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Complexities of nitrogen isotope biogeochemistry in plant-soil systems: implications for the study of ancient agricultural and animal management practices.

Szpak P - Front Plant Sci (2014)

Bottom Line: This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions.The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems.Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

View Article: PubMed Central - PubMed

Affiliation: Department of Anthropology, University of British Columbia Vancouver, BC, Canada.

ABSTRACT
Nitrogen isotopic studies have the potential to shed light on the structure of ancient ecosystems, agropastoral regimes, and human-environment interactions. Until relatively recently, however, little attention was paid to the complexities of nitrogen transformations in ancient plant-soil systems and their potential impact on plant and animal tissue nitrogen isotopic compositions. This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions. This paper explores two larger themes that are prominent in archaeological studies using stable nitrogen isotope analysis: (1) agricultural practices (use of animal fertilizers, burning of vegetation or shifting cultivation, and tillage) and (2) animal domestication and husbandry (grazing intensity/stocking rate and the foddering of domestic animals with cultigens). The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems. Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

No MeSH data available.


Related in: MedlinePlus

Differences in δ15N between grains/fruits and above-ground plant parts. The grain or fruit tends to be depleted in 15N relative to the leaves and stems/stalks. Data are from studies examining effects of fertilizers on plant δ15N values and a “C” above a particular bar denotes that these data are from a control treatment in which no fertilizer was applied. Abbreviations at the bottom of the figure denote species represented and source for data. MZ, maize; RC, rice; S, squash; B, bean; P, pepper. Data obtained from: aSzpak et al. (2012a), bSzpak et al. (2012b), cChoi et al. (2002), dYun et al. (2011), eSzpak et al. (2014), fDel Amor et al. (2008).
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Figure 8: Differences in δ15N between grains/fruits and above-ground plant parts. The grain or fruit tends to be depleted in 15N relative to the leaves and stems/stalks. Data are from studies examining effects of fertilizers on plant δ15N values and a “C” above a particular bar denotes that these data are from a control treatment in which no fertilizer was applied. Abbreviations at the bottom of the figure denote species represented and source for data. MZ, maize; RC, rice; S, squash; B, bean; P, pepper. Data obtained from: aSzpak et al. (2012a), bSzpak et al. (2012b), cChoi et al. (2002), dYun et al. (2011), eSzpak et al. (2014), fDel Amor et al. (2008).

Mentions: Grains or fruits tend to act as strong N sinks. The amount of N that is remobilized to the grain from previously absorbed N is substantial, up to 85% in maize (Ta and Weiland, 1992), 100% in wheat (Martre et al., 2003; Tahir and Nakata, 2005), and 65% in rice (Mae and Ohira, 1981). Thus, fruits and grains should be systematically depleted in 15N relative to whole plants, leaves, and stems. In support of this notion, several studies have found lower δ15N values in grains relative to the leaves, stems, or shoots (Figure 8), the magnitude of which varies strongly with growing conditions, but is typically on the order of 1–4‰. Therefore, if animals were foddered to a significant extent on agricultural byproducts and humans consumed variable proportions of grains and those animals, there should be a convergence in the nitrogen isotopic compositions of the human and animal tissues relative to humans consuming variable proportions of grains and animals grazing on open pastures. This must be kept in mind when contemporaneous human and animal δ15N data are directly compared for paleodietary reconstructions, and considered as a possibility if higher than expected δ15N values are recorded in domestic animal tissues. Finally, agricultural systems tend to be characterized by higher N inputs (and in turn higher N losses) than non-agricultural systems, and are thus expected to be more prone to the loss of 14N (Kriszan et al., 2014). Therefore, animals foddered to a large extent on agricultural products or byproducts should be characterized by higher tissue δ15N values than animals grazing on wild pastures.


Complexities of nitrogen isotope biogeochemistry in plant-soil systems: implications for the study of ancient agricultural and animal management practices.

Szpak P - Front Plant Sci (2014)

Differences in δ15N between grains/fruits and above-ground plant parts. The grain or fruit tends to be depleted in 15N relative to the leaves and stems/stalks. Data are from studies examining effects of fertilizers on plant δ15N values and a “C” above a particular bar denotes that these data are from a control treatment in which no fertilizer was applied. Abbreviations at the bottom of the figure denote species represented and source for data. MZ, maize; RC, rice; S, squash; B, bean; P, pepper. Data obtained from: aSzpak et al. (2012a), bSzpak et al. (2012b), cChoi et al. (2002), dYun et al. (2011), eSzpak et al. (2014), fDel Amor et al. (2008).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4066317&req=5

Figure 8: Differences in δ15N between grains/fruits and above-ground plant parts. The grain or fruit tends to be depleted in 15N relative to the leaves and stems/stalks. Data are from studies examining effects of fertilizers on plant δ15N values and a “C” above a particular bar denotes that these data are from a control treatment in which no fertilizer was applied. Abbreviations at the bottom of the figure denote species represented and source for data. MZ, maize; RC, rice; S, squash; B, bean; P, pepper. Data obtained from: aSzpak et al. (2012a), bSzpak et al. (2012b), cChoi et al. (2002), dYun et al. (2011), eSzpak et al. (2014), fDel Amor et al. (2008).
Mentions: Grains or fruits tend to act as strong N sinks. The amount of N that is remobilized to the grain from previously absorbed N is substantial, up to 85% in maize (Ta and Weiland, 1992), 100% in wheat (Martre et al., 2003; Tahir and Nakata, 2005), and 65% in rice (Mae and Ohira, 1981). Thus, fruits and grains should be systematically depleted in 15N relative to whole plants, leaves, and stems. In support of this notion, several studies have found lower δ15N values in grains relative to the leaves, stems, or shoots (Figure 8), the magnitude of which varies strongly with growing conditions, but is typically on the order of 1–4‰. Therefore, if animals were foddered to a significant extent on agricultural byproducts and humans consumed variable proportions of grains and those animals, there should be a convergence in the nitrogen isotopic compositions of the human and animal tissues relative to humans consuming variable proportions of grains and animals grazing on open pastures. This must be kept in mind when contemporaneous human and animal δ15N data are directly compared for paleodietary reconstructions, and considered as a possibility if higher than expected δ15N values are recorded in domestic animal tissues. Finally, agricultural systems tend to be characterized by higher N inputs (and in turn higher N losses) than non-agricultural systems, and are thus expected to be more prone to the loss of 14N (Kriszan et al., 2014). Therefore, animals foddered to a large extent on agricultural products or byproducts should be characterized by higher tissue δ15N values than animals grazing on wild pastures.

Bottom Line: This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions.The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems.Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

View Article: PubMed Central - PubMed

Affiliation: Department of Anthropology, University of British Columbia Vancouver, BC, Canada.

ABSTRACT
Nitrogen isotopic studies have the potential to shed light on the structure of ancient ecosystems, agropastoral regimes, and human-environment interactions. Until relatively recently, however, little attention was paid to the complexities of nitrogen transformations in ancient plant-soil systems and their potential impact on plant and animal tissue nitrogen isotopic compositions. This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions. This paper explores two larger themes that are prominent in archaeological studies using stable nitrogen isotope analysis: (1) agricultural practices (use of animal fertilizers, burning of vegetation or shifting cultivation, and tillage) and (2) animal domestication and husbandry (grazing intensity/stocking rate and the foddering of domestic animals with cultigens). The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems. Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

No MeSH data available.


Related in: MedlinePlus