TY - JOUR
T1 - Differential use of large summer rainfall events by shrubs and grasses
T2 - A manipulative experiment in the Patagonian steppe
AU - Golluscio, R. A.
AU - Sala, O. E.
AU - Lauenroth, W. K.
N1 - Funding Information:
Acknowledgements This work was funded by the US National Science Foundation (Cross-site LTER-DEB 9416815), Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, and Antorchas Foundation (Argentina). We acknowledge Instituto Nacional de Tecnología Agropecuaria INTA (Argentina) for its permission to use facilities at the Río Mayo Experimental Field Station, Chubut. We are grateful for the field aid and critical suggestions of Alberto Soriano, Martín Aguiar, José Paruelo, Roberto Fernández, Pablo Roset, and Adrián Nuñez. This work contributes to the Global Change and Terrestrial Ecosystems Core Project of the International Geosphere-Biosphere Programme.
PY - 1998/6
Y1 - 1998/6
N2 - In the Patagonian steppe, years with above-average precipitation (wet years) are characterized by the occurrence of large rainfall events. The objective of this paper was to analyze the ability of shrubs and grasses to use these large events. Shrubs absorb water from the lower layers, grasses from the upper layers, intercepting water that would otherwise reach the layers exploited by shrubs. We hypothesized that both lifeforms could use the large rainfalls and that the response of shrubs could be more affected by the presence of grasses than vice versa. We performed a field experiment using a factorial combination of water addition and lifeform removal, and repeated it during the warm season of three successive years. The response variables were leaf growth, and soil and plant water potential. Grasses always responded to experimental large rainfall events, and their response was greater in dry than in wet years. Shrubs only used large rainfalls in the driest year, when the soil water potential in the deep layers was low. The presence or absence of one life-form did not modify the response of the other. The magnitude of the increase in soil water potential was much higher in dry than in humid years, suggesting an explanation for the differences among years in the magnitude of the response of shrubs and grasses. We propose that the generally reported poor response of deep-rooted shrubs to summer rainfalls could be because (1) the water is insufficient to reach deep soil layers, (2) the plants are in a dormant phenological status, and/or (3) deep soil layers have a high water potential. The two last situations may result in high deep-drainage losses, one of the most likely explanations for the elsewhere-reported low response of aboveground net primary production to precipitation during wet years.
AB - In the Patagonian steppe, years with above-average precipitation (wet years) are characterized by the occurrence of large rainfall events. The objective of this paper was to analyze the ability of shrubs and grasses to use these large events. Shrubs absorb water from the lower layers, grasses from the upper layers, intercepting water that would otherwise reach the layers exploited by shrubs. We hypothesized that both lifeforms could use the large rainfalls and that the response of shrubs could be more affected by the presence of grasses than vice versa. We performed a field experiment using a factorial combination of water addition and lifeform removal, and repeated it during the warm season of three successive years. The response variables were leaf growth, and soil and plant water potential. Grasses always responded to experimental large rainfall events, and their response was greater in dry than in wet years. Shrubs only used large rainfalls in the driest year, when the soil water potential in the deep layers was low. The presence or absence of one life-form did not modify the response of the other. The magnitude of the increase in soil water potential was much higher in dry than in humid years, suggesting an explanation for the differences among years in the magnitude of the response of shrubs and grasses. We propose that the generally reported poor response of deep-rooted shrubs to summer rainfalls could be because (1) the water is insufficient to reach deep soil layers, (2) the plants are in a dormant phenological status, and/or (3) deep soil layers have a high water potential. The two last situations may result in high deep-drainage losses, one of the most likely explanations for the elsewhere-reported low response of aboveground net primary production to precipitation during wet years.
KW - Aboveground net primary production
KW - Patagonian steppe
KW - Percolation
KW - Water stress
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U2 - 10.1007/s004420050486
DO - 10.1007/s004420050486
M3 - Article
AN - SCOPUS:0031864334
SN - 0029-8549
VL - 115
SP - 17
EP - 25
JO - Oecologia
JF - Oecologia
IS - 1-2
ER -