Distribution of soil types , vegetation and tree species diversity in Eastern Ghats of Srikakulam District , Andhra Pradesh , India

The present investigation was carried out on distribution of soil types, vegetation and tree species diversity in Eastern Ghats of Srikakulam District, Andhra Pradesh, India. The inventory of tree species was done in 40 different forest areas of Srikakulam district. All the sample plots are tropical and moist thorny forest and dry thorny scrub forests of Srikakulam district. The soils of the study area are compressed red soils, loamy soils, sandy loams, with varying proportions of sand and clay and it constitute 96% of the total area; red sandy soil is the common type. Tree species richness varied according to the disturbance gradient in the different stands, a total of 4744 individuals, belonging to 129 species, 96 genera among 46 families from 40 line transects were recorded in the study area. Species richness ranging from 47 to 9 in a transect was recorded in the present study. Highest species richness of sizes 47 for 65-N/14 (SW-3, 65N-14 NW-3) was seen at Haddubanghi and lowest diversity 9 was seen at Korasanda 74-B/1(SE-1).


INTRODUCTION
Biodiversity is used in describing the diversity of life on earth, it includes all life forms and the ecosystem of which they are part.In the developing countries, biodiversity provides the assurance of food, many raw materials such as fibre for clothing, materials for shelter, fertilizers, fuel and medicines as well as sources of work energy in the form of animal traction.In addition, biodiversity maintains balance for planetary and human survival (Jafferies, 1997).Species diversity in the tropics varies dramatically from place to place, as compared to other tropical forest types, (Holdridge 1967).Dry deciduous forests are among the most exploited and endangered ecosystems of the biosphere (Murphy and Lugo, 1986;Gentry, 1992).Studies from forest survey of India showed that an average of 54% of forest is effected by fire and 72% of forest area is subjected to grazing annually, 3.73 million hectors of forest area are burnt resulting in economic losses of approximately 440 crores (MOE,1999).Dry deciduous forests are among the most exploited and endangered ecosystems of the biosphere (Janzen, 1988;Gentry, 1992).The world wide destruction of the natural environment by population explosion, urbanization, industrialization and habitat fragmentation has led to a tremendous loss of biological diversity over the past few decades.Over exploitation is to severely reduce the population sizes below the critical level and consequently the survival of the species.Phyto-sociological investigation of vegetation serves as a pre-requisite for investigating the details of the primary productivity of an ecosystem.Tree species diversity, distribution and population structure of tropical forests of Eastern Ghats are poorly understood.We analyzed the structure of tropical deciduous forests in Srikakulam district of Eastern Ghats, Andhra Pradesh, India.

MATERIALS AND METHODS
Phytosociological studies carried out during July 2008 to June 2011 covered all spectrum of vegetation.The entire stretches of Eastern Ghats of Srikakulam district are divided into 6.25 x 6.25 km grid, based on the toposheets obtained.This expertise method of classification is obtained from UAS-ATREE team Bangalore (Jagadish et al., 2003).Each grid is from a sampling unit.The inventory of tree species was done in 40 different forest areas in Srikakulam district.In each forest area consider as one belt transect, one belt transect (Plot) of 5 x 1000 m in each of the 6.25 x 6.25 km (grid) is a sampling protocol with 0.01% of sampling intensity based on random sampling method.All the plots samples are from tropical dry deciduous forests, moist deciduous forests and scrub deciduous forests of Srikakulam district.In order to revisit these plots for seasonal sampling, latitude, longitude, altitude values were recorded by using a GPS (Garmen India) and other Geo-climatic features were identified and represented in Tables 1  and 2. The specimens were identified with the help of flora of Andhra Pradesh 3 Volumes (Pullaiah et al., 1997) and local floras like Flora of Srikakulam district (Rao R.S. and Hara Sreeramulu, 1986), studies on the vegetation and flora of Vizianagaram district (Venkaiah, 1980) and (Srinivasa et al., 2012) phytosociological studies on tree diversity of Srikakulam districts of Andhra Pradesh, India.

Study area
The Srikakulam district lies on the east coast of India between 18°-20 ' and 19°-10'N and 83°-50' and 84°-50' E. The total geographical area is 2,254 sq km.This area is bounded by Orissa State on the North and West and Bay of Bengal on the East and North east on the south and west Visakhapatnam district.These area consist of 37 mandals of different types of soils like red soils, loamy soils, sandy loams, with varying proportions of sand and clay and they constitute 96% of the total area .Red sandy soils area the common type.The climate of the region is generally tropical.The temperature in the hill areas is cooler than in plains because hills receive heavier rainfall.The mean maximum temperature is 30-40°C in April-May and the mean minimum temperature is 17.4°C in December-January during the summer season till the on-set of the South-West monsoon the heat is oppressive and the day temperature may sometimes be about 43°C.The rainfall in the region is considerably more in the hilly areas as compared to the plains.

RESULTS AND DISCUSSION
A total of 129 tree species were recorded from 40 tran-  1.In the present investigation, the highest altitude was recorded in Laada followed by Polla, Kothakota, Samarillu, Sara, Sunnapugedda and lowest altitude was recorded in Sakipuram.Total study area was divided into 40 grids , the number of species that occurred in each grid was recorded; 47 species in Huddubanghi (65N-14,SW-3) followed by 45 species in near Chapara (74B-1 SE-4) and Sundarada (74B-2 NE-1), 43 species at Sobha (74B-1(SW-2), 42 species at Sunnapagedda (65N-10 NE-3), 41 species at Yetugada (65 N-13 NW-2) etc were recorded in the entire forest area (Table 2).Tree species richness varied according to disturbance gradient in different, a total of 4744 individuals, belonging to 129 species, 96 genera among 46 families from 40 line transects in the study area are recorded in Tables 1 and 2).Species richness ranges from 47 to 9 in a transect, as recorded in the present study.Species richness was more 47 for 65-N/14(SW-3, 65 N/14 NW-3) at Haddubanghi and has least species diversity 9 at Korasanda 74 B/1 (SE-1).Species area and species individual accumulation curve against equal-sized sampling area in different vegetation types showed that species heterogeneity was higher in vegetation types at mid elevations while their abundance was higher in vegetation types at higher elevations (Jayakumar and Nair, 2013).In tropical rain forests, the ranges of tree species count per hectare is about 20 to maximum of 223 (Parthasarathy and Sethi, 1997), 42-47 species ha -1 (Kadavul and Parthasarathy, 1998).In the present investigations, maximum of 47 tree species per 1000 m (one transect) was recorded, these results agree with earlier observations of Parthasarathy and Sethi (1997) and Kadavul and Parthasarathy (1998).
In the present study, species richness in study sites are also correlated with the taxonomical studies, most of the trees show random distribution and was lowwhen compared with that of tropical forests of Indian Eastern Ghats and Western Ghats, that is, the number of species in Nallamalias, 69 (Sudhakar et al., 2008), Kolli hills, 25-56 (Chittibabu and Parthasaratthy, 2000), Kalarayan hills, 42-47 (Kadavul and Parthasarathy, 1999a).Shervarayan hills, 33-50 (Kadavul and Parthasarathy, 1999 b).The sacred grooves of Kerala 14-23, (Chandra Sekhar and Sankar, 1998), Thirumani Kuzhi sacred groove, 38 (Parthasarathy and Karthikeyan, 1997).The predominant forest areas of the study regions of Srikakulam district in Andhra Pradesh are tropical deciduous forests (Champion and Seth, 1968).Studies in this area reveal that the most abundant families were Rubiaceae and Mimosaceae (13), Moraceae (12), Euphorbiaceae (11), Fabaceae (9), Verbenaceae (9), Rutaceae, Anacardiaceae, Combretaceae and Ebenaceae with 6 species, respectively.An obvious variation in representation of tree species and the proportion of dominant species in the forests can directly be attributed to rainfall distribution and favorable topographic conditions.The present study also support the above fact that Euphorbiaceae, Fabaceae Num +---------+---------+---------+---------+---------+   (Mani and Parthasarathy, 2006), the total individuals reported in the study area is less when compared with various sites in Eastern Ghats, revealing the degradation of forests due to cut stumps; ecological factors like forest fires are predominant hence we can conclude that some parts of the study area were under frequent fires, which is degradation to the vegetation.

Conclusion
The findings of the current study suggested that the species richness ranges from 47-9 in a transect.Species richness was more than 47 for 65N/14 (SW-3, 65N/14 NW-3) at Haddubanghi and has least species diversity of 9 at Korasanda 74B/1 (SE-1).Further research should focus on the diversity of the tree species from nearby Srikakulam forest area which will be beneficial to the ecological and taxonomical status of the plant species.

Table 1 .
Latitude, longitude and altitude of the sampling areas and soil types of the study area.

Table 2 .
Details of the study area.