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1.  Meta-analysis reveals profound responses of plant traits to glacial CO2 levels 
Ecology and Evolution  2013;3(13):4525-4535.
A general understanding of the links between atmospheric CO2 concentration and the functioning of the terrestrial biosphere requires not only an understanding of plant trait responses to the ongoing transition to higher CO2 but also the legacy effects of past low CO2. An interesting question is whether the transition from current to higher CO2 can be thought of as a continuation of the past trajectory of low to current CO2 levels. Determining this trajectory requires quantifying the effect sizes of plant response to low CO2. We performed a meta-analysis of low CO2 growth experiments on 34 studies with 54 species. We quantified how plant traits vary at reduced CO2 levels and whether C3 versus C4 and woody versus herbaceous plant species respond differently. At low CO2, plant functioning changed drastically: on average across all species, a 50% reduction in current atmospheric CO2 reduced net photosynthesis by 38%; increased stomatal conductance by 60% and decreased intrinsic water use efficiency by 48%. Total plant dry biomass decreased by 47%, while specific leaf area increased by 17%. Plant types responded similarly: the only significant differences being no increase in SLA for C4 species and a 16% smaller decrease in biomass for woody C3 species at glacial CO2. Quantitative comparison of low CO2 effect sizes to those from high CO2 studies showed that the magnitude of response of stomatal conductance, water use efficiency and SLA to increased CO2 can be thought of as continued shifts along the same line. However, net photosynthesis and dry weight responses to low CO2 were greater in magnitude than to high CO2. Understanding the causes for this discrepancy can lead to a general understanding of the links between atmospheric CO2 and plant responses with relevance for both the past and the future.
PMCID: PMC3856751  PMID: 24340192
CO2; glacial; growth; meta-analysis; photosynthesis; plant traits; subambient CO2
2.  TRY – a global database of plant traits 
Kattge, J | Díaz, S | Lavorel, S | Prentice, I C | Leadley, P | Bönisch, G | Garnier, E | Westoby, M | Reich, P B | Wright, I J | Cornelissen, J H C | Violle, C | Harrison, S P | Van Bodegom, P M | Reichstein, M | Enquist, B J | Soudzilovskaia, N A | Ackerly, D D | Anand, M | Atkin, O | Bahn, M | Baker, T R | Baldocchi, D | Bekker, R | Blanco, C C | Blonder, B | Bond, W J | Bradstock, R | Bunker, D E | Casanoves, F | Cavender-Bares, J | Chambers, J Q | Chapin, F S | Chave, J | Coomes, D | Cornwell, W K | Craine, J M | Dobrin, B H | Duarte, L | Durka, W | Elser, J | Esser, G | Estiarte, M | Fagan, W F | Fang, J | Fernández-Méndez, F | Fidelis, A | Finegan, B | Flores, O | Ford, H | Frank, D | Freschet, G T | Fyllas, N M | Gallagher, R V | Green, W A | Gutierrez, A G | Hickler, T | Higgins, S I | Hodgson, J G | Jalili, A | Jansen, S | Joly, C A | Kerkhoff, A J | Kirkup, D | Kitajima, K | Kleyer, M | Klotz, S | Knops, J M H | Kramer, K | Kühn, I | Kurokawa, H | Laughlin, D | Lee, T D | Leishman, M | Lens, F | Lenz, T | Lewis, S L | Lloyd, J | Llusià, J | Louault, F | Ma, S | Mahecha, M D | Manning, P | Massad, T | Medlyn, B E | Messier, J | Moles, A T | Müller, S C | Nadrowski, K | Naeem, S | Niinemets, Ü | Nöllert, S | Nüske, A | Ogaya, R | Oleksyn, J | Onipchenko, V G | Onoda, Y | Ordoñez, J | Overbeck, G | Ozinga, W A | Patiño, S | Paula, S | Pausas, J G | Peñuelas, J | Phillips, O L | Pillar, V | Poorter, H | Poorter, L | Poschlod, P | Prinzing, A | Proulx, R | Rammig, A | Reinsch, S | Reu, B | Sack, L | Salgado-Negret, B | Sardans, J | Shiodera, S | Shipley, B | Siefert, A | Sosinski, E | Soussana, J-F | Swaine, E | Swenson, N | Thompson, K | Thornton, P | Waldram, M | Weiher, E | White, M | White, S | Wright, S J | Yguel, B | Zaehle, S | Zanne, A E | Wirth, C
Global Change Biology  2011;17(9):2905-2935.
Plant traits – the morphological, anatomical, physiological, biochemical and phenological characteristics of plants and their organs – determine how primary producers respond to environmental factors, affect other trophic levels, influence ecosystem processes and services and provide a link from species richness to ecosystem functional diversity. Trait data thus represent the raw material for a wide range of research from evolutionary biology, community and functional ecology to biogeography. Here we present the global database initiative named TRY, which has united a wide range of the plant trait research community worldwide and gained an unprecedented buy-in of trait data: so far 93 trait databases have been contributed. The data repository currently contains almost three million trait entries for 69 000 out of the world's 300 000 plant species, with a focus on 52 groups of traits characterizing the vegetative and regeneration stages of the plant life cycle, including growth, dispersal, establishment and persistence. A first data analysis shows that most plant traits are approximately log-normally distributed, with widely differing ranges of variation across traits. Most trait variation is between species (interspecific), but significant intraspecific variation is also documented, up to 40% of the overall variation. Plant functional types (PFTs), as commonly used in vegetation models, capture a substantial fraction of the observed variation – but for several traits most variation occurs within PFTs, up to 75% of the overall variation. In the context of vegetation models these traits would better be represented by state variables rather than fixed parameter values. The improved availability of plant trait data in the unified global database is expected to support a paradigm shift from species to trait-based ecology, offer new opportunities for synthetic plant trait research and enable a more realistic and empirically grounded representation of terrestrial vegetation in Earth system models.
PMCID: PMC3627314
comparative ecology; database; environmental gradient; functional diversity; global analysis; global change; interspecific variation; intraspecific variation; plant attribute; plant functional type; plant trait; vegetation model
3.  Is leaf dry matter content a better predictor of soil fertility than specific leaf area? 
Annals of Botany  2011;108(7):1337-1345.
Background and Aims
Specific leaf area (SLA), a key element of the ‘worldwide leaf economics spectrum’, is the preferred ‘soft’ plant trait for assessing soil fertility. SLA is a function of leaf dry matter content (LDMC) and leaf thickness (LT). The first, LDMC, defines leaf construction costs and can be used instead of SLA. However, LT identifies shade at its lowest extreme and succulence at its highest, and is not related to soil fertility. Why then is SLA more frequently used as a predictor of soil fertility than LDMC?
SLA, LDMC and LT were measured and leaf density (LD) estimated for almost 2000 species, and the capacity of LD to predict LDMC was examined, as was the relative contribution of LDMC and LT to the expression of SLA. Subsequently, the relationships between SLA, LDMC and LT with respect to soil fertility and shade were described.
Key Results
Although LD is strongly related to LDMC, and LDMC and LT each contribute equally to the expression of SLA, the exact relationships differ between ecological groupings. LDMC predicts leaf nitrogen content and soil fertility but, because LT primarily varies with light intensity, SLA increases in response to both increased shade and increased fertility.
Gradients of soil fertility are frequently also gradients of biomass accumulation with reduced irradiance lower in the canopy. Therefore, SLA, which includes both fertility and shade components, may often discriminate better between communities or treatments than LDMC. However, LDMC should always be the preferred trait for assessing gradients of soil fertility uncoupled from shade. Nevertheless, because leaves multitask, individual leaf traits do not necessarily exhibit exact functional equivalence between species. In consequence, rather than using a single stand-alone predictor, multivariate analyses using several leaf traits is recommended.
PMCID: PMC3197453  PMID: 21948627
Ellenberg numbers; functional traits; leaf density; leaf nitrogen; leaf size; leaf thickness; relative growth rate (RGR); shade tolerance; variation in trait expression
4.  Seasonal climate manipulations have only minor effects on litter decomposition rates and N dynamics but strong effects on litter P dynamics of sub-arctic bog species 
Oecologia  2012;170(3):809-819.
Litter decomposition and nutrient mineralization in high-latitude peatlands are constrained by low temperatures. So far, little is known about the effects of seasonal components of climate change (higher spring and summer temperatures, more snow which leads to higher winter soil temperatures) on these processes. In a 4-year field experiment, we manipulated these seasonal components in a sub-arctic bog and studied the effects on the decomposition and N and P dynamics of leaf litter of Calamagrostis lapponica, Betula nana, and Rubus chamaemorus, incubated both in a common ambient environment and in the treatment plots. Mass loss in the controls increased in the order Calamagrostis < Betula < Rubus. After 4 years, overall mass loss in the climate-treatment plots was 10 % higher compared to the ambient incubation environment. Litter chemistry showed within each incubation environment only a few and species-specific responses. Compared to the interspecific differences, they resulted in only moderate climate treatment effects on mass loss and these differed among seasons and species. Neither N nor P mineralization in the litter were affected by the incubation environment. Remarkably, for all species, no net N mineralization had occurred in any of the treatments during 4 years. Species differed in P-release patterns, and summer warming strongly stimulated P release for all species. Thus, moderate changes in summer temperatures and/or winter snow addition have limited effects on litter decomposition rates and N dynamics, but summer warming does stimulate litter P release. As a result, N-limitation of plant growth in this sub-arctic bog may be sustained or even further promoted.
PMCID: PMC3470819  PMID: 22526945
Climate warming; Immobilization; Nutrient limitation; Nutrient mineralization; Phosphorus release
5.  Stomatal vs. genome size in angiosperms: the somatic tail wagging the genomic dog? 
Annals of Botany  2010;105(4):573-584.
Background and Aims
Genome size is a function, and the product, of cell volume. As such it is contingent on ecological circumstance. The nature of ‘this ecological circumstance’ is, however, hotly debated. Here, we investigate for angiosperms whether stomatal size may be this ‘missing link’: the primary determinant of genome size. Stomata are crucial for photosynthesis and their size affects functional efficiency.
Stomatal and leaf characteristics were measured for 1442 species from Argentina, Iran, Spain and the UK and, using PCA, some emergent ecological and taxonomic patterns identified. Subsequently, an assessment of the relationship between genome-size values obtained from the Plant DNA C-values database and measurements of stomatal size was carried out.
Key Results
Stomatal size is an ecologically important attribute. It varies with life-history (woody species < herbaceous species < vernal geophytes) and contributes to ecologically and physiologically important axes of leaf specialization. Moreover, it is positively correlated with genome size across a wide range of major taxa.
Stomatal size predicts genome size within angiosperms. Correlation is not, however, proof of causality and here our interpretation is hampered by unexpected deficiencies in the scientific literature. Firstly, there are discrepancies between our own observations and established ideas about the ecological significance of stomatal size; very large stomata, theoretically facilitating photosynthesis in deep shade, were, in this study (and in other studies), primarily associated with vernal geophytes of unshaded habitats. Secondly, the lower size limit at which stomata can function efficiently, and the ecological circumstances under which these minute stomata might occur, have not been satisfactorally resolved. Thus, our hypothesis, that the optimization of stomatal size for functional efficiency is a major ecological determinant of genome size, remains unproven.
PMCID: PMC2850795  PMID: 20375204
Stomatal size; genome size; seed size; life history; photosynthesis; allometry; ecology; evolution; SLA; leaf structure; CAM; C4

Results 1-5 (5)