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Plant Functional Trait Response to Habitat Change and Grazing in a Semiarid Grassland : Unravelling Species Turnover and Intraspecific Variation Effects

Zhang Jing, Zuo Xiaoan, Lv Peng, Zhao Shenglong, Zhao Xueyong

Polish Journal of Ecology

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2019

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Vol. 67, nr 1

62--74

EN

Plant community assembly is determined by species turnover and intraspecific trait variations (ITV) controlled by environment changes. However, little is known about how species turnover and ITV affect the responses of plant community to habitat changes and grazing disturbance in semiarid grasslands. Here, we measured five functional plant traits in four typical grassland habitats under fencing and grazing disturbance in a semiarid grassland, Northern China, including plant height, specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (LNC) and leaf carbon: nitrogen ratio (C:N). We also calculated the community weighted means (CWM) and non-weighted means (CM) of all traits and examined the relative roles of species turnover and ITV in affecting the responses of community traits to habitat changes and grazing disturbance. Our results showed that the CWM and CM values of five functional traits differed with grassland habitat changes. As compared to other grasslands, the Stipa steppe had the higher plant height, the sandy grassland had the higher SLA and lower LDMC, and the meadow had the lower LNC and higher C:N. Grazing decreased plant height across grassland habitats, as well as decreased SLA and increased LDMC in meadow. The responses of all community-level traits to habitat changes were driven by species turnover, while the responses of phenotypic traits (height, SLA and LDMC) to grazing were determined by both species turnover and ITV. So, we argue that ITV should be considered when understanding plant community assembly under grazing disturbance regime in semiarid grasslands.

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Lu T., Ma K., Zhang Y., Ni H., Fu B.

Polish Journal of Ecology

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2009

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Vol. 57, nr 4

647-657

EN

Disturbance is considered to be one of the main factors influencing variations in species diversity. While many experimental and observational studies provide a good understanding of how disturbance maintains the [alfa]-diversity, we know little about how disturbance influences [beta]-diversity, and the effects of disturbance intensity on spatial species turnover are lacking. The aim of this paper is to evaluate the effects of disturbance on patterns of species similarity in wetland communities, and to identify how disturbance intensity affects the species similarity - distance relationship. In our study, four isolated wetland remnants under different agricultural drainage ditch densities were surveyed in Sanjiang Plain, Northeast China. Wetland disturbance was assessed by agricultural ditch densities, and species similarity was quantified by the Jaccard index. A simple measure of environmental distance was obtained by using water level and five soil variables, and a corresponding measure of geographical distance was made between pairs of plots from each site. Based on these data, we estimated rates of distance decay through regression of log-transformed compositional similarity against both environmental and geographical distance for pair-wise comparisons of wetland plots from each site. One key finding of our research is that disturbance intensity does influence the species similarity - distance relationship. At each site, species similarity decreased significantly with distance, and both effects of geographical and environmental distance were statistically significant. The results indicate that with disturbance intensity increasing, the distance decay rate decreases.

3

Seasonal bird assemblages in a Mediterranean patchy wetland : corroborating the intermediate disturbance hypothesis

Malavasi R., Battisti C., Carpaneto G.

Polish Journal of Ecology

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2009

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Vol. 57, nr 1

171-179

EN

The structure of bird assemblages recorded in breeding and wintering period in a Mediterranean wetland of Central Italy was studied in order to evaluate their seasonal changes and the influence of land cover on their parameters. We identified three habitat macro-types, according to a man-disturbed gradient (from natural to man-made macro-types). Bird assemblages showed differences in relation to season and habitat type, either at quantitative (species richness, diversity index) or qualitative level (species composition and turnover, similarity). In winter, we obtained the higher values of mean species richness, Margalef richness, Shannon diversity, and [Beta]-diversity. The dendrogram of similarity showed a major clear-cut division between seasons, and a secondary division among habitat macro-types. In winter, assemblages were more rich and diverse, with a high turnover among point counts. The semi-natural habitat macro-types showed always the higher values of these indexes, with the exception of the [Beta]-diversity, which showed the highest value in winter but the lowest in the breeding period. The high mean values of richness ([alpha]-diversity) of the semi-natural habitat macro-types, especially in the breeding period could be mainly explained by the 'intermediate disturbance hypothesis'; on the contrary, differences in turn-over ([Beta]-diversity) between the seasons are mainly due to seasonal changes in habitat heterogeneity of this habitat macro-type (from an arid homogeneous pasture to a patchy flooded one). A pattern of intermediate disturbance was evident at mean species richness level (significant values) but not at diversity index level (not significant values). These results could imply specific strategies for the management of small wetlands, focused on maintaining a regime of natural (flooding) and man-made (grazing) disturbances.

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The parasitic Hymenoptera in a beech forest on limestone. 1, species composition, species turnover, abundance and biomass

Ulrich W.

Polish Journal of Ecology

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1998

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Vol. 46, no 3

261-289

EN

Between 1980 and 1987 a beech forest (Fagus sylvatica) on limestone near Gottingen (FRG) was studied using ground-photo-electors. 720 species of Hymenoptera were detected. 669 of the species were parasitoids, 29 phytophagous Tenthredinidae, Cynipidae and Eurytomidae, 9 ants, 4 vespids and 9 nest-building sphecids, megachilids, andrenids and bumble bees. Even after 8 years of sampling a great number of species seems to remain undetected. Estimates of extiction and immigration rates indicate species turnover rates of at least 5 to 10%. The abundance of the parasitic Hymenoptera ranged between 123 +- (1981) and 1078 +- 186 (1984) ind. m^-2 a^-1. The most important groups were the parasitoids of Diptera with 56 +- 15 (1981) to 936 +- 164 (1984) ind. m^-2 a^-1. As judged by the sorting according to parasitoid guild, the parasitoids of gall-makers (23 +- 9 to 880 +- 163 ind. m^-2 a^-1) and the egg-parasitoids (21 +- 17 to 102 +- 33 ind. m^-2 a^-1) reached the highest densities. The biomass of the parasitic wasps ranged between 19 +- 5 (1981) and 170 +- 92 (1987) mg DW m^-2 a^-1 with a mean of 68 mg DW m^-2 a^-1. In comparison with other important insect taxa this is a low value.