Production and turnover rates of shallow fine roots in rangelands of the Patagonian Monte, Argentina |
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Authors: | Cecilia Larreguy Analía L Carrera Mónica B Bertiller |
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Institution: | (1) Centro Nacional Patag?nico-CENPAT (CONICET), Boulevard Brown 2915, U9120ACV Puerto Madryn, Chubut, Argentina;(2) Universidad Nacional de la Patagonia San Juan Bosco, Boulevard Brown 3700, U9120ACV Puerto Madryn, Chubut, Argentina |
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Abstract: | Selective sheep grazing in arid rangelands induces a decrease in total cover and grass cover and an increase in the dominance
of shrubs. Both life forms differ in aboveground and belowground traits. We hypothesized that grazing disturbance leads to
the replacement of grass by shrub fine roots in the upper soil, and this is reflected in changes in the seasonal dynamics
of shallow fine roots at the community level. In two sites representative of non-grazed and grazed vegetation states in the
Patagonian Monte, we assessed the canopy structure, and the fine root biomass, N concentration, production, and turnover during
two consecutive years. The non-grazed site exhibited higher total, grass, and shrub cover than the grazed site. The grazed
site had larger or equal fine root biomass than the non-grazed site except for late spring of the second year. This could
be associated with the ability of shrubs to develop dimorphic-root systems occupying the soil freed by grasses at the grazed
site, and with the larger contribution of grass than shrub fine roots in relation to an extraordinary precipitation event
at the non-grazed site. This was consistent with the N concentration in fine roots. Fine root production was positively correlated
to temperature at the grazed site and with precipitation at the non-grazed site. Fine root turnover did not differ between
sites. Our results indicate that grazing leads to a shifting in the seasonality and main climatic controls of fine root production,
while fine root turnover is mostly affected by changes in soil water conditions. |
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