Mean Percentage Cover Research Articles

Benthic community structure and geomorphology of uncharted nearshore reefs in Kuantan coastal waters.

The nearshore reefs play several important ecosystem functions in marine environments, especially in coastal areas. Six relatively unknown nearshore reef sites were surveyed in the southern Kuantan coastal waters using the coral video transect (CVT) technique between April 2021 and September 2022 to estimate coral reef benthic components. Data analysis on coral reef benthic components indicated that these uncharted nearshore reefs have ‘fair’ coral cover with an average percentage of 39.4 % ± 17.8 in which ST 1 recorded the highest live coral cover coverage with 68.06 %. Abiotic components (sand and rock) were the second-most abundant and the coverage of dead coral was relatively low at all stations. A total of 33 coral genera were recorded in this study in which Porites, Acropora and Montipora mean percentage cover dominated most of the reef sites. Bathymetry data indicated that some of these uncharted reefs were located on submerged shoals with a depth range between 12 – 17 meters. The variation in benthic community composition observed among reef sites highlights the importance of location-specific management and conservation strategies.

Long-Term Spatial Pattern Predictors (Historically Low Rainfall, Benthic Topography, and Hurricanes) of Seagrass Cover Change (1984 to 2021) in a Jamaican Marine Protected Area

Climate change and other anthropogenic factors have caused a significant decline in seagrass cover globally. Identifying the specific causes of this decline is paramount if they are to be addressed. Consequently, we identified the causes of long-term change in seagrass/submerged aquatic vegetation (SAV) percentage cover and extent in a marine protected area on Jamaica’s southern coast. Two random forest regression (RFr) models were built using 2013 hydroacoustic survey SAV percentage cover data (dependent variable), and auxiliary and 2013 Landsat 7 and 8 reflectance data as the predictors. These were used to generate 24 SAV percentage cover and benthic feature maps (SAV present, absent, and coral reef) for the period 1984–2021 (37 years) from Landsat satellite series reflectance data. These maps and rainfall data were used to determine if SAV extent/area (km2) and average percentage cover and annual rainfall changed significantly over time and to evaluate the influence of rainfall. Additionally, rainfall impact on the overall spatial patterns of SAV loss, gain, and percentage cover change was assessed. Finally, the most important spatial pattern predictors of SAV loss, gain, and percentage cover change during 23 successive 1-to-4-year periods were identified. Predictors included rainfall proxies (distance and direction from river mouth), benthic topography, depth, and hurricane exposure (a measure of hurricane disturbance). SAV area/extent was largely stable, with >70% mean percentage cover for multiple years. However, Hurricane Ivan (in 2004) caused a significant decline in SAV area/extent (by 1.62 km2, or 13%) during 2002–2006, and a second hurricane (Dean) in 2007 delayed recovery until 2015. Additionally, rainfall declined significantly by >1000 mm since 1901, and mean monthly rainfall positively influenced SAV percentage cover change and had a positive overall effect on the spatial pattern of SAV cover percentage change (across the entire bay) and gain (close to the mouth of a river). The most important spatial pattern predictors were the two rainfall proxies (areas closer to the river mouth were more likely to experience SAV loss and gain) and depth, with shallow areas generally having a higher probability of SAV loss and gain. Three hurricanes had significant but different impacts depending on their distance from the southern coastline. Specifically, a hurricane that made landfall in 1988 (Gilbert), resulted in higher SAV percentage cover loss in 1987–1988. Benthic locations with a northwestern/northern facing aspect (the predominant direction of Ivan’s leading edge wind bands) experienced higher SAV losses during 2002–2006. Additionally, exposure to Ivan explained percentage cover loss during 2006–2008 and average exposure to (the cumulative impact of) Ivan and Dean (both with tracks close to the southern coastline) explained SAV loss during 2013–2015. Therefore, despite historic lows in annual rainfall, overall, higher rainfall was beneficial, multiple hurricanes impacted the site, and despite two hurricanes in three years, SAV recovered within a decade. Hurricanes and a further reduction in rainfall may pose a serious threat to SAV persistence in the future.

Impact of Phytophthora dieback on a key heathland species Xanthorrhoea australis (Asphodelaceae) (austral grasstree) and floristic composition in the eastern Otways, Victoria

Context The plant pathogen Phytophthora cinnamomi causes severe declines in susceptible vegetation, including loss of plant species, vegetation structure and fauna abundance. Grasstrees (Xanthorrhoea spp.) are keystone species that provide optimal habitat for vertebrates and invertebrates and are highly susceptible to the pathogen. Although effects in the Otway Ranges have been assessed at specific sites, there is less knowledge across the landscape on the extent of loss of Xanthorrhoea australis (austral grasstree). Aims The aims were thus to assess impacts at three Heathy Woodland sites and to determine the magnitude of loss of X. australis and susceptible species losses. Methods Floristic composition, species cover or abundance, and basal area of X. australis were recorded in quadrats within treatments (uninfested, infested, post-infested vegetation). Analyses included floristics (PRIMER v7), significant effects (ANOSIM), species contribution to similarity/dissimilarity (SIMPER). Species richness and susceptible species cover were analysed using two-way crossed ANOVAs to detect the influence of site, treatment, and interactions. Key results Species composition of uninfested vegetation was significantly different to infested and post-infested vegetation, with susceptible species more abundant in uninfested areas. Post-infested vegetation had the lowest percentage cover of susceptible species. The mean percentage cover of X. australis in uninfested vegetation (43%) was 10-fold greater than in infested areas (4.3%) and extremely low in post-infested vegetation (0.9%). Conclusions Susceptible species were subject to density declines and extirpation, and the loss of X. australis resulted in major structural vegetation changes. Implications These results have severe implications for heathy woodland communities and reliant fauna. Limiting the spread of P. cinnamomi and protecting grasstrees is critical for their security.

Extensive and Continuing Loss of Seagrasses in Florida's Big Bend (USA).

Florida's Big Bend in the northeastern Gulf of Mexico contains the second-largest contiguous seagrass meadow in the continental United States, providing numerous ecosystem functions and services, including carbon cycling and storage. We present 21 years of mapping data and 13 years of annual in-water monitoring that reveal extensive declines in area, species frequency of occurrence (FO), and percent cover of seagrass. Seagrass area declined by 15% to 85,170 ha in 2022. Subregions in the southern Big Bend experienced extensive seagrass losses of 90-100%. North of the Steinhatchee River, the Northern Big Bend contained 85% of the total seagrass area and experienced losses of only 8.4%. The FO of seagrass and bare quadrats exhibited similar trends to areal coverage. The lowest FO along with complete loss of species was observed near the mouth of the Suwannee River. At a distance from the Suwannee River, FO also declined, but no species were lost. In the remainder of the Big Bend, FO remained stable except for short-term reductions in 2013-2014, which were likely related to anomalously high runoff from rainfall and tropical storm activity. Mean percent cover, however, declined throughout Big Bend, reaching minimal levels in 2014, with little to no recovery through 2019. The persistence of low percent cover may increase vulnerability of beds to continuing areal losses, but the persistence of seagrass species at a distance from the Suwannee River mouth may allow recovery if environmental conditions improve.

Physical, biological and anthropogenic drivers of spatial patterns of coral reef fish assemblages at regional and local scales

Species abundance, diversity and community assemblage structure are determined by multiple physical, habitat and management drivers that operate across multiple spatial scales. Here we used a multi-scale coral reef monitoring dataset to examine regional and local differences in the abundance, species richness and composition of fish assemblages in no-take marine reserve (NTMR) and fished zones at four island groups in the Great Barrier Reef Marine Park, Australia. We applied boosted regression trees to quantify the influence of 20 potential drivers on the coral reef fish assemblages. Reefs in two locations, Magnetic Island and the Keppel Islands, had distinctive fish assemblages and low species richness, while the Palm and Whitsunday Islands had similar species composition and higher species richness. Overall, our analyses identified several important physical (temperature, wave exposure) and biological (coral, turf, macroalgal and unconsolidated substratum cover) drivers of inshore reef fish communities, some of which are being altered by human activities. Of these, sea surface temperature (SST) was more influential at large scales, while wave exposure was important both within and between island groups. Species richness declined with increasing macroalgal cover and exposure to cyclones, and increased with SST. Species composition was most strongly influenced by mean SST and percent cover of macroalgae. There was substantial regional variation in the local drivers of spatial patterns. Although NTMR zoning influenced total fish density in some regions, it had negligible effects on fish species richness, composition and trophic structure because of the relatively small number of species targeted by the fishery. These findings show that inshore reef fishes are directly influenced by disturbances typical of the nearshore Great Barrier Reef, highlighting the need to complement global action on climate change with more targeted localised efforts to maintain or improve the condition of coral reef habitats.

The long-term effects of invasive earthworms on plant community composition and diversity in a hardwood forest in northern Minnesota.

Nonnative European earthworms are invading hardwood forests of the Chippewa National Forest, MN. While effects on plant communities at the leading edge of invasion have been studied, little is known about longer-term effects of invasive earthworms. We applied a model using historic O-horizon soil thickness and a chronosequence approach to classify 41 hardwood sites in the Chippewa National Forest as "long-term wormed" (wormed >2 decades), "short-term wormed" or "unwormed/lightly wormed." Graminoids, especially Carex pensylvanica, had the greatest mean percent cover in sites that had been wormed for over two decades. The families with the greatest negative change in mean percent cover after over two decades of earthworm invasion were Asteraceae, Violaceae, and Sapindaceae (specifically Acer species). Across all diversity metrics measured, long-term wormed sites had the lowest understory plant species diversity, short-term wormed sites had intermediate diversity, and unwormed/lightly wormed sites exhibited the highest diversity. Long-term wormed sites had the lowest mean species richness across all sample scales (1-1024 m2). The greatest within-group compositional dissimilarity occurred at sites that had been wormed for over two decades, suggesting that sites that had been wormed for over two decades have not reached a compositionally similar end-state "wormed" community type. Our study suggests that understory diversity will decrease as hardwood forest stands become wormed over time. While our results support other findings that exotic earthworm invasion is associated with lower understory plant diversity in hardwood forests, our study was the first to use space-for-time substitution to document the effects after multiple decades of earthworm invasion.

Bioaccumulation Potential of Seagrass (Halophila sp.) for Mercury in the Selected Coastal Areas in Malita, Davao Occidental

This research aims to determine the potential of seagrass Halophila sp. in absorbing mercury in the selected coastal barangays in Malita, Davao Occidental. The study employs a quantitative type of research where strategies focus on quantifying the collection and analysis of data. The study was conducted from October 2020 to December 2021 in the three selected coastal Barangays in Malita, Davao Occidental namely Brgy.Culaman, Brgy. New Argao and Brgy. Tingolo. Transect line quadrat method was used to determine the percent cover and shoot density of seagrass. Using this method, the point of seagrass occurrence up to the outer limit where seagrasses disappears was determined. There were three (3) stations and three (3) transect lines were laid for each station with an interval of 50m. Five (5) quadrats were also laid in the seagrasses along the 50 meter transect line positioned perpendicular to the shoreline. The seagrasses were collected in each quadrat and the samples were transported to Davao Analytical Laboratories, Inc. for mercury analysis. The highest mean percent cover (10.27%), shoot density (128.91 shoots/m2) and Hg accumulation (572.9ppb) was recorded in Brgy. Tingolo, Malita, Davao Occidental while the lowest result was obtained by Brgy. Culaman, Malita, Davao Occidental. Halophila sp. has the capability to accumulate mercury content and exceeds the standard level of 20 ppb. There were no significant differences in the percent cover and Hg accumulation of seagrass Halophila sp. while significant difference is observed in the shoot density. However, there is a positive relationship (.664) between the shoot density and mercury concentration of Halophila sp.

Testing restoration methods for Lake Ontario wetlands at a wetland scale

Sedges and grasses have a competitive advantage over cattails at higher elevations in Great Lakes wetlands where periodic low lake levels result in soils too dry to support cattails. Regulation of Lake Ontario water levels eliminated low lake-level years, resulting in cattail invasion. At a wetland scale at two Lake Ontario sites, we tested restoration methods by dredging channels through cattails, using spoil materials to create mounds suitable for sedge/grass growth, seeding mounds, and controlling cattails (T. × glauca) using methods adapted from experimental studies. Soil moisture and subsidence of mound soils were monitored. Vegetation was sampled pre-restoration and in shoreline sedge/grass meadow, emergent, and mound zones for two years following implementation. Although spoil mounds decreased in elevation at both sites, soil moisture increased more at the site with greater subsidence. Mean percent cover and ramet counts of cattails were reduced in sedge/grass and emergent zones at both sites. Mounds with greater soil moisture held more cattails post-construction. Across years at both sites, Carex lacustris and Calamagrostis canadensis increased in the sedge/grass meadow zone with reduction in Typha; Calamagrostis increased on the mounds. Key factors affecting results were cattail litter and, on the mounds, a second year of seeding with in situ cold, moist stratification, as well as soil moisture related to subsidence. Recommendations for future restorations include conducting more detailed soil surveys to assess potential subsidence, dredging wider and deeper channels to provide spoil for higher mounds, actively controlling invasive species, and conducting additional years of post-restoration data collection.

Seagrass in a Changing Estuary, the Indian River Lagoon, Florida, United States

Seagrass is a major structural habitat in the Indian River Lagoon. Maps documented locations and areal extents of beds periodically since the 1940s, and surveys of fixed transects yielded changes in percent cover and depths at the end of the canopy since 1994. Areal extent increased by ∼7,000 ha from 1994 to 2009, mean percent cover within beds decreased from ∼40 to 20%, and mean percent cover standardized to maximum transect length remained near 20%. Thus, conditions supported a consistent biomass because cover decreased as areal extent increased. Between 2011 and 2019, ∼19,000 ha or ∼58% of seagrasses were lost, with offshore ends of canopies moving shoreward and shallower, and standardized mean percent cover decreased to ∼4%. These changes coincided with blooms of phytoplankton, and ≤ 27% of incident subsurface irradiance at 0.9 m was stressful. Decreases in mean percent cover per month of stress became larger when initial mean cover per transect was < 20%, which suggested that the ratio of aboveground to belowground tissues in the expanded and sparser beds led to respiratory demand that was not met by photosynthesis. Despite intermittent improvements in light penetration, widespread recovery of seagrasses has not occurred potentially due to detrimental feedbacks. For example, loss of seagrass exposed sediments to waves, and the resulting disturbance may have hampered recruitment of new shoots. The same decreases also made 58–88% of the carbon, nitrogen, and phosphorus in seagrass tissue available to other primary producers. These nutrients did not enhance growth of epiphytes, whose biomass decreased by ∼42%, but they apparently fueled blooms of phytoplankton, with mean chlorophyll-a concentrations increasing by > 900%. Such intense blooms increased shading and loss of seagrasses. Fortunately, data showed that patches of seagrasses at depths of 0.5–0.9 m persisted for 22–24 years, which suggested that this depth zone could hold the key to recovery. Nevertheless, optimistic estimates predict recovery could take 12–17 years. Such a long-term, widespread loss of a key structural habitat may generate multiple adverse effects in the system, and mitigating such effects may entail planting seagrasses to accelerate recovery.

Foraging ecology of critically endangered Eastern Pacific hawksbill sea turtles (Eretmochelys imbricata) in the Gulf of California, Mexico

The Eastern Pacific hawksbill sea turtle population is one of the most endangered of all sea turtle species. Here, we examine the foraging ecology of 47 hawksbill turtles (40.5–90.3 cm CCL, mean = 54.1 ± 10.1 cm) around Isla San José, Gulf of California, Mexico by integrating information from passive acoustic telemetry, behavior recordings, fecal analysis, and habitat surveys. Tagged hawkbill turtles exhibited high site fidelity over months and years (tracking duration 1–1490 days, mean = 255 ± 373 days) to the location and benthic habitat where individuals were initially caught. Diet was dominated by benthic invertebrates and algae including sponges, algae, tunicates, and mangrove roots. The mean percent cover of these benthic food items was significantly greater in the mangrove estuary than in adjacent rocky and sandy reef habitats. The Isla San José foraging ground is a high-use area for hawksbills and should be granted national protection status.

Settling in: Reintroduced Persian Fallow Deer Adjust the Borders and Habitats of Their Home-Range During the First 5 Years Post Release

Translocated animals typically find themselves in a novel environment in which they must establish a home range in a manner that will maximize their fitness. We hypothesized that the initial establishment of a home range is followed by adjustments expressed as home range shifting, and occurs as familiarity with the landscape increases, until the home range is stabilized. We studied the process of home range shifting in 42 female Persian fallow deer (Dama mesopotamica) reintroduced into the Galilee, Israel over a period of 2–5 years. We used changes in the degree of home range overlap between consecutive years as an indicator of stabilization. We then compared how the mean percent cover of the key vegetation types (woodland, scrubland and open pastures) differed between the areas abandoned in the first year's home range and the areas added to the last year's home range relative to the first (using a weighted paired t-test). We also compared the distribution (using χ2 test of independence and Levene's test for homogeneity of variance) of %cover of the 3 vegetation types between the first and last year's home range. The average home range overlap increased over the 5 years following the first release. During the first-year post release, deer avoided open pastures and preferred woodland. In later years deer increase in the % open pastures (weighted t-test: p < 0.001) and decreased the % woodland cover (weighted t-test: p = 0.07) by abandoning areas with little open pasture and steeper terrain and moving into areas with more open pasture and moderate terrain. Variance of the cover types across individuals increased with time. We conclude that the home ranges of the reintroduced deer stabilized with time. The changes in vegetation and slope are driven by time-dependent changing needs reflecting a tradeoff between safety (refuge) and foraging. Our findings suggest that using the initially established home range to determine species preferences can create a misleading picture of what the optimal home range of the species really is. Individual variation in term of preferences can take a few years to be expressed due to the initial high-risk perceived by individuals in a novel environment.

Environmental associations and effects of disturbances by common wombats in alpine Tasmania

AbstractThe common wombat (Vombatus ursinus) is the largest extant fossorial mammal in Tasmania. Fossorial mammals have substantial edaphic and geomorphic effects, which, in turn can affect vegetation. We asked whether wombat disturbances were associated with particular environments in an alpine environment in Tasmania, and whether, and to what degree, they altered topography, soil or vegetation. Soil analyses, vegetation surveys and topographic transects were used to test for the effects of wombat activity. We contrasted toilets and controls. We compared adjacent burrows, mounds and paths. We also mapped burrows and animal trails. Wombat burrowing created distinct topography and was linked to feeding areas by path systems. There was no difference in bulk density, pH or phosphorus among burrow mounds, paths and undisturbed areas. Burrow mounds, usually used as toilets, were higher in nitrogen (mg L−1) (9. 8 ± 6.3) than either paths (2.3 ± 2.0) or controls (1.08 mg L−1 ± 1.5). Herbs were favoured by wombat disturbance, having a mean percentage cover of 27.8 ± 4.1 on burrow mounds compared to 14 ± 2.69 on controls, and a mean percentage cover of 51.6 ± 7.8 in toilets compared to 25.6 ± 4.8 in control plots. In contrast, shrubs have greater percentage cover in controls than on mounds (47.2 ± 12.0 cf. 12.7 ± 5.0) and toilets (37.3 ± 10 cf. 17.8 ± 6.5). Overall, wombat activity and modification of the alpine environment were concentrated in grassy vegetation above the winter water table, although paths, burrows and toilets extended into less grassy alpine communities. Our results imply that common wombats have a major role in engineering topography and soils with subsequent effects on vegetation, directly affecting at least 1.2% of the study area. Their reduction, or loss, is likely to lead to substantial changes in patterns of geodiversity and biodiversity.

The Status of the Coral Reefs of the Jaffna Peninsula (Northern Sri Lanka), with 36 Coral Species New to Sri Lanka Confirmed by DNA Bar-Coding

Sri Lanka, an island nation located off the southeast coast of the Indian sub-continent, has an unappreciated diversity of corals and other reef organisms. In particular, knowledge of the status of coral reefs in its northern region has been limited due to 30 years of civil war. From March 2017 to August 2018, we carried out baseline surveys at selected sites on the northern coastline of the Jaffna Peninsula and around the four largest islands in Palk Bay. The mean percentage cover of live coral was 49 ± 7.25% along the northern coast and 27 ± 5.3% on the islands. Bleaching events and intense fishing activities have most likely resulted in the occurrence of dead corals at most sites (coral mortality index > 0.33). However, all sites were characterised by high values of diversity (H’ ≥ 2.3) and evenness (E ≥ 0.8). The diversity index increased significantly with increasing coral cover on the northern coast but showed the opposite trend on the island sites. One hundred and thirteen species of scleractinian corals, representing 16 families and 39 genera, were recorded, as well as seven soft coral genera. Thirty-six of the scleractinian coral species were identified for the first time on the island of Sri Lanka. DNA barcoding using the mitochondrial cytochrome oxidase subunit I gene (COI) was employed to secure genetic confirmation of a few difficult-to-distinguish new records: Acropora aspera, Acropora digitifera, Acropora gemmifera, Montipora flabellata, and Echinopora gemmacea.

Changes in Herbaceous Species Variables After Enhanced Hunting Effort for White-tailed Deer in Soldiers Delight Serpentine Ecosystem in Maryland

Soldiers Delight Natural Environment Area and Wildlands, a biodiversity hotspot in the Maryland piedmont, conserves an endangered serpentine oak savanna (“barren”) ecosystem with numerous rare, threatened, and endangered species. White-tailed deer became conspicuous during daylight hours circa 1994. In 2008, a helicopter-mounted forward-looking infrared camera (FLIR) survey estimated 36 deer/km2 (93 deer/mi2). A sharpshooter harvest was conducted in 2014, and public hunting was expanded beginning with the 2014–2015 season. This study investigated changes in percent cover, frequency, and importance percentage of herbaceous species using site data collected in 1993 and 1994 when deer were becoming conspicuous, in 2011 when deer density was extremely high, and in 2018 and 2019 after four to five years of expanded hunting effort. In addition, the level of impact to serpentine aster (Symphyotrichum depauperatum), an endangered serpentine endemic, was quantified using caged and uncaged plants. Gray goldenrod (Solidago nemoralis), common in 1993 and 1994, occurred in only one of the 37 plots in 2011 and none in 2018 and 2019. Serpentine aster had almost disappeared from all plots by 2011, but in 2019 was within 50% of 1993 mean percent cover levels. Number of flower heads and main stem length of serpentine aster were significantly different between caged and uncaged plants, except during the three years following the sharpshooter harvest. Data indicate that deer herbivory will continue to be excessive with only regulated public hunting. To prevent species extirpation, public hunting will need to be supplemented by additional deer reduction.

Distribution and Diversity of Living Natural Resources from the Most Northern Red Sea Islands, Egypt: I- Hard and Soft Corals

The present study is a part of a monitoring program of the most important living natural resources, investigating the substrate cover distribution in the most northern islands of the Egyptian Red Sea. These resources include both hard and soft corals. This study was made during winter 2017 using Line Intercept Transact (LIT) to monitor the diversity and distribution of those resources. Eight islands located at the entrance of the Suez Gulf were surveyed using standard methods. Monitoring work for the hard and soft corals using transect was done by diving and snorkeling in the study areas. In the current study, the highest percentage cover of hard corals was 84 % recorded at Ghanim Island compared with the lowest cover of 41.3 %, estimated at Ashrafi Island, with mean percentage cover for all Islands averaged 60.1%. Acropora and Stylophora were the most abundant hard coral genera with a percentage cover of 35.8% and 17.6 %, respectively. Soft corals were the highest at Tawila Island with a percentage cover of 6% and the Nephthea was the highest soft coral genera with a percentage cove of 1.0 %. The monitoring work showed the diversity and distribution of these natural resources, especially coral reefs, and the extent to which these resources are affected by human activities, especially tourism activities, and also extraction and drilling for oil near the study areas. Observations on hard and soft corals in the study areas may be useful and important in the development of those areas in the future.

Scaling-up individual-level allometric equations to predict stand-level fuel loading in Mediterranean shrublands

Allometric biomass equations developed for individual shrubs can be applied to estimate shrubland fuels from measurements of cover and average height by species. Shrubs are a major component of surface fuels in many fire-prone ecosystems. Shrub fuel loading is often estimated by “double sampling”, where data from a destructive vegetation survey is used to model vegetation-fuel relationships (development phase), and these relationships are then applied to vegetation data from a second survey (application phase). Vegetation-fuel relationships can be modeled at different levels of vegetation detail, from individual plants to stands, but the increased effort of detailed measurements may compromise large-scale applications. To facilitate fuel loading assessments in Mediterranean shrublands, we present and test a novel method to estimate stand-level shrub loading that consists in applying individual-level allometric equations to vegetation plot data collected by measuring the percent cover and mean height of each shrub species. We used individual-level data (i.e., plant dimensions and dry weights) to develop allometric equations for total and fine (leaves and branches < 6 mm) biomass of 26 Mediterranean shrub species. We then evaluated the accuracy and precision of the proposed method in comparison to an approach assuming constant bulk density, using data from 131 vegetation plots and taking as benchmark stand-level loading estimates derived by aggregation of individual biomass allometric estimates. A second set of 13 plots was used to quantify the additional error derived from visual estimation of species mean height and cover. The performance of species-specific models was acceptable in estimating total and fine biomass at the individual level. When based on species mean height and cover data, stand-level fuel loading estimates calculated using the proposed method had a better precision and accuracy than those obtained using bulk density values (− 4 vs. + 39% in relative bias; 10 vs. 40% in relative MAE). Visual estimation of species mean height and percent cover led to 10 and 16% increase in MAE for species loading estimates of total and fine fuels, respectively, with respect to estimates obtained without this source of error. Our approach to estimate shrub loading allows combining fast species-level vegetation sampling with the flexibility of individual-level allometries to model to size-related variations of bulk density.

Cohesive framework for modelling plant cover class data

Abstract The study of plant distribution and abundance is a fundamental pursuit in ecology and conservation biology. Measuring plant abundance by visually assessing percent cover and recording a cover class is a common field method that yields ordinal data. Statistical models for ordinal data exist but entail cumbersome interpretations and sometimes restrictive assumptions. We propose a Bayesian hierarchical framework for analysing cover class data that allows for linking ordinal observations to a latent beta distribution and accounts for zero inflation. Harnessing a latent beta distribution supports interpreting changes in abundance in terms of mean percent cover rather than odds ratios of cumulative cover classes as for cumulative link models. The zero augmentation allows for simultaneous inferences on both occurrence (distribution) and abundance. We show how our model can account for true and false zeros, misclassification of cover classes, multiple species and hierarchical sampling designs, using empirical examples and simulations. Simulated observation errors, when ignored, led to models overestimating abundance and underestimating occurrence. Based on simulations, we found no substantial difference between mean percent cover estimates when analyzing ordinal cover classes versus continuous percent cover as the response. Our empirical datasets displayed high probability of detection (&gt;0.85 on average for all species), likely due to the sampling design used and training of observers. Probability of occurrence was slightly underestimated for bare ground, Artemisia tridentata, Elycap medusae, and Poa secunda using a model that ignored imperfect detection. Estimated mean percent cover was not substantially impacted by ignoring measurement error for five plant species and bare ground. Our modelling framework for cover class data allows for an explicit separation of distribution from abundance and, importantly, allows for interpreting species–environment relationships in terms of variation in mean percent cover as compared to cumulative odds ratios. The beta distribution inherently accommodates heteroscedasticity and skewness, statistical properties that are a consequence of spatially aggregated patterns common to plant survey data. Recording cover classes provides a reliable, efficient way to measure plants and our simulations suggest little loss of information compared to assuming continuous percent cover. We provide JAGS and Stan model code for implementation.

Epiphyte Diversity, Abundance, and Distribution in an Old Sitka Spruce Crown

Preserving biodiversity in remaining old-growth forests is a high priority for many land managers. To this end, we inventoried the diversity, abundance, and distribution of epiphyte species in one 318-year-old, 86 m tall Picea sitchensis tree on the north coast of California. In 39 plots, we recorded species present and mean percent cover for each species. Our findings include the following: 1) 68 epiphyte species were found in this one tree; 2) epiphyte diversity increased with height; 3) lichens had the highest diversity of all epiphyte classes; and 4) mosses had the highest percent cover of all epiphyte classes. These findings highlight the capacity for old trees to serve as reservoirs of biodiversity in younger forests.

Seagrass meadow cover and species composition drive the abundance of Eurasian wigeon (Mareca penelope L.) in a lagoon ecosystem of the northern Adriatic Sea

A comprehensive understanding of the interactions between primary producers and consumers plays an important role for the conservation of sensitive ecosystems such as lagoons. In this light, we studied the relationships between the flocks' size of Mareca penelope and the distribution of three seagrass species (Cymodocea nodosa, Zoostera marina and Nanozostera noltei) occurring in the Marano and Grado lagoon (Northern Adriatic Sea). Twelve bird monitoring areas were monthly surveyed for 3 years whereas seagrass distribution data were collected for the whole lagoon in the following years. The overall number of individuals of M. penelope was related to seagrass meadow extension and species cover by using a multiscale approach in four circle buffers (with radius of 500, 750, 1,000 and 1,250 m). Among the considered scales, the 750 m radius scale showed the best performance. The overall number of M. penelope increased where the occupied area by seagrass meadows was larger. Results also showed that when C. nodosa mean percentage cover increased the number of M. penelope decreased, while if N. noltei mean percentage cover increased also M. penelope number increased. Z. marina showed a negligible influence for all the tested scales. Our findings demonstrate that M. penelope populations depend not only on the extension of seagrass meadows but also on their species assembly, evidencing that M. penelope seem to prefer N. noltei stands, avoiding meadows with high abundance of C. nodosa.

Vegetation response to fire and roller-chopping in the south-west of Buenos Aires, Argentina

The objective of this work was to study the effect of acontrolled fire and/or roller-chopping on foliar cover and density ofthe most conspicuous woody and forage perennial grass species inthe south of the Phytogeographical Province of the Monte, Argentina.All control treatments reduced the woody species mean percentagecover. This reduction persisted during the whole study period.Nevertheless, the woody species tended to recover their percentagecover towards the end of study. At the end of the study period, significantdifferences (P 0.05) in woody species mean density were detectedamong treatments throughout the study period. At the end of thestudy period, the foliar cover and density of desirable perennial grassspecies was higher (P 0.05) were detected in intermediate perennial grassesfoliar cover and density among treatments. Our results suggest thatthe reduction of the woody species cover might encourage increasedthe foliar cover and density of desirable perennial grass species. Theuse of the controlled fire and/or roller-chopping, with proper grazingmanagement, may be the key factor to reduce woody species influenceand improve rangelands condition in the Monte region.