Plant Origin Regulates the Response of Solidago canadensis Reproductive Traits to Long-Term Warming and Nitrogen Addition

Abstract

Climate warming and nitrogen (N) deposition have already occurred and will continue to occur, profoundly affecting exotic plant invasion. Most studies on the effects of climate change focus on plant growth, biomass, and leaf traits, with limited reports on reproductive responses. We selected Solidago canadensis from North America and China as focal species and conducted a long-term common garden experiment simulating climate warming and N deposition to examine how climate warming, N addition, and plant origin influence its reproductive traits. Chinese Solidago canadensis exhibited significantly greater ramet height, more robust ramet diameters, longer and wider inflorescences, and higher seed mass compared to North American Solidago canadensis. Long-term warming and plant origin alone or in combination significantly influenced reproductive traits, while N addition did not influence these traits. The vegetative propagation of a native population was sensitive to warming and N addition, while the generative propagation of an invasive population was sensitive to their combined effects. These findings suggest that the reproductive strategies of Solidago canadensis varied with their origin, and plant origin might be important in mediating climate change effects on their reproduction under plant invasion.

Keywords: Solidago canadensis; climate warming; plant invasion; provenance; reproduction.

Figure 1

The effects of warming, nitrogen addition, and origin on the ramet numbers (a), height (b), and diameter (c) of S. canadensis. Note: SNA: S. canadensis from North America; SCN: S. canadensis from China; A: ambient; N: N addition; W: warming; W + N: warming plus N addition. In a and b, the hollow points represent the mean of each measurement ± SE for SCN and SNA, while the solid points indicate the average of measurements ± SE (n = 6). In c, transparent points are observed values, and solid points represent the mean ± SE (n = 18). ** p < 0.01 indicate significant differences in reproductive traits between SNA and SCN.

Figure 2

The effects of warming, nitrogen addition, and origin on the inflorescence length (a), width (b), and thousand seed mass (c) of S. canadensis. Note: Transparent points are observed values and solid points represent the mean ± SE (n = 60 for inflorescence length and width; n = 5 for thousand seed mass). SNA: S. canadensis from North America; SCN: S. canadensis from China; A: ambient; N: N addition; W: warming; W + N: warming plus N addition. * p < 0.05 and ** p < 0.01 indicate significant differences in reproductive traits between SNA and SCN.

Figure 3

The relative changes in reproductive traits of S. canadensis from SNA and SCN under warming, N addition, and their combination. Note: The data in the graph represent the mean ± SE (n = 6 for ramet number and ramet height; n = 6 for ramet diameter; n = 6 for inflorescence length and width; n = 5 for thousand seed mass). SNA: S. canadensis from North America; SCN: S. canadensis from China; W + N: warming plus N addition.

Figure 4

Linear regression relationship of reproductive traits of S. canadensis from different origins. (a) the linear regression relationship between ramet height and ramet number, (b) the linear regression relationship between ramet diameter and ramet number, (c) the linear regression relationship between ramet height and ramet diameter, (d) the linear regression relationship between thousand seed mass and inflorescence length, (e) the linear regression relationship between inflorescence width and inflorescence length, and (f) the linear regression relationship between thousand seed mass and inflorescence width. Note: SNA: S. canadensis from North America; SCN: S. canadensis from China The blue solid points (n = 11–24) and blue solid line represent SNA, while the red solid points (n = 14–29) and red solid line represent SCN.

Figure 5

The Mantel test for the associations of warming, N addition, and plant origin with reproductive traits of S. canadensis. The line color indicates the Mantel test p-value of the association between environmental factors and reproductive traits, the brown line represents 0.01 < p < 0.05, the blue line represents p < 0.01, and the gray line represents p ≥ 0.05. The line width corresponds to the Mantel test r value. The color of the box represents pairwise correlations between reproductive traits, with deeper color saturation denoting stronger correlation. Note: IL: inflorescence length; IW: inflorescence width; H: ramet height; D: ramet diameter; TSM: thousand seed mass; RN: ramet number.

Figure 6

Pathway models examining the impacts of climate warming, N addition, or/and plant origin on vegetative and generative propagation. The red solid arrow indicates a significant negative association between explanatory and response variables, the blue solid arrow indicates a significant positive association between explanatory and response variables, and the gray dashed arrow indicates a nonsignificant association between explanatory and response variables. The width of a solid arrow indicates the intensity of associations; the numbers associated with pathways represent standard path coefficients.

Figure 7

The experimental design involving three factors (Factor 1: origin; Factor 2: temperature; Factor 3: N addition). The plant origins are S. canadensis from North America (SNA) and S. canadensis from China (SCN). The four climate scenarios are the ambient (A), climate warming (W), N addition (N), and climate warming plus N addition environment (W + N).