Grassland ecophysiology and grazing ecology

Bieber, León

doi:10.1079/9780851994529.0000

Cited by 41 publications

(3 citation statements)

References 1 publication

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“…Grazing may influence SOC directly via effects on plant carbon allocation and soil resource availability, and indirectly via effects on long-term plant community composition (Piñeiro et al, 2010). In the short term, root carbon allocation is often lower under grazing in favor of rapid re-establishment of photosynthetic tissue (Briske & Richards, 1995;Dawson, Grayston, & Paterson, 2000), but the longterm effects of grazing on belowground biomass vary considerably (Bardgett, Wardle, & Yeates, 1998;Hafner et al, 2012;Milchunas & Lauenroth, 1993). As such, root biomass may be critical for sustaining SOC (Rasse, Rumpel, & Dignac, 2005), especially in grasslands where aboveground tissue is lost to grazing or fire.…”

Section: Introductionmentioning

confidence: 99%

Grazing enhances belowground carbon allocation, microbial biomass, and soil carbon in a subtropical grassland

Wilson

Strickland

Hutchings

et al. 2018

Global Change Biology

197

135

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Despite the large contribution of rangeland and pasture to global soil organic carbon (SOC) stocks, there is considerable uncertainty about the impact of large herbivore grazing on SOC, especially for understudied subtropical grazing lands. It is well known that root system inputs are the source of most grassland SOC, but the impact of grazing on partitioning of carbon allocation to root tissue production compared to fine root exudation is unclear. Given that different forms of root C have differing implications for SOC synthesis and decomposition, this represents a significant gap in knowledge. Root exudates should contribute to SOC primarily after microbial assimilation, and thus promote microbial contributions to SOC based on stabilization of microbial necromass, whereas root litter deposition contributes directly as plant-derived SOC following microbial decomposition. Here, we used in situ isotope pulse-chase methodology paired with plant and soil sampling to link plant carbon allocation patterns with SOC pools in replicated long-term grazing exclosures in subtropical pasture in Florida, USA. We quantified allocation of carbon to root tissue and measured root exudation across grazed and ungrazed plots and quantified lignin phenols to assess the relative contribution of microbial vs. plant products to total SOC. We found that grazing exclusion was associated with dramatically less overall belowground allocation, with lower root biomass, fine root exudates, and microbial biomass. Concurrently, grazed pasture contained greater total SOC, and a larger fraction of SOC that originated from plant tissue deposition, suggesting that higher root litter deposition under grazing promotes greater SOC. We conclude that grazing effects on SOC depend on root system biomass, a pattern that may generalize to other C4-dominated grasslands, especially in the subtropics. Improved understanding of ecological factors underlying root system biomass may be the key to forecasting SOC and optimizing grazing management to enhance SOC accumulation.

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Section: Introductionmentioning

confidence: 99%

Grazing enhances belowground carbon allocation, microbial biomass, and soil carbon in a subtropical grassland

Wilson

Strickland

Hutchings

et al. 2018

Global Change Biology

197

135

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“…Grazing by livestock affects the dynamics of soil C in three main ways (McSherry & Ritchie, 2013;Tang et al, 2019): (a) foraging directly reduces the net primary production of grasses and, as its indirect consequence, decreases the amount of C added to soil through above-ground litter (Martinsen et al, 2011;Sun et al, 2011); (b) grazing influences the allocation of plant C between the above-ground and below-ground components, typically favoring photosynthetic tissues over roots in the short term (Dawson et al, 2000), although its long-term impacts on root biomass to vary greatly (Hafner et al, 2012;Wilson et al, 2018); and (c) grazing can affect the physical properties of soil such as its structure, infiltration capacity, macroporosity, and moisture content as the soil becomes compact and hard as a result of being trampled upon, as well as its chemical properties through the addition of animal dung and urine, which, in turn, influences the dynamics of soil C and the activity of soil microbes . The overall effects of grazing on soil C are thus complex and regulated by many different biogeochemical processes, environmental variables (e.g., precipitation, soil type, and soil depth), and management practices (e.g., grazing intensity and duration; McSherry & Ritchie, 2013).…”

Section: Introductionmentioning

confidence: 99%

Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis

Jiang

Lai

et al. 2020

Global Change Biology

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Grazing by livestock greatly affects the soil carbon (C) cycle in grassland ecosystems. However, the effects of grazing at different intensities and durations on the dynamics of soil C in its subsoil layers are not clearly understood. Here, we compiled data from 78 sites (in total 122 published studies) to examine the effects of varying grazing intensities and durations on soil C content at different depths for grasslands in China.

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“…The results of this study indicate the great flexibility in adapting to defoliation by marandu palisadegrass, through different morphogenetic adjustments to the seasonal variation in sward height. It is possible that the decreasing height promotes the accumulation of reserve compounds in the winter, even with little growth, which might favour regrowth in the spring through the mobilisation of these reserves (THORNTON et al, 2000), associated with medium defoliation (30 cm). Moreover, the grass lowering in the summer to 15 cm re-establishes the tissue-flow potential under favourable environmental conditions.…”

Section: Discussionmentioning

confidence: 99%

The morphogenesis of marandu palisadegrass at fixed or variable heights in different seasons of the year

Santos

Cardoso

Silva³

et al. 2020

Biosci. J.

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Height variations in a sward over the year may be efficient for increasing plant growth, compared with maintenance of the sward at a constant height. Thus, this experiment was conducted from February 2013 to May 2014 to characterise the development of Urochloa brizantha syn. Brachiaria brizantha cv. Marandu (marandu palisadegrass), managed under three defoliation strategies: constant height (30 cm during the entire experimental period), increasing height (15 cm in the winter, 30 cm in the spring, and 45 cm in the summer), and decreasing height (45 cm in the winter, 30 cm in the spring, and 15 cm in the summer). The experimental design was completely randomised, in a split-plot arrangement, with four replicates. Phyllochron was higher in the winter, but leaf and stem elongation rates and the number of live leaves per tiller were lower compared with the spring and summer. In the summer, the swards under increasing height displayed a higher phyllochron than those under decreasing and constant height. When comparing seasons, the highest leaf senescence rate occurred in spring. In the winter, the sward with increasing height had shorter leaves and stems, in contrast to the summer. The sward under decreasing height showed a high stem elongation rate in the spring. Marandu palisadegrass has great flexibility in terms of defoliation management and a typical seasonal development pattern. Modifying the sward height results in a gradual change in the development of marandu palisadegrass and generates residual effects on the subsequent season.

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Grassland ecophysiology and grazing ecology

Cited by 41 publications

References 1 publication

Grazing enhances belowground carbon allocation, microbial biomass, and soil carbon in a subtropical grassland

Grazing enhances belowground carbon allocation, microbial biomass, and soil carbon in a subtropical grassland

Light grazing facilitates carbon accumulation in subsoil in Chinese grasslands: A meta‐analysis

The morphogenesis of marandu palisadegrass at fixed or variable heights in different seasons of the year

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