Soil conservation in Polylepis mountain forests of Central Argentina: Is livestock reducing our natural capital?

Abstract

Mountain forests and their soils provide ecological services such as maintenance of biodiversity, provision of clean water, carbon capture and forage for livestock rearing, which is one of the principal economic activities in mountain areas. However, surprisingly little is known about livestock impact in South American mountain forest soils. With the aim of understanding how livestock and topography influence patterns of forest cover, soil compaction, soil loss and soil chemical properties, we analysed these parameters in 100 Polylepis australis woodland plots situated in the humid subtropical mountains of Central Argentina. We used distance from the nearest ranch as an objective index of historical livestock impact and measured standard topographic variables. Our main results reveal that distance from ranch in all cases partly explains tree canopy cover, soil loss, soil compaction and soil chemical properties; suggesting a strong negative effect of livestock. Intermediate altitudes had more tree canopy cover, while landscape roughness -a measure of the variability in slope inclination and aspect -was negatively associated to soil impedance and acidity, and positively associated to soil organic matter content. Finally, flatter areas were more acid. We conclude that livestock has had a substantial influence on forest soil degradation in the Mountains of Central Argentina and possibly other similar South American mountains. Soil degradation should be incorporated into decision making when considering long-term forest sustainability, or when taking into account retaining livestock for biodiversity conservation reasons. Where soil loss and degradation are ongoing, we recommend drastic reductions in livestock density.

Genetic structure and diversity ofPolylepis australis(Rosaceae) tree populations from central Argentina: Implications for forest conservation

“…Although at present these populations show low density, they have preserved relatively high levels of genetic diversity, since the fragmentation may have occurred quite recently. Several studies in the mountains of central Argentina suggest that low population densities in these basins are the result of human activity enhanced by the proximity to roads that provide easy access to the development of livestock (CINGOLANI et al, 2008;2004;RENISON et al, 2011RENISON et al, , 2010. The populations of the second group (Condorito, Molles, and Santa Clara) cluster together.…”

“…We chose five river basins -which in RENISON et al (2006) were categorized according to the different land use histories and consequent varying levels of fragmentation and conservation -from the least to the most preserved as (1) Mina Clavero, (2) Yuspe, (3) Condorito, (4) Los Molles and (5) Santa Clara river basins -with Polylepis cover of 1, 3, 6, 15 and 15 %, respectively. Further descriptions and historical land use information may be found in RENISON et al (2011;2010;.…”

“…Forests were destroyed on a large scale during centuries of recurrent burning, which was used to claim agricultural land. At present, nearly all Polylepis stands throughout South America are still used for firewood, timber or as pasture land, which substantially affects their structure, species composition, regeneration and soil protection capacity (RENISON et al, 2011;2010;TORRES et al, 2008;HENSEN, 2002;KESSLER and DRIESCH, 1993). The genus Polylepis (Rosaceae) includes about 28 wind-pollinated species of short to tall shrubs and trees, which are distributed from Venezuela to Argentina (KESSLER and SCHMIDT-LEBUHN, 2006;SCHMIDT-LEBUHN et al, 2006a).…”

Soil “Ecosystem” Services and Natural Capital: Critical Appraisal of Research on Uncertain Ground

“…Indeed, it is clear from that diagram that the fulfillment of a function by a soil will, in general, affect the extent to which it is capable of fulfilling others. For example, on a given piece of land, a farmer's decision to change the land use or its management, e.g., by planting a forest instead of having a field or a pasture, on which livestock feeds (Renison et al, 2010), or by switching from industrial agricultural practices to a form of conservation agriculture or organic farming, will likely have a marked effect on the percolation of water down the soil profile, which in turn will affect the recharge of groundwater and/or the filtration of chemicals. Another, more extreme, example, is if a soil is covered with an impervious surface, as in a parking lot.…”

Effects of Recreational Traffic on Alpine Plant Communities in the Northern Canadian Rockies

“…Differences between the current and past grazing pressure, even where vegetation is adapted to herbivory, can affect the vulnerability of ecosystems to grazing (Cingolani et al, 2008;Renison et al, 2010). For example, reductions in productivity due to a greater herbivore biomass per unit area can occur with intensive management of domestic livestock, compared to unmanaged systems (Oesterheld et al, 1992;Cingolani et al, 2008).…”