In spite of its designation as one of the world’s biodiversity “hot spots,” Ecuador has the highest deforestation rate in South America. Large tracts of its Andean forests have been exploited for timber and non-timber forest products and then converted into agricultural systems, primarily pastures for livestock production. These pastures decrease in productivity relatively quickly and must eventually be abandoned, leaving a denuded site overgrown with non-native grasses. Due to the region’s harsh environmental conditions, natural forest succession at these sites proceeds very slowly, making reforestation initiatives a growing necessity in recent years. At present, approximately 90% of these initiatives have employed fast growing non-native species–mainly pine (Pinus radiata and Pinus patula) and eucalyptus (Eucalyptus globulus and Eucalyptus saligna)–owing to a paucity of knowledge about the silvicultural characteristics and ecology of native species. This study was undertaken to evaluate the performance of a number of native species (both light demanding and shade tolerant) at three sites, representing different successional phases, and to test the efficacy of various methodologies in facilitating their establishment and long-term survival. Another facet of the study involved the plantation of native species within a Pinus patula monoculture to assess the potential for converting these plantations into more natural ecosystems. It is hoped that as a result of this study, restoration measures in Ecuador’s Andean forests will begin to rely more heavily on native species, and thereby improve the region’s overall biodiversity and resilience.
Andes of Ecuador, -1.831239, -78.18340599999999
Country or Territory:
Tropical Forest - Moist Broadleaf
Area being restored:
Primary Causes of DegradationAgriculture & Livestock, Deforestation, Invasive Species (native or non-native pests, pathogens or plants), Mining & Resource Extraction
The original forest cover of Ecuador is estimated to have covered 90% of the land area, corresponding to about 26 million hectares (Cabarle et al. 1989, Wunder 2000). In 2005, the remaining forest area was only 10.8 million hectares (FAO 2006a) of which only 3.0 million hectares can be classified as “production forests”–which are designated for the production and extraction of forest goods. Apart from deforestation in the pre-Columbian era, the main deforestation processes occurred in the last century, during the cocoa (1920s) and banana boom (1950-1965) in the coastal region (Costa), where large areas of forest were cleared for crop production. Another wave of deforestation was driven by the opening-up of the Oriente by road construction and oil exploitation in the 1970s. However, even today deforestation is continuing at an alarming rate. Over the last several years, Ecuador has faced the highest deforestation rate in South America (1.7 % area year-1) (FAO 2006a). The conversion of forest land into agricultural land–mainly pastures–is the primary cause of the deforestation, especially in the Andean Region.
For the San Francisco Valley, the area under investigation in this study, Paulsch et al. (2001) described the land-use dynamic typical of the montane Andean region. The first step is the exploitation of the primary forests. Following the exploitation, small-scale farmers transform the exploited forests into pastures for cattle ranching. In order to improve the productivity of the pastures, they plant non-native grasses, especially Setaria sphacelata and Melinis minutiflora. As a result of the regular burning of the pastures by the farmers, bracken fern (Pteridium arachnoideum) is invading the areas more and more. After several years, the decreasing productivity of the sites forces farmers to abandon the land and convert a new patch of forest into pastures (see also Hartig & Beck 2003). Due to the harsh environmental conditions on the abandoned sites and the lack of seed input, the natural succession is very slow, and it takes several decades until a forest is recovered. Consequently, there exists an increasing amount of unproductive land, especially over-used, degraded or abandoned pastures.
Reference Ecosystem Description
Originally, mountain forests covered most of the Ecuadorian Andean region. The Tropical Mountain Forest (TMF) is characterized by high richness and endemism of arboreal species. It is considered one of the most diverse ecosystems in the world and is named among the global “hot spots” of biodiversity (Brummitt & Lughadha 2003, Richter & Moreira 2005, Bussmann 2006). The diversity of this ecosystem is strongly correlated with elevation; diversity diminishes linearly with increasing altitude from 1.500 m a.s.l. to the forest top limit (Gentry 1995). JÁ¸rgensen & Leon (1999) registered for the Andean region 9865 vascular plant species, which represent 64.4% of the total number of species in Ecuador. Ulloa & JÁ¸rgensen (1995) found 334 trees species and 1.071 shrubs species in zones over 2.400 meters altitude, and Fehse et al. (1999) also registered more than 200 tree species over 2.500 m a.s.l.
The forests at the ECSF are rather specific (Bussmann 2006). They are characterized by a very high variation of small-scale vegetation units. This variation is related to vegetation zoning, steep slopes, and frequent natural landslide occurrences, which cause mosaics of micro-climatic conditions and, consequently, highly variable vegetation units (Becking 2004, Bussmann 2006). According to Neill (1999), the dominant vegetation types in the Andean region are: Lower montane rain forest (LMRF), Cloud forest (CF), North Ecuadorian grassland and quebrada vegetation, South Ecuadorian shrub vegetation, and Páramos.
– The first type is distributed between 700 – 2.500 m a.s.l. on the western and eastern Andean slopes. With nearly constant high atmospheric humidity, frequent fog- and mist-associated precipitation, and dense loads of vascular epiphytes as well as bryophytes on tree branches and trunks.
– The Cloud forest also called “upper montane rain forest” and “ceja andina” (in Spanish) occurs on the high Andean slopes from 2.500 m elevation to the upper limit of closed forest (3.400 – 3.600 m a.s.l.).
– The North Ecuadorian grassland and quebrada vegetation is present in the densely populated inter-Andean valleys, where the original vegetation was removed and replaced by agricultural and pastures.
– The South Ecuadorian shrub vegetation occurs in the inter-Andean valleys of south Ecuador between 2.000 – 3.000 m elevation.
– The Páramo vegetation is distributed through the Ecuadorian Andes from about 3.400 (in the North region) to 2.800 (in the South region).
To improve basic knowledge of the silvicultural properties of selected native tree species and evaluate their capability for reforestation of abandoned lands.
The project does not have a monitoring plan.
Description of Project Activities:
For the investigations conducted under this project, four different sites have been selected: 1. A pasture currently used for livestock rearing (hereafter: pasture) 2. A recently abandoned pasture covered by the weed Pteridium arachnoideum (hereafter: fern) 3. An abandoned pasture where a young secondary forest with bushy vegetation has become established (hereafter: shrub) 4. A 20-year-old pine (Pinus patula) plantation with a density of 400 individuals per hectare REFORESTATION EXPERIMENT Five native species were the primary focus of project activities. Two of these species (Alnus acuminata and Heliocarpus americanus) can be classified as light demanding species since they naturally regenerate (especially in clearances); while the other three species (Cedrela cf montana, Juglans neotropica and Tabebuia chrysantha) are defined as shade tolerant species due to their preference to regenerate under a closed canopy. These native species were planted in pure and mixed plantations. Because no seeds or seedlings of the selected species were available in the local nurseries, all plants for the reforestation had to be produced within the project, including the exploration of the seed sources, the collection and germination of the seeds, and the production of seedlings in containers. This work was done in the nursery of the project in cooperation with the Forest Engineering Career of Loja National University. The nursery is located in Loja city at 2.100 meters a.s.l and with a mean annual temperature of 15Â°C, which corresponds closely to the conditions at the designated planting sites. The seedlings for the plantations on the experimental sites were grown in 560 cm3 Polyethylene containers with a substrate that consisted of a mixture of highland black soil, bed sand, and forest humus at a relation of 2:1:1. The main field experiment was established as a Generalised Randomised Block Factorial Design (GRBFD) with three successional phases, two treatments (management variations), nine different tree species, and eight repetitions. In total 432 plots (10.8 x 10.8 m each) were established, 144 per successional phase. On each plot, 25 seedlings were planted in pure or mixed species sets with a spacing of 1.8 x 1.8 meters. The planting in the field was performed between May and September 2003 and was realized manually by means of metal bars, making a 30x30x30 cm hole. Immediately before planting, the herbaceous ground vegetation was manually eliminated on all plots. The shrubs and woody vegetation were not removed. Although forest plantations in the Ecuadorian Sierra have been generally established with a spacing of 3 x 3 m (van Voss et al. 2001), this study employed a spacing of 1.8 x 1.8 m. This allowed a reduction in the size of the plots, and thus facilitated more homogenous conditions within the plots. Furthermore, because canopy cover and canopy density are considered to be the most important factors for encouraging soil stabilization and vegetation recruitment in the understorey (Montagnini & Sancho, 1990, Fisher 1995, Jones et al. 2004), the closer spacing will result in earlier crown closure and intensified competition between the trees and the ground vegetation. It will also create more dynamic interactions among the different tree species in the mixed plots. To analyze the development of the plants and the influence of the environmental factors, five measurements were performed during the first 24 months: one immediately after planting and then every 6 months. Measurements included such indicators as survival, total height, root collar diameter, number of complete leaves, etc. Soil samples were also collected to facilitate an analysis of environmental variables influencing seedling development. In the collection of these samples, parameters such as altitude, mean inclination, rock cover, and physical soil characteristics were determined. HERBICIDE EXPERIMENT For a more detailed analysis of the competitive effects of ground vegetation on the early development of seedlings in abandoned pastures, three sites in the pasture area of the restoration experiment not used for reforestation were selected to establish three blocks of an herbicide experiment. Each plot has been planted with five seedlings of the two native forest species Tabebuia chrysantha and Cedrela montana in pure plantations with a spacing of 1 x 1 m. Consequently, each species is represented by 45 individuals per block and 135 in total. The treatments used in the experiment were: a. Control: removal of the ground vegetation one time before planting. b. Mechanical: manual removal before planting and every 4 months after planting. c. Chemical: removal of ground vegetation by means of a systemic herbicide, (Glifopac, 480 g per liter) 8 days before planting with no further treatment after planting. The seedlings were produced in the project nursery and planted in November 2004. For the analysis of the treatment effects, three measurements were performed during the first 12 months: one immediately after planting, and subsequent measurements 6 and 12 months after planting. ENRICHMENT EXPERIMENT To investigate the potential of native species for enrichment planting in exotic plantations, a further experiment was established in a 20-year-old Pinus patula plantation adjacent to the pasture site of the reforestation experiment (Aguirre et al. 2006). On eight plots, 648 individuals from nine native species were planted in subplots of 16 m2 each under two different environmental conditions: 4 plots under the closed canopy of the pine plantation and 4 plots in small gaps. The species tested were: Alnus acuminata, Cedrela montana, Cinchona officinalis, Cupania cf americana, Heliocarpus americanus, Isertia laevis, Myrica pubescens, Piptocoma discolor and Tabebuia chrysantha. The enrichment planting was done in May 2004. As with the other experiments, ground vegetation was removed manually before planting and every 4 months after planting over a period of 24 months. Four inventories of the seedlings were performed during the first 24 months: one immediately after planting to document the initial situation followed by further inventories after 6, 12 and 24 months.
Ecological Outcomes Achieved
Eliminate existing threats to the ecosystem:
REFORESTATION In surveys conducted to assess vegetative succession at the project sites, the number of seedlings increased according to the successional phase--from about 38.000 individuals per hectare in the pasture samples to more than 430.000 in the forest samples. In total the seedlings germinated in the greenhouse comprised 15 species from 15 genera and 10 families. The dominant families were Asteraceae and Melastomataceae, which contributed 40% of all species. Only two species (Brachyotum and Rubus) could be identified at all three sites of the reforestation experiment. As expected, the proportion of tree species was highest in the forest samples (98%). In the samples from the pasture, 18.000 individuals per hectare could be observed, but all of them were from only one species: H. americanus. Likewise, in the fern samples, 10.000 tree seedlings of Miconia sp. were produced, while in the shrub samples 37.000 trees per hectare, representing 5 different species, successfully germinated. In the forest samples, all seedlings were trees except those from Meriana sp., which contributed 2% of the total number of seedlings. It is surprising that despite the high number of Heliocarpus seedlings for the pasture and the forest, no individual could be found in the fern and the shrub samples. In order to compare the development of the reforestation with the process of natural succession, the structure, composition and dynamic of the tree and shrub communities was monitored on control plots at all sites. At the shrub site about 6.000 individuals were already present at the beginning of the observation period; at the fern site 2.000 individuals were present. At the shrub site, 64% of those (3752 individuals) were tree species and 35% (2136 individuals) shrubs. At the pasture site, almost no woody plants were present at the beginning; 96% of the individuals found were shrubs and 4% trees. Recruitment showed a decreasing gradient from the shrub to the pastures site. During the observation period of 24 months, more than 6000 individuals (2857 trees, 3725 shrubs) became established at the shrub site and more than 2000 at the fern site. Even at the pasture, a recruitment of 18 trees and 1788 shrubs could be registered. However, mortality was high at the pasture site compared to the fern site. At the end of the observation period, a total of 49 species from 44 genera and 29 families were present. The dominant three families were Asteraceae, Melastomataceae and Ericaceae, representing 34% of all species and 31% of the observed genera. At the shrub site, 90% of all species included were represented at the last measurement. At the fern site, 39% of the species were represented, and at the pasture only 35%. It is also important that at the shrub site, 47% of the species were trees compared to only 8% at the pasture and 16% at the fern site. However, mortality was also highest at this site which means that many individuals can establish but are not able to survive for a long period of time due to the strong competition. Myrsine andina was present at all sites, but at the shrub site, density was much higher than at both others sites. Nectandra sp. showed good recruitment (43 ind. Ha-1) at the fern and shrub sites but none at the pasture. No mortality appeared at either site, and the mean height of this species was already 168 cm at the fern site and 226 cm at the shrub site. Other species, such as Tabebuia chrysantha, Clethra revoluta, Hyeronima moritziana and Inga acreana, had densities of 87 ind. Ha-1 at the shrub site, but no new recruitment could be observed during the observation period. Piptocoma discolor could only establish at the pasture and fern sites but not at the shrub site. There were tree species, e.g. Alchornea pearcei and Myrica pubescens, that could establish for a short time but then suffered high mortality, leaving no seedlings at the end of the observation. There are huge differences in the survival rate among the species after 2 years of natural regeneration. Survival of the exotics species was 92%, and there was no significant difference between E. saligna and P. patula. However, the survival of the native shade tolerant T. chrysantha (94%) was even a bit higher. Surprisingly, the survival of the two light demanding species was significantly lower (57%) than that of all other species (except J. neotropica with 44%), and there was no significant difference between A. acuminata and H. americanus. On the predominant majority of the plots, more than 5 individuals survived the first two years. Even for the species with high mortality (e.g. H. americanus and J. neotropica), there were only a few plots where less than two individuals survived. If it is assumed that for a full stocking in the final stand, only 100 to 200 individuals per hectare are needed, the long-term survival of only one or two individuals per plot could be sufficient. Moreover, common experience has shown that the surviving trees will be the most vital and competitive individuals. In fact, for all species the maximum height was more than 45% higher than the mean height. For A. acuminata, T. chrysantha and P. patula, the mean height of the highest plants was more than 80% higher than the total mean height. These three species--T. chrysantha, E. saligna and P. patula--showed the highest rates of survival at all three sites. Survival of all species was lowest on the pasture, with the exception of A. acuminata and J. neotropica, which had the lowest survival on the fern and shrub sites respectively. Almost all species showed the best height results on the pasture site, even though the differences are very small for some species. Results for root collar diameter were similar to height, and only J. neotropica had the lowest RCD on the pasture. For all analysed parameters, significant differences between the pasture site and the two other sites could be found, while differences between the fern and shrub sites were not significant except for RCD. Survival of the light demanding and exotic species increased with advanced successional level of the site. Only for the shade tolerant species did conditions seem to be best at the fern site. In contrast to survival, the height of all three groups decreased with advanced succession. Surprisingly, survival of the shade tolerant species at the pasture was significantly higher than that of the light demanding species. The light demanding species had better survival at the shrub site compared to the pasture. However, this can be explained by the low survival of H. americanus on the pasture, which was significantly lower than that of A. acuminata. With regard to height and RCD, the exotics showed significantly higher means than the native species, and the shade tolerant species significantly lower than the light demanding species. At the pasture site, survival of all tree groups (except the exotics) was higher during the first six months of development compared to the other sites, but then started to rapidly decrease. At the fern and shrub site, survival was a bit lower in the first year but did not decrease tremendously during in the time that followed. Shade tolerant species were superior to the light demanding at all sites, although there were also huge differences among the various species. The growth characteristics among the successional phases did not differ significantly within the 1st year, but in the 2nd, the development at the pasture became increasingly better than at the other two sites. Comparing the growth performance of the different tree groups, the shade tolerant group showed the lowest growth. The light demanding H. americanus was at the same level as the shade tolerant species, but this was compensated for by the excellent growth of A. acuminata. The shade tolerant J. neotropica even showed a reduction in mean height during the first year because many seedlings experienced a die-back of the shoots. Within the exotics, it is notable that the growth of P. patula showed a strong increase after the first year. It is also remarkable that the development of the RCD of the light demanding species at the pasture site was better than that of the exotics at the fern and shrub sites. All species except the two exotics showed better rates of survival on the plots with treatment. However, this effect was significant only for the light demanding species A. acuminata and H. americanus. This is surprising, as they were expected to cope best with the pre-existing situation at the sites. While RCD of all species was positively influenced by the treatment, the effect on height varied among the species. C. montana, J. neotropica and E. saligna showed better heights on the untreated plots, while all other species grew better with treatment. Considering all species monitored by the project, neither rates of survival and nor height were significantly affected by the treatment. A similar conclusion could be drawn for RCD among all groups. Here, the differences between the treated and untreated plots also started to increase only after 12 months. The height of the shade tolerant trees was more or less stagnant during the first 18 months, independent of the treatment. With regard to pure vs. mixed plantations, no significant effects of mixture on seedling performance could be recognized after two years. These results are not astonishing, as the wide spacing (1.8 x 1.8 m) employed, together with the slow growth of the plants, means that interactions among the species are still very limited. However, mixture effects are expected with the closure of the crowns or when the roots start to interact directly or indirectly in the soil. That being said, significant differences between the pure and mixed plots could be identified for J. neotropica, where all parameters were worse in the mixture. A. acuminata had a significantly lower rate of survival on the pure plots, and C. montana was significantly higher on the mixture. A different effect of the successional phase on the pure and mixed plots could be identified for the survival of C. montana and H. americanus, where the pasture showed the lowest survival compared with the fern and shrub sites. Only for J. neotropica was survival at the fern site significantly different from that at the pasture and shrub sites. Also, height and RCD of J. neotropica and A. acuminata showed differences between sites, where the fern led to significant reductions in the mixed plots. In contrast to the pure plots, the treatment had a significant effect on all parameters of H. americanus on the mixed plots, with better survival and growth under the treatment. C. montana and J. neotropica showed better growth in height, and A. acuminata and J. neotropica in RCD, on the treated plots. MICRO-SITE CONDITIONS Although there exists no single parameter that is correlated with the growth of all species, rooting depth and the water capacity of the soil seem to be the major influencing factors in seedling performance. Soil texture is another important factor, as was inclination. Indeed, inclination had negative significant correlations with the growth of H. americanus, J. neotropica, T. chrysantha and E. saligna. Even though the altitude had a small variation range of only 340 m (between 1860 - 2200), it showed a negative correlation with the height of A. acuminata, C. montana, J. neotropica, and of both exotic species as well. Shrub cover showed a positive correlation with one shade tolerant species (T. chrysantha), while with A. acuminata it showed negative correlation. In addition, the growth of C. montana, J. neotropica, E. saligna and P. patula was correlated with the rooting depth of the soil, and J. neotropica showed a positive correlation with available water capacity (AWC). Positive correlations of pH were observed with both species exhibiting the best growth rates--A. acuminata and P. patula. HERBICIDE EXPERIMENT In the reforestation experiment, the manual removal of ground vegetation did not show a clear significant effect on the growth of the seedlings. A side experiment with C. montana and T. chrysantha seedlings was established to investigate the effects of a chemical treatment as an alternative to the manual clearing. This experiment also considered the biomass production of the ground vegetation and the seedlings. Similar to the reforestation experiment, C. montana had a higher mortality than T. chrysantha, but survival of the seedlings of both species was very high without a significant influence evident from the treatment. In contrast, height and RCD were significantly higher under the chemical treatment, while there was no difference between the control and the manual treatment. The analyses of the above- and belowground biomass of the ground vegetation and the seedlings conducted in this experiment allow much better insight into the competitive effects between these components. Both treatments led to a reduction in the biomass of the ground vegetation; however, the effect was predominantly concentrated on the aboveground biomass and the belowground biomass between 0 and 7.5 cm depth. Only in the manually treated T. chrysantha plots was the biomass reduction in the category 7.5 - 15 cm of depth higher than in the category 0 - 7.5 cm. In the chemically treated plots under this species, the aboveground biomass of the ground vegetation was also higher than in the manually treated plots. The roots of both tree species were able to penetrate the root tomentum of the ground vegetation and colonize deeper soil, even if their biomass proportion was still low. If the mean height of the plants is considered, the extension of the root system is astonishing. For instance, with a mean height of 51 cm on the chemical plots for T. chrysantha, the vertical extension of the roots was already about 80 cm, and the roots reached a depth of 60 cm. In contrast to the chemical treatment, the total biomass of the trees did not show a significant reaction to the manual treatment. It is interesting to note that of the total biomass on plots treated manually, the proportion of the tree biomass increased from 0.9% (control), 3.5% (manual) to 26.5% for T. chrysantha and 1.0%, 1.1% and 16.4% respectively for C. Montana--although the biomass of ground vegetation in the chemically treated plots was only slightly lower than in the manually treated. Besides the effects on the biomass, the different treatments also had an effect on the structure and floristic composition of the ground vegetation. After one year in the plots without chemical treatment, the floristic composition of the ground vegetation was still dominated by the pasture grasses Setaria sphacelata and Melinis minutiflora. On the chemical plots, however, S. sphacelata was eliminated and substituted by native grasses and other plants. In fact, vegetation height was reduced at the treated plots by >30% compared to the control plots, but coverage was reduced only at the T. chrysantha plots. Under C. Montana, coverage was even higher at the treated plots. ENRICHMENT EXPERIMENT Seedlings of native species were planted under the shelter and in the gaps of a pine plantation to assess the potential for transforming these plantations into more natural ecosystems. Two years after planting, the overall survival was not significantly different among the micro-sites. However, survival of the light demanding species was actually better under the closed canopy (except for A. acuminata and P. discolor), while that of the shade tolerant C. montana and C. officinalis was better in the gaps. C. officinalis experienced high mortality under both conditions. Interestingly, no mortality at all could be observed in the gaps within the first 6 months; while under the canopy, P. discolor, C. officinalis and H. americanus experienced losses of 11 %, 19 %, and 3 % respectively during this time. Mortality continued constantly until the end of the observation period, but survival remained relatively stable in the gaps (except for I. laevis). When the survival in this enrichment planting is compared to that in the reforestation experiment, the situation in the gaps was superior for the corresponding seedlings at all three successional sites. With regard to the development of the height and root collar diameter of the species, it is obvious that both parameters were better in the gaps. A. acuminata and P. discolor, in particular, showed excellent growth and reached mean heights of 234 cm and 165 cm respectively, which is more than 2.5 times that of the plants under the canopy and 1.6 times of those in the reforestation experiment. Looking at the height/RCD ratio, it is interesting that many species had higher values under the canopy. Only C. cf americana and C. montana had clearly higher values in the gap. These species had a very low increment in RCD compared to the canopy. T. chrysantha also exhibited a slightly increased ratio under the canopy, but its RCD increment of 1.1 cm was similar to that of the light demanding species. All species except C. cf americana and C. montana already stand more than 1 meter in height, and the talles trees are more than 3 m tall. For most species, the relation between the height in the gap and under the canopy increased; only for I. laevis and T. chrysantha did the relation decreased slightly. In addition, the variation of the growth parameters under the canopy was clearly lower compared to the gap. Thus, under the canopy, the growth was more homogenous. In addition to the growth parameters, the surviving seedlings of all species also showed a better health status in the gap. This is not only true for the light demanding species, but also for the shade tolerant species. The shade tolerant C. montana, for example, obviously preferred the gap condition because under the canopy 25% of the plants were of poor health.
Factors limiting recovery of the ecosystem:
The results obtained for the native species show that the micro-site conditions apparently play a fundamental role in the performance of a given species. A. acuminata has the reputation of having a strong ability to adapt to and grow well under a wide range of environmental conditions (Dunn et al. 1990, Lamprecht 1990, Añazco 1996, Fournier 2002). However, in this study, a survival of only 58% was observed. This low rate of survival was related to the water availability and soil compaction because at a humid site without soil compaction near Oyacachi, Ecuador at 2000 m elevation, Fehse et al. (2002) registered very high colonization rates of A. acuminata (>20.000 individuals per hectare) within the first two years after a natural landslide. Apart from the relatively high mortality, though, the surviving seedlings of A. acuminata in this study exhibited excellent performance. They showed the best growth and were only surpassed by the seedlings of P. patula. The light demanding species H. americanus was expected to exhibit good adaptability to conditions at the reforestation plots, especially on the pasture, since in reforestations on abandoned land in the Amazonian region of Ecuador, this species showed high survival rates (90%) and excellent growth in height (1 meter per year) (Davidson et al. 1998). However, those sites were at a lower altitude (1300 m a.s.l.) and exhibited more humidity (3000 mm/year) and warmer temperatures (mean temperature 22Â°C). In this study, the behaviour of H. americanus was disappointing, as its survival rate was only 53% and its growth performance was low. It is concluded that this species has clear preferences for certain micro-sites (niches). For instance, in the three plots with drainage problems, the seedlings experienced a mortality of 100%. Nitrogen availability could also help explain the bad performance, as Rhoades et al. (1998) report that the nitrogen availability within pastures with Setaria sphacelata was reduced by 20% compared to the soil of natural montane forest. This conclusion is supported by the fact that in the current study, at one plot with a comparatively good nutritional status (due to natural fertilization by cattle dung), the total mean in height was 187 meters, which was quite similar to the growth registered in the natural forest of the ECSF close to a creek where Cabrera (pers. comm.) registered a height growth of 2 meters per year. These findings are also in line with the common experience of the local foresters that H. americanus has a preference for sites with good drainage and constant humidity. Surprisingly, the shade tolerant native species T. chrysantha showed the best survival (94%) of all species. This demonstrates its ability to establish in degraded areas under very heterogeneous conditions. Otsamo et al. (1997) also reported good survival rates in plantations with T. chrysantha in Indonesia at sites with a precipitation of 2128 mm per year and a dry period of 5 months. The high survival of this species may be explained by the presence of arbuscular mycorrhizas in the roots. A corresponding sampling of the seedlings at the pasture site revealed that all roots of T. chrysantha contained abundant arbuscular mycorrhizas (Huag pers. comm.). This is a result of the fact that for the production of the seedlings in the nursery, a substrate was used with soil from the natural forest containing ample mycorrhizas, which inoculated the roots of the seedlings (Kottke et al. in press). However, in contrast to the excellent survival, the growth of the seedlings was quite modest, which is also in line with the results of Otsamo. This modest growth performance is likely due to strong root competition with the ground vegetation because in the herbicide experiment, the chemical elimination of the root competition improved the growth of C. montana and T. chrysantha significantly. The behaviour of J. neotropica was characterized by its minimal survival and poor growth. This stands in contrast with the good development of the species reported from plantations in New Zealand using seed provenient from Ecuador (National Research Council 1989). In fact, in New Zealand, the trees exhibited a growth rate of up to 1.5 m/year (at 10 years of age the plants were 10 meters tall). For the species J. piriformis, Pedraza & Williams-Linera (2003) reported survival rates of 76% on abandoned pastures in Veracruz, Mexico. Due to the excellent behaviour of Juglans in their observations, and despite its poor performance here, Juglans is still recommended for rehabilitation of degraded soil. The poor performance of the seedlings at the ECSF could be related to the superficial depth of soil and the deficient drainage properties. Indeed, from studies in Costa Rica it is known that Juglans requires optimal soil and water availability for good performance (CATIE 1997, Nieto & Rodriguez 2002b). The opposed trends of increasing survival but decreasing growth between the pasture site and the fern and the shrub sites in this study can be explained by the different floristic composition of the vegetation at the sites (Flick 2003) on the one hand, and the differences in the light exposure and humidity conditions in soil and air on the other. At the pasture, competition was predominantly determined by the Setaria grass. However, due to the removal of ground vegetation before planting, competition during the observation period was primarily dominated by the belowground effects. Consequently, the low survival of A. acuminata, H. americanus and J. neotropica at the pasture site may be related to reduced soil humidity resulting from compaction due to recent grazing. Another critical soil factor may have been the nitrogen availability. As already mentioned, Rhoades et al. (1998) reported that the nitrogen availability in pastures with Setaria sphacelata was reduced by 20% compared to that in the natural forest. This fact would also explain the strong performance of the N-fixing A. acuminata in this study. The finding that surviving seedlings at the pasture site showed better growth than those at the fern and shrub sites can be explained by the higher solar radiation at the open pasture compared to both other sites. As is known from many studies, plants are able to adapt their photosynthesis to high radiation (e.g. Lichtenthaler 1996, Larcher 2003). Thus, immediately after planting, photoinhibition may even have contributed to the higher mortality at the pasture, but the surviving seedlings seem to have subsequently adapted to the high insolation. At the fern site, the lower growth rate of the seedlings could be related to the direct competitive effect of the invasive Pteridium (in addition to the aforementioned shade effect) (Shepherd 1986, Hartig & Beck 2003, Roos 2004, Rodriguez Da Silva & Da Silva Matos 2006). Its competitive strength results from deep rhizomes that reach depths of one meter and enable the plant to survive under adverse conditions. Furthermore, this dense network of roots releases allelopathic substances that inhibit the natural regeneration and growth of native forest species (Ferguson et al. 2005, Rodriguez Da Silva & Da Silva Matos 2006, Slocum et al. 2006).
Socio-Economic & Community Outcomes Achieved
Economic vitality and local livelihoods:
The Andean tropical mountain forests are of great global, regional, and local importance for the provision of environmental services (Sarmiento 2001, Lojan 2003, Bussmann 2006). They capture and store rainfall and humidity, maintain water quality, reduce erosion, and provide protection against landslides, avalanches, and floods (Sarmiento 2001, Lojan 2003). In developing countries like Ecuador, the loss of land productivity is particularly disastrous because forestry and agricultural land use is one of the main generators of income, especially in rural areas.
Key Lessons Learned
The afforestation practice in the Andes of Ecuador is still almost completely based on the use of exotic species (e.g. Pinus patula, P. radiata, Eucalyptus globulus, E. saligna and Cupressus lusitanica), while native species are merely used for agroforestry or at an experimental scale. The widespread use of exotic tree species is mainly a result of extensive knowledge about their silvicultural characteristics, the fast growth rates they exhibit, and their industrial utility. However, these exotic species have also been favored because of a lack of corresponding knowledge about the native species. The study described herein allows a direct comparison which will enable practitioners to balance the ecological, economic and socio-economic advantages and disadvantages of both groups in the long run.
In the reforestation experiment conducted as part of the project, the performance of the exotics during the first two years after plantation was better than that of most natives. That being said, T. chrysantha exhibited a higher rate of survival than both exotics, and the growth of A. acuminata was significantly superior to that of E. saligna and only slightly inferior to that of P. patula. These observations suggest that natives are able to compete with exotic species when species-specific characteristics and appropriate site conditions are carefully considered. For Ecuador, with its tremendous diversity of 2736 native tree species (JÁ¸rgensen & León Yanez 1999), and more than 200 species in areas above 2500 m a.s.l. (Fehse et al. 1999), it can be assumed that species for all types of conditions are available. However, there is a huge need for more experiences and investigations.
Sources and Amounts of Funding
Financial support for this project was provided by the Deutsche Forschungsgemeinschaft (DFG).
Mendoza, Nikolay Aguirre. Silvicultural contributions to the reforestation with native species in the tropical mountain rainforest region of south Ecuador. Doctoral Dissertation. Munich: Technischen UniversitÁ¤t MÁ¼nchen, 2007.