Impact of exclosures on wood biomass production and fuelwood supply in northern Ethiopia

In the Ethiopian highlands, communal grazing lands are one of the major land uses, and are source of livelihood for the rural people. Free and uncontrolled grazing in the communal grazing lands is the dominant grazing system. The traditional uncontrolled and free grazing system has caused severe degradation of the grazing lands. As a result, communities have started to establish exclosures and support the restoration of degraded communal grazing lands. Studies have shown that exclosures are effective to restoring degraded communal grazing lands and improving ecosystem services. However, studies that investigate the changes in aboveground biomass following the establishment of exclosures and compare it with fuelwood demand of the beneficiaries in our study area is lacking. Therefore, our study aimed at:(1) quantifying yearly biomass accumulation in exclosures and compare it to fuelwood demand of households that manage the exclosures;(2) assessing household energy sources and their consumption levels. To monitor changes in biomass production with over time, replicated(n = 3) 5 and10 year-old exclosures were sampled. To investigate fuelwood sources and consumption patterns, household surveys, key informant interviews and focus group discussion were conducted. Our results demonstrated that total biomass production increased with exclosure age. In both exclosure, biomass production from Vachellia etbaica was significantly(p \ 0.05) greater than that from Euclea.racemosa. Average daily fuelwood consumption per person was(0.63 ± 0.2) kg day^(-1). This means that the total biomass(27.5 Mg year^(-1)) obtained from 114.6 ha of exclosures covers only 9.4% of yearly fuelwood demand of the residents who manage the sampled exclosures. Nearly all respondents(95%) confirmed that they travel more than10 km day^(-1) to gather fuelwood from surrounding degraded forest patches. We recommend plantings of fast growing native tree species within exclosures and around homesteads to provide a sustainable fuelwood supply and using improved stoves to address the problem of fuelwood shortage. District agricultural offices could provide seedlings of native plant species, while communities provide unpaid labour for planting and managing plantations.

Carbon sequestration in the total and light fraction soil organic matter along a chronosequence in grazing exclosures in a semiarid degraded sandy site in China

Horqin Sandy Land is a fragile, seriously desertified region located in Inner Mongolia of China. Over- grazing is one of the primary drivers of desertification in this region. We investigated whether the establishment of grazing exclosures in areas with active sand dunes enhances soil carbon （C） sequestration and benefits soil re- covery. The results showed that soil organic C storage was 1.4, 1.9, and 3.5 times, and light fraction C storage was 2.3, 3.2, and 4.4 times in the 100-cm topsoil after 7, 12, and 25 years of grazing exclusion, respectively, compared to the case in active sand dunes. The light fraction of soil played an important role in soil C sequestration, although it might not change rapidly to provide an early indication of how soil C is increasing in response to grazing exclusion. The results indicated that soils could potentially sequester up to 13.8 Mt C in 25 years if active sand dunes in the study area were to be protected by exclosures. This corresponds to 12.8% of the estimated carbon loss （107.53 Mt） that has been associated with desertification over the past century in the Horqin Sandy Land. Our results suggested that exclosures have the capacity to increase soil C sequestration; however, decades will be required for soil C to recover to historical grassland levels observed prior to desertification.

Effect of exclosure ages on woody plant structure,diversity and regeneration potential in the western Tigray region of Ethiopia

Exclosure is a method of rehabilitating degraded lands by protecting them from the interference of animals and from human encroachment, and is used to regenerate native vegetation as a way to reduce soil erosion, increase rain water infiltration and provide fodder and woody biomass in degraded grazing lands. Therefore, we studied woody plant structure, diversity and regeneration potentials in 5-and 10-year grazing exclosures in comparison with open grazed sites in a semi-arid environment. Data on species diversity, abundance, structure, basal area, frequency, density, and regeneration status were collected from 270 sample plots. Forty-one woody species representing 20 families were identified, with 18, 28 and 38 species found in open grazed areas, and in 5-and 10-year grazing exclosures, respectively. The 10-year grazing exclosures had a higher(P <0.05) species richness and plant densities compared to the 5-year grazing exclosures and the open grazed areas. The population structure and regeneration status of woody species in both grazing exclosures showed an inverted J-shape, indicating a healthy regeneration status, whereas hampered regeneration was observed in open grazed areas. The establishment of grazing exclosures had positive effects in restoring woody plant diversity and improving vegetation structure and regeneration potentials of degraded grazing lands.

Effect of exclosure on dryland woody species restoration in northeastern Amhara,Ethiopia

In Ethiopia,among many restoration efforts to reverse deforestation and land degradation,area exclosure is one of the most common practices to restore secondary forests with assisted natural regeneration.The present study in the S ekota district,northeastern Amhara region,Ethiopia evaluated the influence of areas exclosures on woody species diversity,population structure and regeneration status.A total of 36 and 27 quadrats,each 20 m×20 m,were used to collect data in exclosures and non-exclosures,respectively.Within quadrats,four 5 m×5 m and 2 m×2 m quadrats at the corners were used to sample saplings and seedlings,respectively.In exclosures,35 woody species representing21 families and 29 genera were recorded;19 woody species representing 13 families and 13 genera were recorded in the non-exclosure.Acacia etbaica was the most dominant species in the two land-uses.The Shannon diversity index was1.77±0.46 in exclosures and 1.39±0.46 in non-exclosures.Shannon and Simpson diversity indices showed a significant difference between the two land-uses(p<0.01).The regeneration status of all wood species in exclosures was good,only fair in non-exclosures.Area exclosures have thus played a great role in the restoration of degraded lands by improving vegetation diversity and regeneration status.The least dominant woody species should be maintained through active restoration.Continuous follow-up,maintenance of soil water conservation structure to improve soil fertility will further help enhance the woody species diversity and abundance.

Exclosures restored the density and root colonization of arbuscular mycorrhizal fungi in Tigray, Northern Ethiopia

Introduction:Exclusion of grazing animals and tree plantations were among the methods used for the restoration of degraded lands in tropical semiarid areas.Exclosures can foster secondary forest succession by improving soil conditions and modifying microclimate for understory growth.This paper compared the arbuscular mycorrhizal fungi(AMF)spore density,root colonization of woody plants and soil chemical properties under exclosure with increasing age,and grazing land at different slope positions.Methods:The study was conducted in northern Ethiopia from 12 exclosure sites paired each with adjacent grazing land in total from 24 sites with four treatments replicated three times.In the entire study,216 plots were examined of which 108 were in exclosures and 108 in communal grazing lands.There were four age classes and three slope positions in each of the land uses.Composite soil and root samples were collected using nested plots measuring 100m2 from four sides of 1763 plants for spore enumeration and root colonization.Soils for chemical properties were collected from the four corners and center of 5 m×5 m plots.Results:All the 61 woody plant species that belong to 41 families were colonized by AMF.Spore density and root colonization were significantly higher in exclosures as compared to grazing land and increased with increasing ages of exclosures.Foot slope had significantly higher spore density and root colonization than middle and upper slopes.Soil chemical properties were significantly higher in the exclosure,oldest age of exclosure,and foot slope position(except P).AMF spore density and root colonization were significantly positively correlated with soil chemical properties.Conclusions:Exclosures are helpful to restore the AMF spore density and root colonization of woody species and soil fertility.

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.

Exclosure land management for restoration of herbaceous species in degraded communal grazing lands in Southern Tigray

Herbaceous species contribute to the largest proportion of the fodder.Despite the profound benefits obtained,anthropogenic disturbances are hindering its development.On the other hand,to ensure the sustainability of herbaceous species,communities and governments have been putting efforts in managing herbaceous species through the establishment of area exclosure(AE).Thus,the main importance of this research paper is to provide information about the role of AE on the restoration of herbaceous species.The objective of this study was to assess the effect of restoration on the herbaceous species following AE established on communal grazing land(CGL).A total of 124 and 73 quadrats of 1×1m^(2) size were laid down at 50 m intervals along parallel transects at AE and CGL,respectively,and data were analyzed by t-test unequal variances using R-software.AE displayed higher plant species richness and diversity than the CGL and showed a significant difference(p<0.001).Similarly,the AE had significantly(p<0.001)higher forage biomass than the CGL.In general,herbaceous species diversity index and species richness were significantly(p<0.001)higher in the AE compared to the CGL.The study concluded that effective AE has the potential to enhance the restoration of herbaceous species and hence forage productivity.

Impact of grazing on soil, vegetation and ewe production performances in a semi-arid rangeland

Controlled grazing is considered a good management strategy to maintain or increase the live weight of livestock and to reduce vegetation degradation of rangelands. The present study investigated soil characteristics, aboveground vegetation biomass dynamics and controlled grazinginduced changes in the live weight of local ewes in the semi-arid rangeland of Ahmadun, Ziarat, Balochistanprovince of Pakistan. An area of 115 ha was protected from livestock grazing in April 2014. In June 2015, soil characteristics within 0-30 cm depth i.e. soil organic matter(SOM), mineral nitrogen, p H and texture in controlled and uncontrolled grazing sites were assessed. Aboveground vegetation biomass measured in early(June) and late summer(August) in 2015 and 2016. The nutritional value i.e. crude protein, phosphorus(P), neutral detergent fiber(NDF), acid detergent fiber(ADF), calcium(Ca), magnesium(Mg) and potassium(K) of dominantplant species were assessed at the beginning of experiment in 2015. Vegetation cover of controlled and uncontrolled grazing sites was also measured during the two years of the study period using the Veg Measure software. From June to November in2015 and 2016, controlled and uncontrolled livestock grazing sites were grazed on a daily basis by local ewes with a stocking rate of 2 and 1 head ha^(-1) respectively. Results reveal that the organic matter contents of coarse-textured, slightly alkaline soil of the study site were in the range of 9.4-17.6 g kg^(-1) soil and showed a strong positive correlation with aboveground vegetation biomass. The biomass of plants was 56.5% and 33% greater at controlled than uncontrolled grazing site in 2015 and 2016 respectively and plant cover was also higher at controlled than uncontrolled grazing site in both years The nutrient contents were significantly(P<0.05)lower in grasses than shrubs. In both years, the controlled grazing increased the weight gain of ewes about two folds compared to the uncontrolled grazing.The results indicate that controlled grazing improved the vegetation biomass production and small ruminant productivity.

Investigation of rangeland indicator species using parametric and non-parametric methods in hilly landscapes of central Iran

This study aimed to identify indicator species and explore the most important environmental and management variables contributing to vegetation distribution in a hilly upper dam landscape in Zagros Mountain chain, Iran. A stratified random sampling method was used to collect topographic, edaphic, management and vegetation data. The density and cover percentage of perennial species were measured quantitatively. Indicator species were identified using the two-way indicator species analysis. Besides calculating physiognomic factors in sample sites, 24 soil samples were collected from 0 to 30 cm of soil depth and analyzed in terms of gravel percentage, texture, saturation moisture, organic matter, pH and electrical conductivity in saturation extract, lime percentage, soluble calcium and magnesium, available phosphorus, Cation Exchange Capacity(CEC) and soluble sodium and potassium. Multivariate techniques including Canonical Correspondence Analysis and Multi-Dimensional Scaling were used to explore the relationships of species with environmental and management variables. Seven plants were identified as indicator species due to being significantly correlated with management(grazing or non-grazing) and edaphic variables such as CEC, soil texture, pH, CaCO3 percentage and physiographic variable including slope, elevation, and convex and concave formations(p < 0.05). Overall, overgrazing and its subsequent effects on soil characteristics, loss of vegetation cover and trampling were found as the major causes of deterioration. Sustainable and integrated management practices such as the implementation of appropriate grazing systems were suggested to enhance soil quality and reduce the accelerated erosion in upper dam zones.

Stand Structure, Diversity and Regeneration Status of Woody Species in Open and Exclosed Dry Woodland Sites around <i>Molapo</i>Farming Areas of the Okavango Delta, Northeastern Botswana

Stand structure, diversity and regeneration status of woody species were investigated in open and exclosed dry woodland sites in Island Safari, Shorobe and Xobe, northeastern Botswana. A total of 105, 111 and 130 quadrats, measuring 20 × 20 m each, were laid down along parallel line transects in the three sites, respectively, to collect data. A total of 47 species, representing 16 families and 24 genera, were recorded in the study sites. Of these, 33 species representing 13 families and 20 genera, 41 species representing 15 families and 23 genera and 27 species representing 10 families and 14 genera were encountered in Island Safari, Shorobe and Xobe, respectively. The most diverse family was Fabaceae followed by Combretaceae and Tiliaceae at all the three sites. The most diverse genus was Acacia, followed by Combretum and Grewia. The diversity of woody species in the study sites were 2.18, 2.15 and 1.5 in Shorobe, Island Safari and Xobe, respectively, while their corresponding evenness values were 0.6, 0.6 and 0.5, respectively. The mean densities of the woody species encountered in Island Safari, Shorobe and Xobe were 2629, 4271 and 2745 individuals ha&#451, respectively. The five densest species were Colophospermum mopane, Dichrostachys cinerea, Acacia tortilis, Philenoptera violacea and Terminalia prunioides in Island Safari, C. mopane, A. tortilis, A. erioloba, P. violacea and D. cinerea in Shorobe and Acacia mellifera, A. tortilis, P. nelsii, A. luederitzii and A. erubescens in Xobe. The highest important value index values were exhibited by C. mopane, D. cinerea, A. tortilis, P. violacea and T. prunioides in Island Safari, C. mopane, A. erioloba, A. tortilis, P. violacea and C. imberbe in Shorobe, and A. mellifera, A. tortilis, P. nelsii and A. luederitzii in Xobe. The alarming result was the fact that 71%, 80% and 85% of the woody species recorded in Island Safari, Shorobe and Xobe, respectively, exhibited hampered regeneration and, thus, unhealthy population structures. Therefore, there is an urgent need to address the observed unhealthy population structures of the woody species through investigation of the major causes of their hampered regeneration, and also designing measures that will facilitate natural and artificial regeneration of these species at the three study sites.

Response of understory vegetation over 10 years after thinning in an old-growth cedar and cypress plantation overgrazed by sika deer in eastern Japan

Background： Forest management strategies such as thinning have long been used to enhance ecosystem functions, especially in plantations.Thinning in plantations with high deer density, however, may not yield a desired increase in understory vegetation because deer graze on germinating plants after thinning.Here, we examine the changes in understory vegetation after thinning in plantations that have been overgrazed by sika deer to provide insight into the effects of thinning on ecosystem functions such as soil conservation and biological diversity.Methods： We conducted our survey in the Tanzawa Mountains of eastern Japan.We surveyed the change in understory vegetation within and outside of three deer exclosures on a single slope with three levels of understory vegetation cover： sparse（1%, exclosure ＂US＂）, moderate（30%, exclosure ＂MM＂）, and dense（80%, exclosure ＂LD＂） over10 years after a 30% thinning of an old-growth cedar and cypress plantation which was overgrazed by sika deer.Results： Understory vegetation cover, biomass and species richness increased within and outside the ＂US＂ and＂MM＂ exclosures after thinning, and biomass was greater within than outside the exclosures at 10 years after thinning.Unpalatable species dominated both ＂US＂ and ＂MM＂ exclosures before thinning, and trees and shrubs dominated within the exclosures over time after thinning.In contrast, unpalatable, grazing-tolerant, perennial,and annual species increased outside the ＂US＂ and ＂MM＂ exclosures.No noticeable changes were observed within and outside the ＂LD＂ exclosure when compared with the ＂US＂ and ＂MM＂ exclosures.Conclusions： Our results suggest that thinning a stand by 30% based on volume resulted in an increase in understory vegetation cover mainly composed of both unpalatable and grazing-tolerant species in a plantation forest where understory vegetation is sparse or moderate and sika deer density is high.We emphasize that establishing deer exclosures or controlling deer is essential to maintaining similar understory vegetation both within and outside exclosures.

Herbivory Effects on <i>Ephedra</i>spp. in the Chihuahuan Desert

Two species of Ephedra: E. trifurca and E. torreyana inhabit shrub and grassland habitats in the northern Chihuahuan Desert. E. torreyana is limited to black grama grasslands where grasses are taller than the shrub. E. torreyana is heavily browsed by vertebrates and E. trifurca is browsed during some years. We established an experiment with cylindrical exclosures that excluded rabbits and rodents, rabbits but accessible to rodents, for comparison with E. torreyana plants available to all herbivores. Plants accessible to all vertebrate herbivores were significantly smaller with shorter stem lengths than plants in exclosures. We concluded that E. torreyana in black grama grassland are largely hidden from vertebrate herbivores and that intense herbivory reflects the degraded state of the study site which makes the E. torreyana evergreen shrubs apparent to vertebrates.

Defaunation Increases the Survivorship of the Palm Astrocaryum gratum in a Submontane Tropical Forest

Overhunting of mammals may negatively affect plant populations though indirect impacts on mammal-plant interactions such as herbivory. In this paper, we examined how hunting of terrestrial mammals impacts the survival of seedlings and juveniles of the palm Astrocaryum gratum. To determine A. gratum seedling survivorship patterns, an experiment with seedlings in 25 × 250-m plots exclosures and different levels of mammal species presence was conducted: all mammals, only Tayassu peccari potentially a major seedling predator and no animals excluded. More than 50,600 non-adults were measured for 27 months. We replicated these treatments in three forest categories: 1) no hunting, with an intact mammal community, 2) a lightly hunted region and 3) a heavily hunted area. Seedling survivorship under natural non-experimental conditions was highest in the heavily hunted (S(T) = 0.72), lower in moderate and lowest in unhunted forests. Experiments revealed that T. peccari was the main agent of palm seedling mortality and the most important factor determining seedling and juvenile survivorship, for example they caused the 84.61% deaths of the seedlings in unhunted forests. Thus, T. peccari feeding habits can influence forest dynamics and forest structure. T. peccari was also susceptible to hunting pressure and as the main seed and seedling predator in the system, its extinction should affect the survivorship and distribution of A. gratum in forests.

Long-term changes in biological soil crust cover and composition

Introduction:Communities change over time due to disturbances,variations in climate,and species invasions.Biological soil crust communities are important because they contribute to erosion control and nutrient cycling.Crust types may respond differently to changes in environmental conditions:single-celled organisms and bryophytes quickly recover after a disturbance,while lichens are slow growing and dominate favorable sites.Community change in crusts has seldom been assessed using repeated measures.For this study,we hypothesized that changes in crust composition were related to disturbance,topographic position,and invasive vegetation.Methods:We monitored permanent plots in the Columbia Basin in 1999 and 2010 and compared changes in crust composition,cover,richness,and turnover with predictor variables of herbivore exclosure,elevation,heat load index,time since fire,presence of an invasive grass,and change in cover of the invasive grass.Results:Bryophytes were cosmopolitan with high cover.Dominant lichens did not change dramatically.Indicator taxa differed by monitoring year.Bryophyte and total crust cover declined,and there was lower turnover outside of herbivore exclosures.Lichen cover did not change significantly.Plots that burned recently had high turnover.Increase in taxon richness was correlated with presence of an invasive grass in 1999.Change in cover of the invasive grass was positively related to proportional loss and negatively related to gain.Conclusions:Composition and turnover metrics differed significantly over 11 years,though cover was more stable between years.This study can be a baseline for assessing change in crust composition due to anthropogenic influences.

Response of endemic afroalpine rodents to the removal of livestock grazing pressure

The Bale Mountains of Ethiopia represent the world＇s largest continuous extent of afroalpine habitat. With a peak combined density of over 8000 individuals/km2, the endemic giant mole rat Tachyoryctes macrocephalus, Blick＇s grass rat Arvi- canthis blicki and the brush-furred mouse Lophuromys melanonyx are the dominant wild herbivores within this ecosystem and may be affected by the presence of high densities of domestic livestock. The purpose of this study was to establish whether these endemic rodent populations could respond to the removal of grazing pressure inside three 0.25 hectare livestock exclosures （paired with grazed control plots） and to determine whether such response was mediated through concomitant changes in the vegetation structure. We hypothesised that livestock grazing negatively affects endemic rodent populations through competition or increased predation risk and we predicted an increase in rodent biomass following the removal of grazing pressure. We found no evidence of rodent populations responding to the removal of livestock after fourteen months. The short-term nature of the ex- perimental design, environmental fluctuations and the ecosystem＇s inherent stochasticity may explain the apparent lack of a sig- nificant response. However, while this study is inconclusive, it emphasises the need for more long-term experimental investiga- tions to assess the effects of domestic grazers on vegetation and on dependent communities. The effects of rapidly increasing livestock numbers in the Bale Mountains will require continued close monitoring of vegetation and endemic animal communities as the afroalpine is altered by external biotic and abiotic forces .

Resource availability and plant diversity explain patterns of invasion of an exotic grass

Aims in this study,we examine two common invasion biology hypotheses-biotic resistance and fluctuating resource availability-to explain the patterns of invasion of an invasive grass,Microstegium vimineum.Methods We used 13-year-old deer exclosures in great smoky mountains National Park,USA,to examine how chronic disturbance by deer browsing affects available resources,plant diversity,and invasion in an understory plant community.using two replicate 1 m2 plots in each deer browsed and unbrowsed area,we recorded each plant species present,the abundance per species,and the fractional per-cent cover of vegetation by the cover classes:herbaceous,woody,and graminoid.For each sample plot,we also estimated overstory canopy cover,soil moisture,total soil carbon and nitrogen,and soil pH as a measure of abiotic differences between plots.Important Findings We found that plant community composition between chronically browsed and unbrowsed plots differed markedly.Plant diversity was 40%lower in browsed than in unbrowsed plots.at our sites,diver-sity explained 48%and woody plant cover 35%of the variation in M.vimineum abundance.in addition,we found 3.3 times less M.vimineum in the unbrowsed plots due to higher woody plant cover and plant diversity than in the browsed plots.a parsimonious explanation of these results indicate that disturbances such as herbivory may elicit multiple conditions,namely releasing available resources such as open space,light,and decreasing plant diversity,which may facilitate the proliferation of an invasive species.Finally,by testing two different hypotheses,this study addresses more recent calls to incorporate multiple hypotheses into research attempting to explain plant invasion.

Carbon stocks and sequestration potential of dry forests under community management in Tigray, Ethiopia

Introduction:Forests form a major component of the carbon(C)reserves in the world’s ecosystems.However,little is known on how management influences C stocks of woody vegetation,particularly in dry areas.We developed regression models for two dominant tree species to predict C stocks and quantified the potential of community managed forests as C sinks.Methods:Plots were randomly selected from community-managed natural forest,herbivore exclosures,and from communal grazing land.Tree and shrub biomass were estimated using a regression model on the most dominant woody species while herbaceous biomass was determined using destructive sampling.Results:The simplest model,based on only one single predictor variable,showed a good fit to the data for both species(Juniperus procera and Acacia abyssinica).Diameter at breast height(r2>0.95)was a more reliable predictor than height(r2>0.54),crown diameter(r2>0.68)(p<0.001).The C content of the total biomass for the managed natural forest and the exclosure were estimated as,58.11 and 22.29 Mg ha−1,respectively,while that for the grazing land was 7.76 Mg ha−1,and the mean carbon content between the three land uses were significantly different(p<0.05).Conclusions:We conclude that forests managed by the community have a high potential for C sequestration and storage and their conservation should be promoted.

Effects of grassland management, endophytic fungi and predators on aphid abundance in two distinct regions

Aims Fungal endophytes of cool-season grass species produce alkaloids toxic to herbivores,affecting food webs in agricultural and natural ecosystems.Field studies about the effects of endophytes on herbi-vores are rare and show contradictory results,leading to uncertain conclusions about the nature of endophyte-grass symbiosis.We asked whether the environmental contexts of local and regional scales and predation could modify the effects of endophytes on herbivores.Methods In a full factorial field experiment,we quantified the abundance of the aphid species Rhopalosiphum padi on the potted host grass Lolium perenne,which was either infected or uninfected with the endophytic fungus Neotyphodium lolii.Predators were either excluded or had free access to the pots with the aphids.One hun-dred and sixty grass pots were located in two regions on altogether 40 grassland sites,half of the sites intensively and half extensively managed.We tested the importance of endophyte infection,study region,management intensity of grasslands,predation and all two-way interactions on aphid abundance.Important Findings Endophyte infection reduced aphid abundance significantly in one study region only.In both regions,we found that the impacts of aphidophagous predators and grassland management intensity on aphid abundance were substantially stronger and more consistent than that of endophytes on aphid abundance.Pots excluding preda-tors and pots placed on extensive grasslands contained higher aphid abundance.The impact of predators and management on aphid abundance were not modified by the endophyte.We conclude that the effect of endophytes on herbivores can be weak in field experi-ments and depends on environmental context at a regional scale.Hence,more field research efforts are necessary to detect the rela-tive importance of endophytes and the environmental context on biotic interactions in ecosystems.