1. An area that had been historically deforested
2. A highly visible area (to achieve greening of degraded land)
3. Relative difficulty of establishing trees using conventional planting methods (such that the DFS would not normally attempt such a project) and
4. A desire to have a high profile project area (along a major route)

These criteria resulted in the choice of a site between Paro, where the only civil airport in Bhutan is located (Paro District), and Thimpu, the capital of Bhutan (Thimpu District). The site, Isuna, is one kilometre south of an old DFS nursery and lies on both sides of a steep valley, best described as almost ravine like, through which the main Paro-Thimpu road passes. Envirotrade had noted the Paro-Thimpu Valley on a previous visit to Bhutan , as a potential area for afforestation due to the very visible and significant areas of degraded land.

Site characteristics 

The site is located within Paro District, some 10 kilometres south east of Paro, and lies at approximately 2,500m asl and is in the inner Himalayan Zone. The climate may be characterised as cool temperate, with annual rainfall of between 650-850mm and temperatures ranging from 1.0 to 26 degrees Celsius (mean 13 degrees C).
The soils are shallow (up to 30cm in depth) and are sandy in character and the site is north easterly and south westerly in aspect (both sides of the valley). It falls within the Blue pine (Pinus wallichiana) vegetation zone (from Roder et al., 2001), which is assumed to be within 2,100 to 3,000m asl. The northeasterly facing slopes have a covering of low shrubs (Berberis ) and the southwesterly facing slopes have tussocky grass cover.

Site visit

The site was visited on two occasions, with the Forest Officer for Paro District, the Forest Ranger for the district, the DFS representative from Thimpu (Head of Policy Unit) and representatives from Namsay Consulting and Envirotrade.
During the first site visit basic site details were noted. The slopes are moderate to steep with sparse ground vegetation. This latter observation may change during summer (monsoon) months, however the grass cover was patchy and does not appear to grow to much more than 50cm in height. Erosion and soil loss would appear to be a problem on the steep valley sides and loss of tree cover would appear to have taken place more than 50 years ago. The DFS have Plantation Record Journals, which record site characteristics and operations. The Paro District log alluded to repeated burning, grazing and the felling of remnant Blue pine stands in the past 30-50 years. Historical information is difficult to come by but it would appear that much forest loss and degradation in the Paro-Thimpu Valley has occurred over the last 200 years.

The second site visit established that the soils were structurally- and nutrient-poor valley brown earths with little water retention capacity. The sites are also characterised by rocky outcrops and by a high percentage of stones in soil profiles. This finding means that future tree establishment would be challenging and would require labour intensive techniques. The north easterly facing slope had been subject to a previous afforestation attempt, with large willow poles (cuttings) having dramatically failed to establish. This attempt was followed by a further planting scheme using small (slip) willow cuttings, which had also failed.

The Paro District Forest Officer showed tree establishment on an adjacent site extending to approximately 100 hectares, which had been planted some ten years previously using a mixture of Blue and Chir pine (Pinus roxburghii). Other species such as Quercus griffithi were used in this plantation but less than a dozen or so individuals appeared to have survived. The planted Chir pine had responded well to the drought-prone nutrient poor soils and many individuals are +2.5 meters in height, with subsequent provision of shelter for the more wind sensitive (apparently) Blue pine. This planting of Chir pine out with its natural zonation and in a valley that does not contain many naturally regenerating Chir pine does not present any biodiversity issues and it’s resilience to drought conditions and a tolerance of exposure make it ideal for the Isuna site.

Tree species

The use of Chir and Blue pine in mixture was readily accepted by the DFS as the best course of action in attempting to establish forest cover on this site. Healthy seedlings of these species and the local oak species were observed in a Forest Development Corporation Nursery on the outskirts of Paro. It was felt that planting small quantities of Quercus griffithi was desirable from a biodiversity and demonstration project standpoint.

Blue pine and chir pine forests are two of the major forest types in Bhutan . They occur in the temperate regions of the inner Himalayas , with an average rainfall of around 1,000 mm.
Chir pine forests extend from around 900 to 1,800 masl, in the warm temperate zone of Bhutan . Chir pine predominates in the deep dry valleys of Puna Tsang Chhu, Kuri Chhu and Kulong/Dangmechhu river systems. The climate is a highly seasonal monsoon climate, with a long dry season. Chir pine generally reaches around 55 m in height. The Chir pine zone represents the most heavily affected forest zone in the Himalayas with cultivation, grazing and burning. In Bhutan this is best illustrated in the Districts of Wangue–Phodrang and Punakha.

Blue pine forests occur at cooler, higher altitudes, in the valleys and foothills between 1,800 to 3,000 masl. Blue pine prefers sandy, well-drained soils and can be found either in pure stands or in association with Quercus, Acer and Ilex species. Blue pine can reach heights of 30-50m.
Quercus griffithi is a large deciduous tree is a moderate light demander and regenerates where grazing browsing and burning are excluded.

Forest establishment

The land is owned by the RGoB but is used by itinerant (allegedly) villagers, who have a settlement at a higher elevation, above the site, and who are said to be residents of Paro and Thimpu, who use the land and settlement at weekends and during the summer months.
The biggest impediments to tree establishment on this site are grazing, burning and drought.
The area is used for traditional grazing, predominantly cattle at lower elevations, and it is apparent that repeated heavy grazing has prevented the regeneration of Blue pine. Where grazing is excluded from an area Blue pine can, depending on the proximity of seed trees, re-establish. The problem of overgrazing is a national problem with cattle numbers far exceeding the carrying capacity of the land (Ministry of Agriculture [1996b] Sustainable Land Use-Guidelines for Bhutan, Vol. II.).

The forest project would have to negotiate with traditional users (to establish cattle movement routes) and to explain the requirements for stock exclusion, fire prevention and maintenance of fencing. Loss of grazing may be offset by employment within the forest project and subsequent use of timber, from thinning. The DFS need to start negotiations with the local community to establish a rapport in respect of this project and to try to engage and involve the villagers in its design and execution.

The climate is seasonal, with the monsoon bringing high precipitation between June and September and a long dry period between October and May. Because of the extensive land degradation and soil depletion, steep sided sites with sandy soils containing little organic matter are susceptible to erosion and to drought. The method of establishing trees should be hand dug pits. Ideally these should be 2 feet by 2 feet in surface area and approximately 1 foot in depth. The tree seedling should have leaf litter mulch packed round it before covering with soil. The leaf litter mulch will provide water retention capacity and a limited source of nutrients. Training of planting labour is essential to the establishment of planted trees.
Biomass yield and forest increment

Data from the FAO (Food and Agriculture Organization of the United Nations) publication Forest Resources of Bhutan, 2000a Working Paper No. 18 suggests that Bhutanese forests contain 163 cubic metres per hectare volume, equivalent to 178 tonnes per hectare of biomass. This is a country average that is approximately one and a half times the world average.

The growth rates for pine forests in Bhutan are reported to be relatively low. The local timber yield for Blue pine stands on marginal sites, under management in Forest Management Units (FMUs) is reported by the DFS to be approximately 330 cubic metres per hectare. The rotation period for these forests is between 90-100 years, giving an approximate Mean Annual Increment (MAI) of 3-4 cubic metres per hectare per annum. This is a low growth rate and probably best mirrors the potential productivity of the Isuna site. Changes to site productivity may occur with canopy closure, when leaf litter will begin to accumulate and water retention is enhanced.

Yield tables for Scots pine (Pinus sylvestris L.), a species with relatively similar growth characteristics to local pines, provide yield curves for a variety of growth rates and management regimes, and theses are used to provide proxy data for this site. The output of these models is illustrated in Figure 1. This proxy data can be refined as yield information is obtained from the Indian Forest Service Yield Tables and this in turn can be fed into ECCM models.

Changes in carbon stocks over 100 years for Scots pine, mean annual increment 4 m3 yr-1, using the ECCM Model v3.1

The figures for carbon uptake when soil carbon is included show an increase in carbon stocks of approximately 35-40 tonnes per hectare. The inclusion of soil carbon in carbon calculations is becuase the Isuna site possesses soils of such poor quality and negligible organic content that it appears valid to include them in any carbon sale.