Chile: Restoration and Rehabilitation of Mixed Espinales in Central Chile

Project Stage:
Implementation

Start Date:
1989-01-15

End Date:
2008-01-15

Primary Causes of Degradation

Degradation Description

Over the past 465 years, the Central Valley has been rapidly and profoundly transformed in the pursuit of wheat and meat production, and the secano interior now generally carries vegetation types of low productivity and species richness used in a number of low-input, low-output farming and animal husbandry systems. These production systems, handicapped by depleted soils and unfavorable world market conditions, are now undergoing a deep crisis in many sectors. In their place, a green tide of industrial forestry plantations is unfurling, especially in the southern, more rain-fed slopes and portions of the region, proceeding in recent years at an average rate of about 120,000 ha/yr. Thus, what bio- and eco-diversity does survive in the secano interior, along with the sociocultural heritage related to traditional farming systems, is gravely threatened.

Espinales now occur on virtually all gentle slopes and plains where the original sclerophyllous vegetation (matorral) has been cleared, and where overgrazing is a severe and chronic disturbance. The introduction of exotic herbivores (cattle and European rabbits) also contributes to maintaining Chilean espinales in their present state. Soils in the area are badly leached, with pH 6.0-6.5 and very low nutrient levels. A long history of shallow cultivation, with animal traction only, and uncontrolled pastoral use have also led to severe compaction of most soils, some of which are therefore subject to periodic inundations in low-lying areas. Consequently, wafer infiltration is poor and rainfall is mostly ineffective for vegetation. Acacia caven forms a nearly monospecific shrub stratum, and most of the herbaceous understory consists of exotic annuals of little forage value.

A regional study of land occupation based on aerial photographs and field surveys was undertaken on a representative transect covering an area of 22,970 ha in the espinales in the subhumid zone. This study revealed that 70% of the study area was occupied by espinales, of varying levels of tree cover, more or less equally divided between the flatlands (llanos) and hillsides (lomas). An additional 4% of the study area was occupied by low shrublands known as romerillales after the dominant shrub Baccharis linearis (Ruiz et Pavon) (romerillo), a formation that is an indicator of overexploited and abandoned cereal fields. Only 2% of the espinales, primarily in the llanos, have been consistently managed with a sustainable silvopastoral approach that appears appropriate to the vegetation structure as well as being economically viable. It was also found that only in the llanos did there exist formations that readily lend themselves to silvicultural improvement. These correspond to espinales with 26­-50% tree cover and that occupy about 46% of the llanos in the transect, i.e., about 27% of the total of the study area. Only about 6.2% of the lomas in the study area were found to retain any recognizable remnants of the indigenous sclerophyllous matorral vegetation.

Reference Ecosystem Description

The region has various endemic plant species with affinities to the tropics, the Antarctic and the Andes. About 95% of the native plant species are Chilean endemic, including Gomortega keule, Pitavia punctata, Nothofagus alessandrii and Jubaea chilensis. The Chilean matorral has several threatened plant species; some endangered species are Adiantum gertrudis, Avellanita bustillosii and Beilschmiedia berteroana. Seven endemic birds are found in this ecoregion, including Chilean tinamous, moustached turcas, and Chilean mockingbirds. Other birds in the area include Andean condors, red-backed hawks, mountain parakeets, and long-tailed meadowlarks. Coastal species include Humbolt penguins, royal and Buller’s albatrosses, pink-footed shearwaters, and Inca terns. Mammals in the ecoregion include the yaca (a medium-sized mouse opossum), pichi (a small, hairy armadillo), South American and gray fox, kodok (a rare, housecat-sized wildcat), Andean cat, puma, and pudu (the smallest deer in the Western Hemisphere).It is futile to imagine a full restoration of the indigenous formations of which the pre-European structure and composition are largely unknown and which, in any case, could not support the existing human populations. Thus realistic restoration goals follow a post-Conquest model consisting of multilayered, species-enriched landscapes similar to what apparently occurred in the study area in the 16th-­19th centuries. Not only did the espinales contain several tree species other than espino, but these formations were integrated in a mosaic including intensively cultivated fields and vineyards, as well as a much more extensive number of woodland and matorral fragments, some of which at least were purposely protected as long-term timber and hunting reserves.

Project Goals

Based on many historical and first-hand accounts, the fertility and productivity of espinales of the region have declined steadily since the middle of the last century, and this no doubt has to do with the short-term mining of soils since that time. The ultimate goal of this project is the rehabilitation of these espinales, through increased soil fertility, to a situation of “mixed espinales” such as were common 100 years ago. This goal is also based on the existence of farmers who have chosen or have been convinced to manage their A. caven and other trees as a useful resource.

Monitoring

The project does not have a monitoring plan.

Stakeholders

The Chilean espinales provide the framework for subsistance-level agriculture and animal husbandry for approximately 300,000 people. Thus, ecological restoration or rehabilitation cannot be disassociated from agriculture and livestock management practices. On the contrary, it is only by incorporating economically beneficial changes in these human activities that increased biodiversity and other environmental desiderata can be achieved.

Description of Project Activities:
BNF Trees and Shrubs To study BNF in legume trees in espinal soils in conjunction with growth rates, a controlled field experiment was undertaken utilizing a local provenance of Acacia caven, along with Chamaecitysus proliferus ssp. palmensis (Tagasaste), Prosopis chilensis (Mol.) Stuntz. emend. Burkart, and P. alba Grisebach. Over 6 years, Chamaecitysus proliferus ssp. palmensis (Tagasaste) consistently showed growth rates several times greater than all other species used, attaining 3.5 m in height and 9.0 cm dbh. In addition, nodulation and the amount of N2 fixed by this remarkable species were an order of magnitude higher than in any other species. The amount of nitrogen accumulated per plant was also 10­-30 times greater in Tagasaste than in any of the other three NFLs tested (or the two nonfixing reference species). A. caven was shown to have one of the highest nodule efficiency values of any NFL on record. This may explain in part its remarkable success in disturbed lands in central Chile and throughout southern South America. In terms of their effects on soils through BNF, however, Tagasaste stands out remarkably. Tagasaste appears capable of contributing remarkably large quantities of N to espinal soils, i.e., in excess of 70 kg N/ha/yr in the second year, 129 kg N/ha/yr in the sixth year, and a total of 496 kg N/ha for the entire experimental period. The other three species tested fixed between 0 and 18 kg N/ha/yr in any single year and between 5 and 62 kg N/ha over 6 years. In a concurrent study on a nearby site at Cauquenes, 6-year-old Tagasaste was found to be capable of producing 4.4 Mg DW of edible, nutritious phytomass per year of immediate use for livestock of all kinds. At a coastal site, on sandy soils with 1200 mm mean annual rainfall, remarkable yields of 9 tons/ha/yr were recorded in the sixth year of growth. Annual Legumes In addition to studies on NFL trees and shrubs, annual legumes were also studied. From experiences recorded elsewhere, and especially in climatologically comparable areas in western Australia, annual Medicago species appeared highly promising for the secano interior. Moreover, at least nine different species are found naturalized throughout the area and showed very clear potential for selection and improvement as ecotypes and cultivars for each agroclimatological subregion. The most widespread, prolific, and polymorphic of these, Medicago polymorpha, was selected for particular attention. Starting in 1989, seeds of this species were field-collected in 59 sites along the natural aridity gradient running from La Serena (30°S, 150 mm mean annual precipitation) and Temuco (39°S, 1200 mm mean annual precipitation). These accessions were sown at Cauquenes with the main objective of characterizing their relative phenology and productivity under common garden conditions. Among many other results, precocity, i.e., time from emergence to first flowering, varied from 82 and 129 days, with a very tight relation existing between latitude of collecting site and precocity. This trait is of great importance for the long-term persistence of a stand or population of an annual medic under dry farming conditions, since it will often be the critical factor in determining its survival over the annual drought period. Thus the marked ecotypic variation in this trait could be put to use immediately in a selection and breeding program that has already yielded a number of commercial varieties that will soon be released for Chilean (and foreign) farmers. In parallel with the selection of M . polymorpha ecotypes, selection and improvement of rhizobial inoculants also began, with 33 isolates taken from soils of some of the 59 medic accessions. The two most efficient strains were isolated from collections made at Combarbala, Santa Dolores, and Chanaral alto, and these are all now commercially available from INIA. A similar effort was also initiated with subterranean clover and several additional species of Trifolium (T . michelianum Boiss. [Balansa clover] , T. incarnatum L. and T. resupinatum L. [ Persian clover] , and T. vesiculosum L.), incorporating a large number of acessions imported from Australia, Spain, and Portugal. Here again, the objective was to select precocious varieties showing high percentages of hard (i.e., dormant) seeds for use in specific edaphic conditions where M . polymorpha fails to prosper. After several years of field evaluation in a variety of sites, four Portugese varieties (Santiago de Cacem, Ponte de Ajuda, Sao Romao, and Argelino) and one Spanish variety (Areces) all showed higher DM production that the Australian var. Clare in common use in Chile today. In addition, a group of precocious varieties, including var. Areces and var. Santiago de Cacem, was identified for use in rotational systems with wheat, e.g., the so-called ley-farming system. The experimental inclusion of M. polymorpha in existing systems has already been shown to have a dramatic positive impact on organic matter content as well as N, P, and K content in espinal soils. These results are similar to those obtained in Australia and in Chile under more controlled conditions. Still more significant results can be expected from the selected cultivars that are just now entering into usage. More general rehabilitator effects are also apparent in relatively short periods from the use of both annual and woody perennial NFLs.

Ecological Outcomes Achieved

Eliminate existing threats to the ecosystem:
So far, experimental introductions of various NFLs has been accomplished, with the goal of eventually encouraging widespread land management practices that will ameliorate structural and biological soil conditions, facilitate the spontaneous reintroduction of native plants, microbes, and animals, and ultimately help improve overall productivity and stability of the espinales.

Factors limiting recovery of the ecosystem:
In the short-term, revegetation can be too costly for most small land-owners to afford, especially in view of the degraded state of most espinal soils and the ubiquitous presence of voracious rabbits and hares, both of which render tree and shrub planting a somewhat risky and costly affair. This problem may be ameliorated to some extent by utilizing alternative crop rotation systems designed to improve soil fertility while also increasing cashflow on medium-size farms.

Socio-Economic & Community Outcomes Achieved

Economic vitality and local livelihoods:
Evidence exists that revised management of NFLs in degraded espinales, including A. caven, will positively affect soil fertility, as well as pasture composition and productivity. In all subprograms of this project, efforts were made to identify techniques or organisms that could provide short-term benefits to landowners, especially in the form of wood, fuelwood, or forage for livestock.

Key Lessons Learned

Only a small proportion of the espinales (~25%) of the secano interior appear to lend themselves to a straightforward restoration process via revised sylvopastoral management and and the reintroduction of selected native trees and shrubs. All the rest of the study area has undergone such degradation and apparent overdomination (shall we say, parasitism ?) by Acacia caven that other responses appear necessary: either rehabilitation or else outright reallocation to new land-use systems bearing no direct relationship to historical formations such as the mixed espinales. This study confirms the hypothesis that NFLs can be found that are adapted to dryland conditions in the secano interior and that can have dramatic and apparently beneficial effects on soils in relatively short periods of time. The two annual legumes and Tagasaste had the most spectacular results, but it should be noted that this latter species also caused a decrease in soil pH and in available P. Its very rapid growth rate clearly causes profound changes in all five soil parameters considered and, no doubt, several others. Management is a critical issue in such a situation. Moreover, it is clear that 5 years is not an adequate period to allow confident predictions of long-term effects. At the same time, it can be imagined that in some restoration scenarios, after an initial period of Tagasaste cultivation used to promote a jump-start rehabilitation effect, it would be advisable to then eliminate this species altogether to make room for more balanced combinations of others, notably native species of trees and shrubs with fodder value or other important attributes.

As a complement to a purely ecological approach, we are convinced that the only hope for the degraded lands of the secano interior requires an economic rehabilitation and reinforcement, so that landowners can devote some portion of their resources to the long-term and costly process of ecological restoration and rehabilitation. Our original hypothesis concerning NFLs has clearly been confirmed to the first 10 years of our program ; over the next 10 years, we shall continue along these lines, while also paying greater attention to the opportunities and constraints for recent integration into global markets. This suggests we must encourage and facilitate ever-greater diversity of farm products as well as flexibility in terms of market fluctuations. Finally, we must accept that tourism will play an increasing role in rural economies and ecology in central Chile, as elsewhere. This is all the more reason to promote greater biodiversity through ecological restoration and rehabilitation.

Long-Term Management

In addition to the various rehabilitation tools we are developing, we are also actively pursuing more conventional R&D designed to develop new crops for the small portions of secano lands that can be equipped with irrigation through small-scale dams and canals. To wit, if high-quality grapes, strawberries, or other cash crops can be grown on, say, 5% of a farm lot permanently reallocated to such intensive activities, this will automatically release pressure on the rest of the landholding and facilitate long-term rehabilitation and restoration efforts. In those parts of the R&D program, it should also be emphasized that improved animal husbandry techniques and systems are being developed for the production of value-added products such as cow, sheep, and goat cheeses and organic grapes and other fruits, all of which are seriously underdeveloped products in central Chile. Water resources, especially rainfall and surface runoff, must also be better managed, so that we do not find ourselves perpetually confined to a secano or dryland farming paradigm.

Sources and Amounts of Funding

This project was facilitated by financial aid from the Franco-Chilean ECOS-Sud program and a CNRS-CONICYT Agreement of Cooperation.

Other Resources

Dr. Carlos Ovalle
Instituto de Investigaciones Agropecuarias (INIA)
CRI Quilamapu Experimental Station
Casilla 426, Chillan, Chile
covalle@quilamapu.inia.cl

Publications:

Peer Reviewed:
Aronson, J., C. Floret, Le Floc’h, E., Ovalle, C., Pontanier, R. (1993). “Restoration and Rehabilitation of Degraded Ecosystems in Arid and Semi-Arid Lands. I. A View from the South.” Restoration Ecology 1(1): 8-17.

Aronson, J., C. Floret, Le Floc’h, E., Ovalle, C., Pontanier, R. (1993). “Restoration and Rehabilitation of Degraded Ecosystems in Arid and Semi-Arid Lands. II. Case Studies in Southern Tunisia, Central Chile and Northern Cameroon.” Restoration Ecology 1(3): 168-187.

Ovalle, C., J. Aronson, A. del Pozo, and J. Avendano. (1990). The espinal: agroforestry systems of the Mediterranean-type climate region of Chile. Agroforestry Systems 10:213-239.

Ovalle, C., J. Aronson, A. del Pozo, and J. Avendano. (1999). “Restoration and Rehabilitation of Mixed Espinales in Central Chile: 10-Year Report and Appraisal.” Arid Soil Research & Rehabilitation 13(4): 369-381.

Ovalle, C., J. Aronson, A. del Pozo, and J. Avendano. (1996). “Land occupation patterns and vegetation structure in the anthropogenic savannas (espinales) of central Chile.” Forest Ecology and Management 86(1-3): 129-139.

Not Peer Reviewed:
http://www.worldwildlife.org/wildworld/profiles/terrestrial/nt/nt1201_full.html

Primary Contact

Organizational Contact