Change in community traits over tim

Change in community traits over timePlant height was the only trait for which the CWM changed over the 27 years of monitoring; it increased rapidly at nearly every survey site (Fig. 3a, b, Extended Data Fig. 3 and Supplementary Table 6). Interannual variation in community height was sensitive to summer temperature (Fig. 3c, Extended Data Fig. 2 and Supplementary Table 7), indicating that increases in community height are responding to warming. However, neither the total rate of temperature change nor soil moisture predicted the total rate of CWM change in any trait (Extended Data Fig. 5 and Supplementary Table 8). Incorporating potential ITV doubled the average estimate of plant height change over time (Figs. 3a, 4a, dashed lines). Because spatial patterns in ITV can be due to both phenotypic plasticity and genetic differences among populations, this is likely to be a maximum estimate of the ITV contribution to trait change (for example, if intraspecific temperature–trait relationships are due entirely to phenotypic plasticity). The observed increase in community height is consistent with previous findings of increasing vegetation height in response to experimental warming at a subset of these sites28 and with studies showing increased shrub growth over time11.