Plant species composition and diversity depending on piospheres and seasonality in the southern rangelands of Kenya

Introduction:Scarcity of water in the rangelands of Kenya has led to the introduction of piospheres.Previous research has however produced contrasting results on the effects of piospheres and seasonality on ShannonWiener’s diversity index,and therefore,this information is still deficient.In this study,the impact of these piospheres on plant species composition,diversity,and richness was assessed.Methods:Vegetation sampling was done during both the long rains(April)and the dry season(August).Three piosphere types(dam,trough,and a seasonal river)were studied using 0.25 m2 quadrats to sample vegetation at intervals of 20 m along 100-m transects.Four 100-m transects were used per piosphere(north,east,south,and west directions).Shannon-Wiener’s diversity index was used to determine species richness and composition.Twoway ANOVA was used to determine if piospheric distance had an effect on species diversity,richness,and evenness using GenStat 15th edition.Results:A total of 22 grasses and 29 forbs were recorded in the study area.The most abundant grasses near the piospheres were Eragrostis tenuifolia(12.9%)and Cynodon dactylon(10.6%).E.tenuifolia is an increaser species and was therefore most abundant in areas of severe grazing while C.dactylon has been known to be tolerant to grazing.The most abundant forbs were Crotalaria brevidens(37.5%).The Shannon-Wiener diversity index significantly increased(F=25.07,P=0.001)with distance from the three piospheres owing to the high grazing intensity near the piospheres and was significantly different between piospheres,being higher(F=10.05,P=0.001)at 20 m from the river(1.2±0.1)compared to a similar distance from the dam(0.9±0.1)and the trough(0.8±0.2).This was probably because the trough was smaller in size compared to the other piospheres,thereby concentrating more grazing animals per unit area and causing a greater impact on plant species.Conclusions:The study demonstrated that species diversity,richness,and evenness were low near the piospheres due to heavy grazing.Similarly,the lowest species diversity,richness,and evenness were recorded near the trough compared to the dam and the river.This study therefore recommends that range reseeding and rest period be done to rehabilitate degraded areas and facilitate plant regeneration.Larger piospheres should also be used to minimize animal impact per unit area.

Effect of piospheres on physio-chemical soil properties in the Southern Rangelands of Kenya

Introduction:Water-based interventions haphazardly introduced in the drylands of Kenya have led to the introduction of piospheres used as concentration mounts.Not much is known about the effect of these piospheres on soil physio-chemical properties,especially in the Kenyan rangelands where the government and other development agencies have created piospheres aimed at curbing water shortages and sustaining livestock production.The study assessed the effect of piospheres on soil physio-chemical characteristics in the southern rangelands of Kajiado,Kenya,in order to provide evidence-based insights that will be useful in guiding future water interventions.Methods:Soil samples were collected within 0.25-m2 plots at 20-m intervals along 100-m transects from three piospheres(a dam,a trough,and a seasonal river).Two-way ANOVA was used to determine if there were significant differences in soil parameters between piospheric distances.Results:Soil bulk density significantly different between piospheric distances(F=22.25,P=0.001)and piospheres(F=13.10,P=0.002),being highest at 20 m from the trough(1.1–1.21 gcm−3)relative to a similar distance from the dam(1.01–1.20 gcm−3)and the river(1.1–1.17 gcm−3).On the other hand,mean soil aggregate stability significantly increased(F=66.89,P=0.001)with piospheric distance,being lowest at 20 m from the trough(43.9–46.2%),the dam(43.1–48.9%),and the river(46.6–47.5%).Conclusions:High soil bulk density and consequent low soil porosity,hydraulic conductivity,and moisture content demonstrated that grazing was high near the piospheres.It is recommended that livestock should be herded away from the piospheres after drinking water to ensure that grazing livestock spend less time near the piospheres if reduced soil compaction is to be realized.Piospheres should also be better planned and placed at landscape level to exploit landscape heterogeneity.

Tracking desertification on the Mongolian steppe through NDVI and field-survey data

Changing environmental and socio-economic conditions make land degradation,a major concern in Central and East Asia.Globally satellite imagery,particularly Normalized Difference Vegetation Index(NDVI)data,has proved an effective tool for monitoring land cover change.This study examines 33 grassland water points using vegetation field studies and remote sensing techniques to track desertification on the Mongolian plateau.Findings established a significant correlation between same-year field observation(line transects)and NDVI data,enabling an historical land cover perspective to be developed from 1998 to 2006.Results show variable land cover patterns in Mongolia with a 16%decrease in plant density over the time period.Decline in cover identified by NDVI suggests degradation;however,continued annual fluctuation indicates desertification
irreversible land cover change
has not occurred.Further,in situ data documenting greater cover near water points implies livestock overgrazing is not causing degradation at water sources.In combination of the two research methods
remote sensing and field surveys
strengthen findings and provide an effective way to track desertification in dryland regions.