Contrasting trait responses in plant communities to experimental and geographic variation in precipitation

Abstract

Summary Patterns of precipitation are likely to change significantly in the coming century, with important but poorly understood consequences for plant communities. Experimental and correlative studies may provide insight into expected changes, but little research has addressed the degree of concordance between these approaches. We synthesized results from four experimental water addition studies with a correlative analysis of community changes across a large natural precipitation gradient in the United States. We investigated whether community composition, summarized with plant functional traits, responded similarly to increasing precipitation among studies and sites. In field experiments, increased precipitation favored species with small seed size, short leaf life span and high leaf nitrogen (N) concentration. However, with increasing precipitation along the natural gradient, community composition shifted towards species with higher mean seed mass, longer leaf life span and lower leaf N concentrations. The differences in temporal and spatial scale of experimental manipulations and natural gradients may explain these contrasting results. Our results highlight the complexity of responses to climate change, and suggest that transient dynamics may not reflect long‐term shifts in functional diversity and community composition. We propose a model of community change that incorporates these differences between short‐ and long‐term responses to climate change.

Climate-driven diversity loss in a grassland community

“…Variation among species in mean specific leaf area (SLA; leaf area/dry mass; or its inverse, termed leaf mass per unit area) has been found to correlate well with among-species variation in key physiological attributes such as leaf longevity (LL), water use efficiency (WUE), and relative growth rate (RGR). Species with high SLA and RGR, and low LL and WUE, are more prevalent in wetter climates (34) and in wetter years (35) and tend to increase disproportionately in response to experimental watering (36) and natural precipitation increase (37). Several previous studies have found that high-SLA species are especially vulnerable to decline or loss under aridification (38,39).…”

Trait-based community assembly of understory palms along a soil nutrient gradient in a lower montane tropical forest

“…The importance of intraspecific variation in determining trait-environmental relationships and trait-based community assembly is becoming increasingly recognized (Ashton et al 2010;Jung et al 2010;Sandel et al 2010). We examined trait plasticity in G. cuneata, which occurred across all sites examined here and was also the most abundant species at most sites (Andersen et al 2010a).…”

“…Habitat filtering can lead to changes in trait composition along environmental gradients as a result of either turnover in species composition or differences in species abundance (Keddy 1992;Cornwell and Ackerly 2009;Sandel et al 2010) or intraspecific variation due to plasticity or genetic variation (Cornwell and Ackerly 2009;Hulshof and Swenson 2010;Jung et al 2010). Whereas most trait-based studies focus on species mean trait values, recent work has incorporated intraspecific variation to trait-based frameworks, adding a greater power to detect trait-environment linkages (Cornwell and Ackerly 2009;Hulshof and Swenson 2010;Jung et al 2010).…”

“…In addition, tropical montane forests are expected to be impacted disproportionately by climate change as rising cloud-bases (Pounds et al 1999;Foster 2001) and increasing nitrogen deposition in tropical latitudes directly affect ecosystem function (Foster 2001;Corre et al 2010). The use of trait-based studies to explore the mechanisms underlying species distributions along natural environmental gradients can provide a means for 4u Sprin: ger prediction of community-wide shifts with changing climate and nutrient regimes (Diaz and Cabido 1997;Lavorel and Gamier 2002;Sandel et al 2010). Here, we examine plant functional traits and species distribution patterns in relation to soil nutrient, light, and rainfall gradients in a lower montane forest in western Panama.…”

“…Trait-based approaches have linked community structure and ecosystem function along various resource gradients (Reich et al 2003), particularly light (Poorter 1999;Poorter and Bongers 2006) and water (Wright et al 2001;Engelbrecht et al 2007;Sandel et al 2010) and to lesser extent soil nutrient (Wright et al 2001;Cavender-Bares et al 2004) gradients. Furthermore, the examination of leaf functional traits along resource gradients has led to hypotheses regarding plant strategies on local to global scales (Reich et al 2003;Lavorel and Gamier 2002) and to insights into processes generating community structure (Keddy 1992;Kraft et al 2008;Ackerly and Cornwell 2007).…”