Response of soil invertebrates to disturbance across three resource regions in North Carolina

Effects of Species Invasion and Inundation on the Collembola Community in Coastal Mudflat Wetland from the Perspective of Functional Traits

The group of soil arthropods known as Collembola is characterized by its abundance and sensitivity to environmental changes. They are ideal an species for soil indicators. In order to clarify the effects of species invasion and inundation on the Collembola community in coastal mudflat wetlands, the correlation between the collembolan functional traits and environmental factors was studied in Shanghai Jiuduansha Wetland National Nature Reserve for the first time. Five sample plots, including three vegetations-Spartina alterniflora (an invasive species), Phragmites australis, and Zizania latifolia-were set up following the differences in vegetation types and between high and low tidal flats. Data on the diversity of the Collembolan species and their functional traits were collected and combined with the soil physicochemical properties and vegetation environment factors in different tidal flats. The key findings and conclusions of the study are as follows: a total of 18 species, four families, and three orders make up the obtained Collembola, two species of Proisotoma are dominant species that account for 49.59% and 24.91% of the total, respectively. The maintenance of the species diversity of Collembola is disturbed by the higher conversion efficiency of Spartina alterniflora rather than Phragmites australis with lower organic carbon (C) content and higher total nitrogen (N) content. The primary environmental variables influencing species distribution were the C/N ratio, total N, and bulk soil density. The bulk density of the soil impacts the movement and dispersal of the functional traits. The depth of the soil layer is related to the functional traits of the sensory ability. The analysis of the functional traits and environment is fairly helpful in exploring how species respond to their environment and offers a better explanation for the habitat selection of Collembola.

Ecological and morphological differentiation among COI haplotype groups in the plant parasitic nematode species Mesocriconema xenoplax

DNA barcoding with the mitochondrial COI gene reveals distinct haplotype subgroups within the monophyletic and parthenogenetic nematode species, Mesocriconema xenoplax. Biological attributes of these haplotype groups (HG) have not been explored. An analysis of M. xenoplax from 40 North American sites representing both native plant communities and agroecosystems was conducted to identify possible subgroup associations with ecological, physiological, or geographic factors. A dataset of 132 M. xenoplax specimens was used to generate sequences of a 712 bp region of the cytochrome oxidase subunit I gene. Maximum-likelihood and Bayesian phylogenies recognized seven COI HG (≥99/0.99 posterior probability/bootstrap value). Species delimitation metrics largely supported the genetic integrity of the HG. Discriminant function analysis of HG morphological traits identified stylet length, total body length, and stylet knob width as the strongest distinguishing features among the seven groups, with stylet length as the strongest single distinguishing morphological feature. Multivariate analysis identified land cover, ecoregion, and maximum temperature as predictors of 53.6% of the total variation (P = 0.001). Within land cover, HG categorized under “herbaceous,” “woody wetlands,” and “deciduous forest” were distinct in DAPC and RDA analyses and were significantly different (analysis of molecular variance P = 0.001). These results provide empirical evidence for molecular, morphological, and ecological differentiation associated with HG within the monophyletic clade that represents the species Mesocriconema xenoplax.

The role of urban forest patches in maintaining isopod diversity (Oniscidea)

Compositional changes in natural communities associated with anthropogenic influence often lead to localised extinctions and biodiversity loss. Soil invertebrates are also threatened by urbanisation due to habitat fragmentation, vegetation changes and management, soil alteration, degradation, and disappearing shelter sites. The aim was to assess terrestrial isopod (Oniscidea) assemblages in differently degraded urban forest patches of a metropolitan area (Budapest, Hungary). Study sites were compared by their species richness, composition and the relevant background factors (soil properties, dead wood, litter characteristics, and canopy closure). The degree of urban disturbance was expressed using an urbanisation index (UI) based on built-up density and vegetation cover. The isopods were identified to species level, and were qualified by their habitat preference and naturalness index (TINI). Average Rarity Index (ARI), derived from TINIs provided information on the degree of naturalness/disturbance of each habitat. Altogether 14 isopod species were collected from 23 sample sites. Urbanisation indirectly affected on the composition of isopod assemblages through the quantity of dead wood and soil plasticity. ARIs and UIs of sample sites were negatively correlated. Urban patches harboured habitat generalist, synanthropic and established introduced species with low naturalness value of assemblages. Areas with no or low anthropogenic disturbance maintained stable native, autochthonous assemblages that were characteristic of rural sites in the region. Transitional zones between rural and urban habitats usually maintained a mixed isopod fauna consisting of both urban and rural elements.

Effects of set-aside management on certain elements of soil biota and early stage organic matter decomposition in a High Nature Value Area, Hungary

Agricultural intensification is one of the greatest threats to soil biota and function. In contrast, set-aside still remains a management practice in certain agri-environmental schemes. In Hungary, the establishment of sown set-aside fields is a requirement of agri-environmental schemes in High Nature Value Areas. We tested the effects of set-aside management on soil biota (bacteria, microarthropods, woodlice and millipedes), soil properties and organic matter decomposition after an initial establishment period of two years. Cereal – set-aside field pairs, semi-natural grasslands and cereal fields were sampled in the Heves Plain High Nature Value Area in Eastern Hungary, in May 2014. Topsoil samples were taken from each site for physical, chemical, microbial analyses and for extraction of soil microarthropods. Macrodecomposers were sampled by pitfall traps for two weeks. The biological quality of soil was estimated by the integrated QBS index (‘‘Qualità Biologica del Suolo’’, meaning ‘‘Biological Quality of Soil’’) based on diversity of soil microarthropods. To follow early stage organic matter decomposition, we used tea bags filled with a site-independent, universal plant material (Aspalathuslinearis, average mass 1.26 ± 0.03 g). Tea bags were retrieved after 1 month to estimate the rate of mass loss. We found significant differences between habitat types regarding several soil physical and chemical parameters (soil pH, K and Na content). The study showed positive effects of set-aside management on soil biodiversity, especially for microarthropods and isopods. However, we did not experience similar trends in relation to soil bacteria and millipedes. There was higher intensity of organic matter decomposition in soils of set-aside fields and semi-natural grasslands (remaining mass on average: 74.17% and 76.6%, respectively) compared to cereal fields (average remaining mass: 81.3%). Out of the biotic components, only the biological quality of soil significantly influenced (even if marginally) plant tissue decomposition. Our results highlight the importance of set-aside fields as shelter habitats for soil biota, especially for arthropods. Set-aside fields that are out of a crop rotation for 2 years could be a valuable option for maintaining soil biodiversity, as these fields may simultaneously conserve elements of above- and below-ground diversity.

Soil microbial characteristics at the monitoring plots on windthrow areas of the Tatra National Park (Slovakia): their assessment as environmental indicators

This study focused on the responses of soil microorganisms to different management regimes on disturbed windthrow areas. Microbial parameters potentially serving as indicators of environmental changes within a long-term monitoring of forest development after large-scale disturbance events were assessed. Basal and substrate-induced respiration, N mineralisation, catalase activity, microbial biomass as well as functional diversity based on Biolog assay were determined in soil samples from three disturbed plots and an undisturbed reference plot in the Tatra National Park (Slovakia) since 2006. A relative congruence of inter-annual trends of microbial activity indicators at all plots results from a common response of microbiota to changes of climate at the landscape level after forest stands were destroyed. While catalase activity and functional diversity proved to be useful indicators of temporal trends, microbial biomass seems to reflect different management regimes at the disturbed plots.