Title: Vulnerability of crops and native grasses to summer drying in the U.S. Southern Great Plains

Abstract

The Southern Great Plains are characterized by a fine-scale mixture of different land-cover types, predominantly winter-wheat and grazed pasture, with relatively small areas of other crops, native prairie, and switchgrass. Recent droughts and predictions of increased drought in the Southern Great Plains, especially during the summer months, raise concern for these ecosystems. We measured ecosystem carbon and water fluxes with eddy-covariance systems over cultivated cropland for 10 years, and over lightly grazed prairie and new switchgrass fields for 2 years each. Growing-season precipitation showed the strongest control over net carbon uptake for all ecosystems, but with a variable effect: grasses (prairie and switchgrass) needed at least 350. mm of precipitation during the growing season to become net carbon sinks, while crops needed only 100. mm. In summer, high temperatures enhanced evaporation and led to higher likelihood of dry soil conditions. Therefore, summer-growing native prairie species and switchgrass experienced more seasonal droughts than spring-growing crops. For wheat, the net reduction in carbon uptake resulted mostly from a decrease in gross primary production rather than an increase in respiration. Flux measurements suggested that management practices for crops were effective in suppressing evapotranspiration and decomposition (by harvesting and removing secondary growth), and inmore » increasing carbon uptake (by fertilizing and conserving summer soil water). In light of future projections for wetter springs and drier and warmer summers in the Southern Great Plains, our study indicates an increased vulnerability in native ecosystems and summer crops over time.« less

Authors:

Raz-Yaseef, Naama; Billesbach, Dave P.; Fischer, Marc L.; Biraud, Sebastien C.; Gunter, Stacey A.; Bradford, James A.; Torn, Margaret S.

Publication Date:

Tue Dec 01 00:00:00 EST 2015

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1245476

Alternate Identifier(s):

OSTI ID: 1213682; OSTI ID: 1470997

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Agriculture, Ecosystems and Environment

Additional Journal Information:

Journal Name: Agriculture, Ecosystems and Environment Journal Volume: 213 Journal Issue: C; Journal ID: ISSN 0167-8809

Publisher:

Elsevier

Country of Publication:

Netherlands

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Agriculture; Drought; Southern Great Plains; Wheat; Switchgrass; Prairie; NEE; GPP; Evapotranspiration