Subjects: Geosciences >> Geography submitted time 2021-06-13 Cooperative journals: 《干旱区研究》
Abstract：土壤有机碳（SOC）是生态系统稳定性和农业生产力的基础，充分了解焉耆盆地绿洲不同土壤类型SOC分布特征，对实现农业系统可持续发展具有重要意义。以新疆焉耆盆地绿洲长期定点试验的监测数据为基础，利用生物地球化学模型（DNDC）进行模拟试验，研究在当前的田间管理和气候模式下，焉耆盆地绿洲农田土壤有机碳密度（SOCD）和土壤有机碳储量（SOCS）的空间分布特征，并探究了在不同的土壤类型下SOCD和SOCS的差异性。结果表明：（1）DNDC模型能够很好的模拟该区域下SOC及其动态变化，模型相关系数（r）>92.75%，相对误差（E）介于2.98%~4.12%，<5%，模型的可靠性较高。（2）2018年焉耆盆地绿洲农田0~20 cm SOCD介于12000~28000 kg·hm-2，SOCS为2414 Gg，不同区域之间的差异较为明显。（3）不同的土壤类型之间，SOCD和SOCS差异明显，其中沼泽土的SOCD最大，为25136 kg·hm-2；石质土的SOCD最小，为13335 kg·hm-2。
Subjects: Biology >> Botany >> Applied botany submitted time 2023-07-13 Cooperative journals: 《广西植物》
Abstract： Nitrate is predominant in the karst soils. However, the temporal and spatial heterogeneity was observed for the nitrate content in the soils. Hence, the Morus alba seedlings grown in karst regions may suffer from low nitrogen stress. In order to provide a scientific management of inorganic nitrogen for M. alba seedlings grown in karst regions, the M. alba seedlings were used as the experimental materials in this study. The M. alba seedlings were grown hydroponically with a modified Hoagland solution. NaNO3, with a δ15N of 22.35‰, was employed as the sole nitrogen source at three concentrations (0.5, 2, and 8 mmol·L-1) in this study. The photosynthetic characteristics, dry weight, carbon content, nitrogen content and δ15N values of the leaves, stems and roots of the M. alba seedlings were measured in this study. The physiological response to different nitrogen supply levels was analyzed for M. alba seedlings. The relationship between internal nitrogen demand and external nitrogen supply of M. alba seedlings was estimated based on the stable nitrogen isotope fractionation values at the whole-plant scale. The carbon-nitrogen coupling relationship was studied based on the nitrogen accumulation amount and carbon accumulation amount in the whole plant. The results were as follows ： (1) When the nitrate concentrations ranged from 0.5 to 2 mmol·L-1, increasing nitrate concentrations significantly increased the chlorophyll content and net photosynthetic rate of the M. alba seedlings, which in turn significantly promoted the biomass accumulation. However, when the nitrate concentration exceeded 2 mmol·L-1, more nitrate supply (8 mmol·L-1) did not lead to a significant increase in the chlorophyll content, net photosynthetic rate and biomass. (2) Increasing the nitrate supply could promote the nitrogen assimilation in M. alba seedlings. The nitrogen accumulation amount in M. alba seedlings gradually increased with increasing nitrate supply. However, the carbon accumulation amount in M. alba seedlings did not change significantly at nitrate concentrations of 2 mmol·L-1 and 8 mmol·L-1; (3) The stable nitrogen isotope fractionation values of the nitrate assimilates in the whole M. alba seedlings reached the minimum value at 2 mmol·L-1 nitrate. Therefore, the inorganic nitrogen supply at the nitrate concentration of 2 mmol·L-1 is close to the internal nitrogen demand of M. alba seedlings, and the close balance between external nitrogen supply and internal nitrogen demand of the plants means an effective coordination of carbon and nitrogen metabolism in plants, thus achieving a simultaneous increase in carbon and nitrogen assimilates.
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