The challenge of rangeland degradation in a temperate semiarid region of Argentina: The Caldenal

Abstract

The phytogeographical region known as the Caldenal comprises an area of approximately 10 million ha in the central temperate part of Argentina (35-408 S, 62-668 W). The original physiognomy of the vegetation consisted of a gramineous steppe with isolated shrubs and trees. Rangeland deterioration was initiated in the early-1900s with the introduction of livestock by the colonizing European ranchers. After a few decades of inappropriate use, the Caldenal proved to be a fragile environment. Major environmental impacts were: (a) The replacement of the most abundant palatable grasses Poa ligularis, Stipa clarazii, S. tenuis, Piptochaetium napostaense and Digitaria californica by low nutritive unpalatable grasses such as Stipa gynerioides, S. tenuissima, S. ambigua, S. bracychaeta and Elyonurus muticus; (b) The conversion of extensive areas dominated by grasses to a scrubland. There, frequent species are: Condalia microphylla, Lycium chilense, Prosopis alpataco, Larrea divaricata and Chuquiraga erinacea; (c) Depletion of plant cover resulting in incipient but increasing soil erosion in extensive areas. With the purpose of reversing this situation, the remit initiated 25 years ago was to develop management guidelines conducive to sustainable productivity while preserving the natural resources of the region. This work provides a comprehensive assessment of the impact of major stresses (drought, herbivory, fire) on grass and shrub responses, as well as more basic studies on the ecophysiology of these species. We have gained knowledge which is extremely useful to initiate rangeland utilization based on scientific information, facilitating increased sustainable rangeland productivity while preserving the natural resources.

A Global Assessment of Long-Term Greening and Browning Trends in Pasture Lands Using the GIMMS LAI3g Dataset

“…In southeastern Australia, the recent "Millennium Drought" [63] has driven significant vegetation productivity declines [64][65][66]. Other areas where we do not find significant and widespread degradation, but where degradation has been independently documented, include Africa [20] and South America [26,67].…”

Growth, blood metabolites and hormones in calves fed diets with different amounts of energy and protein during the pre- or post-weaning periods

“…Cow-calf operations are the most important activities in the temperate semi-arid rangeland region in Central Argentina known as the Caldenal (35 to 40° S, 62 to 66° W) (Fernández and Busso, 1999;Fernández, 2003;Fernández et al, 2009). Current stocking rates ranged from 5 to 7 ha cow -1 .…”

Water Use Efficiency and Net Production of Two Semi Arid Grasslands in Different Successional Stages

“…However, today their productivity does not fulfill the forage demand of ruminants, especially during the dry period of summer, widely oscillating in space and time according to plant species composition, herbivore pressure, human activities, successional stages as well as climatic conditions (Gatti et al, 2005;Migo, 2006; Ali-Shtayeh and Salahat, 2010). The abiotic profile of an area (i.e soil, climate, landscape) as well as external factors, such as fire and grazing may affect the productivity of an ecosystem (Gurevitch et al, 2006;Fernandez et al, 2009;Salis, 2010;Long et al, 2015). In addition, the productivity of grasslands is strongly associated with the successional stage of vegetation (Würtz and Annila, 2010).…”

“…Under drought conditions, natural selection favors plants with physiological adaptations that ensure the survival and growth based on the efficient use of available water (Heschel and Riginos, 2005). The low annual precipitation in the Mediterranean region combined with natural hazards of environmental degradation make an essential need to detect plants or successional stages which discourage the degradation and ensure environmental stability and high productivity (Bolle, 1995;Alcamo et al, 2007;Fernandez et al, 2009). According to Souza and coworkers (2005) there is a flexibility in plant capacity to respond to environmental changes taking into account positive or negative relationshi ps between physiological parameters and environmental conditions.…”

“…In Mediterranean ecosystems, the natural vegetation has been modified by the interactions of climate and human intervention and has developed coping mechanisms to further changes inhibiting a possible new environmental degradation (Fernandez et al, 2009;Păcurar et al, 2014;Zimmermann et al, 2014). Ecologists have developed many theories and models to describe those changes that succession induce (Clements, 1916;Odum, 1969;Connell and Slayer, 1977;Pickett et al, 1987;Meiners et al, 2015).…”