Study Area
Pauri Garhwal, a district in the state of Uttarakhand, in Western Himalayan region encompasses an area of 5230 km2 and is situated between 29°45’ and 30°15’ N, 78°24’ to 79°23’ E with sub-tropical to temperate climate. Monthly minimum and maximum temperature in the study area ranged between 6–21°C and 18–35°C, respectively, with mean annual rainfall of 1500 mm, while the soil is derived from weathering of slate down to 30–80 cm deep. The main occupation of the local inhabitants is farming, while other major sources of employment for young people are armed forces and teaching. Due to the lack of infrastructure and geography of the area, there are no major industries in the hilly part of the district (MSME 2016).
The present study was carried out in two villages i.e., Manjgaon (29°54’54.2’‘N, 78°52’27.8’‘E; 1500 m above mean sea level (a.m.s.l.) and Mald Bada (29°55’04.8’‘N, 078°52’43.7’‘E; longitude at 1534 m a.m.s.l.) in Pauri Garhwal district (Figure 1). In each village, two sites i.e., agricultural land (site A) and a fallow land(site B) were studied.
The inhabitants of both villages depend on forest and agricultural resources, such as fuel wood for cooking and fodder for livestock to fulfil their basic needs. Common trees growing along the edges of agricultural fields were Bauhinia variegata, Celtis australis, Ficus roxburghii, Ficus palmata, Grewia optiva, Prunus cerasoides, Pistacia integerrima, Quercus leucotrichophora, Sapium insigne and Toona ciliata. The fallow land around the village was earlier agricultural land, left due inadequate irrigation facility and monkey problem. Fallow land consist of various multi-purpose trees such as Quercus leucotrichophora (Banj oak), Celtis australis (khadik), Pinus roxburghii (chir), Prunus cerasoides (padam/payya), Ficus roxburghii (timla), Ficus palmate (bedu), Bauhinia variegata (kweral), Sapium insigne (khinnu) and Pistacia integerrima (kakhad), of which Celis australis, Prunus cerasoides, Pinus roxburghii and Quercus leucotrichophora are the most common species, while Berberis asiatica (kingora), Rhus parviflora (tung), Woodfordia fruticosa (dhaula) and Rubus ellipticus (hisalu) are the most common shrub species in the forested area.
Data collection
Collection of primary data was carried out using a pre-tested semi-structured questionnaire was framed based on reviewed literature, previous knowledge, a pilot survey and peer discussions during 2011–2012. The questionnaire included a mix of questions pertaining to the issue under investigation, with the majority being closed-ended questions. The information was collected by personal visit to the study area and discussion with respondents (local inhabitants) with their prior oral consent. The responses to the questionnaire provided data on household attributes, crops grown and factors responsible for biomass extraction. The interviews and discussions with peers and locals (mainly elderly people and women) lasted for one hour and were conducted in Hindi as well as local dialect (Garhwali).
Biomass estimation
The aboveground biomass was calculated using existing volume regression equations for Toona ciliata, Quercus leucotrichophora and Bauhinia variegate (Table 1) (FSI 1996; FSI 2015).The aboveground biomass values for remaining tree species such as Celtis australis, Ficus palmata, Ficus roxburghii, Grewia optiva, Sapium insigne, Pistacia integerrima and Prunus cerasoides were estimated using the formula for standing trees, with the results expressed in m3(Chaturvedi and Khanna 1982). The diameter at breast height was measured with a calliper and tree height with a Ravi multimeter.
Calculation of aboveground biomass for remaining species was as follows:
The basal area(Ab) of merchantable bole was estimated as:
Ab = πd2/4
Where,π = 3.14 and d is the diameter of the tree at breast height.
The volume (V) in m3was calculated as:
V = Ab×H×BEF
Where, H is tree height and BEF is biomass expansion factor used in an Indian context (value 1.575; Kishwan et al. 2009).
Using mean wood density (MWD)of each species, total biomass was calculated in metric tonnes (Rajput et al. 1996). The MWD value of 0.72 was used for species for which the exact MWD was not known (Kaul et al. 2009). The calculated volume of the trunk was used to estimate total trunk biomass (kg) by multiplying with wood density (WD) for the corresponding tree species following Brown (1997):
Biomass = V×WD×1000
Assessment of Carbon Stocks
To estimate the carbon content of trees in the study area and total biomass extraction, samples of wood were taken from felled trees of the different species. The ash content method was used to estimate carbon content following Negi et al. (2003), due to its simplicity and the availability of resources such as equipment and research expertise. Twenty samples were taken from each tree species and ground into powder using an electric pestle mortar. The powder samples were sieved and oven-dried to constant weight and then a 2g sub-sample of each was transferred to an uncovered crucible, which was placed in a muffle furnace and heated at 575 ± 25°C for 3 hrs to eliminate the carbon. The crucibles were then placed in desiccators for cooling, to avoid moisture absorption (Ehrman 1994). Finally, the weight of ash was measured after the crucibles has attained room temperature and carbon content (%) of the original sample was calculated following Negi et al. (2003):
Carbon % = 100-[Ash Weight+MolecularWeightof O253.3in C6]
Carbon (C) = Biomass×Carbon %
Carbon Sequestration = Carbon×3.666