Potential nitrogen constraints on soil carbon sequestration under low and elevated atmospheric CO2.

The interaction between nitrogen cycling and carbon sequestration is critical in predicting the consequences of anthropogenic increases in atmospheric CO2 (hereafter, Ca). The progressive N limitation (PNL) theory predicts that carbon sequestration in plants and soils with rising Ca may be constrained by the availability of nitrogen in many ecosystems. Here we report on the interaction between C and N dynamics during a four-year field experiment in which an intact C3/C4 grassland was exposed to a gradient in Ca from 200 to 560 micromol/mol. There were strong species effects on decomposition dynamics, with C loss positively correlated and N mineralization negatively correlated with Ca for litter of the C3 forb Solanum dimidiatum, whereas decomposition of litter from the C4 grass Bothriochloa ischaemum was unresponsive to Ca. Both soil microbial biomass and soil respiration rates exhibited a nonlinear response to Ca, reaching a maximum at approximately 440 micromol/mol Ca. We found a general movement of N out of soil organic matter and into aboveground plant biomass with increased Ca. Within soils we found evidence of C loss from recalcitrant soil C fractions with narrow C:N ratios to more labile soil fractions with broader C:N ratios, potentially due to decreases in N availability. The observed reallocation of N from soil to plants over the last three years of the experiment supports the PNL theory that reductions in N availability with rising Ca could initially be overcome by a transfer of N from low C:N ratio fractions to those with higher C:N ratios. Although the transfer of N allowed plant production to increase with increasing Ca, there was no net soil C sequestration at elevated Ca, presumably because relatively stable C is being decomposed to meet microbial and plant N requirements. Ultimately, if the C gained by increased plant production is rapidly lost through decomposition, the shift in N from older soil organic matter to rapidly decomposing plant tissue may limit net C sequestration with increased plant production.

[1]  F. Chapin,et al.  Plant Species Mediate Changes in Soil Microbial N in Response to Elevated CO 2 Author ( s ) : , 2007 .

[2]  W. Parton,et al.  Progressive Nitrogen Limitation of Ecosystem Responses to Rising Atmospheric Carbon Dioxide , 2004 .

[3]  A. Gorissen,et al.  Decomposition of leaf and root tissue of three perennial grass species grown at two levels of atmospheric CO2 and N supply , 2000, Plant and Soil.

[4]  R. B. Jackson,et al.  CO2 alters water use, carbon gain, and yield for the dominant species in a natural grassland , 1994, Oecologia.

[5]  P. Curtis,et al.  Elevated atmospheric CO2 and feedback between carbon and nitrogen cycles , 1993, Plant and Soil.

[6]  F. Bazzaz,et al.  The response of plants to elevated CO2 , 1984, Oecologia.

[7]  Daniel G. Milchunas,et al.  CO2 ENHANCES PRODUCTIVITY, ALTERS SPECIES COMPOSITION, AND REDUCES DIGESTIBILITY OF SHORTGRASS STEPPE VEGETATION , 2004 .

[8]  S. C. Geijn,et al.  Implications of increased carbon dioxide levels for carbon input and turnover in soils , 2004, Vegetatio.

[9]  W. Parton,et al.  Plant Nitrogen Dynamics in Shortgrass Steppe under Elevated Atmospheric Carbon Dioxide , 2004, Ecosystems.

[10]  Christopher B. Field,et al.  Nitrogen and Climate Change , 2003, Science.

[11]  J. Derner,et al.  Increasing CO2 from subambient to superambient concentrations alters species composition and increases above-ground biomass in a C3 /C4 grassland. , 2003, The New phytologist.

[12]  J. Derner,et al.  Increasing CO 2 from subambient to superambient concentrations alters species composition and increases above-ground biomass in a C 3 / C 4 grassland , 2003 .

[13]  W. Schlesinger,et al.  Species control variation in litter decomposition in a pine forest exposed to elevated CO2 , 2002 .

[14]  W. Horwath,et al.  Linking sequestration of 13C and 15N in aggregates in a pasture soil following 8 years of elevated atmospheric CO2 , 2002 .

[15]  V. Bailey,et al.  Relationships between soil microbial biomass determined by chloroform fumigation–extraction, substrate-induced respiration, and phospholipid fatty acid analysis , 2002 .

[16]  R. B. Jackson,et al.  Nonlinear grassland responses to past and future atmospheric CO2 , 2002, Nature.

[17]  R. Phillips,et al.  Microbial community composition and function beneath temperate trees exposed to elevated atmospheric carbon dioxide and ozone , 2002, Oecologia.

[18]  H. W. Polley,et al.  Gas exchange and photosynthetic acclimation over subambient to elevated CO 2 in a C 3 -C 4 grassland , 2001 .

[19]  F. Chapin,et al.  Erratum to “Contrasting effects of elevated CO 2 on old and new soil carbon pools” [Soil Biology & Biochemistry 33(6) 365–373] , 2001 .

[20]  William H. Schlesinger,et al.  Limited carbon storage in soil and litter of experimental forest plots under increased atmospheric CO2 , 2001, Nature.

[21]  G. Katul,et al.  Soil fertility limits carbon sequestration by forest ecosystems in a CO2-enriched atmosphere , 2001, Nature.

[22]  Philip Ineson,et al.  Elevated CO2, litter chemistry, and decomposition: a synthesis , 2001, Oecologia.

[23]  F. Chapin,et al.  Contrasting effects of elevated CO2 on old and new soil carbon pools , 2001 .

[24]  C. Field,et al.  Nitrogen limitation of microbial decomposition in a grassland under elevated CO2 , 2001, Nature.

[25]  H. W. Polley,et al.  Elongated chambers for field studies across atmospheric CO2 gradients. , 2000 .

[26]  R. B. Jackson,et al.  THE VERTICAL DISTRIBUTION OF SOIL ORGANIC CARBON AND ITS RELATION TO CLIMATE AND VEGETATION , 2000 .

[27]  P. Curtis,et al.  ATMOSPHERIC CO2 AND THE COMPOSITION AND FUNCTION OF SOIL MICROBIAL COMMUNITIES , 2000 .

[28]  I. Burke,et al.  Relationship Between Root Biomass and Soil Organic Matter Pools in the Shortgrass Steppe of Eastern Colorado , 1999, Ecosystems.

[29]  Johan Six,et al.  Aggregation and soil organic matter accumulation in cultivated and native grassland soils , 1998 .

[30]  P. Ineson,et al.  Elevated CO2 reduces the nitrogen concentration of plant tissues , 1998 .

[31]  R. B. Jackson,et al.  The fate of carbon in grasslands under carbon dioxide enrichment , 1997, Nature.

[32]  Edward B. Rastetter,et al.  RESPONSES OF N‐LIMITED ECOSYSTEMS TO INCREASED CO2: A BALANCED‐NUTRITION, COUPLED‐ELEMENT‐CYCLES MODEL , 1997 .

[33]  F. Chapin,et al.  Decomposition of litter produced under elevated CO2: Dependence on plant species and nutrient supply , 1997 .

[34]  I. Burke,et al.  Soil organic matter and nutrient availability responses to reduced plant inputs in shortgrass steppe , 1996 .

[35]  Jay M. Ham,et al.  Fluxes of CO2 and water vapor from a prairie ecosystem exposed to ambient and elevated atmospheric CO2 , 1995 .

[36]  E. T. Elliott,et al.  Particulate soil organic-matter changes across a grassland cultivation sequence , 1992 .

[37]  M. Mousseau,et al.  Increased Atmospheric CO 2 and Litter Quality: Decomposition of Sweet Chestnut Leaf Litter with Animal Food Webs of Different Complexities , 1991 .

[38]  F. A. Bazzaz,et al.  The Response of Natural Ecosystems to the Rising Global CO2 Levels , 1990 .

[39]  F. A. Bazzaz,et al.  The Response of Annuals in Competitive Neighborhoods: Effects of Elevated CO2 , 1988 .

[40]  F. S. Nakayama,et al.  Soil Carbon Dioxide Distribution and Flux within the Open-top Chamber , 1988 .

[41]  B. Strain,et al.  Effects of CO2 enrichment and water stress on growth of Liquidambar styraciflua and Pinus taeda seedlings , 1984 .

[42]  D. Patterson,et al.  Interacting Effects of CO2 and Nutrient Concentration , 1982, Weed Science.

[43]  D. Mortensen,et al.  Growth Response of Wheat to CO2 Enrichment and Different Levels of Mineral Nutrition1 , 1981 .

[44]  K. Domsch,et al.  A physiological method for the quantitative measurement of microbial biomass in soils , 1978 .

[45]  J. P. E. AND-N.  A PHYSIOLOGICAL METHOD FOR THE QUANTITATIVE MEASUREMENT OF MICROBIAL BIOMASS IN SOILS , 2022 .