Ecology and Society: Towards Integrated Analysis of Human Impacts on Forest Biodiversity: Lessons from Latin America

Study areas

The research was undertaken within a series of study areas located within highland Mexico and southern South America. Some general information about these locations is provided below. Further information is provided by Newton (2007).

Tropical montane forest
Neotropical montane forests are widely recognized as being of exceptional conservation importance, being a centre of high diversity and endemicity for many different groups of organisms. For example, some 45,000 plant species are thought to be found in neotropical highlands, nearly a fifth of all species known (Churchill et al. 1995). Cloud forests, being those montane forests in the humid tropics that are frequently covered in clouds or mist, have attracted particular conservation concern. Research focused on montane forests in three areas of Mexico (Fig. A1):

(i) Xalapa, Veracruz. The study area is situated between 1200 and 2000 m of altitude in the eastern Sierra Madre mountains, and is located between 19°13' and 19°41' N, and 96°51' and 97°01' W, with an area of 842 km². Total annual precipitation in this region varies between 1300 - 2200 mm, while mean annual temperature is between 12 – 18°C. Typically, there are three well-defined seasons, the relatively dry-cool season lasting from October-November to March, the dry-warm season during April and May, and the wet-warm season from June to September-October. Soils are andosols. Some important canopy tree species in the study area are Quercus xalapensis, Liquidambar styraciflua, Q. leiophylla and Carpinus caroliniana. Current land cover is a mosaic of cloud forest, secondary forest, coffee plantations, pastures, agricultural crops and human settlements. Most of the land is privately owned.

(ii) Highlands of Chiapas.
The Highlands of central Chiapas is a limestone massif, situated at 16°15' - 17°10' N, and 91°45' - 92°50' W, at altitudes of 1500 – 2840 m. The climate is temperate sub-humid, with a mean annual temperature of 13-17°C and mean annual rainfall typically in the range 1100-1600 m. Soils are a mixture of thin rendzinas, deeper humic acrisols and infertile chromic luvisols. Vegetation includes a number of highly diverse forest formations including seasonal pine and pine-oak forests, montane rain forests (800-2500 m elevation) and evergreen cloud forests (>2500 m). Oaks and pines are usually dominant in the forest canopy, including species such as the oaks Quercus laurina, Q. rugosa and Q. crassifolia, and the pines Pinus oocarpa, P. pseudostrobus and P. ayacahuite. The understorey is typically dominated by a diverse shrub community, including species such as Myrcia jurguensenii, Oreopanax xalapensis, Fuchsia spp. and Litsea glaucescens. Most inhabitants belong to Mayan ethnic groups, principally the Tzotzil, Tojolobal and Tzeltal. Land is communally owned. Traditional agriculture involves slash-and-burn (‘milpa’) involving the cultivation of corn, beans, and squash, producing a landscape mosaic of vegetation at different successional stages.

(iii) El Rincón Alto, Sierra Norte, Oaxaca. The study area is the Sierra Madre de Oaxaca Mountain Range, located in the north of the State of Oaxaca, between the parallels 17°18’ and 17°23’ N and the meridians 96°15’ and 96°21’ W. The area is part of the El Rincón Alto region and lies at 1850 + 150 m altitude, where tropical montane cloud forest is the primary vegetation. Topography is mountainous and the slopes are usually steep (15 - 64%). The climate is temperate-humid to subhumid, with mean annual temperature ranging between 20-22°C and mean precipitation around 1700 mm yr^-1, with a rainy season in summer and a dry season in winter. Soils lie on a bedrock of Mesozoic schist and are classified as entisols, inceptisols and dystrudepts. The land cover is a mosaic of primary forests, secondary forests of different ages after abandonment, and agricultural fields. Successional forests are dominated by the conifer Pinus chiapensis, which occurs in association with other species such as Clethra integerrima, Gaultheria acuminata, Liquidambar styraciflua and Phyllonoma laticuspis. Late-successional forests are dominated by broadleaved species such as Persea americana, Quercus spp., Rapanea spp., Ternstroemia hemsleyi and Quetzalia occidentalis. Human population density is relatively low compared to the other Mexican study areas. The area is inhabited by Zapotecs, a native Mexican ethnic group. Land tenure is communal.

South temperate rain forest
Temperate rain forests are distributed along the coastal mountain range of Chile and the main Andean range from 38°-56° S. Within this area, a number of different forest types may be differentiated, including the Valdivian evergreen forests that extend for 250 km from the Tolten River (40°50’ S) to south of the Llico River (41°30’ S). Notable elements of the flora include the long-lived conifers Monkey puzzle (Araucaria araucana) and alerce (Fitzroya cupressoides), with some trees of the latter species living for more than 3,620 years. Over the past 30 years, the Chilean forestry sector has become a driving force in the national economy, with forest exports increasing from approximately US$40 million in 1970 to US$2.2 billion in 2000. Other main threats to native forests have been the conversion to pasturelands, human-set fires, highgrading (selective felling), fuelwood cutting and other logging practices. Most land is privately owned.

Fig. A-1. Map illustrating the location of the principal study areas, namely Central Veracruz and the Highlands of Chiapas, Mexico, and Rio Maule-Cobquecura (Regions VII and VIII) and Los Muermos (Region X), Chile. Some field-based research was also undertaken in neighboring areas, including Sierra Norte, Oaxaca (Mexico), Chiloé Island (Region X, Chile), locations in Region IX (Chile) and neighboring areas of Argentina.

While research activities were distributed throughout southern Chile and adjacent locations in Argentina, investigations were particularly focused on the following three areas of Chile:

(i) Los Muermos area, Region X, Chile.
The study area corresponds to 503,287 ha located between 41°30· S, 73° W and 42°20· S, 74° W in southern Chile. The zone is characterised by a rainy temperate climate with an oceanic influence and without dry-periods, with a mean annual precipitation of around 2000 mm. The landscape is dominated by Valdivian temperate rain forests, surrounded by crops and pasture lands. Many of the remaining forest occur on acidic, shallow, poorly-drained soils referred to as ñadis, which are classified a gleysols. The forests are characterised by the presence of broad-leaved evergreen tree species such as Drimys winteri (Winteraceae), Nothofagus dombeyi (Nothofagaceae), Laurelia philipiana (Monimiaceae), Amomyrtus luma, Amomyrtus meli (both Myrtaceae), and Eucryphia cordifolia (Eucryphiaceae). In some sites, long-lived conifers such as Fitzroya cupressoides and Pilgerodendron uvifera (both Cupressaceae) can also be found. Anthropogenic disturbance has led to early successional stages of the forest being widespread, which are characterized by a high abundance of D. winteri and N. nitida. In some degraded sites, shrub species such as Berberis spp. (Berberidaceae), Baccharis spp. (Asteraceae), and Gaultheria spp. (Ericaceae) are abundant.

(ii) Chiloé Island, Region X, Chile. The study area comprises about 400 km² in the north-eastern corner of Chiloé Island, approximately 20 km north of the city of Ancud (41º50· S, 73º50· W). The landscape is characterized by an undulating topography with altitudes ranging from 50 to 100 m. Soils are generally thin (< 1 m), originating from Pleistocene moraine fields and glacial outwash plains, often with poor drainage. The prevailing climate is described as wet temperate with a strong oceanic influence. Meteorological records at Senda Darwin Biological Station (45º53· S, 73º40· W) indicate an annual rainfall of 2,090 mm and a mean annual temperature of 12ºC. Maximum monthly temperatures (January) are 16ºC and minimum monthly temperatures (July-August) are 5ºC. Rainfall occurs throughout the year, but 64% of the precipitation is concentrated from April to September. Lowland forests in the area have been logged since the early 1800s, but land clearing became more intense in the second half of the 20th century. The present-day rural landscape is characterized by a mosaic of remnant forest fragments and grazing pastures. The major forms of human impact on forests during the last century have been selective logging of valuable timber trees, widespread use of fire to clear land for pastures, and increasing forest fragmentation.

The forests are dominated by evergreen, broad-leaved trees, but included narrow-leaf conifers such as Saxegothaea conspicua and Podocarpus nubigena. Floristically, many forests belong to the North Patagonian forest type. Nothofagus nitida, Drimys winteri and Podocarpus nubigena are widespread. Some sites are more typical of a Valdivian rain forest with canopy dominants such as Eucryphia cordifolia, Laureliopsis philippiana and Nothofagus nitida. All forests have an understorey of Myrtaceae trees, often with abundant regeneration of tree seedlings and saplings and abundant cover of the native bamboo Chusquea quila, especially in tree-fall gaps.

(iii) Región del Maule, Chile. This study area covers around 578,164 ha in the Coastal Range of the Maule and Bío-Bío (VII and VIII) regions of south-central Chile, at latitudes between 35º and 36º30· S and longitudes between approximately 72º and 73º W. The climate is of Mediterranean type, with an average annual rainfall of 700-800 mm concentrated in the winter; the summers are dry from September to April, with high luminosity. The mean annual temperature is 14ºC. The two main types of soil are well-developed alfisoles, which have evolved from granite substrate; and thinner inceptisoles usually originating from marine sediment rock layers. The natural forest is mainly dominated by secondary forest of Nothofagus species (N. obliqua and N. glauca) (Fagaceae) and sclerophyllous species including Acacia caven (Mimosaceae), Quillaja saponaria (Rosaceae), and Maytenus boaria (Celastraceae). Also, many endangered tree species such as N. alessandri, Pitavia punctata (Rutaceae) and Gomortega keule (Gomortegaceae) occur in the study area. Anthropogenic disturbance is intense: in particular, the region suffered massive forest clearance in the middle of the 20th century for the cultivation of wheat crops, and non-sustainable extraction of firewood in more recent decades. The area therefore currently is characterized by a highly fragmented forest landscape.

Literature Cited