查看更多>>摘要：Since epiphytes mainly obtain water and nutrients from surrounding air, they are extremely sensitive to environmental changes, making them reliable bio-indicators for monitoring climate change. Hemiepiphytes are one common form of epiphytic plants, consisting of primary and secondary hemiepiphytes. It is thus reasonable to suppose that the hemiepiphytes should respond strongly to an extreme change in local climatic conditions. Based on survey data of hemiepiphytes (all the investigated species are primary hemiepiphytes) on trees before (2014) and after (2018) a heavy snowfall event (2015, depth of 50 cm), we examined differences in the distribution and abundance of individuals, population structure, and the general network structure of hemiepiphyte-host associations in a subtropical forest in the Ailao Mountains (Yunnan Province, in southwest China). Contrary to our hypothesis, the results revealed no significant changes for the distribution and abundance of this hemiepiphyte community before and after the heavy-snowfall event. The population structure of all hemiepiphytes (pooled) shifted from a dynamic to a stable state, but did not change on a per species basis. According to the constructed network's parameters, no significant differences were found between years, except for changed web asymmetry, linkage density, and interaction evenness. Our results suggest hemiepiphytes are highly resilient to extreme weather perturbations: within just four years after the snowfall, the community was nearly fully restored to its prior composition and structure. We propose this resilience capability is linked to their ecophysiological characteristics and distributions on host trees.
Mekahlia, Mohamed NacerAbidi, HarounSlimane, FerielSadine, Salah Eddine...
11页
查看更多>>摘要：Scorpion fauna of Algeria is insufficiently known. This study was carried out to assess seasonal changes of the scorpion biodiversity at the region of Tebessa (northeastern Algeria) along a climatic gradient including semiarid, arid and desertic climates randomized sampling was carried out at three sites stratified according to a climatic gradient. Sites visits were carried out 16 times per year at each site for a period of 2 h for each field trip. The distribution of the scorpions was studied by ecological descriptors and by statistical analyzes. In this study, 257 scorpion specimens belonging to the families Buthidae (64%) and Scorpionidae (36%) were collected. The Buthidae family was represented by four species: Buthus tunetanus (Herbst, 1800) (26%), Buthus aures Lourenco, 2016 (21%), Androctonus australis Ewing, 1928 (14%) and Androctonus aeneas (Koch, 1839) (3%), while the Scorpionidae was represented by a single species, Scorpio punicus Fet, 2000, which was also the most abundant at 36%. Statistical models revealed that climatic gradient and seasonal variation significantly influenced the distribution and the biodiversity of scorpions and that ecological descriptors were strongly correlated with climatic gradient and seasonal variation. This work constitutes the first study carried out on the scorpion diversity in northeastern Algeria. Thus, planning of control programs for the species identified in this area is essential.
查看更多>>摘要：Moss-associated nitrogen (N-2) fixation performed by epiphytic, N-2-fixing bacteria (diazotrophs) contributes significantly to ecosystem N input in pristine habitats. While we have some understanding of the effects of climate warming on moss-associated N-2 fixation, we lack data on effects of freeze-thaw cycles (FTCs) on diazotroph activity, although increased frequency of FTCs is predicted. We collected the widespread moss Pleurozium schreberi along a climate gradient (temperate, boreal, arctic) and exposed moss and associated diazotmphs to severe (20 degrees C difference, cycling between +10 and -10 degrees C) and mild (6 degrees C difference, +/- 3 degrees C) diurnal FTCs. We measured N-2 fixation in mosses over 8 weeks and assessed their nutrient loss (fixed N-2, total dissolved N, ammonium, phosphate) during the FTCs. We expected lower nitrogenase activity in mosses exposed to more severe FTCs and different sensitivities of N-2 fixation towards FTCs along the climate gradient. However, no differences were found in N-2 fixation between mild and severe FTCs, but N-2 fixation in mosses from the temperate heath was less susceptible to FTCs than those from colder sites, suggesting adapted temperate diazotroph communities. Mosses lost little N, most at constant, positive temperatures, while more phosphate was lost from mosses exposed to FTCs, depending on the positioning along the climate gradient, mirroring nutrient demand and limitation. Our results show that moss-associated N-2 fixation is less susceptible towards FTCs than expected but nutrient loss from moss carpets can increase following FTCs, with consequences for nutrient pools and fluxes.
查看更多>>摘要：Coppicing is a common management strategy in oak woodlands; however, our knowledge is limited in the impacts of coppicing on spatial structure and growth dynamics of oak stands. In this study, we compared the spatial patterns of two adjacent high and coppice pure stands of Brant's oak (Quercus brantii Lindl.) in central part of Zagros semi-arid woodlands, western Iran. We used univariate form of scale-dependent summary statistics (nearest neighbour distribution function, L-function, pair- and mark correlation functions) and Analytical Global Envelopes under inhomogeneous Poisson process which allow detection of the intraspecific interactions of the individuals within the high and coppice stands. Our results indicated the aggregation of oak individuals at small spatial scales (i.e., 0-3 m) in the high stand, most likely as a result of aggregation in parts with environmentally benign conditions. The positive interactions of conspecifics had a marked effect on their size (e.g., larger height (5%), DBH (24%), and crown area (50%) than mean size at spatial scale of 2 m) inferred as growth stimulation and aggregation of young trees around their nurse or parent trees. However, the findings revealed the segregation of oak trees at short distances in the coppice stand (i.e., 0-5 m), probably due to strong competition of conspecific neighbors. The negative size correlation of oaks (e.g., smaller height, DRC, and crown area of oak individuals (15%) than mean size at distance of 2 m) was considered as the outcome of competition for scarce resources in the woodlands with unfavourable conditions. In general, it was concluded that the aggregated spatial structure of the high stand has changed to segregation of individuals within the coppice stand. Additionally, we found that environmental heterogeneity and intraspecific competition are the main drivers of the high and coppice stands, respectively.
查看更多>>摘要：Although millipedes are faunistically among the best studied groups of edaphon in Europe, there is still a lack of available information on the ecological requirements of particular species. Habitat preferences that determine the distribution of species are largely controlled by soil properties, habitat structure and microclimate. In forests, habitat features are predominantly driven by the properties of woody tree species. Millipedes, like other saprophages, are influenced by the characteristics of litter and soil. However, the effect of tree species on millipede communities has not been investigated in forest stands consisting of several autochthonous or allochthonous tree species. Our study examines the effect of soil properties related to several autochthonous and allochthonous tree species on millipede communities. The research was carried out at 9 stands in the Arboretum Mly.nany (western Slovakia). Each stand represents a monoculture of one of 9 tree species: 4 autochthonous species (Picea abies, Taxus baccata, Quercus cerris, and Carpinus betulus) and 5 allochthonous species (Picea orientalis, Pinus nigra, Pinus ponderosa, Thuja occidentalis, and Castanea sativa). The results of this research confirmed relationships between (1) the soil pH and the total activity-density of millipedes, (2) the soil pH and the structure of the millipede communities, (3) the soil conductivity and the structure of the millipede communities, and (4) the leaf litter pH and the equitability of the millipede communities. In terms of the total activity-density and species richness of the millipedes, forest stands with autochthonous tree species provided more favourable conditions for millipedes than forest stands with allochthonous tree species. Millipedes achieved high abundance and diversity in these stands and can therefore contribute to the faster decomposition of dead organic matter and nutrient recycling in forest ecosystems.
NSTL
Elsevier