Semi-arid and arid regions are characterised by drying and rewetting events, salinity as well as fires. The effects of these stresses on soils are all related to water availability and have been investigated extensively, but usually separately. To study the impact of two stresses, we combined a short heating event as it may occur in fast-moving grass fires with either a drying and rewetting event or salinity. In the first experiment, soils were incubated air-dried, moderately dried and constantly moist for 7 days after which the dried soils were rewetted. Seven days after rewetting, half of the replicates from each treatment were heated and then maintained at 60 °C for 30 min followed by rapid rewetting, while others remained unheated. The rewetting flush of respiration after 7 days was greater in previously air-dried soil than moderately dry soil. Regardless of prior water treatment, heating followed by rewetting compared to constantly moist soil increased respiration threefold and available N and P by about 20–30%. In the second experiment, NaCl was added to non-saline soil (EC 1:5 0.01 dS m −1 ) to achieve EC 1:5 1 and 4 ds m −1 (referred to as NS, S1 and S4). Soils were incubated moist for 1 month and then amended with pea residue at 10 g kg −1 . Five days after residue amendment, half of the replicates from each treatment were heated and rewetted as in the first experiment. In unheated S4 compared to NS, cumulative respiration was 30% lower and available N and P were threefold and 30% higher. Heating reduced cumulative respiration by 10% in NS and S1 but by 30% in S4. Compared to unheated treatments, available N in heated NS was up to tenfold higher, but in S4, heating increased available N only up to threefold. In all salinity treatments, heating increased available P by about 15%. It can be concluded that the impact of short-term heating on nutrient availability and soil respiration was not affected by prior drying and rewetting. High salinity on the other hand reduced the impact on nutrient availability whereas the effect on soil respiration was exacerbated compared to non-saline soil.

中文翻译：

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加热后的土壤呼吸和养分有效性受盐度影响，但不受先前干燥和再润湿的影响

半干旱和干旱地区的特点是干燥和再湿润事件、盐度和火灾。这些压力对土壤的影响都与水的可用性有关，并且已经进行了广泛的研究，但通常是分开的。为了研究两种压力的影响，我们将一个短暂的加热事件与干燥和再润湿事件或盐度结合起来，因为它可能发生在快速移动的草火中。在第一个实验中，将土壤风干、适度干燥和持续湿润培养 7 天，然后再润湿干燥的土壤。再润湿 7 天后，将每个处理的一半重复加热，然后在 60°C 下保持 30 分钟，然后快速再润湿，而其他的则保持不加热。7 天后呼吸的再润湿潮红在先前风干的土壤中比中度干燥的土壤更大。无论之前的水处理如何，加热后再润湿与持续潮湿的土壤相比，呼吸增加了三倍，有效氮和磷增加了约 20-30%。在第二个实验中，将 NaCl 添加到非盐分土壤 (EC 1:5 0.01 dS m -1 ) 以实现 EC 1:5 1 和 4 ds m -1 (称为 NS、S1 和 S4)。将土壤湿润培养 1 个月，然后用 10 g kg -1 的豌豆残留物进行修正。残留修正后五天，每个处理的一半重复像在第一个实验中一样加热和再润湿。在未加热的 S4 中，与 NS 相比，累积呼吸降低了 30%，可用 N 和 P 增加了三倍和 30%。加热使 NS 和 S1 的累积呼吸减少了 10%，但在 S4 中减少了 30%。与未加热处理相比，加热 NS 中的有效氮高出十倍，但在 S4 中，加热使可用 N 仅增加了三倍。在所有盐度处理中，加热使有效磷增加了约 15%。可以得出结论，短期加热对养分有效性和土壤呼吸的影响不受先前干燥和再润湿的影响。另一方面，与非盐分土壤相比，高盐度降低了对养分有效性的影响，而对土壤呼吸的影响则加剧。