Differences in plant cover and species composition of semiarid grassland communities of central Mexico and its effects on net ecosystem exchange 1División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica A. C. (IPICYT), San Luís Potosí, 78216, Mexico
12 Jul 2013
2Science Department, National Ecological Observatory Network, Boulder, CO 80301, USA
3Institute of Alpine and Arctic Research, University of Colorado, Boulder, CO 80303, USA
4Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Km. 10 Carr. Ojuelos-Lagos de Moreno, Jalisco, Mexico
Received: 16 October 2012 – Published in Biogeosciences Discuss.: 04 December 2012 Abstract. Changes in land use across the semiarid grasslands of northern Mexico have
driven a decline of plant cover and alteration of plant species composition.
A number of different plant communities have resulted from these changes.
Their implications, however, on the carbon (C) cycle and regional carbon
balance are still poorly understood. Here, we examined the effects of plant
cover loss and changes in species composition on net ecosystem CO2
exchange (NEE) and their biotic and abiotic controls. NEE was measured in five
representative plant community types within a semiarid grassland by
temporarily enclosing the entire aboveground ecosystem using a chamber
method (i.e., geodesic dome). Sites included an oat crop (crop), a moderately
grazed grassland (moderate grazing), a 28 yr-old grazing exclosure (exclosure), an overgrazed site
with low perennial grass cover (overgrazed), and an overgrazed site presenting shrub
encroachment (shrub encroachment). For natural vegetation, rates of standardized daytime NEE for
sites with a high plant cover (exclosure and moderate grazing) were similar
(P > 0.05) as
compared to sites with low plant cover (overgrazed and shrub encroachment). However, yearly total
nighttime NEE (carbon loss) was more than double (P < 0.05) for sites
with high plant cover compared to sites with low cover, resulting to slight
C sinks for the low plant cover sites, and neutral or sources for the high
plant cover sites as accounted by daytime and nighttime NEE annual balance.
Differences in plant cover and its associated biomass defined the
sensitivity to environmental controls. Thus, daytime NEE in low plant cover
sites reached light compensation points at lower photosynthetic photon flux
density than those from high plant cover sites. Differences in species
composition did not influence NEE rates even though there were transient or
permanent changes in C3 vs. C4 functional groups. Our results allowed the
detection of the large variability and contribution of different plant
communities to regional C balance in patchy landscapes. Identification of the
role of landscape patches in the regional C balance as either sinks or sources
may provide tools allowing land use management strategies that could favor C
uptake in patchy landscapes.
Revised: 01 June 2013 – Accepted: 11 June 2013 – Published: 12 July 2013
Citation: Delgado-Balbuena, J., Arredondo, J. T., Loescher, H. W., Huber-Sannwald, E., Chavez-Aguilar, G., Luna-Luna, M., and Barretero-Hernandez, R.: Differences in plant cover and species composition of semiarid grassland communities of central Mexico and its effects on net ecosystem exchange, Biogeosciences, 10, 4673-4690, doi:10.5194/bg-10-4673-2013, 2013.