The carbon cycle of saline–alkali ecosystems will be affected to some extent in the context of future global warming. Therefore, we investigated the net ecosystem exchange (NEE) of three typical crops (wheat, maize and soybean) in the saline–alkaline land of the Yellow River Delta. To further investigate CO2 fluxes, NEE was decomposed into gross primary productivity (GPP) and ecosystem respiration (Re). In terms of seasonal variation, wheat and soybean were carbon sources in the early and late growth periods, and carbon sinks in the rest of the period, whereas maize was a carbon sink in the majority of the period, and maize had good carbon sink potential. The cumulative NEE during the growth periods for wheat, maize, and soybean were 414.86, 258.24 and 228.92 g cm−2, respectively, and the daily variation showed that the peak NEE values for the three crops preceded the peak values of both GPP and ecosystem respiration, occurring approximately at 12:00 a.m. In the correlation analysis, NEE and GPP of the three crops were well correlated with photosynthetic photon flux density and net radiation, whereas Re was significantly correlated with air temperature. Through a comparative analysis of CO2 fluxes within various agricultural ecosystems, our findings indicated that wheat demonstrated moderate carbon sequestration capabilities, whereas maize and soybean exhibited strong carbon sink characteristics. Notably, saline–alkali crops exhibited lower Re, whereas GPP levels remained at a moderate range. Therefore, under the global warming trend, the respiration of saline crops and soils will be affected and may change the original carbon sink into a carbon source. Hence, implementing suitable measures targeting saline–alkali areas, such as the establishment of an effective crop rotation system and the enhance saline–alkali land conditions, can reduce emissions of greenhouse gases, thus reducing the pressure of global warming and maintaining a stable carbon cycle in saline–alkali land.

中文翻译：

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全球变暖背景下盐碱土碳通量特征分析


未来全球变暖的背景下，盐碱生态系统的碳循环将受到一定影响。因此，我们调查了黄河三角洲盐碱地三种典型作物（小麦、玉米和大豆）的净生态系统交换（NEE）。为了进一步研究二氧化碳通量，NEE 被分解为总初级生产力 (GPP) 和生态系统呼吸 (Re)。从季节变化来看，小麦和大豆在生育前期和后期为碳源，其余时期为碳汇，而玉米在大部分时期为碳汇，玉米具有良好的碳汇潜力。小麦、玉米和大豆生育期的累计NEE分别为414.86、258.24和228.92 g cm−2，日变化表明三种作物的NEE峰值先于GPP和生态系统的峰值呼吸作用，发生在中午 12:00 左右。相关性分析中，三种作物的 NEE 和 GPP 与光合光子通量密度和净辐射具有良好的相关性，而 Re 与气温显着相关。通过对不同农业生态系统内二氧化碳通量的比较分析，我们的研究结果表明，小麦表现出中等的固碳能力，而玉米和大豆则表现出较强的碳汇特征。值得注意的是，盐碱作物的 Re 较低，而 GPP 水平仍保持在中等范围。因此，在全球变暖趋势下，盐碱作物和土壤的呼吸作用将受到影响，并可能将原有的碳汇转变为碳源。 因此，针对盐碱地区采取适当的措施，如建立有效的轮作制度、改善盐碱地条件等，可以减少温室气体的排放，从而减轻全球变暖的压力，维持稳定的碳循环。在盐碱地。