Chapter 9
Are Soil Carbon Stocks in Mountain
Grasslands Compromised by Land-Use
Changes?
Jordi Garcia-Pausas, Joan Romanyà, Francesc Montané, Ana I. Rios,
Marc Taull, Pere Rovira and Pere Casals
Abstract Mountain grasslands are generally rich in soil organic C, but the typical
high spatial variability of mountain environments, together with the different
management systems, makes their soil C content particularly variable. Socioeconomic changes of the past decades have caused a progressive abandonment of
the traditional use for grazing of some areas, while grazing pressure at easily
accessible grasslands have increased. Here, we analyse the effect of these land-use
changes on the factors regulating the soil C accumulation and stocks. Overgrazing
generally leads to a reduction above- and below-ground litter inputs and a decrease
in soil C stocks, affecting some soil physicochemical and biological properties.
Additionally, the labile C inputs coming from animal faeces may accelerate the
mineralisation of organic matter. Grazing abandonment causes a reduction of
aboveground productivity, but the lack of consumption causes a short-term accumulation of organic matter. Its effect on belowground biomass and productivity is
less clear. At longer term, grazing abandonment causes a change in the plant
community composition, having the shrub encroachment the strongest effect on C
storage. The low biochemical quality of shrub litter delays its decomposition and
allows higher organic matter accumulation in the topsoil. But the effect of shrub
proliferation at the deeper soil is less clear. The low root turnover of shrubs
compared to grasses may reduce the C inputs to the soil. But, at the same time, the
reduction of the root exudates may also reduce the microbial activity and the
organic matter mineralisation.
J. Garcia-Pausas (&) Á F. Montané Á A.I. Rios Á M. Taull Á P. Rovira Á P. Casals
Forest Sciences Centre of Catalonia, CEMFOR-CTFC, Ctra de St. Llorenç de Morunys,
km 2, 25280 Solsona, Catalonia, Spain
e-mail: jordi.gpausas@gmail.com
J. Romanyà
Department of Biology, Health and Environment, Universitat de Barcelona,
Joan XXIII s/n, 08028 Barcelona, Catalonia, Spain
F. Montané
School of Natural Resources and the Environment,
University of Arizona, Tucson, AZ 85721, USA
© The Author(s) 2017
J. Catalan et al. (eds.), High Mountain Conservation in a Changing World,
Advances in Global Change Research 62, DOI 10.1007/978-3-319-55982-7_9
207
Are Soil Carbon Stocks in Mountain
Grasslands Compromised by Land-Use
Changes?
Jordi Garcia-Pausas, Joan Romanyà, Francesc Montané, Ana I. Rios,
Marc Taull, Pere Rovira and Pere Casals
Abstract Mountain grasslands are generally rich in soil organic C, but the typical
high spatial variability of mountain environments, together with the different
management systems, makes their soil C content particularly variable. Socioeconomic changes of the past decades have caused a progressive abandonment of
the traditional use for grazing of some areas, while grazing pressure at easily
accessible grasslands have increased. Here, we analyse the effect of these land-use
changes on the factors regulating the soil C accumulation and stocks. Overgrazing
generally leads to a reduction above- and below-ground litter inputs and a decrease
in soil C stocks, affecting some soil physicochemical and biological properties.
Additionally, the labile C inputs coming from animal faeces may accelerate the
mineralisation of organic matter. Grazing abandonment causes a reduction of
aboveground productivity, but the lack of consumption causes a short-term accumulation of organic matter. Its effect on belowground biomass and productivity is
less clear. At longer term, grazing abandonment causes a change in the plant
community composition, having the shrub encroachment the strongest effect on C
storage. The low biochemical quality of shrub litter delays its decomposition and
allows higher organic matter accumulation in the topsoil. But the effect of shrub
proliferation at the deeper soil is less clear. The low root turnover of shrubs
compared to grasses may reduce the C inputs to the soil. But, at the same time, the
reduction of the root exudates may also reduce the microbial activity and the
organic matter mineralisation.
J. Garcia-Pausas (&) Á F. Montané Á A.I. Rios Á M. Taull Á P. Rovira Á P. Casals
Forest Sciences Centre of Catalonia, CEMFOR-CTFC, Ctra de St. Llorenç de Morunys,
km 2, 25280 Solsona, Catalonia, Spain
e-mail: jordi.gpausas@gmail.com
J. Romanyà
Department of Biology, Health and Environment, Universitat de Barcelona,
Joan XXIII s/n, 08028 Barcelona, Catalonia, Spain
F. Montané
School of Natural Resources and the Environment,
University of Arizona, Tucson, AZ 85721, USA
© The Author(s) 2017
J. Catalan et al. (eds.), High Mountain Conservation in a Changing World,
Advances in Global Change Research 62, DOI 10.1007/978-3-319-55982-7_9
207