Translator Disclaimer
1 May 2011 Status of Native Woody Species Diversity and Soil Characteristics in an Exclosure and in Plantations of Eucalyptus globulus and Cupressus lusitanica in Northern Ethiopia
Author Affiliations +
Abstract

Exclusion of grazing animals and tree plantations are 2 methods that have been used for restoration of degraded lands in tropical semiarid areas. These 2 options can foster secondary forest succession by improving soil conditions, attracting seed-dispersal agents, and modifying microclimate for understory growth. We compared native woody plant diversity and soil chemical and physical attributes under exclosure and on Eucalyptus globulus (EGP) and Cupressus lusitanica (CLP) plantations. Vegetation data were collected by an inventory of stands with circular plots of 5.64 m radius, and soil samples were collected from the 4 corners and center of 20 × 20 m plots. As a result, 15 native woody plant species belonging to 13 families were recorded. Importance value index (IVI), Shannon-Wiener, Simpson's diversity, and species richness were higher in the exclosure, followed by EGP and CLP. Contents of soil organic carbon and total nitrogen showed significance difference and were highest in the exclosure, followed by CLP, EGP, and grazing land. Although the difference was not significant, an increasing trend was observed for cation exchange capacity and K . Bulk density was highest on the grazing land, followed by EGP, CLP, and exclosure. Our results suggest that degraded land reclamation can be achieved with plantation of rapidly growing tree species as well as exclosure. However, native woody species diversity and improved soil attributes are better achieved with exclosure. Exclosures can be established interspersed strategically with single- or mixed-species plantations to facilitate restoration of native vegetation. However, it is important to conduct further research on the comparative advantage of enrichment planting of exclosures with preferred tree species or exclosures interspersed within blocks of plantation.

Introduction

Land degradation, which impairs land productivity in the Ethiopian Highlands, may lead to desertification if unabated. Especially in northern Ethiopia, land degradation has been accelerated by long-standing human impact through changing land use and deforestation (Hurni 1988; Nyssen et al 2009) and strong biomass demand for the still-increasing human and livestock populations (Tekle 1999). The most important countermeasures taken to halt this process have been plantation of trees and assisted natural regeneration by excluding human and animal interference (exclosure) (Pohjonen and Pukkala 1990; Tekle 2001).

Plantations of rapidly growing exotic tree species are good options for increased biomass productivity per given time and area (Pohjonen and Pukkala 1990). However, in terms of restoration of degraded lands, this option may fail to address the concerns of productivity and diversity, and it may not be feasible and compatible with specific local environmental, socioeconomic, and technological realities, which all may force tree plantations to be replaced or augmented with different restoration strategies, such as exclosure. Exclosures have been reported to be effective for native plant restoration (Mengistu et al 2005; Aerts et al 2007), improving soil attributes, and reducing soil erosion (Descheemaeker et al 2006a, 2006b). Similarly, plantations have been used to catalyze forest succession in the understory to restore native vegetation (Parrotta 1999; Lee et al 2005; Brockerhoff et al 2008) and improve soil physical and chemical attributes (Mishra et al 2003).

The 2 options considered here can foster secondary forest succession by improving soil conditions, attracting seed-dispersal agents, and modifying microclimate for understory growth; however, there might be differences with regard to speed in restoring native vegetation and soil close to their original condition. Findings show that seedlings of late successional tree species are especially impacted by environmental modifications following restoration (Farwig et al 2009). Thus, the diversity and density of late successional species can be used as proxies for the potential of different reclamation techniques to develop into more natural forests (Babaasa et al 2004).

Several studies have been conducted that compare pure and mixed-species plantation and natural forest (Lisanework and Michelsen 1994; Lugo 1997; Lemenih et al 2004a; Piotto et al 2004; Zamora and Montagnini 2007) to determine their impact on naturally regenerated native woody species (NRNWS) and soil. Few studies, however, have compared exclosure and plantation of exotic species on degraded lands in the dry Afromontane forests of Ethiopia. In this study, we compared exclosure, Cupressus lusitanica (CLP), and Eucalyptus globulus (EGP) plantations with respect to their impact on naturally regenerated native woody species (NRNWS) as well as on soil attributes.

Material and methods

Study area

The study area is located in Tehuledere district, South Wello, on the eastern edge of the northeastern highlands of Ethiopia (11°12′30.56″N; 39°40′44.51″E). The great Ethiopian Rift system is found within an ∼25 km radius. The topography is rugged, with a dissected and degraded plateau. The average altitude is 2350 m, mean annual temperature is 21°C, and the average annual precipitation is 1030 mm. The potential natural vegetation of the area is dry Afromontane forest dominated by Juniperus procera and Olea europaea ssp cuspidata. Broad-leaved species are dominant (Aalbaek 1993). The valley floors are settled by subsistence farmers engaged in mixed-crop production and livestock rearing. The average population density is estimated to be 285 persons per km2 (Tesfahun et al 2002). The study plots were established on the east-facing slope (20–45%) of a ridge that stretches through the political boundary of the district and that was rehabilitated by the efforts of donors and local partners following the Sahel drought of the 1970s (some of the reports related to the rehabilitation efforts are: Tekle et al 1997; Tekle 1999, 2001; Tekle and Bekele 2000; Tekle and Hedlund 2000). On this ridge, we purposely selected an area where an exclosure had been established between a block of E. globulus and C. lusitanica plantations on former grazing land. According to reports, it has been protected since establishment from human and domestic animal interference by paid guards as well as by the local population (Tesfahun et al 2002). This area was selected because it is one of the few forests that survived destruction in 1991 during the change of government. The exclosure and plantations were established in close proximity, creating a good opportunity to compare their effects, and they were also easily accessible.

Data collection

Vegetation sampling was done on transect lines perpendicular to the contours. The spacing between transects was 100 m. Circular sampling plots with a 5.64 m radius (∼100 m2) at 75 m intervals (adjusted for slope) were used on a transect. The maximum number of plots per transect was 3 in the exclosure and 2 in the plantations. The total number of plots per habitat was 6. Inside each plot, every woody plant greater than 3 cm diameter at breast height (DBH) was identified and measured. Identification of species and nomenclature follow Flora of Ethiopia and Eritrea (Edwards et al 1995; Hedberg and Edwards 1995; Edwards et al 1997).

Little is known about soil conditions before intervention; therefore, the grazing land was used as a reference. Sampling plots were located based on their representativeness by using available field methods such as similarity in soil color, structure, and cohesiveness when wet, developed by the first and second authors. Soil samples were then collected in 5 replicates per habitat from a pit dug from the 4 corners and center of square 20 m × 20 m plots, including on the grazing land. Samples were obtained from depths of 0–10 and 10–20 cm.

Soil analysis was carried out at the soil laboratory at the Sirinka Agricultural Research Center (Ethiopia). Soil pH was measured in water and 1 M KCl suspension at 1∶2.5 soil∶liquid ratio potentiometrically using glass-calomel combination electrodes. Soil organic C (SOC) and total N were determined using a LECO-1000 CHN analyzer. Available P was analyzed according to standard methods (Olsen et al 954). Potassium was analyzed by flame photometer (Black et al 1965). Cation exchange capacity (CEC) was determined following Chapman (1965). Bulk density was determined following Brady and Weil (2002).

Data analysis

The relative dominance or importance of a species in a given habitat can be expressed by the Importance value index (IVI). IVI is calculated as the sum of relative dominance, relative abundance, and relative frequency of species. Dominance is calculated as the sum of basal area (BA) in square meters per hectare of each species (BA =  π[DBH2/4]). Relative dominance is the percentage of the total basal area of a given species out of the total measured stem basal areas for all species, relative abundance is the percentage of the abundance (the number of stems of individuals of a species per ha) of each species compared to the total stem numbers for all species per hectare, and relative frequency is the percentage of frequency (the percentage of the total number of plots containing the species to all plots) of a species compared to the total frequencies of all the species added up. Plot-level species diversity statistics were calculated using the Shannon-Wiener index and Simpson's diversity index. The effects of habitats (created by each intervention) on the diversity statistics were determined with 1-way analysis of variance (ANOVA). The frequency of DBH (cm) size classes was used to compare population structure. The data obtained from the soil analyses were subjected to 1-way ANOVA for each sample depth separately.

Results

Woody species diversity

In total, 15 NRNWS from 13 families were recorded. All NRNWS were represented in the exclosure, but only 2 were found in CLP and 4 in EGP. About 75% of the species had more than 50% frequency in the exclosure. The most dominant species were Juniperus procera Hochst. ex Endl., Acacia abyssinica Hochst. ex Benth., Olea europaea ssp. cuspidata, Carissa edulis (Forssk.) Vahl, Nuxia congesta R.Br. ex Fresen., and Maytenus senegalensis (Lam.) Excell. The dominance, density, and frequency values for each species were higher in the exclosure than the plantation (Table 1). The IVI values for J. procera, A. abyssinica, and O. europaea in the exclosure were higher than the 2 plantations (Table 1).

Table 1

Frequency, abundance, dominance, relative dominance (%), and Importance value index (IVI) of the main naturally regenerated native woody species (NRNWS) under exclosure, C. lusitanica plantation (CLP), and E. globulus plantation (EGP). (Table extended on next page.)

i0276-4741-31-2-144-t01.tif

Species richness was significantly higher in the exclosure than in the 2 plantations (p < 0.001). There was no significant difference in species richness between the 2 plantations, although EGP had greater mean species richness value than CLP. Shannon-Wiener and Simpson's diversity indices also showed significant differences, where the exclosure was more diverse than the 2 plantations (Table 2). Stem diameter size distribution for the most dominant NRNWS was higher in the exclosure (Figure 1A) than in CLP (Figure 1B) and EGP (Figure 1C) for all size classes. Rather, smaller-sized individuals dominated in the plantations.

Figure 1

Frequency of the number of trees per ha according to stem diameter size. (A) Exclosure; (B) C. lusitanica plantation (CLP); (C) E. globulus plantation (EGP). Note: for reasons of scale, the number of trees per ha has been log transformed.

i0276-4741-31-2-144-f01.tif

Soil physical and chemical attributes

Significant (p < 0.05) differences in soil pH were found at the lower (10–20 cm) soil depth among habitats. In the case of SOC and N, the exclosure exhibited significantly higher (p < 0.001) values, and the order was exclosure > CLP > EGP > grazing land, except for EGP > CLP in SOC for the lower layer (Table 3). Mean values of CEC, K, and P were not significantly different (p > 0.05).

Bulk density (g cm−3) was also significantly (p < 0.001) different. The grazing land exhibited significantly (p < 0.00) higher mean value of soil bulk density, followed by EGP, CLP, and the exclosure (Table 3).

Discussion

Our results show, 30 years after establishment, that exclosure increased diversity of NRNWS more than the plantations. DBH for most of the encountered NRNWS was less than 15 cm, except in the population of A. abyssinica and J. procera, where 99% are less than 30 cm DBH, and more than 95% are less than 19 cm DBH. This difference may be explained by the regeneration strategy of NRNWS and can be discussed in relation to the facilitative or inhibitive processes created by postintervention environmental conditions (Connell and Slatyer 1977).

Reports have shown that succession achieves successful seedling recruitment in dry Afromontane forests either from seed rain or advance regeneration (Teketay 1997a, 1997b, 1997c, 2005). However, these regeneration pathways are reportedly impeded by several limitations. Seed limitation has been reported due to diminished natural vegetation from long-standing deforestation and the confinement of mother trees in churches and remote groves (Wassie and Teketay 2006; Wassie et al 2009), absence of soil seed banks and their depletion by cultivation (Teketay and Granström 1995; Teketay and Granström 1997a, 1997b; Teketay 1998; Lemenih and Teketay 2005), and insufficient disperser activity because the seeds of late successional native plants are large, short-lived, and dependent on frugivorous animals for dispersal (Aerts et al 2006, 2008a). Similar studies also have shown that light, moisture, seed dormancy, and other biotic and abiotic factors limit establishment of late successional tree species.

Our results showed higher frequency of NRNWS for all stem diameter size classes in the exclosure than on the plantations (Figure 1A, B, and C). This suggests that the exclosure created a postintervention environment that facilitated succession, either from seed rain or advance regeneration. Regeneration from seed rain might have been facilitated in the exclosure by increased seed influx, forest structural diversity, attraction of animal seed dispersers (Zanne and Chapman 2001), and creation of light, moisture, and other resource gradients favorable for germination and establishment of diverse NRNWS (Yirdaw 2001; Yirdaw and Leinonen 2002; Yirdaw and Luukkanen 2004).

The positive role of soil seed bank (SSB) against establishment and seed limitations might have contributed to the observed differences. Although we did not measure SSB, and there have been reports of little similarity between SSB and standing flora, and SSB mostly composed of annual plants (Teketay and Granström 1995), pioneer plants from the SSB have strong effects in modifying the environment to facilitate secondary succession (Tekle and Bekele 2000). In addition, some light-demanding trees that have a strong effect on secondary succession might originate from the SSB. For instance, A. abyssinica and J. procera are represented by larger-sized individuals in irregular patterns in the plantations and in almost every size class in the exclosure (Figure 1A–C). Although some of the extremely large trees (<2%; not shown in Figure 1A–C) may be remnants of the original vegetation, the majority are likely to have established from the SSB before the habitat changed much in the plantations. Previous studies have shown that seeds from these 2 species have longer viability and different dormancy mechanisms (Teketay 1998; Wassie et al 2009). Disturbance during plantation-site preparation may break dormancy and trigger germination, and protection from human and livestock would ensure successful recruitment. However, this recruitment does not seem to have occurred continuously; rather, it likely fluctuated with time and affected canopy characteristics, which would have indirectly determined germination (Yirdaw and Leinonen 2002; Yirdaw and Luukkanen 2004).

Succession through the pathway of advance regeneration might have improved NRNWS diversity under exclosure. Site clearance and weeding, which are important activities in plantation forest management, especially impede advance regeneration, as noted by Hartley (2002). Some NRNWS in particular, which are exposed to different stresses of herbivory, fire, and cutting, show highly modified morphology. However, when left in situ and relieved from stress with the establishment of exclosures, they can play a remarkable role in the recovery of tree canopy and forest microclimate and forest succession by resprouting. For instance, in situ persistence, the ability to produce vegetative shoots and hence modified morphology, is an important addition to other recruitment pathways such as recruitment via seed rain for Olea europaea ssp. cuspidate (Aerts et al 2008b).

According to studies from other different areas, tree plantations increase the diversity of understory woody vegetation, which varies with species (eg Kuusipalo et al 1996; Slocum 2000; Ashton et al 2001; Cusack and Montagnini 2004; Butler et al 2008). Similarly, among plantation species, the broad-leaved Eucalyptus sp. encouraged higher understory plant recruitment than the conifer (Cupressus sp.), which conforms to results from previous studies in Ethiopia (Yirdaw 2001; Lemenih et al 2004a; Yirdaw and Luukkanen 2004). Such variations are attributed to stand canopy characteristics that determine the amount of canopy gaps available for solar radiation, which influences the environmental conditions at the forest floor such as light and air and soil temperatures.

Our results also suggest that exclosure affected the soil chemical attributes desirably. This is consistent with previous studies (eg Descheemaeker et al 2009). Similarly, Mekuria et al (2007) found higher soil organic matter content, total nitrogen, available phosphorus, exchangeable bases, and CEC values in an exclosure (10 years old) than on the adjacent grazing land.

The plantations improved soil features associated with chemical characteristics better than the grazing land. This also conforms to previous reports (Mishra et al 2003; Lemenih et al 2004b; Lemma et al 2006; Boley et al 2009). For instance, Lemenih et al (2004b) reported lower bulk density and higher soil C, total N, CEC, base saturation, K, Ca, and Mg after 15 years of C. lusitanica plantation than in soils under cultivation.

The bulk density results from the soil in the exclosure are in agreement with previous reports (Descheemaeker et al 2006b; Castellano and Valone 2007; Jeddi and Chaieb 2010), which showed that grazing increased soil compaction, bulk density, and runoff.

Implications for practice

Recruitment of NRNWS and improved soil attributes can be achieved with the establishment of exclosures, given enough time. The major practical implications are: First, exclosures can be established interspersed strategically with single- or mixed-species plantations to facilitate restoration of native vegetation. Second, future tree plantation activities should consider maintaining original vegetation to foster recruitment of seedlings/saplings either from seed rain or soil seed bank through recolonization or advance regeneration through resprouting. However, further research will be required to gain insights into the comparative advantage of either enrichment planting of exclosures with the desired tree species or interspersing exclosures within blocks of single- or mixed-species plantations.

Table 2

Mean ± SE for species richness, Shannon-Wiener, and Simpson's diversity values under exclosure, C. lusitanica plantation (CLP), and E. globulus plantation (EGP).

i0276-4741-31-2-144-t02.tif

Table 3

Mean ± SE result of soil pH, soil organic carbon (SOC), total nitrogen (N), available potassium (K), available phosphorus (P), and bulk density (BD) for depths of 0–10 cm and 10–20 cm for the exclosure, C. lusitanica plantation (CLP), grazing land (GL), and E. globulus plantation (EGP), and corresponding F and P values from ANOVA.

i0276-4741-31-2-144-t03.tif

Open access article: please credit the authors and the full source.

Acknowledgments

The authors would like to thank the Amhara Region Agricultural Research Institute (ARARI), Bahir Dar, Ethiopia, for logistic support. Financial support for the first author from the Commission for Development Studies (KEF) at the Austrian Agency for International Cooperation in Education and Research, Vienna, Austria, and the International Foundation for Science (IFS) Sweden, Stockholm, is gratefully acknowledged.

REFERENCES

  1. A. Aalbaek 1993. Seed Zones of Ethiopia and Eritrea. Addis Abeba, Ethiopia National Tree Seed Project. Google Scholar

  2. R. Aerts, W. Maes, E. November, A. Negussie, M. Hermy, and B. Muys . 2006. Restoring dry Afromontane forest using bird and nurse plant effects: Direct sowing of Olea europaea ssp. Cuspidata seeds. Forest Ecology and Management 230 (1–3):23–31. Google Scholar

  3. R. Aerts, A. Negussie, W. Maes, E. November, M. Hermy, and B. Muys . 2007. Restoration of dry Afromontane forest using pioneer shrubs as nurse-plants for Olea europaea ssp. Cuspidata. Restoration Ecology 15 (1):129–138. Google Scholar

  4. R. Aerts, F. Lerouge, E. November, L. Lens, M. Hermy, and B. Muys . 2008a. Land rehabilitation and the conservation of birds in a degraded Afromontane landscape in northern Ethiopia. Biodiversity and Conservation 17:53–69. Google Scholar

  5. R. Aerts, E. November, W. Maes, I. Van der Borght, A. Negussie, E. Aynekulu, M. Hermy, and B. Muys . 2008b. In situ persistence of African wild olive and forest restoration in degraded semiarid savanna. Journal of Arid Environments 72 (6):1131–1136. Google Scholar

  6. M. Ashton, C. Gunatilleke, B. Singhakumara, and I. Gunatilleke . 2001. Restoration pathways for rain forest in southwest Sri Lanka: A review of concepts and models. Forest Ecology and Management 525:1–23. Google Scholar

  7. D. Babaasa, G. Eilu, A. Kasangaki, R. Bitariho, and A. McNeilage . 2004. Gap characteristics and regeneration in Bwindi Impenetrable National Park, Uganda. African Journal of Ecology 42:217–224. Google Scholar

  8. C. A. Black, D. D. Evans, J. L. White, L. E. Ensminger, and F. E. Clark . 1965. Methods of Soil Analysis. Part 1. Physical and Mineralogical Properties, Including Statistics of Measurement and Sampling. Madison, WI American Society of Agronomy. Google Scholar

  9. J. D. Boley, A. P. Drew, and R. E. Andrus . 2009. Effects of active pasture, teak (Tectona grandis) and mixed native plantations on soil chemistry in Costa Rica. Forest Ecology and Management 257 (11):2254–2261. Google Scholar

  10. N. C. Brady and R. R. Weil . editors. 2002. The Nature and Properties of Soils. 13th edition. Englewood Cliffs, NJ Prentice-Hall. Google Scholar

  11. E. G. Brockerhoff, H. Jactel, J. A. Parrotta, C. P. Quine, and J. Sayer . 2008. Plantation forests and biodiversity: Oxymoron or opportunity? Biodiversity and Conservation 17:925–951. Google Scholar

  12. R. Butler, F. Montagnini, and P. Arroyo . 2008. Woody understory plant diversity in pure and mixed native tree plantations at La Selva Biological Station, Costa Rica. Forest Ecology and Management 255 (7):2251–2263. Google Scholar

  13. M. J. Castellano and T. J. Valone . 2007. Livestock, soil compaction and water infiltration rate: Evaluating a potential desertification recovery mechanism. Journal of Arid Environments 71 (1):97–108. Google Scholar

  14. H. D. Chapman 1965. Cation exchange capacity. In: C. A. Black, D. D. Evans, J. L. White, L. E. Ensminger, and F. E. Clark . editors. Methods of Soil Analysis. Vol 9. Madison, WI American Society of Agronomy. pp. 891–901. Google Scholar

  15. J. H. Connell and R. O. Slatyer . 1977. Mechanisms of succession in natural communities and their role in community stability and organization. The American Naturalist 111 (982):1119–1144. Google Scholar

  16. D. Cusack and F. Montagnini . 2004. The role of native species plantations in recovery of understory woody diversity in degraded pasturelands of Costa Rica. Forest Ecology and Management 188 (1–3):1–15. Google Scholar

  17. K. Descheemaeker, B. Muys, J. Nyssen, J. Poesen, D. Raes, M. Haile, and J. Deckers . 2006a. Litter production and organic matter accumulation in exclosures of the Tigray Highlands, Ethiopia. Forest Ecology and Management 233 (1):21–35. Google Scholar

  18. K. Descheemaeker, J. Nyssen, J. Poesen, D. Raes, M. Haile, B. Muys, and S. Deckers . 2006b. Runoff on slopes with restoring vegetation: A case study from the Tigray Highlands, Ethiopia. Journal of Hydrology 331 (1–2):219–241. Google Scholar

  19. K. Descheemaeker, B. Muys, J. Nyssen, W. Sauwens, M. Haile, J. Poesen, D. Raes, and J. Deckers . 2009. Humus form development during forest restoration in exclosures of the Tigray Highlands, northern Ethiopia. Restoration Ecology 17 (2):280–289. Google Scholar

  20. S. Edwards, T. Mesfin, and I. Hedberg . 1995. Flora of Ethiopia and Eritrea. Vol 2, Part 2. Addis Abeba, Ethiopia The National Herbarium, Addis Abeba University; and Uppsala, Sweden: Department of Systematic Botany, Uppsala University. Google Scholar

  21. S. Edwards, D. Sebsebe, and I. Hedberg . 1997. Flora of Ethiopia and Eritrea. Vol 6. Addis Abeba, Ethiopia The National Herbarium, Addis Abeba University; and Uppsala, Sweden: Department of Systematic Botany, Uppsala University. Google Scholar

  22. N. Farwig, N. Sajita, and K. Böhning-Gaese . 2009. High seedling recruitment of indigenous tree species in forest plantations in Kakamega Forest, western Kenya. Forest Ecology and Management 257 (1):143–150. Google Scholar

  23. M. J. Hartley 2002. Rationale and methods for conserving biodiversity in plantation forests. Forest Ecology and Management 155 (1–3):81–95. Google Scholar

  24. I. Hedberg and S. Edwards . 1995. Flora of Ethiopia. Vol 7. Addis Abeba, Ethiopia The National Herbarium, Addis Abeba University; and Uppsala, Sweden: Uppsala University. Google Scholar

  25. H. Hurni 1988. Degradation and conservation of soil resources in the Ethiopian Highlands. Mountain Research and Development 8:123–130. Google Scholar

  26. K. Jeddi and M. Chaieb . 2010. Changes in soil properties and vegetation following livestock grazing exclusion in degraded arid environments of south Tunisia. Flora—Morphology, Distribution, Functional Ecology of Plants 205 (3):184–189. Google Scholar

  27. J. Kuusipalo, Y. Jafarsidik, G. Ådjers, and K. Tuomela . 1996. Population dynamics of tree seedlings in a mixed Dipterocarp rainforest before and after logging and crown liberation. Forest Ecology and Management 81 (1–3):85–94. Google Scholar

  28. E. W. S. Lee, B. C. H. Hau, and R. T. Corlett . 2005. Natural regeneration in exotic tree plantations in Hong Kong, China. Forest Ecology and Management 212 (1–3):358–366. Google Scholar

  29. M. Lemenih, T. Gidyelew, and D. Teketay . 2004a. Effects of canopy cover and understory environment of tree plantations on richness, density and size of colonizing woody species in southern Ethiopia. Forest Ecology and Management 194 (1–3):1–10. Google Scholar

  30. M. Lemenih, M. Olsson, and E. Karltun . 2004b. Comparison of soil attributes under Cupressus lusitanica and Eucalyptus saligna established on abandoned farmlands with continuously cropped farmlands and natural forest in Ethiopia. Forest Ecology and Management 195 (1–2):57–67. Google Scholar

  31. M. Lemenih and D. Teketay . 2005. Effect of prior land use on the recolonization of native woody species under plantation forests in the highlands of Ethiopia. Forest Ecology and Management 218 (1–3):60–73. Google Scholar

  32. B. Lemma, D. B. Kleja, I. Nilsson, and M. Olsson . 2006. Soil carbon sequestration under different exotic tree species in the southwestern highlands of Ethiopia. Geoderma 136 (3–4):886–898. Google Scholar

  33. N. Lisanework and A. Michelsen . 1994. Litterfall and nutrient release by decomposition in three plantations compared with a natural forest in the Ethiopian highland. Forest Ecology and Management 65 (2–3):149–164. Google Scholar

  34. A. E. Lugo 1997. The apparent paradox of reestablishing species richness on degraded lands with tree monocultures. Forest Ecology and Management 99 (1–2):9–19. Google Scholar

  35. W. Mekuria, E. Veldkamp, M. Haile, J. Nyssen, B. Muys, and K. Gebrehiwot . 2007. Effectiveness of exclosures to restore degraded soils as a result of overgrazing in Tigray, Ethiopia. Journal of Arid Environments 69 (2):270–284. Google Scholar

  36. T. Mengistu, D. Teketay, H. Hulten, and Y. Yemshaw . 2005. The role of enclosures in the recovery of woody vegetation in degraded dryland hillsides of central and northern Ethiopia. Journal of Arid Environments 60 (2):259–281. Google Scholar

  37. A. Mishra, S. D. Sharma, and M. K. Gupta . 2003. Soil rehabilitation through afforestation: Evaluation of the performance of Prosopis juliflora, Dalbergia sissoo and Eucalyptus tereticornis plantations in a sodic environment. Arid Land Management and Research 17:257–269. Google Scholar

  38. J. Nyssen, M. Haile, J. Naudts, N. Munro, J. Poesen, J. Moeyersons, A. Frankl, J. Deckers, and R. Pankhurst . 2009. Desertification? Northern Ethiopia re-photographed after 140 years. Science of the Total Environment 407 (8):2749–2755. Google Scholar

  39. S. R. Olsen, C. V. Cole, F. S. Watanabe, and L. A. Dean . 1954. Estimation of Available Phosphorous in Soils by Extraction with Sodium Bicarbonate. USDA Circular 939. Washington, DC USDA. Google Scholar

  40. J. A. Parrotta 1999. Productivity, nutrient cycling, and succession in single- and mixed-species plantations of Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala in Puerto Rico. Forest Ecology and Management 124 (1):45–77. Google Scholar

  41. D. Piotto, E. Viquez, F. Montagnini, and M. Kanninen . 2004. Pure and mixed forest plantations with native species of the dry tropics of Costa Rica: A comparison of growth and productivity. Forest Ecology and Management 190:359–372. Google Scholar

  42. V. Pohjonen and T. Pukkala . 1990. Eucalyptus globulus in Ethiopian forestry. Forest Ecology and Management 36 (1):19–31. Google Scholar

  43. M. G. Slocum 2000. Logs and fern patches as recruitment sites in a tropical pasture. Restoration Ecology 8 (4):408–413. Google Scholar

  44. D. Teketay and A. Granström . 1995. Soil seed banks in dry Afromontane forests of Ethiopia. Journal of Vegetation Science 6:777–786. Google Scholar

  45. D. Teketay 1997a. The impact of clearing and conversion of dry Afromontane forests into arable land on the composition and density of soil seed banks. Acta Oecologica 18 (5):557–573. Google Scholar

  46. D. Teketay 1997b. Seedling population in dry Afromontane forests of Ethiopia. Forest Ecology and Management 98:149–165. Google Scholar

  47. D. Teketay 1997c. Seedling populations and regeneration of woody species in dry Afromontane forests of Ethiopia. Forest Ecology and Management 98 (2):149–165. Google Scholar

  48. D. Teketay and A. Granström . 1997a. Germination ecology of forest species from the highlands of Ethiopia. Journal of Tropical Ecology 14:793–803. Google Scholar

  49. D. Teketay and A. Granström . 1997b. Seed viability of Afromontane tree species in forest soils. Journal of Tropical Ecology 13:81–95. Google Scholar

  50. D. Teketay 1998. Soil seed banks at an abandoned Afromontane arable site. Feddes Repertorium 109:161–174. Google Scholar

  51. D. Teketay 2005. Seed and regeneration ecology in dry Afromontane forests of Ethiopia: I. Seed production - population structures. Tropical Ecology 46 (1):29–44. Google Scholar

  52. K. Tekle, I. Backéus, J. Skoglund, and Z. Woldu . 1997. Vegetation on hill slopes in southern Wello, Ethiopia: Degradation and regeneration. Nordic Journal of Botany 17 (5):483–493. Google Scholar

  53. K. Tekle 1999. Land degradation problems and their implications for food shortage in South Wello, Ethiopia. Environmental Management 23 (4):419–427. Google Scholar

  54. K. Tekle and T. Bekele . 2000. The role of soil seed banks in the rehabilitation of degraded hill slopes in southern Wello, Ethiopia. Biotropica 32 (1):23–32. Google Scholar

  55. K. Tekle and L. Hedlund . 2000. Land cover change between 1958 and 1986 in Kalu district, southern Wello, Ethiopia. Mountain Research and Development 20 (1):42–45. Google Scholar

  56. K. Tekle 2001. Natural regeneration of degraded hill slopes in southern Wello, Ethiopia: A study based on permanent plots. Applied Geography 21:275–300. Google Scholar

  57. G. Tesfahun, A. Abiyu, B. Balkewu, S. Menbere, F. Getachew, L. Admasu, Z. Berhane, and A. Beyene . 2002. Farming System in Tehuledere District, South Wello, Ethiopia Unpublished paper presented at the Amhara Region Agricultural Research Institute (ARARI) Annual Research Review Workshop. Bahir Dar, Ethiopia, 10–15 January 2002. Available from corresponding author of this article.  Google Scholar

  58. A. Wassie and D. Teketay . 2006. Soil seed banks in church forests of northern Ethiopia: Implications for the conservation of woody plants. Flora—Morphology, Distribution, Functional Ecology of Plants 201 (1):32–43. Google Scholar

  59. A. Wassie, F. J. Sterck, D. Teketay, and F. Bongers . 2009. Tree regeneration in church forests of Ethiopia: Effects of microsites and management. Biotropica 41 (1):110–119. Google Scholar

  60. E. Yirdaw 2001. Diversity of naturally-regenerated native woody species in forest plantations in the Ethiopian Highlands. New Forests 22:159–177. Google Scholar

  61. E. Yirdaw and K. Leinonen . 2002. Seed germination responses of four Afromontane tree species to red/far-red ratio and temperature. Forest Ecology and Management 168:53–61. Google Scholar

  62. E. Yirdaw and O. Luukkanen . 2004. Photosynthetically active radiation transmittance of forest plantation canopies in the Ethiopian Highlands. Forest Ecology and Management 188:17–24. Google Scholar

  63. C. O. Zamora and F. Montagnini . 2007. Seed rain and seed dispersal agents in pure and mixed plantations of native trees and abandoned pastures at La Selva Biological Station, Costa Rica. Restoration Ecology 15 (3):453–461. Google Scholar

  64. A. E. Zanne and C. A. Chapman . 2001. Expediting reforestation in tropical grasslands: Distance and isolation from seed sources in plantations. Ecological Applications 11:1610–1621. Google Scholar

Abrham Abiyu, Mulugeta Lemenih, Georg Gratzer, Raf Aerts, Demel Teketay, and Gerhard Glatzel "Status of Native Woody Species Diversity and Soil Characteristics in an Exclosure and in Plantations of Eucalyptus globulus and Cupressus lusitanica in Northern Ethiopia," Mountain Research and Development 31(2), 144-152, (1 May 2011). https://doi.org/10.1659/MRD-JOURNAL-D-10-00116.1
Received: 1 March 2011; Accepted: 1 April 2011; Published: 1 May 2011
JOURNAL ARTICLE
9 PAGES


SHARE
ARTICLE IMPACT
Back to Top