The biogeochemistry of a north-temperate grassland with native ungulates: Nitrogen dynamics in Yellowstone National Park

Frank, Douglas A.; Inouye, Richard S.; Huntly, Nancy J.; Minshall, G. Wayne; Anderson, Jay E.

doi:10.1007/bf00002905

Cited by 133 publications

(111 citation statements)

References 48 publications

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“…Some movement of N down slope is likely to occur through hydrological processes, but since this is a semi-arid system, transport via water could be limited. Just as wild grazers play a crucial role as transporters of organic matter and nutrients in many systems (Frank et al 1994;Walker et al 2003;Schoenecker et al 2004;Holdo et al 2007), we suggest that domestic herds must have played a similar role in the Mongolian steppe for millennia. Currently, the livestock herds largely sort themselves across the topographic gradient, with sheep and goats foraging more often on steeper, upper slopes.…”

Section: Discussionmentioning

confidence: 96%

Legumes mitigate ecological consequences of a topographic gradient in a northern Mongolian steppe

et al. 2011

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Topography should create spatial variation in water and nutrients and play an especially important role in the ecology of water-limited systems. We use stable isotopes to discern how plants respond both to ecological gradients associated with elevation and to neighboring legumes on a south-facing slope in the semi-arid, historically grazed steppe of northern Mongolia. Out of three target species, Potentilla acaulis, Potentilla sericea, and Festuca lenensis, when >30 cm from a legume, all showed a decrease in leaf δ(15)N with increasing elevation. This, together with measures of soil δ(15)N, suggests greater N processing at the moister, more productive, lower elevation, and more N fixation at the upper elevation, where cover of legumes and lichens and plant-available nitrate were greater. Total soil N was greater at the lower elevation, but not lichen biomass or root colonization by AMF. Leaf δ(13)C values for P. acaulis and F. lenensis are consistent with increasing water stress with elevation; δ(13)C values indicated the greatest intrinsic water use efficiency for P. sericea, which is more abundant at the upper elevation. Nearby legumes (<10 cm) moderate the effect of elevation on leaf δ(15)N, confirming legumes' meaningful input of N, and affect leaf δ(13)C for two species, suggesting an influence on the efficiency of carbon fixation. Variation in leaf %N and %C as a function of elevation and proximity to a legume differs among species. Apparently, most N input is at upper elevations, pointing to the possible importance of grazers, in addition to hydrological processes, as transporters of N throughout this landscape.

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Section: Discussionmentioning

confidence: 96%

Legumes mitigate ecological consequences of a topographic gradient in a northern Mongolian steppe

et al. 2011

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“…Soil organic matter is an important integrating pool linking herbivore activities and nitrogen availability (Ruess and McNaughton 1987, Pastor et al 1988, Holland and Detling 1990, Frank et al 1994, Frank and Evans 1997, de Mazancourt et al 1998, Frank and Groffman 1998 (Fig. 1).…”

Section: Discussionmentioning

confidence: 99%

“…Net nitrogen mineralization measured in the field during the growing season following a vole population peak at two riparian sites in northern Yellowstone Park. Methods are after Adams and Attiwill (1986) and Frank et al (1994). sence of voles relative to that of soil from vole-accessible plots.…”

Section: Discussionmentioning

confidence: 99%

“…In some cases, the concentration of nitrogen in herbivore biomass and waste products leads to a fertilizer effect, stimulating nitrogen mineralization and increasing nitrogen availibility (McKendrick et al 1980, McNaughton et al 1988, Frank et al 1994, Shariff et al 1994, Pastor et al 1996, Frank and Evans 1997. Herbivory often increases the quality of the grazed plants by decreasing their C:N ratio (McNaughton 1979, Seastedt 1985, Seastedt et al 1988, Merrill et al 1994, which increases litter decomposition and stimulates net mineralization (Taylor et al 1989, Frank et al 1994, Scott and Binkley 1997, Frank and Groffman 1998. Herbivory-induced change in allocation of carbon and nitrogen in plant roots and shoots also tends to increase nitrogen turnover (Holland andDetling 1990, Merrill et al 1994).…”

Section: Introductionmentioning

confidence: 99%

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Direct and Indirect Effects of Herbivores on Nitrogen Dynamics: Voles in Riparian Areas

Sirotnak¹,

Huntly²

2000

Ecology

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Abstract. Herbivores can directly increase nitrogen mobility by increasing the quality of organic matter entering the decomposition cycle, but they also may decrease nitrogen mobility by decreasing the biomass of high-nitrogen species in the plant community. We assessed effects of voles (Microtus) on nitrogen dynamics using exclosures in two riparian meadows (Crystal Bench and Blacktail Deer Creek) in Yellowstone National Park (USA). At both sites, the quantity of plant litter was decreased by herbivory following a vole population peak in 1992. At Crystal Bench, removal of voles caused a decrease in the nitrogen concentration and an increase in the C:N ratio of plant litter over the four years of the study. The higher quality litter produced in the presence of voles at Crystal resulted in a larger pool of potentially mineralizable nitrogen in soil from control plots relative to soils from plots that had not been accessible to voles. At Crystal, vole removal did not cause a change in plant community composition. However, at Blacktail, after several years of vole exclusion, legumes became more common in exclosures than in control plots that were accessible to voles. Selective herbivory on high-nitrogen legumes kept the litter quality outside exclosures low, whereas higher legume biomass caused a decrease in C:N ratio of plant litter inside exclosures. The removal of voles at Blacktail caused a 15% increase in the fraction of the soil nitrogen that was rapidly mineralizable.Our results show that voles increased nitrogen mobility, especially during and after population peaks. However, that increase was offset by decreases in nitrogen mineralization over longer periods when voles caused a decrease in high-quality plant litter produced by preferred forage plants, especially legumes. Thus, both the mechanisms by which voles affected nitrogen dynamics and the net effects of voles varied over time and space. The balance of direct and indirect effects may provide a general mechanistic explanation of whether herbivores increase or decrease the rate of nitrogen cycling.

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“…There was no net movement of seed biomass between the two regions, but P was transported between the sites only due to the nutrient concentration gradient. There are several other similar studies showing the net movement of nutrients by animals (Frank et al 1994, Abbas 2012. Our mathematical framework enables us to estimate this process over all animals and long periods of time.…”

Section: Justification For the Random Walkmentioning

confidence: 82%

The impact of large animal extinctions on nutrient fluxes in early river valley civilizations

Doughty¹,

Wolf²,

Malhi³

2013

Ecosphere

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Abstract. Urbanization began independently in four river valley civilizations ;3,500-5,000 years before the present (ybp) in fertile river valleys that originally had free-ranging large animals, including elephants, that eventually went locally extinct. Such large animals are disproportionally important in the lateral spread of nutrients away from nutrient concentration gradients common near floodplains, and the local extinction of the animals would have reduced this flow of nutrients into surrounding regions. Prior to the use of manure as a fertilizer, this natural spread of nutrients would have increased productivity and food yield, and its absence would have immediately decreased fertility to regions outside the floodplains. Here we calculate this changing nutrient flux using a ''random walk'' model and estimate that phosphorus (P) concentrations in the vegetation were reduced by .40% outside the floodplain following the loss of these animals and the process could take between 840 and 6,800 years depending on the region and the model parameters used. In the short term, we hypothesize that the decreased fertility may have reduced food yields and driven early agriculturalists from the outer regions away from rivers towards the more fertile floodplains. In the long term, yield and populations in outer regions would have decreased, constraining the potential growth of these civilizations, thus demonstrating how the loss of a key ecosystem service could have important repercussions for humanity that continue over thousands of years.

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The biogeochemistry of a north-temperate grassland with native ungulates: Nitrogen dynamics in Yellowstone National Park

Cited by 133 publications

References 48 publications

Legumes mitigate ecological consequences of a topographic gradient in a northern Mongolian steppe

Legumes mitigate ecological consequences of a topographic gradient in a northern Mongolian steppe

Direct and Indirect Effects of Herbivores on Nitrogen Dynamics: Voles in Riparian Areas

The impact of large animal extinctions on nutrient fluxes in early river valley civilizations

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