As a less time-consuming procedure, subsampling technology has been widely used in biological monitoring and assessment programs. It is clear that subsampling counts af fect the value of traditional biodiversity indic...As a less time-consuming procedure, subsampling technology has been widely used in biological monitoring and assessment programs. It is clear that subsampling counts af fect the value of traditional biodiversity indices, but its ef fect on taxonomic distinctness(TD) indices is less well studied. Here, we examined the responses of traditional(species richness, Shannon-Wiener diversity) and TD(average taxonomic distinctness: Δ +, and variation in taxonomic distinctness: Λ +) indices to subsample counts using a random subsampling procedure from 50 to 400 individuals, based on macroinvertebrate datasets from three dif ferent river systems in China. At regional scale, taxa richness asymptotically increased with ?xed-count size; ≥250–300 individuals to express 95% information of the raw data. In contrast, TD indices were less sensitive to the subsampling procedure. At local scale, TD indices were more stable and had less deviation than species richness and Shannon-Wiener index, even at low subsample counts, with ≥100 individuals needed to estimate 95% of the information of the actual Δ + and Λ + in the three river basins. We also found that abundance had a certain ef fect on diversity indices during the subsampling procedure, with dif ferent subsampling counts for species richness and TD indices varying by regions. Therefore, we suggest that TD indices are suitable for biodiversity assessment and environment monitoring. Meanwhile, pilot analyses are necessary when to determine the appropriate subsample counts for bioassessment in a new region or habitat type.展开更多
Invasions by exotic plant species and their impacts on invaded communities are a highly topical field of research because it provides a basis for the management of neophyte populations. However, for many invasive neop...Invasions by exotic plant species and their impacts on invaded communities are a highly topical field of research because it provides a basis for the management of neophyte populations. However, for many invasive neophyte species in Central Europe little is known about their impacts on invaded plant communities. Moreover, it has hardly been considered whether effects vary among habitat conditions. Here, we selected each ten sites with different habitat conditions invaded by Erigeron annuus, Fallopia japonica, Impatiens glandulifera and Solidago canadensis which were listed as invasive in Switzerland. At each site, we established four 4 m × 1 m subplots covering a gradient from very low to very high cover of the particular neophyte species to investigate the effect of increasing neophyte cover on the species richness, Shannon diversity and evenness of the invaded plant communities. Moreover, we measured soil pH and characterized habitat conditions using Ellenberg indicator values to light and soil fertility. Whereas increasing cover of I. glandulifera had no effect on the diversity of invaded plant communities, an increasing cover of E. annuus negatively affected Shannon diversity. An increasing cover of F. japonica combined with a decreasing soil pH negatively affected the Shannon diversity of invaded plant communities. Similarly, an increasing cover of S. canadensis in combination with decreasing soil fertility negatively affected the Shannon diversity and evenness of invaded communities. Our results indicate that significant effects of increasing neophyte cover are mostly coupled to particular habitat conditions and then rather suppress than eliminate native plant species in invaded communities. We therefore suggest including abiotic variables in further impact studies on biotic invasions. Furthermore, adapting measures to the respective environmental context can be a useful tool in priority setting for the management of invasive neophyte populations and the restoration of invaded habitats.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.31400469,41571495,31770460)the National Science and Technology Basic Research Program(No.2015FY110400-4)+2 种基金the China Three Gorges Corporation Research Project(No.JGJ/0272015)the Key Program of the Chinese Academy of Sciences(Comprehensive Assessment Technology of River Ecology and Environment for the Water Source Region of "South-toNorth Water Diversion Central Route")the Program for Biodiversity Protection(No.2017HB2096001006)
文摘As a less time-consuming procedure, subsampling technology has been widely used in biological monitoring and assessment programs. It is clear that subsampling counts af fect the value of traditional biodiversity indices, but its ef fect on taxonomic distinctness(TD) indices is less well studied. Here, we examined the responses of traditional(species richness, Shannon-Wiener diversity) and TD(average taxonomic distinctness: Δ +, and variation in taxonomic distinctness: Λ +) indices to subsample counts using a random subsampling procedure from 50 to 400 individuals, based on macroinvertebrate datasets from three dif ferent river systems in China. At regional scale, taxa richness asymptotically increased with ?xed-count size; ≥250–300 individuals to express 95% information of the raw data. In contrast, TD indices were less sensitive to the subsampling procedure. At local scale, TD indices were more stable and had less deviation than species richness and Shannon-Wiener index, even at low subsample counts, with ≥100 individuals needed to estimate 95% of the information of the actual Δ + and Λ + in the three river basins. We also found that abundance had a certain ef fect on diversity indices during the subsampling procedure, with dif ferent subsampling counts for species richness and TD indices varying by regions. Therefore, we suggest that TD indices are suitable for biodiversity assessment and environment monitoring. Meanwhile, pilot analyses are necessary when to determine the appropriate subsample counts for bioassessment in a new region or habitat type.
文摘Invasions by exotic plant species and their impacts on invaded communities are a highly topical field of research because it provides a basis for the management of neophyte populations. However, for many invasive neophyte species in Central Europe little is known about their impacts on invaded plant communities. Moreover, it has hardly been considered whether effects vary among habitat conditions. Here, we selected each ten sites with different habitat conditions invaded by Erigeron annuus, Fallopia japonica, Impatiens glandulifera and Solidago canadensis which were listed as invasive in Switzerland. At each site, we established four 4 m × 1 m subplots covering a gradient from very low to very high cover of the particular neophyte species to investigate the effect of increasing neophyte cover on the species richness, Shannon diversity and evenness of the invaded plant communities. Moreover, we measured soil pH and characterized habitat conditions using Ellenberg indicator values to light and soil fertility. Whereas increasing cover of I. glandulifera had no effect on the diversity of invaded plant communities, an increasing cover of E. annuus negatively affected Shannon diversity. An increasing cover of F. japonica combined with a decreasing soil pH negatively affected the Shannon diversity of invaded plant communities. Similarly, an increasing cover of S. canadensis in combination with decreasing soil fertility negatively affected the Shannon diversity and evenness of invaded communities. Our results indicate that significant effects of increasing neophyte cover are mostly coupled to particular habitat conditions and then rather suppress than eliminate native plant species in invaded communities. We therefore suggest including abiotic variables in further impact studies on biotic invasions. Furthermore, adapting measures to the respective environmental context can be a useful tool in priority setting for the management of invasive neophyte populations and the restoration of invaded habitats.
