02633nas a2200253 4500008004100000245013900041210006900180300001500249490000800264520182600272653001002098653001502108653001202123653001502135653001202150653003102162653001002193653001502203100001802218700002302236700001902259700002002278856008102298 2014 eng d00aFire dynamics distinguish grasslands, shrublands, and woodlands as alternative attractors in the Central Great Plains of North America0 aFire dynamics distinguish grasslands shrublands and woodlands as a1374 -13850 v1023 a
Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1–2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1–2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency.
10abison10aEcosystems10aForests10aGrasslands10aGrazing10aLinear regression analysis10aTrees10aWatersheds1 aRatajczak, Z.1 aNippert, Jesse, B.1 aBriggs, J., M.1 aBlair, John, M. uhttps://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.1231102419nas a2200265 4500008004100000245011100041210006900152300001200221490000600233520162300239653001001862653000901872653002201881653001501903653001301918653001301931653002001944653002001964100002201984700002102006700001602027700001602043700001602059856007802075 2013 eng d00aEffects of sexual dimorphism and landscape composition on the trophic behavior of Greater Prairie-Chickens0 aEffects of sexual dimorphism and landscape composition on the tr a79986 -0 v83 aPartitioning of ecological niche is expected in lekking species that show marked sexual size dimorphism as a consequence of sex-specific ecological constraints. However, niche partitioning is uncertain in species with moderate sexual dimorphism. In addition, the ecological niche of a species may also be affected by landscape composition; particularly, agricultural fragmentation may greatly influence the trophic behavior of herbivores. We studied trophic niche variation in Greater Prairie-Chickens (Tympanuchus cupido), a grouse species that shows moderate sex-dimorphism. Greater Prairie-Chickens are native to tallgrass prairies of North America, although populations persist in less natural mosaics of cropland and native habitats. We used stable isotope analysis of carbon and nitrogen in blood, claws and feathers to assess seasonal differences in trophic niche breadth and individual specialization between male and female Greater Prairie-Chickens, and between birds living in continuous and fragmented landscapes. We found that females showed broader niches and higher individual specialization than males, especially in winter and autumn. However, differences between females and males were smaller in spring when birds converge at leks, suggesting that females and males may exhibit similar feeding behaviors during the lekking period. In addition, we found that birds living in native prairies showed greater annual trophic variability than conspecifics in agricultural mosaic landscapes. Native habitats may provide greater dietary diversity, resulting in greater diversity of feeding strategies.
10aBlood10adiet10aEcological niches10aEcosystems10aFeathers10ahabitats10aMating behavior10aStable isotopes1 aBlanco-Fontao, B.1 aSandercock, B.K.1 aObeso, J.R.1 aMcNew, L.B.1 aQuevedo, M. uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.007998602826nas a2200277 4500008004100000245010400041210006900145300001200214490000600226520201300232653001502245653001502260653001202275653001102287653002102298653001202319653001102331653002002342100002302362700002002385700001702405700001802422700001302440700001702453856007802470 2013 eng d00aEvidence of physiological decoupling from grassland ecosystem drivers by an encroaching woody shrub0 aEvidence of physiological decoupling from grassland ecosystem dr a81630 -0 v83 aShrub encroachment of grasslands is a transformative ecological process by which native woody species increase in cover and frequency and replace the herbaceous community. Mechanisms of encroachment are typically assessed using temporal data or experimental manipulations, with few large spatial assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra-annual variability in leaf δ13C in Cornus drummondii across a grassland landscape with varying fire frequency, presence of large grazers and topographic variability. This assessment of changes in individual shrub physiology is the largest spatial and temporal assessment recorded to date. Despite a doubling of annual rainfall (in 2008 versus 2011), leaf δ13C was statistically similar among and within years from 2008-11 (range of −28 to −27‰). A topography*grazing interaction was present, with higher leaf δ13C in locations that typically have more bare soil and higher sensible heat in the growing season (upland topographic positions and grazed grasslands). Leaf δ13C from slopes varied among grazing contrasts, with upland and slope leaf δ13C more similar in ungrazed locations, while slopes and lowlands were more similar in grazed locations. In 2011, canopy greenness (normalized difference vegetation index – NDVI) was assessed at the centroid of individual shrubs using high-resolution hyperspectral imagery. Canopy greenness was highest mid-summer, likely reflecting temporal periods when C assimilation rates were highest. Similar to patterns seen in leaf δ13C, NDVI was highest in locations that typically experience lowest sensible heat (lowlands and ungrazed). The ability of Cornus drummondii to decouple leaf physiological responses from climate variability and fire frequency is a likely contributor to the increase in cover and frequency of this shrub species in mesic grassland and may be generalizable to other grasslands undergoing woody encroachment.
10aEcosystems10aGrasslands10aGrazing10aLeaves10aPlant physiology10aSeasons10aShrubs10aWater resources1 aNippert, Jesse, B.1 aOcheltree, T.W.1 aOrozco, G.L.1 aRatajczak, Z.1 aLing, B.1 aSkibbe, A.M. uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.008163001884nas a2200193 4500008004100000245009100041210006900132260004100201300001000242490001400252520122500266653002401491653001501515653002901530653003301559653002701592100001701619856005401636 2008 eng d00aAltered rainfall due to climate change: Modeling the ecological effects on grasslands0 aAltered rainfall due to climate change Modeling the ecological e aStorrs,CTbUniversity of Connecticut a1 -630 vMS Thesis3 aThe acceleration of the hydrological cycle due to global climate change is predicted to cause more extreme precipitation, characterized by fewer but more intense storms. Such altered rainfall patterns will have significant impacts on water limited ecosystems such as grasslands. This project used a land surface model, the Community Land Model 3.0 coupled with a dynamic vegetation model, to examine how changing the size and frequency of rain events impacts plants, surface hydrology and surface energy budgets in the tallgrass prairie ecosystem. We applied a similar rainfall scheme as the Rainfall Manipulation Plots at Konza Prairie Biological Station in Kansas, which consisted of an altered rainfall treatment, with fewer but more intense events, and an ambient treatment, which replicated the natural pattern of rain. Both the model and field experiments show a reduction in grass productivity from the ambient to the altered treatment and a negative correlation between soil moisture variability and productivity. In addition, based on the modeling results, the altered rainfall treatment increases runoff, decreases evapotranspiration, and increases sensible heat flux at the expense of latent heat flux.
10aClimate variability10aEcosystems10aImpacts of global change10aLand/atmosphere interactions10astructure and dynamics1 aHoover, D.L. uhttp://adsabs.harvard.edu/abs/2008AGUFM.B21C0377H02231nas a2200349 4500008004100000245008200041210006900123300001300192490000700205520128800212653001901500653001201519653001501531653001801546653001501564100002001579700001401599700001701613700001801630700001201648700001901660700001601679700001601695700001501711700001401726700001801740700001701758700001501775700001401790700001301804856006401817 2008 eng d00aConsequences of more extreme precipitation regimes for terrestrial ecosystems0 aConsequences of more extreme precipitation regimes for terrestri a811 -8210 v583 amplification of the hydrological cycle as a consequence of global warming is forecast to lead to more extreme intra-annual precipitation regimes characterized by larger rainfall events and longer intervals between events. We present a conceptual framework, based on past investigations and ecological theory, for predicting the consequences of this underappreciated aspect of climate change. We consider a broad range of terrestrial ecosystems that vary in their overall water balance. More extreme rainfall regimes are expected to increase the duration and severity of soil water stress in mesic ecosystems as intervals between rainfall events increase. In contrast, xeric ecosystems may exhibit the opposite response to extreme events. Larger but less frequent rainfall events may result in proportional reductions in evaporative losses in xeric systems, and thus may lead to greater soil water availability. Hydric (wetland) ecosystems are predicted to experience reduced periods of anoxia in response to prolonged intervals between rainfall events. Understanding these contingent effects of ecosystem water balance is necessary for predicting how more extreme precipitation regimes will modify ecosystem processes and alter interactions with related global change drivers.
10aClimate change10aDrought10aEcosystems10aPrecipitation10asoil water1 aKnapp, Alan, K.1 aBeier, C.1 aBriske, D.D.1 aClassen, A.T.1 aLuo, Y.1 aReichstein, M.1 aSmith, M.D.1 aSmith, S.D.1 aBell, J.E.1 aFay, P.A.1 aHeisler, J.L.1 aLeavitt, S.W1 aSherry, R.1 aSmith, B.1 aWeng, E. uhttps://academic.oup.com/bioscience/article/58/9/811/25085301984nam a2200229 4500008004100000245006600041210006600107260003200173300001000205520127700215653001601492653001101508653001701519653001501536653001901551653001601570100001601586700002001602700001601622700002001638856009601658 2007 eng d00aPrinciples and Standards for Measuring Net Primary Production0 aPrinciples and Standards for Measuring Net Primary Production bOxford University Press, NY a268 -3 aStandardized approaches for the measurement of primary production — the rate of energy storage in the organic matter of plants — are essential to facilitate scientific comparisons and syntheses as well as policy and management on global climate change and the carbon cycle. This book provides an overview of the principles that should underlie every program of measurement of primary production in the Earth's major biomes. Each of seven biome-based chapters provides an overview of essential features of primary production processes in the biome and detailed descriptions of the procedures used to quantify primary production in grasslands, shrublands, forests, peatlands and tundra, salt marshes, marine pelagic, and freshwater ecosystems. Recent advances in the measurement of belowground production in terrestrial biomes are described. The book also provides detailed guidelines for information management based upon current experiences of the US Long-Term Ecological Research network. Advanced techniques are described for scaling up empirical measurements of primary production using remotely-sensed information. Finally, the principles and practices for quantifying uncertainty in primary production measurements are explored using examples from various biomes.10abelowground10abiomes10acarbon cycle10aEcosystems10aremote sensing10auncertainty1 aFahey, T.J.1 aKnapp, Alan, K.1 aFahey, T.J.1 aKnapp, Alan, K. uhttp://lter.konza.ksu.edu/content/principles-and-standards-measuring-net-primary-production