Acta Oecologica

Earthworms contribute to ecosystem process in no-till systems with high crop rotation intensity in Argentina Publication date: July 2019 Source: Acta Oecologica, Volume 98 Author(s): J.C. Bedano, F. Vaquero, A. Domínguez, M.P. Rodríguez, L. Wall, P. Lavelle Abstract In the Pampas region of Argentina agriculture is dominated by intensive no-till (NT) soybean cropping which produce negative consequences on soil quality. A group of farmers started to use the Good Agricultural Practices (GAP) which include a higher crop rotation, use of winter cover crops and nutrient restoration. In this NT system earthworms have a significant role in soil functioning, particularly in organic matter cycling and soil structure formation. The aim of this paper was to examine the contribution of earthworm activity to the process of C incorporation and soil structure maintenance in soils with different NT variants of: NT with GAP for 30 years (NT + r30); NT with some of the GAP for 12 years (NT-r12) and NT with soybean monoculture (NTm). Also a natural grassland (NA) was sampled as a reference. Earthworm aggregates were obtained by gently separating them from surrounding soil. Fine (HOC) and coarse (POC) organic matter fractions, water-stable aggregates (WSA) and mean weight diameter (MWD) were calculated for earthworm aggregates and bulk soil. In all sites only one species (Aporrectodea caliginosa) was found, with higher density in the NA, followed by NT + r30, that had about 9 times more earthworms than NTm. The number of earthworm aggregates was higher in the NT + r30 followed by the NA, both showing differences with the other NT systems. The earthworm aggregates in NA and NT + r30 had significantly more POC than the surrounding soil (230% increase in NA and 100% NT + r30). Earthworm casts had higher values of MWD and WSA than physical soil aggregates in both NA and NT + r30 management treatments. Our results show the existence of a positive feedback loop we called earthworm-driven virtuous cycle. The increase in earthworm abundance promotes higher production of earthworm aggregates which are richer in organic matter and more water stable than the surrounding soil. This has favourable results in terms of soil quality but also increase crop yields (57% in maize and 18% in soybean), by means of biologically mediated soil processes, which is a highly desirable way to sustainability of agricultural production. Farmers, politicians and the whole society should pay more attention to soil as a key component supporting agricultural production by means of internal biological soil functioning.

Heterogeneity in millipede communities (Diplopoda) within a forest–forest edge–meadow habitat complex Publication date: July 2019 Source: Acta Oecologica, Volume 98 Author(s): Slavomír Stašiov, Vladimír Kubovčík, Marek Čiliak, Andrea Diviaková, Ivan Lukáčik, Vladimír Pätoprstý, Martin Dovciak Abstract The positive influence of heterogeneity in vegetation and land-use on animal diversity is generally well established, but it has not been conclusively confirmed yet in millipede communities inhabiting karst canyons where biodiversity is to large extent determined by variation in topography (e.g., elevation). We studied how millipede assemblages (Diplopoda) vary between forest, forest edge, and meadow habitats in this specific karst environment. We sampled millipedes by pitfall trapping during two vegetation seasons (from March to October in 2001 and 2002) in approximately monthly intervals across nine sites in Central Slovakia (Veľká Fatra Mts). In total, 951 individuals belonging to 12 species from 6 families and 10 orders were collected. The dominant species was Unciger foetidus, which was also one of the two most frequent species along with Polydesmus complanatus. Although the total number of captured millipedes was greatest on forest edges (395 individuals), intermediate in meadows, and lowest in forests (214 individuals), millipede abundance and species composition varied considerably within each habitat type among the sites. Total millipede species richness in meadow and forest edge habitats was the same (11 species) and it was lower in forest habitats (7 species), while species diversity (Shannon's H′) and equitability (E) were greatest in meadows. Millipede diversity measures (species richness or equitability) were correlated positively with species richness of herb layer and negatively with shrub layer equitability, soil conductivity, and soil phosphorus. Thus, we found complex patterns of heterogeneity in millipede community composition and richness across studied habitats and elevations that were driven by habitat type and plant community and soil characteristics. While millipede abundance patterns varied, open habitats supported most species-rich millipede communities at lower elevations, while forest edges were most species-rich at the high elevation.

Fear alone reduces energy processing by resident ‘keystone’ prey threatened by an invader; a non-consumptive effect of ‘killer shrimp’ invasion of freshwater ecosystems is revealed Publication date: July 2019 Source: Acta Oecologica, Volume 98 Author(s): Calum MacNeil, Mark Briffa Abstract Non-consumptive effects (NCEs) of predators – so called ‘fear’ responses – encompass costly antipredator behaviours, such as reduced feeding efficiency. NCEs can influence prey population dynamics and community structure, if prey are ‘keystone’ species such as Gammarus spp. amphipod ‘shrimps’. These freshwater macroinvertebrates have the ecosystem functional role of shredding fallen leaf litter, making it accessible to other taxa. Across Europe, the invasive predatory ‘killer shrimp’ Dikerogammarus villosus is replacing resident Gammarus spp., potentially threatening this vital ecosystem function. While predation (consumptive effects (CEs)) of this invader has been well studied, for the first time we test whether NCEs can be evident in prey only exposed to D. villosus presence and whether this could potentially impact on the prey's functional role. In mesocosms, exposure to constrained D. villosus did not result in mortalities of any of three Gammarus prey species but the leaf shredding efficiencies of all prey were significantly reduced compared to a control treatment. This clear NCE has the potential to propagate through the ecological community via decreased energy processing. This study demonstrates the potential for fear of invasive predator presence alone to impact on ecosystem function.

Determinants of spatial patterns of plant diversity depend on the biogeographical affinities of the taxa − a case study in Northwest Yunnan, Southwest China Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Jianmeng Feng Abstract The influence of the biogeographical affinities of taxa on the spatial determinants of plant diversity remains largely unknown. I explored the spatial patterns of tropical and temperate plant diversity in Northwest Yunnan and their primary determinants. Generalized linear models (GLMs) and variance partitioning were used to investigate the influences of predictors. Temperate genus diversity significantly increased with latitude, whereas tropical genus diversity did not show any obvious latitudinal trends. Proportions of tropical genera decreased with latitude, whereas those of temperate genera were on the contrary. Environment heterogeneity explained higher percentage of the spatial variation of temperate genus diversity than for that of tropical genus diversity. It may imply that the influence of environment heterogeneity on plant diversity may depend on the taxa's biogeographic affinities, which might modify the exploitation of environment heterogeneity, though the flora diversification induced by the uplifting of the Tibet Plateau may also play important roles. Climate predictors explained higher percentages of variation in the proportions of tropical genera than for the variations in tropical genus diversity. It may suggest that compared with the associations between genus diversity with tropical affinities and climatic conditions, the associations between the proportions of tropical plants and climatic conditions might more accurately reflect niche conservatism of tropical plants in the study area.

Microclimatic effects on the incubation success, hatchling morphology and locomotor performance of marine turtles Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Melissa N. Staines, David T. Booth, Colin J. Limpus Abstract Global atmospheric temperatures are predicted to rapidly increase within the next hundred years, consequently altering the microclimates of the sand dune environment where marine turtles lay their eggs. High nest temperatures can increase embryonic mortality, decrease hatchling vigour and size (i.e. quality), and also feminises the sex-ratio of clutches. Sand composition, vegetation cover, rainfall and sun exposure affect the temperature of sand surrounding a nest, however the effect of this variability in the beach environment on the incubation success of a sea turtle clutch is still relatively unknown. We conducted a manipulative study on loggerhead turtle nests at Mon Repos, Queensland, Australia, to investigate the effect of ground-cover vegetation vs bare sand and tree-shade vs no shade on incubation success, hatchling morphology and hatchling locomotor performance. Twenty-four nests were used in a two-factor experimental design, with tree-shade/sun and, ground-cover vegetated/cleared as fixed factors. Sun-exposed nests experienced higher nest temperatures (∼2 °C warmer), shorter incubation periods and poorer incubation success than those in tree-shade. Ground-cover-vegetated nests in tree-shade had lower hatching and emergence success (73%, 66% respectively) than sun-exposed nests placed in sites cleared of ground-cover vegetation (79%, 83% respectively). Hatchlings that emerged from cooler, tree-shaded nests were also larger and crawled faster than hatchlings from sun-exposed nests. We suggest for conservation projects on naturally ‘hot’ beaches, active management strategies such as selective groundcover vegetation removal and increased shading could be implemented to increase high quality hatchling production. Graphical abstract

Linking local people's perception of wildlife and conservation to livelihood and poaching alleviation: A case study of the Dja biosphere reserve, Cameroon Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Manfred Aimé Epanda, André Junior Mukam Fotsing, Thomas Bacha, Daniel Frynta, Luc Lens, Isaac Roger Tchouamo, Dupain Jef Abstract This Paper examines how people's livelihoods and perceptions of wildlife are related to self-reported poaching (here defined as commercial bushmeat hunting) in 25 villages at the northern buffer zone of the Dja Biosphere Reserve, East Cameroon. Using a six-point Likert scale questionnaire among 263 households interviewed form March to June 2017, the following hypothesis were tested: (1) Households with positive perceptions of wildlife are less involved in poaching; (2) Positive perceptions of wildlife are linked to sustainable livelihood improvement of households; and (3) Sustainable livelihood improvement of households leads to poaching alleviation. The study area has been the site since 2010 for a community-centered conservation Program that aims to improve local people's livelihoods (through the creation of income sources based on cocoa-based agroforestry and Non Timber Forest Products (NTFPs) Valorization) and their perceptions of wildlife (mainly through awareness raising and wildlife education) and therefore divert them from poaching. The main findings of the study indicates that positive perceptions of wildlife are linked to lower levels of poaching. Similarly, positive perception of wildlife was positively related to Livelihood improvement of the respondents. However, livelihood improvement alone did not predict poaching alleviation though we reported a significant difference in poaching frequencies of cocoa and non-cocoa producers with the firsts less involved in poaching. The findings of this study recommend more holistic approaches of biodiversity conservation that integrate simultaneously perception and livelihood improvement.

Snake diversity in floodplains of central South America: Is flood pulse the principal driver? Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Liliana Piatti, Dan F. Rosauer, Cristiano de C. Nogueira, Christine Strussmann, Vanda Lúcia Ferreira, Marcio Martins Abstract Seasonal flood pulses drive important seasonal ecosystem changes, trigger ecological processes that control spatial and temporal distribution of organisms and their life-history strategies, and are considered a key ecological process shaping diversity in floodplains. We used generalized dissimilarity modelling (GDM) to analyse the relative importance of flooding as a driver of snake community composition in the Paraguay River Basin (PRB), which encompasses discontinuous seasonal flooded areas, including the Pantanal floodplain, one of the largest Neotropical wetland systems. We modelled the beta diversity of pairs of PRB snake communities (based on species occurrence and phylogenetic relationships) as a function of biogeographical and environmental dissimilarities between areas, considering predictors that represent distinct limitations of species’ ability to use an area. Annual flooding directly drives snake diversity, mainly when ancient evolutionary relationships between species were considered to calculate the phylogenetic diversity of the communities. Floods recurrently produce major changes in the environment and probably limit the persistency of species extremely specialized in habitat use. Despite the confirmation of the effect of flooding, the most important predictor of beta diversity between snake communities in the PRB was forest cover where communities were placed. Forest cover seems to constrain the occurrence of some species in both gradient extremities through the absence of suitable conditions for either specialized habitat use or thermoregulatory behaviours. Geographical distance was also an important predictor of beta diversity, highlighting the importance of neutral process in the assembly of local communities in systems such as seasonally flooded areas, where annual disturbances of varying intensities continually disassemble and reassemble biological communities. For the first time, we quantified the relative importance of flooding affecting patterns of biological communities in the Pantanal floodplain, compared to multiple factors also acting on species turnover in the area.

Prey abundance drives habitat occupancy by jaguars in Amazonian floodplain river islands Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Rafael M. Rabelo, Susan Aragón, Júlio César Bicca-Marques Abstract The jaguar (Panthera onca) is widely distributed across a broad range of habitat types, where its feeding habits and habitat use patterns vary significantly. The jaguar and its main arboreal prey – the brown-throated sloth (Bradypus variegatus) and the red howler monkey (Alouatta juara) – are widespread in the Amazonian floodplain forests of the Mamirauá Reserve. These forest-dwelling species are the most common mammal species both in the continuous forest and the forest patches surrounded by a river matrix – the fluvial islands – of the Solimões and Japurá rivers. We used sign surveys along line-transects to assess the pattern of habitat occupancy by jaguars in Amazonian floodplain forests. Specifically, we (i) tested whether habitat occupancy by jaguars differs between river islands and continuous forest; and (ii) evaluated whether and how the local abundance of sloths and howler monkeys influence the probability of site occupancy by jaguars. We built an occupancy model and used Bayesian inference to reach these goals. The proportion of sites estimated to be used by jaguars was ψ = 0.75 (HPD95: 0.36–1.00), and it did not differ between islands and continuous forest. The abundance of both prey species had a direct influence on jaguar's habitat use, whereas the aquatic matrix seems to have a negligible effect on the use of islands by jaguars. We conclude that the isolation of the river islands within the aquatic matrix does not hamper jaguars to use them. We also conclude that prey search modulates jaguars' habitat occupancy patterns with both prey species having a similar effect. This finding is compatible with the previously reported importance of sloths to the diet of jaguars in the study region despite its lower abundance than howlers. Finally, we suggest that sign surveys are an alternative method to assess the pattern of jaguar habitat occupancy in floodplain forests.

Environmental adaptation and ecological distribution of streamside annual plants in northern Japan Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Mayuko Suzuki, Takashi Nakamura, Takeshi Shindo, Masahito T. Kimura Abstract Environmental adaptation and distribution of three annual plants, Impatiens noli-tangere, I. textori and Persicaria thunbergii, occurring in streamside environments were studied in Sapporo, northern Japan. Impatiens noli-tangere was found along steep streams as well as gentle streams, whereas I. textori and P. thunbergii were less frequent along steep streams than along gentle streams. Impatiens noli-tangere was the least tolerant or resistant to environmental disturbances such as submergence, rapid water current, herbivory and possibly shading. P. thunbergii was the most tolerant or resistant, and I. textori showed an intermediate response. On the other hand, I. noli-tangere started reproduction earliest, followed by I. textori and P. thunbergii. Earlier start of reproduction of I. noli-tangere is assumed to serve as a means to reduce risks to encounter catastrophic events before reproduction. In addition, I. noli-tangere was the tallest per stem dry-weight unit. Growing taller would be an adaptation to reduce risk of shading. It is assumed that earlier reproduction enables I. noli-tangere to leave offspring along steep streams where water current after heavy rain is more rapid and catastrophic.

Quad bike impacts on vegetation and soil physicochemical properties in an arid ecosystem Publication date: May 2019 Source: Acta Oecologica, Volume 97 Author(s): Ana L. Navas Romero, Mario A. Herrera Moratta, Antonio D. Dalmasso, Agustina Barros Abstract The increase use of Off-Road Vehicles (ORVs) coupled with the absence of control strategies have led to extensive use of natural areas for the creation of recreational trails. We assessed the effects of quad bikes on vegetation and soils in an arid ecosystem subjected to intensive quad bike use. We selected randomly eight traffic sites (disturbed sites) and eight adjacent control sites (undisturbed sites). Plant cover and composition were assessed with the point-intercept method and phytosociological census. In each site, we collected soil samples to assess soil physicochemical properties, including apparent specific weight (ASG), actual specific weight (RSG), porosity, texture, electric conductivity (EC) and pH. Soil compaction was measured at 30 spaces points per site. Plant cover and richness was significant lower in disturbed sites, with only four species present in areas subjected to disturbance. There were also changes in species dominance, with native perennial shrubs and grasses characterizing the undisturbed sites while the disturbed sites were mainly dominated by the invasive exotic herb Salsola kali. ORVs traffic also affected soil physicochemical properties including soil compaction, ASG, EC and soil pH. Soil compaction was more than double in disturbed sites and ASG tended to be higher under this condition. The EC was significantly higher and soil pH was significantly lower in the disturbed sites. Reduced vegetation cover and changes to soils physicochemical properties on quadbike trails highlights the impacts of ORVs in the landscape and the need to develop management strategies to minimize disturbance from ORVs on vegetation and soils.