Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.Green leaves are fundamental for the functioning of terrestrial ecosystems. Their pigments are the predominant signal seen from space. Nitrogen uptake and carbon assimilation by plants and the decomposability of leaves drive biogeochemical cycles. Animals, fungi and other heterotrophs in ecosystems are fuelled by photosynthate, and their habitats are structured by the stems on which leaves are deployed. Plants invest photosynthate and mineral nutrients in the construction of leaves, which in turn return a revenue stream of photosynthate over their lifetimes. The photosynthate is used to acquire mineral nutrients, to support metabolism and to re-invest in leaves, their supporting stems and other plant parts.There are more than 250,000 vascular plant species, all engaging in the same processes of investment and reinvestment of carbon and mineral nutrients, and all making enough surplus to ensure continuity to future generations. These processes of investment and re-investment are inherently economic in nature [1][2][3] . Understanding how these processes vary between species, plant functional types and the vegetation of different biomes is a major goal for plant ecology and crucial for modelling how nutrient fluxes and vegetation boundaries will shift with land-use and climate change. Data set and parametersWe formed a global plant trait network (Glopnet) to quantify leaf economics across the world's plant species. The Glopnet data set spans 2,548 species from 219 families at 175 sites (approximately 1% of the extant vascular plant species). The coverage of traits, species and sites is at least tenfold greater than previous data compilations [4][5][6][7][8][9][10][11] , extends to all vegetated continents, and represents a wide range of vegetation types, from arctic tundra to tropical rainforest, from hot to cold deserts, from boreal forest to grasslands. Site elevation ranges from below sea level (Death Valley, USA) to 4,800 m. Mean annual temperature (MAT) ranges from 216.5 8C to 27.5 8C; mean annual rainfall (MAR) ranges from 133 to 5,300 mm per year. This cove...

The natural geographical occurrence, carbon assimilation, and structural and biochemical diversity of species with C photosynthesis in the vegetation of Mongolia was studied. The Mongolian flora was screened for C plants by using C/C isotope fractionation, determining the early products of CO fixation, microscopy of leaf mesophyll cell anatomy, and from reported literature data. Eighty C species were found among eight families: Amaranthaceae, Chenopodiaceae, Euphorbiaceae, Molluginaceae, Poaceae, Polygonaceae, Portulacaceae and Zygophyllaceae. Most of the C4 species were in three families: Chenopodiceae (41 species), Poaceae (25 species) and Polygonaceae, genus Calligonum (6 species). Some new C species in Chenopodiaceae, Poaceae and Polygonaceae were detected. C Chenopodiaceae species make up 45% of the total chenopods and are very important ecologically in saline areas and in cold arid deserts. C grasses make up about 10% of the total Poaceae species and these species naturally concentrate in steppe zones. Naturalized grasses with Kranz anatomy,of genera such as Setaria, Echinochloa, Eragrostis, Panicum and Chloris, were found in almost all the botanical-geographical regions of Mongolia, where they commonly occur in annually disturbed areas and desert oases. We analyzed the relationships between the occurrence of C plants in 16 natural botanical-geographical regions of Mongolia and their major climatic influences. The proportion of C species increases with decreasing geographical latitude and along the north-to-south temperature gradient; however grasses and chenopods differ in their responses to climate. The abundance of Chenopodiaceae species was closely correlated with aridity, but the distribution of the C grasses was more dependent on temperature. Also, we found a unique distribution of different C Chenopodiaceae structural and biochemical subtypes along the aridity gradient. NADP-malic enzyme (NADP-ME) tree-like species with a salsoloid type of Kranz anatomy, such as Haloxylon ammodendron and Iljinia regelii, plus shrubby Salsola and Anabasis species, were the plants most resistant to ecological stress and conditions in highly arid Gobian deserts with less than 100 mm of annual precipitation. Most of the annual C chenopod species were halophytes, succulent, and occurred in saline and arid environments in steppe and desert regions. The relative abundance of C succulent chenopod species also increased along the aridity gradient. Native C grasses were mainly annual and perennial species from the Cynodonteae tribe with NAD-ME and PEP-carboxykinase (PEP-CK) photosynthetic types. They occurred across much of Mongolia, but were most common in steppe zones where they are often dominant in grazing ecosystems.

This study examines interrelationships between eight leaf attributes (specific leaf mass, area, dry mass, lamina thickness, mesophyll cell number per cm#, mesophyll cell volume, chloroplast volume, and number of chloroplasts per mesophyll cell) in field-grown plants of 94 species from the Eastern Pamir Mountains, at elevations between 3800 and 4750 m. Unlike most other mountain areas, the Eastern Pamirs, Karakorum system, Tadjikistan provide localities where low temperatures and radiation combine with moisture stress at high altitudes. For all the attributes measured, significant differences were found between plants with different mesophyll types. Leaves with dorsiventral palisade structure (dorsal palisade, ventral spongy mesophyll cells) had thicker leaves with larger but fewer mesophyll cells, containing more and larger chloroplasts. These differences in mesophyll type are reflected in differences in the total surface of mesophyll cells per unit leaf area (A mes \A) or volume (A mes \V ). Plants with isopalisade leaf structure (palisade cells under both dorsal and ventral surfaces) are more commonly xerophytes and their increased values of A mes \A and A mes \V decrease CO # mesophyll resistance, which is an important adaptation to drought. Path analysis shows the critical importance of mesophyll cell volume in leading to the covariance between the different leaf attributes and hence to specific leaf mass (SLM), even though mesophyll cell volume is not itself strongly correlated with SLM. This is because mesophyll cell volume increases SLM through its effects on leaf thickness and chloroplast number per cell, but decreases SLM through its negative effect on mesophyll cell density.

A survey of C4 plants in Europe was performed with 216 species based on information in the literature and new studies. C4 species were found in 10 families: the eudicots Amaranthaceae, Chenopodiaceae, Euphorbiaceae, Molluginaceae, Nyctaginaceae, Polygonaceae, Portulacaceae and Zygophyllaceae and the monocots Cyperaceae and Poaceae. The majority of the C4 species belong to four families, Amaranthaceae (23), Chenopodiaceae (65), Cyperaceae (27) and Poaceae (88). In central and southern Europe, the abundance of native C4 plants varied between 44 and 88% of total C4 plants occurring, the rest being invasive C4 species. The occurrence of total C4 species, C4 monocots and C4 Chenopodiaceae was assessed for five major phyto-geographical regions of Europe (north-west, north-east, central, south-west, and south-east). The abundance of C4 plants of total C4 dicots, C4 Chenopodiaceae, total C4 monocots, C4 Poaceae and C4 Cyperaceae was related to the climatic variables of annual mean daily temperature, annual precipitation and DeMartonne's aridity index. The abundance of total C4 plants decreases with increasing temperature and expression of aridity (decreasing aridity index) and is not correlated with precipitation. The abundance of total C4 dicots and C4 Chenopodiaceae is correlated with precipitation and aridity but not temperature, whereas the abundance of total C4 monocots, C4 Poaceae and C4 Cyperaceae is correlated with temperature and aridity but not precipitation.

Haloxylon aphyllum and H. persicum of Chenopodiaceae are dominant plants in the continental deserts of the Asian Irano-Turanian region. The photosynthetic organs, assimilating shoots and leaf-like cotyledons of these two species were studied to characterize their photosynthetic types. 13 C/ 12 C isotope ratios, the cellular anatomy of assimilating organs, primary photosynthetic products, and activities of carbon metabolism enzymes, RUBP carboxylase, PEP carboxylase, malic enzymes, and aspartate aminotransferase, indicate different pathways of CO 2 fixation in the photosynthetic organs. Assimilating shoots had attributes of the C 4 photosynthesis entirely, while cotyledons lack Kranz-anatomy and incorporated CO 2 via C 3 photosynthesis. Cotyledons and seeds had lower S U C values compared to shoots, consistent with the contribution of C 3-like CO 2 assimilation. Two pathways of carbon donation to the C 3 cycle via decarboxylation of C 4 acids in bundle sheath cells are suggested to occur in shoots of Haloxylon. The primary photosynthetic product malate can be utilized through NADP +-malic enzyme which occurs in high activity. NAD +-malic enzyme may contribute to C 4 photosynthesis (some aspartate is formed as an initial product, the bundle sheath chloroplasts have some grana, and NAD +-malic enzyme is found in bundle sheath cells of shoots, all criteria for NAD +-malic enzyme type photosynthesis). We propose that organ diversity of CO 2 fixation pathway in Haloxylon species is an important factor for their growth, survival and reproduction in continental climate deserts.