Distribution Of C4 Grasses Research Articles

Drought susceptibility of southern African C4 grasses: Phylogenetically and photosynthetically determined?

Abstract Factors that determine C4 grass distributions have been well documented, with evidence in the literature for C4 photosynthetic subtypes displaying varying levels of drought susceptibility. However, the interactions between C4 photosynthetic subtype and phylogeny add complexity and are relatively under studied. We use species distribution modelling to determine the influence of rainfall on distribution patterns of representative C4 grass families and subtypes. Select C4 grass species, representing different photosynthetic subtypes (NADP‐Me and NAD‐Me) and lineages (Panicoideae and Aristidoideae), were subjected to a progressive 58‐day drought period and recovery phase, to explore drought responses through leaf water relations, gas exchange and chlorophyll fluorescence. We show Panicoideae NADP‐Me species to be more susceptible to drought than both Panicoideae NAD‐Me and Aristidoideae NADP‐Me species due to apparent greater metabolic impairment. The differences between groups were related to how rapidly photosynthesis declines with exposure to drought and the rate of recovery postdrought, rather than the maximum extent of photosynthetic decline. The mechanisms for the relative maintenance of plant water status differed between the Panicoideae NAD‐Me species, which utilized greater stomatal control, and the Aristidoideae NADP‐Me species, which maintained water uptake through osmotic adjustment. Synthesis. We show here that drought susceptibility differs both phylogenetically and according to photosynthetic subtype, but that the role of phylogeny may outweigh physiological control. This research adds novel insight into the physiological differences behind observed rainfall‐related differences in C4 grass distribution patterns. Read the free Plain Language Summary for this article on the Journal blog.

Divergent climate impacts on C3 versus C4 grasses imply widespread 21st century shifts in grassland functional composition

AbstractAimGrasslands cover a third of Earth's landmass and provide critical ecosystem services. Anticipating how perennial C3 (cool‐season) and C4 (warm‐season) grasses respond to climate change will be key to predicting future composition and functioning of grasslands. Here, we evaluate environmental drivers of C3 and C4 perennial distributions and assess how C3 and C4 grass distributions shift in response to future climate change.LocationWestern United States.MethodsWe developed integrated species distribution models to identify climate and soil drivers of relative abundance of C3 and C4 perennial grasses. We then created projections of species abundances under future climate and evaluated when and where projected shifts in relative abundance were robust across climate models.ResultsHistorically, C3 grasses occupied areas with lower temperature and more variable precipitation regimes, while C4 grasses occupied areas of higher temperature, greater temperature variability and greater warm‐season precipitation. C4 species also occupied narrower soil texture niches. In response to future climate change, C3 grass abundance declined across 74% of areas, while C4 abundance increased across 66% of areas. C3 grasses expanded in mid‐ to higher‐latitude areas with increasing temperature and decreasing seasonality of precipitation. In contrast, C4 grasses increased in higher‐latitude regions, but declined in lower‐latitude, dryer regions. Results were surprisingly robust across climate scenarios, suggesting high confidence in the direction of these future changes.Main ConclusionsFindings imply C3 and C4 perennial grasses will have highly divergent responses to climate change that may result in grassland functional compositional changes. Increasing temperatures and precipitation variability may favour some C4 grasses, but C4 habitat expansion may be constrained by soil conditions in western USA. Results provide actionable insights for anticipating the impacts of climate change on grass‐dominated and co‐dominated ecosystems and improving large‐scale conservation and restoration efforts.

Traits explain sorting of C4 grasses along a global precipitation gradient.

Species distributions are closely associated with moisture availability, but the underlying mechanisms remain unresolved. Drought relations are especially important for plants such as C4 grasses that dominate seasonally dry ecosystems. Here, we test the hypothesis that C4 grass species sampled across global precipitation gradients show variation in survival under drought that can be explained by their traits.Our experiment subjected 18 C4 grass species to a lethal drought under controlled environmental conditions. The number of days until death was measured, along with root traits, senescence, and aspects of hydraulic function.We identified two strategies: Drought‐avoiding species that stayed green as the water potential declined and drought‐tolerating species that senesced more quickly but could extend survival via drought‐tolerant meristems.Plants that stay‐green for longer occupied drier habitats and had the longest survival under drought, facilitated by narrow root diameter and isohydric stomatal behavior. Plants that senesced quickly had thicker roots, an anisohydric strategy, and occupied wetter habitats.Global distributions of C4 grasses can be predicted by variation in rates of senescence, meristem survival, root traits, and stomatal strategy, showing the value of these traits for understanding plant distributions in relation to climate.

Climate, CO2, and the history of North American grasses since the Last Glacial Maximum.

The spread of C4 grasses in the late Neogene is one of the most important ecological transitions of the Cenozoic, but the primary driver of this global expansion is widely debated. We use the stable carbon isotopic composition (δ(13)C) of bison and mammoth tissues as a proxy for the relative abundance of C3 and C4 vegetation in their grazing habitat to determine climatic and atmospheric CO2 controls on C4 grass distributions from the Last Glacial Maximum (LGM) to the present. We predict the spatial variability of grass δ(13)C in North America using a mean of three different methods of classification and regression tree (CART) machine learning techniques and nine climatic variables. We show that growing season precipitation and temperature are the strongest predictors of all single climate variables. We apply this CART analysis to high-resolution gridded climate data and Coupled Model Intercomparison Project (CMIP5) mean paleoclimate model outputs to produce predictive isotope landscape models ("isoscapes") for the current, mid-Holocene, and LGM average δ(13)C of grass-dominated areas across North America. From the LGM to the present, C4 grass abundances substantially increased in the Great Plains despite concurrent increases in atmospheric CO2. These results suggest that changes in growing season precipitation rather than atmospheric CO2 were critically important in the Neogene expansion of C4 grasses.

Biogeographically distinct controls on C3 and C4 grass distributions: merging community and physiological ecology

AbstractAimC4 photosynthesis is an adaptation that maintains efficient carbon assimilation in high‐light, high‐temperature conditions. Due to the importance of C4 grasses for carbon and surface energy fluxes, numerous models have been proposed to describe their spatial distribution and forecast their responses to climate change. These models often rely on broad climatic predictors (e.g. temperature and precipitation) but fail to integrate other ecologically relevant factors like disturbance and competition, which may modify realized C3/C4 grass distributions. Here, we present a combined evaluation of the contribution of ecological factors and climatic predictors to realized C3/C4 grass distributions. We consider multiple biogeographic regions of North America using a multisource database of over 40,000 vegetation plots.LocationThe conterminous United States of America (USA).MethodsWe identified a comprehensive pool of climatic models in the literature and used information theoretic criteria to select a primary climatic predictor of C3 and C4 grass distributions. Subsequently, the best model was combined with ecological predictors (e.g. fire, tree cover) using a multiple regression framework and tested within eight regions.ResultsSurprisingly, grass‐dominated communities across the USA exist largely in C3‐ or C4‐dominated states. Transitions between C3/C4 dominance were best explained by models that integrated temperature and precipitation with ecological factors that varied according to region. For some regions, like Eastern Temperate Forests, local ecological factors were comparable in strength to broad‐scale climatic predictors of C3/C4 abundance.Main conclusionLocal ecological factors modify C3/C4 grass responses to broad‐scale climatic drivers in ways that manifest at regional scales. In Eastern Temperate Forests, for example, C4 grass abundances are maintained below climatic expectations where tree cover creates light limitation but above expectations where frequent fires reduce tree cover. Thus, local ecological factors, which vary among biogeographic regions, contribute to large‐scale climate disequilibrium.

Neotropical C3/C4 grass distributions – present, past and future

AbstractChanges in C4 grass distribution and abundance are frequently observed in Quaternary, Holocene and future environmental‐change scenarios. However, the factors driving these dynamics are not fully understood, and conflicting theories have been reported. In this paper, we present a very large dataset of modern altitudinal distribution profiles of C3 and C4 grasses covering the entire Neotropical Andes, which was compared with actual climate data. The results of multivariate analysis demonstrate that, in the Neotropical Andes, mean annual temperature is the main factor governing the modern altitudinal distribution of C3 and C4 grass species. The C3 and C4 grass distributions were compared with simulations based on the Lund‐Potsdam‐Jena dynamic global vegetation model (LPJ‐DGVM), which allowed the present grass distribution to be estimated. Finally, the DGVM was employed to simulate past and future scenarios, using the IPCC's climate projections for 2100 and PMIP2 models for the Holocene Optimum (HO, 6000 years bp) and the Last Glacial Maximum (LGM, 21 000 years bp). The results were found to be significantly different from those obtained using a simple photosynthetic model. According to LPJ forced with the PMIP2 models for the LGM, during the LGM, the C4 grasses would not have reached higher altitudes than found in the present day.

Climate, phylogeny and the ecological distribution of C4 grasses

'C4 photosynthesis' refers to a suite of traits that increase photosynthesis in high light and high temperature environments. Most C4 plants are grasses, which dominate tropical and subtropical grasslands and savannas but are conspicuously absent from cold growing season climates. Physiological attributes of C4 photosynthesis have been invoked to explain C4 grass biogeography; however, the pathway evolved exclusively in grass lineages of tropical origin, suggesting that the prevalence of C4 grasses in warm climates could be due to other traits inherited from their non-C4 ancestors. Here we investigate the relative influences of phylogeny and photosynthetic pathway in determining the ecological distributions of C4 grasses in Hawaii. We find that the restriction of C4 grasses to warmer areas is due largely to their evolutionary history as members of a warm-climate grass clade, but that the pathway does appear to confer a competitive advantage to grasses in more arid environments.

Stable carbon isotope analyses show dominance of C3 grasses in the feed selected by small herbivores at the alpine meadow at the Tibetan Plateau

Muscle samples were collected from small herbivorous mammals (Ochotona curzoniae, Microtus oecnomus, Myospalax fontanierii and Lepus oiostolus) at the alpine meadow ecosystem at the Tibetan Plateau in order to address variability in stable carbon isotope composition. Stable carbon isotope values of muscles remain steady and show no significant variations (-25.72 to -27.04 parts per thousand) among the four small mammal species. Based on the mass balance theory of stable isotopes, it is proposed that small herbivorous mammals mainly (or totally) rely on C3 grasses as food supply, and there is few or no distribution of C4 grasses at the ecosystem. The results reflect our previous study on the isotope patterns of plant species. Thus, stable carbon isotope analysis of muscles provides a method to address dietary selection and dietary variability in herbivores. In addition, stable carbon isotopic analyses can be used to address changes in vegetation distributions in ecosystem and paleovegetaion and paleoclimate.

Effects of climate and atmospheric CO2 partial pressure on the global distribution of C4 grasses: present, past, and future.

C4 photosynthetic physiologies exhibit fundamentally different responses to temperature and atmospheric CO2 partial pressures (pCO2) compared to the evolutionarily more primitive C3 type. All else being equal, C4 plants tend to be favored over C3 plants in warm humid climates and, conversely, C3 plants tend to be favored over C4 plants in cool climates. Empirical observations supported by a photosynthesis model predict the existence of a climatological crossover temperature above which C4 species have a carbon gain advantage and below which C3 species are favored. Model calculations and analysis of current plant distribution suggest that this pCO2-dependent crossover temperature is approximated by a mean temperature of 22°C for the warmest month at the current pCO2 (35 Pa). In addition to favorable temperatures, C4 plants require sufficient precipitation during the warm growing season. C4 plants which are predominantly graminoids of short stature can be competitively excluded by trees (nearly all C3 plants) - regardless of the photosynthetic superiority of the C4 pathway - in regions otherwise favorable for C4. To construct global maps of the distribution of C4 grasses for current, past and future climate scenarios, we make use of climatological data sets which provide estimates of the mean monthly temperature to classify the globe into areas which should favor C4 photosynthesis during at least 1 month of the year. This area is further screened by excluding areas where precipitation is <25 mm per month during the warm season and by selecting areas classified as grasslands (i.e., excluding areas dominated by woody vegetation) according to a global vegetation map. Using this approach, grasslands of the world are designated as C3, C4, and mixed under current climate and pCO2. Published floristic studies were used to test the accuracy of these predictions in many regions of the world, and agreement with observations was generally good. We then make use of this protocol to examine changes in the global abundance of C4 grasses in the past and the future using plausible estimates for the climates and pCO2. When pCO2 is lowered to pre-industrial levels, C4 grasses expanded their range into large areas now classified as C3 grasslands, especially in North America and Eurasia. During the last glacial maximum (∼18 ka BP) when the climate was cooler and pCO2 was about 20 Pa, our analysis predicts substantial expansion of C4 vegetation - particularly in Asia, despite cooler temperatures. Continued use of fossil fuels is expected to result in double the current pCO2 by sometime in the next century, with some associated climate warming. Our analysis predicts a substantial reduction in the area of C4 grasses under these conditions. These reductions from the past and into the future are based on greater stimulation of C3 photosynthetic efficiency by higher pCO2 than inhibition by higher temperatures. The predictions are testable through large-scale controlled growth studies and analysis of stable isotopes and other data from regions where large changes are predicted to have occurred.

Effects of climate warming on the distribution of C4 grasses in New Zealand

Data from pasture and roadside surveys and from an appeal to the public were used to assess whether recent climate warming has increased the spread of C4 grasses. Because of differences in date of introduction, saturation of existing range, ability to spread by seed, frost tolerance, and soil and moisture requirements, each species studied had a different potential increase in response to higher temperatures. Also spread could be exhibited as greater abundance within existing range as well as increase in geographical range. The strongest evidence that could be construed as an effect of climate warming was an increase of about 1.5" latitude in the area of 40% pasture occurrence of paspalum in the last 10-12 years. In the same period both carpet grass and knot-root bristle grass also greatly increased their impact. Most of the species studied (including the annual summer grass) underwent an explosive increase in the last 2-3 years after several particularly mild winters and warm summers. C4 species will probably be an increasing feature of pastures and lawns in future, and this should be accommodated by appropriate management and the introduction of improved pasture and amenity cultivars of this type. Keywords C4 grasses, climate change, paspalum, pasture survey

The distribution of C3 and C4 grasses in Australia in relation to climate.

All but four of 833 native and 292 naturalised Australian grasses (Poaceae) have been assigned as having the C4 or C4 photosynthetic pathway. In conjunction with comprehensive species composition data for 75 geographic subdivisions Australiawide, this has permitted the construction of distribution maps for C3 and C4 grasses. C3 and C4 grass distributions have been considered (i) independently, using subdivisional native species numbers; and (ii) relatively, using 'subdivisional % C4'. C3 species are most numerous in the Southern Tablelands (New South Wales), the QZ subdivision (Victoria), and Tasmania; C4 species in the northern Northern Territory and northern Queensland, including the Cook subdivision where 54% of Australia's native C4 grasses can be found. C3 species predominate only in south-west Western Australia, parts of southern South Australia, the Tablelands, central and south coast, and south western slopes of New South Wales, Victoria and Tasmania. C4 species predominate over 80-85% of the continental area. For 16 temperature and rainfall variables, subdivisional area-weighted means were calculated, and correlation analyses performed. C3 species number correlates most highly with January average maximum temperature (-ve) and spring rainfall (+ve); C4 species number with October average minimum temperature (+ve) and February median rainfall (+ve); '%C4' with January average minimum temperature (+ve). Predictive multiple linear regression equations were generated using climatic variables. In general, C4 grass species, like C3 species, increase in number with increasing rainfall, in their preferred temperature regime. C4 species are most numerous where the summer is hot and wet; C3 species where the spring is cool and wet. C4 species numbers decline with decreasing temperature and/or decreasing summer rainfall; C3 species numbers decline with increasing temperature and/or decreasing spring rainfall. Results are also considered in relation to the taxonomic and physiological heterogeneity of grasses and to Australia's geobotanic history.

Ecological Aspects of the Distribution of C 4 Grasses in Selected Habitats of Costa Rica

A distributional study of 65 grass species in seven habitats of Costa Rica was done to determine the differential distribution of C3 and C4 grasses and their adaptations to climatic conditions of rainfall, temperature, and sunlight. The highest proportion of C4 grasses were found in lowland areas with prevailing conditions of high temperatures, high insolation, and water stress, whereas the majority of C3 species were found in high attitude environments with conditions of lower temperatures, lower atmospheric 02 concentration, and no water stress. C4 PLANTS HAVE BEEN SHOWN to differ significantly from C3 plants in their physiology, anatomy, ultrastructure, and environmental requirements (Black 1971; Black, Chen, and Brown 1969; Laetsch 1974; Purohit and Tregunna 1974; Smith and Epstein 1971). Limiting climatic factors and ecological adaptations also differ between these two photosynthetic types (Black 1971, Cooper and Tainton 1968, Downes and Hesketh 1968, McWilliams and Mison 1974, Purohit and Tregunna 1974). C4 plants are generally characterized by a low atmospheric CO2 compensation point, low to negligible rates of photorespiration, a high optimum temperature range, a well-developed bundle-sheath containing chloroplasts, and a high light-saturation point; whereas C,3 plants have a higher CO2 compensation point, high rates of photorespiration, an optimum temperature range of 10-25?C, a poorly developed bundle-sheath generally without chloroplasts, and a light saturation point much lower than C4 plants (Black 1971; Black, Chen, and Brown 1969; Bidwell 1974; Cooper and Tainton 1968). Photosynthesis in C4 plants is unaffected by high or low atmospheric 02 concentrations whereas photosynthesis of C3 plants is inhibited at high 02 concentrations and enhanced at low 02 concentrations (Downes and Hesketh 1968). C4 plants have a higher C02 fixed/ water-use ratio and are therefore better adapted to arid environments (Black 1971, Laetsch 1974, Downes 1969). Thus, C4 plants have a competitive advantage over C3 plants in areas of high light intensity, high temperatures, high atmospheric 02 concentrations, and low CO2 concentrations (Bjorkman 1976, Cooper and Tainton 1968, Downes and Hesketh 1968), and generally experience a selective disadvantage in cool, moist environments where low atmospheric 02 concentrations and high C02 concentrations enhance photosynthesis of C3 plants (Downes and Hesketh 1968, Teeri and Stowe 1976). Not all C4 plants have a high optimum-temperature range as evidenced by the C4 species Atriplex sabulosa, the photosynthesis of which is completely inhibited, as occurs with most C.3 species, at temperatures of 44-45?C. These temperatures are considered optimal for most CG species (Bjorkman 1976). The objective of this study was to gather field data relating the differential occurrence and distribution of C4 and C3 grasses in selected habitats of Costa Rica to certain environmental and climatic conditions, taking into account the physiological and anatomical differences inherent in the two pathways. A similar study has been done with grass species in North America (Teeri and Stowe 1976) to determine the relative importance of several climatic variables in the distribution and occurrence of C4 species. In this way, both the ecological distribution of C4 grass species and possible evolutionary selective pressures can be studied from environmental and climatic

Implications of quantum yield differences on the distributions of C3 and C4 grasses.

The implications of a reduced quantum yield (initial slope of the photosynthetic light response curve) in C4 plants and temperature dependence of quantum yield in C3 plants on total canopy primary production were investigated using computer simulations. Since reduced quantum yield represents the only known disadvantage of the C4 photosynthetic pathway, simulations were conducted with grass canopies (high LAI and hence photosynthesis in most leaves will be light-limited) to see if quantum yield is a significant factor in limiting the primary production and thus distributions of C4 grasses. Simulations were performed for three biogeographical or environmental conditions: the Great Plains region of North America, the Sonoran Desert of North America, and shade habitats. For all three cases, the simulations predicted either spatial or temporal gradients in the abundances of C4 grasses identical to the abundance patterns of C4 grasses observed in the field. It is thus concluded that while the C4 photosynthetic mechanism may be highly advantageous in specific environments, it may be disadvantageous in others.

Climatic patterns and the distribution of C4 grasses in North America.

A stepwise multiple regression analysis was used in an attempt to correlate statistically the geographic patterns in the abundance of C4 grasses with patterns in climatic variables. The percent of grasses having the C4 pathway was computed for the total grass flora in twenty-seven widely spaced regions of North America. From long-term climatic records seasonal and annual values for solar irradiance, water supply, heat availability, and combinations of these variables were assigned to each of the twentyseven regions. The results of the analysis suggest that high minimum temperatures during the growing season have the strongest correlation with the relative abundance of C4 grass species in a regional flora. It appears that the deleterious effects of low temperatures during growth negate the advantages of possessing the C4 pathway in cooler habitats.

A Reanalysis of Vuilleumier's Data

Previous articleNext article No AccessLetters to the EditorsA Reanalysis of Vuilleumier's DataDavid Mauriello and Joann P. RoskoskiDavid Mauriello Search for more articles by this author and Joann P. Roskoski Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 108, Number 963Sep. - Oct., 1974 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/282950 Views: 2Total views on this site Citations: 11Citations are reported from Crossref Copyright 1974 The University of ChicagoPDF download Crossref reports the following articles citing this article:Ronald H. Karlson, Howard V. Cornell SCALE-DEPENDENT VARIATION IN LOCAL VS. REGIONAL EFFECTS ON CORAL SPECIES RICHNESS, Ecological Monographs 68, no.22 (May 1998): 259–274.https://doi.org/10.1890/0012-9615(1998)068[0259:SDVILV]2.0.CO;2H. J. B. Birks Statistical approaches to interpreting diversity patterns in the Norwegian mountain flora, Ecography 19, no.33 (Jan 1996): 332–340.https://doi.org/10.1111/j.1600-0587.1996.tb01262.x Thomas W. Schoener On Testing the MacArthur-Wilson Model with Data on Rates, The American Naturalist 131, no.66 (Oct 2015): 847–864.https://doi.org/10.1086/284826W Chapco, M J Bidochka Genetic variation in prairie populations of Melanoplus sanguinipes, the migratory grasshopper, Heredity 56, no.33 (Jun 1986): 397–408.https://doi.org/10.1038/hdy.1986.62P. Opdam, G. Rijsdijk, F. Hustings Bird communities in small woods in an agricultural landscape: Effects of area and isolation, Biological Conservation 34, no.44 (Jan 1985): 333–352.https://doi.org/10.1016/0006-3207(85)90039-4François Vuilleumier, Daniel Simberloff Ecology versus History as Determinants of Patchy and Insular Distributions in High Andean Birds, (Jan 1980): 235–379.https://doi.org/10.1007/978-1-4615-6959-6_5 Lawrence G. Stowe , and James A. Teeri The Geographic Distribution of C4 Species of the Dicotyledonae in Relation to Climate, The American Naturalist 112, no.985985 (Oct 2015): 609–623.https://doi.org/10.1086/283301J. A. Teeri, L. G. Stowe Climatic patterns and the distribution of C4 grasses in North America, Oecologia 23, no.11 (Mar 1976): 1–12.https://doi.org/10.1007/BF00351210A. L. Sullivan, M. L. Shaffer Biogeography of the Megazoo: Biogeographic studies suggest organizing principles for a future system of wild lands, Science 189, no.41964196 (Jul 1975): 13–17.https://doi.org/10.1126/science.189.4196.13Beryl B. Simpson Pleistocene changes in the flora of the high tropical Andes, Paleobiology 1, no.33 (May 2016): 273–294.https://doi.org/10.1017/S0094837300002530 Edwin H. Bryant An Addendum on the Statistical Relationship between Enzyme Polymorphisms and Environmental Variability, The American Naturalist 108, no.963963 (Oct 2015): 698–701.https://doi.org/10.1086/282946