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夏季林火后降雨对南非易火灌丛中再萌芽型和再繁殖型种群恢复的影响存在差异。

Post-fire summer rainfall differentially affects reseeder and resprouter population recovery in fire-prone shrublands of South Africa.

机构信息

Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.

Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.

出版信息

Sci Total Environ. 2021 Sep 20;788:147699. doi: 10.1016/j.scitotenv.2021.147699. Epub 2021 May 13.

Abstract

Summer rainfall can have strong effects on post-fire mediterranean-type shrubland recovery patterns, with potentially long-lasting implications on communities. Our three-year field rainfall manipulation experiment tested post-fire survival and physiological responses of reseeders and resprouters to contrasting summer rainfall patterns in Fynbos and Renosterveld shrublands in South Africa. Climate projections are uncertain for this region but indicate that increased convective summer rainfall events could occur. We irrigated treatment plots during the hottest summer months (i.e. Jan, Feb, March) to contrast the naturally dry summer conditions. This allowed for assessments of the potential limiting effects of summer drought on post-fire vegetation recovery and the responsiveness of vegetation to moisture inputs during this time. Natural summer droughts led to leaf dehydration, reduced photosynthesis and reduced photosynthetic capacity. This had a particularly severe effect on reseeders during the first summer after fire leading to high mortality rates. Summer irrigations strongly reduced levels of reseeder stress and mortality. Resprouters in both vegetation types were physiologically less sensitive to rainfall patterns and showed little drought-related mortality. Comparisons of final population sizes with emergence and survival patterns showed that summer rainfall during the first summer after fire had the potential to strongly alter reseeder population sizes. The physiological sensitivity of plants to summer rainfall patterns was higher in shrubland communities occurring on fine-textured, moderately fertile soils (e.g. Renosterveld). Shrublands occurring on sandy, nutrient-poor soils (e.g. Fynbos) were remarkably insensitive to summer drought after the first summer with lower irrigation responses. Our study demonstrated the potential for variation in post-fire summer rainfall to strongly affect reseeder and resprouter population recovery patterns.

摘要

夏季降雨对火灾后地中海型灌木恢复模式有强烈影响,可能对群落产生长期影响。我们进行了为期三年的野外降雨操纵实验,测试了在南非的 Fynbos 和 Renosterveld 灌木林中,重新种子发芽和重新萌发植物对不同夏季降雨模式的火灾后生存和生理反应。该地区的气候预测不确定,但表明夏季对流降雨事件可能会增加。我们在最热的夏季月份(即 1 月、2 月和 3 月)对处理小区进行灌溉,以对比自然干旱的夏季条件。这使得我们可以评估夏季干旱对火灾后植被恢复的潜在限制作用,以及植被在这段时间对水分输入的响应能力。自然夏季干旱导致叶片脱水、光合作用减少和光合作用能力降低。这对火灾后第一个夏季的重新种子发芽植物产生了特别严重的影响,导致高死亡率。夏季灌溉强烈降低了重新种子发芽植物的应激和死亡率。两种植被类型的萌发植物对降雨模式的生理敏感性较低,与干旱相关的死亡率较小。最终种群大小与出现和生存模式的比较表明,火灾后第一个夏季的夏季降雨有可能强烈改变重新种子发芽植物的种群大小。在质地较细、中等肥沃土壤上(如 Renosterveld)发生的灌木林群落中,植物对夏季降雨模式的生理敏感性更高。在第一个夏季之后,在沙质、养分贫瘠的土壤上(如 Fynbos)发生的灌木林对夏季干旱的敏感性显著降低,灌溉响应较低。我们的研究表明,火灾后夏季降雨的变化可能会强烈影响重新种子发芽和萌发植物的种群恢复模式。

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