Prospects for Succession of Abandoned Pastures and Scrubs

UvA-DARE (Digital Academic Repository) Towards recovery of native dry forest in the Colombian Andes : a plantation experiment for ecological restoration Groenendijk, J.P. Publication date 2005 Link to publication Citation for published version (APA): Groenendijk, J. P. (2005). Towards recovery of native dry forest in the Colombian Andes : a plantation experiment for ecological restoration. Universiteit van Amsterdam, IBED. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:02 Oct 2021 Chapter 2. Vegetation patterns in a semi-arid dwarf forest zone: prospects for succession of abandoned pastures and scrubs J.P. Groenendijk and A.M. Cleef, accepted for publication in Vhytocoenologia Abstract A study on vegetation patterns in a semi-arid zone of the high plain of Bogota (Colombia), at 2600-2950 m.a.s.1., is presented, as a basis for a restoration experiment in the dry Andean dwarf forest zone. We aimed at explaining successional pathways by means of environment and disturbance history data. We laid out 101 relevees in grassland and shrubland types in different stages of recovery, and in relatively little disturbed endemic Condalia thomasiana dwarf forest. CCA was applied to relate species composition to environment, disturbance history and to the spatial configuration of the relevees. Abiotic factors mosdy related to species composition were soil nutrient richness and soil organic matter content. Invasion of grasslands by woody species is pioneered by Baccharis macrantha and Dodonaea viscosa. Dalea coerulea was the predominant woody species on truncated clayey soils, which will probably not support Condalia dwarf forest. This exploratory study will be of use in the set-up of future succession-based restoration experiments. 11 Chapter 2 Introduction Deforestation in the northern Andes is a major threat to all types of forest. Presently, most remnants of natural montane forest in this area are humid forests. Dry Andean forests are particularly threatened because die semi-arid areas are often densely populated, and have a long history of land use (Murphy & Lugo 1986). The population of the high plain of Bogota depends heavily on the surrounding mountain ranges for their drinking water. Parts of the aquifers originate in semi-arid areas, where inadequate land use has drastically reduced the cover of water retaining natural vegetation; extensive badlands are a common sight (Araque 1976; Thouret & Rovera 1983). Plantations with exotics (e.g., Acacia decurrens) have been established in the 1980s, virtually devoid of understory vegetation, and showing a poor recovery of ecosystem functions — soil tem perature and evapotransporation reduction - as compared to the native dwarf forest (Van der Hammen 1997, 1998). Remnants of dry montane dwarf forest were found in the semi-arid northern edge of the high plain of Bogota, in the Eastern Cordillera of the Colombian Andes. Van der Hammen (1997) described this forest as Xylosmo - Condalietum, or "Condalia forest". One of the characteristic treelets, Condalia thomasiana (Rhamnaceae), is a recently discov ered endemic of this particular zone (Fernandez-Alonso 1997). The Condalia forest reach es heights up to five meters, and has a highly diverse and dense understory of herbs, mosses and lichens, both terrestrial and epiphytic, with a high capacity of moisture reten tion. Very litde is known about the basic ecology of dry equatorial montane forest, or its recovery after disturbance. In spite of this, restoration efforts are needed, and the Cor- poración Autónoma Regional de Cundinamarca (CAR), which manages the (renewable) natural resources in the region, is now interested in this study. A start has been made with a succession-based plantation experiment in the area, involving application of mix tures of locally occurring species in different vegetation types in the study area, in coo peration with the CAR. The area has suffered from many kinds of disturbance. Cutting, grazing and agriculture have been practiced since pre-Columbian times (Van der Hammen 1998; Marchant et al. 2004; Vélez et al. 2003), and have had a great impact on vegetation pat terns and development (Adler et al. 2001; Backeus et al. 1994; Girardideiro el al. 1994; Hadar et al. 1999; Motzkin et al. 1999). Extensive grazing has favored the introduction of invasive herbs like Hypocboeris radicata, Antboxanthum odoratum, and Vennisetum clandestimim. Disturbance history assessment has been used extensively in vegetation studies; however, the aim was mosdy to assess changes in the cover of vegetation types (Kadmon & Harari-Kremer 1999; Verheyen et al. 1999). We used the individual disturbance history 12 Vegetation patterns and succession over the last ~60 years of each vegetation relevee point as a means to explain the pres ent-day species composition. The purpose of our study was to describe the vegetation types of the surroun dings of the Hacienda Susata, and to infer successional pathways from environmental variables and disturbance history. We assumed that vegetation development can be ex pressed in terms of structural development and diversity. In the present study, we chose not to consider heavily eroded sites, which would need engineering practices before any vegetation development could take place, and to limit our efforts to existing grasslands, scrubs and dwarf forest. Methods Study area The fieldwork area is at the edge of the high plain of Bogota, an intramontane basin in the Eastern Cordillera of Colombia (Figure 2.1). It concerns a part of the valley of the Checua River, an affluent of the Bogota River, situated within the community of Suesca, Cundinamarca (5° 07' N, 73° 50' W). The height above sea level of the study area is between 2550 and 2950 m. The zone receives about 700 mm of annual rainfall, generally concentrated in two short rainy periods. Evapotranspiration approximates 1050 mm annually, leading to a deficit of about 350 mm (Claro-Rizo 1995). The mean annual temperature is around 13°C (Van der Hammen 1998), which is below the minimum of the temperature range of "tropical dry forest" as set by Murphy & Lugo (1986). The area has a hilly terrain morphology. Most of the hills are built up by sand stones belonging to the Guadalupe Formation (Cretaceous). Northward, the pediment material probably is strongly weathered kaolinitic clay of the Balsillas Formation, of early Pliocene age (Helmens 1990). The entire area is covered by a volcanic ash cap, which var ies in thickness from less than 20 cm (upper slopes and summits) to 70 cm (pediments). Due to erosion, the hills are intersected by crevices, up to several meters depth, exposing either sandstone or kaolinitic clay. Soil formation in the ash layers has taken place under semi-arid conditions. Most sites show a natric B horizon primarily containing clay, organic material, and so dium. This illuviation horizon underlies a strongly leached E horizon, which in extreme conditions (on pediments) has formed a hardpan. An A horizon has hardly developed in the pediments. However, in the higher parts of the hills, where more humid conditions prevail, this horizon is often found. Slope deposits and fine alluvial caps have caused local variations in soil properties. 13 Chapter 2 73° 51' 73°50'W Figure 2.1. Locations of the vegetation relevees in the study area, indicated by circles. Since pre-Columbian times, the area has been affected by forest cutting, agri culture, and cattle grazing. With the growing population pressure in the 20n century, grazing and cultivation of oat and lentils increased. Recently, the intensity of agricultural land use in the area has reduced, and parts of the area were reforested witiS Acacia decurrens by the Corporation Autónoma Regional de Cundinamarca. Rekvees A total of 101 relevees were made between October 1999 and April 2001, following Braun-Blanquet (Mueller-Dombois & Ellenberg 1974). Selecting the relevee sites, we aimed at including a maximal variation in vegetation diversity and structure, avoiding planted vegetation and rocky substrates. Eighty-five of these had dimensions of 10 x 10 m, while the remaining 16 were rectangules of 10 x 15 m. The relevees of 10 x 15 m had no significantly different numbers of species than the ones of 10 x 10 m (/-test, />=0.641). In each relevee, the cover percentage of all vascular plant species was estim ated, and the vegetation structure was described by estimating the average height and cover of treelets, high shrubs, low shrubs, high herbs, low herbs, brvophytes, and lichens. 14 Vegetation patterns and succession Vouchers were deposited at the herbarium of the Instituto de Ciencias Naturales, Bogo ta, Colombia (COL). In each relevee the following geographical data were taken: GPS position, elev ation a.s.L, inclination, and exposure. Also, a bulk sample was taken of the upper five centimeters of mineral soil, consisting of five subsamples (from the four comers and the center) of the relevee. Soil sample analyses Soil analyses were carried out in the soil laboratory' of the Geographical Institute "Agustin Codazzi" (IGAC) in Bogota, Colombia. Samples were air-dried until constant weight.

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