New Phytologist and the Earth System

Field: Environmental Science (Physical Sciences)

In recent weeks, world-wide media reports have highlighted the fact that atmospheric CO2 concentrations measured at the Mauna Loa Observatory reached 400 ppm (http://keelingcurve.ucsd.edu/), having risen from 280 ppm before the start of the Industrial Revolution. This news reminds us that in the coming years, CO2 levels will continue to rise, giving us an atmospheric CO2 concentration that has not been reached in millions of years (Pagani et al., 2009). As readers of New Phytologist well know, such increases in atmospheric CO2 can have profound impacts on plant growth and performance (Ayub et al., 2011; Jordan, 2011; Dijkstra et al., 2012; Zeppel et al., 2012; Battipaglia et al., 2013; Franks et al., 2013; Smith et al., 2013), plant–insect interactions (Robinson et al., 2012), community composition and ecosystem productivity (Antoninka et al., 2011; Bradford et al., 2012). Indeed, New Phytologist is a natural home for studies assessing how plants respond to increasing atmospheric CO2 (and other abiotic and biotic factors associated with global environmental change). More recently, New Phytologist has also emerged as an ideal home for papers assessing the role of vegetation in the Earth system. Four papers illustrate this. The first is that of Fisher et al. (2010), where they examined how representation of demographic processes (e.g. seed dispersal, seed mixing, sapling survival, competitive exclusion and plant mortality) in a second-generation Dynamic Global Vegetation Model (DGVM) influences predicted community structure and ecosystem responses to climate change. The second is a study by Galbraith et al. (2010), where the contribution of four environmental drivers (precipitation, temperature, humidity and CO2) to simulated future changes in Amazonian vegetation carbon were assessed. Third, Prentice et al. (2011) assessed the realism of DGVM-modeled changes in past vegetation with paleodata on forest distributions; a fourth paper discussed how concepts from community assembly theory and coexistence theory can help to improve DGVMs (Scheiter et al., 2013). Collectively, these New Phytologist papers provide important insights into global change and Earth system functioning. The earlier mentioned studies also illustrate the role of New Phytologist in bridging the gap between the fields of plant biology, biogeoscience and climate change prediction. Here, the role of New Phytologist as a non-profit trust (http://www.newphytologist.org/sections/index/1) is important, as the Trust has funded several Symposia and Workshops that focus on plant responses to global climate change, and the importance of plants in influencing future change in the Earth system (Atkin et al., 2010; Austin & Vitousek, 2012). This support will continue, with the upcoming 8th New Phytologist Workshop (NPW) (http://www.newphytologist.org/workshops/view/3) in July 2013 focusing on how to improve representation of leaf respiration in large-scale predictive climate–vegetation models). Similarly, the 9th NPW will explore how to improve representations of photosynthesis in Earth System Models (ESMs). Given that plant physiology responses to climate change drivers may represent the largest uncertainty in ESMs (Booth et al., 2012; Huntingford et al., 2013), both NPWs are timely opportunities for further dialogue in this important area of interdisciplinary research. Finally, New Phytologist will also soon publish a Virtual Special Issue that highlights the importance of root form and function for ecosystem models, and how knowledge of root processes are crucial for integrated assessments of climate change impacts on carbon, water, and nutrient cycles. The Environment Section in New Phytologist has always welcomed submissions that assess relationships among plant traits (Wright et al., 2006; Poorter et al., 2009; Hattenschwiler et al., 2011; Renton & Poorter, 2011). Here, relationships between photosynthesis, leaf nitrogen concentration and leaf mass–area relationships have been of particular interest (Field & Mooney, 1986; Evans, 1989; Reich et al., 1997; Wright et al., 2004). Inter-specific comparisons of leaf trait relationships have revealed very close links between mass-based rates of photosynthesis and related traits (e.g. mass-based leaf nitrogen concentration and leaf life-span) (Wright et al., 2004). By contrast, area-based rates of photosynthesis are often poorly correlated with their area-based counterparts (Field & Mooney, 1983; Wright et al., 2004). These findings led Wright et al. (2004) to hypothesize that such patterns represent a ‘leaf economic spectrum’ (LES). Since then, the concept of the LES has received considerable interest and support. Yet, debate continues about how one should interpret the contrasting strong mass-based relationships and their weaker, area-based counterparts. In the current issue of New Phytologist, Lloyd et al. (pp. 311–321) employ a range of statistical methods to revisit the LES; central to their argument is the suggestion that photosynthesis is an area-based trait and that analyses of photosynthesis–nutrient or photosynthesis–structure relationships should be done on a leaf area basis. In their response Letter, Westoby et al. (pp. 322–323) highlight the value of mass-based expressions for studies that focus on plant growth and economics of resource use. Further attention to this topic is also provided elsewhere (Osnas et al., 2013). Thus, the debate remains active. Given the pivotal nature of photosynthesis–nutrient–structure relationships for ESM predictions and our understanding of the evolution of leaf traits, this debate has considerable significance for readers of New Phytologist. Other papers in this issue that fall under the umbrella of the Environment Section include an assessment of the effects of experimental warming on terrestrial nitrogen pools and dynamics (Bai et al., pp. 441–451); application of carbon isotope labeling in comparisons of different functional groups in tropical ecosystems (Krepkowski et al., pp. 431–440); quantification of the impacts of insect infestation on water and carbon relations in two species of hemlock (Domec et al., pp. 452–463); controls over root respiration in forest ecosystems (Hopkins et al., pp. 339–351; Lynch et al., pp. 420–430); and the form of inorganic nitrogen used by mosses (Liu et al., pp. 407–419). All of these papers make use of novel experimental approaches to provide insights into the role of the environment in influencing plant function. Rich Norby has led the Environment Section since its inception in 2001. Since then, Rich has overseen huge increases in submissions to the Section, with the impact of environment-related New Phytologist papers on the scientific community growing markedly. These papers have contributed in no small way to the rising ISI Impact Factor of New Phytologist, which has risen from 2.53 in 2001 to 6.45 in 2012. Rich also serves as a Trustee of the New Phytologist Trust (an independent charity/non-profit-making organization, much like a scientific society, which is dedicated to the promotion of plant science). Rich has thus carried a heavy load; to lighten this load, he has recently decided to step down as the lead Environment Section Editor, while maintaining his role as a Trustee and Editor. To reflect the growing number of submissions to the Environment Section, particularly with respect to studies dealing with impacts of drought on plant function and mortality, New Phytologist is pleased to announce the appointment of Nate McDowell (Los Alamos National Laboratory, USA) to the Editorial Board. Nate is a card-carrying plant ecophysiologist with expertise in ecosystem ecology and isotope ecology. His research group focuses on quantifying mechanisms that control the balance between carbon uptake and water lost at the leaf, whole plant, and ecosystem scales. His work is informing our understanding of how plants (particularly forest species) respond to climate change/variability, as well as how disturbance regimes impact on ecosystem function. An example of the way his work combines empirical approaches with theory and modeling is his widely cited 2008 Tansley Review on drought-induced mortality (McDowell et al., 2008). Nate's interests complement those of the other Environment Section Editors – David Ackerly, Owen Atkin, Amy Austin, Andrea Polle and Rich Norby. Finally, as in the past, future success of New Phytologist requires the journal to maintain its focus on publishing high quality, original research in the plant sciences. Identifying emerging areas of science is central to this goal. Here, studies assessing the influence of vegetation over the Earth system provide an exciting area for future volumes of New Phytologist. We strongly encourage authors working in this area to submit their best work to us.