Leaf lifespan is positively correlated with periods of leaf production and reproduction in 49 herb and shrub species

Abstract

Leaf life span and plant phenology are central elements in strategies for plant carbon gain and nutrient conservation. Although few studies have found that leaf life span correlate with the patterns of leaf dynamics and reproductive output, but there have not been sufficient conclusive tests for relationships between leaf life span and plant phenological traits, the forms and strengths of such relationships are poorly understood. This study was conducted with 49 herb and shrub species collected from the eastern portion of the Tibetan Plateau and grown together in a common garden setting. We investigated leaf life span, the periods of leaf production and death, the time lag between leaf production and death, and the period of plant reproduction (i.e., flowering and fruiting). Interspecific relationships of leaf life span with leaf dynamics and reproduction period were determined. Leaf production period was far longer than leaf death period and largely reflected the interspecific variation of leaf life span. Moreover, leaf life span was positively correlated with the length of reproduction (i.e., flowering and fruiting) period. These relationships were generally consistent across different subgroups of species (herbs vs. shrubs) and indicate potentially widely applicable relationships between LLS and aboveground phenology. We concluded that leaf life span is associated not simply with the dynamics of the leaf itself but with reproduction period. The results demonstrate a plant trade-off in resource allocation between production and reproduction and a coordinated arrangement of leaves, flowers, and fruits in their time investment. Our results provide insight into the relationship between leaf life span and plant phenology.

Keywords: Functional traits; interspecific relationship; leafing pattern; phenology; plant reproduction; trade‐offs; whole‐plant strategy.

Figure 1

Conceptual model describing leaf dynamics through the growing season. Each letter represents a key phenological date as follows: A, first leaf production; B, last leaf production; C, first leaf death; D, last leaf death. E and F, theoretical total leaf number. Dotted lines represent the end of the period of leaf production [BE] and end of period of leaf death [DF]. Solid lines link the cumulative number of leaves produced [AE] or lost [CF] through time. LP is the period of leaf production (solid arrow), LD is the period of leaf death (dashed arrow) and L is the time lag between the end of leaf production and the start of leaf death (dashed and dotted arrow).

Figure 2

Relationships between leaf life span (LLS) and (A) period of leaf production (LP), (B) time lag between the end of leaf production and the start of leaf death (L), (C) period of plant reproduction (R) and (D) period of plant growth (G) for the considered species: gray open circle, annual herb; black open circle, perennial herb; gray solid circle, subshrub; black solid circle, shrub. The regression line is fitted to all species.

Figure 3

Display of species traits along the first two PCA axes. Trait (roman) and species (italic) abbreviations are given in Table 1.