VARIABLES OF MORAINIC AND ALPINE ECOSYSTEMS
Global warming/ enhanced greenhouse effect and the loss of biodiversity are the major environmental issues around the world. The greatest part of the world’s population lives in the tropical regions. Mountainous regions in many cases provide favourable conditions for water supply due to orographically enhanced convective precipitation. Earth scientists are examining ancient periods of extreme warmth, such as the Miocene climatic optimum of about 14.5-17 million years ago. Fossil floral and faunal evidences indicate that this was the warmest time of the past 35 million years; a mid-latitude temperature was as much as 60C higher than the present one. Many workers believe that high carbon dioxide levels, in combination with oceanographic changes, caused Miocene global warming by the green house effect. Pagani et al. (1999) present evidence for surprisingly low carbon dioxide levels of about 180-290ppm by volume throughout the early to late Miocene (9-25 million years). They concluded that green house warming by carbon dioxide couldn’t explain Miocene warmth and other mechanism must have had a greater influence.
Carbon dioxide is a trace gas in the Earth’s atmosphere, which exchanges between carbon reservoirs in particularly the oceans and the biosphere. Consequently atmospheric concentration shows temporal, local and regional fluctuations. Since the beginning of industrialization, its atmospheric concentration has increased. The 1974 mean concentration of atmospheric CO2 was about 330 μmol mol-1 (Baes et. al., 1976), which is equivalent to 2574 x 1015 g CO2 702.4 x 1015 C assuming 5.14 x 1021 g as the mass of the atmosphere. This value is significantly higher than the amount of atmospheric CO2 in 1860 that was about 290 μmol mol-1 (617.2 x 1015 g). Precise measurements of the atmospheric CO2 concentration started in 1957 at the South Pole, Antarctica (Brown and Keeling, 1965) and in 1958 at Mauna Loa, Hawaii (Pales and Keeling, 1965). Records from Mauna Loa show that the concentration of CO2 in the atmosphere has risen since 1958, from 315 mmol mol-1 to approximately 360 315 mmol mol-1 in 1963 (Boden et al., 1994). From these records and other measurements that began more recently, it is clear that the present rate of CO2 increase ranges between 1.5 and 2.5 mmol mol-1 per annum. In the context of the Indian Himalayan region, the effect of warming is apparent on the recession of glaciers (Valdiya, 1988), which is one of the climatic sensitive environmental indicators, and serves as a measure of the natural variability of climate of mountains over long time scales (Beniston et al., 1997). However no comprehensive long-term data on CO2 levels are available. The consumption of CO2 by photosynthesis on land is about 120 x 1015 g dry organic matter/year, which is equivalent to about 54 x 1015gC/yr (Leith and Whittaker, 1975). Variations in the atmospheric CO2 content on land are mainly due to the exchange of CO2 between vegetation and the atmosphere (Leith, 1963; Baumgartner, 1969). The process in this exchange is photosynthesis and respiration. The consumption of CO2 by the living plant material is balanced by a corresponding production of CO2 during respiration of the plants themselves and from decay of organic material, which occurs mainly in the soil through the activity of bacteria (soil respiration). The release of CO2 from the soil depends on the type, structure, moisture and temperature of the soil. The CO2 concentration in soil can be 1000 times higher than in air (Enoch and Dasberg, 1971). Due to these processes, diurnal variations in the atmospheric CO2 contents on ground level are resulted.
High mountain ecosystems are considered vulnerable to climate change (Beniston, 1994; Grabherr et al., 1995; Theurillat and Guisan, 2001). The European Alps experienced a 20 C increase in annual minimum temperatures during the twentieth century, with a marked rise since the early 1980s (Beniston et al., 1997). Upward moving of alpine plants has been noticed (Grabherr et al., 1994; Pauli et al., 2001), community composition has changed at high alpine sites (Keller et al., 2000), and treeline species have responded to climate warming by invasion of the alpine zone or increased growth rates during the last decades (Paulsen et al., 2000). Vegetation at glaciers fronts is commonly affected by glacial fluctuations (Coe, 1967; Spence, 1989; Mizumo, 1998). Coe (1967) described vegetation zonation, plant colonization and the distribution of individual plant species on the slopes below the Tyndall and Lewis glaciers. Spence (1989) analyzed the advance of plant communities in response to the retreat of the Tyndall and Lewis glaciers for the period 1958- 1984. Mizumo (1998) addressed plant communities in response to more recent glacial retreat by conducting field research in 1992, 1994, 1996 and 1997. The studies illustrated the link between ice retreat and colonization near the Tyndall and Lewis glaciers. The concern about the future global climate warming and its geoecological consequences strongly urges development and analysis of climate sensitive biomonitoring systems. The natural elevational tree limit is often assumed to represent an ideal early warming line predicted to respond positionally, structurally and compositionally even to quite modest climate fluctuations. Several field studies in different parts of the world present that climate warming earlier in the 20th century (up to the 1950s – 1960s) has caused tree limit advances (Kullman, 1998). Purohit (1991) also reported upward shifting of species in Garhwal Himalaya.
The Himalayan mountain system is a conspicuous landmass characterised by its unique crescent shape, high orography, varied lithology and complex structure. The mountain system is rather of young geological age through the rock material it contains has a long history of sedimentation, metamorphism and magmatism from Proterozoic to Quaternary in age. Geologically, it occupies a vast terrain covering the northern boundary of India, entire Nepal, Bhutan and parts of China and Pakistan stretching from almost 720 E to 960 E meridians for about 2500 km in length. In terms of orography, the geographers have conceived four zones in the Himalaya across its long axis. From south to north, these are (i) the sub-Himalaya, comprising low hill ranges of Siwalik, not rising above 1,000 m in altitude; (ii) the Lesser Himalaya, comprising a series of mountain ranges not rising above 4000 m in altitude; (iii) the Great Himalaya, comprising very high mountain ranges with glaciers, rising above 6,000 m in altitude and (iv) the Trans-Himalaya, Comprising very high mountain ranges with glaciers. The four orographic zones of the Himalaya are not strictly broad morpho-tectonic units though tectonism must have played a key role in varied orographic attainments of different zones. Their conceived boundaries do not also coincide with those of litho-stratigraphic or tectono-stratigraphic units. Because of the involvement of a large number of parameters of variable nature, the geomorphic units are expected to be diverse but cause specific, having close links with mechanism and crustal movements (Ghosh, et al., 1989).
Soil is essential for the continued existence of life on the planet. Soil takes thousands of years to form and only few years to destroy their productivity as a result of erosion and other types of improper management. It is a three dimensional body consisting of solid, liquid and gaseous phase. It includes any part of earth’s crust, which through the process of weathering and incorporation of organic matter has become capable in securing and supporting plants. Living organisms and the transformation they perform have a profound effect on the ability of soils to provide food and fiber for expanding world population. Soils are used to produce crops, range and timber. Soil is basic to our survival and it is nature’s waste disposal medium and it serves as habitats for varied kinds of plants, birds, animals, and microorganisms. As a source of stores and transformers of plant nutrients, soil has a major influence on terrestrial ecosystems. Soil continuously recycles plant and animal remains, and they are major support systems for human life, determining the agricultural production capacity of the land (Anthwal, 2004). Soil is a natural product of the environment. Native soil forms from the parent material by action of climate (temperature, wind, and water), native vegetation and microbes. The shape of the land surface affects soil formation. It is also affected by the time it took for climate, vegetation, and microbes to create the soil. Soil varies greatly in time and space. Over time-scales relevant to geo-indicators, they have both stable characteristics (e.g. mineralogical composition and relative proportions of sand, silt and clay) and those that respond rapidly to changing environmental conditions (e.g. ground freezing). The latter characteristics include soil moisture and soil microbiota (e.g. nematodes, microbes), which are essential to fluxes of plant nutrients and greenhouse gases (Peirce, and Larson, 1996.). Most soils resist short-term climate change, but some may undergo irreversible change such as lateritic hardening and densification, podsolization, or large-scale erosion. Chemical degradation takes place because of depletion of soluble elements through rainwater leaching, over cropping and over grazing, or because of the accumulation of salts precipitated from rising ground water or irrigation schemes. It may also be caused by sewage containing toxic metals, precipitation of acidic and other airborne contaminants, as well as by persistent use of fertilizers and pesticides (Page et al., 1986). Physical degradation results from land clearing, erosion and compaction by machinery (Klute, 1986). The key soil indicators are texture (especially clay content), bulk density, aggregate stability and size distribution, and water-holding capacity (Anthwal, 2004).
Soil consists of 45% mineral, 25% water, 25% air and 5% organic matter (both living and dead organisms). There are thousands of different soils throughout the world. Soil are classified on the basis of their parent material, texture, structure, and profile There are five key factors in soil formation: i) type of parent material; ii) climate; iii) overlying vegetation; iv) topography or slope; and v) time. Climate controls the distribution of vegetation or soil organisms. Together climate and vegetation/soil organisms often are called the "active factors" of soil formation (genesis). This is because, on gently undulating topography within a certain climatic and vegetative zone a characteristic or typical soil will develop unless parent material differences are very great (Anthwal, 2004). Thus, the tall and mid-grass prairie soils have developed across a variety of parent materials.
Soil structure comprises the physical constitution of soil material as expressed by size, shape, and arrangement of solid particles and voids (Jongmans et al., 2001). Soil structure is an important soil property in many clayey, agricultural soils. Physical and chemical properties and also the nutrient status of the soil vary spatially due to the changing nature of the climate, parent material, physiographic position and vegetation (Behari et al., 2004).
Soil brings together many ecosystem processes, integrating mineral and organic processes; and biological, physical and chemical processes (Arnold et al., 1990, Yaalon 1990). Soil may respond slowly to environmental changes than other elements of the ecosystem such as, the plants and animal do. Changes in soil organic matter can also indicate vegetation change, which can occur quickly because of climatic change (Almendinger, 1990).
In high altitudes, soils are formed by the process of solifluction. Soils on the slopes above 300 are generally shallow due to erosion and mass wasting processes and usually have very thin surface horizons. Such skeletal soils have median to coarse texture depending on the type of material from which they have been derived. Glacial plants require water, mineral resources and support from substrate, which differ from alpine and lower altitude in many aspects. The plant life gets support by deeply weathered profile in moraine soils, which develops thin and mosaic type of vegetation. Most of the parent material is derived by mechanical weathering and the soils are rather coarse textured and stony. Permafrost occurs in many of the high mountains and the soils are typically cold and wet. The soils of the moraine region remain moist during the summer because drainage is impeded by permafrost (Gaur, 2002).
In general, the north facing slopes support deep, moist and fertile soils. The south facing slopes, on the other hand, are precipitous and well exposed to denudation. These soils are shallow, dry and poor and are often devoid of any kind of regolith (Pandey, 1997). Based on various samples, Nand et al., (1989) finds negative correlation between soil pH and altitude and argues that decrease in pH with the increase in elevation is possibly accounted by high rainfall which facilitated leaching out of Calcium and Magnesium from surface soils. The soils are invariably rich in Potash, medium in Phosphorus and poor in Nitrogen contents.
However, information on geo-morphological aspects, soil composition and mineral contents of alpine and moraine in Garhwal Himalaya are still lacking. Present investigation was aimed to carry out detail observations on soil composition of the alpine and moraine region of Garhwal Himalaya.
As far as the recordings of abiotic environmental variables of morainic and alpine ecosystems of Dokriani Bamak are concerned, the atmospheric carbon dioxide and the physical and chemical characteristics of the soil were recorded under the present study. As these are important for the present study.
4.1.1. Atmospheric Carbon Dioxide
Diurnal variations in the atmospheric CO2 were recorded at Dokriani Bamak from May 2005- October 2005. Generally the concentration of CO2 was higher during night and early morning hours (0600-0800) and lower during daytime. However, there were fluctuations in the patterns of diurnal changes in CO2 concentration on daily basis.
In the month of May 2005, carbon dioxide concentration ranged from a minimum of 375µmol mol-1 to a maximum of 395µmol mol-1. When the values were averaged for the measurement days the maximum and minimum values ranged from 378µmol mol-1 to 388µmol mol-1. A difference of 20µmol mol-1 was found between the maximum and minimum values recorded for the measurement days. When the values were averaged, a difference of 10µmol mol-1 was observed between maximum and minimum values.
During the measurement period, CO2 concentrations varied from a minimum of 377μmol mol-1 at 12 noon to a maximum of 400μmol mol-1 at 0800 hrs in the month of June, 2005. When the CO2 values were averaged for 6 days, the difference between the minimum and maximum values was about 23μmol mol-1.
In the month of July, levels of carbon dioxide concentrations ranged from a minimum of 369μmol mol-1 to a maximum of 390μmol mol-1. When the values of the carbon dioxide concentrations for the measuring period were averaged, the difference between the minimum and maximum values was about 21μmol mol-1.
Carbon dioxide concentration ranged from a minimum of 367μmol mol-1 to a maximum of 409μmol mol-1 during the month of August. When the values of carbon dioxide were averaged for the measurement days, the difference in the minimum and maximum values was about 42μmol mol-1.
During the measurement period (September), CO2 concentrations varied from a minimum of 371μmol mol-1 at 12 noon to a maximum of 389μmol mol-1 at 0600 hrs indicating a difference of 18μmol mol-1 between the maximum and minimum values. When the values of the measurement days were averaged the minimum and maximum values ranged from 375μmol mol-1 to 387μmol mol-1 and a difference of 12μmol mol-1 was recorded.
During the month of October, carbon dioxide levels ranged from a minimum of 372μmol mol-1 at 1400 hrs to a maximum of 403μmol mol-1 at 2000 hrs indicating a difference of 31μmol mol-1. When the values were averaged, the carbon dioxide levels ranged from a minimum of 376μmol mol-1 to a maximum of 415μmol mol-1.A difference in the minimum and maximum values was found to be 39µmol mol-1 when the values were averaged for the measurements days.
In the growing season (May-October) overall carbon dioxide concentration was recorded to be highest in the month of June and seasonally it was recorded highest during the month of October
4.1.2. A. Soil Physical Characteristics of Soil
Soil Colour and Texture
Soils of the study area tend to have distinct variations in colour both horizontally and vertically (Table 4.1). The colour of the soil varied with soil depth. It was dark yellowish brown at the depth of 10-20cm, 30-40cm of AS1 and AS2, brown at the depth of 0-10cm of AS1 and AS2 and yellowish brown at the depths of 20-30cm, 40-50cm, 50-60cm of AS1 and AS2). Whereas the soil colour was grayish brown at the depths of 0-10cm, 30-40cm, 50-60cm of MS1 and MS2, dark grayish brown at the depths of 10-20cm, 20-30cm of MS1 and MS2 and brown at the depth of 40-50cm of both the moraine sites (MS1 and MS2).
Soil texture is the relative volume of sand, silt and clay particles in a soil. Soils of the study area had high proportion of silt followed by sand and clay (Table 4.2). Soil of the alpine sites was identified as silty loam category, whereas, the soil of the moraine was of silty clayey loam category.
The soil temperature depends on the amount of heat reaching the soil surface and dissipation of heat in soil. Figure 4.2 depicts soil temperature at all the sites in the active growth period. A maximum (13.440C) soil temperature was recorded during the month of July and minimum (4.770C) during the month of October at AS1. The soil temperature varied between 5.10C being the lowest during the month of October to 12.710C as maximum during the month of August at AS2. Soil temperature ranged from 3.240C (October) to 11.210C (July) at MS1. However, the soil temperature ranged from 3.40C (October) to 12.330C (July) at MS2.
Soil Moisture (%)
Moisture has a big influence on soil’s ability to compact. Some soils won’t compact well until moisture is 7-8%. Likewise, wet soil also doesn’t compact well. The mean soil water percentage (Fig. 4.3) in study area fluctuated between a maximum of 83% (AS1) to a minimum of 15% (AS2). The values of soil water percentage ranged from a minimum of 8% (MS2) to a maximum of 80% (MS1). Soil water percentage was higher in the month of July at AS1 and during August at MS1 (. During the month of June, soil water percentage was recorded minimum in the lower depth (50-60cm) at both the sites.
Water Holding Capacity (WHC)
The mean water holding capacity of the soil varied from alpine sites to moraine sites (Table 4.4). It ranged from a maximum of 89.66% (August) to a minimum of 79.15% (May) at AS1. The minimum and maximum values at AS2 were 78.88% (May) to 89.66% (August), respectively. The maximum WHC was recorded to be 84.61 % during the month of September on upper layer (0-10 cm) at MS1 and minimum 60.36% during the month of May in the lower layer (50-60cm) at MS1. At MS2, WHC ranged from 60.66% (May) to 84.61% (September). However, maximum WHC was recorded in upper layers at both the sites of alpine and moraine.
The soil pH varied from site to site during the course of the present study (Table 4.5). Mean pH values of all the sites are presented in Figure 4.4 The soil of the study area was acidic. Soil of the moraine sites was more acidic than that of the alpine sites. Soil pH ranged from 4.4 to 5.3 (AS1), 4.5 to 5.2 (AS2), 4.9 to 6.1 (MS1) and 4.8 to 5.7 (MS2).
4.1.2 B. Chemical Characteristics of Soil
Organic Carbon (%): Soil organic carbon (SOC) varied with depths and months at both the alpine and moraine sites (Table 4.6). High percentage of organic carbon was observed in the upper layer of all sites during the entire period of study. Soil organic C decreased with depth and it was lowest in lower layers at all the sites. Soil organic carbon was maximum (5.1%) during July at AS1 because of high decomposition of litter, while it was minimum (4.2%) during October due to high uptake by plants in the uppermost layer (0-10 cm). A maximum (5.0%) SOC was found during the month of July and minimum (4.1%) during October at AS2. At the moraine sites, maximum (3.58%, 3.73%) SOC was found during June and minimum (1.5% and 1.9%) during August at MS1 and MS2 respectively.
Phosphorus (%): A low amount of phosphorus was observed from May to August which increased during September and October. The mean phosphorus percentage ranged from 0.02 ± 0.01 to 0.07 ± 0.03 at AS1 and AS2. It was 0.03±0.01 to 0.03±0.02 at MS1 and MS2. Maximum percentage of phosphorus was estimated to be 0.09 in the uppermost layer (0-10 cm) during October at AS1. The lower layer (40-50 cm) of soil horizon contained a minimum of 0.01% phosphorus during September at AS1 and AS2. In the moraine sites (MS1 and MS2), maximum phosphorus percentage of 0.03 ±0.01 was estimated in the upper layers (0-10, 10-20, 20-30 cm) while it was found to be minimum (0.02±0.01) in the lower layers (30-40 cm). Overall, a decreasing trend in amount of phosphorus was found with depth in alpine as well as moraine sites
Potassium (%): A decline in potassium contents was also observed with declining depth during the active growing season. Maximum value of potassium was found in the uppermost layer (0-10 cm) at all the sites. The mean values ranged from 0.71±0.02 to 46±0.06 at AS1 while it was 0.71±0.02 to 0.47±0.05 at AS2. In the moraine sites the values ranged from a minimum of 0.33 ±0.06 to a maximum of 0.59±0.05 in the MS1 and from 0.59±0.05 to 0.32±0.06 at MS2. In the upper layer of soil horizon (0-10 cm), maximum value of 0.74 %, 0.75% of potassium was observed during the month of July at AS1 and AS2. While the values were maximum in the month of October at moraine sites MS1 and MS2 having 0.66% and 0.65% respectively
Nitrogen (%): Highest percentage of nitrogen was found in the upper layers at all the sites. Maximum percentage of nitrogen were found during the month of July-August (0.25%, 0.25 and 0.26%, 0.25%) at AS1 and AS2, respectively. Maximum values of 0.18% and 0.15% respectively were found during the month of June at the moraine sites MS1 and MS2. The nitrogen percentage ranged from 0.23±0.02 to 0.04±0.01% at AS1. However, it ranged from a minimum of 0.05±0.01 to 0.24±0.02% at AS2. The nitrogen percentage ranged from a minimum of 0.03±0.01, 0.02±0.04% to a maximum of 12±0.03, 13±0.01%, respectively at MS1 and MS2 Overall, a decreasing trend was noticed in the nitrogen percentage with depth at both the alpine and moraine sites.
Soil has a close relationship with geomorphology and vegetation type of the area (Gaur, 2002). Any change in the geomorphological process and vegetational pattern influences the pedogenic processes. However, variability in soil is a characteristic even within same geomorphic position (Gaur, 2002). Jenney (1941) in his discussion on organisms as a soil forming factors treated vegetation both as an independent and as dependent variable. In order to examine the role of vegetation as an independent variable, it would be possible to study the properties of soil as influenced by vegetation while all other soil forming factors such as climate, parent material, topography and time are maintaining at a particular constellation. Many soil properties may be related to a climatic situation revealing thousand years ago (e.g. humid period during late glacial or the Holocene in the Alps and Andes (Korner, 1999).
The soil forming processes are reflected in the colour of the surface soil (Pandey, 1997). The combination of iron oxides and organic content gives many soil types a brown colour (Anthwal, 2004). Many darker soils are not warmer than adjacent lighter coloured soils because of the temperature modifying effect of the moisture, in fact they may be cooler (Pandey, 1997). The alpine sites of the resent study has soil colour varying from dark yellowish brown/yellowish brown to brown at different depths. Likewise, at the moraine sites, the soil colour was dark grayish brown/grayish brown to brown. The dark coloured soils of the moraine and alpine sites having high humus contents absorb more heat than light coloured soils. Therefore, the dark soils hold more water. Water requires relatively large amount of heat than the soil minerals to raise its temperature and it also absorbs considerable heat for evaporation. At all sites, dark colour of soil was found due to high organic contents by the addition of litter.
Soil texture is an important modifying factor in relation to the proportion of precipitation that enters the soil and is available to plants (Pandey, 1997). Texture refers to the proportion of sand, silt, and clay in the soil. Sandy soil is light or coarse-textured, whereas, the clay soils are heavy or fine-textured. Sand holds less moisture per unit volume, but permits more rapid percolation of precipitated water than silt and clay. Clay tends to increase the water-holding capacity of the soil. Loamy soils have a balanced sand, silt, and clay composition and are thus superior for plant growth (Pidwirny, 2004). Soil of the alpine zone of Dokriani Bamak was silty predominated by clay and loam, whereas the soil of moraine zone was silty predominated by sand and clay.
There is a close relationship between atmospheric temperature and soil temperature. The high organic matter (humus) help in retaining more soil water. During summers, high radiations with greater insulation period enhance the atmospheric temperature resulted in the greater evaporation of soil water. In the monsoon months (July-August) the high rainfall increased soil moisture under relative atmospheric and soil temperature due to cloud-filter radiations (Pandey, 1997). Owing to September rainfall, atmospheric and soil temperatures decreased. The soil moisture is controlled by atmospheric temperature coupled with absorption of water by plants. During October, occasional rainfall and strong cold winds lower down the atmospheric temperature further. The soil temperature remains more or less intact from the outer influence due to a slight frost layer as well as vegetation cover. Soil temperature was recorded low at the moraine sites than the alpine sites. During May, insulation period increases with increase in the atmospheric and soil temperature and it decreases during rainfall. The increasing temperature influences soil moisture adversely and an equilibrium is attained only after the first monsoon showers in the month of June which continued till August. Donahue et al. (1987) stated that no levelled land with a slope at right angle to the Sun would receive more heat per soil area and will warm faster than the flat surface.
The soil layer impermeable to moisture have been cited as the reason for treelessness in part of the tropics, wherein it’s absence savanna develops (Beard, 1953). The resulting water logging of soil during the rainy season creates conditions not suitable for the growth of trees capable of surviving the dry season.
The water holding capacity of the soil is determined by several factors. Most important among these are soil texture or size of particles, porosity and the amount of expansible organic matter and colloidal clay (Pandey, 1997). Water is held as thin film upon the surface of the particles and runs together forming drops in saturated soils, the amount necessarily increases with an increase in the water holding surface. Organic matter affects water contents directly by retaining water in large amount on the extensive surfaces of its colloidal constituents and also by holding it like a sponge in its less decayed portion. It also had an indirect effect through soil structure. Sand particles loosely cemented together by it, hence, percolation is decreased and water-holding capacity increased. Although fine textured soil can hold more water and thus more total water holding capacity but maximum available water is held in moderate textured soil.
Porosity in soil consists of that portion of the soil volume not occupied by solids, either mineral or organic material. Under natural conditions, the pore spaces are occupied at all times by air and water. Pore spaces are irregular in shape in sand than the clay. The most rapid water and air movement is observed in sands than strongly aggregated soils.
The pH of alpine sites ranged from 4.4 to 5.3 and it ranged from 4.8 to 6.1 in moraine sites of Dokriani Bamak. It indicated the acidic nature of the soil. The moraine sites were more acidic than the alpine sites. Acidity of soil is exhibited due to the presence of different acids. The organic matter and nitrogen contents inhibit the acidity of soil. The present observations pertaining to the soil pH (4.4 to 5.3 and 4.8 to 6.1) were more or less in the same range as reported for other meadows and moraine zones. Ram (1988) reported pH from 4.0-6.0 in Rudranath and Gaur (2002) on Chorabari. These pH ranges are lower than the oak and pine forests of lower altitudes of Himalayan region as observed by Singh and Singh, 1987 (pH:6.0-6.3). Furthermore, pH increased with depth. Bliss (1963) analyzed that in all types of soil, pH was low in upper layers (4.0-4.30) and it increased (4.6-4.9) in lower layer at New Hampshire due to reduction in organic matter. Das et al. (1988) reported the similar results in the sub alpine areas of Eastern Himalayas. All these reports support the present findings on Dokriani Bamak strongly. A potent acidic soil is intensively eroded and it has lower exchangeable cation, and possesses least microbial activity (Donahue et al., 1987). Misra et al., 1970 also observed higher acidity in the soil in the region where high precipitation results leaching. Koslowska (1934) demonstrated that when plants were grown under conditions of known pH, they make the culture medium either more acidic or alkaline and that this property differed according to the species.
Soil properties may change in response to heat and increased exposure (Ralston and Hatchell, 1971). The short term effects on nutrient availability depend on thermal effects of the fire on organic compounds, the rise in soil pH and the microbial processing of organic matter (Binkley et al., 1993).
High precipitation increased soil moisture during rainy season. Under the present study, soil moisture varied from 19.07 to 85.00 % (alpine) and 8.00 to 80.00% (moraine). Higher values of soil moisture were recorded during monsoon season from 48.00 to 83.00 % in alpine sites and 31.00 to 76.00% in moraine sites.
WHC of soil is directly influenced by the soil texture. Water is a solvent for vital plant nutrients. The presence of water and its movement through the soil affects the availability of these nutrients to the plants. Texture, structure, and physical conditions of surface and subsoil layers affect vertical drainage and capacity of soil to store water. The ideal moisture level is attained when water occupies one half of the pore spaces in soil structure. Soil is saturated when all the pore spaces are filled with water. Saturated soil has no oxygen in its pore spaces. Better utilization of rainfall, irrigation facilities and effective control of soil erosion and runoff depends largely on the water retention and transmission properties (Kumar et al., 2002). The higher values of WHC were estimated in all the stands and in both the alpine and moraine sites during the rainy season. The WHC was recorded to be low in the month of May at all sites.
The mineral components of an ecosystem operate in a dynamic state through a series of inputs and outputs of the essential elements (Anthwal, 2004). Plants and soils are the subsystem of this dynamic system and serve as storage compartment, while the atmosphere can be considered as an open reservoir, fluxes of nutrients from plants occur to soil via litter formation (Karunaichamy and Paliwal, 1995). Availability of soil carbon and nitrogen as nutrients can be important factor regulating forest nutrient cycling (Anthwal, 2004). Carbon and nitrogen are critical to many aspects of plant, herbivore and microbial metabolism (Reich et al., 2006). Given rising levels of atmospheric carbon dioxide, the coupled cycling of carbon and nitrogen is also critical to ecosystem functioning. Interactions involving carbon and nitrogen that might influence the global carbon cycle are of great importance to atmosphere-biosphere interactions and thus to human society because changes in elevated carbon dioxide have a direct impact on global climate. Interactions involving carbon and nitrogen likely modulate terrestrial ecosystem responses to elevated atmospheric CO2 levels at scales from the leaf to the globe and from the second to the century. In particular, response to elevated CO2 may influence soil nitrogen processes that regulate nitrogen availability to plants. Such responses could constrain the capacity of terrestrial ecosystems to acquire and store carbon under rising elevated carbon dioxide levels (Reich et al., 2006). Organic matter inputs to the soil, in the form of plant or animal detritus, are a primary source of both carbon and nitrogen (Gosz et al., 1973; Aber and Melillo, 1991). Nitrogen is the most important nutrient stored in soil, primarily in soil organic matter from which it is mineralized by ammonium-N by the action of enzymes, produced by soil organisms. Nitrogen is the nutrient that limits grass growth. Loss of nitrogen and release of other nutrients are associated with decrease in the organic matter content of the forest floor (Chandler et al., 1983). If land use change leads to increased N losses or reduced plant-available N, plant uptake and forest productivity may decline overtime (Parfitt et al., 2003). The forms of N and their rate of formation influence the competitive outcome between plants and soil microorganisms (Kaye and Hart, 1997) and can influence potential C storage (Nadelhoffer et al., 1999). The relationship among soil C concentration or contents and biotic and biotic predictor variables varied across the landscape, but elevation explained much of the variability in soil C (Powers et al., 2002). Sagger et al. (1994, 1996) have shown that the turn over time of freshly added C substrates is greater with soils that have greater specific surface and greater capacity to absorb organic matter. Thus, soil specific surface area may also influence the soil organic matter levels in soils. In response to change in aspect and slope, soil organic carbon also varied. Soil organic carbon is higher on north than on south aspects because of the drying and heating effects of increased exposure to solar radiation on south aspects (Frank and Lee, 1966). As solar radiation decreased in north aspect soil organic carbon increased regularly on slope. Daniels et al. (1987) reported that on north facing slopes organic content were higher on horizon A. Horizon A was darker in colour on north aspect because of the presence of greater organic carbon. The climate on north aspect would be more favorable to higher vegetative inputs, greater litter incorporation, and lower erosion rates than the south aspects.
Soil organic carbon was resident in litter layers longer on south aspects because of the drier climate, lower geophage activity, and higher amount of high-lignin leaves (Miller et al., 2004). The soil carbon (C) pool composed of soil organic C and soil inorganic C is not only critical for the soil to perform its productivity and environmental functions, but also plays an important role in the global C cycle (Sahrawat, 2003).
Elevated CO2 concentrations often lead to increased inputs of carbon into soil, and mainly through increased detritus production and root exudation (Cheng and Johnson, 1998; Hungate et al., 1997; Ineson et al., 1996; Pregitzer et al., 2000), potentially stimulating soil organic matter decomposition and microbial biomass. Some studies have suggested that elevated CO2 increases lignin concentrations in litter that may reduce decomposition per gram litter and increase soil carbon sequestration (Cotrufo et al., 1998; Van Ginkel et al., 1996), little evidence for this mechanism exists (Cotrufo et al., 1994; Norby et al., 2001). Recent studies have shown that most of the additional carbon released into the soil in response to elevated CO2 is labile and decomposes quickly, and therefore does not alter carbon storage significantly (Hungate et al., 1997; Norby et al., 2002; Schlesinger and Lichter 2001; Tate and Ross 1997; Van Kessel et al., 2000). Increased labile carbon inputs into the soil in response to elevated CO2 could in turn stimulate microbial activity and increase soil nitrogen availability (Martin Olmedo et al., 2002; Zak et al., 1993) or decrease soil nitrogen availability via greater microbial nitrogen immobilization (Diaz et al., 1993; Gill et al., 2002). The effect of plant diversity on microbial activity and C and N dynamics remain controversial. Increased plant diversity has been shown to increase soil respiration and microbial biomass because of increased net primary productivity and therefore greater carbon inputs (Craine and Wedin 2002; Zak et al., 2003) but has also been shown to have no effect on soil respiration and microbial biomass (Wardle et al., 1999). Higher plant diversity could decrease soil nitrogen immobilization into accruing litter (Knops et al., 2001). Alternatively, higher diversity could reduce nitrogen losses through leaching (Tilman et al., 1996, 1997) or increase inputs through nitrogen fixation because of increased probability of the presence of nitrogen fixing plants (Spehn et al., 2002; Zanetti et al., 1997), thereby increasing nitrogen availability. Elevated carbon dioxide increases labile carbon pools in soils, likely because of increased above and below ground plant productivity (Reich et al., 2001a, b).
Nitrogen is the most important element in the structure and metabolism of the plant and the need of the plant for a continuous supply of nitrogen dramatically point out one of the nature’s most paradoxical situations. Humus contains more nitrogen than other mineral elements (Rychnocaska, 1979). Nitrogen content was recorded maximum in alpine sites than the moraine sites due to the occurrence of forb species. The knowledge of nitrogen concentration in various soil-vegetation components at different stages of life cycle of plants is considered useful in determining the visual symptoms of nitrogen excess or deficiency (Embleton et al., 1959). In alpine meadows, the high capacity for nitrogen fixation by natural means is of importance, since it provides a source of cheap protein production. In different grassland ecosystems, the status of nitrogen has been worked out by Hannon, 1958; Porter, 1969; Bokhari and Singh, 1975; Paul, 1976; Billore and Mall 1976; Tiwari, 1982 and in the moraine by Gaur, 2002. With the advent of rain in June-July, the nitrogen contents in the soil started increasing and it continued till August and later a gradual decrease in soil nitrogen was observed upto May in both the alpine and moraine sites under the present study on Dokriani Bamak.
Increased soil organic matter inputs have been suggested as a management alternative for increasing phosphorus availability in highly adsorbing soils (Teissen, 1989). The optimum organic matter content of soil depends on local climate, the amount and type of clay material present in the soil, and the soil, and the soil’s intended use (Satya Priya etal., 1997).
Odum (1969) stated that phosphorus cycle is truly a close one as phosphorus is relatively a stable element in an annual grassland ecosystem, it is added to the system in very small amounts from natural external sources. Singh and Jones (1976) reported that the C: P ratio determined whether or not organic materials increased or decreased P availability. Phosphorus availability in soil is associated with other soil minerals and is very important property of soil. Availability of phosphorus in soil nutrition is very important because the supply of phosphorus in most soils is low and is not readily available for plant use. This low amount of phosphorus in soil reflects the characters of soil to permit the plant to grow in a particular area and determine the vegetational type of the area. Saxena and Singh (1980) reported poor availability of phosphorus under open grasslands as compared to the soils under tree cover, nevertheless in the present study higher phosphorus values were recorded on the moraine sites where tree canopy was absent. Phosphorus controls the distribution of vegetational types and organic matter production of soils. The increase in soil organic carbon increased the nitrogen and expansion in phosphorus added the soil potassium. Bawa (1992) through his study of phosphorus as an indicator of pedogenesis of soils concluded that the relative magnitude of predistribution within the profile is a function of degree of soil development. Grasses accumulates more phosphorus. Higher concentration of phosphorus was due to the presence of grasses at alpines sites (July-September) than the moraine sites.
The availability of potassium in Indian soils was studied by Raychaudhary et al. (1963). They reported that the soils rich in mica have a high potassium fixing capacity but organic matter contents reduce its amount. Potassium in soils showed a decreased trend in soil profile because of maximum exchange of potassium between plant and soil. Maximum concentration of potassium was found at AS1 and AS2 than the moraine sites (MS1 and MS2). Basumatary and Bardoloi (1992) observed that higher values of potassium in lateritic soils are due to weathering of potash bearing minerals and release of soluble potassium from insoluble compounds. Leaching and running off as a result of destruction of vegetation may cause the decrease of potassium. Losses of organic matter and nutrients were due to erosion, leaching and volatilization (Menaut et al., 1993).
Overall, moraine soil was much more acidic than the alpine. Soil of the alpine was rich in nutrients as compared to the moraine. Organic carbon percentage was found to be greater in the alpine sites ranging from 3.8 to 4.7 in the top 30 cm whereas it ranged from 1.3 to 2.6 in moraine. Nitrogen, Phosphorus and Potassium percentage was also found to be higher in the alpine than the moraine. Thus, the alpine sites had maximum number of species than the moraine sites. Soil needs optimum amounts of organic matter to maintain its structure and keep it in a tillable condition. The soil organic matter and the humus decay are the important components in assessing and maintaining the productivity of the soils.
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