Quadrat Research Articles

Assessment of WorldView-2 images for aboveground seagrass carbon stock mapping in patchy and continuous seagrass meadows

ABSTRACT Spatially explicit information on aboveground seagrass carbon stock (AGCseagrass) is required to understand the role of seagrass as a nature-based solution to mitigating and adapting to climate change. Remote sensing provides the most effective and efficient means to map AGCseagrass. This research aimed to assess the accuracy of multispectral images to map AGC in seagrass meadows with different characteristics. Kemujan Island in Indonesia was selected to represent patchy beds with relatively low seagrass percent cover and low water clarity, whereas Labuan Bajo of Indonesia served an example of continuous beds with a relatively high percent cover and water clarity. WorldView-2 is a high-spatial-resolution multispectral image with six visible bands, by which water can be penetrated. Several image processing techniques, including sunglint and water column correction, principal component analysis, and co-occurrence texture analysis, were applied to the atmospherically corrected WorldView-2 images. These datasets were used as inputs in the AGC empirical model using seven regression algorithms, namely, single-band linear regression, band-ratio linear regression, stepwise regression, random forest regression, support vector regression, extreme gradient boosting, and multivariate adaptive regression spline. Seagrass field data collected using photo quadrat technique were used to train the regression model and assess the accuracy of the resulting AGCseagrass maps. The results indicated that WorldView-2 can be used to map AGC in different seagrass meadows with a consistent accuracy. The most accurate AGCseagrass map for Kemujan Island had a root mean square error (RMSE) of 4.11 g C m−2 for the aboveground stock in the range of 0–28.70 g C m−2, and for Labuan Bajo, the RMSE of the map was 9.73 g C m−2, with aboveground stock range of 0.31–64.38 g C m−2. Model cross-validation revealed that the mapping model can be site-specific or robust depending on the characteristics of the field-derived AGCseagrass data used to train the regression algorithm. For example, the model developed for Labuan Bajo seagrasses, which had a higher AGC variance, can be successfully applied to Kemujan Island with its lower AGC variance, but not vice versa. This finding is a key factor in the future development of a robust AGCseagrass mapping model that is applicable to various seagrass meadows as a stepping stone to accelerating the filling of gaps in the global seagrass dataset.

Coral reef benthic composition and its influence on reef fish communities in Buton Islands

Benthic communities in coral reef ecosystems are very dynamic and influenced by environmental conditions and human factors. Unfortunately, changes in benthic communities can impact reef fish communities which are essential to support fishery industries. This study investigates the change and relationships between coral reef benthic and fish communities in Buton Islands from 2016 to 2018. The methods used were underwater photo quadrat to estimate percent covers of benthic communities and belt transect to observe the reef fish communities. The result shows that, based on an ordination analysis, the majority of reefs within the years were characterized by Dead Coral with Algae (DCA) and hard coral (HC), indicating that the reef conditions, in general, remained stable during the period. In this case, DCA covers were 42.13 ± 3.66% (SE) in 2016, 42.97 ± 2.21% (SE) in 2017, and 28.46 ± 4.27% (SE) in 2018, whereas, percent covers of hard corals were 28.83 ± 3.92% (SE), 30.16 ± 3.49% (SE) and 35.76 ± 4.41% (SE) for 2016, 2017, and 2018 respectively Although not significantly changing, this stable condition was correlated significantly with overall fish diversity. Furthermore, corallivore species richness and diversity were subject to change when the benthic gradients changed. Although not all fish functional groups were affected (probably due to low percent covers of algae, sponges, soft corals, and others), the change in benthic communities requires more attention, especially when the reefs shift to non-reef building corals-dominated reefs. Continuous monitoring and local communities’ participation need to be improved to maintain the current reef condition and provide better insight regarding coastal ecosystem management.

Switching between standard coral reef benthic monitoring protocols is complicated: proof of concept.

Monitoring the state of coral reefs is necessary to identify drivers of change and assess effectiveness of management actions. There are several widely-used survey methods, each of which is likely to exhibit different biases that should be quantified if the purpose is to combine datasets obtained via different survey methods. The latter is a particularly important consideration when switching methodologies in long-term monitoring programs and is highly relevant to the Caribbean today. This is because of the continuing need for regionally comparable coral reef monitoring datasets and the fact that the Global Coral Reef Monitoring Network (GCRMN)-Caribbean node is now recommending a photoquadrat (PQ) method over the chain intercept transect method widely adopted by the members of the first truly regional monitoring network, Caribbean Coastal Marine Productivity Program (CARICOMP), in the early-1990s. Barbados, a member of the CARICOMP network, has been using a variation of the chain intercept method in its long-term coral reef monitoring program for more than two decades. Now a member of GCRMN-Caribbean, Barbados is considering switching to the PQ method in conformity with other regional members. Since we expect differences between methods, this study seeks to quantify the nature of those differences to inform Barbados and others considering switching methods. In 2017, both methods were concurrently implemented at 21 permanent monitoring plots across three major reef types in Barbados. Differences in % cover estimates for the six major benthic components, that is, hard corals, sponges, gorgonians, macroalgae, turf algae and crustose coralline algae, were examined within and among reef types. Overall, we found a complex pattern of differences between methods that depended on the benthic component, its relative abundance, and the reef type. We conclude that most benthic components would require a different conversion procedure depending on the reef type, and we provide an example of these procedures for Barbados. The factors that likely contribute to the complex pattern of between-method differences are discussed. Overall, our findings highlight that switching methods will be complicated, but not impossible. Finally, our study fills an important gap by underscoring a promising analytical framework to guide the comparison of ecological survey methods on coral reefs.

Weed flora survey in field crops of Northwestern Ethiopia

A survey was conducted in different field crops of six districts (Chilga, Gondarzuria, Metema, Takussa, Dabat and Dembia) in Northwestern Ethiopia within 2016 and 2017 cropping seasons. The objective of the study was to identify the most important weed species and to determine their frequency, density and uniformity at different altitudes. A quantitative and qualitative method was employed for the enumeration and identification of weed species. Quadrats were laid along transects and individual weed species in each quadrat was identified and counted. Frequency, uniformity, similarity index and relative abundance were used to determine the weed community structure. A total of 76 weed species belonging to 65 genera within 27 families were identified across different field crops. The most dominant families, based on the family dominance index (FDI), were Asteraceae, Poaceae, and Fabaceae with 78.97, 63.76, and 20.72 FDI, respectively. The most frequent, abundant and dominant weed species were Digitaria abyssinica (Hochst. Ex A. Rich), Cyperus rotundus L. and Cynodon dactylon L. The average values for frequency and dominance of weed species in arable fields ranged between 49.34 to 59.87% and 3 to 3.69%, respectively. Results obtained from this study would be useful in creating a weed management programme and making inform decision on choice of herbicides and directing research toward new or improved weed control measures. Key words: Altitude, density, district, dominance, family, frequency, species.

Community assessment techniques and the implications for rarefaction and extrapolation with Hill numbers.

Diversity estimates play a key role in ecological assessments. Species richness and abundance are commonly used to generate complex diversity indices that are dependent on the quality of these estimates. As such, there is a long‐standing interest in the development of monitoring techniques, their ability to adequately assess species diversity, and the implications for generated indices. To determine the ability of substratum community assessment methods to capture species diversity, we evaluated four methods: photo quadrat, point intercept, random subsampling, and full quadrat assessments. Species density, abundance, richness, Shannon diversity, and Simpson diversity were then calculated for each method. We then conducted a method validation at a subset of locations to serve as an indication for how well each method captured the totality of the diversity present. Density, richness, Shannon diversity, and Simpson diversity estimates varied between methods, despite assessments occurring at the same locations, with photo quadrats detecting the lowest estimates and full quadrat assessments the highest. Abundance estimates were consistent among methods. Sample‐based rarefaction and extrapolation curves indicated that differences between Hill numbers (richness, Shannon diversity, and Simpson diversity) were significant in the majority of cases, and coverage‐based rarefaction and extrapolation curves confirmed that these dissimilarities were due to differences between the methods, not the sample completeness. Method validation highlighted the inability of the tested methods to capture the totality of the diversity present, while further supporting the notion of extrapolating abundances. Our results highlight the need for consistency across research methods, the advantages of utilizing multiple diversity indices, and potential concerns and considerations when comparing data from multiple sources.

Comparison ofT-Square, Point Centered Quarter, andN-Tree Sampling Methods inPittosporum undulatumInvaded Woodlands

Tree density is an important parameter affecting ecosystems functions and management decisions, while tree distribution patterns affect sampling design.Pittosporum undulatumstands in the Azores are being targeted with a biomass valorization program, for which efficient tree density estimators are required. We comparedT-Square sampling, Point Centered Quarter Method (PCQM), andN-tree sampling with benchmark quadrat (QD) sampling in six 900 m2plots established atP. undulatumstands in São Miguel Island. A total of 15 estimators were tested using a data resampling approach. The estimated density range (344–5056 trees/ha) was found to agree with previous studies using PCQM only. Although with a tendency to underestimate tree density (in comparison with QD), overall,T-Square sampling appeared to be the most accurate and precise method, followed by PCQM. Tree distribution pattern was found to be slightly aggregated in 4 of the 6 stands. Considering (1) the low level of bias and high precision, (2) the consistency among three estimators, (3) the possibility of use with aggregated patterns, and (4) the possibility of obtaining a larger number of independent tree parameter estimates, we recommend the use ofT-Square sampling inP. undulatumstands within the framework of a biomass valorization program.

Variations in Forest Carbon Stocks Along Environmental Gradients in Egdu Forest of Oromia Region, Ethiopia: Implications for Sustainable Forest Management

Forests play a significant role in climate change mitigation by sequestering and storing more carbon from the atmosphere than any other terrestrial ecosystem. Although a number of studies have been done on carbon stock estimations, the influence of environmental factors on forest carbon stocks has not been properly addressed. This study was conducted to estimate the carbon stock and its variation along the altitudinal gradients in Egdu dry afromontane forest found in Oromia Regional State of Ethiopia. The carbon stock in the different carbon pools and analysis of the influence of the environmental variables were studied by collecting data in sixty-nine quadrat plots of 10 x 20 m distributed along transect lines. To estimate carbon in above and below ground biomass; each tree in the study site having diameter at breast height (DBH) of ≥ 5 cm were measured for DBH and height. Above ground biomass was estimated by using allometric model while below ground biomass was determined based on the ratio of below ground biomass to above ground biomass factors. The mean total carbon stock density of Egdu Forest was found to be 614.72 ± 35.79 t ha-1 (ranging from 182.6 to1416 t ha-1), of which 45.24% of carbon was contained in the above ground biomass, 9.05% in below ground biomass, 0.56% in litter carbon and 45.15% was stored in soil organic carbon (0-30 cm depth). The carbon stocks in above ground biomass, below ground biomass, litter biomass and soil organic carbon exhibited distinct patterns along environmental gradients (slope gradient and slope aspect). The analysis of carbon stock variation of different carbon pools on eight different aspects of the forest area showed a significant variation with exception of soil organic carbon stock. The amount of carbon stock in above and below ground biomass, soil organic carbon and the total carbon stock was higher on the northern aspect as compared to other aspects. On the other hand, the carbon density of the forest carbon pool components showed a negative correlation with slope gradient; with increasing % slope, the above and below ground carbon, soil organic carbon and the total carbon stock decreased. This study concluded that the carbon stock value of Egdu Forest is large, and the carbon storage in different carbon pools of the forest area varies with slope aspect and slope aspect.

HUBUNGAN FAKTOR PERILAKU DENGAN KEJADIAN HEPATITIS A DI KECAMATAN DEPOK KABUPATEN SLEMAN

Dinas Kesehatan Kabupaten Sleman melaporkan terjadi peningkatan jumlah kasus hepatitis A di Kabupaten Sleman dan sebagian besar adalah mahasiswa. Tujuannya untuk mengetahui faktor perilaku berisiko dengan kejadian hepatitis A di Sleman. Penelitian observasional dengan rancangan kasus kontrol. Teknik pengambilan sampel adalah consecutive sampling (non probability sampling). Uji statistik yang digunakan adalah chi square (x2) dan regresi logistik. Jumlah responden adalah 280 orang (140 kasus dan 140 kontrol). Riwayat kontak dengan penderita hepatitis A (OR=3,42 95%CI=1,97-5,95; p=0,00), tidak mencuci tangan dengan sabun (OR=2,19; 95%CI=1,32-3,65; p=0,00), tidak mencuci alat makan dengan sabun (OR=2,88; 95%CI=1,03-9,25; p=0,02), sering mengonsumsi sayur/makanan mentah (tidak dimasak)(OR=3,8295%CI=1,94-7,81p=0,00), tukar menukar alat makan (OR=2,0995%CI=1,26-3,48; p=0,00), sering makan di warung yang hanya mencuci dengan satu ember (OR=2,22; 95%CI=1,22-4,09; p=0,00), dan tidak memperhatikan kebersihan warung (OR=3,74; 95%CI= 2,19-6,41; p=0,00) mempunyai hubungan yang signifikan dengan hepatitis A. Hasil analisis multivariat menunjukkan riwayat kontak dengan penderita hepatitis A (OR=3,17; 95%CI=1,82-5,52; p=0,00; z=4,09), sering mengonsumsi sayur/makanan mentah (tidak dimasak) (OR=3,43; 95%CI=1,73-6,81; p=0,00; z=3,52) dan tidak memperhatikan kebersihan warung (OR=3,28;95%CI=1,92-5,60; p=0,00; z=4,35). Perilaku sehat dan tidak hygienis adalah faktor risiko hepatitis A di Sleman.

Primary Mangrove Forest Structure and Biodiversity

An understanding of the mangrove forest structure is ecologically important, this information useful for the management and sustainable conservation. Aim of this study is to analyze the structure and biodiversity of natural mangrove communities in Sungai Sembilang and Sungai Bungin, Sembilang National Park (SNP). The survey was conducted in September- October 2013. The data was collected by using quadrat of line transect method. The results of the study have a highest density structure in location I was Nypa fruticans Sungai Sembilang and Sungai Bungin which was located on the third location of the same species on the tree level . Seedling density of Rhizophora mucronata highest in Sungai Sembilang at location III and Rhizophora apiculata Sungai Bungin at location I , and seedling of Bruguiera gymnorrhiza in location III Sungai Sembilang and Rhizophora apiculata in Sungai Bungin at location III . The composition of mangrove forests on both the location of the observation that 12 species of mangrove found. Similarity Index of the mangrove vegetation in Sungai Sembilang and Sungai Bungin on trees level, saplings and seedlings respectively 14.2%; 9.3%; and 12.5%.

Benthic and fish population monitoring associated with a marine protected area in the nearshore waters of Grenada, Eastern Caribbean

<span>Un estudio sobre poblaciones bentónicas y de peces fue realizado en cinco localidades en la zona costera en el suroeste de Grenada entre 2008 y 2010. Dos sitios se ubicaron en una Área Marina Portegida (AMP) recientemente creada. Para determinar la cobertura se utilizaron foto-cuadrantes (FQ) y transectos de intersección de puntos (TIP). Las algas fueron el principal componente del bentos, aumentando significativamente de 45,9% en 2008 a 52,7% en 2010 (TIP). Las algas también fueron predominantes (61,9%-59,3) en los FQ, aunque las diferencias anuales no fueron significativas. La cobertura de corales pétreos tenía un ámbito de 16,5% a 15,4% (TIP) y de 11,4% a 12,0% (FQ), sin diferencias significativas entre años. Los corales ramificados e incrustantes fueron más frecuentes que los corales masivos. En los tres años no hubo diferencias significativas entre las AMPs y las áreas no protegidas. La abundancia relativa de peces a lo largo de un transecto de 30x2m no varió significativamente entre los años, sin embargo, la densidad de peces decreció significativamente a través de los años, para los grupos principales.<em> Chromis</em> spp. predominó con 65,2% en 2008 y 49,8% en 2012, seguido por damiselas territoriales, 11,1% y 15,5%, y los lábridos aumentaron de 7,3% a 15,5%. Tanto la coberura del sustrato como los datos de peces indican una comunidad estable pero degradada. Sondeos anuales están planeados para el futuro. Los datos existentes y futuros de este proyecto serán muy útiles para determinar la eficacia de la gestión de las AMPs y el estado de salud de los sistemas arrecifales de Grenada.</span>

Monitoreo en aguas cercanas al área marina protegida en la costa de Granada, Caribe Oriental: cobertura bentónica y poblaciones de peces

Grenada is highly dependent on coral reefs as a source of food and to support tourism. Local and global environmental stressors threaten these reefs. Legislation was created for this MPA in 2001, permanent mooring buoys were deployed in 2009 and enforcement of fishing restrictions began in 2010. Initiatives to address point and nonpoint source pollution from the land have recently begun, aimed at reducing stress on reef area. This study documents benthic cover and fish populations associated with reefs in a Marine Protected Area (MPA) along Grenada’s southwest coast from 2008 through 2012. Both Point Line Intercept and Photo Quadrat methods were used to assess benthic cover along permanent 30m transects (8 in and 12 outside the area) annually. Fish and Diadema antillarum urchin relative abundance were determined based on 2m wide belt surveys along the same transects. The predominant substrate cover was algae, ranging from 41% in 2009 to 74.2% in 2011. A general trend of increasing algal cover was noted. Combined annual survey results prior (2008-2010) and after controls were implemented (2011-2012) showed a significant increase in algal cover. The predominant algal form was macroalgae comprising 65.4% - 90.8% of total algae. Live hard coral percent cover ranged from 8.7% to 21.1%. Little annual variation was observed in percent live coral cover. Branching corals (34.1% - 52.3% of total living hard coral) were the most common. Of the 19 living hard coral species identified, Porites porites (21%-23%) and Porites astreoides (20%) dominated percentage composition. Madracis mirabilis contributed 21% of total live hard coral outside the MPA but only 8.7% in the MPA. Of the 63 species of fish identified in the study areas Chromis spp. (71.5% - 46%) was the dominant group. Wrasse had a significant increase from 6.9% in 2008 to 21.5% in 2010 inside the MPA with a similar increase peaking in 2011 outside the MPA. There was a noticeable (though not statistically significant) increase in piscivorous fishes in the MPA in 2012. This is a promising indication that fishing restrictions in the MPA may be having an effect. Diadema antillarum density was low, ranging from 4.58 to 0.21 urchins/100m2 outside and 0.28 to 0.10 urchins/100m2 inside despite a stocking attempt in the area in 2011. Rev. Biol. Trop. 62 (Suppl. 3): 273-286. Epub 2014 September 01.

Patrones de asociación entre la cobertura vegetal y la calidad del suelo en el matorral costero de la reserva Ría Lagartos, Yucatán

La restauración ecológica de la Reserva Ría Lagartos incluye la plantación de especies nativas; sin embargo, no se ha documentado con qué propiedades del ecosistema se relacionan estas especies en sus hábitats naturales. En este trabajo se describe la relación entre la cobertura vegetal y algunas propiedades del suelo del matorral de duna costera. Se muestrearon 30 cuadrantes de 4 m2 cada uno; en cada cuadrante se estimó el porcentaje de cobertura por especie y porcentaje de cobertura del mantillo en el suelo (MAN), así mismo se tomó una muestra de suelo de cada uno, y se les midió: pH, conductividad eléctrica (CE), densidad aparente (DA), contenido de nitrógeno total (NT), porcentaje de materia orgánica (MO) y tono de gris (TG). Se realizaron análisis de correlación entre estas variables y la cobertura de las tres especies dominantes de arbustos: Pithecellobium keyense, Bumelia retusa y Enriquebeltrania crenatifolia. P. keyense y B. retusa correlacionaron con MAN; P. keyense además correlacionó con MO, y tuvo una tendencia a aumentar con NT; E. crenatifolia correlacionó con CE. Además, se observó que TG se correlacionó con casi todas las variables, excepto pH y MAN, y que NT y DA se correlacionaron con casi todas las variables edáficas, excepto pH y CE. Los resultados obtenidos sugieren que P. keyense podría ser una especie mejoradora del suelo y que DA y TG son proxys fáciles y económicos de medir para evaluar la calidad del suelo en este sitio.

Analysis of predictive factors affecting sentinel lymph node status in early breast cancer patients

To investigate the predictive factors affecting sentinel lymph node status in early breast cancer patients. Clinicopathological data of 1 038 patients with early breast cancer, who underwent sentinel lymph node biopsy in Henan Tumor Hospital between July 2010 and August 2013, were reviewed. Logistic regression analysis was performed to identify the relevance of clinicopathological features with sentinel lymph node metastases. This group was consisted of 1 038 female patients with an average of 48.6 years. Positive sentinel lymph nodes were found in 22.9% (238/1 038) of the patients. The average number of sentinel lymph nodes removed by surgery was 3.8. Tumor size, tumor location, histopathology, ER/PR status and Ki-67 level were significantly correlated with SLN metastasis(P < 0.05 for all). All the above factors but Ki-67 level were significant independent predictors for SLN metastasis(P < 0.01 for all). Negative hormone receptor status, invasive cancer of non-specific histopathological type, tumor size >2 cm, and tumor location in the outer upper quadrat are independent predictive factors of sentinel lymph node metastasis in patients with early breast cancer.

Plant Species Diversity in Unmanaged Moist Deciduous Forest of Northern India

The present study examines species recovery and change in community composition four decades after the management plan completely constrained all silvi-cultural activities in Doon Valley (India) moist deciduous sal forests ( Shorea robusta ). These forests experienced intensive commercial logging for an extended period (> 100 years). To discontinue disinte-gration and improve the diversity and regeneration, these were declared protective and consequently all silvicultural activities were abandoned. For this, spe-cies richness and regeneration were studied in the con-text of overstorey structure, employing nested quadrat method. Out of 130 species reported in the earliest-most study from these forests, only 68 species were recorded here. Change in community composition has taken place with Mallotus philippensis becoming do-minant in one community; this association is new for these forests. Effect of overstorey structure was noti-ceable, highest species richness and diversity were in-creasing with a decrease in tree density and basal area. These forests showed impaired regeneration progression; for all the groups there was a wide gap between the seedlings and saplings conversion to ad-vance stages. Prospects of recovery are fair as several tree species were reported in juvenile stages with ade-quate density. Results demonstrated that conversion of forests having a long history of exploitation to pro-tected forest is initially good, but for successful recov-ery, after a restitution time, it is desirable to emulate intermediate disturbance by selective harvesting of old and malformed trees. This will initiate gap-phase regeneration and channelize resources to lower dia-meter class trees to develop.

Effect of quadrat shapes on measurement of tree density and basal area: a case study on Scots Pine ( Pinus silvestris L.)

While quadrat shape of 10 x 10m has been commonly used in tree studies, the efficiency of this shape compared to the other shapes of size 100 m 2 has not been tested. In this study, effect of various shapes of 100 m 2 quadrat on measurement of Scots Pine ( Pinus silvestris L.) density and basal area would be assessed. The aim was to assess the effect of quadrat shapes of 10 x 10m, 5 x 20m and 2 x 50m on the estimation of density and basal area of the pine in two woodlands in Norwich and to find the most efficient shape, statistically and with respect to sampling time. The results from all quadrat shapes similarly showed that the density and basal area of the Pines between two woodlands were significantly different. In site with lower pine density, the density and basal area measurement were not affected by variety of quadrat shapes. In site where the density of the Pine was higher, however, mean density and basal area measurement using 2x50m quadrat gave higher value than of the other two shapes. In term of efficiency, all shapes were not significantly different in statistical precision and sampling time. Shape of 5x20m, however, was more preferable as it required fewer samples before the mean of density and basal area always falls inside the 95% confidence interval of whole samples mean.

수정된 사진방형구법을 이용한 조하대 해조류의 군집구조 분석

The species composition and distributions of subtidal marine algae on the east coast of Korea were studied. We examined all species found in permanent quadrats at three depths (3 m, 5 m and 10 m) at Sacheon between October 2008 and December 2009. Coverage and frequency data were collected monthly via underwater photography and analyzed using a modified photo quadrat method. Of the 82 species identified, 10 were chlorophytes, 21 were phaeophytes, 50 were rhodophytes, and one was a seagrass. The largest number of species (59) was found 10 m deep, while the fewest (39) species were present at 5 m. A total 17 species (two green, five brown, and 10 red algae) occurred at all three depths. The vertical distribution of the study site was characterized by the melobesioidean algae, Ulva pertusa, Sargassum confusum, Phyllospadix iwatensis, and Codium arabicum at 3 m deep, melobesioidean algae and U. pertusa at 5 m deep, and Corallina pilulifera, Prionitis cornea, Chondracanthus tenellus and melobesioidean algae at 10 m deep. Given that coralline algae such as melobesioidean algae and C. pilulifera play important roles in coastal ecosystems, thorough studies on the spatial and temporal variations of coralline algae and the dynamics of marine algal communities on the east coast of Korea are now required.

The influence of grass biomass production on hippopotamus population density distribution along the Luangwa River in Zambia

Hippopotamus is a selective nocturnal grazer consuming 50 kg of grass. Due to its large body size, it requires large areas of grass often exceeding 5 hectares within 2-5 km of the water body to maintain good body condition. In this study, hippo population size and density, grass biomass and grazing capacity were assessed in March 2008 along a 165 km stretch of the Luangwa River. The study area was subdivided into study blocks, A, B, C, D, E and F. Methods used were: river bank total counts, quadrat sampling and identification of all grass species, clipping of grass in a quadrat, drying of clipped grass at constant temperature of 70oC and weighing to obtain dry weight. Grazing capacity of the hippo was estimated based on grass biomass values obtained during the study. Hippo population density was then matched with grass biomass distribution along the study blocks A-H. Total primary production was 62, 800 kg with mean biomass per study block of 7, 850 kg /ha-1 (in 2008). Grazing capacity was 1 hippo/6 ha-1. Grass biomass varied significantly between river segments being higher in study blocks A, B and E and lower in study blocks C, D, F and G. Mean hippo density was 33 individuals/km stretch of the river. Hippo density was found to be above 33/km in study blocks A, B and E which had higher biomass and lower than 33/km in study blocks C, D, F and G. Hippo population density distribution was found to be influenced by grass species diversity and amount of biomass produced which also determined grazing capacity. In light of global climate change and changing rainfall patterns, more studies are required to determine the influence of rainfall on primary production and how this would affect the increase or decrease in hippo density and grazing capacity in the long-term. Key words: Hippo, density, grazing capacity, grass biomass.

Benthic Community zonation in a breakwater on the north coast of the state of Rio de Janeiro, Brazil

The present study presents the vertical zonation pattern of the intertidal benthic organisms on granitic boulders in the Farol de São Tomé beach (22º02'S, 41º03'W), Rio de Janeiro State. Four sampling profiles using 20 x 20 cm quadrats through a photo quadrat technique revealed four horizontal bands: (1) Littoral Fringe characterized by empty space and Littorina; (2) Upper eulittoral mainly occupied by Chthamalus and bare rock; (3) Lower eulittoral characterized by Chthamalus, Phragmatopoma, Ulva and Centroceras; and (4) Sublittoral Fringe characterized by Ulva, Phragmatopoma and Hypnea. The high variability in the relative abundance of the dominant species among the profiles may be attributed to the high topographic irregularity, reflecting in different wave action intensity at the same height, and consequently favoring the establishment of different species. The frequent substrate alternation from granitic rock to Phragmatopoma sandy reefs might contribute to the small-scale spatial variability. The implantation of a breakwater on an area without natural rocky shores allowed the study of intertidal benthic communty zonation, and provide a baseline for the experimental studies.

Size matters more than method: Visual quadrats vs photography in measuring human impact on Mediterranean rocky reef communities

The performances of two commonly used non-destructive sampling procedures for rocky benthic assemblages (i.e. photography and visually assessed quadrats) were compared. A damaging human activity, date mussel ( Lithophaga lithophaga) harvesting (DMH), was chosen. Directly impacted sites were compared with reference conditions (controls). Both visual quadrats and photography were equally able to detect differences between impacted situations and controls. However, visual quadrats showed high variability among replicates and estimated higher species richness for controls, while photography did so for impacts. Pooling photos in a ‘sum photo quadrat’ showed that differences between the two methods are due to sampling unit size rather than sampling procedure itself. As a small sampling unit is unavoidable with photography, visual quadrats should be preferred in investigating shallow rocky reefs for their larger size; however, longer working time underwater with quadrats does not allow for numerous replicates. Pooling many photos to reach sampling sizes comparable with those of quadrats may be a valid alternative to reconcile image resolution and areal coverage.

Comparison of physical separation and alkane concentrations to estimate the species composition of herbage samples from a pastoral environment

The botanical composition of simple herbage mixes has been successfully estimated using the alkane profiles of pasture species. In this report, the ability of the n-alkane technique to identify the component species in more complex herbage mixes from a pastoral environment was examined. Herbage samples (quadrat cuts), collected from 3 heterogeneous pastures at Condobolin, were sorted by hand to identify the botanical components and their proportional representation. Within each pasture, 19-20 individual species were identified. Groups of species were subsequently formed on the basis of a principal components analysis of their alkane profiles. The botanical composition determined by hand sorting was then compared with the estimates obtained from a least-squares optimisation of the alkane profiles, and significant differences between the techniques were found. In general, the proportions of the Medicago spp. component, and of the component including Avena spp., in the herbage mixes were underestimated.