Norm of reaction for four species at two soil nutrients (N), water (W) and population density (D) levels on morphological traits; + and − indicate two levels of factor; The data represent means ± SD of average across treatments; ns denote not significance (<i>P</i>>0.05), asterisks denote significance at <i>P</i><0.05 (*), <i>P</i><0.01 (**) and <i>P</i><0.001 (***) for each species in different level environmental treatments; the same lower case letters within columns are not significantly different at <i>P</i><0.05 in low level environmental treatment for four species; the same capital letters within columns are not significantly different at <i>P</i><0.05 in high level environmental treatments for four species.

<p>Sig, the <i>P</i> value of interactions between traits and environmental factors when compared between <i>C. acuminatum</i> and early succession species (<i>A. squarrosum</i> and <i>C. macrocarpum</i>) and between <i>S. collina</i> and early succession species (<i>A. squarrosum</i> and <i>C. macrocarpum</i>).</p

Log10-log10 plots showing the relationship between reproductive biomass and vegetative biomass of (a) <i>A. squarrosum</i> (black), <i>C. macrocarpum</i> (red), <i>C. acuminatum</i> (green) and <i>S. collina</i> (blue); and SMA fit line for combining all early successional species (cyan dashed line) and combining all late successional species (magenta solid line).

<p>For b (soil nutrient treatments), c (soil water treatments), and d (population density treatments), low environmental level (circle points and solid line) and high soil nutrient treatment level (triangle points and dashed line), black, red, green and blue, respectively for <i>A. squarrosum</i>, <i>C. macrocarpum</i>, <i>C. acuminatum</i> and <i>S. collina</i>, and SMA fit line for combining all low environmental levels (cyan dashed line) and combining all high environmental levels (magenta solid line).</p

Analysis of variance for plant traits of four species under soil nutrients, water, and population densities.

<p><i>F</i>-values are presented.</p>*<p>refers to significance at <i>P</i><.05;</p>**<p>to significance at <i>P</i><.01;</p>***<p>to significance at <i>P</i><.001.</p

Results of standardized major axis regression (SMA) analysis of pairwise combinations of reproductive biomass and vegetative biomass for combining all species in different treatments.

<p>Significant results (P<0.05) are shown in bold.</p

Results of standardized major axis regression (SMA) analysis of pairwise combinations of reproductive biomass and vegetative biomass for each species in different treatments.

<p><i>P</i>1 is the test of slope homogeneity, <i>P</i>2 is the test of shift in elevation, <i>P</i>3 is the test of Shift along slope. Significant results (P<0.05) are shown in bold.</p

Norm of reaction for four species at two soil nutrients (N), water (W) and population density (D) levels on total biomass and reproductive effort of four species; + and − indicate two levels of factor.

<p>The data represent means ± SD of average across treatments; Asterisks denote significance at <i>P</i>>0.05 (ns), <i>P</i><0.05 (*), <i>P</i><0.01 (**) and <i>P</i><0.001 (***) for each species in different level environmental treatment; the same lower case letters within columns are not significantly different at <i>P</i><0.05 in low level environmental treatments for four species; Same capital letters within columns are not significantly different at <i>P</i><0.05 in high level environmental treatment for four species. Sig, the <i>P</i> value of interactions of between total biomass and environmental factor when compared between <i>C. acuminatum</i> and early succession species (<i>A. squarrosum</i> and <i>C. macrocarpum</i>) and between <i>S. collina</i> and early succession species (<i>A. squarrosum</i> and <i>C. macrocarpum</i>).</p

Germination Shifts of C₃ and C₄ Species under Simulated Global Warming Scenario

<div><p>Research efforts around the world have been increasingly devoted to investigating changes in C₃ and C₄ species' abundance or distribution with global warming, as they provide important insight into carbon fluxes and linked biogeochemical cycles. However, changes in the early life stage (e.g. germination) of C₃ and C₄ species in response to global warming, particularly with respect to asymmetric warming, have received less attention. We investigated germination percentage and rate of C₃ and C₄ species under asymmetric (+3/+6°C at day/night) and symmetric warming (+5/+5°C at day/night), simulated by alternating temperatures. A thermal time model was used to calculate germination base temperature and thermal time constant. Two additional alternating temperature regimes were used to test temperature metrics effect. The germination percentage and rate increased continuously for C₄ species, but increased and then decreased with temperature for C₃ species under both symmetric and asymmetric warming. Compared to asymmetric warming, symmetric warming significantly overestimated the speed of germination percentage change with temperature for C₄ species. Among the temperature metrics (minimum, maximum, diurnal temperature range and average temperature), maximum temperature was most correlated with germination of C₄ species. Our results indicate that global warming may favour germination of C₄ species, at least for the C₄ species studied in this work. The divergent effects of asymmetric and symmetric warming on plant germination also deserve more attention in future studies.</p></div

Thermal time model parameter estimates (<i>T_b</i>, minimum temperature; <i>θ</i>₁, thermal time constant) for C₄ and C₃ species under the symmetric warming (SW) and asymmetric warming (AW) alternating temperature regimes.

<p>Thermal time model parameter estimates (<i>T_b</i>, minimum temperature; <i>θ</i>₁, thermal time constant) for C₄ and C₃ species under the symmetric warming (SW) and asymmetric warming (AW) alternating temperature regimes.</p

Germination rates of C₄ and C₃ species under different alternating temperature regimes.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0105139#pone-0105139-g001" target="_blank">Fig. 1</a> for symbols.</p

Pearson correlation analysis of germination percentage (GP) and germination rate (GR) with temperature metrics (TM, minimum, maximum, average, diurnal temperature range (DTR)) from the four alternating temperature regimes for C₄ and C₃ species (<i>r</i>, correlation coefficient; <i>P</i>, probability for the correlation).

<p>Pearson correlation analysis of germination percentage (GP) and germination rate (GR) with temperature metrics (TM, minimum, maximum, average, diurnal temperature range (DTR)) from the four alternating temperature regimes for C₄ and C₃ species (<i>r</i>, correlation coefficient; <i>P</i>, probability for the correlation).</p