Overlapping Water and Nutrient Use Efficiencies and Carbon Assimilation between Coexisting Simple- and Compound-Leaved Trees from a Valley Savanna

Yang-Si-Ding Wang,Huai-Dong Wu,Jiao-Lin Zhang,Da Yang,Shu-Bin Zhang,Yun-Bing Zhang,Yong-Jiang Zhang

doi:10.3390/w12113037

Abstract

Identifying differences in ecophysiology between simple and compound leaves can help understand the adaptive significance of the compound leaf form and its response to climate change. However, we still know surprisingly little about differences in water and nutrient use, and photosynthetic capacity between co-occurring compound-leaved and simple-leaved tree species, especially in savanna ecosystems with dry-hot climate conditions. From July to September in 2015, we investigated 16 functional traits associated with water use, nutrients, and photosynthesis of six deciduous tree species (three simple-leaved and three compound-leaved species) coexisting in a valley-savanna in Southwest China. Our major objective was to test the variation in these functional traits between these two leaf forms. Overall, overlapping leaf mass per area (LMA), photosynthesis, as well as leaf nitrogen and phosphorus concentrations were found between these coexisting valley-savanna simple- and compound-leaved tree species. We didn’t find significant differences in water and photosynthetic nitrogen or phosphorus use efficiency between simple and compound leaves. Across these simple- and compound-leaved tree species, photosynthetic phosphorus use efficiencies were positively related to LMA and negatively correlated with phosphorus concentration per mass or area. Water use efficiency (intrinsic water use efficiency or stable carbon isotopic composition) was independent of all leaf traits. Similar ecophysiology strategies among these coexisting valley-savanna simple- and compound-leaved species suggested a convergence in ecological adaptation to the hot and dry environment. The overlap in traits related to water use, carbon assimilation, and stress tolerance (e.g., LMA) also suggests a similar response of these two leaf forms to a hotter and drier future due to the climate change.

Highlights

Plant leaves can be classified into two categories: a simple leaf with a single lamina and single rachis, and a compound leaf with multiple leaflets that occur in various arrangements along the rachis [1,2,3]
There was no significant difference in leaf mass per area (LMA) between compound- and simple-leaved species (Figure 1a, Table 2, p = 0.76)
We found no significant differences in concentration ratio (C/N), Photosynthetic nitrogen use efficiency (PNUE)

Summary

Introduction

Plant leaves can be classified into two categories: a simple leaf with a single lamina and single rachis, and a compound leaf with multiple leaflets that occur in various arrangements along the rachis [1,2,3]. Leaves as the main CO2-fixation organs, the diversity of leaf forms reflects the plant morphological and physiological adaptation [6]. An intact compound leaf may require larger within-leaf support for mechanical stability compared with a simple leaf [7,8], and the differences in leaf and stem properties between simple- and compound-leaved species may result in co-variation of morphology, physiology, and growth. We still know very little about the differences in eco-physiological adaptation between simple and compound leaf forms. Such knowledge will be useful to predict the comparative responses of these two leaf forms to rainfall patterns related to climate change

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Conclusion