Taxonomic and Functional Diversity of Heterotrophic Protists (Cercozoa and Endomyxa) from Biological Soil Crusts

Biological soil crusts (biocrusts) accommodate diverse communities of phototrophic and heterotrophic microorganisms. Heterotrophic protists have critical roles in the microbial food webs of soils, with Cercozoa and Endomyxa often being dominant groups. Still, the diversity, community composition, and functions of Cercozoa and Endomyxa in biocrusts have been little explored. In this study, using a high-throughput sequencing method with taxon-specific barcoded primers, we studied cercozoan and endomyxan communities in biocrusts from two unique habitats (subarctic grassland and temperate dunes). The communities differed strongly, with the grassland and dunes being dominated by Sarcomonadea (69%) and Thecofilosea (43%), respectively. Endomyxa and Phytomyxea were the minor components in dunes. Sandonidae, Allapsidae, and Rhogostomidae were the most abundant taxa in both habitats. In terms of functionality, up to 69% of the grassland community was constituted by bacterivorous Cercozoa. In contrast, cercozoan and endomyxan communities in dunes consisted of 31% bacterivores, 25% omnivores, and 20% eukaryvores. Facultative and obligate eukaryvores mostly belonged to the families Rhogostomidae, Fiscullidae, Euglyphidae, Leptophryidae, and Cercomonadidae, most of which are known to feed mainly on algae. Biocrust edaphic parameters such as pH, total organic carbon, nitrogen, and phosphorus did not have any significant influence on shaping cercozoan communities within each habitat, which confirms previous results from dunes.

Heterogeneity of fern communities in riparian forest remnants from the South Brazilian Campos (Pampa)

Riparian forests present biotic and abiotic factors that influence environmental dissimilarity, which reflect specific fern distribution. The purpose of this this study was to evaluate the environmental heterogeneity associated to the terrestrial fern communities in riparian forest remnants in the grasslands southern half of Rio Grande do Sul state . We sampled ten 5×5 m plots in each site (AI, AII and AIII), totaling 30 plots. In each plot, fern species were inventoried and vegetative, microclimatic and edaphic parameters were collected. A total of 24 species were surveyed in the three riparian forest remnants, distributed in 19 genera and 10 families. The Principal Components Analysis (PCA) showed that plots of AI had the highest temperature and aluminum values, while humidity was the lowest, which was reflected in the decrease of ferns richness. Soil moisture and air humidity were variables more related to the plots of AII and AII, indicating that these plants were favored in these environments. The floristic identity characteristic of each site suggests that many species are dependent to certain local environmental conditions. In this sense, even in very geographically close sites, riparian remnants deserve conservation attention, since they are capable of harboring high diversity in this grassland phytophysiognomy in southern Brazil. The results of this integrated study, with vegetation, climatic, and edaphic parameters, suggest, as expected, that ferns categorically respond to the heterogeneity shown by riparian environments, even when fragments are geographically very close to each other.

Floristic Distribution According to the Edaphic Parameters of a Steppe Zone, Case of Study: The Nature Reserve “El-Mergueb” M’sila, Algeria

The natural site of El-Mergueb, is one of the specific steppe ecosystem, that occupies an area of 16,481 ha; it is among the particular ecosystems in Algeria and is unique in northern Africa. It is located in the geographical limit of the Tell Atlas and the Saharan Atlas. It is at an altitude of 550 to 800 m, with a typically arid climate. The faunistic and floristic richness, quite specifically, contains species protected and classified in the IUCN: Chlamydotis and Gazella, as well as an autochthonous plant diversity: Stipa, Pistacia and Ziziphus. This study is based on the analysis of the vegetation by characterizing the associated soil type through the monitoring of the Eco-pedological relation during two seasons in three years: 2015−2016−2017. Nine soil profiles with a collection of twenty-one samples for each station of experimentation were collected. The results thus obtained showed that the content of the parameters analyzed is between low and average of the three stations. The average of the floristic analysis of the study area made it possible to define 34 botanical families spread over 69 botanical genus and 275 species. The analysis and the description of a natural space is important to establish a typology which is that is the basis for the development of management plans to conserve this category of protected areas. The FAC (Factorial Analysis of Correspondence) is relative to the individualization and the typology for three sequences, which corresponds to the groups (A), (B) and (C) also for the places in arid climate variants with very cold winters.

Invasion of the tropical earthwormPontoscolex corethrurus(Rhinodrilidae, Oligochaeta) in temperate grasslands

The tropical earthwormPontoscolex corethrurus(Rhinodrilidae, Oligochaeta) presents a broad distribution (e.g., 56 countries from four continents). It is generally assumed that temperature appears to limit the success of tropical exotic species in temperate climates. However, the distribution range of this species could advance towards higher elevations (with lower temperatures) where no tropical species currently occur. The aim of this study was to evaluate the soil and climatic variables that could be closely associated with the distribution ofP. corethrurusin four sites along an altitudinal gradient in central Veracruz, Mexico. We predicted that the distribution ofP. corethruruswould be more related to climate variables than edaphic parameters. Five sampling points (in the grassland) were established at each of four sites along an altitudinal gradient: Laguna Verde (LV), La Concepción (LC), Naolinco (NA) and Acatlán (AC) at 11–55, 992–1,025, 1,550–1,619 y 1,772–1,800 masl, respectively. The climate ranged from tropical to temperate along the altitudinal gradient. Ten earthworm species (5 Neotropical, 4 Palearctic and 1 Nearctic) were found along the gradient, belonging to three families (Rhinodrilidae, Megascolecide and Lumbricidae). Soil properties showed a significant association (positive for Ngrass, pH, permanent wilting point, organic matter and P; and negative for Total N, K and water-holding capacity) with the abundance of the earthworm community. Also there seems to be a relationship between climate and earthworm distribution along the altitudinal gradient.P. corethruruswas recorded at tropical (LV and LC) and temperate sites (NA) along the altitudinal gradient. Our results reveal that soil fertility determines the abundance of earthworms and site (climate) can act as a barrier to their migration. Further research is needed to determine the genetic structure and lineages ofP. corethrurusalong altitudinal gradients.

Дискримінантний аналіз агроекологічного впливу способів механічного обробітку ґрунту

У статті представлено результати дискримінантного аналізу за едафічними показниками станів ґрунтової системи, які формуються внаслідок різних способів механічного обробітку. Показано, що для дискримінації чизелювання, безполицевого та мінімального обробітку, а також «нульового обробітку» достатньо дві канонічні дискримінантні осі. Канонічна функція 1 дискримінує способи механічного обробітку з високою глибиною оранки та способи з малою глибиною та нульовим обробітком. Канонічна функція 2 дискримінує кожну з перших груп на підгрупи з меншою глибиною оранки у парі. Більш глибокі варіанти оранки відрізняються більшими рівнями поживних речовин (азот, фосфор, калій). Значення канонічних змінних розглядаються як маркери осей простору, в межах якого відбивається мінливість едафічних показників. The article presents the results of discriminant analysis on the state of soil on edaphic parameters of the system, which are formed as a result of different methods of machining. Two initial discriminant axes is enough for discrimination of results of chisel cultivation, subsurface cultivation, minimum tillage, and also «no till». Canonical axes 1 discriminates ways of machining with high depth of ploughing and ways with small depth or zero processing. Canonical axes 2 discriminates each of the first groups on subgroups with smaller depth of ploughing in each pair. Deeper variants of a ploughed land differ by the big levels of nutrients (nitrogen, phosphorus, potassium) in soil. Values of canonical variables are considered as markers of axes of space in which limits variability of edaphic indicators is reflected.

Rare Taxa Maintain Microbial Diversity and Contribute to Terrestrial Community Dynamics throughout Bark Beetle Infestation

ABSTRACTA global phenomenon of increasing bark beetle-induced tree mortality has heightened concerns regarding ecosystem response and biogeochemical implications. Here, we explore microbial dynamics under lodgepole pines through the analysis of bulk (16S rRNA gene) and potentially active (16S rRNA) communities to understand the terrestrial ecosystem responses that are associated with this form of large-scale tree mortality. We found that the relative abundances of bulk and potentially active taxa were correlated across taxonomic levels, but at lower levels, cladal differences became more apparent. Despite this correlation, there was a strong differentiation of community composition between bulk and potentially active taxa, with further clustering associated with the stages of tree mortality. Surprisingly, community clustering as a function of tree phase had limited correlation to soil water content and total nitrogen concentrations, which were the only two measured edaphic parameters to differ in association with tree phase. Bacterial clustering is more readily explained by the observed decrease in the abundance of active, rare microorganisms after tree death in conjunction with stable alpha diversity measurements. This enables the rare fraction of the terrestrial microbial community to maintain metabolic diversity by transitioning between metabolically active and dormant states during this ecosystem disturbance and contributes disproportionately to community dynamics and archived metabolic capabilities. These results suggest that analyzing bulk and potentially active communities after beetle infestation may be a more sensitive indicator of disruption than measuring local edaphic parameters.IMPORTANCEForests around the world are experiencing unprecedented mortality due to insect infestations that are fueled in part by a changing climate. While aboveground processes have been explored, changes at the terrestrial interface that are relevant to microbial biogeochemical cycling remain largely unknown. In this study, we investigated the changing bulk and potentially active microbial communities beneath healthy and beetle-killed trees. We found that, even though few edaphic parameters were altered from beetle infestation, the rare microbes were more likely to be active and fluctuate between dormancy and metabolic activity. This indicates that rare as opposed to abundant taxa contribute disproportionately to microbial community dynamics and presumably biogeochemical cycling within these types of perturbed ecosystems.