Life history strategies concerning water stress and photosynthetic capacity of four savanna tree species

Variable characteristics in the timing and extent of leaf-fall and green-up can be seen in savanna trees. This study investigated implications of these life history strategies for tree health (water stress and photosynthetic potential) in four savanna species: Afzelia quanzensis, Euclea divinorum, Colophospermum mopane and Terminalia sericea. The study took place in northern Kruger National Park, where C. mopane and T. sericea trees are abundant deciduous trees with similar strategies of the extent of leaf drop but with variation in the timing of leaf drop. C. mopane and T. sericea showed the highest measures of “water stress” and “photosynthetic potential” in comparison with A. quanzensis and E. divinorum. However, C. mopane trees were found to be able to maintain a greater leaf canopy at the same water potential range as T. sericea trees. This may play a role in the dominance of C. mopane in certain areas, but further investigation into the role of local soil and rainfall conditions would be necessary to supplement this finding.

稀树草原树木的落叶与返青的时间及程度均存在可变特征。本研究以4种稀树草原树种为研究对象，分别为Afzelia quanzensis、Euclea divinorum、Colophospermum mopane及Terminalia sericea，探究了这些生活史策略对树木健康（水分胁迫与光合潜力）的影响。本研究在克鲁格国家公园北部开展，该区域内Colophospermum mopane与Terminalia sericea为优势落叶树种，二者的落叶幅度策略相似，但落叶时间存在差异。相较于Afzelia quanzensis和Euclea divinorum，Colophospermum mopane与Terminalia sericea的水分胁迫与光合潜力指标均更高。然而，研究发现，在相同水势范围内，Colophospermum mopane能够维持比Terminalia sericea更为广阔的叶冠层。这或许是Colophospermum mopane在部分区域占据优势的原因之一，但仍需进一步探究当地土壤与降雨条件的作用，以补充该研究结论。