Status and life strategy of Orchis punctulata Steven ex Lindl. (Orchidaceae) in the South-Eastern Crimea

This article presents the results of the population studies of rare protected species Orchis punctulata (Orchidaceae). Based on analysis of local floras in eastern and southeastern Crimea and personal observations, we identified the three most numerous populations of O. punctulata: two in the steppe (on the Tepe-Oba mountain ridge) and one in forest communities (on the Kiziltash mountain ridge). The ontogenetic, demographic, and vitality structures of the populations were studied. We also assessed the life strategies of the species in different habitats. The populations in steppe communities were characterized by high number and density parameters. O. punctulate often formed large clusters and was dominated here. A small number and low density characterized the population in the forest community; the distribution of individuals within the population was scattered. The age spectra were also different. The populations in steppe communities had a left-sided spectrum with a maximum in immature individuals, while in forest communities, it had a bimodal spectrum with maximums in generative (with a predominance of mature and old generative) and immature individuals. Specimens from forest communities were more extensive than those of steppe communities, they had longer leaves and inflorescences, and their inflorescences had a more significant number of flowers. As a result, the population in the forest community had a higher vitality index. It included individuals of the highest and middle class of vitality. The populations in the steppe community consisted of all classes of vitality or only of middle and lower classes. Thus, optimal environmental conditions for the growth of species are in forests. At the same time, a low level of regeneration and competition from other plants hinder its wide distribution. As a result, the species exserts as a phytocenotic patient (S-strategy). In steppe communities, the species is characterized by a mixed patient-explerant-violant strategy (SRC strategy).

Meadows of the Crimean Yaila

A comparative analysis of the vegetation composition in the meadow steppe community and the meadow in the middle in a karst sinkhole was made. The appearance of the meadow, which is formed by its coenogenous elements, is contrasted with the steppe. The compositions of the elements in two neighboring coenoses are also not similar. Obviously, the examined communities have different genesis. These differences are due to environmental conditions of karst depression. Yaila meadows are here indigenous primary vegetation of azonal origin.

A six-year grazing exclusion changed plant species diversity of a Stipa breviflora desert steppe community, northern China

Excluding grazers is one of most efficient ways to restore degraded grasslands in desert-steppe communities, but may negatively affect the recovery of plant species diversity. However, diversity differences between grazed and fenced grasslands in desert-steppe are poorly known. In a Stipa breviflora desert steppe community in Northern China, we established six plots to examine spatial patterns of plant species diversity under grazed and fenced conditions, respectively. We addressed three aspects of species diversity: (1) The logistic, exponential and power models were used to describe the species-area curve (SAR). Species richness, abundance and Shannon diversity values change differently with increasing sampling areas inside and outside of the fence. The best fitted model for SAR was the logistic model. Excluding grazers had a significant impact on the shape of SAR. (2) Variograms was applied to examine the spatial characteristics of plant species diversity. We found strong spatial autocorrelations in the diversity variables both inside and outside the fence. After grazing exclusion, the spatial heterogeneity decreased in species richness, increased in abundance and did not change in Shannon diversity. (3) We used variance partitioning to determine the relative contributions of spatial and environmental factors to plant species diversity patterns. Environmental factors explained the largest proportion of variation in species diversity, while spatial factors contributed little. Our results suggest that grazing enclosures decreased species diversity patterns and the spatial pattern of the S. breviflora desert steppe community was predictable.

Ecological responses of Stipa steppe in Inner Mongolia to experimentally increased temperature and precipitation. 2. Plant species diversity and sward characteristics

The responses of plant community diversity and sward characteristics to temperature and moisture changes on the Stipa steppe in Inner Mongolia were investigated in the growing season from 2013 to 2015. Warming significantly (P < 0.05) increased biomass and density. Highest biomass and density were achieved with warming and precipitation combined, whereas increased precipitation alone had no significant effect. Warming increased the Shannon–Weiner diversity index, which was significantly correlated with both air temperature (R2 = 0.45, P < 0.05) and soil temperature (R2 = 0.255 P < 0.05), and it was further increased by the combination of warming and increased precipitation. The Simpson index, an alternative measure of diversity that is not as sensitive to species richness, was less responsive to either warming or increased precipitation. Overall, warming had a more substantial effect than increased precipitation on the characteristics of the Stipa steppe community. However, its impact was complex, with significant variance among the 3 years of the study. The impacts of future changes in precipitation are also likely to be complex and warrant further research.