¹Department of Botany Govt. Degree College Tral, J&K, India
²Department of Botany University of Kashmir Srinagar, J&K, India

^*Corresponding author:: Ganaie MM, Department of Botany Govt. Degree College Tral, J&K, India, Email: masoodmg@gmail.com

Copyright: © Ganaie MM, et al. 2021. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article Information: Submission: 13/05/2021; Accepted: 03/07/2021; Published: 13/07/2021

Species richness, evenness, species diversity and concentration of dominance, computed on the basis of density of constituent species during months and seasons, were used to study the community organization of protected temperate grassland in Kashmir Himalaya. The vegetation showed a strong seasonal pattern reflected by high species richness and diversity during favourable seasons and low during unfavourable season. The species diversity revealed an inverse relationship with concentration of dominance. The relative species, abundance pattern confirmed to log-normal pattern indicative of a heterogeneous assemblage of species with relative abundance distribution governed by many independent factors.

Species richness; Evenness; Species diversity; Relative abundance distribution; Dominance

Species diversity is an important structural attribute of a natural community and there is increasing evidence from experimental studies that plant diversity can influence a variety of ecosystem functions [1,2] particularly productivity [3] and stability [4-10]. Although species diversity in strict sense is the number of species (richness) in a community, it also includes relative abundance pattern of the species which also has been shown to have marked influence on the structure and function of the community [11] and as such a number of attempts have been made to explain the species abundance and distribution pattern of both real and idealized communities [12-14]. For plants the most common view is that both abundance and distribution reflect species’ relationships to resource availability (Mitchley and Grubb, 1986 and Mitchley, 1988) [15,16] but lately it has been shown that the ‘mobile’ dispersal phase also plays a role in determining species abundance pattern [17].

In view of the importance of such studies, a number of investigations have been conducted particularly on central Himalaya grasslands [18-22] to quantitatively analyse their community structure and function, but the temperate grasslands of Kashmir Himalaya are yet to be investigated hence the present study.

The present studies were carried out on a grassland with flat topography located in Srinagar district, lying at an altitude of 1576 m, above mean sea level and protected from any biotic disturbance for last five years. The climate of the study area was temperate with four distinct seasons viz. spring (March-May), summer (June- August), autumn (September-November) and winter (December- February). During the study period (March to next March) maximum temperature of about 30.1^o C was recorded during summer while a minimum of about -3.6^o C was recorded during winter (Figure 1). Annual precipitation of 345.9 mm during the study period was less than the annual average precipitation of 6.14.75 mm.

Twenty quadrats of 0.5 m2 size were randomly laid each month during the study period to record the number of individuals of each species and the density of constituent species was calculated after Curtis and Cottom (1965). In case of runners each node was taken equivalent to an individual and in respect of other rhizomatous species each upright shoot was considered as an individual [23]. The diversity indices, evenness, concentration of dominance and species abundance pattern was determined on the basis of density using following formulae: a) Diversity indices after [24]
N0 = Total number of species present
N1 = exp(Ĥ)
N2 = Reciprocal of Simpson’s index
N0 = Total number of species present
b) Shannon-Wiener’s index of general diversity after Shannon
and Wiener (1949) [25]
Ĥ = -Ʃpilnpi
where pi is the proportion of the total number of individuals
belonging to ith species
Ĥmax = log2S
where S is the total number of species
c)Equitibility or evenness indices
E1 = Ĥ/Ĥmax
E2 = (N2 -1)/(N1-1)/[26]
d) Concentration of dominance was by Simpson’s (1949) [27] formula
C = Ʃ(Pi)2
where Ĥ, Ĥmax, N1, N2 and pi are same as defined earlier.
Relationship between various attributes was studied through correlation and regression analysis.

The effective number of species (N0) revealed a very characteristic pattern of high species richness in month of March with consistent decline in intervening months. Lowest number of species [12] was recorded during January. The species richness, computed on the basis of abundant species (N1), was highest during March 2020 but also recorded increase during June and November (Table 1). Richness on the basis of very abundant species (N2) exhibited bimodal pattern with one peak in June and other in March 2021. Irrespective of index of species richness, lowest value was recorded in January.

The evenness index (E1) revealed three peaks in months of March 2019, June and November (Table 1). Evenness revealed an entirely different pattern (E2) when worked after [26]. Data reveals a low evenness value during March 2020 followed by an increase till October but during November it recorded a sharp decline and in the succeeding months a more or less regular pattern of increase and decrease was observed with highest value observed during February.

Ĥmax (Table 1) shows a more or less a uniform trend up to November followed by a decline with lowest value recorded in January. A sharp increase, however, was recorded after January with Ĥmaxregistering a peak value in March 2021. Species diversity computed on the basis of Shannon-Weiner information (Ĥ) also reveals a similar pattern of lowest value during January and highest during March.

The dominance index (C) revealed a more or less uniform pattern up to December followed by a sharp increase attaining a peak value in January, though marginal decrease was recorded during June. A consistent decline, however, was recorded after January.

The species richness in the present grassland reflects a seasonal pattern of maximum species richness during spring and minimum during winter. Such a seasonal pattern is indicative of the involvement of climatic variables chiefly precipitation and temperature pattern. The maximum species occurrence during spring could be attributed to the prevalence of favourable climatic conditions while the very cold climatic conditions during winter may be responsible for low species richness. Analysis of the relationship between species richness (N0) and the climatic variables revealed that precipitation pattern had a significant influence on it explaining about 37% variability in species variability in species richness and the two were related according to the following equation:

However, temperature and species richness (N0) showed an insignificant positive correlation (r = +0.27). In addition to climatic variables, changes in species composition have been attributed to plant phenology [28], germination attributes [29-31] cycling and availability of mineral nutrients, especially nitrogen [32-36] photosynthetic strategy [37] and edaphic conditions [38]. Thus, the seasonality in the species richness observed in the grassland during the present study could be attributed to intrinsic species-specific characteristics and a variety of biotic factors, besides climatic factors particularly precipitation pattern.

Evenness, a measure of how similar are the abundances of different species [39,40], has been related to a number of factors like strong current completion [41], soil fertility [42] and succession [43-46]. A low value of evenness indicates that one or a few species are highly dominant, while as a high value of evenness indicates that all the species in the community have rather similar abundance. In the present study, indices of evenness, in general, reveal high values during favourable seasons of spring, summer and autumn but low during unfavourable winter season suggestive of dominance of cold tolerant species during winter while a more or less similar abundance of constituent species during other seasons.

Diversity index, based on Shannon-Wienner information, further strengthens our earlier conclusion of strong seasonal influence on the community organization as the grassland under study was more diverse when favourable climatic conditions prevailed and least diverse during winter when climatic conditions were unfavourable. Furthermore, diversity index showed a negative relationship with concentration of dominance (Figure 2). The negative relationship is presumably due to richness in species composition of the community leading to distribution of importance value among many species, rather than in few species. Such negative relationship has been reported by [46-49] Increase in plant species richness has shown to increase above-ground biomass production [50-54] in experimental assemblages of grassland species, where species richness and functional composition were controlled through such a trend has not been observed in semi-natural grasslands [55,56]. In the present study also species diversity (log2S) and aboveground productivity did not reveal any significant positive relationship (r = +0.429) and species diversity explained only 18.44% of the variation in aboveground biomass.

The relative abundance pattern of species was used to interpret the nature and organization of the grassland community has been by [57,58,59]. The species – abundance curve (Figure 2) approached by the grassland under study, drawn by plotting log abundance (measured as density) and ranked from the most to the least abundant species, conforms neither to broken stick model nor to niche pre- emption model but conforms to log-normal relationship that indicates large and heterogeneous assemblage of species where abundance distribution pattern is governed by,many more or less independent factors [60] has further suggested that log-normal species abundance curve is reflective of communities in stable environments [61-64] and thus similar conclusions can be drawn for the grassland under study.

Climatic condition particularly temperature and precipitation have a positive effect on the species richness as indicated in the present study. High values of species richness during favourable seasons (with good temperature conditions) and low ones in unfavourable winter period indicates dominance of cold tolerant species during winter while a similar abundance of constituent species during other seasons. In the present study no significant relationship was found between species diversity and aboveground productivity. Shannon-Wienner diversity index in the present study showed a negative relationship with concentration of dominance. This seems due to richness in species composition of the community leading to distribution of importance value among many species, rather than in few species. The relative abundance pattern values of species in the present study indicates large and heterogeneous assemblage of species where abundance distribution pattern is governed bymany more or less independent factors. The values also indicate stability of the plant community under study.