Study site

The study was carried out in 2 communities, Chepplung and Monjo, in the buffer zone area of Sagarmatha National Park, Nepal. Both study sites are located in the Chaurikharka village development committee and are the main settlement areas of this region with fertile agriculture land (Figure 1). They lie in the eastern mountainous region of Nepal, between 27°42′09″ and 27°46′23″N and 86°42′51″ and 86°43′28″E, with an altitude of 2600–3200 masl. The Red Panda Community Forest in Chepplung has a mixed broadleaved forest, dominated by Quercus semecarpifolia Sm. and Rhododendron arboreum Roxb. as overstory. Other codominant species are Eurya acuminata DC, Ilex dipyrena Wall., Lyonia ovalifolia (Wall.) Drude, and Sorbus cuspidata (Spach) Hedl. The shrub layer is mainly dominated by Pieris formosa (Wall.) D. Don and Rhododendron lepidotum Wall. ex G. Don. The Himalaya Community Forest in Monjo is dominated by Pinus wallichiana A. B. Jacks and Q. semecarpifolia Sm. as overstory. Understory vegetation includes L. ovalifolia (Wall.) Drude and R. arboreum Roxb. The shrub layer is dominated by P. formosa (Wallich) D. Don, Rhododendron spp, and Rosa spp.

FIGURE 1

Location of the study communities of Monjo (Himalaya Community Forest) and Chepplung (Red Panda Community Forest) in the buffer zone of Sagarmatha National Park, Nepal. (Map by Mr Yogendra Karna)

The soils at the study sites are mainly developed from glacial, fluvioglacial, and fluvial deposits and are generally well drained. The soil south of Lukla (near Chepplung) has highly weathered brown clays, developed from numerous stratified fluvioglacial sediments (migmatites). Low clay content is found in the lower soil profile. The stones in the soil profile show thick weathering crusts. Around Monjo, podzols are found, which are developed from coarse–blocky migmatitic debris (Bäumler et al 1991). The mean annual rainfall is 2076 mm, and the mean annual minimum and maximum temperatures are −0.1 and 18.2°C (rainfall data were provided by the Department of Hydrology and Meteorology, Government of Nepal, and temperature data were provided by the Ev-K2-CNR–SHARE Project, Italy). The main rainy season lasts from mid-June to September, with most of the annual precipitation occurring during this time.

Traditional land use practices are the basic livelihood options of the studied communities and are categorized as kitchen vegetable garden, bari (highland rainfed agricultural) land, and forest. The choice of crops depends on demand, land size, and the interests of the household. The yield of crops is affected by weather conditions and differs from year to year and land parcel to land parcel. In both study villages, potato is the main crop, grown on 70% of the total agricultural land. Maize, wheat, and oats are grown in a small area (0.1–0.2 ha) and considered secondary crops. Other common crops are barley and vegetables such as radishes, carrots, cabbage, and beans. Potatoes and beans are usually intercropped and are grown on bari land, whereas vegetables are grown in kitchen gardens located near the houses.

The mean family size is 4.2; landholdings range from 0.5 ha to 1.5 ha. Farmyard manure (FYM) and humanure are the main fertilizers applied to agriculture land. The availability of both is declining because of a rapid decrease in the livestock population and the introduction of modern toilets.

The main livestock are yak, nak (female yak), cows, bulls, jopkyo (a cross breed of yak and cattle), and horses. Goat farming has been banned by the park in consultation with the local communities since 1980. Cows and jopkyo are mostly kept in the homesteads; yak and horses are always kept in highland pastures above 4000 m. Local tradition holds that these animals could not withstand the warmer climate and limited availability of nutritious wild grasses below 3000 m. When the tourist season starts, these animals are brought to the lower elevation to carry loads. Even then, herders prefer to feed yak and horses with dried alpine wild grasses. These grasses are cut and dried carefully and transported to the main settlements along the main trekking routes in Sagarmatha National Park (Lukla, Monjo, Phakding, Namche Bajar, Khumjung, and Tangboche) before the start of the tourist season. For this study, household manure production and fodder requirements were calculated based only on the number of livestock kept in the homestead.

Calculation of the C and N pool

The sampling was done using 3 nested circular plots for vegetation (trees, saplings, and shrubs) and nested square plots for litter and ground vegetation. Trees with <5 cm diameter at breast height (Dbh) and >1.3 m height were measured within a radius of 2.5 m; trees with 5–10 cm Dbh and height >1.3 m were measured within a radius of 5 m; and trees >10 cm Dbh and height >1.3 cm were measured within a radius of 10 m. Density and basal area of plants were calculated. Allometric functions (Yoda 1968; Chaturvedi and Singh 1987; Adhikari et al 1995; Garkoti and Singh 1992; Sharma and Pukkala 1990) were used to calculate tree biomass. Shrubs were harvested from 2.5-m-radius circular plots to estimate biomass. Ground vegetation and organic material were collected from 5 square subplots (1 × 1 m) within the main circular plots. The fresh weights of shrubs, ground vegetation, and organic materials within the plots were recorded, and subsamples were taken to the laboratory for dry weight estimation.

Calculation of C and N flux

The community forests in the study sites were divided into blocks with defined areas separated by prominent features such as streams, ridges, forest borders, and trails. Most of the forest resources were collected from these blocks, as they are near the villages. The boundary coordinates of the collection area were obtained using a Garmin eTrek GPS and were imported into ArcGIS (9.3.1) for the calculation of total source area used for the collection of fodder, fuelwood, and litter.

Questionnaire survey

Semistructured questionnaires were used to interview approximately 25% of the total households in each village (Martin 1995): 15 in Chepplung and 16 in Monjo. The field survey was carried out from March to September 2010 to gather data on family size, number of domestic animals, fuelwood consumption, grazing patterns, litter needed for animal bedding, application of FYM, source area for collection, and crop yield.

Estimation of fuelwood and fodder requirements

Fuelwood and fodder requirements in each household were estimated in 2 ways: by interviewing the households, and by verifying the information provided by each household by measuring the amount of fuelwood and fodder required per day.

Estimation of C and N sources

Laboratory analysis

Analytical procedures conformed to Austrian Standards Institute (2010). Samples of parts of trees (foliage, bole, branches), shrubs, herbs, organic matter, fodder, FYM, fuelwood, and crops were taken to the laboratory and oven dried at 80°C until the mass was constant for dry weight estimation. Oven-dried samples were ground for the analysis of C and N content, which was determined using a Leco TruSpecCN analyzer (Leco Corp, St Joseph, MI, USA). The analysis involved dry combustion at 1400°C in a pure oxygen atmosphere and infrared detection of evolved carbon dioxide and thermal conductivity detection of nitrogen oxide. The resulting C and N values were used for the calculation of C and N stocks and fluxes.

Statistical analysis

Analysis of data was carried out by using Microsoft Excel and SPSS (version 15).

Forest condition

In Chepplung (Red Panda Community Forest), 13 tree species were recorded, with a total tree density of 576 ± 97 individuals ha⁻¹ and total basal area of 31.0 ± 6.5 m² ha⁻¹. Q. semecarpifolia Sm. had a maximum density of 300 ± 57 individuals ha⁻¹ and basal area of 20.45 m² ha⁻¹. Another dominant species, R. arboreum Roxb., had a density of 159 ± 37 individuals ha⁻¹ and basal area of 7.7 ± 3.2 m² ha⁻¹. Q. semecarpifolia Sm. and R. arboreum Roxb. are mostly used for fuelwood, whereas the leaves and twigs of Q. semecarpifolia Sm., E. acuminata DC, and I. dipyrena Wall. are mostly used for fodder.

Seven tree species were recorded in Monjo (Himalaya Community Forest). The total density of plant species found in this forest was 465 ± 155 individuals ha⁻¹, and basal area was 18.8 ± 5.9 m² ha⁻¹. P. wallichiana A. B. Jacks contributed the maximum density and basal area (394 ± 76 individuals ha⁻¹ and 15 ± 4.2 m² ha⁻¹). P. wallichiana A. B. Jacks and L. ovalifolia (Wall.) Drude are mostly used for fuelwood. Leaves and twigs of Q. semecarpifolia Sm. is used as fodder.

C and N pools

In Chepplung (Red Panda Community Forest), the total vegetation C and N pools were 47.6 ± 12.5 Mg ha⁻¹ and 274.3 ± 64.7 kg ha⁻¹, respectively, whereas the organic layer stock had 1.0 ± 0.1 Mg ha⁻¹ of C and 30 ± 0.4 kg ha⁻¹ of N. Q. semecarpifolia Sm. alone comprised more than 50% of the total C and N stocks (C 32 ± 8.2 Mg ha⁻¹, N 132 ± 34.1 kg ha⁻¹), followed by R. arboreum Roxb. (C 10.7 ± 2.9 Mg ha⁻¹, N 79.1 ± 19.5 kg ha⁻¹). Monjo (Himalaya Community Forest) recorded 60.5 ± 14.1 Mg ha⁻¹ of C and 431.3 ± 112.1 kg ha⁻¹ of N in the vegetation layer, whereas the organic layer contained 1.1 ± 0.2 Mg ha⁻¹ of C and 30 ± 0.3 kg ha⁻¹ of N. Of the total C and N stocks, P. wallichiana A. B. Jacks contributed more than 80% (C 58.2 ± 13.9, N 403 ± 109.5 kg ha⁻¹). No trees were recorded in the agricultural plots for the estimation of vegetation C and N stocks.

C and N fluxes from the forest

Annual fuelwood C and N fluxes from the forests to the households were in the magnitude of 1.1–1.2 Mg ha⁻¹ C and 18.4–20 kg ha⁻¹ N. Litter collection transports 0.27–0.34 Mg ha⁻¹ C and 7.4–10.6 kg ha⁻¹ N from the forest; fodder collection accounts for 0.19–0.2 Mg ha⁻¹ C and 6.2–6.4 kg ha⁻¹ N.

Livestock is a major asset and plays a vital role in maintaining the fertility of agricultural land. About four fifths of the households keep livestock for subsistence farming. The livestock ownership pattern is influenced by occupation and farm size. Local people who are involved in tourism and have larger farms keep more livestock. Cows and jopkyo are mostly kept in the homestead, whereas yak are always kept in the highland pastures.

Almost every household obtained fodder, fuelwood, and litter from the forest. The community forests in the study sites are protected and managed by the buffer zone community forest user groups. The resources of the community forests are provided to local users based on an operational plan under which the forest is open throughout the year for grazing and the collection of litter and fodder. Firewood collection is limited to two 15-day periods a year, and only fallen trees and branches can be collected. Each household allocates 2–3 people for the collection, which is carried out 2–3 times a day.

Fodder

Both agricultural and forest land provide fodder for livestock. Livestock feeding in the homestead depends mostly on the season. In summer, the soil is dry and the ground vegetation ceases growing; hence, trees and crop residues are the main fodder sources. The postmonsoon period allows herbs, grasses, and shrubs to flourish and supply fodder to cattle. Autumn (July–August) is the main season for potato field grazing. Leaves of Q. semecarpifolia Sm. are the preferred fodder, followed by I. dipyrena Wall., E. acuminata DC, and grasses. Agriculture residues (wheat, oats, and maize) are dried and stored for use as fodder during the dry season.

The average amount of fodder collected annually from the forest was 75–95 bharis, which amounted to 1500–1900 kg of fresh fodder. Annual transports of C and N amounted to about 578–750 kg C and 19.5–24.2 kg N from forest land (through grazing and tree fodder) and 203–257 kg C and 3–3.5 kg N from agricultural land (through straw and potato field grazing). Stall-feed fodder contained 535–670 kg C and 14.5–17.3 kg N per household annually (Table 1).

TABLE 1

Total fodder, carbon, and nitrogen supplied annually from the forest and agricultural land to the household.^a)

Application of FYM

The average annual fresh FYM input in agricultural land was 3.7–4.1 Mg ha⁻¹ (Table 2). Applications vary according to crop types. Whereas highest amounts are applied to vegetables, potatoes, and wheat, maize and barley are grown on residual soil fertility, with FYM added once every 3–4 years.

TABLE 2

C and N inputs to agricultural land from FYM.

Both animal and human wastes are used. Annual fresh manure production from livestock was 4–5.4 Mg per household, and annual fluxes of C and N to agricultural land were 293–400 kg C and 10–14 kg N per household. Additional fertilizer came from traditional toilets (sotaar charpi), in which the waste is covered by leaf litter and, after 8–10 months, is used as compost, especially in the potato fields. The approximate dry weight of human waste produced annually per household is 0.13 Mg, which accounts for 0.09 Mg C and 9 kg N.

C and N produced by crops

Agricultural land produced 1.8–1.9 Mg ha⁻¹ C and 49.4–52.2 kg ha⁻¹ N annually, of which about 58% of C and 68% of N were transported to the households through crops, and about 14% of C and 6% of N through crop residues. The remaining C and N were left behind as potato residues, which decompose and add nutrients to the soil.

C and N flow between households and fields

The total annual requirement for animal fodder was 781–1007 kg ha⁻¹ C and 22.5–27.8 kg ha⁻¹ N. Of this, 73–74% of C and 86–88% of N were provided by tree fodder and forest grazing, and 26–27% of C and 14–15% of N by crop residues. Another pathway of C and N flow from household to agricultural land was through livestock manure (293–400 kg C, 10–14 kg N). A major proportion of C (58–64%) and N (54–47%) was provided by bedding material. Annual fluxes from agricultural land to household (hh) were 1061–1142 kg ha⁻¹ C and 33–35.7 kg ha⁻¹ N from crops, and 203–257 kg hh⁻¹ C and 3–3.5 kg hh⁻¹ N from crop residues and grazing in agricultural fields. A large proportion of the C and N added annually to agricultural land came from crop residues (538–552 kg C and 13.5–14 kg N per household); smaller amounts of N were provided by human waste (9 kg N per household). In general, 1400–1490 kg C and 52–54 kg N from various household sources were applied to agricultural land each year. Figures 2 and 3 provide an overview of C and N flows between household and agricultural land.

FIGURE 2

Annual carbon flow (t ha⁻¹) in high mountain communities in Nepal. Rectangles represent sources and sinks, arrows represent flows within the community area. No estimates are available for input rates to and output rates from the systems (eg photosynthesis, decomposition, sediment transport).

FIGURE 3

Annual nitrogen flow (kg ha⁻¹) in high mountain communities in Nepal. Rectangles represent sources and sinks; arrows represent flows within the community area. No estimates are available for input rates to and output rates from the systems (eg nitrogen fixation, leaching and denitrification, sediment transport).

Fuelwood use

The study sites are in the Himalayan region and are situated along one of the most popular trekking routes and gateways to Mt Everest. Because of this, household consumption of fuelwood depends on the season. An increase in the number of tourists increases total fuelwood demands proportionally. The present values are higher than those reported from the Himalayan region of western Nepal (11.6 kg hh⁻¹ d⁻¹; Metz 1994) and Manang, Nepal (5.89 kg hh⁻¹ d⁻¹; Karky 2008) and within the range reported from the eastern Himalaya region in India (11–13 kg hh⁻¹ d⁻¹; Bhattacharya and Joshi 2001); Uttarakhanda, India (13 kg hh⁻¹ d⁻¹; Sati and Song 2012); high-altitude villages of India (11.6–13.1 kg hh⁻¹ d⁻¹; Sharma et al 2009); and Suhelwa Wildlife Sanctuary, Uttar Pradesh, India (14.2 kg hh⁻¹ d⁻¹; Jaiswal and Bhattacharya 2013).

The lower fuelwood consumption rates reported by various authors could be due to the fact that those areas are not important tourist destinations, or to the socioeconomic condition of the people, their occupations, weather conditions, household size, or access to other energy sources (such as kerosene and liquid petroleum gas). However, the fuelwood extraction data obtained in the present study fall within the lower range provided by Singh and Rawat (2012) for the western Himalaya region of India (30 kg hh⁻¹ d⁻¹) and Awasthi et al (2003) for Garwal Himalaya (35 kg hh⁻¹ d⁻¹). The values recorded during the tourist season are in the range reported for Garwal Himalaya (20 to 25 kg hh⁻¹ d⁻¹) (Singh et al 2010) and for Dhikoli village in the high-altitude area of India (24.6 kg hh⁻¹ d⁻¹) (Sharma et al 2009). In comparison, according to forest user groups, a decrease in fuelwood consumption during winter (December–March) could be due to the migration of households involved in tourism to lower altitudes, mostly to Kathmandu Valley.

Household fodder requirements

Annual fodder consumption in both communities was 1.3 ± 0.4 Mg LSU⁻¹ (dry weight), of which 44–45% was contributed by forest resources (tree leaves), followed by forest grazing (28–29%) and agricultural residues (26–27%). These consumption data are close to the range reported by Mahat (1987) (1.2 Mg LSU⁻¹ dry weight per year) for the midhill region of Nepal for all fodder categories (stall-fed and grazed).

In Kavre Palanchok, Nepal, grass contributed 64% of fodder, followed by tree leaves (20%) and agricultural residues (15%) (Mahat et al 1987a). In Sindhu Palchok, Nepal, 28% of total fodder was obtained from the forest and 13% from grazing (Mahat et al 1987b). Fox (1984) estimated that in central Nepal, 66% of fodder was derived from agricultural residues, 24% from grass, and 10% from tree leaves. Metz (1994) estimated that in Chimkhola, western Nepal, 70% of fodder was obtained by grazing and browsing. Bajracharya (1999) reported that 30–50% of fodder was derived from forests and grasslands. The higher proportion of both grass and tree fodder found by the present study could be due to the smaller amount of agricultural land, agricultural residues, and fodder trees in the study areas.

C and N balance

The rate of application of FYM depends on farmers' perceptions about the importance of crops and FYM availability. Dry FYM applied to agricultural land per household per year was 2.1–2.2 Mg, which falls within the lower range (1–31 Mg) calculated by Vaidya (1988) for different categories of agricultural land and crops. The lower application of FYM could be due to the fresh/dry factor used for calculations. However, the application of FYM in the bari (highland rainfed agricultural land) is consistent with the finding of Pilbeam et al (2000) about bari potato fields in the midhill regions of Nepal (3.9 Mg ha⁻¹ of fresh FYM per year).

This study found that approximately 39–40 kg N ha⁻¹ was applied to the arable land as FYM each year. Additional soil nutrients came from crop residue, which supplied about one third of the FYM. Subedi et al (1996) estimated that 25–100 kg N ha⁻¹ was applied annually to arable land in midhill regions. Pilbeam et al (2000) stated that 1 ha of land (two-thirds rainfed hillside and one-third irrigated lowland) would be in balance with inputs of 26 kg ha⁻¹ N per year.

Homesteads in the study areas had fewer LSUs than those in other Himalayan and midhill regions of Nepal. But the application of N to agricultural land was still within the range given by various authors (Subedi et al 1996; Pilbeam et al 2000). This could be due to the addition of N from human waste and crop residues. Calculations indicated that if human waste were removed from the annual inputs, N would be reduced by the equivalent of 9 kg per household per year. This accounts for 19% of the annual N requirement of agricultural land, which means there would be a reduction in the total N produced in crops and vegetables of 18 kg per household.

It is calculated that to maintain the present fertility of the arable land, each household would require 2–5 hectares of forest land. It is obvious that an increase in the demand for litter, fuelwood, and fodder would increase the C and N fluxes from the forest. This might cause forest degradation, soil acidification, changes in vegetation structure, and negative impacts on regeneration. On the other hand, these forest resources are important to local livelihoods. A decrease in the supply of livestock feed and litter would decrease the production of FYM, which might affect the fertility and productivity of agricultural land. A decrease in soil fertility would in turn cause food scarcity in such areas if no other food sources were available.