Evaluation of the Effects of Range Management Using SHE and Diversity Indices

The complexity of natural ecosystem, as the rangelands, is caused to propose the different approaches toevaluatethe ecosystem on the basis of sustainable and systematic management. Study on the interaction connectionsbetween plants and biotic and abiotic factors in the rangeland ecosystem can be achieved by relationsofmanagerial strategies in order to conduct the rangeland health. Vegetation cover, however, is disturbed based upon biotic (e.g. Climate, light, altitude, slope, and so on) and abiotic (e.g. Human and livestock) factors. If the animal disturbances continue to regressive position, ecological equilibrium and vulnerability of the ecosystem will be more changed. Overgrazing of animalaffectson vegetation structures, declines the organic matters, destroys the soil and creates the erosion, increases the runoff, decreases the infiltrability, and finally decreases all kinds of diversities and richness of species. Moreover, it will also decrease the life support system such as soil, medicinal plants, producing water and oxygen and so on.
Albeit animal productions from the rangelands have highly important values, lack of desirable grazing management policy can be caused to go down the drain of biodiversity in a given area and to decrease more diversity around the water sources in the rangeland where it is called a critical area in the Range Sciences. It is claimed that with increase of the distance from the water sources and decrease of animal grazing, the species diversity, vegetation cover, vertical vegetation structure, palatable perennial grasses and forbs will be increased while the annual species will be decreased. Notwithstanding, new approaches of livestock grazing can make forthe regressive species diversity. It means that omissionof the grazing from the ecosystem will be decreasing in the species richness and diversity. Hence, as a vegetative management, sectional exclosure of the rangeland can make opportunities for palatable species to increase. Based upon researched data, long-term exclosure increases the palatable and native species, but it also decreases the variability of species similar to grazing areas.
Vegetation cover is the main component of biodiversity and is the key element in the rangeland function (such as production and stability). Nowadays, many researchers endeavor to evaluate the economic approaches.On the basis of the ecosystem reality, they have been considered by scientists more than ever in the species diversities, such as alpha, beta, and gamma. The alpha diversity, based upon Whittaker’s definition, refers to the diversity in a given area which is generally obtained by the number of species (like species richness). If the changes of species diversity between some sites are the target, hence, the beta diversity will be achieved that is defined based upon the total amount of species at each site. The gamma diversity, however, refers to the whole amount of species at total sites in a region.
The biodiversity conservation can be obtained by drawing of the patterns and structures of the species diversity in term of the environmental changes. For instance, if the beta diversity in a given area is high level, it shows the heterogeneoushabitat and it, therefore, needs separately managerial strategy. Many studieshave been carried outabout the patterns of species diversity with regard to gradient of environmental changes and more time focused on precipitation gradient. However, there is less studies about the effects of biotic factors, e.g. the livestock grazing, on the changes of species diversity. The research of Jouri et al. (2015) in the northern aspect of Alborz rangeland showed that the beta and gamma diversities in the Ramianrangeland were the fair condition, because of good condition of rangeland.While the rangelands of Javaherdeh and Masooleh had high levels of the alpha diversity, because of their fair condition of rangelands.
Since the alpha diversity of the species is divided into two different components such as richness (S), which mentions to the number of species in the sampling unit, and evenness (E), which refers to the distribution of the species individual in the sampling unit; these elements can be mixed to determine the proportion of each component which is called the SHE index. The SHE index is a simple way can be obtainedbased upon the diversity index of Shannon (H) that is established by Information Theory and is made feasible to determine the spatial and temporal changes of plant species. Some researchers have used this method in their studies such as investigation of the species diversity in the marshland of Carolina state, coral cliffs of shoreland, and even for archaeological studies.
Unfortunately, in the past three decades, the progressive degradation of the rangelands in Iran, because of overgrazing, is experienced unbalance in the ecological equilibrium of the rangelands. In such cases, this disturbance activity was analysed by means of the species richness and diversity, but it is not surveyed by the objective interpretation, from all kinds of diversities such as alpha, beta, and gamma or SHE index, in a field area. For instance, some studies were mentioned to the proportion of the richness component in term of the evenness index in the Mahoor rangelands of Mamasani.Another study indicated that the evenness in term of richness index have some proportions of diversity and noting else. The current research, however, has endeavored to show an objective interpretation of the diversity in the Polour rangeland close to Damavand summit.
Three sites including long-term exclosure, key (is around Lar Dam and is known as Meli Park of Lar; it is 7 km far from the exclosure area), and grazing areas (it is 2 km far from the exclosure area and between the two sites) were selected. A 64 square meter grid was selectedin each site where 1 square meter plots were mosaically established side by side. This grid was proposed by Adler et al (2011) who believed this method can reduce the statistical error by way of diverse calculation in rows and columns. Cover percentage, density, and frequency of each species were then recorded in each plot. It is necessary to be told that the three sites had same geomorphological and topographical conditions such as flat area. Hence, this omits the interference of runoff or moisture and organic matter gradients. The rangeland condition of each site was obtained by the Daubenmier method in six classes such as excellent (81-100), good (70-80), fair (50-69), poor (30-49), very poor (11-29), and unusable (0-11).The rangeland trend was achieved by the Trend Balance method as well.
The Alpha (Shannon index; ), beta () and gamma () diversities using Whitaker index, richness (Margalef index; ), evenness (Sheldon index; ) indices.SHE () analysis were calculated in each plot using PAST software for both sites, including rows (which has been prevailing 8 rows) and columns (which has been existing 8 columns as well). Comparison of the three sites and grouping of them was respectively carried out by one way ANOVA and Duncan methods using SPSS v.22 software.
Results showed that the exclosure site has the excellent range condition with 86.34 scores and equalrangeland trend. The key site has good condition with 79.91 scores, which is going to be the excellent rangeland condition and the area has positive range trend as well. The grazing area, however, has the worst condition (poor) with a 31.25 score, which is going to be a very poor condition in rangeland, and regressive range trend as well. On the basis of the ANOVA analysis, three sites have a higher difference in... .
Optimal condition of ecological management was falling out the key area where it was going through grazing capacity and time entrance of livestock. The grazing site did not manage the rangeland and the long-term area must terminate the excluding to improving of rangeland condition and trend as this site going toward a unique cover of few species which can make fragile the site. On the other hand, this site with long term exclosure have been formed by a few species (such as Agropyronelongifromis) and the grazing land has also been covered by some species because of high pressure of livestock grazing as it can be observed overstocking in this area by ranchers. Overgrazing of the site has omitted many palatable plant species, which are native to these areas, and have put back by many less-palatable and unpalatable species. They are savoury to the livestock. As a matter of fact, many palatable and native plant species are getting clear of the area because of over ranching and less monitoring of them by Natural Resources Administrative experts. All at once, it can be said that the rangeland evaluation can be achieved by means of forming components of diversity indices (SHE) and other diversity indices such as alpha, beta, and gamma indicators.
For the most part, it can be saidthat by the SHE analysis, which refers to components of the diversity index, all kinds of the diversities indices (alpha, beta, and gamma diverisities) can evaluate the rangeland ecosystem well. The SHE analysis can also interpret the spatial and temporal changes of the diversity, richness, and evenness which can be used to elucidate the ecological condition of the rangeland ecosystem. In the current study, the most desirable ecological condition was found in the key area where the time of livestock enterance for grazing and the capacity grazing have been observed. The grazing area has the least diversity and richness and it then has not hadwell management. The long term exclosure also needs to be rehabilitatedwith light grazing strategy. On the other side, all sorts of diversity indices, which have been applied in this research, can draw an objective figure from the reality of the rangeland area. Therefore, it can easily make the rangeland ecosystem condition using SHE and diversities analyses.