;soil CO2 flux was negatively correlated with near-ground air humidity and carbon content,positively correlated with soil temperature and near-ground air temperature,and showed no obvious correlation with soil moisture.

Effects of elevated atmospheric CO_2 concentration and temperature on the soil profile methane distribution and diffusion in rice–wheat rotation system

The aim of this experiment was to determine the impacts of climate change on soil profile concentrations and diffusion effluxes of methane in a rice-wheat annual rotation ecosystem in Southeastern China. We initiated a field experiment with four treatments：ambient conditions（CKs）, CO2 concentration elevated to - 500 μmol/mol（FACE）,temperature elevated by ca. 2°C（T） and combined elevation of CO2 concentration and temperature（FACE ＋ T）. A multilevel sampling probe was designed to collect the soil gas at four different depths, namely, 7 cm, 15 cm, 30 cm and 50 cm. Methane concentrations were higher during the rice season and decreased with depth, while lower during the wheat season and increased with depth. Compared to CK, mean methane concentration was increased by 42%, 57% and 71% under the FACE, FACE ＋ T and T treatments, respectively, at the 7 cm depth during the rice season（p 〈 0.05）. Mean methane diffusion effluxes to the 7 cm depth were positive in the rice season and negative in the wheat season, resulting in the paddy field being a source and weak sink, respectively. Moreover, mean methane diffusion effluxes in the rice season were 0.94, 1.19 and 1.42 mg C/（m^2·hr） in the FACE,FACE ＋ T and T treatments, respectively, being clearly higher than that in the CK. The results indicated that elevated atmospheric CO2 concentration and temperature could significantly increase soil profile methane concentrations and their effluxes from a rice-wheat field annual rotation ecosystem（p 〈 0.05）.

Detecting the storage and change on topsoil organic carbon in grasslands of Inner Mongolia from 1980s to 2010s

Soil carbon sequestration and potential has been a focal issue in global carbon research. Under the background of global change, the estimation of the size as well as its change of soil organic carbon（SOC） storage is of great importance. Based on soil data from the second national soil survey and field survey during 2011–2012, by using the regression method between sampling soil data and remote sensing data, this paper aimed to investigate spatial distribution and changes of topsoil（0–20 cm） organic carbon storage in grasslands of Inner Mongolia between the 1980 s and 2010 s. The results showed that：（1） the SOC storage in grasslands of Inner Mongolia between the 1980 s and 2010 s was estimated to be 2.05 and 2.17 Pg C, with an average density of 3.48 and 3.69 kg C·m–2, respectively. The SOC storage was mainly distributed in the typical steppe and meadow steppe, which accounted for over 98% of the total SOC storage. The spatial distribution showed a decreased trend from the meadow steppe, typical steppe to the desert steppe, corresponding to the temperature and precipitation gradient.（2） SOC changes during 1982–2012 were estimated to be 0.12 Pg C, at 7.00 g C·m–2·yr–1, which didn＇t show a significant change, indicating that SOC storage in grasslands of Inner Mongolia remained relatively stable over this period. However, topsoil organic carbon showed different trends of carbon source/sink during the past three decades. Meadow steppe and typical steppe had sequestered 0.15 and 0.03 Pg C, respectively, served as a carbon sink; while desert steppe lost 0.06 Pg C, served as a carbon source. It appears that SOC storage in grassland ecosystem may respond differently to climate change, related to vegetation type, regional climate type and grazing intensity. These results might give advice to decision makers on adopting suitable countermeasures for sustainable grassland utilization and protection.