Effects of Land Use on the Riparian Vegetation along the Njoro and Kamweti Rivers, Kenya

Riparian zones are valuable ecosystems. They act as the ecological engineers that improve river health by delivering a range of ecosystem functions. They play a significant role in river health and provide various ecosystem goods and services for human well-being. Currently, riparian areas are under threat due to intensive human activities such as agriculture and urbanization, which alter riparian ecosystem structure and composition. The main objective of this study was to determine the effect of adjacent land use on the structure and diversity of the riparian vegetation in the Njoro and Kamweti Rivers. Along each river, three sampling sites were selected within the major land use categories which were;forest, agricultural and built-up areas. At each site, three 70 m long transects were established perpendicular to the river. The three plots were systematically established, separated by a 5 m distance along each transect. Forest canopy cover was estimated in percentage. Njoro River riparian vegetation recorded a total of 145 plant species from 40 families where trees and shrubs were dominant in the forest area, and herbs dominated the agricultural and built-up areas. In Kamweti River riparian area, a total of 110 species from 45 families were encountered, in which trees dominated the forest area. A similar trend to the Njoro River was observed, in which herbs were dominant in the agricultural and built-up areas. In Njoro River, the Shannon diversity (H’) values ranged between 2.73 and 3.08 whereas Kamweti River riparian area values ranged from 2.59 to 3.40. At the level of P ≤ 0.05, T-Test revealed that there was no significant difference in plant abundance and diversity between the two rivers, with F = 0.53;P = 0.51 and F = 2.71;P = 0.17. Human-centered disturbances along the Njoro and Kamweti River riparian areas have affected the riparian vegetation as shown by the decrease in plant species diversities, and the change in vegetation composition and distribution across the land uses. Due to the present and probable future scenarios of the changes in riparian vegetation observed, there is a pressing need for an integrated approach for the management of riparian zones based on various components such as riparian condition assessment, policy framework, stakeholder’s participation, management practices, legislation, and awareness.

Influence of Land Use Activities on Riparian Vegetation, Soil and Water Quality: An Indicator of Biodiversity Loss, South West Mau Forest, Kenya

Watershed and riparian areas of Mau Forest Complex in Kenya are experiencing increased threats due to unsustainable land use activities geared towards economic growth amidst growing population. This study was carried out to examine effects of land use activities on riparian vegetation, soil and water quality along two major rivers (Chemosit and Kipsonoi) of South West Mau Forest (SWMF). Land use activities adjacent to these rivers and biodiversity disturbance on the riparian zone were identified and underpinned to changes on Total Nitrogen, Total Phosphorous, Potassium, Sulphur, Cadmium, Copper, Lead, Total Suspended Solids and soil Organic Carbon. Three sampling sites designated(upstream, midstream and downstream) were identified and established along each river as guided by existing land use activities represented by forest, tea plantation and mixed agricultural farming respectively. At each sampling site, a 200 m × 50 m section was systematically marked on each side of the river bank;the longest side being parallel to the river flow and divided into three belts transects each 20 m × 50 m, spaced 70 m apart. Six distinct land use activities (indigenous forest, food crop, tree and tea farming, livestock keeping and urban settlement) were identified as the major land use activities in SWMF. Plant species richness decreased and overall riparian disturbance increased from upstream (intact canopy with native vegetation) to mid-stream and downstream as epitomized by the structure, biodiversity disturbance resulting from extensive and intensive farming, intrusion of exotic species to livestock grazing and urban settlement. Variation among sampling sites in Total Suspended Solids, pH, Total Nitrogen, Phosphorus and Potassium were associated to different land use activities along the riparian zone. Total Nitrogen and water pH showed significant sensitivity to land use changes (p < 0.05). Put together these results indicate loss of biodiversity, riparian disturbance hence a need to adopt environmental-friendly land use planning and sustainable farming systems in SWMF.

Modelling the role of ground-true riparian vegetation for providing regulating services in a Mediterranean watershed

Intensive agricultural and industrial activities are often considered major sources of water contamina-tion.Currently,riparian vegetation(RV)is increasingly being promoted as a solution to balance the potentially adverse effects that agriculture may have on water quality.Nonetheless,existing RV is often overlook in recent modelling efforts,failing to capture the current amount of ecosystem services provide.Here,we used the Soil and Water Assessment Tool ecohydrological model to simulate the influence of ground-true RV on i)nutrient(nitrate and total phosphorus)and sediment exports from agricultural areas and ii)its effect for in-stream concentrations.These results are further compared against a set of hypothetical scenarios of different RV widths and different land-uses.Our results point to a great rele-vance of existing RV in controlling in-stream concentration of sediments and nutrients where pressure from agriculture is highest,preventing them to surpass limits set in the EU Water Framework Directive.On the other hand,in areas with industry discharges,the role of RV is limited and model results suggest that restoring RV would have limited impacts.We illustrate how existing RV may already provide strong but not acknowledged water quality regulation services,how these services can differ substantially between nearby streams,and that effective strategies to improve water quality using RV must acknowledge existing patterns of vegetation,land use and contamination sources.

Effects of Industrial Agriculture and Urbanization on Structure and Functional Organization of Macroinvertebrate of Coastal Streams in Cameroon

The impact of land use changes on watercourses is poorly documented in Cameroon. Therefore, this study examines the effects of agriculture and urbanization on water quality, the structure and functional organization of macroinvertebrates of streams in the coastal zone of Cameroon. Nine sampling stations including three per catchment area with different land occupations (agricultural, urban and forest) were selected. Benthic macroinvertebrates were sampled monthly from February to July 2018 and the physicochemical variables were measured simultaneously. The urban and agricultural streams showed highly polluted waters with high nutrient and suspended matter content, whereas the forest stream waters are moderately polluted. In addition, the hierarchical ascending classification indicated a proximity in water quality between the agricultural and forest streams for which the main physicochemical variables did not vary significantly. With regards to macroinvertebrates, the forest watercourse is characterized by the proliferation of pollution-sensitive taxa, high diversity indices and complex trophic structuring, indicating its good ecological status. In contrast the urban watercourse, heavily polluted is characterized by low diversity indices reflecting a simplification of the structure of stands dominated by the pollution-tolerant collector-gatherer stands. The majority of biological indices and functional feeding groups were not significantly different between the agricultural and forest streams, suggesting a less pronounced impact of agriculture on macroinvertebrates. Our results showed that, riparian vegetation even though constituted of perennial crops, reduces the effects of agricultural inputs on streams and promotes the establishment of diversified macroinvertebrate communities.

Diversity and distribution pattern of riparian plant species in the Wami River system, Tanzania

Aims The Wami River system is among the most important rivers for ripar-ian plant biodiversity conservation but it is potentially threatened by anthropogenic activities.This study was aimed to determine riparian plant species diversity and distribution patterns in relation to the anthropogenic disturbances.Methods The transect method was used to collect vegetation data.Transects were established perpendicular to the river at intervals of 50 m downstream and five plots were systematically established,sepa-rated by 5-m distance along each transect.Important Findings A total of 261 plant species in 68 families were recorded in the Wami River system with a Shannon diversity index in the range of 1.63-2.94 and a significantly decreasing trend downstream.Using the two-way indicator species analysis(TWiNSPAN),three plant communities(A,B and C)emerged based on variations in riparian plant species composition among sites.Canonical correspondence analysis(CCA)indicated that the spatial pattern of riparian plant species was significantly influenced by environmental variables.This implies that the plant species composition gradients and spatial assemblages of vegetation communities are a result of human disturbances.Because of the fragile nature of the riparian system,some species are more vulnerable than others and hence there is an urgent need for better land use planning to conserve riparian plant biodiversity in the sub-basin of Wami River.

Variation in species assemblages due to micro-topography and flow regime govern vegetation carbon stock in seasonal floodplain wetlands

Hypothesis:Variation in species assemblages due to micro-topographic features and flow regime determine vegetation carbon stock in floodplain wetlands.Material and method:We tested this hypothesis in Chatla—a tropical floodplain wetland located in northeast India.Five sampling stations characterized by contrasting micro-topographic and flow parameters were selected in the wetland for study.Species composition,assemblage pattern,and vegetation carbon stock were studied in these stations during three flood phases,i.e.,early,middle,and late flood phases following standard methods.Univariate and multivariate statistics were used to determine the relationship between the selected environmental parameters,plant species assemblages,and vegetation carbon stock of the wetland.Results:Thirty-one species of herbs and five species of shrubs were recorded from the five stations in Chatla floodplain wetland.Flow regime characterized by water flow velocity and discharge showed substantial variations across the stations.These parameters in turn are related to variations in the micro-topographic characteristics namely depth,width,and cross-sectional area of the stations.Plant species composition and abundance differed significantly with respect to micro-topography and flow regime as revealed by the cluster diagram.The canonical correspondence analysis revealed strong association of plant species assemblages with the micro-topography and flow regime within the wetland.Multiple regression analysis revealed a significant positive relationship of the vegetation carbon stock with the water discharge.Conclusions:Spatial variation in plant species diversity because of micro-topography and flow regime determines the vegetation carbon stock in floodplain wetlands.Modification of these parameters by anthropogenic activities such as mining and quarrying may potentially influence the carbon stocking potential of seasonal floodplain wetlands.Therefore,appropriate measures should be taken to maintain the integrity of the natural topographic features of such wetlands.

The influence of disturbance on driving carbon stocks and tree dynamics of riparian forests in Cerrado

Aims Riparian forests in the Brazilian Cerrado,also known as gallery forests,are very heterogeneous in structure,species composition and ecological features due to strong and abrupt variations of soil,hydrological and topographic properties.However,what are the variables driving forest carbon stock and productivity,mortality and recruitment in disturbed gallery forests?Methods We used 36 permanent plots data from a gallery forest in the Brazilian Cerrado.We investigated how tree community dynam-ics vary in a gallery forest on two contrasting disturbance levels-logged and non-logged-across a topographic gradient intrinsically related to differences in moisture conditions,edge effects,as well as soil fertility and texture.Important Findings Soil variables were reduced into principal components and we used structural equation modelling to disentangle covarying variables.We also included carbon stocks as a determinant variable of dynamics rates.Logged forest had 50%higher productivity than non-logged forest and streamside forest had aboveground carbon stocks 70%higher than the forest edge.Both logging and natural disturbance drove variation in the carbon stocks which contributed to shaping productivity and recruitment rates.Distance from the river also drove mortality and carbon stock rates.Areas with high-carbon stocks favoured higher competition and lessened produc-tivity and recruitment rates.Although soil fertility and texture are considered crucial components shaping forest dynamics,there was no clear influence of those variables on the present forest,probably because the strong effects of soil moisture,forest edge and distur-bance disrupted the correlation between soil and forest dynamics.

Flow dynamics and sediment transport in vegetated rivers:A review

The significance of riparian vegetation on river flow and material transport is not in dispute.Conveyance laws,sediment erosion and deposition,and element cycling must all be adjusted from their canonical rough-wall boundary layer to accommodate the presence of aquatic plants.In turn,the growth and colonization of riparian vegetation are affected by fluvial processes and river morphology on longer time scales.These interactions and feedbacks at multiple time scales are now drawing significant attention within the research community given their relevance to river restoration.For this reason,a review summarizing methods,general laws,qualitative cognition,and quantitative models regarding the interplay between aquatic plants,flow dynamics,and sediment transport in vegetated rivers is in order.Shortcomings,pitfalls,knowledge gaps,and daunting challenges to the current state of knowledge are also covered.As a multidisciplinary research topic,a future research agenda and opportunities pertinent to river management and enhancement of ecosystem services are also highlighted.