Plant functional trait change across a warming tundra biome

Bjorkman, A. D., Myers-Smith, I. H., Elmendorf, S. C., Normand, S., Rüger, N., Beck, P. S., ... & Georges, D. (2018). Plant functional trait change across a warming tundra biome. Nature, 562(7725), 57.

Abstract

The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature–trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.

Strong spatial relationships in traits across temperature and soil moisture 555 gradients are primarily explained by species turnover. a, Community-level (CWM) 556 variation in functional traits across space (N = 1520 plots within 117 sites within 72 regions) 557 as related to mean summer (warmest quarter) temperature and soil moisture, and b, 558 intraspecific variation (ITV) across space as related to summer temperature (note the log 559 scale for height and leaf area). c, Standardized effect sizes were estimated for all 560 temperature-trait relationships both across communities (CWM; solid bars) and within 561 species (ITV; striped bars). Effect sizes for CWM temperature-trait relationships were further 562 partitioned into the proportion of the effect driven solely by species turnover (light bars) and 563 abundance shifts (dark bars) over space. Dashed lines indicate the estimated total 564 temperature-trait relationship over space if intraspecific trait variability is also accounted for 565 (CWM: ITV). The contribution of ITV is estimated from the spatial temperature-trait 566 relationships modeled in (b). Soil moisture in (a) was modeled as continuous but is shown 567 predicted only at low and high values to improve visualization. Transparent ribbons in (a) 568 and (b) indicate 95% credible intervals for model mean predictions. Grey lines in (b) 569 represent intraspecific temperature-trait relationships for each species (height: N = 80 570 species, LDMC: N = 43, leaf area: N = 85, leaf N: N = 85, SLA: N = 108; N of observations 571 per trait shown in Table S1).