Vegetation structural characteristics and topographic factors in the remnant moist Afromontane forest of Wondo Genet, south central Ethiopia

For forest ecosystem management to be effective, knowledge of the horizontal and vertical structural diversity of a forest is essential. The moist Afromontane highlands of Wondo Genet in south-central Ethiopia present an opportunity to restore and rehabilitate and enhance the ecosystem services to be obtained from this forest sustainably. We focused on the forest structural characteristics to better understand the current forest conditions to assist in the sustainable management of this resource. A total of 75 （20 m × 20 m） quadrats were sampled and diame- ter at breast height （DBH） 〉2 cm and stem height 〉2 m were measured. Species identity and abundance, elevation, slope, and aspect were recorded for each plot. Structural characteristics were computed for each plot. Relationship of topographic factors with vegetation characteristics was conducted using R-Software. A total of 72 woody species was re- corded. Whereas, the overall diameter distribution shows an inverted J-shaped curve, the basal area followed a bell-shaped pattern. Five types of population structures are revealed. The mean tree density and basal area was 397.3 stems.ha-1 and 31.4 m2.ha-1, respectively. Only 2.8% of the tree species have densities of 〉25 stems.ha^-1 and the percentage dis- tribution of trees show 56.2% in the DBH class 2-10 cm, indicating that the forest is dominated by medium-sized trees. Celtis africana （8.81 m2.ha^-1） and Pouteria adolfi-friederieii （5.13 m2.ha^-1） make the highest contribution to the basal area and species importance value index. The families/species with the highest importance value index are Ulmaceae, Fabacea and Sapotaceae. Species abundance （r2 = 0.32, p 〈0.001） and species richness （P =0.50, p 〈0.001） are positively related with tree density. Tree density is negatively related with elevation （~ = -0.36, p 〈0.001）, slope （r2 =-0.15, p 〈0.001） and aspect （r2 = -0.07, p 〈0.05）. While basal area is negatively related with elevation （r2 =-0.14, p 〈0.001）, it has a positive relationship with tree density （r2 =0.28, p 〈0.001 and species richness （r2 =0.098）. Species with poor population structure should be assisted by restoration tasks and further anthropogenic distur- bance such as illegal logging and fuel wood extraction should be re- stricted.

Effect of border planting of Eucalyptus citriodora Hook. on the growth and biomass production performance of Cymbopogon winterianus Jowitt ex Bor Grass at Wondo Genet,Southern Ethiopia

The use of Eucalyptus trees, in association with other plants, has the potential to reduce the growth of neighbouring plants or grasses by competing for resources or releasing allelochemicals that may cause other plants to grow slowly. Our purpose here is to assess whether border planting of Eucalyptus is harmful to the establishment,growth, and production of Cymbopogon winterianus at various distances from tree lines in the Wondo Genet Agricultural Research Center in Southern Ethiopia. Several factors were studied: growth performances and yield of aromatic grasses; soil properties, including total nitrogen,organic carbon, and moisture content; and plant leaf nutrient content(NPK) at various distances away from the Eucalyptus citriodora border line were studied. Chemical compositions of hydro-distilled essential oils obtained from selected C. winterianus grasses leaves were analysed by gas chromatography. Plant height, biomass yield, amount of essential oil yield, and essential oil composition all were significantly affected due to Eucalyptus effect in the first10-m distance as compared to beyond 10 m from the tree border line. There were increases in soil total nitrogen,organic carbon, and moisture content with decreasing distances to the Eucalyptus tree border. The result of plant leaf nutrient content(NPK) differed across treatment and distance. The pot experiment(15 cm 9 20 cm), shoot length,and number of leaves of aromatic plants varied in the degree of inhibition based on the concentration of the aqueous extract. Significantly higher inhibitions of the shoot length and number of leaf parameters were observed when using 25% fresh leaf extract compared to other extract levels.

Woody Species Diversity and Structure of Agroforestry and Adjacent Land Uses in Dallo Mena District, South-East Ethiopia

Sustainable farming practice that utilizes and conserves biodiversity, reducing negative impacts of agriculture on biodiversity and provides wood and energy to local community is a good solution to reduce deforestation and forest degradation. This study was carried out in Dallo Mena district of Bale zone to identify woody species diversity in homegarden agroforestry practices, shade grown coffee agroforestry practices and adjacent natural forest, and to show how land use and management practice determine the plant species diversity. The study site was selected based on spatial analogue approach. In each land use, a plots of 10 m × 10 m size was drown by using systematic sampling method following the transect line. A total of 36 sample plots were sampled along the transect line laid down inside each land uses. In each plot, woody species were counted and the diameter and height of trees and shrubs were measured. Based on this inventory a total of 39 woody plant species which are about 23, 10, 15 woody plant species were recorded from natural forest, shade grown coffee agroforestry and homegarden agroforestry practices respectively. These species were classified belonging to 24 families. The Shannon Wiener diversity index used to estimate species diversity ranged from 0.14 to 2.54 with a mean of 1.47. Also 21% woody species similarities were observed between those three land uses. The result shows that both agroforestry practices (shade grown coffee and home garden agroforestry practices) and adjacent natural forests are conserving several woody species diversity in its system.

Influence of topographic aspect on floristic diversity, structure and treeline of afromontane cloud forests in the Bale Mountains,Ethiopia

We studied the influence of east and west aspects on floristic composition, diversity, structure and treeline of afromontane cloud forests at Rira in the Bale Mountains, southeast Ethiopia. In addition, we studied how aspect relates to and/or interacts with other topographic and edaphic factors in influencing vegetation diversity. Strati- fied systematic plot sampling was used to survey the floristic composition, diversity and structure of forests on east- and west-facing slopes. The sample plot size was 20 x 20 m and a total of 36 plots were inventoried. A total of 72 composite soil samples were collected and analysed. Woody species richness of the forest on the east-facing slope was 1.7 times higher than on the west-facing slope. Shannon, Simpson and Log-series alpha diversity indices and evenness of forests on the east-facing slope were sig- nificantly higher than on the west-facing slope. NMDS ordination indicated that the east- and west-facing slopes formed two clusters of species and aspect explained 55.2 % and 10.4 % of the variation in species richness and abun- dance, respectively. There was no significant difference between aspects in stand structure except in dominantheight, which was higher on the east-facing slopes. There was significant interaction between aspect and elevation in influencing woody species diversity. The four plant com- munity groups, which were identified using cluster and indicator species analysis were represented differently on the east and west aspects. The treeline on the east-facing slope （3352 m） was located about 110 m higher than on the west-facing slope （3240 m）. Soil moisture deficiency was unlikely to be a limiting factor on either site. Near the equator, east-west aspect was shown to have considerable impact on floristic composition, diversity, structure, and treeline position of montane forests. Diurnal cloud move- ment patterns and its impact on microclimate of slope aspect should be taken into account in future studies of cloud forest diversity, structure, and treeline position.

Effects of level soil bunds and stone bunds on soil properties and its implications for crop production: the case of Bokole watershed, Dawuro zone, Southern Ethiopia

Level soil bunds (LSB) and stone bunds (SB) have been widely implemented in the Bokole watershed since 2000 through support of the World Food Program (WFP). However, the performance of them against the target of the structure has not been studied. This study analyzed the effect of LSB and SB on selected soil properties, when compared with nonterraced cropland. The Bokole watershed was divided into two units. From upper watershed, three croplands with LSB (aged 4, 6, and 9 years) and three nonterraced croplands each adjacent to one of the LSB were selected. Similarly, in lower watershed, SB aged 4, 6, and 8 years and three nonterraced croplands each adjacent to one of the SB were selected. From each cropland with LSB and SB, three composite soil samples (rep licates) were collected systematically in X designed rectangular plot. From each nonterraced cropland, three composite soil samples (replicates) were collected in X designed square plot. A total of 36 soil samples were analyzed for Soil Organic Carbon (SOC), Total Nitrogen (TN), Available Phosphorus (AP), Available Potassium (AK), pH, and Cation Exchange Capacity (CEC) following standard laboratory procedures. Most soil parameters were not significantly different in cropland with LSB and SB compared to nonterraced. However, in LSB aged 4 years and SB aged 6 years AP and pH were significantly less than their adjacent-nonterraced cropland. In SB aged 8 years, SOC, AP, AK, and pH were also significantly less than adjacent-nonterraced cropland. Past erosion, and past land uses are likely factors contributed to the observed result. It was inferred that the mean con tribution of LSB and SB alone for crop production with regard to analyzed soil parameters was not significant in the considered sites. Additional soil fertility management practices should be incorporated for better effect.

Micropropagation of Kebericho: An Endandered Ethiopian Medicinal Plant

Echinops kebericho, endemic to Ethiopia, is a critically endangered medicinal plant. It is among the most important medicinal plants of the country, valued primarily for its root parts. The commercial harvesting and sale of roots of E. kebericho have threatened local populations. This study aimed to develop micropropagation protocol for E. kebericho using shoot tip explants. The study started with seed germination test using seeds stored for different months. Shoot tips from in vitro germinated seedlings were cultured on shoot initiation MS media supplemented with 0, 0.1, 0.5, 1.0, 1.5 and 2.0 mg/l BAP or KN alone. Explants were cultured on shoot proliferation media fortified with Kinetin, BAP, and TDZ each at 0.0, 0.5, 1.0, 2.5, 3.0 and 5.0 mg/l either alone or in combination with 0.0, 0.1, 0.25 and 0.5 mg/l NAA. For rooting, full, half and 1/3 strength MS media supplemented with IBA and NAA alone each at 0, 0.05, 0.1, 0.5, 1.0, 1.5 and 2.5 mg/l were used. Growth regulator free MS medium was used as control. Study results showed that 100% germination was recorded in fresh seeds and dropped as low as 65.18% and 22.3% for 3 and 5 months seeds respectively. 1.0 mg/l KN and 0.5 mg/l KN + 0.1 mg/l NAA showed maximum shoot proliferation on shoot induction media and shoot multiplication media respectively. Best rooting was obtained on 1/3 MS containing 1.5 mg/l NAA with 8.23 roots and 4.82 cm root length and established under greenhouse with 83% survival.

Diversity, regeneration status and population structure of gum-and resin-bearing woody species in south Omo zone, southern Ethiopia

South Omo Administrative Zone in Ethiopia is home to 18 indigenous ethnic groups whose livelihood is vulnerable due to recurrent drought and degradation. Despite the preliminary observation showing the rich dry-forest resource base that, if sustainably managed could enhance livelihoods and biodiversity conservation, there is lack of empirical data on its current status. We conducted a study aiming at quantifying the population status of gum- and resin-bearing species in two randomly selected districts, Hamer and Bena-Tsemay. Seventy-five quadrats （35 at Hamer and 40 at Bena-Tsemay） each measuring 400 m2 were established along line transects to assess species diversity and equitability, density, frequency, dominance, importance value and population structure. We recorded a total of 27 woody species of 12 families and 14 genera. Fifteen species （9 at Hamer and 14 at Bena-Tsemay） of the genera Acacia, Boswellia, Commiphora and Sterculia, were identified as either major sources of commercial gums and resins or their adulterants. Gum- and resin-bearing species comprised 56% and 57% of species richness, 48% and 50% of total density per ha, 95% and 98% of basal area, and 64% and 56% of importance values at Hamer and Bena-Tsemay, respectively. Diversity of the entire woody species assemblage and of the gum- and resin-bearing species was slightly higher at Bena-Tsemay （H= 2.61, 1.4） than at Hamer （H＇= 2.48, 1.28）, respectively. The diversity and abundance of the resource base suggest potential for development of value-added commercialization of gum and resins to enhance livelihoods and encourage sustainable management of the forest at these study areas. We recorded, however, declining natural regeneration of most gum- and resin-bearing species, and this calls for integrated and participatory species management and landscape rehabilitation.

Woody plant species diversity and composition in and around Debre Libanos church forests of North Shoa Zone of Oromiya,Ethiopia

Dry afromontane forests are among the most poorly managed and endangered ecosystems.Therefore,we assessed the composition,diversity,and conservation status of woody plant species of the Debre Libanos church forests and surrounding forest lands in Oromiya Regional National State,central Ethiopia in 62 nested circular sample plots spaced 200 m apart along two transect lines.Large circular plots 314 m^(2)were used to sample trees with DBH of at least 10 cm,and subplots of 28.26 m^(2)were laid in each main plot were used to assess saplings and shrubs;a small subplot of 3.14 m2 was used to assess seedlings.In total,70 woody plant species belonging to 62 genera and 43 families were recorded.Of these,59,28 and 32 were in the church,government and private forest types,respectively.The most dominant families were Fabaceae and Verbenaceae,each represented by five species.In the forests considered,trees accounted for 61%,and shrubs with diameter at breast height(DBH)of 1-10 cm accounted for ca.33%.Among growth forms of woody species,shrubs and seedlings,followed by trees constituted much of the density of woody species in all the three ownership types of forests.The church forest had the most species(59)and highest Shannon(3.12)and Simpson(0.92)species diversity indices,and the government and private forests had a nearly similar total number of species and Shannon and Simpson species diversity indices.Most of the species with higher importance value indices(IVI)were indigenous in origin within the church forest(Juniperus procera=82),government forest(J.procera=66)and private forest(Acacia abyssinica=84).The composition,diversity,and population structure of woody species in the church forest were significantly higher than in the other forest lands.However,interventions of the government and private sectors to conserve forest systems in the areas,particularly the government-owned forest and specific species such as Olea europaea need active enrichment plantings due to their limited natural regeneration.Without improved management interventions,livelihood income diversification and ecosystem services obtained from the forest will not be sustainable.

Impact of Land Cover Change on Water Quality and Stream Flow in Lake Hawassa Watershed of Ethiopia

Quantifying the hydrologic response of land use/land cover change (LULCC) is of paramount importance to improve land management. This study was carried out to analyze the effect of LULCC on water quality and quantity. LULCC of the watershed in 1986, 1999 and 2011 was analyzed from Landsat satellite images using supervised classification. Time series and point data were collected from the upper and lower sections of Wedesa, Wesha and Hallo Rivers. Water quality parameters (turbidity, suspended solid (SS), total dissolved solid (TDS), pH, electric conductivity (EC), total organic carbon (TOC), ammonia, nitrate and phosphate) were analyzed in the laboratory. A considerable decline in forest and an increase in woodland were observed in the watershed during the indicated periods. Turbidity, SS, TDS and EC were significantly higher (P < 0.05) in the lower section of the rivers compared to the upper ones. Ammonia, nitrate and phosphate were higher in the lower section of some rivers compared to the upper ones. In general, water quality in the upper watershed of the three rivers was better than the lower one with respect to considered parameters, which might be related to the observed LULCC. Most water quality parameters varied (P < 0.05) seasonally in both the upper and lower sections of the rivers. Despite the irregular rainfall pattern and increased water consumption from the catchment, the annual discharge of the Tikur-Wuha River to Lake Hawassa shows an increasing trend. We concluded that the discharge is not only related to the upstream LULCC but also to the management of the Cheleleka wetland. However, further investigation is required to determine the dominant factors affecting inflow discharge to Lake Hawassa.

Climate forcing of tree growth in dry Afromontane forest fragments of Northern Ethiopia:evidence from multi-species responses

Background: Climate-induced challenge remains a growing concern in the dry tropics, threatening carbon sink potential of tropical dry forests. Hence, understanding their responses to the changing climate is of high priority to facilitate sustainable management of the remnant dry forests. In this study, we examined the long-term climate-growth relations of main tree species in the remnant dry Afromontane forests in northern Ethiopia. The aim of this study was to assess the dendrochronological potential of selected dry Afromontane tree species and to study the influence of climatic variables (temperature and rainfall) on radial growth. It was hypothesized that there are potential tree species with discernible annual growth rings owing to the uni-modality of rainfall in the region. Ring width measurements were based on increment core samples and stem discs collected from a total of 106 trees belonging to three tree species (Juniperus procera, Olea europaea p. cuspidate and Podocarpus falcatus). Thesubsp. collected samples were prepared, crossdated, and analyzed using standard dendrochronological methods. The formation of annual growth rings of the study species was verified based on successful crossdatability and by correlating tree-ring widths with rainfall. Results: The results showed that all the sampled tree species form distinct growth boundaries though differences in the distinctiveness were observed among the species. Positive and significant correlations were found between the tree-ring widths and rainfall, implying that rainfall plays a vital role in determining tree growth in the region. The study confirmed the formation of annual growth rings through successful crossdating, thus highlighted the potential applicability of dendroclimatic studies in the region. Conclusions: Overall, the results proved the strong linkage between tree-ring chronologies and climate variability in the study region, which further strengthens the potential of dendrochronological studies developing in Ethiopia, and also has great implications for further paleo-climatic reconstructions and in the restoration of degraded lands. Further knowledge on the growth characteristics of tree species from the region is required to improve the network of tree-ring data and quality of the chronology so as to successfully reconstruct historic environmental changes.

Woody species composition,structure and environmental determinants in a moist evergreen Afromontane forest,southern Ethiopia

Ethiopian moist evergreen Afromontane forests are vital for the conservation of plant diversity,including genetic pools of Coffea arabica L.However,these forests are continuously shrinking and need empirical scientific studies for their effective conservation and sustainable management.This study was,therefore,conducted to assess woody species composition,diversity,endemicity,structure,plant communities,and environmental determinants in Sirso moist evergreen Afromontane forest of southern Ethiopia.Environmental variables such as altitude,slope,aspect,disturbance levels,and geographical location were recorded for each main plots.Vegetation structure and importance value index(IVI),diversity,vegetation classification,and correlation with environmental factors were analyzed.A total of 74 woody species representing 70 genera and 34 families were identified.Seven species were endemic.Rhus glutinosa A.Rich subsp.glutinosa and Prunus africana(Hook.f.)Kalkm.were species categorized as vulnerable according to the IUCN red list category.The highest number of species was recorded for the Rubiaceae family(8),followed by Euphorbiaceae(6),and Asteraceae(6).Five plant communities were identified:Maesa lanceolata-Dombeya torrida,Galiniera saxifraga-Cyathea manniana,Vepris dainellii-Triumfetta tomentosa,Dracaena fragrans-Rytigynia neglecta,and Arundinaria alpina.The distribution of these communities depends on altitude,slope,and disturbance factors.Syzygium guineense(Wild.)DC.,Schefflera abyssinica(Hochst.ex A.Rich.)Harms,and Galiniera saxifraga(Hochst.)Bridson were species with the highest IVI,while P.africana,Cordia africana Lam.,Hagenia abyssinica(Bruce)J.F.Gmelin,Bridelia micrantha(Hochst.)Baill.,and C.arabica had the lowest.Population structure of woody species showed an inverted J-shape,a J-shape,a bell-shape,and an irregular shaped pattern.These latter three population structure revealed signs of disturbances,and were negatively correlated with altitude and slope.The study showed that the Sirso moist evergreen Afromontane forest is species rich and should be given conservation priority to maintain endemic and native species.

Living with Climate Change: Assessment of the Adaptive Capacities of Smallholders in Central Rift Valley, Ethiopia

Farms less than 2 hectares have constituted almost 90% of the total number of farms in Ethiopia. These small farms are rain fed and are vulnerable to climate change and variability extremes such as droughts. This in turn undermined the ability of smallholders’ farmers to feed themselves and the growing population. A questionnaire survey was conducted with a random sample of 355 smallholder farmers distributed in three agro-ecologies, namely, lowland, midland, and highland in central rift valley of Ethiopia (Arsi Negele district). This was supplemented with 18 focus group discussions and 30 key informant interviews. How do smallholder farmers live with climate change and variability challenges? On the basis of this question, this study has assessed the factors that determine the adaptive capacities, strategies and livelihoods of smallholders to climate change and variability;and the role of climate capacities and landscape functions for sustainable adaptation in response to climate change and variability. The results showed that even if most respondents (>95%) have the perception and intention of climate change;it was nearly 3% of them have higher adaptive capacity to adapt to climate change impacts. Adaptive capacity of smallholders and the potential impact exerted by climate change risks were negatively correlated (r = &#8722;0.134 and p < 0.02). The results showed that farmers have made some evolution in their livelihoods as an adaptation strategy. Adaptation strategies explicitly depend on adaptive capacity-human, natural, financial, social and physical resources. Indeed, the results indicated limited climate-specific and climate-relevant capacities at the local level which suggests a need to strengthen climate capacities. Moreover, it has been implicated that maintaining the landscapes, which provide landscape production functions that build the well-being and adaptive capacity of farmers, could help to sustain farmers’ livelihood and build their adaptive capacity to withstand the challenges of climate change.

Soil Bunds Effect on Soil Properties under Different Topographies of the Southwest Ethiopia

Soil erosion is a major environmental problem affecting development endeavor.Physical soil and water conservation(SWC)measures such as soil bunds are implemented to mitigate soil erosion.However,information on the effects of soil bunds on soil fertility is limited.This study was aimed to evaluate soil quality in fields with soil bunds and with no soil bunds in steep,middle and lower sloping cultivated lands as well as spatial variation of soil properties in between bunds in southwest Ethiopia.About 7-15 years old bunds and nearby cultivated fields lacking bunds were assessed.From 0 cm-20 cm soil depth,a 36 soil samples were collected.Soil texture,soil organic carbon(SOC),total nitrogen(N_(tot))and exchangeable potassium(K_(exch))were analyzed.Soil bunds showed significantly(p<0.0.5)greater clay but less sand than adjacent no-bund fields.In steep,middle,and lower slopes,concentrations of SOC and Kexch were greater in fields with soil bunds than without.Lower slope fields showed greater clay,SOC and nutrients than steep slopes.In between soil bunds,soil was more fertile at above bunds than below the bunds.In Fanta watershed,soil bunds are vital conservation measure to retain soil fertility on cultivated mountainous area.

Effects of warming,wetting and nitrogen addition on substrate-induced respiration and temperature sensitivity of heterotrophic respiration in a temperate forest soil

Soil heterotrophic respiration and its temperature sensitivity are affected by various climatic and environmental factors.However,little is known about the combined effects of concurrent climatic and environmental changes,such as climatic warming,changing precipitation regimes,and increasing nitrogen(N)deposition.Therefore,in this study,we investigated the individual and combined effects of warming,wetting,and N addition on soil heterotrophic respiration and temperature sensitivity.We incubated soils collected from a temperate forest in South Korea for 60 d at two temperature levels(15 and 20℃,representing the annual mean temperature of the study site and 5℃warming,respectively),three moisture levels(10%,28%,and 50%water-filled pore space(WFPS),representing dry,moist,and wet conditions,respectively),and two N levels(without N and with N addition equivalent to 50 kg N ha^(-1)year^(-1)).On day 30,soils were distributed across five different temperatures(10,15,20,25,and 30℃)for 24 h to determine short-term changes in temperature sensitivity(Q_(10),change in respiration with 10℃increase in temperature)of soil heterotrophic respiration.After completing the incubation on day 60,we measured substrate-induced respiration(SIR)by adding six labile substrates to the three types of treatments.Wetting treatment(increase from 28%to 50%WFPS)reduced SIR by 40.8%(3.77 to 2.23μg CO_(2)-C g^(-1)h^(-1)),but warming(increase from 15 to 20℃)and N addition increased SIR by 47.7%(3.77 to 5.57μg CO_(2)-C g^(-1)h^(-1))and 42.0%(3.77 to 5.35μg CO_(2)-C g^(-1)h^(-1)),respectively.A combination of any two treatments did not affect SIR,but the combination of three treatments reduced SIR by 42.4%(3.70 to 2.20μg CO_(2)-C g^(-1)h^(-1)).Wetting treatment increased Q_(10)by 25.0%(2.4 to 3.0).However,warming and N addition reduced Q_(10)by 37.5%(2.4 to 1.5)and 16.7%(2.4 to 2.0),respectively.Warming coupled with wetting did not significantly change Q_(10),while warming coupled with N addition reduced Q_(10)by 33.3%(2.4 to 1.6).The combination of three treatments increased Q_(10)by 12.5%(2.4 to 2.7).Our results demonstrated that among the three factors,soil moisture is the most important one controlling SIR and Q_(10).The results suggest that the effect of warming on SIR and Q_(10)can be modified significantly by rainfall variability and elevated N availability.Therefore,this study emphasizes that concurrent climatic and environmental changes,such as increasing rainfall variability and N deposition,should be considered when predicting changes induced by warming in soil respiration and its temperature sensitivity.

Effects of the nitrification inhibitor nitrapyrin and tillage practices on yield-scaled nitrous oxide emission from a maize field in Iran

Nitrification inhibitors can effectively decrease nitrification rates and nitrous oxide(N_(2)O)emission while increasing crop yield under certain conditions.However,there is no information available on the effects of nitrification inhibitors and tillage practices on N_(2)O emissions from maize cropping in Iran.To study how tillage practices and nitrapyrin(a nitrification inhibitor)affect N_(2)O emission,a split factorial experiment using a completely randomized block design with three replications was carried out in Northeast Iran,which has a cold semiarid climate.Two main plots were created with conventional tillage and minimum tillage levels,and two nitrogen(N)fertilizer(urea)management systems(with and without nitrapyrin application)were created as subplots.Tillage level did not have any significant effect on soil ammonium(NH_(4)^(+))and nitrate(NO_(3)^(-))concentrations,cumulative amount and yield-scaled N_(2)O emission,and aboveground biomass of maize,whereas nitrapyrin application showed significant effect.Nitrapyrin application significantly reduced the cumulative amount of N_(2)O emission by 41%and 32%in conventional tillage and minimum tillage practices,respectively.A reduction in soil NO_(3)^(-)concentration by nitrapyrin was also observed.The average yield-scaled N_(2)O emission was 13.6 g N_(2)O-N kg^(-1)N uptake in both tillage systems without nitrapyrin application and was significantly reduced to 7.9 and 8.2 g N_(2)O-N kg^(-1)N uptake upon the application of nitrapyrin in minimum tillage and conventional tillage practices,respectively.Additionally,nitrapyrin application increased maize biomass yield by 4%and 13%in the minimum tillage and conventional tillage systems,respectively.Our results indicate that nitrapyrin has a potential role in reducing N_(2)O emission from agricultural systems where urea fertilizers are broadcasted,which is common in Iran due to the practice of traditional farming.

Tree species diversity predicts aboveground carbon storage through functional diversity and functional dominance in the dry evergreen Afromontane forest of Hararghe highland, Southeast Ethiopia

Background:Regarding the most important ecological challenges,scientists are increasingly debating the relationship between biodiversity and ecosystem function.Despite this,several experimental and theoretical researches have shown inconsistencies in biodiversity and ecosystem function relationships,supporting either the niche complementarity or selection effect hypothesis.The relationship between species diversity,functional diversity,and aboveground biomass carbon was investigated in this study employing standing aboveground carbon(AGC)stock as a proxy measure for ecosystem function.We hypothesized that(i)effects of diversity on AGC can be transmitted through functional diversity and functional dominance;(ii)effects of diversity on AGC would be greater for functional dominance than functional diversity;and(iii)effects of functional diversity and functional dominance on carbon stock varied with metrics and functional traits.Community-weighted means(CWM)of functional traits(wood density,specific leaf area,and maximum plant height)were calculated to assess functional dominance(selection effects).As for functional diversity(complementarity effects),multi-trait functional diversity(selection effects)indices were computed.We tested the first hypothesis using structural equation modeling.For the second hypothesis,the effects of environmental variables such as slope,aspect,and elevation were tested first,and separate linear mixed-effects models were fitted afterward for functional diversity,functional dominance,and the two together.Results:Results revealed that slope had a significant effect on aboveground carbon storage.Functional diversity and functional dominance were significant predictors of the aboveground carbon storage(22.4%)in the dry evergreen Afromontane forest.The effects of species richness on aboveground carbon storage were mediated by functional diversity and functional dominance of species.This shows that both the selection effects and the niche complementarity are important for aboveground carbon storage prediction.However,the functional diversity effects(niche complementarity)were greater than functional dominance effects(selection effects).Conclusions:Linking diversity and biodiversity components to aboveground carbon provides better insights into the mechanisms that explain variation in aboveground carbon storage in natural forests,which may help improve the prediction of ecosystem functions.

Socio-ecological vulnerability to climate change/variability in central rift valley,Ethiopia

Climate change/variability and environmental degradation have increased in the central rift valley of Ethiopia,which in turn making the people inhabiting in that ecosystem more vulnerable to the impacts.The purposes of this study were to assess the vulnerability of households andagro-ecosystems to climate change and environmental degradation and the factors determining vulnerabilities in the central rift valley,Ethiopia.Data were collected between November 2014 and May 2015 by interviewing 355 respondents.This has been supplemented with focus group discussions and key informant interviews.The indicator and matrix methods were used to describe socio-ecological vulnerabilities.The resultsshowed that about 9%of the respondents were highly vulnerable to climate change/variability,and environmental degradation.Households in the lowland have the largest proportion of high vulnerable households(60%),while households in highland have the largest proportion of low vulnerable households(30%).In the lowland agro-ecology,the adaptive capacity component has contributed the largest share to household's vulnerability index to the impacts of climate change/variability and environmental degradation.The sensitivity component has higer contribution in highland agro-ecology and the exposure component in the midland agro-ecology.There were variations of income deviation between agro-ecologies that lead to variation in vulnerability of households.Household vulnerability index has shown a very light negative correlation with livelihood diversification index.The poorest households with little share of the total income distribution and with low livelihood diversity index,were the most vulnerable.The results showed that the highest exposure index on ecosystem functions and agricultural performance were in the lowland agro-ecology.This study highlighted the need to assess the social and ecological vulnerabilities in integrated approach as singling out one from the other is difficult.That is,social vulnerability impacts ecological vulnerability and vice versa.

Effect of exclosure on woody species diversity and population structure in comparison with adjacent open grazing land: the case of Jabi Tehnan district north western Ethiopia

Land rehabilitation by area exclosure was the fastest and moderate approach of recovering degraded sites.However,the effect of exclosure on woody species parameters in Jabitehnan district,north-western Ethiopia has not been investigated.Therefore,the current study was conducted(i)to assess and compare diversity,composition and density of woody species in exclosure and adjacent open lands,and(ii)to analyze population structure as well as regeneration status of woody species.A random sampling method was employed to select a total of 40 sample plots(50m*50m).A total of 8 parallel transect lines were used inside and outside the exclosure land in each site for consecutive(50m interval)plot establishment.Species diversity was 1.7 and 3.03 for WG,1.1 and 2.94 for GW open and exclosures,respectively.Population structure of woody species in exclosures of both sites exhibited an inverted J shape which indicates good regeneration status,while in adjacent open grazing land it exhibited partial bell shape.Generally,exclosure provides various biophysical benefits better than adjacent open grazing lands.It is recommended to protect degraded lands by exclosure via integrating appropriate species and convert their diversity into use so as to develop their potential benefits on land restoration.

Potential of exclosure on aboveground biomass carbon stock and ecological fitness of woody species in Jabi Tehnane district, northwestern Ethiopia

Assessment of ecological fitness of woody species across land use is critical issues in degraded land restoration.However,little is known about AGBC stored capacity,important value and distribution index of woody species grows in exclosure and adjacent open lands.Therefore,this research is aimed to(i)analyse impact of exclosure on AGBC(ii)ecological fit species.A random sampling method was employed.Forty sample plots(50m*50m)were used.AGBC stocks(mean±SE)of woody species in adjacent open grazing and exclosure land use of GW site was 0.11±0.07 and 1.24±0.27Mg ha^(-1) respectively.While in adjacent open grazing and exclosure land use of WG site,the value was 0.27±0.03 and 2.79±0.27Mgha^(-1) respectively.In both site exclosure land uses,the proportion of rare,occasional and common woody species were better than their adjacent open grazing land.Cupressus lustanica from open grazing and Vernonia auriculifera from exclosure land use of WG as well as Croton macrostachyus from open grazing and Leucaena leucocephala fromexclosure land use of GWsite were recorded as top ecologically fit species.It is recommended to protect degraded lands via integrating ecologically adapted native species and fully used their diversity to achieve the potential benefits of land restoration.

Human-climate induced drivers of mountain grassland over the last 40 years in Sidama, Ethiopia: perceptions versus empirical evidence

Background:Mountain grasslands are globally important ecosystems.They are considered as heritage sites with“outstanding values”to ecological communities by adding a further“layer and support to the existing protection measures.”However,mountain grasslands are increasingly under threat from human activities and impacts of climate change.Methods:Using satellite imagery,we studied land use/land cover(LULC)patterns between 1973 and 2015.Individual interviews consisting of 240 households for comparison and field data collection were conducted for accuracy assessment.Results:Five categories of LULC types were identified from the image classification that included forestland,grassland,shrubland,bushland,and agricultural land.Between 1973 and 2015,the forestland,grassland,and shrubland covers were declined by 15.9%,53.6%,and 41.0%,respectively.In contrast,bushland and agricultural land were increased by 169%and 647%,respectively.The overall LULC classification accuracies for the four reference years ranged from 77.6 to 86.5%with Kappa statistic of 0.69 to 0.80.The majority of respondents(92.5%)mentioned that the cover of forestland outsized the other land use land cover types followed by grassland in the past.Conclusions:The stated indicators of land use/land cover changes linked to the impact of climate change were decline in milk yield and crop production,spread of livestock diseases,degradation of grazing lands,and change in the timing of rain.The results of the study suggest that human-climate related components were major drivers of land use/land cover dynamics that demand for proper management and conservation of mountain grassland ecosystem in Sidama South Ethiopia.