Functional diversification enabled grassy biomes to fill global climate space (original) (raw)
Related papers
The Origin of Grass-Dominated Ecosystems
Annals of the Missouri Botanical Garden, 1999
Approximately one-third of the Earth's vegetative cover comprises savannas. grasslands, and other grass-dominated ecosystems. Paleobotanical, paleofaunal, and stable carbon isotope records suggest five major phases in the origin of grass-dominated ecosystems: (1) the late Maastrichtian (or Paleocene) origin of Poaceae; (2) the opening of Paleocene and Eocene forested environments in the early to middle Tertiary; (3) an increase in the abundance of C3 grasses during the middle Tertiary; (4) the origin of C, grasses in the middle Miocene; and (5) the spread of C, grass-dominated ecosystems at the expense of C3 vegetation in the late Miocene. Grasses are known from all continents except Antarctica between the early Paleocene and middle Eocene. Herbivore morphology indicative of grazing, and therefore suggestive of grass-dominated ecosystems. appears in South America by the Eocene-Oligocene boundary, prior to the occurrence of grazing morphology elsewhere, and persists throughout the Cenozoic. Clear vertebrate and paleobotanical evidence of widespread grass-dominated ecosystems in northern continents does not occur until the early to middle Miocene. C4 grasses are present from approximately 1 5 Ma and undergo a dramatic expansion in the lower latitudes of North America, South America, East Africa, and Pakistan between 9 and 4 Ma. The expansion may have taken place in a shorter interval in some regions. C4 grasses are characteristic of seasonal. arid, and warm environments and are more tolerant of lower atmospheric CO, (< 400 ppmv) than C, plants. C4 grass distribution, therefore, is climatically controlled. The late Miocene spread of C, grasses possibly involved a decrease in atmospheric CO, and heralded the establishment of modern seasonality and rainfall patterns.
The evolution of grass-dominated ecosystems during the late Cenozoic
Palaeogeography, Palaeoclimatology, …, 2004
Grass-dominated ecosystems, including steppes, temperate grasslands, and tropical–subtropical savannas, play a central role in the modern world, occupying about 1/4 of the Earth's land surface (Shantz, 1954) and providing food and habitat for humans and many of the animals upon which humans have come to depend. Understanding the evolution of grass-dominated habitats and the creatures that inhabit them—including ourselves—is therefore crucial in providing future directions for conservation and management.
Diverse responses of phenology to global changes in a grassland ecosystem
Proceedings of The National Academy of Sciences, 2006
Shifting plant phenology (i.e., timing of flowering and other developmental events) in recent decades establishes that species and ecosystems are already responding to global environmental change. Earlier flowering and an extended period of active plant growth across much of the northern hemisphere have been interpreted as responses to warming. However, several kinds of environmental change have the potential to influence the phenology of flowering and primary production. Here, we report shifts in phenology of flowering and canopy greenness (Normalized Difference Vegetation Index) in response to four experimentally simulated global changes: warming, elevated CO 2, nitrogen (N) deposition, and increased precipitation. Consistent with previous observations, warming accelerated both flowering and greening of the canopy, but phenological responses to the other global change treatments were diverse. Elevated CO 2 and N addition delayed flowering in grasses, but slightly accelerated flowering in forbs. The opposing responses of these two important functional groups decreased their phenological complementarity and potentially increased competition for limiting soil resources. At the ecosystem level, timing of canopy greenness mirrored the flowering phenology of the grasses, which dominate primary production in this system. Elevated CO 2 delayed greening, whereas N addition dampened the acceleration of greening caused by warming. Increased precipitation had no consistent impacts on phenology. This diversity of phenological changes, between plant functional groups and in response to multiple environmental changes, helps explain the diversity in large-scale observations and indicates that changing temperature is only one of several factors reshaping the seasonality of ecosystem processes.
Ecology, 2015
Various environmental factors, including atmospheric CO 2 ( pCO 2 ), regional climate, and fire, have been invoked as primary drivers of long-term variation in C 4 grass abundance. Evaluating these hypotheses has been difficult because available paleorecords often lack information on past C 4 grass abundance or potential environmental drivers. We analyzed carbon isotope ratios (d 13 C) of individual grains of grass pollen in the sediments of two East African lakes to infer changes in the relative abundance of C 3 vs. C 4 grasses during the past 25 000 years. Results were compared with concurrent changes in pCO 2 , temperature, moisture balance, and fire activity. Our grass-pollen d 13 C analysis reveals a dynamic history of grass-dominated vegetation in equatorial East Africa: C 4 grasses have not consistently dominated lowland areas, and high-elevation grasses have not always been predominantly C 3. On millennial timescales, C 4 grass abundance does not correlate with charcoal influx at either site, suggesting that fire was not a major proximate control of the competitive balance between C 3 and C 4 grasses. Above the present-day treeline on Mt. Kenya, C 4 grass abundance declined from an average of ;90% during the glacial period to less than ;60% throughout the Holocene, coincident with increases in pCO 2 and temperature, and shifts in moisture balance. In the lowland savanna southeast of Mt. Kilimanjaro, C 4 grass abundance showed no such directional trend, but fluctuated markedly in association with variation in rainfall amount and seasonal-drought severity. These results underscore spatiotemporal variability in the relative influence of pCO 2 and climate on the interplay of C 3 and C 4 grasses and shed light on an emerging conceptual model regarding the expansion of C 4 -dominated grasslands in Earth's history. They also suggest that future changes in the C 3 /C 4 composition of grass-dominated ecosystems will likely exhibit striking spatiotemporal variability as a result of varying combinations of environmental controls.
Climatic Controls on C4 Grassland Distributions During the Neogene: A Model-Data Comparison
Frontiers in Ecology and Evolution
Fox et al. Neogene C 4 Grasslands: Model-Data Comparison comparisons, suggesting that regional to local ecological interactions, continent-specific plant evolutionary histories, and/or regional to local climatic conditions not represented in global scale OAGCMs may have been equally strong or stronger in driving the evolution of C 4 grasslands as global changes in the Earth system such as decreases in atmospheric pCO 2 and late Cenozoic global cooling and/or aridification.
Journal of Vegetation Science, 2008
AbstractQuestions: Is plant diversity in mesic grassland ecosystems vulnerable in the short-term to extreme climate change events? How rapidly can responses in vegetation composition occur in perennial grasslands? Are the expected compositional changes related to rare species losses or to shifts in the relative abundance of the dominants?Is plant diversity in mesic grassland ecosystems vulnerable in the short-term to extreme climate change events? How rapidly can responses in vegetation composition occur in perennial grasslands? Are the expected compositional changes related to rare species losses or to shifts in the relative abundance of the dominants?Location: Subalpine mesic grasslands on limestone in the Pyrenees.Subalpine mesic grasslands on limestone in the Pyrenees.Methods: Transplanting turves from the upland, with cold-temperate climate, to a lowland location, with continental Mediterranean climate.Transplanting turves from the upland, with cold-temperate climate, to a lowland location, with continental Mediterranean climate.Results: Transplanting led to decreased biodiversity and strong shifts in vegetation composition. Results from both permutation tests and traditional multivariate analysis suggested different trajectories of vegetation depending on the initial species pool. Vegetation showed a tendency to converge in composition in the lowland over time, independently of initial differences. Estimated changes in relative biomass of the five most abundant species between the upland and the lowland ranged from -89 to +96 %. The ensemble of all other species was reduced by 80%. The most dominant species in the upland, Festuca nigrescens, reduced its abundance in the lowland, shifting from having mainly positive to mainly negative associations with other species.Transplanting led to decreased biodiversity and strong shifts in vegetation composition. Results from both permutation tests and traditional multivariate analysis suggested different trajectories of vegetation depending on the initial species pool. Vegetation showed a tendency to converge in composition in the lowland over time, independently of initial differences. Estimated changes in relative biomass of the five most abundant species between the upland and the lowland ranged from -89 to +96 %. The ensemble of all other species was reduced by 80%. The most dominant species in the upland, Festuca nigrescens, reduced its abundance in the lowland, shifting from having mainly positive to mainly negative associations with other species.Conclusions: Mesic grassland ecosystems in the Pyrenees showed strong shifts in plant diversity and composition after a short period of warming and drought, as a consequence of acute vulnerability of some dominant grasses, losses of rare species, and aggregate and trigger effects of originally uncommon forb species.Mesic grassland ecosystems in the Pyrenees showed strong shifts in plant diversity and composition after a short period of warming and drought, as a consequence of acute vulnerability of some dominant grasses, losses of rare species, and aggregate and trigger effects of originally uncommon forb species.
Climate, phylogeny and the ecological distribution of C4 grasses
Ecology Letters, 2008
ÔC4 photosynthesisÕ 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.
GrassPlot - a database of multi-scale plant diversity in Palaearctic grasslands
2018
GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains dat...