Biological nitrogen fixation in mixed legume/grass pastures

Ledgard, S. F.; Steele, K. W.

doi:10.1007/978-94-017-0910-1_8

Cited by 123 publications

(161 citation statements)

References 37 publications

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“…The between grass-legume functional group interaction coefficients were strong and positive for each function highlighting the benefits of mixing these functional groups for multifunctionality in grassland systems (Table 1a). This benefit is well documented for individual functions (Ledgard & Steele 1992;Spehn et al 2002;Nyfeler et al 2011) but is shown here for the first time for ecosystem multifunctionality. The two grasses also interacted strongly and positively for both sown biomass and N yield perhaps reflecting the fast-establishing and temporally persistent traits of G1 and G2 respectively.…”

Section: Discussionsupporting

confidence: 55%

Testing the effects of diversity on ecosystem multifunctionality using a multivariate model

et al. 2015

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Most ecosystems provide multiple services, thus the impact of biodiversity losses on ecosystem functions may be considerably underestimated by studies that only address single functions. We propose a multivariate modelling framework for quantifying the relationship between biodiversity and multiple ecosystem functions (multifunctionality). Our framework consolidates the strengths of previous approaches to analysing ecosystem multifunctionality and contributes several advances. It simultaneously assesses the drivers of multifunctionality, such as species relative abundances, richness, evenness and other manipulated treatments. It also tests the relative importance of these drivers across functions, incorporates correlations among functions and identifies conditions where all functions perform well and where trade‐offs occur among functions. We illustrate our framework using data from three ecosystem functions (sown biomass, weed suppression and nitrogen yield) in a four‐species grassland experiment. We found high variability in performance across the functions in monocultures, but as community diversity increased, performance increased and variability across functions decreased.

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Section: Discussionsupporting

confidence: 55%

Testing the effects of diversity on ecosystem multifunctionality using a multivariate model

et al. 2015

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“…The method to compute N gainmix has been previously used to calculate the amount of apparent symbiotic N 2 fixation (N sym ) in grass-legume mixtures ('N-difference method', e.g., Ledgard & Steele, 1992). The N-difference method has been criticized because it assumes that the cumulative uptake of N from soil and fertilizer of grasses and legumes in mixture would be the same as for the reference grass monoculture, which may not necessarily be the case (Boller & N€ osberger, 1987;Nyfeler et al, 2011).…”

Section: N Yield Gain In Mixtures Is Evident Over a Wide Range Of Legmentioning

confidence: 99%

Nitrogen yield advantage from grass–legume mixtures is robust over a wide range of legume proportions and environmental conditions

Suter

Connolly

Finn

et al. 2015

Global Change Biology

164

130

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Current challenges to global food security require sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N), increased protein self‐sufficiency through homegrown crops, and reduced N losses to the environment. Such challenges were addressed in a continental‐scale field experiment conducted over 3 years, in which the amount of total nitrogen yield (Ntot) and the gain of N yield in mixtures as compared to grass monocultures (Ngainmix) was quantified from four‐species grass–legume stands with greatly varying legume proportions. Stands consisted of monocultures and mixtures of two N2‐fixing legumes and two nonfixing grasses. The amount of Ntot of mixtures was significantly greater (P ≤ 0.05) than that of grass monocultures at the majority of evaluated sites in all 3 years. Ntot and thus Ngainmix increased with increasing legume proportion up to one‐third of legumes. With higher legume percentages, Ntot and Ngainmix did not continue to increase. Thus, across sites and years, mixtures with one‐third proportion of legumes attained ~95% of the maximum Ntot acquired by any stand and had 57% higher Ntot than grass monocultures. Realized legume proportion in stands and the relative N gain in mixture (Ngainmix/Ntot in mixture) were most severely impaired by minimum site temperature (R = 0.70, P = 0.003 for legume proportion; R = 0.64, P = 0.010 for Ngainmix/Ntot in mixture). Nevertheless, the relative N gain in mixture was not correlated to site productivity (P = 0.500), suggesting that, within climatic restrictions, balanced grass–legume mixtures can benefit from comparable relative gains in N yield across largely differing productivity levels. We conclude that the use of grass–legume mixtures can substantially contribute to resource‐efficient agricultural grassland systems over a wide range of productivity levels, implying important savings in N fertilizers and thus greenhouse gas emissions and a considerable potential for climate change mitigation.

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“…Legumes, with their nitrogen-fixing capability, may increase soil nitrate through turnover of nitrogen-rich leaves or roots (Table 3, Fig. 5) (Vitousek et al 1987, Vitousek and Howarth 1991, Ledgard and Steele 1992. Reduced light levels may be associated with shading by the greater abundance of broad-leaved legumes and woody plants such as Lathyrus venosus and Quercus spp.…”

Section: Herbivore Effects On Plant Resources and Allocationmentioning

confidence: 99%

Herbivore Effects on Plant and Nitrogen Dynamics in Oak Savanna

Ritchie

Tilman

Knops

1998

Ecology

436

261

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Herbivores can often control plant dynamics by mediating positive feedbacks in plant species’ influence on nutrient cycling. In a 7‐yr field experiment in a nitrogen‐limited Minnesota oak savanna, we tested whether herbivores accelerated or decelerated nitrogen (N) cycling through their effects on plants. We measured effects of excluding insect (primarily Orthoptera and Homoptera) and mammalian herbivores (primarily white‐tailed deer, Odocoileus virginianus) on above‐ and belowground plant biomass, plant species composition, plant tissue nitrogen concentration, available soil N and light, and total N and carbon (C) in different pools (soil, roots, litter, etc.). Herbivore exclusion strongly increased cover and biomass of the legume Lathyrus venosus and a few species of woody plants. These effects were associated with greater aboveground standing crop, reduced belowground standing crop, and reduced light penetration to the ground surface. Herbivore exclusion also modified N cycling through greater N content of live, aboveground plant tissue early in the growing season and of litter and belowground tissue late in the growing season. Herbivore exclusion also increased soil nitrate and total available N concentrations but did not alter total soil or plant N. Our results support the hypothesis that herbivores indirectly decelerate N cycling by decreasing the abundance of plant species with nitrogen‐rich tissues. However, other factors, such as disturbance from fire, may mediate herbivore effects on long‐term changes in N and C pools. Herbivores may therefore indirectly control productivity, N cycling, and succession by consuming nitrogen‐fixing and woody plants that have strong effects on plant resources (e.g., nitrogen and light).

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Biological nitrogen fixation in mixed legume/grass pastures

Cited by 123 publications

References 37 publications

Testing the effects of diversity on ecosystem multifunctionality using a multivariate model

Testing the effects of diversity on ecosystem multifunctionality using a multivariate model

Nitrogen yield advantage from grass–legume mixtures is robust over a wide range of legume proportions and environmental conditions

Herbivore Effects on Plant and Nitrogen Dynamics in Oak Savanna

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