Amino acid abundance and proteolytic potential in North American soils

Hofmockel, Kirsten; Fierer, Noah; Colman, Benjamin P.; Jackson, Robert B.

doi:10.1007/s00442-010-1601-9

Cited by 39 publications

(44 citation statements)

References 47 publications

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“…Because only inorganic, and not organic, forms of N and P (nitrate, ammonium and inorganic phosphate) were measured, available N and P may have been underestimated. Although plants are capable of taking up organic N as amino acids that are present in many soils (Hofmockel et al ., ), it remains unclear how important organic N uptake is for plant nutrition (Näsholm et al ., ). Even less clear is the importance of organic P uptake (Macklon et al ., ).…”

Section: Methodsmentioning

confidence: 99%

Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland

Dijkstra

Pendall

Morgan³

et al. 2012

New Phytologist

218

155

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SummaryNitrogen (N) and phosphorus (P) are essential nutrients for primary producers and decomposers in terrestrial ecosystems. Although climate change affects terrestrial N cycling with important feedbacks to plant productivity and carbon sequestration, the impacts of climate change on the relative availability of N with respect to P remain highly uncertain.In a semiarid grassland in Wyoming, USA, we studied the effects of atmospheric CO 2 enrichment (to 600 ppmv) and warming (1.5/3.0°C above ambient temperature during the day/night) on plant, microbial and available soil pools of N and P.Elevated CO 2 increased P availability to plants and microbes relative to that of N, whereas warming reduced P availability relative to N. Across years and treatments, plant N : P ratios varied between 5 and 18 and were inversely related to soil moisture.Our results indicate that soil moisture is important in controlling P supply from inorganic sources, causing reduced P relative to N availability during dry periods. Both wetter soil conditions under elevated CO 2 and drier conditions with warming can further alter N : P. Although warming may alleviate N constraints under elevated CO 2 , warming and drought can exacerbate P constraints on plant growth and microbial activity in this semiarid grassland.

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Section: Methodsmentioning

confidence: 99%

Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland

Dijkstra

Pendall

Morgan³

et al. 2012

New Phytologist

218

155

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“…Finally, the previously published data on the activity of proteolytic enzyme under saturating conditions was assayed using casein, an animal protein, which is commonly used in soil assays to stimulate an unbound, unprotected protein [e.g., Lipson et al , 2001; Weintraub and Schimel , 2005; Hofmockel et al , 2010]. There is the potential that casein may be more easily degraded than the in situ soil protein pool because it lacks tertiary structure.…”

Section: Methodsmentioning

confidence: 99%

“…Chemical and physical protection of substrates from enzymatic attack is an important constraint on SOM decomposition, perhaps on par with that of temperature [ Davidson and Janssens , 2006; Hernández and Hobbie , 2010; German et al , 2011]. Substrate limitation of proteolytic enzyme activity is common in forest soils [ Berthrong and Finzi , 2006; Hofmockel et al , 2010] because of physical and chemical protection of proteins from enzymatic attack, and because of slow rates of diffusion through SOM [ Sollins et al , 2006; Rillig et al , 2007; McCarthy et al , 2008]. Thus, even if proteolytic enzymes were highly temperature sensitive, substrate limitation could limit the expression of temperature sensitivity in many forest soils, though we know relatively little about temperature versus substrate limitation to proteolytic enzyme activity.…”

Section: Introductionmentioning

confidence: 99%

Seasonal variation in the temperature sensitivity of proteolytic enzyme activity in temperate forest soils

Brzostek

Finzi

2012

J. Geophys. Res.

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.[1] Increasing soil temperature has the potential to alter the activity of the extracellular enzymes that mobilize nitrogen (N) from soil organic matter (SOM) and ultimately the availability of N for primary production. Proteolytic enzymes depolymerize N from proteinaceous components of SOM into amino acids, and their activity is a principal driver of the within-system cycle of soil N. The objectives of this study were to investigate whether the soils of temperate forest tree species differ in the temperature sensitivity of proteolytic enzyme activity over the growing season and the role of substrate limitation in regulating temperature sensitivity. Across species and sampling dates, proteolytic enzyme activity had relatively low sensitivity to temperature with a mean activation energy (E a ) of 33.5 kJ mol À1. E a declined in white ash, American beech, and eastern hemlock soils across the growing season as soils warmed. By contrast, E a in sugar maple soil increased across the growing season. We used these data to develop a species-specific empirical model of proteolytic enzyme activity for the 2009 calendar year and studied the interactive effects of soil temperature (ambient or +5°C) and substrate limitation (ambient or elevated protein) on enzyme activity. Declines in substrate limitation had a larger single-factor effect on proteolytic enzyme activity than temperature, particularly in the spring. There was, however, a large synergistic effect of increasing temperature and substrate supply on proteolytic enzyme activity. Our results suggest limited increases in N availability with climate warming unless there is a parallel increase in the availability of protein substrates.Citation: Brzostek, E. R., and A. C. Finzi (2012), Seasonal variation in the temperature sensitivity of proteolytic enzyme activity in temperate forest soils,

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“…In addition, this method April 2011 895 LIMITS TO PROTEOLYTIC ENZYME ACTIVITY integrates the activity of a larger suite of proteolytic enzymes in soils, which may have more relevance ecologically than more specific enzyme assays. We acknowledge the loss of plant-microbe interactions and soil disturbance as methodological artifacts when employing this assay of proteolytic enzyme activity (c.f., Hofmockel et al 2010). However, these assumptions are inherent to any assay of soil enzyme activity (Wallenstein and Weintraub 2008).…”

Section: Temperature and Substrate Limitation To Proteolytic Activitymentioning

confidence: 99%

Substrate supply, fine roots, and temperature control proteolytic enzyme activity in temperate forest soils

Brzostek¹,

Finzi²

2011

Ecology

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Temperature and substrate availability constrain the activity of the extracellular enzymes that decompose and release nutrients from soil organic matter (SOM). Proteolytic enzymes are the primary class of enzymes involved in the depolymerization of nitrogen (N) from proteinaceous components of SOM, and their activity affects the rate of N cycling in forest soils. The objectives of this study were to determine whether and how temperature and substrate availability affect the activity of proteolytic enzymes in temperate forest soils, and whether the activity of proteolytic enzymes and other enzymes involved in the acquisition of N (i.e., chitinolytic and ligninolytic enzymes) differs between trees species that form associations with either ectomycorrhizal or arbuscular mycorrhizal fungi. Temperature limitation of proteolytic enzyme activity was observed only early in the growing season when soil temperatures in the field were near 4 degrees C. Substrate limitation to proteolytic activity persisted well into the growing season. Ligninolytic enzyme activity was higher in soils dominated by ectomycorrhizal associated tree species. In contrast, the activity of proteolytic and chitinolytic enzymes did not differ, but there were differences between mycorrhizal association in the control of roots on enzyme activity. Roots of ectomycorrhizal species but not those of arbuscular mycorrhizal species exerted significant control over proteolytic, chitinolytic, and ligninolytic enzyme activity; the absence of ectomycorrhizal fine roots reduced the activity of all three enzymes. These results suggest that climate warming in the absence of increases in substrate availability may have a modest effect on soil-N cycling, and that global changes that alter belowground carbon allocation by trees are likely to have a larger effect on nitrogen cycling in stands dominated by ectomycorrhizal fungi.

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Amino acid abundance and proteolytic potential in North American soils

Cited by 39 publications

References 47 publications

Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland

Climate change alters stoichiometry of phosphorus and nitrogen in a semiarid grassland

Seasonal variation in the temperature sensitivity of proteolytic enzyme activity in temperate forest soils

Substrate supply, fine roots, and temperature control proteolytic enzyme activity in temperate forest soils

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