Timing outweighs magnitude of rainfall in shaping population dynamics of a small mammal species in steppe grassland

Climate change–induced shifts in species phenology differ widely across trophic levels, which may lead to consumer–resource mismatches with cascading population and ecosystem consequences. Here, we examined the effects of different rainfall patterns (i.e., timing and amount) on the phenological asynchrony of population of a generalist herbivore and their food sources in semiarid steppe grassland in Inner Mongolia. We conducted a 10-y (2010 to 2019) rainfall manipulation experiment in 12 0.48-ha field enclosures and found that moderate rainfall increases during the early rather than late growing season advanced the timing of peak reproduction and drove marked increases in population size through increasing the biomass of preferred plant species. By contrast, greatly increased rainfall produced no further increases in vole population growth due to the potential negative effect of the flooding of burrows. The increases in vole population size were more coupled with increased reproduction of overwintered voles and increased body mass of young-of-year than with better survival. Our results provide experimental evidence for the fitness consequences of phenological mismatches at the population level and highlight the importance of rainfall timing on the population dynamics of small herbivores in the steppe grassland environment.

Grazing intensity rather than host plant’s palatability shape the community of arbuscular mycorrhizal fungi in a steppe grassland

Arbuscular mycorrhizal fungi (AMF) are the predominant type of mycorrhizal fungi in roots and rhizosphere soil of grass species worldwide. Grasslands are currently experiencing increasing grazing pressure, but it is not yet clear how grazing intensity and host plant grazing preference by large herbivores interact with soil- and root-associated AMF communities. Here, we tested whether the diversity and community composition of AMF in the roots and rhizosphere soil of two dominant perennial grasses grazed differently by livestock change in response to grazing intensity. We conducted a study in a long-term field experiment in which seven levels of field-manipulated grazing intensities were maintained for 13 years in a typical steppe grassland in northern China. We extracted DNA from the roots and rhizosphere soil of two dominant grasses, Leymus chinense (Trin.) Tzvel. and Stipa grandis P. Smirn, with contrasting grazing preference by sheep. AMF DNA from root and soil samples were then subjected to molecular analysis. Our results showed that AMF α-diversity (richness) at the virtual taxa (VT) level varied as a function of grazing intensity. Different VTs showed completely different responses along the gradient, one increasing, one decreasing and others showing no response. Glomeraceae was the most abundant AMF family along the grazing gradient, which fits well with the theory of disturbance tolerance of this group. In addition, sheep grazing preference for host plants did not explain a considerable variation in AMF α-diversity. However, the two grass species exhibited different community composition in their roots and rhizosphere soils. Roots exhibited a lower α-diversity and higher β-diversity within the AMF community than soils. Overall, our results suggest that long-term grazing intensity might have changed the abundance of functionally-diverse AMF taxa in favor of those with disturbance-tolerant traits. We suggest our results would be useful in informing the choice of mycorrhizal fungi indicator variables when assessing the impacts of grassland management choices on grassland ecosystem functioning.

Timing outweighs amount of rainfall in shaping population dynamics

Climate variability has been widely documented to have bottom-up effects on the population dynamics of animals1,2, but the mechanisms underlying these effects have been rarely investigated through field manipulative experiments that control for confounding factors3. Here, we examined the effects of different rainfall patterns (i.e. timing and amount) on the population size of Brandt’s voles Lasiopodomys brandtii in semi-arid steppe grassland in Inner-Mongolia by conducting a 10-year (2010-2019) rainfall manipulation experiment in twelve 0.48 ha field enclosures. We found that moderate rainfall increase during the early rather than late growing season drove marked increases in population size through increasing the biomass of preferred plant species, whereas heavily increased rainfall produced no further increase in vole population growth. The increase in vole population size was more coupled with increased reproduction of overwintered voles and increased body mass of young-of-year than with better survival. Our results provide the first experimental evidence for the bottom-up effects of changing rainfall on the population growth of small mammals, and highlight the importance of rainfall timing on the population dynamics of wildlife in the steppe grassland environment.

Description of the second instar larva of Thermothrips mohelensis Pelikán (Thysanoptera: Thripidae)

Thermothrips mohelensis Pelikán is an extremely rare thrips found in dry steppe grassland ecosystems (Pelikán 1949, 1995; Ulitzka 2019a). It has been reported from only a few locations and almost always in very low abundance: one female each has been collected in Germany (Ulitzka 2019a), Slovenia (Kucharczyk 2008) and Turkey (Tunç 1992), two females are known from Iran (Mirab-balou & Chen 2013), three from Poland (Zawirska 1988; Kucharczyk 2007) and six from Western Russia (Schliephake 1977). Larger series including males and larvae are known only from Czechoslovakia (Pelikán 1949, 1995) and from Yakutia, East Siberia where—besides other specimens—the larvae discussed below have been collected (see Evdokarova & Kucharczyk 2020). The fragmented and selective occurrence of this species in steppe habitats has been interpreted to represent scattered relict populations that may have remained from a more extensive distribution far back, possibly in the wide dry grasslands of the Late Pleistocene (Ulitzka 2019a). Similar to other specialist species of those barren habitats T. mohelensis is severely threatened by the general decline of these fragile ecosystems due to natural succession or anthropogenic impact (Kucharczyk 2008; Kucharczyk & Kucharcyk 2008; Ulitzka 2019a). T. mohelensis is a thermophilous (zur Strassen 2003) and highly xerophilous species. This thrips was erroneously considered an hydrophilous wetland thrips (Bhatti 1998) due to a mistranslation (see Ulitzka 2019a). T. mohelensis lives and breeds monophagously in flowers of Galium (Rubiaceae), particularly G. verum but also G. mollugo (Pelikán 1949, 1995; Schliephake 1972; Tunç 1992).

Patterns in steppe grassland vegetation of Troitsky State Natural Complex Preserve

The patterns (mosaicity) in the northern type of Southern Ural steppe vegetation were characterized by a hierarchical continuum concept theory for Troitsky State Natural Complex Preserve example. Multispecies patterns have been identified by blocks and principal components methods while a hierarchical patterns evaluation by multivariate statistics (Cluster, Discriminant Analysis and Non-Metric Multidimensional Scaling) and biotopes phytoindication. It has been established that three pattern levels micro-patterns (0,8 and 1,8 m), parcels (6,0 m) and coenotics (11,0 m) are significantly identified in steppe vegetation. The two last levels correspond to levels specified for the southern type of Southern Ural steppe vegetation earlier. The authors have demonstrated that parcel and coenotic patterns are identified as ratio of four species abundance: Stipa lessingiana, S. pennata, S. tirsa and Festuca valesiaca. For natural and undisturbed steppe associations informative species are non-dominants or edificators. Vegetation plot size and the location in phytocatena can be determinative for floristic composition, phytodiversity indexes and syntaxon detection. There are several non-uniformly scaled factors of mosaicity identification. The most significant ones are coenotic interactions among species. Soil nitrogen regime and soil calcium regimes, soil moistening, aeration and acidity are significant for abiotic factors.

Habitat filtering shapes the differential structure of microbial communities in the Xilingol grassland

The spatial variability of microorganisms in grasslands can provide important insights regarding the biogeographic patterns of microbial communities. However, information regarding the degree of overlap and partitions of microbial communities across different habitats in grasslands is limited. This study investigated the microbial communities in three distinct habitats from Xilingol steppe grassland, i.e. animal excrement, phyllosphere, and soil samples, by Illumina MiSeq sequencing. All microbial community structures, i.e. for bacteria, archaea, and fungi, were significantly distinguished according to habitat. A high number of unique microorganisms but few coexisting microorganisms were detected, suggesting that the structure of microbial communities was mainly regulated by species selection and niche differentiation. However, the sequences of those limited coexisting microorganisms among the three different habitats accounted for over 60% of the total sequences, indicating their ability to adapt to variable environments. In addition, the biotic interactions among microorganisms based on a co-occurrence network analysis highlighted the importance of Microvirga, Blastococcus, RB41, Nitrospira, and four norank members of bacteria in connecting the different microbiomes. Collectively, the microbial communities in the Xilingol steppe grassland presented strong habitat preferences with a certain degree of dispersal and colonization potential to new habitats along the animal excrement- phyllosphere-soil gradient. This study provides the first detailed comparison of microbial communities in different habitats in a single grassland, and offers new insights into the biogeographic patterns of the microbial assemblages in grasslands.