Effects of Edaphic (Soil) Factors on Plant Distribution in Chameli Community Forest, Bhaktapur, Nepal

Horizontal (east, centre, west) and vertical (bottom, middle and top) distribution study of plants as well as the study of edaphic factors were done in 2016 in Chameli Community Forest hill. Soil samples were taken from bottom, middle and top areas of east, centre and west reasons of the hill. During this study, Schima wallichi and Rhododendron arboreum were found dominant species and had less effect of edaphic factors. Similarly climber plants like Smilax aspara, Smilax lancaefolia, Smilax ovalifolia and Dioscorea bulbifera were absent in west area of top region which might be due to low content of moisture, pH, and phosphorous. Scutellaria repens, Sida cordifolia, Solanum nigrum, Tripterospermum volubile, Carex baccans, Heteropogan contortus etc. were absent in west areas of middle region which might be due to the effect of high % of sand, phosphorous and moisture content and has low % of silt, potassium and pH. Herbs are more dominant in bottom, trees in middle and shrubs in top region. The east area of bottom, middle and top region had more diverse vegetation. The average of organic matter percentage, nitrogen, potassium and phosphorous content was maximum in middle hill which supports the highly diversified tree species and dense forest. Phosphorous showed the most effective factor on plant distribution. Therefore, for the proper growth, functioning and abundance of plant species, edaphic factors had a significant effect and play an important role on plant distribution.

During the study, it was found that subtropical plants species cover much numerous than the high hill plant species. This is due to the low elevation (1400-1590m) of the study area. Horizontally, eastern elements were found more numerous than the western. Therefore, from the study of Chameli Community Forest it was revealed that the forest was slightly disturbed, non-polluted, highly diversified and interesting. The study would be helpful for the people who are willing to get information on floristic composition of Chameli Community Forest.
Both the patterns of plant distribution viz. horizontal as well as vertical were recorded from bottom (1400masl) to top (1590masl) as well as horizontally into east, centre and west area were recorded (Table 2).

Soil Analysis (Edaphic Factors)
Physical analysis A. Moisture Content (MC%): When the moisture content were compared among east, centre and west areas of bottom region of the hill, high moisture percentage (4.2%) was found in west area while low (0.9%) in centre area of the bottom region of the hill. Similarly, when moisture % were compared among east, centre and west areas of middle region of the hill, high moisture % (4.8%) was found in west area while low (1.7%) in east area of the middle region of the hill. When moisture percentage were compared among east, centre and west areas of top region of the hill, high (4.2%) was noticed in centre area whereas low (0.8%) in west area of the top region of the hill.
Again, when moisture percentage were compared among east, centre and west areas of bottom, middle and top region, higher moisture % (4.8%) was found in west area of middle region and lower (0.8) in west region of the top region of the hill.
In an average, the highest (H) moisture percentage (3.0%) was recorded in middle region and the lowest (L) moisture % (2.3%) in top region of the hill (Table 3).
Herbs and trees sharply decreased in population on the top due to the lack of moisture (Lamichaney, 1995). Moisture of the soil is affected by texture and the amount of available water is low for the plants growing in coarse textured soil type (Olsen and Watanable, 1963). Soil moisture is highest in the west areas of middle region where vegetation abundance is low when compared with other in comparison with other areas (Table 3).

B. Texture:
When the texture of soil from different areas of bottom, middle and top region of the Chameli Community forest were analyzed, different soil types were found (Table 3). Soil collected from the Chameli Community forest were analyzed into sand, loamy sand, sandy clay, sandy loam and loamy sand. The sand % was higher when compared to silt % and clay % (Table 3). Loam and silty soils have better water relation properties as it is best for the growth of plants (Kramer, 1949). The soil type of this forest varies from sandy to sandy loam soil where NPK content was moderate. Soil factors control and maintain vegetation growth (Shrestha, 1979). The middle region of the forest on vertical distribution showed the higher trees dominancy which prefer to grow in coarse textured soil type.

C. Color:
The soil color helps to know the soil fertility of the area. The darker the soil, the more humus content present in it. The soil color in the study area were colorful such as brown, light brown, light red, brownish black, dark red, reddish brown and greyish brown ( Table 3). The highest diversity of plant was found in east area of the bottom, middle and top region of the hill where the soil color was brownish and light brown. Similarly, the soil color has adverse effect on soil fertility (Howell, 1988).

A. pH
When pH was compared among east, centre and west area of bottom region of the hill, high pH (6.8) was found in centre area while low (5.2) in west area of bottom region. Similarly, when pH was compared among east, centre and west areas of middle region, high (5.3) was recorded in west area whereas low (5.1) was found in east area of the middle region. When pH was compared among east, centre and west areas of top region, high (5.5) was found in centre region while low (5.0) in west area of top region.
Again, when pH was compared in east, centre and west areas of bottom, middle and top region, higher pH was found in (6.8) was found in centre areas of bottom region and lower (5.0) was recorded in west area of top region. In an average, the highest (H) pH (5.8) was found bottom region whereas the lowest (L) pH (5.2) in middle region of the forest (Table 4).
The higher pH was found in centre area of bottom region while lower in west area of top region. The soil was found to be less acidic, low phosphorous and high potassium at the bottom region (Table 4) which was suitable for herbs to grow vigorously (Baral, 1983). The growth of Rhododendron arboreum was dense in lower organic content and acidic soil in the west areas of the middle region as well as bottom region of hill (Pradhan and Ghimire, 1994).

B. Organic Matter (OM)
When organic matter was compared among east, centre and west areas of bottom region of the forest, high organic matter (4.9%) was found in east area and low (2.6%) in west area of the bottom region. Similarly, when organic matter was compared among east, centre and west areas of middle region high organic matter (6.4%) was found in centre area while low (2.4%) in east area of middle region. When organic matter was compared in east, centre and west areas of top region, high organic matter (4.2%) found in west area but low (1.9%) in centre area of top region of the hill.
Again, when organic matter was compared among east, centre and west areas of bottom, middle and top region, higher organic matter (6.4%) was found in centre area of middle region whereas lower (1.9%) in centre area of top region. In an average, the highest (H) organic matter (4.01%) was found in middle region while the lowest (L) organic matter (3.4%) in east area of top region (Table 4).
The higher organic matter was found in centre area of middle region whereas lower in centre area of top region. The middle region of the hill had highest content of organic matter, nitrogen, potassium and phosphorous (Table 4) in the soil which supports the large number of tree species to grow. The healthy growth of plant species requires the soil with all the minerals along with N, P, K, OM% etc. (Champion and Seth, 1968).

C. Nitrogen (N)
When nitrogen percentage was compared among east, centre and west areas of bottom region, high (0.25%) was found in east area while low (0.1%) in west area of bottom region of the hill. Similarly, when nitrogen percentage was compared among east, centre and west areas of middle region, high nitrogen (0.32%) was found in centre area while low (0.25%) in west area of middle region. When nitrogen % was compared among east, centre and west areas of top region, high (0.21%) nitrogen % was noticed in east area but low (0.1%) in centre area of top region (Table 4).
Again, when nitrogen percentage was compared among east, centre and west areas of bottom, middle and top region, higher nitrogen (0.32%) was found in centre area of middle region while lower (0.1%) in centre area of top region.
In an average, the highest (H) nitrogen (0.25%) was found in middle region whereas the lowest (0.16%) was found in top region of the forest.
Organic matter was very much related with pH and organic matter supplies mist of the nitrogen (Willem, 1990). The nitrogen content in the soil promote the proper growth and functioning of the plant species (Morphac et al, 1991). Nitrogen in the soil helps to increase soil structure and increase soil microorganism.

D. Phosphorous (P)
When phosphorous was compared among east, centre and west areas of bottom region, high phosphorous (50.4kg/h) was found in west area while low (18.3kg/h) in centre area of bottom region. Similarly, when phosphorous was compared among east, centre and west areas of middle region, high phosphorous (160.3kg/h) was found in west area while low (18.3kg/h) in centre area of middle region. When phosphorous was compared among east, centre and west areas of the top region, high phosphorous (91.6kg/h) was found in centre area whereas low (18.3kg/h) in west area of top region. Again, when phosphorous was compared in east, centre and west areas of bottom, middle and top region higher phosphorous (160.3 kg/h) was found in west area of middle region while low (18.3 kg/h) in centre areas of bottom and middle region as well as west area of top region.
In an average, the higher (H) phosphorous content (76.3kg/h) was found in middle region while the lowest (L) phosphorous (36.6kg/h) in bottom region of the hill (Table  4). The higher percentage of phosphorous in the west area of middle region showed medium plant diversity with dominant trees (Juwa, 1989).

E. Potassium (K)
When potassium was compared among east, centre and west areas of bottom region, high potassium (152.6kg/h) was found in west area while low (122.1kg/h) in east area of bottom region. Similarly, when potassium was compared among east, centre and west areas of middle region, high (225.9 kg/h) was found in east areas while low (67.2kg/h) in west area of middle region. When potassium was compared among east, centre and west areas of top region, high (122.1kg/h) was found in west area but low (73.3kg/h) in east area of top region.
Again, when potassium was compared in east, centre and west areas of bottom, middle and top region, higher potassium (225.9kg/h) was found in west area of bottom region while lower (67.2 kg/h) in west area of middle region.
In an average, the highest (H) potassium was found in middle region whereas the lowest (L) potassium was found in top region of the hill (Table 4).Vigorous growth of the herb species in the bottom region of the hill was due to the highest potassium content of soil and sand fraction increase with decreases in potassium (Failyer (1908).

Effect of Edaphic Factors on Plant Distribution
Dominant species i.e. which are found in both horizontal and vertical distribution pattern such as bottom (east, centre and west), middle (east, centre and west) and top (east, centre and west) of the Chameli Community Forest hill were Schima wallichi and Rhododendron arboreum (Bhattarai and Vetaas, 2006). So, these two species favors to grow in all type of soil factors such as sand % (high and low), silt (high and low), clay % (high and low), different types of soil such as sand, sandy loam, loamy sand, sandy clay loam etc. Similarly, they can grow in light brown to dark red color of the soil. The study showed that these two species might have less effect of low as well as high soil moisture pH, N, P, K and OM%.
Edaphic factor has great role in distribution of plants.

Conclusions
During the study of effect of edaphic factors on plant distribution, it was found that the plant species which were present in all area of the bottom, middle and top region eg. Schima wallichi and Rhododendron arboreum had less effect of physical and chemical soil factors. They could grow in a slight change in pH, N, P, K and OM content of the soil. Plant species such as Necotiana tabacum, Nyctanthes arbor-tristis, Salvia officinales and Curculigo orchiodes were present only in one area (east) of bottom region. These plants species might have effected due to less acidic soil and low phosphorous. The plant species, which were found only in one area (centre) of bottom region, were Jasminum humile and Rungia himalayenthes which might be due to the effect of high silt and clay %. Good quality of soil, which favors the growth of large number of vegetation, was found in middle hill. The average of organic matter percentage, nitrogen, potassium and phosphorous content was maximum in middle hill, which supports the highly diversified tree species and dense forest.