NMDS Ordination Research Articles

Trophic functioning of macrobenthic fauna in a tropical acidified Bornean estuary (Southeast Asia)

The trophic structure of a community is used to infer ecosystem functioning (e.g. energy transfer and nutrient cycling). Here the trophic structure of the benthic infaunal and epifaunal communities in the Brunei Estuary are characterized, and their distribution along an estuarine pH gradient is analyzed using univariate and multivariate techniques. This analysis revealed that surface deposit feeders (e.g., polychaetes) were numerically dominant within the infaunal communities whereas in the epifaunal communities filter feeders (e.g., bivalves) were highly abundant. Species richness for almost all trophic groups increased toward the lower estuary, except for omnivores in the epifaunal communities, which decreased markedly. Both Analysis of Variance (ANOVA) and Analysis of Similarities (ANOSIM) detected significant differences in the density of respective trophic groups among stations. Within infaunal communities, both Biological and Environmental procedure (BIO-ENV) and Canonical Correspondence Analysis (CCA) showed that trophic shifts were associated with environmental gradients. Surface-deposit feeders and omnivores were the most abundant macrobenthos of the upper estuary characterized by low salinity, low pH, and a higher percentage of mud particles. The proportion of filter feeders and carnivores increased with salinity/pH and sand. A more uniform distribution of trophic structure was found in the lower estuary, with high salinity and pH over sandy habitat. In contrast, within epifaunal trophic groups, the percentage of surface deposit feeders and omnivores declined, but filter feeders remarkably increased toward the sea. The proportion of carnivores remained similar at all stations. Non-Metric Multidimensional Scaling (nMDS) ordination for epifaunal trophic groups clearly demarcated higher salinity/pH stations from lower salinity/pH stations, suggesting different trophic compositions along the estuarine pH gradient.

Revision of the central Mediterranean xerothermic cliff vegetation

QUESTIONS: What are the syntaxonomic and synchorological patterns of the xerothermic chasmophytic vegetation in the central part of the Mediterranean Basin? What are the diagnostic species of the high‐rank syntaxa of Asplenietalia glandulosi, Onosmetalia frutescentis and Centaureo dalmaticae‐Campanuletalia pyramidalis? LOCATION: Mediterranean coastal and subcoastal areas of southern France, Italy, Malta, Slovenia, Croatia, Bosnia and Herzegovina, Montenegro, Albania and of mainland Greece. METHODS: The data set of 1,261 published releves was analysed using hierarchical clustering (Flexible Beta method), involving a series of data transformations. Indicator species analysis was used to select the best dendrogram solution and identify diagnostic taxa of the main clusters. The dendrogram was interpreted from a syntaxonomic point of view, using nomenclatural type releves as a basis. The NMDS ordination was performed in order to visualize the floristic relationships among associations and high‐rank syntaxa. MRPP was used to test for differences among alliances. RESULTS: The classification revealed four main clusters of releves representing the chasmophytic vegetation of southern France, Sardinia and the northwestern part of Italy (Asplenienalia glandulosi/Asplenietalia glandulosi), the southwestern part of Italy and Malta (Tinguarrenalia siculae/Asplenietalia glandulosi), the Adriatic Basin area (Centaureo dalmaticae‐Campanuletalia pyramidalis) and the southern Balkans (Onosmetalia frutescentis). The NMDS ordination confirmed the overall pattern, while MRPP showed significant differences among the alliances of the above‐mentioned orders and suborders. The lists of diagnostic taxa of the high‐rank syntaxa were revised according to a supra‐national perspective. CONCLUSIONS: The new syntaxonomic scheme provides a comprehensive overview of the chasmophytic vegetation of the central part of the Mediterranean Basin. This scheme mostly matches the recently published EuroVegChecklist, but also exhibits important novelties concerning the syntaxonomic position of some alliances (Dianthion rupicolae, Centaureion pentadactyli, Arenarion bertolonii and Caro‐Aurinion), and the floristic and chorological relationships among high‐rank syntaxa, with new revised sets of diagnostic taxa. This revision might be useful for further small‐scale phytosociological studies.

The trouble with stress: A flexible method for the evaluation of nonmetric multidimensional scaling

AbstractNonmetric multidimensional scaling (NMDS) is a powerful statistical tool which enables complex multivariate data sets to be visualized in a reduced number of dimensions. Users typically evaluate the fit of an NMDS ordination via ordination “stress” (i.e., data distortion) against a commonly accepted set of heuristic guidelines. However, these guidelines do not account for the mathematical relationship which links ordination stress to sample size. Consequently, researchers working with large data sets may unnecessarily present ordinations in an intractable number of dimensions, subdivide their data, or forego the use of NMDS entirely and lose the benefits of this highly flexible and useful technique. In order to overcome the limitations of these practices, we advocate for an alternative approach to the evaluation of NMDS ordination fit via the usage of permutation‐based ecological null models. We present the rationale for this approach from a theoretical basis, supported by a brief literature review, and an example usage of the methodology. Our literature review shows that NMDS analyses often far exceed the number of observations under which the original stress guidelines were formulated—with a significant increasing trend in recent decades. Adoption of a permutation‐based approach will consequently provide a more flexible and quantitative evaluation of NMDS fit and allow for the continued application of NMDS in an era of increasingly large datasets.

Soil propagule bank of ectomycorrhizal fungi associated with Masson pine (Pinus massoniana) grown in a manganese mine wasteland.

Ectomycorrhizal (ECM) fungal propagule bank could facilitate the regeneration and plantation of seedlings in disturbed area. In this study, Masson pine (Pinus massoniana) seedlings were used to bait the ECM fungal propagule bank buried in the soils collected from a manganese (Mn) mine wasteland and a non-polluted area in China. After 6-month growth, we found the seedlings grown in the Mn mine soil (Mn:3200 mg kg-1) did not display any toxicity symptoms. Based on morphotyping and ITS-PCR sequencing, we identified a total of 16 ECM fungal OTUs (operative taxonomic units) at 97% similarity threshold, among which 11 OTUs were recovered in the Mn mine soils and 14 in the non-polluted soil. Two soil types shared 9 OTUs and both of them were dominated by a Tylospora sp. Based on those soil propagule banks in Masson pine forests reported in previous, we speculated that some Atheliaceae species may be preferred in the soil propagule bank of some pine species, such as Masson pine. In addition, NMDS ordination displayed geographical position effects on soil propagule banks in five Masson pine forest from three sites at regional scale. In conclusion, Masson pine ECM seedlings could grow well in the Mn wasteland as a suitable tree species used for reforestation application in Mn mineland, in addition, Mn pollution did not alter the dominant ECM fungal species in the soil propagule banks.

Diatom diversity in some hot springs of northern Thailand

AbstractDiversity of hot spring diatoms in northern Thailand was studied. Forty-six diatom species were identified in eight localities. The dominant species according to high relative abundance were Diatomella balfouriana (41.7%), Achnanthidium exiguum (20.9%) and Anomoeoneis sphaerophora (11.2%). Moreover, Caloneis molaris, Craticula acidoclinata, Navicula subrhynchocephala and Pinnularia saprophila were recorded as species new to Thailand. The NMDS ordination revealed variation in species composition of eight different hot springs and correlation with the existing environmental variables. Silicon dioxide (SiO2), pH, conductivity, water temperature and total hardness were statistically significant factors affecting relative abundance of Achnanthidium exiguum, Amphora montana, Caloneis aequatorialis, Cocconeis placentula, Craticula cuspidata, Diploneis elliptica, Gomphonema affine, Gomphonema augur, Halamphora fontinalis, Planothidium lanceolatum, Pinnularia abaujensis, Sellaphora lanceolata and Stauroneis anceps.

BorealPicea abiesMires of Finland: Cajanderian Site Types and Compositional Gradients in Relation to Species Richness

We used classic sample plot data of Rauno Ruuhijarvi and Seppo Eurola from the early 1960s to compare Cajanderian site types of boreal Picea abies mires in Finland with a classification made with a multivariate method. Classic site types explained the compositional variation in the NMDS ordination better than the analysis, based on numerically derived clusters. Distinct compositional gradients were the poor—rich gradient and the peat thickness (paludification). Additionally, one could interpret a microtopographic gradient in the results. Our results, as well as some other studies support a view that climatic factors affect more than the bedrock the species richness in boreonemoral—boreal Picea abies mires of northern Europe. Soil chemical features (poor—rich gradient) and the microtopography modify the species richness at a site scale. Geographic speciesrichness centre of boreal-temperate Picea abies mires of Europe is unknown, but it is in relation at least to climate, to bedrock and to historical aspects.

Estimating the response of wildlife communities to coastal dune construction

Coastal ecosystems worldwide are being impacted by sea-level rise caused by climate change. As mitigation efforts increase to protect these threatened ecosystems, a deeper understanding of how wildlife adapt to coastal management techniques is needed. We monitored three constructed sand dunes (built in 2010 and 2014) and two natural dunes in central Florida from June 2015 through June 2016 to assess the impact of dune construction as a management technique on terrestrial vertebrates. Specifically, we tested if constructed dunes accumulated and maintained similar community composition and species richness to natural dunes. We used AHDriFT, a game camera-based trapping technique, to monitor terrestrial wildlife communities in both the natural and human-modified landscapes. After 4502 camera nights, we documented 2537 unique photo-capture events, comprised of 33 different species. Species communities were compared by constructing species accumulation curves for each dune type, and by modeling community similarity through multivariate hierarchical clustering. Species accumulation curves overlapped among all dune types, and the cluster analysis showed no pattern separating natural and constructed dunes. However, PERMANOVA found a difference between constructed and natural dunes, which was verified by a NMDS ordination that separated out constructed and natural dunes. Differences between dunes was likely driven by rare species, as commonly observed species overlapped across all dunes, including one protected species. Given the similarity between overall species richness, and that differences in community composition may be due to microhabitat variation and species rarity, we conclude that constructing dunes to increase coastal resilience does not negatively impact endemic wildlife in coastal zones and may provide suitable habitat for many wildlife species.

Plant diversity and composition of rice field bunds in Southeast Asia

Which plant species can be found on rice field bunds and what are the prevailing life forms? Which plant communities occur and what are the main environmental drivers and phytogeographic patterns shaping these communities? How do species diversity and composition differ between bunds and paddies? To answer these questions, 133 vegetation releves using the Braun-Blanquet method were collected in lowlands and uplands of Vietnam and the Philippines between 2012 and 2015. Soil samples were collected and farmers were interviewed. Properties of soil, climate, and geography were assessed, further structural parameters, landscape heterogeneity, seasonality, management and intensity of cultivation. Hierarchical UPGMA cluster analysis and NMDS ordinations were performed to visualize variation in plant community composition and the determinants. We found 302 vascular plant species, of which 94 species are red listed by the IUCN (under category “Least concern”). Therophytes and helophytes are the prevailing life forms. Six clusters of plant communities were classified, and temperature, soil acidity, land use intensity and nutrient availability were identified (according to relevance) as explanatory variables. Bunds revealed higher species richness than paddies and bunds in mountain areas were more species-rich than those in the lowlands. We conclude that the composition of bund communities provides valuable information on environmental and biogeographical conditions of the local rice landscapes, and that it is probably the best applicable and most reliable indicator of management intensity.

Influences of diel and tidal cycles on fish assemblage in eelgrass (Zostera marina) bed of southern Korea during autumn

Short-term tidal and diel variations of autumn fish assemblage in a Zostera marina bed were investigated using 3 h interval samplings for 24 h in both spring and neap tide using a small beam trawl. A total of 1 346 fishes belonging to 19 species were collected at spring tide, whereas 1 115 fishes belonging to 17 species were at neap tide. The common fish species were Nuchequula nuchalis, Acanthogobius flavimanus, Takifugu niphobles, Acentrogobius pflaumii, and Pholis nebulosa with the former three species dominating at spring tide, while the latter two species being abundant at neap tide. Diel variation in abundance was significant with higher abundance at night than day, but there were no significant differences between spring and neap tides, and between ebb and flood tides (three-way ANOVAs). Diel variation in the abundance of fishes may be influenced by tidal range and cycle, and day-night differences of food availability and behaviors of fishes indirectly. Non-metric multidimensional scaling (nMDS) ordination and analysis of similarity (ANOSIM) results revealed significant differences in species compositions both between day and night, and between spring and neap tide. Eelgrass beds are highly productive marine ecosystem, and thus, our results will contribute to conservation of seagrass ecosystem in the study area.

Seasonal and habitat structures of crustacean decapod assemblages associated withZostera marinabeds in northern Jinhae Bay, Korea

Crustacean decapod assemblages were surveyed inZostera marinabeds adjacent to tidal flats (ET) and rocky shore (ER), and in unvegetated habitats (UV). Decapod samples were collected monthly throughout 2002 using a small beam trawl from northern Jinhae Bay, Korea. Water temperature, salinity, eelgrass biomass, sediment composition and organic matter were also monitored to assess any correlation between environmental variables and decapod fauna. A total of 31 decapod species belonging to five taxa (three prawns, 13 caridean shrimps, one hermit crab, one mud shrimp and 13 crabs) were collected at three different habitats. To assess variations in decapod assemblages in relation to habitat type and season, various multivariate analyses were used. The dominant caridean shrimps werePalaemon macrodactylus, Alpheus digitalisandCrangon uritai,and the dominant crabs wereCharybdis japonica, Hemigrapsus penicillatusandCharybdis bimaculata. The number, abundance and diversity of decapod species varied greatly with habitat type and season, peaking in eelgrass beds and during spring, and showing the lowest catch rate in unvegetated habitat and during winter months. The nMDS ordination and multivariate analyses revealed that habitat type and season were determinant factors affecting the structure of decapod assemblages. Seasonal shifts in the abundance of decapods corresponded with changes in eelgrass biomass and loss on ignition (LOI), but not with water temperature or salinity.

Feeding Relationships among Six Seagrass-associated Fishes in the Northeastern Gwangyang Bay, Southern Korea

We conducted dietary analyses of six seagrass-associated fish species inhabiting northeastern Gwangyang Bay, Korea. These six species consumed a variety of benthic invertebrates and teleosts, but their preferences for different food resources varied. Although all species consumed crustaceans, the contributions of different crustacean taxa differed among the species’ diets. Caridean shrimps and crabs were a significant part of the Hexagrammos agrammus and H. otakii diets, respectively, while amphipods were consumed mainly by Sebastes inermis. Caridean shrimps and prawns were abundant within the Lateolabrax japonicas diet, but were not common prey resources for Pseudopleuronectes yokohamae or S. schlegelii. Polychaetes and ophiurids were ingested by P. yokohamae, and the former prey taxon also made moderate contributions to the diets of H. agrammus and L. japonicus. With the exception of P. yokohamae, the diets of all species included teleosts. Teleosts contributed the largest proportion of the S. schlegelii diet, followed by the S. inermis and L. japonicas diets; however, H. agrammus and H. otakii rarely consumed teleosts. Non-metric multidimensional scaling (nMDS) ordination plots and permutational analysis of variance (PERMANOVA) revealed the variation in dietary composition among species and the contributions of each prey taxon. These interspecific differences in diet increase the range of food resources available to these fishes, thereby reducing competition for resources within the fish community in this region.

Spatiotemporal patterns of the macrofaunal community structure in the East China Sea, off the coast of Zhejiang, China, and the impact of the Kuroshio Branch Current.

The Kuroshio Current intrudes in the bottom layer of the East China Sea continental shelf from the northeast of Taiwan via two bottom branches named the Nearshore Kuroshio Branch Current (NKBC, along the 60 m isobath) and the Offshore Kuroshio Branch Current (OKBC, along the 100 m isobath). However, knowledge on the macrofaunal responses to these bottom branches is limited. This study examined the variations in the benthic macrofaunal community in a section of the East China Sea under the influence of the NKBC. Seven sites corresponding to three regions (the west, middle and east region) were sampled using an Agassiz trawl net at a monthly rate from February to November 2015 (except in August). A total of 270 macrofaunal species were collected in this study. Cluster analysis and nMDS ordination revealed three communities: the inshore, Kuroshio and offshore communities, roughly corresponding to the west, middle and east of NKBC route. Significant differences in the species composition (one-way PERMANOVA) and diversity indices (one-way ANOVA) among the regions and communities were observed, while no statistically significant difference among the months was detected. The indicator species also varied among the communities, with Sternaspis scutata and Odontamblyopus rubicundus dominating the inshore community, Camatopsis rubida, Schizaster lacunosus and Craspidaster hesperus dominating the Kuroshio community, and Portunus argentatus, Champsodon snyderi and Coelorinchus multispinulosus dominating the offshore community. Some rare species (e.g., Neobythites sivicola) may indicate the passage of the NKBC better than the indicator species. A redundancy analysis was used to describe the relationship between the macrofaunal species and environmental variables in this study. Water depth and turbidity played important roles in the distribution of the macrofauna. S. scutata and O. rubicundus were associated with high turbidity and shallow depth, while Plesionika izumiae and P. argentatus were associated with low turbidity and deep depth. This study outlines the impact of the NKBC on the distribution patterns of the macrofaunal community of the East China Sea. More studies are needed to understand the detailed interactions between macrofauna and the NKBC in the future.

Variations in macrobenthic community at two stations in the southern Yellow Sea and relation to climate variability (2000–2013)

Decadal variations (2000–2013) in the macrobenthic community of the southern Yellow Sea were investigated based on the analysis of the community at two stations located basically along the 70 m depth contour. Significant decadal variations in community structure were found through cluster analysis, nMDS ordination and one-way ANOSIM. SIMPER analysis showed that the decadal community variations could be roughly attributed to the decrease of two species of Mollusks (Thyasira tokunagai and Nucula tenuis) and the increase of one echinoderm (Ophiura sarsii vadicola), one polychaete (Notomastus latericeus) and one bivalve (Portlandia japonica) at both stations. Redundancy analysis showed that the Pacific Decadal Oscillation and the Southern Oscillation Index were significant climate indices influencing the macrobenthic community structure in the southern Yellow Sea. Most of the species collected in 2000s showed a positive correlation with Pacific Decadal Oscillation at both stations, especially for cold water species Thyasira tokunagai, while most species in 2010s were positively correlated to Southern Oscillation Index, e.g. Portlandia japonica and Notomastus latericeus at station 1 and Sigambra bassi and Aricidea fragilis at station 2.

Microhabitat selection and distribution of functional feeding groups of mayfly larvae (Ephemeroptera) in lotic karst habitats

Research examining mayfly ecology in karst streams and rivers has increased in recent years, though microhabitat preferences remain poorly characterized. We examined mayfly assemblage taxonomy, functional feeding groups and microhabitat preferences in two contrasting lotic Dinaric karst catchments, one pristine and one anthropogenically impacted. At monthly intervals over a one-year period, all major microhabitats (i.e.dominated by boulders, cobbles, sand, silt, mosses, or angiosperms) were sampled at sites spanning springs, upper, middle and lower river reaches, and tufa barriers. In both catchments, mayfly species richness was comparable among microhabitats, while mayfly abundance was highest on mosses and lowest on silt. NMDS ordination did not group assemblages according to microhabitat type, which may reflect the greater influence of physical and chemical water properties. In both catchments and all microhabitats, mayfly assemblages were dominated by grazers/scrapers at upstream sites and by detritivores at downstream sites. Active filter feeders were more abundant in microhabitats with silt substrates and lower current velocities. This study demonstrated that certain mayfly species strongly preferred a specific microhabitat type, reflecting their water current preferences and feeding strategies, while other species shifted between microhabitats, likely in search of food resources and shelter. The results emphasize the importance of habitat heterogeneity in supporting diverse communities in karst rivers.

Rooting of cuttings of the wild Indian almond tree (Sterculia foetida) enhanced by the application of indole-3-butyric acid (IBA) under leafy and non-leafy conditions

Abstracts Vegetative propagation is one of the important conservation means of wild, native, and threatened tree species. The experiment finds out the opportunities of rooting of leafy and non-leafy branch cuttings of Sterculia foetida with different concentration of IBA in a non-mist propagator. Five treatments were used for this experiment. The treatments were T0 (control), T1 (0.2% IBA), T2 (0.4% IBA), T3 (0.6% IBA) and T4 (0.8% IBA). The experiment revealed the importance using IBA treatments rather than the types of cuttings used. The experiment showed that the highest rooting percent was observed in 0.8%IBA concentration and lowest rooting percent was observed in control in both leafy and non-leafy condition. Rooting success varied among the IBA treatments from 33.1% to 86.2% in leafy and 34.5 to 82.6% in non-leafy cuttings. The two way analysis of variance (ANOVA) showed no significant difference (p > 0.05) among type of cuttings (leafless / leafy) but it showed significant difference (p 0.05) but there were significant differences (p 0.05). The overall survival of rooted cutting was higher in 0.8% IBA concentration (66.6 in leafy and 69.3% in non-leafy cuttings) and lower in control. The two way ANOVA also showed significant differences on survival of rooted cutting among the treatments but no significant difference between leafy and non-leafy cuttings. Tukey post-hoc test showed the comparisons of different mean values of treatments of rooting success, sprouting success of rooted cuttings and overall survival. NMDS ordination plot showed rooting and sprouting success parameters and how the parameters of leafy and non-leafy cutting shifted from each other. On the basis of this study, 0.8% IBA may be applied for rooting of cuttings of Sterculia foetida.

Topography and soil type are critical to understanding how bird and herpetofaunal communities persist in forest fragments of tropical China

Habitat fragmentation in heterogeneous landscapes is a non-random process, with farmers selecting lands with flat topography and fertile soils. To understand the persistence of biodiversity in forest fragments in such landscapes, it is necessary to distinguish between factors associated with fragmentation (e.g., area and distance to edge) and characteristics of where fragments are located (e.g., topography and soil conditions). Location factors have been previously demonstrated to be important in explaining the persistence of trees in fragments in the environmentally diverse region of Xishuangbanna, China (Liu and Slik, Biological Conservation, 2014). However, it is unknown how location factors influence more mobile, short-lived organisms. We sampled 42 of the previous study's plots for birds and herpetofauna across two years. A multi-model inference approach indicated that topography was the most important predictor of amphibian diversity, with valleys having more than three times the species in other locations. Topography interacted with fragment size for bird species, and particularly forest interior (FI) species: diversity in valley plots climbed strongly with fragment area, but the relationship between area and diversity was less strong in other locations. Soil type (limestone or not) most strongly influenced the score of plots on the first axis of a NMDS ordination of FI birds. These results suggest that managers should consider the location of fragments in the landscape in prioritizing forest fragments for protection. For Xishuangbanna, all valley fragments are important to protect amphibians; amalgamating them into large fragments >1000ha will make them most useful for bird conservation.

Gastrointestinal Cancer

Gastrointestinal Cancer

Alpine cushion plants have species–specific effects on microhabitat and community structure in the tropical Andes

AbstractQuestionSpecies–specific interactions can connect particular species to others, which has important implications for species interdependence and co‐existence. However, species‐specific effects of ecosystem engineers remain little explored, particularly in the alpine tropics. We investigated the effects of two cushion plants with subtle differences in morphological traits in a tropical Andean ecosystem. We asked whether these foundation species differed in their effects on local abiotic factors, species richness and the structure of plant assemblages growing within them.LocationLa Culata National Park, northern tropical Andes, Venezuela.MethodsWe determined shallow soil temperature, soil organic matter and water content within two co‐existing cushion species, the larger and more compact Azorella julianii and the smaller and denser Arenaria musciformis, and in adjacent open areas. We also recorded the total number of plant species growing within both cushion species, and in paired open areas at three sites. We then compared local species richness, total plant abundance and the abundance of each species within cushions and outside using the relative interaction index (RII), and community dissimilarity patterns using NMDS ordination. We also compared species accumulation curves across sites between the cushions and open areas.ResultsBoth cushions had similar positive effects on soil organic matter, but soil water content was increased only with Azorella. Both cushions had a positive effect on local species richness and total plant abundance. In addition, both species significantly modified species abundance patterns, showing a positive association with several species, many of them grasses. However, facilitative effects on other species were generally stronger for Azorella than Arenaria. Moreover, community structure of plants growing within the two cushion plants differed. The exotic invader Rumex acetosella increased in abundance within Azorella but not Arenaria.ConclusionsWe found evidence for species‐specific effects of ecosystem engineers in the alpine tropics; two cushion species with subtly contrasting traits had different effects on microhabitat conditions and plant assemblages. This could in turn increase abiotic and biotic heterogeneity and promote species co‐existence and emphasizes interdependence among species in alpine plant communities.

Subtle differences in birds detected between organic and nonorganic farms in Saskatchewan Prairie Parklands by farm pair and bird functional group

Abstract Organic farming may be more beneficial to biodiversity than nonorganic farming but the comparison is often confounded by regional within-farm and landscape differences. We compared breeding bird species composition and abundance on 10 farm pairs of each type matched at the site level for land cover in the prairie parklands of Saskatchewan, Canada in 1990. Land cover was measured around bird point counts at two extents; ‘site’ (6.3 ha area) and ‘field’ (16.3 ha area). We pooled species into functional groups; linear mixed models showed no significant differences between farm types for species richness but that all birds, migratory birds using crops and aerial insectivores were more abundant on organic farms. A permutational multivariate analysis of variance demonstrated that farm type did not have a significant overall effect on compositional similarity but that pairwise differences existed between about half of the farm pairs (the direction of differences in beta diversity was not consistent between organic and nonorganic farms according to tests for the homogeneity of multivariate dispersions). Farm-pair differences were more pronounced for all birds and for migratory bird species using crops, migratory birds consuming grains and ground feeders, but not grassland birds. nMDS ordinations suggested that there was more variation in species composition and abundance on organic farms than nonorganic ones but the difference was not significant. Distance-based redundancy analysis (dbRDA) was used to examine the main drivers of bird species composition and abundance and to see which extent was most important; land cover at the field extent was more important than land cover at the site extent or the farming practices measured. The most important field-extent land cover was the amount of native grassland, woodland (including shelterbelts) and wetlands. After controlling for significant field-extent land cover, seed treatment, herbicide use, and number of passes were significant. At the site extent, greater non-crop heterogeneity had a significantly positive effect on abundance and species richness of several groups (e.g., grassland birds, migratory granivores, ground feeders, ground nesters) but a negative effect on richness of woodland birds and abundance of aerial insectivores. Relationships with crop heterogeneity were mostly negative and non-significant. Overall land cover heterogeneity at the site level was positively related to the richness of grassland birds. In contrast at the field extent, non-crop heterogeneity did not have any significant effects on the richness and abundance of any functional group. Crop heterogeneity had a significantly negative effect on aerial insectivore richness and abundance. In the early 1990s, differences in birds between organic and nonorganic farms in Saskatchewan were evident but subtle and variable among farms, and apparently most related to land cover-bird assemblage interactions/relationships.

Natural or assisted succession as approach of forest recovery on abandoned lands with different land use history in the Andes of Southern Ecuador

Forest recovery on disturbed areas is of special significance in the Ecuadorian Andes, where deforestation is a serious problem. Natural diachronic succession was evaluated on three large plots or sites, differing in their land use and vegetation composition, one is dominated by grass species on an abandoned pasture (Pasture site), the other two are post-fire vegetation dominated by bracken (Bracken site) and various shrubs (Shrub site). Additionally, we assessed the effectiveness of manual removal of competitive herbaceous species to accelerate forest recovery. Monitoring was done in 2003, 2005 and 2007 on 48 subplots of 116 m2 each recording species richness and woody-species density. Results showed that the Pasture site demonstrated a competitive effect of exotic grasses on woody species recruitment with much lower species recruitment and density, suggesting serious inhibition of natural forest regeneration and an unclear successional trajectory. The Bracken and Shrub sites became significantly similar floristically and there is evidence for a marked facilitation of woody plant recruitment correlated with light availability on the ground. Both sites showed characteristics of classic succession, with Shrub showing a higher species richness and density while late-successional species are poorly represented on the Bracken site. However, NMDS ordination using species density showed that the two trajectories may not be converging towards a common “final state”. Manual weeding was ineffective for accelerating forest recovery. These results suggest that the main limiting factor for the recruitment of woody species on the Pasture site is strong grass competition and must be addressed before seed availability, while seed availability seems to be the constraining factor for Bracken and Shrub site development, thus direct seeding or planting may be effective in accelerating forest recovery.