Subjects: Geosciences >> Geography submitted time 2024-07-04 Cooperative journals: 《干旱区研究》
Abstract： Soil nitrogen mineralization is a key process of soil nitrogen cycle, and temperature is one of the most important factors affecting soil nitrogen mineralization. Studying the effect of temperature on soil nitrogen mineralization characteristics in different successional stages is of great significance for understanding soil nitrogen cycle in terrestrial ecosystems. In this study, the communities in different successional stages of Xinglong Mountain in Gansu Province were taken as the research object. The indoor constant temperature aerobic culture method was used to study the soil nitrogen mineralization characteristics of five successional stages (grassland, shrub forest, Betula platyphylla forest, Picea wilsonii-Betula platyphylla forest and Picea wilsonii forest) under different temperatures (15 ℃, 25 ℃, 35 ℃). The results showed that: (1) Except for the 0~20 cm soil depth of grassland, the soil nitrogen mineralization rate of the other successional stages increased with the increase of temperature (15~35 ℃), and the cumulative mineralization of soil nitrogen in different successional stages increased with the increase of temperature. (2) With the positive advancement of succession, the soil nitrogen mineralization rate and cumulative mineralization amount of different successional stages showed a trend of increasing first and then decreasing. The soil nitrogen mineralization rate of Betula platyphylla forest was the highest, which was 1.63 times, 1.61 times, 1.25 times and 1.47 times that of grassland, shrub forest, Picea wilsonii-Betula platyphylla forest and Picea wilsonii forest, respectively. The soil nitrogen mineralization rate and cumulative mineralization amount of Picea wilsonii-Betula platyphylla forest were the highest, which were 0.68 times, 0.72 times, 0.84 times and 0.97 times of those of grassland, shrub forest, Betula platyphylla forest and Picea wilsonii forest, respectively. (3) With the increase of soil depth, the soil nitrogen mineralization rate and cumulative mineralization showed a decreasing trend, with the maximum in the 0~20 cm soil depth. (4) There were significant differences in the temperature sensitivity coefficient Q10 at 15 ℃ and 25 ℃ in different successional stages (P<0.05). With the positive succession, the temperature sensitivity coefficient Q10 decreased first and then increased. There was no significant difference in the temperature sensitivity coefficient Q10 between the communities at different succession stages at 25 ℃ and 35 ℃ (P>0.05). The results of this study will provide a theoretical basis for the evolution of soil quality and the dynamic change of soil nitrogen supply capacity in the community.
Subjects: Geosciences >> Geography submitted time 2023-08-26 Cooperative journals: 《干旱区研究》
Abstract： This study aims to examine the spatiotemporal variation characteristics of grassland vegetation coverat the regional scale and analyze its driving factors. The findings will provide a scientific reference and decisionmakingbasis for the scientific formulation of protection and restoration models, treatment measures, and thesustainable management of the grassland ecosystem in Ningxia, which are crucial for maintaining the balance ofthe regional grassland ecosystem and promoting ecological protection and high- quality development in theYellow River Basin. In this study, the NDVI time series dataset of SPOT/VEGETATION (2000-2019) was usedas the data source. The annual mean method, Theil- Sen Median trend analysis, and Mann- Kendall test wereemployed to study the spatiotemporal distribution and variation characteristics of grassland vegetation cover inNingxia. Furthermore, the Hurst index method was used to analyze the sustainability characteristics and futuredevelopment trends of grassland vegetation cover. Simultaneously, the influence of 13 factors, such as averageprecipitation, altitude, and gross domestic product, on the spatiotemporal distribution was quantified based on thegeographical detectors approach. The results show that from 2000 to 2019, the average annual NDVI ofvegetation in Ningxia grassland showed a fluctuating growth trend, with a growth rate of 0.005 per year. Theregional fluctuation was quite different, with extremely high and high vegetation cover areas concentrated in theLiupan Mountains and the irrigation area along the Yellow River. Overall, the NDVI change showed a low tomedium fluctuation trend, and the regional fluctuation was quite different. The vegetation cover conditionimproved significantly over the 20-year period, with a small degradation area and a favorable overall changetrend. However, 59.341% of the grasslands are projected to face potential risks of continuous degradation ortransformation from improvement to degradation in the future. The most sensitive environmental factorinfluencing grassland vegetation distribution response was precipitation, and climate and soil had the strongestinteraction explanatory power overall. The relationship between the factors affecting the distribution andvariation characteristics of grassland vegetation primarily manifested as mutual reinforcement or nonlinearenhancement, with no independent relationship between the factors. This study provides a scientific reference anddecision-making basis for the sustainable management of the grassland ecosystem in Ningxia.
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