Climatic/edaphic controls on soil carbon/nitrogen response to shrub encroachment in desert grassland

C. Winston Wheeler, Steve Archer, Gregory P. Asner, Chad R. McMurtry

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

The proliferation of woody plants in grasslands over the past 100+ years can alter carbon, nitrogen, and water cycles and influence land surface-atmosphere interactions. Although the majority of organic carbon in these ecosystems resides belowground, there is no consensus on how this change in land cover has affected soil organic carbon (SOC) and total nitrogen (TN) pools. The degree to which duration of woody plant occupation, climate, and edaphic conditions have mediated SOC and TN responses to changes in life-form composition are poorly understood. We addressed these issues at a desert grassland site in Arizona, USA, where the leguminous shrub velvet mesquite (Prosopis velutina) has proliferated along an elevation/precipitation/ temperature gradient and on contrasting soil morphologic surfaces. On sandy loam complexes of mid-Holocene origin, mean SOC and TN of soils in the grassland matrix increased ∼68% and ∼45%, respectively, with increasing elevation. Soil organic carbon pools were comparable and TN pools were ∼23% higher in Pleistocene-aged clay loam complexes co-occurring with Holocene-aged soils at the upper elevation/climatic zone. Across the site, belowground resources associated with large Prosopis plants were 21-154% (SOC) and 18-127% (TN) higher than those in the grassy matrix. The variance in SOC and TN pools accounted for by Prosopis stem size (a rough surrogate for time of site occupation) was highest at the low- and mid-elevation sites (69-74%) and lowest at the upper elevation site (32-38%). Soil δ15N values ranged from 5.5‰ to 6.7‰ across the soil/elevation zones but were comparable in herbaceous and shrub-impacted soils and exhibited a weak relationship with Prosopis basal stem diameter (r2, 0.1) and TN (r2, 0.08). The SOC δ13C values decreased linearly with increasing Prosopis basal diameter, suggesting that size and isotopic composition of the SOC pool is a function of time of Prosopis site occupation. Isotopic mixture models indicate that encroachment of C3 woody plants has also promoted SOC additions from C4 plant sources, indicative of long-term herbaceous facilitation. Grassy sites in contrasting soil/elevation combinations, initially highly distinctive in their SOC pool size and δ13C, appear to be converging on similar values following ∼100 years of woody plant proliferation.

Original languageEnglish (US)
Pages (from-to)1911-1928
Number of pages18
JournalEcological Applications
Volume17
Issue number7
DOIs
StatePublished - Oct 2007

Fingerprint

soil carbon
shrub
desert
grassland
nitrogen
organic carbon
soil
woody plant
occupation
stem
Holocene
C4 plant
matrix
clay loam
facilitation
sandy loam
temperature gradient
land surface
land cover
soil surface

Keywords

  • C
  • Carbon cycle
  • Carbon isotopes
  • Carbon sequestration
  • Mesquite
  • Prosopis velutina
  • Santa Rita experimental range, Arizona, USA
  • Soil nitrogen
  • Soil organic carbon
  • Sonoran desert
  • Woody plant encroachment

ASJC Scopus subject areas

  • Ecology

Cite this

Climatic/edaphic controls on soil carbon/nitrogen response to shrub encroachment in desert grassland. / Wheeler, C. Winston; Archer, Steve; Asner, Gregory P.; McMurtry, Chad R.

In: Ecological Applications, Vol. 17, No. 7, 10.2007, p. 1911-1928.

Research output: Contribution to journalArticle

Wheeler, C. Winston ; Archer, Steve ; Asner, Gregory P. ; McMurtry, Chad R. / Climatic/edaphic controls on soil carbon/nitrogen response to shrub encroachment in desert grassland. In: Ecological Applications. 2007 ; Vol. 17, No. 7. pp. 1911-1928.
@article{7d61abf425c0409e80faaa6916e7c63c,
title = "Climatic/edaphic controls on soil carbon/nitrogen response to shrub encroachment in desert grassland",
abstract = "The proliferation of woody plants in grasslands over the past 100+ years can alter carbon, nitrogen, and water cycles and influence land surface-atmosphere interactions. Although the majority of organic carbon in these ecosystems resides belowground, there is no consensus on how this change in land cover has affected soil organic carbon (SOC) and total nitrogen (TN) pools. The degree to which duration of woody plant occupation, climate, and edaphic conditions have mediated SOC and TN responses to changes in life-form composition are poorly understood. We addressed these issues at a desert grassland site in Arizona, USA, where the leguminous shrub velvet mesquite (Prosopis velutina) has proliferated along an elevation/precipitation/ temperature gradient and on contrasting soil morphologic surfaces. On sandy loam complexes of mid-Holocene origin, mean SOC and TN of soils in the grassland matrix increased ∼68{\%} and ∼45{\%}, respectively, with increasing elevation. Soil organic carbon pools were comparable and TN pools were ∼23{\%} higher in Pleistocene-aged clay loam complexes co-occurring with Holocene-aged soils at the upper elevation/climatic zone. Across the site, belowground resources associated with large Prosopis plants were 21-154{\%} (SOC) and 18-127{\%} (TN) higher than those in the grassy matrix. The variance in SOC and TN pools accounted for by Prosopis stem size (a rough surrogate for time of site occupation) was highest at the low- and mid-elevation sites (69-74{\%}) and lowest at the upper elevation site (32-38{\%}). Soil δ15N values ranged from 5.5‰ to 6.7‰ across the soil/elevation zones but were comparable in herbaceous and shrub-impacted soils and exhibited a weak relationship with Prosopis basal stem diameter (r2, 0.1) and TN (r2, 0.08). The SOC δ13C values decreased linearly with increasing Prosopis basal diameter, suggesting that size and isotopic composition of the SOC pool is a function of time of Prosopis site occupation. Isotopic mixture models indicate that encroachment of C3 woody plants has also promoted SOC additions from C4 plant sources, indicative of long-term herbaceous facilitation. Grassy sites in contrasting soil/elevation combinations, initially highly distinctive in their SOC pool size and δ13C, appear to be converging on similar values following ∼100 years of woody plant proliferation.",
keywords = "C, Carbon cycle, Carbon isotopes, Carbon sequestration, Mesquite, Prosopis velutina, Santa Rita experimental range, Arizona, USA, Soil nitrogen, Soil organic carbon, Sonoran desert, Woody plant encroachment",
author = "Wheeler, {C. Winston} and Steve Archer and Asner, {Gregory P.} and McMurtry, {Chad R.}",
year = "2007",
month = "10",
doi = "10.1890/06-1580.1",
language = "English (US)",
volume = "17",
pages = "1911--1928",
journal = "Ecological Appplications",
issn = "1051-0761",
publisher = "Ecological Society of America",
number = "7",

}

TY - JOUR

T1 - Climatic/edaphic controls on soil carbon/nitrogen response to shrub encroachment in desert grassland

AU - Wheeler, C. Winston

AU - Archer, Steve

AU - Asner, Gregory P.

AU - McMurtry, Chad R.

PY - 2007/10

Y1 - 2007/10

N2 - The proliferation of woody plants in grasslands over the past 100+ years can alter carbon, nitrogen, and water cycles and influence land surface-atmosphere interactions. Although the majority of organic carbon in these ecosystems resides belowground, there is no consensus on how this change in land cover has affected soil organic carbon (SOC) and total nitrogen (TN) pools. The degree to which duration of woody plant occupation, climate, and edaphic conditions have mediated SOC and TN responses to changes in life-form composition are poorly understood. We addressed these issues at a desert grassland site in Arizona, USA, where the leguminous shrub velvet mesquite (Prosopis velutina) has proliferated along an elevation/precipitation/ temperature gradient and on contrasting soil morphologic surfaces. On sandy loam complexes of mid-Holocene origin, mean SOC and TN of soils in the grassland matrix increased ∼68% and ∼45%, respectively, with increasing elevation. Soil organic carbon pools were comparable and TN pools were ∼23% higher in Pleistocene-aged clay loam complexes co-occurring with Holocene-aged soils at the upper elevation/climatic zone. Across the site, belowground resources associated with large Prosopis plants were 21-154% (SOC) and 18-127% (TN) higher than those in the grassy matrix. The variance in SOC and TN pools accounted for by Prosopis stem size (a rough surrogate for time of site occupation) was highest at the low- and mid-elevation sites (69-74%) and lowest at the upper elevation site (32-38%). Soil δ15N values ranged from 5.5‰ to 6.7‰ across the soil/elevation zones but were comparable in herbaceous and shrub-impacted soils and exhibited a weak relationship with Prosopis basal stem diameter (r2, 0.1) and TN (r2, 0.08). The SOC δ13C values decreased linearly with increasing Prosopis basal diameter, suggesting that size and isotopic composition of the SOC pool is a function of time of Prosopis site occupation. Isotopic mixture models indicate that encroachment of C3 woody plants has also promoted SOC additions from C4 plant sources, indicative of long-term herbaceous facilitation. Grassy sites in contrasting soil/elevation combinations, initially highly distinctive in their SOC pool size and δ13C, appear to be converging on similar values following ∼100 years of woody plant proliferation.

AB - The proliferation of woody plants in grasslands over the past 100+ years can alter carbon, nitrogen, and water cycles and influence land surface-atmosphere interactions. Although the majority of organic carbon in these ecosystems resides belowground, there is no consensus on how this change in land cover has affected soil organic carbon (SOC) and total nitrogen (TN) pools. The degree to which duration of woody plant occupation, climate, and edaphic conditions have mediated SOC and TN responses to changes in life-form composition are poorly understood. We addressed these issues at a desert grassland site in Arizona, USA, where the leguminous shrub velvet mesquite (Prosopis velutina) has proliferated along an elevation/precipitation/ temperature gradient and on contrasting soil morphologic surfaces. On sandy loam complexes of mid-Holocene origin, mean SOC and TN of soils in the grassland matrix increased ∼68% and ∼45%, respectively, with increasing elevation. Soil organic carbon pools were comparable and TN pools were ∼23% higher in Pleistocene-aged clay loam complexes co-occurring with Holocene-aged soils at the upper elevation/climatic zone. Across the site, belowground resources associated with large Prosopis plants were 21-154% (SOC) and 18-127% (TN) higher than those in the grassy matrix. The variance in SOC and TN pools accounted for by Prosopis stem size (a rough surrogate for time of site occupation) was highest at the low- and mid-elevation sites (69-74%) and lowest at the upper elevation site (32-38%). Soil δ15N values ranged from 5.5‰ to 6.7‰ across the soil/elevation zones but were comparable in herbaceous and shrub-impacted soils and exhibited a weak relationship with Prosopis basal stem diameter (r2, 0.1) and TN (r2, 0.08). The SOC δ13C values decreased linearly with increasing Prosopis basal diameter, suggesting that size and isotopic composition of the SOC pool is a function of time of Prosopis site occupation. Isotopic mixture models indicate that encroachment of C3 woody plants has also promoted SOC additions from C4 plant sources, indicative of long-term herbaceous facilitation. Grassy sites in contrasting soil/elevation combinations, initially highly distinctive in their SOC pool size and δ13C, appear to be converging on similar values following ∼100 years of woody plant proliferation.

KW - C

KW - Carbon cycle

KW - Carbon isotopes

KW - Carbon sequestration

KW - Mesquite

KW - Prosopis velutina

KW - Santa Rita experimental range, Arizona, USA

KW - Soil nitrogen

KW - Soil organic carbon

KW - Sonoran desert

KW - Woody plant encroachment

UR - http://www.scopus.com/inward/record.url?scp=39049084972&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=39049084972&partnerID=8YFLogxK

U2 - 10.1890/06-1580.1

DO - 10.1890/06-1580.1

M3 - Article

C2 - 17974331

AN - SCOPUS:39049084972

VL - 17

SP - 1911

EP - 1928

JO - Ecological Appplications

JF - Ecological Appplications

SN - 1051-0761

IS - 7

ER -