Papyrus Vegetation Research Articles

Effect of habitat disturbance on distribution and abundance of Papyrus endemic birds in Sio Port Swamp, Western Kenya

Wanyonyi SN, Mwangi EM, Gichuki N. 2018. Effect of habitat disturbance on distribution and abundance of Papyrus endemic birds in Sio Port Swamp, Western Kenya. Bonorowo Wetlands 2: 49-60. Papyrus (Cyperus papyrus) swamps are found patchily around the shores of Lake Victoria mainly along river inflows. The objective of this study was to investigate the distinct forms of habitat disturbance and their implications on the distribution and abundance of papyrus endemic birds. Data on bird counts, habitat quality, and types of disturbance were collected for six months, from October 2013 to March 2014. Total bird counts were established using Timed Species Count (TSC) and playback call technique at every fixed point. The researcher waited for 1 minute, calls of the study species were played to elicit a response of the secretive papyrus endemic birds. The number of each bird's species seen or heard within a radius of 25 meters was recorded for the next 9 minutes before transferring to the next point count. Habitat quality such as height, density, and level of maturity was determined in 1 m2 plots along transverse transects. Opportunistic observations were made to establish forms of disturbance present during vegetation and bird surveys. Papyrus endemic birds were highly distributed in sites with pure papyrus (55.58%) than in places with mixed plants (44.42%). The abundance of three endemic birds, White-winged Swamp-warbler, Papyrus Gonolek, and Northern Brown-throated Weaver, was significantly different in mixed and pure papyrus sites. However, the abundance of Greater Swamp-warbler was not significantly different in mixed and pure papyrus sites in Sio Port Swamp during the study period. Forms of habitat disturbance established were vegetation clearing and invasion by terrestrial and aquatic plants. As many as 76.47% of papyrus vegetation were young and regenerated (0-2 m high), 19.65% were immature papyruses (2-4 m) whereas 3.88% were tall mature papyruses (4-6 m high). The abundance of papyrus endemic birds was positively and significantly correlated with the density of vegetation in height ranging from 4-6 m. Thus, any change in papyrus density changed the abundance of papyrus endemic birds. Advance management of papyrus clearing is necessary for the long-term conservation of biodiversity.

Clonal growth strategy, diversity and structure: A spatiotemporal response to sedimentation in tropical Cyperus papyrus swamps.

Land degradation and soil erosion in the upper catchments of tropical lakes fringed by papyrus vegetation can result in a sediment load gradient from land to lakeward. Understanding the dynamics of clonal modules (ramets and genets) and growth strategies of plants on such a gradient in both space and time is critical for exploring a species adaptation and processes regulating population structure and differentiation. We assessed the spatial and temporal dynamics in clonal growth, diversity, and structure of an emergent macrophyte, Cyperus papyrus (papyrus), in response to two contrasting sedimentation regimes by combining morphological traits and genotype data using 20 microsatellite markers. A total of 636 ramets from six permanent plots (18 x 30 m) in three Ethiopian papyrus swamps, each with discrete sedimentation regimes (high vs. low) were sampled for two years. We found that ramets under the high sedimentation regime (HSR) were significantly clumped and denser than the sparse and spreading ramets under the low sedimentation regime (LSR). The HSR resulted in significantly different ramets with short culm height and girth diameter as compared to the LSR. These results indicated that C. papyrus ameliorates the effect of sedimentation by shifting clonal growth strategy from guerrilla (in LSR) to phalanx (in HSR). Clonal richness, size, dominance, and clonal subrange differed significantly between sediment regimes and studied time periods. Each swamp under HSR revealed a significantly high clonal richness (R = 0.80) as compared to the LSR (R = 0.48). Such discrepancy in clonal richness reflected the occurrence of initial and repeated seedling recruitment strategies as a response to different sedimentation regimes. Overall, our spatial and short-term temporal observations highlighted that HSR enhances clonal richness and decreases clonal subrange owing to repeated seedling recruitment and genets turnover.

The potential use of papyrus (Cyperus papyrus L.) wetlands as a source of biomass energy for sub‐Saharan Africa

AbstractFour of five people in sub‐Saharan Africa rely on the traditional use of solid biomass, mainly fuelwood, for cooking. In some areas, the current rate of fuelwood consumption will exhaust biomass reserves within the next decade or two. A largely unrecognized source of biomass are tropical wetland ecosystems which have been shown to be some of the most productive ecosystems globally, exhibiting rates of net primary productivity comparable with high‐input, intensively managed agricultural systems. Papyrus (Cyperus papyrus L.) is an emergent sedge with C4 photosynthesis which is native to the wetlands, river valleys and lakes of central, eastern and southern Africa. The mean standing dry matter of culms and umbels measured at a number of locations throughout East Africa is 38.3 ± 21.6 tDM ha−1, and the aerial net primary productivity ranges between 25.9 and 136.4 tDM ha−1 yr−1. Papyrus vegetation can be harvested by hand and stacked on the rhizome mat for partial air‐drying, and it has been demonstrated that an annual harvesting regime has no negative impacts on long‐term productivity. The use of papyrus as a biofuel for cooking and heating depends on converting it to a suitably combustible form, such as compressed or carbonized briquettes with a calorific value approximately one‐third less than wood charcoal. While papyrus has significant potential as a biofuel, we argue that an integrated management and decision‐making framework for the sustainable utilization of papyrus wetlands is required, in which all ecosystem services including the provision of biomass energy need to be assessed. Sustainability of papyrus wetlands requires management which combines the strength of traditional communal governance and modern legislation to promote its utilization. In this way, local communities can benefit from the inherent advantages of tropical wetlands as very productive ecosystems.

Impact of papyrus wetland encroachment on spatial and temporal variabilities of stream flow and sediment export from wet tropical catchments

During the past decades, land use change in the Lake Victoria basin has significantly increased the sediment fluxes to the lake. These sediments as well as their associated nutrients and pollutants affect the food and water security of millions of people in one of Africa's most densely populated regions. Adequate catchment management strategies, based on a thorough understanding of the factors controlling runoff and sediment discharge are therefore crucial. Nonetheless, studies on the magnitude and dynamics of runoff and sediment discharge are very scarce for the Lake Victoria basin and the African Rift region.We therefore conducted runoff discharge and sediment export measurements in the Upper Rwizi, a catchment in Southwest Uganda, which is representative for the Lake Victoria basin. Land use in this catchment is characterized by grazing area on the high plateaus, banana cropping on the slopes and Cyperus papyrus L. wetlands in the valley bottoms. Due to an increasing population pressure, these papyrus wetlands are currently encroached and transformed into pasture and cropland. Seven subcatchments (358km2–2120km2), with different degrees of wetland encroachment, were monitored during the hydrological year June 2009–May 2010.Our results indicate that, due to their strong buffering capacity, papyrus wetlands have a first-order control on runoff and sediment discharge. Subcatchments with intact wetlands have a slower rainfall–runoff response, smaller peak runoff discharges, lower rainfall–runoff ratios and significantly smaller suspended sediment concentrations. This is also reflected in the measured annual area-specific suspended sediment yields (SYs): subcatchments with encroached papyrus swamps have SY values that are about three times larger compared to catchments with intact papyrus vegetation (respectively 106–137tonkm−2y−1 versus 34–37tonkm−2y−1). We therefore argue that protecting and (where possible) rehabilitating these papyrus wetlands should be a corner stone of catchment management strategies in the Lake Victoria basin.

Reviewing the carbon cycle dynamics and carbon sequestration potential of Cyperus papyrus L. wetlands in tropical Africa

Tropical papyrus wetlands have the ability to assimilate and sequester significant amounts of carbon. However, the spatial extent, productivity and carbon sink strength associated with papyrus wetlands remains poorly characterised. The objective of this study was to collate information from peer-reviewed publications and relevant government and NGO reports to better understand carbon dynamics within papyrus dominated wetlands, and to assess the processes that regulate the magnitude of the carbon sink. Papyrus wetlands were shown to exhibit high rates of photosynthetic carbon dioxide (CO2) assimilation of up to 40 μmol CO2 m−2 s−1 where the incident photosynthetic photon flux density was ≥1,000 μmol m−2 s−1, high rates of net primary production ranging between 14 and 52 g DM m−2 d−1 and represent a significant carbon sink where up to 88 t C ha−1 is stored in the aboveground and belowground components of the papyrus vegetation. Under flooded conditions significant detrital and peat deposits accumulate in excess of 1 m in depth, representing an additional carbon store in the order of 640 t C ha−1. This study also highlighted the lack of empirical data on emissions of other radiatively important trace gases such as methane and nitrous oxide and also the vulnerability of these carbon sinks to both future changes in climate, in particular periods of hydrological drawdown, and anthropogenic land use change where the papyrus vegetation is removed in favour of subsistence agricultural cropping systems.

Discriminating the papyrus vegetation (Cyperus papyrus L.) and its co-existent species using random forest and hyperspectral data resampled to HYMAP

Techniques for discriminating swamp wetland species are critical for the rapid assessment and proactive management of wetlands. In this study, we tested whether the random forest (RF) algorithm could discriminate between papyrus swamp and its co-existent species (Phragmites australis, Echinochloa pyramidalis and Thelypteris interrupta) using in situ canopy reflectance spectra. Canopy spectral measurements were taken from the species using analytical spectral devices but later resampled to Hyperspectral Mapper (HYMAP) resolution. The RF algorithm and a simple forward variable selection (FVS) technique were used to identify key wavelengths for discriminating papyrus swamp and its co-existence species. The method yielded 10 wavelengths located in the visible and short-wave infrared portions of the electromagnetic spectrum with a lowest out-of-bag (OOB) estimate error rate of 9.5% and .632+ bootstrap error of 8.95%. The use of RF as a classification algorithm resulted in overall accuracy of 90.50% and a kappa value of 0.87, with individual class accuracies ranging from 93.73% to 100%. Additionally, the results from this study indicate that the RF algorithm produces better classification results than conventional classification trees (CTs) when using all HYMAP wavelengths (n = 126) and when using wavelengths selected by the FVS technique.

Assessment of nutrient retention by Natete wetland Kampala, Uganda

Natete wetland which is located in a suburb of Kampala city in Uganda is dominated by C yperus papyrus and covers an area of approximately 1 km 2. The wetland receives wastewater and runoff from Natete town which do not have a wastewater treatment facility. The main objective of this study was to assess nutrient retention of Natete wetland and specifically to: determine the wastewater flow patterns in the wetland; estimate the nutrient loads into and out of the wetland; determine the nutrient retention by soil, plants and water column in the wetland; and assess the above and belowground biomass density of the dominant vegetation. Soil, water and plant samples were taken at 50 m intervals along two transects cut through the wetland; soil and water samples were taken at 10 cm just below the surface. Physico-chemical parameters namely pH, electrical conductivity and temperature were measured in situ. Water samples were analyzed in the laboratory for ammonium-nitrogen, nitrate-nitrogen, total nitrogen, orthophosphate and total phosphorus. Electrical conductivity ranged between 113 μS/cm and 530 μS/cm and the wastewater flow was concentrated on the eastern side of the wetland. pH varied between 6 and 7, temperature ranged from 19 °C to 24 °C. NH 4-N, NO 3-N, and TN concentrations were retained by 21%, 98%, and 35% respectively. Phosphorus concentration was higher at the outlet of the wetland possibly due to release from sediments and leaching. Nutrient loads were higher at the inlet (12,614 ± 394 kgN/day and 778 ± 159 kgP/day) than the outlet (2368 ± 425 kgN/day and 216 ± 56 kgP/day) indicating retention by the wetland. Plants stored most nutrients compared to soil and water. The belowground biomass of papyrus vegetation in the wetland was higher (1288.4 ± 8.3 gDW/m 2) than the aboveground biomass (1019.7 ± 13.8 gDW/m 2). Plant uptake is one of the important routes of nutrient retention in Natete wetland. It is recommended that harvesting papyrus can be an effective way of nutrient removal especially phosphorus which is not easily lost to the atmosphere like nitrogen. Natete wetland needs to be left in its natural state for better efficiency in nutrient retention. Bio-manipulation of the wetland by spreading the wastewater as it enters the wetland could enhance the interaction between plants and wastewater and subsequent nutrient removal.

SRTM DEM levels over papyrus swamp vegetation – a correction approach

Abstract. The SRTM DEM, a digital elevation model based on the Shuttle Radar Topography Mission of February 2000 is a source of elevation data with nearly worldwide coverage. It has proven its usefulness in various regions but problems persist for densely vegetated areas where, caused by the organic matter and water content of the vegetation, the radar signal is reflected at some level between the vegetation canopy and the ground level. This level varies with different types and densities of vegetation cover and has so far not been assessed for papyrus areas. The paper describes the approach and establishment of a correction factor for a pilot area in the Sudd swamps of southern Sudan based on comparison of SRTM reference levels and ground control points collected during field surveys between 2004 and 2006. Results show a correction factor between the sensed and the real surface of 4.66 m and a average penetration depth of the radar signal into the dense papyrus vegetation of 0.34 m.

Spectral discrimination of papyrus vegetation ( Cyperus papyrus L.) in swamp wetlands using field spectrometry

Techniques for mapping and monitoring wetland species are critical for their sustainable management. Papyrus ( Cyperus papyrus L.) is one of the most important species-rich habitats that characterize the Greater St. Lucia Wetlands Park (GSWP) in South Africa. This paper investigates whether papyrus could be discriminated from its co-existing species using ASD field spectrometer data ranging from 300 nm to 2500 nm, yielding a total of 2151 bands. Canopy spectral measurements from papyrus and three other species were collected in situ in the Greater St. Lucia Wetlands Park, South Africa. A new hierarchical method based on three integrated analysis levels was proposed and implemented to spectrally discriminate papyrus from other species as well as to reduce and subsequently select optimal bands for the potential discrimination of papyrus. In the first level of the analysis using ANOVA, we found that there were statistically significant differences in spectral reflectance between papyrus and other species on 412 wavelengths located in different portions of the electromagnetic spectrum. Using the selected 412 bands, we further investigated the use of classification and regression trees (CART) in the second level of analysis to identify the most sensitive bands for spectral discrimination. This analysis yielded eight bands which are considered to be practical for upscaling to airborne or space borne sensors for mapping papyrus vegetation. The final sensitivity analysis level involved the application of Jeffries-Matusita (JM) distance to assess the relative importance of the selected eight bands in discriminating papyrus from other species. The results indicate that the best discrimination of papyrus from its co-existing species is possible with six bands located in the red-edge and near-infrared regions of the electromagnetic spectrum. Overall, the study concluded that spectral reflectance of papyrus and its co-existing species is statistically different, a promising result for the use of airborne and satellite sensors for mapping papyrus. The three-step hierarchical approach employed in this study could systematically reduce the dimensionality of bands to manageable levels, a move towards operational implementation with band specific sensors.

Nutrient status and retention in pristine and disturbed wetlands in Uganda: management implications

Wetlands in Uganda experience different forms of human pressure ranging from drainage for agriculture and industrial development to over harvesting of wetland products. In order to develop sustainable management tools for wetland ecosystems in Uganda and the Lake Victoria Region, water quality analyses were carried out in a rural undisturbed (pristine) wetland (Nabugabo wetland in Masaka) and two urban wetlands that are experiencing human and urban development pressure (the Nakivubo wetland in Kampala and Kirinya wetland in Jinja). The former wetland forms the main inflow into Lake Nabugabo while the other two border the northern shore of Lake Victoria, Uganda. Nabugabo wetland buffers Lake Nabugabo against surface runoff from the catchment, while Nakivubo and Kirinya wetlands provides a water treatment function for wastewater from Kampala City and Jinja town respectively, in addition to buffering Lake Victoria against surface runoff. Water quality was assessed in all the wetland sites, and in addition nutrient content and storage was investigated in the main plant species (papyrus, Phragmites, Miscanthidium and cocoyam) in Nakivubo and Kirinya wetlands. A pilot experiment was also carried out to assess the wastewater treatment potential of both the papyrus vegetation and an important agricultural crop Colocasia esculenta (cocoyam). Low electrical conductivity, ammonium–nitrogen and ortho-phosphate concentrations were recorded at the inflow into Nabugabo wetland (41.5 μS/cm; 0.91 mg/l and 0.42 mg/l respectively) compared to the Nakivubo and Kirinya wetlands (335 μS/cm; 31.68 mg/l and 2.83 mg/l and 502 μS/cm; 10 mg/l and 1.87 mg/l respectively). The papyrus vegetation had higher biomass in Nakivubo and Kirinya wetlands (6.7 kg DW m−2; 7.2 kg DW m−2 respectively), followed by Phragmites (6.5, 6.7), cocoyams (6.4, 6.6) and Miscanthidium (4.0, 4.2). The papyrus vegetation also exhibited a higher wastewater treatment potential than the agricultural crop (cocoyam) during the pilot experiment (maximum removal degree of ammonium–nitrogen being 95% and 67% for papyrus and yams). It was concluded that urbanisation pressure reduces natural wetland functioning either through the discharge of wastewater effluent or the degradation of natural wetland vegetation. It is recommended that wetland vegetation be restored to enhance wetland ecosystem functioning and for wetlands that are not yet under agricultural pressure, efforts should be made to halt any future encroachment.

Carbon and water cycles in tropical papyrus wetlands

Highly productive papyrus (Cyperus papyrus L.) wetlands dominate many permanently flooded areas of tropical East Africa; however, the cycling of carbon and water within these ecosystems is poorly understood. The objective of this study was to utilise Eddy Covariance (EC) techniques to measure the fluxes of carbon dioxide and water vapour between papyrus vegetation and the atmosphere in a wetland located near Jinja, Uganda on the Northern shore of Lake Victoria. Peak, midday rates of photosynthetic CO2 net assimilation were approximately 40 μmol CO2 m−2 s−1, while night time losses through respiration ranged between 10 and 20 μmol CO2 m−2 s−1. Numerical integration of the flux data suggests that papyrus wetlands have the potential to sequester approximately 0.48 kg C m−2 y−1. The average daily water vapour flux from the papyrus vegetation through canopy evapotranspiration was approximately 4.75 kg H2O m−2 d−1, which is approximately 25% higher than water loss through evaporation from open water.

Comparative assessment of the value of papyrus and cocoyams for the restoration of the Nakivubo wetland in Kampala, Uganda

Nakivubo wetland, located on the northern shores of Lake Victoria, separates the city of Kampala from the Inner Murchison Bay of Lake Victoria (the sole raw water supply for Kampala). It provides tertiary treatment for the secondary effluent from the Bugolobi sewage treatment works, and heavily polluted wastewater (run-off, domestic and industrial effluents) from the Nakivubo channel. However, more than half of the wetland has been drained for agriculture and the natural papyrus vegetation ( Cyperus papyrus) has been progressively replaced by cocoyams ( Colocasia esculenta). In order to provide information that could be used in the restoration of Nakivubo wetland, a pilot study was carried out to assess the ecological characteristics (nutrient retention and growth characteristics) of the two plants. The plants were grown in wastewater effluent from the Bugolobi sewage treatment works, in experimental buckets under floating and rooted conditions. The wastewater was replaced every seven days. Papyrus plants were more efficient at removing NH 4-N while growing floating in wastewater or rooted in gravel (maximum values being 89.4% and 79%, respectively) than were cocoyams (67.7% and 68.3%) or the controls without plants (11% and 9%, respectively). The removal of orthophosphate by papyrus was also greater under the two growing conditions (values being 80% and 73%) than by cocoyams (66% and 63%) or the controls (11% and 14%). Biomass densities of papyrus were also higher (16.9 kg Dw/m 2 for the floating plants and 18.7 kg Dw/m 2 for the rooted ones) than of yams (5.9 kg DW/m 2 and 6.8 kg DW/m 2, respectively). It was also observed that the rhizomes of yams did not develop well under the floating conditions and were often rotten. It is concluded that, since papyrus has better wastewater treatment efficiency and superior growth characteristics, it should be encouraged to grow again in the wetland. It was also noted that if encroachment of the wetland by agricultural activities is halted, papyrus would eventually out-compete the yams. Keeping Nakivubo wetland inundated would offer papyrus a competitive advantage, since yams grow poorly when floating in water.

The effect of wastewater discharge on biomass production and nutrient content of Cyperus papyrus and Miscanthidium violaceum in the Nakivubo wetland, Kampala, Uganda

The nutrient content of representative plant parts and biomass production in the Nakivubo wetland, correlation of these with the wastewater flow patterns and determination of nutrient uptake, storage and biomass production of Cyperus papyrus (papyrus) and Miscanthidium violaceum was studied. On average papyrus vegetation under the influence of wastewater had higher nutrient content in the above ground biomass (1.6% N and 0.23% P on dry weight basis) than those not affected (0.98% N and 0.18% P). The biomass varied between 3,529-5,844 g/m2 and 883-1,156 g/m2 in the two respective sites. The juvenile plants of papyrus and Miscanthidium had higher concentrations of P and N in their organs compared to the mature ones. Considering the nutrients stored by the dominant vegetation and the current flow patterns of wastewater in the Nakivubo wetland, harvesting of the above ground biomass once a year, would remove 7.7% of the N input and 15.8% of the P input of the annual total load entering the wetland. However, if the wetland is bio-manipulated and the wastewater flow distributed over the whole wetland, up to 70% nitrogen and 76% phosphorus would be removed by harvesting above ground papyrus biomass.

The response of Cyperus papyrus (L.) and Miscanthidium violaceum (K. Schum.) Robyns to eutrophication in natural wetlands of Lake Victoria, Uganda

Interrelationships between nutrient concentrations and aerial biomass, root numbers, length and rhizomes size in Cyperus papyrus (L.) (papyrus) and Miscanthidium violaceum (K. Schum.) Robyns (synonymous to Miscanthus violaceus (K. Schum) Pilg.) were established in five different wetlands around the northern shores of Lake Victoria in Uganda. The two macrophytes were also grown experimentally under controlled nutrient conditions. There were no significant differences between the rhizome sizes of Miscanthidium in the different wetlands, but those of papyrus varied significantly. Papyrus showed no significant differences in root lengths and numbers under different nutrient conditions in the different wetlands studied. Miscanthidium on the other hand tended to have more and shorter roots in nutrient-rich wetlands as opposed to fewer and longer roots under low nutrient concentrations. Below-ground biomass values for floating papyrus swamps had an average of 1296g dry wt m−2 and rooted papyrus swamps, 776g dry wt m−2. The aerial biomass of papyrus showed a positive response to higher nutrient conditions. In wetlands receiving domestic wastewater, values ranged from 3973–6255g dry wt m−2: in wetlands without wastewater, the aerial biomass values were lower (1983–2862g dry wt m−2). Miscanthidium did not show any clear response to nutrients, having a more or less uniform aerial biomass of 2065 ± 98g dry wt m−2. Results from growth experiments showed that above- and below-ground biomass values were higher for papyrus than Miscanthidium. Whilst papyrus gave a clear positive growth response to increased nutrient conditions, Miscanthidium did not. It was concluded that papyrus vegetation had a better potential for the treatment of nutrientenriched water than Miscanthidium.