Abstract:

The concept of niche is one of the most important fundamental researches of modem ecology and it has percolated into many fields besides ecology. Niche mainly involves three aspects: niche breadth, niche overlap and niche differentiation. Based on the analysis of dominant periphytic algaes niche in the Gufu River, this paper explored the interactions among periphytic algae and their utilization of resources in mountain river. There were many reports about the niche of algae, which mostly focused on lakes or reservoirs. On the contrary, few reports were found focusing on mountain rivers. The Gufu River chosen as the research subject is a nearnatural river which has little human disturbance and a mountain river located in Shennongjia Forest District. In this paper, 22 dominant species of periphytic algae in spring and summer were firstly figured out by Mcnaughton dominance index in the Gufu River. Next, the niche breadth and niche overlap of these dominant species were respectively determined by using modified Smith and Pianka formulae, and niche differentiation was studied by Redundancy Analysis (RDA). The results showed that the most species of the dominant species were diatom and phytoplankton, but the number of diatom was far less than that of phytoplankton, and green algaes number was the least. The niche breadth and niche overlap of these dominant species were different in different periods. Based on their niche breadth in each month, the dominant species in the Gufu River could be classified into 5 groups, among which, Phormidium foveolarum, Achnanthes linearis and Aphanocapsa rivularis had broadest niche; the broader niche a dominant species had, the more resource it would occupy, conversely one with narrower niche. The niche overlap indices were the biggest between three dominant species above and phytoplankton, followed by diatom and green algae; the niche overlap indices between these three dominant species and the rest dominant species were roughly the same in the spring months, yet that were greater in the summer months which probably was due to the larger amount rainfall in summer. The RDA analysis showed that the spatial distribution of the dominant species was more affected by total nitrogen, pH, ammonia nitrogen and chemical oxygen demand; the first axis of RDA ordination map showed the change in total nitrogen, and the second axis showed the changes in ammonia nitrogen; Lyngbya aestuarii was estranged from its two variants and they had an evident niche differentiation; the most evident niche differentiation of these dominant species was green algae and the least evident was diatom. The following conclusions were drawn through the analysises of niche: Phormidium foveolarum, Achnanthes linearis, Aphanocaps arivularis which had broader niche breadth could reflect the overall water conditions of Gufu River, and those algae, like Pandorina morum, Microspora amoena and Gomphonema angustatum which had narrower niche breadth, could reflect the changes of one or several water factors; the index of niche overlap could judge whether the water of the Gufu River was disturbed by external factor or not; comparing RDA ordination map and the population of dominant periphytic algae, the changes of total nitrogen, ammonia nitrogen and pH could be caught out