Trade-off between the biomass and number of flowers in Stellera chamaejasme along an elevation gradient in a degraded alpine grassland

doi:10.3724/SP.J.1258.2014.00041

Abstract

Abstract:

Aims Trade-offs are the basis of the theory on plant life-history strategies, and the trade-off between flower size and flower number is an important determinant of flower biomass allocation. Our objective was to study the changes in the relationship between flower size and flower number in Stellera chamaejasme populations with elevation in Northwest China.
Methods The study site was located in a degraded alpine grassland on the northern slope in Qilian Mountains, Gansu Province, China. Survey and sampling were carried out at four elevations at intervals of 100 m from 2700 m to 3000 m; a GPS was used to determine the elevation. Community traits were investigated and 45 individuals of S. chamaejasme were collected randomly at each elevation. The samples were cleaned and divided into different organs, and their biomass were then measured after being dried at 80 °C in an oven.
Important findings With increasing elevation, the height, density, and aboveground biomass of the plant communities displayed a pattern of initial increase and then followed by a subsequent decline; the flower biomass in S. chamaejasme increased with increasing elevation, while the flower numbers decreased. The flower size was negatively correlated with the flower number, but the relationship varied along the elevation gradient; there was a highly significant negative correlation (p < 0.01) between the flower size and the flower number at elevations 2700, 2900, and 3000 m, whereas the correlation only reached a significant level (p < 0.05) at the elevation of 2800 m, indicating that there is a trade-off between the flower size and flower number. The elevation of 2800 m appeared to be a switching point where the S. chamaejasme individuals with more but smaller flowers at the lower elevations were transformed into ones with fewer but bigger flowers with increasing elevation. Consequently, a change in the reproductive strategy with a trade-off between flower size and flower number ensures successful reproduction of the S. chamaejasme populations in adverse environments.

Key words: degraded alpine grassland, elevation, flower number, flower size, Stellera chamaejasme, trade-off

ZHANG Qian,ZHAO Cheng-Zhang,DONG Xiao-Gang,MA Xiao-Li,HOU Zhao-Jiang,LI Yu. Trade-off between the biomass and number of flowers in Stellera chamaejasme along an elevation gradient in a degraded alpine grassland[J]. Chin J Plant Ecol, 2014, 38(5): 452-459.

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URL: https://www.plant-ecology.com/EN/10.3724/SP.J.1258.2014.00041

https://www.plant-ecology.com/EN/Y2014/V38/I5/452

Figures/Tables 5

Table 1 Community characteristics and air temperature along elevation gradient (mean ± SE)

海拔 Elevation (m)	群落特征 Community characteristics			气温 Air temperature (℃)
海拔 Elevation (m)	高度 Height (cm)	密度 Density (branch·m^-2)	地上生物量 Aboveground biomass (g·m^-2)	气温 Air temperature (℃)
2 700	15.87 ± 0.82^b	797 ± 40.26^d	148 ± 7.24^c	9.23 ± 0.42^a
2 800	18.64 ± 0.92^a	1185 ± 58.84^c	179 ± 9.05^b	8.86 ± 0.26^a
2 900	15.35 ± 0.74^b	1526 ± 75.31^a	207 ± 11.17^a	8.17 ± 0.19^b
3 000	10.27 ± 0.45^c	1405 ± 64.33^b	194 ± 9.21^a	7.03 ± 0.13^c

Table 2 Biological characteristics of Stellera chamaejasme among the elevation gradient (mean ± SE)

海拔 Elevation (m)	地上生物量 Aboveground biomass (g·m^-2)	株高 Plant height (cm)	分枝数 Branch number
2 700	16.37 ± 0.85^a	22.56 ± 1.03^a	14.87 ± 0.82^a
2 800	12.98 ± 0.74^b	18.23 ± 0.88^b	11.64 ± 0.61^b
2 900	10.34 ± 0.53^c	12.17 ± 0.62^c	9.96 ± 0.48^c
3 000	8.92 ± 0.41^c	8.25 ± 0.36^d	7.14 ± 0.28^c

Fig. 1 Changes in flower size and flower number in Stellera chamaejasme along elevation gradient (mean ± SE). Different small letters indicate significant differences among different elevation (p < 0.05).

Fig. 2 Relationship between flower size and flower number in Stellera chamaejasme among different elevations. A, Elevation of 2700 m. B, Elevation of 2800 m. C, Elevation of 2900 m. D, Elevation of 3000 m.

Fig. 3 Changes in reproductive allocation in Stellera cham- aejasme along elevation gradient (mean ± SE). Different small letters indicate significant differences among different elevation (p < 0.05).

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