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Rainfall variability has minimal effects on grassland recovery from repeated grazing
Author(s) -
Koerner Sally E.,
Collins Scott L.,
Blair John M.,
Knapp Alan K.,
Smith Melinda D.
Publication year - 2014
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.1111/jvs.12065
Subject(s) - grazing , grassland , forb , environmental science , growing season , precipitation , conservation grazing , ecosystem , grazing pressure , ecology , plant community , primary production , species richness , agronomy , atmospheric sciences , biology , geography , geology , meteorology
Question Mesic grasslands experience a complex disturbance regime including frequent fire, grazing by large ungulates and strong inter‐annual climate variability. As a result of climate change, growing season precipitation regimes are predicted to become more variable, with larger event sizes and longer dry periods resulting in more temporally dynamic soil moisture regimes. Increased climate variability is likely to interact with other disturbances, such as grazing, in grassland ecosystems. We investigated the individual and combined effects of increased rainfall variability and grazing on plant community composition, structure and function in an annually burned, native tallgrass prairie. Our overarching question was: are grazing impacts modified under a more variable precipitation regime? Location Konza Prairie, Kansas, USA . Methods Plots were established within a long‐term rainfall manipulation experiment in which larger, but less frequent, rain events were imposed during the growing season without altering the total rain amount. We then simulated intense grazing pressure during one growing season by repeatedly clipping all graminoids to 5 cm and monitored recovery over 3 yr. Results Neither grazing nor rainfall treatments affected species richness; however, grazing decreased total and grass above‐ground net primary production ( ANPP ) and increased forb ANPP relative to ungrazed plots. Grass stem density recovered from intense grazing under ambient rainfall but did not fully recover, even after 2 yr in the altered rainfall treatment. Conclusions We found that increased rainfall variability had little effect on tallgrass prairie structure and function, while grazing had large effects. Grazing and increased rainfall variability interacted to suppress grass stem density and delayed recovery relative to controls. Although stem density was reduced, individual stem size increased, resulting in no net change in ANPP . This suggests that ANPP in grazed and ungrazed North American tallgrass prairie may be relatively resilient under more temporally variable precipitation regimes.