IFEVA   02662
INSTITUTO DE INVESTIGACIONES FISIOLOGICAS Y ECOLOGICAS VINCULADAS A LA AGRICULTURA
Unidad Ejecutora - UE
artículos
Título:
Vegetation structure constrains primary production response to increased water availability in the Patagonian steppe of Argentina.
Autor/es:
L. YAHDJIAN; O. SALA
Revista:
ECOLOGY
Referencias:
Año: 2006 vol. 87 p. 952 - 962
ISSN:
0012-9658
Resumen:
Grassland aboveground net primary production (ANPP) increases linearly with
precipitation in space and time, but temporal models relating time series of ANPP and annual
precipitation for single sites show lower slopes and regression coefficients than are shown by
spatial models. The analysis of several ANPP time series showed lags in the ecosystem
response to increased water availability, which may explain the difference between spatial and
temporal models. The lags may result from constraints that ecosystems experience after
drought. Our objective was to explore the structural constraints of the ANPP response to
rainfall variability in a semiarid ecosystem, the Patagonian steppe, in southern Argentina.
We designed a 3-yr rainfall manipulation experiment where we decreased water input with
rainout shelters during two consecutive years, which included three levels of rainfall
interception (30%, 55%, and 80%) and a control. In the third year, we irrigated one-half of the
plots of each rainfall-interception treatment. We evaluated the immediate effects of drought
on current-year ANPP and the effects of previous-year drought on vegetation recovery after
water supplementation.
ANPP (gm2yr1) was linearly related to annual precipitation input (APPT; mm/yr) along
the experimental precipitation gradient (ANPP¼0.133APPTþ58.3; r2¼0.34, P , 0.01), and
this relationship was mostly accounted for by changes in the ANPP of grasses. Plant density
(D; no. individuals/mm2) was related to the precipitation received during the drought period
(D¼0.113APPTþ18; r2¼0.39, P , 0.05). The recovery of plants after irrigation was lower
for those plots that had experienced experimental drought the previous years relative to
controls, and the lags were proportional to the intensity of drought. Therefore, our results
suggest that the density of plants may constrain the recovery of vegetation after drought, and
these constraints may determine lags that limit the capacity of the ecosystem to take advantage
of wet years after dry years.%, 55%, and 80%) and a control. In the third year, we irrigated one-half of the
plots of each rainfall-interception treatment. We evaluated the immediate effects of drought
on current-year ANPP and the effects of previous-year drought on vegetation recovery after
water supplementation.
ANPP (gm2yr1) was linearly related to annual precipitation input (APPT; mm/yr) along
the experimental precipitation gradient (ANPP¼0.133APPTþ58.3; r2¼0.34, P , 0.01), and
this relationship was mostly accounted for by changes in the ANPP of grasses. Plant density
(D; no. individuals/mm2) was related to the precipitation received during the drought period
(D¼0.113APPTþ18; r2¼0.39, P , 0.05). The recovery of plants after irrigation was lower
for those plots that had experienced experimental drought the previous years relative to
controls, and the lags were proportional to the intensity of drought. Therefore, our results
suggest that the density of plants may constrain the recovery of vegetation after drought, and
these constraints may determine lags that limit the capacity of the ecosystem to take advantage
of wet years after dry years.m2yr1) was linearly related to annual precipitation input (APPT; mm/yr) along
the experimental precipitation gradient (ANPP¼0.133APPTþ58.3; r2¼0.34, P , 0.01), and
this relationship was mostly accounted for by changes in the ANPP of grasses. Plant density
(D; no. individuals/mm2) was related to the precipitation received during the drought period
(D¼0.113APPTþ18; r2¼0.39, P , 0.05). The recovery of plants after irrigation was lower
for those plots that had experienced experimental drought the previous years relative to
controls, and the lags were proportional to the intensity of drought. Therefore, our results
suggest that the density of plants may constrain the recovery of vegetation after drought, and
these constraints may determine lags that limit the capacity of the ecosystem to take advantage
of wet years after dry years.¼0.133APPTþ58.3; r2¼0.34, P , 0.01), and
this relationship was mostly accounted for by changes in the ANPP of grasses. Plant density
(D; no. individuals/mm2) was related to the precipitation received during the drought period
(D¼0.113APPTþ18; r2¼0.39, P , 0.05). The recovery of plants after irrigation was lower
for those plots that had experienced experimental drought the previous years relative to
controls, and the lags were proportional to the intensity of drought. Therefore, our results
suggest that the density of plants may constrain the recovery of vegetation after drought, and
these constraints may determine lags that limit the capacity of the ecosystem to take advantage
of wet years after dry years.D; no. individuals/mm2) was related to the precipitation received during the drought period
(D¼0.113APPTþ18; r2¼0.39, P , 0.05). The recovery of plants after irrigation was lower
for those plots that had experienced experimental drought the previous years relative to
controls, and the lags were proportional to the intensity of drought. Therefore, our results
suggest that the density of plants may constrain the recovery of vegetation after drought, and
these constraints may determine lags that limit the capacity of the ecosystem to take advantage
of wet years after dry years.D¼0.113APPTþ18; r2¼0.39, P , 0.05). The recovery of plants after irrigation was lower
for those plots that had experienced experimental drought the previous years relative to
controls, and the lags were proportional to the intensity of drought. Therefore, our results
suggest that the density of plants may constrain the recovery of vegetation after drought, and
these constraints may determine lags that limit the capacity of the ecosystem to take advantage
of wet years after dry years.