Growth, Biomass and Carbon Sequestration Potential of Broad Leaf Forest in North-West Himalayas

The Himalayan forest’s vegetation varies from timberline to tropical dry deciduous woodlands on the slopes. Forests are the primary source of income for individuals living in the Himalayan foothills. The mid-hill forest is dominated by P. roxburghii and Q. leucotrichophora. Temperate forests of the Western and Central Himalaya range in elevation from 1200 to 3000 metres above sea level and are distinguished by large oak and coniferous woods (Kumar and Bhatt, 2006). The peasants rely heavily on Q. leucotrichophora for fuel, fodder and other necessities. Because it is primarily used for fuel, fodder and small timber, oak is the most preferred tree species in the temperate region. Without a doubt, forests are the primary land-based CO₂ sinks (Houghton et al., 2001). Forest ecosystems are crucial to regional and global terrestrial carbon cycles because they store a lot of carbon in vegetation, detritus and soil and exchange a lot of carbon with the atmosphere through respiration and photosynthesis. Since carbon makes up over half of the dry biomass weight of a forest, the amount of carbon that the forest sequesters (or loses) can be estimated from biomass accumulation (FAO, 2005). 
       
Forests play a vital role in regulating the global carbon balance. Increased forest biomass promotes atmospheric carbon sequestration, whereas decreased forest biomass adds to CO₂ emissions. To calculate the entire carbon content stored in a forest ecosystem, the aboveground biomass content must be estimated. As trees get bigger and their biomass rises, they take in more carbon from the environment and store it in their tissues, which causes different portions to develop (Matthews et al., 2000). When forests are managed to fulfil emission objectives, the quantity of carbon that may be emitted to the atmosphere or sequestered on the land is determined by the amount of biomass in the forest. The assumption that 50% of biomass contains carbon (on a dry weight basis) is widely accepted (Hamburg, 2000; Brown, 2001).          
       
SOC dynamics and carbon flow are greatly influenced by land use and soil management practises (Tian et al., 2002 and Rasse et al., 2006). According to Brown (1997), roughly 50% of tree biomass is carbon. However, these ecosystems are increasingly threatened by anthropogenic pressures such as deforestation, land-use change, grazing and the impacts of climate variability. The forest and agro-forestry ecosystem contribute significantly to carbon cycling and helps to mitigate climate change because it is dominated by perennial vegetation, which has a larger capacity to store carbon (Sarkar et al., 2021; Nthebere et al., 2022; Jayara et al., 2023 and Namitha et al., 2025). Nonetheless, the dynamics of nutrients in the terrestrial ecosystem were altered by increasing urbanization and human activities (loss of biodiversity, altered land use, degradation of forests and deforestation). It is impossible to undervalue the contribution that trees outside of forests provide to improving lifestyles and providing ecological benefits.
               
The main objective of this study is to estimate tree biomass and carbon sequestration rates in broadleaf forests. Data were based on tree species measurements in broadleaf forests collected in the years 2020-21 and 2021-22. Forests play an important role in development, livelihoods and climate. They provide wood and non-wood products and agricultural tools to mountain people, as well as improving soil fertility and controlling erosion. The forest composition in the mountain area varies according to altitude, climate, aspect, slope and soil characteristics. 

Study area
 
The current investigation was carried out in the broadleaf forest of Solan district in Himachal Pradesh. The region is bounded by latitudes of 30°50'30" N-30°52'0" N and longitudes of 77°8'30" E-77°11'30" E. The study was conducted from 2020-21 and 202-22. The soil is gravel, sandy with loam texture and it is classified as an inceptisols. The research area was split into five replicates of 10 × 10 m each. All of the trees in each replication were chosen and counted. Each replication had all of the trees picked and counted. In total, 41 trees from the broad leaf forest were chosen. Bauhinia variegata, Grewia optiva, Pinus roxburghii, Toona ciliata and Quercus leucotricophora were the tree species.
 
Biomass estimation of tree species
 
Five sample plots (10 × 10 m) were established in the broadleaf forest and diameter at breast height (DBH at 1.37 m) was measured for every standing tree (Feldpausch et al., 2011) in the sample plots (total 41 trees). Growth and above ground biomass of trees falling in these sample plots were enumerated. All trees were counted in order to calculate height, clear bole, crown spread, crown length and crown index. Diameter at breast height (dbh), crown length and crown diameter were measured with measuring tape. Total height of the tree was measured using Clinometer. The crown spread was established for each tree by measuring the length and breadth of the crown. The area (LxB) to first place of decimal was taken as the crown spread. Crown length is the height of the tree up to the point where the crown branches started was measured and subtracted from the actual height of the tree to know crown length of a tree. Crown Index is the ratio of crown length to the crown width (crown spread).

 
The allometric volume equations approach was used to determine the biomass of the trees.  The biomass of tree species was determined by measuring their diameter and height and applying the volumetric formulae provided by the Forest Survey of India (FSI, 1996), as shown in Table 1. Above ground biomass of tree species was estimated using following equation: 
     

AGB= Volume × Specific gravity

 
       
Below ground biomass of tree sp. present in broad leaf forest was estimated by multiplying aboveground biomass with a factor of 0.26 (IPCC, 2003). Total biomass per tree was obtained by summing AGB and BGB for each sample tree and averaging the samples. The average tree biomass was multiplied by a factor of 0.45 to determine the carbon stock of the broadleaf forest (Sheikh et al., 2011b).
 
Biomass estimation of under storey vegetation and litter
 
The biomass of shrubs and herbs was also calculated using the destructive harvest approach. In total 15 quadrates (50 × 50 cm) were laid out for herbs and shrubs, respectively. All of the species found in each quadrate were harvested. The total number of shrubs of each species was counted in a quadrate. Shrubs falling in the quadrate were uprooted and brought to laboratory. They were separated in to shoot, branches and leaves and their fresh weight was taken. Samples were stored in paper bags and oven dried at 70°C until the weight is stable for biomass estimation. After that, the biomass values were multiplied by the expansion factor to get an area of one hectare. Similarly, litter biomass was estimated.

Biomass was calculated as follow:

Carbon sequestration
 
For the estimation the carbon stock of the forest system the aboveground and belowground tree biomass was added and multiplied with a co-efficient of 0.45 (Sheikh et al., 2011b). By including the carbon stocks of trees, shrubs, herbs and litter, the carbon stock of a broadleaf forest was calculated. Utilizing the following formula, the carbon inventory of the broadleaf forest was determined. Carbon sequestered=Biomass carbon stock × 3.67 (Rajput, 2010).

Trees morphology, biomass and carbon sequestered
 
Trees present in the study area were B. variegata, T. ciliata, P. roxburghii and Q. leucotricophora. Among these Pinus dominated the forest stand with a mean height of 18.33 m and dbh of 27.45 cm. Average height and crown spread in B. variegata was 5.06 m and 0.57 m and in Q. leucotricophora mean height and crown spread were 17.62 m and 1.51 m, respectively (Table 2). Q. Leucotricophora showed highest dbh, crown spread, crown length and crown index. Nautiyal and Singh, (2013) also reported that the dbh and height in Rhododendron arboreum, Myrica esculenta and Quercus leucotricophora in oak dominated forest of Gopeshwar was 20.46 cm, 28 cm and 150.57 cm and 2.83 m, 6.37 m and 14.75 m, respectively. 


       
Total mean tree biomass of individual species in the present study was in order: B. variegata (24.93 Mg/ha) <T. ciliata (26.65 Mg/ha) <P. roxburghii (151.48 Mg/ha) <Q. leucotricophora (172.31 Mg/ha) as given in the Table 3. Both aboveground and belowground biomass followed the same pattern. The maximum above ground biomass was recorded for Q. leucotricophora (136.75 Mg/ha) and minimum for Bauhinia variegata (19.79 Mg/ha). The maximum and minimum above ground carbon stock was 61.54 Mg/ha for Q. leucotricophora and 8.90 Mg/ha for B. variegata. The total tree carbon stock was recorded maximum (77.54 Mg/ha) for Q. leucotricophora and minimum (11.21 Mg/ha) for B. variegata. Present study’s findings are in line with those of Rawat and Singh, (1988), who also documented above-ground biomass in oak forests (291.4 Mg/ha) and mixed oak-pine forests (325.8 Mg/ha). Compared to other Indian oak and mixed forests, many broadleaf forests have higher above-ground biomass (Rawat and Singh, 1988 and Sharma et al., 2010). Total carbon stock of broadleaf forest was 183.36 Mg/ha/year and it sequestered 672.93 Mg/ha/year carbon (Table 3).


       
Total biomass of land use system is 407.48 Mg/ha/year which is sum total of tree biomass (375.38 Mg/ha/year), shrubs biomass (12.63 Mg/ha/year), herbs biomass (7.84 Mg/ha/year) and litter biomass (11.23 Mg/ha/year). Total carbon stock of broad leaf forest was 183.36 Mg/ha/year and carbon sequestered was 672.95 Mg/ha/year which is comparable with outcomes of studies by Siddiqui and Lodhiyal, 2023, Lodhiyal et al., 2013; Kothai and Geetha, 2025. According to present study, broadleaf forests dominated by oak trees were rich in stocked carbon. Other tree sp. can freely flourish in the microclimate that oak forest stands provide. Oak woods (Q. leucotricophora) are more potent and promising in terms of storing carbon (77.54 Mg/ha/year)  and so reducing the effects of climate change.

The current survey leads to the following conclusions: broad leaf forests with better management inputs and lower usufruct extraction show better health than forest areas with higher anthropogenic pressure, poorer management inputs and less usufruct extraction from neighbouring villages. In addition to these factors, the current soil and climate are believed to have contributed to the vegetation structure and abundance of the region’s broadleaf forests. Therefore, more management and scientific input is needed to preserve those forests that are under anthropogenic stress and are deteriorating. To allow these trees to continue storing atmospheric carbon and thus to help preserve a significant amount of carbon sequestered.

Authors are grateful to Department of biological and environmental sciences and also to Vice-Chancellor, Shoolini University, H.P., for providing necessary facilities and co-operation throughout for conducting the present study.

The authors say that there is no conflict of interest.