Current World Environment

Introduction

Forest plays a significant role in biomass production and carbon sequestration. Apart from these, they supply a wide range of goods and services including timber, fuelwood and fodder. Forests are foundation of biodiversity and also mitigate the climate change by sequestering carbon dioxide in atmosphere. Present study of Sal (Shorea robusta Gaertn f.) forests covered a large area in foothills of Shiwalik in Kumaun region of Central Himalaya. Recent growing anthropogenic pressure on Sal forest for different uses like timber, fodder, fuelwood and leaflitter it is very imperative to assess the real time data about the stand structure, dry matter and carbon storage in such forest which are closed to human habitation. However, a few studies on sal forests particularly on biomass and Net Primary Production (NPP) were made by various researchers^1-5, but there is scarcity of datarelated to carbon and its storage capacity in this region. It is assumed that the carbon percent in biomass ranged from 45 to 50 percent^6-7. In this context, stand structure of Sal forest is very important in controlling the various aspects of dry weight, production and carbon potential growing in the region so that the sal forest could be managed and conserved for their full potential of biomass, productivity and carbon. This study aims to analyze the stand composition, biomass and carbon stock of Sal forest in Kumaun region of Central Himalaya. 

Methodology                                                        

Description of study site

This study was performed to evaluate the vegetation structure, biomass and carbon stock in sal forest sites located in Tanakpur (29.074894⁰ N lat. and 80.1083018⁰ E long) of Champawat district, Uttarakhand, India. The sal forest sites were located between 250-358 m elevation. On the basis of canopy cover sal forest sites were categorized into dense (Site-1), moderate (Site-2) and open forest (Site-3).The canopy cover of sal forest was 60-70% for dense forest, 50-55% for moderate forest and 25-40% for open forest.

Methods

Quadrat method (10 x10m size.) was used for the assessment of tree species. In each site, 30 quadrats were randomly placed and circumference of trees was considered at breast height i.e. 1.37 m from the ground level. In each study sites, vegetational parameters were estimated as followed⁸. Species diversity of vegetation was evaluated by using Shannon-Weiner information index⁹. Simpson Index¹⁰ was used to calculate concentration of dominance (Cd). Biomass of tree components i.e. bole, branch, twig and leaves was estimated by using allometric equation developed by various scientists^2,11. Carbon was estimated by using the given factor⁷. The carbon (C) was estimated by using biomass value of component of forest multiplied by 0.475 factor. In each site, total carbon of forest was anticipated by adding carbon values of all tree components. Statistical analysis i.e. Pearson’s correlation test was performed using SPSS Software Version 21.0.

Results

Vegetation analysis

Site-1

Total nine trees were found  in this site. Tree density was 690 indiv.ha^-1.Of this, S. robusta (370 indiv.ha^-1) followed by Syzygium cumini (80 indiv.ha^-1), Haldina  cordifolia (70 indiv.ha^-1), Terminalia bellerica (40 indiv.ha^-1) and Terminalia tomentosa (30 indiv.ha^-1). Total basal area was 78.8 m²ha^-1. S. robusta (54.5) accounted maximum basal area followed by S.cumini (8.1m²ha^-1), H. cordifolia (4.6 m²ha^-1), T.bellerica (3.7m²ha^-1) and T.tomentosa (2.9m²ha^-1). The IVI of tree species ranged from 8 (Albizzia lebbeck) to 105 (S. robusta).Species diversity of trees range from 0.01 to 1.0 in the forest (Table 1).

Site-2

Total eight tree species were recorded  in this site. Tree density was 510 indiv.ha^-1.Of this, S. robusta (310 indiv.ha^-1) followed by Mallotus philippensis (100 indiv.ha^-1), S.cumini (30 indiv.ha^-1) and Allianthus excelsa (20 indiv.ha^-1). Total basal area was 75.3 m²ha¹. S. robusta (62.7 m²ha^-1) accounted maximum basal area followed by M.philippensis (4.7m²ha^-1), S.cumini (2.4 m²ha^-1) and A.excelsa (0.8 m²ha^-1). The IVI ranged among tree from 12.4 (Trewia nudiflora) to 130 (S. robusta).The tree species diversity varied from 0.001 to 1.2 in the forest (Table 2).

Site-3

Total two tree species were found in this site. Tree density was 290 indiv.ha^-1.Of this, S. robusta (220 indiv.ha^-1) and T. grandis (70 indiv.ha^-1). Total basal area was (50.9 m²ha^-1). S. robusta (43 m²ha^-1) accounted maximum basal area and IVI. The tree species diversity of S. robusta (1.9) and Tectona grandis (0.9) in the forest (Table 2).

Total fifteen tree species i.e.  S. robusta Gaertn., S.cumini L. Skeels, H. cordifolia (Roxb.)Ridsdale., T.bellerica (Gaertn.) Roxb., T. tomentosa, Lannea parviflora, M.philippensis(Lam.) Muell.-Arg. , Lannea coromendelica (Houtt.) Merr., A.lebbeck, A.excelsa, Ficus hispida L., B. ceiba, Cassia  fistulaL. , T.nudiflora, and T. grandis L.were reported in sal forests. Total tree density varied from 290 to 690 indiv. ha^-1 across the all forest sites. Total basal area of trees ranged between 50.9 to 78.8m²ha^-1. The species diversity for the trees ranged between 1.1-2.1 in the studied sal forest (Table 1). 

Table 1: Phytosociological attribute (Density, TBA) in sal forests in the Tanakpur of district Champawat in Kumaun, Central Himalaya.

Note: D= Density, BA= Basal Area, IVI=Important Value Index, H^- =Species diversity, Cd= Concentration of dominance

Biomass

Site-1

Total tree biomass was 787.2t ha^-1in sal dense forest. Aboveground and belowground tree components accounted for 77.9 and 22.1% respectively (Table 2). S. robusta contributed 613.6t ha^-1 followed by S.cumini 60.3t ha^-1 in total biomass whereas A. lebbeck contributed minimum biomass 15.8 t ha^-1in this site. However, bole component shared maximum (56.7%) biomass in the above ground part. In aboveground component i.e. bole, branches, twigs and foliage accounted for 46.1-58.0, 12.6-19.8, 3.4-5.9, 2.4-4.4% respectively while belowground part shared 20.5-27.8% biomass among the studied tree species (Table 2).

Site-2

Total tree biomass was 754.8t ha^-1 in sal moderate forest. Aboveground and belowground tree components accounted for 78.9 and 21.1% respectively (Table 2). S. robusta contributed 691 t ha-1 followed by B. Ceiba 23.0 t ha^-1 in total biomass whereas T. nudiflora contributed minimum biomass 3.3 t ha^-1in this site. However, bole component shared maximum (58.7%) biomass in the above ground part. In aboveground component i.e. bole, branches, twigs and foliage accounted for 43.3-59.5, 19.5-11.9, 2.8-5.5, 2-4% respectively while belowground part shared 20.5-27.8% biomass among the studied tree species (Table 2).

Site-3

Total tree biomass was 473.3t ha^-1in sal open forest. Aboveground and belowground tree components accounted for 79.5 and 20.5 % respectively (Table 2). S. robusta contributed 472.0 t ha-1 followed by T. grandis 1.3 t ha^-1 in  total biomass whereas T.grandis contributed minimum biomass 1.3 t ha^-1 in this site. However, bole component shared maximum (59.19%) biomass in the above ground part. In aboveground component i.e. bole, branches, twigs and foliage accounted for 39.8-59.4, 11.9-1, 23.3-5.1, 3.1-7.5% respectively while belowground part shared 20.5-17.3% biomass among the studied tree species (Table 2).

Total biomass ranged 473.3 to 787.2t ha^-1 in the sal forests (Fig.1). The aboveground and belowground components accounted 77.9 to 79.5 % and 20.5 to 22.1 % respectively.

Table 2: Component wise tree biomass (tha^-1) in sal forests at three forest sites

* TAG (Total Above Ground) * TBG (Total Below Ground) (values in parentheses are the percentage contribution)

Carbon stock

Site-1

Total carbon stock of trees was 373.9t C ha^-1 in sal dense forest. Aboveground and belowground tree components accounted for 77.9 % and 22.1 % respectively. (Table 3). S. robusta contributed 291.5t C ha^-1 followed by S. cumini 28.6t C ha^-1 in total carbon stock. Among the aboveground component, bole shared maximum 56.7% carbon (Table 4).In aboveground component i.e. bole, branches, twigs and foliage accounted for 47-58.1, 12.6-19.9, 3.4-5.8, 2.2-4.2% respectively while belowground part shared 20.5-27.8% carbon content among the studied tree species. (Table 3). 

Site-2

Total carbon stock of trees was 358.6t C ha^-1 in sal dense forest. Aboveground and belowground tree components accounted for 78.9% and 21.2% respectively. (Table 3). S. robusta contributed 328.3t C ha^-1 followed by B. ceiba 18.8t C ha^-1 in total carbon stock. Among the aboveground component, bole shared maximum 63.3 % carbon (Table 4). In aboveground component i.e. bole, branches, twigs and foliage accounted for 43.2-59.5, 11.9-19.5, 2.8-5.5, 2-4% respectively while belowground part shared 20.5-27.8% carbon content among the studied tree species. (Table 3). 

Site-3

Total carbon stock of trees was 224.8t C ha^-1 in sal open forest. Aboveground and belowground tree components accounted for 79.5 % and 20.5 % respectively. S. robusta and T. grandis contributed 224.2 t C ha^-1 and 0.6 t C ha^-1 total carbon stock respectively.  Among the aboveground component, bole shared maximum 59.3% carbon. The carbon storage of different tree species ranged from 79.5-82.8 and 17.2-20.5 % in above and belowground part, respectively (Table 3).Total carbon stock ranged 373.9 to 224.8 t C ha^-1 in the sal forests. The aboveground and belowground accounted 77.9 to 79.5 % and 20.5 to 22.1 % carbon respectively.

Table 3: Component wise carbon stock (tha^-1) in sal forests at three forest sites

* TAG (Total Above Ground) * TBG (Total Below Ground) (values in parantheses are the percentage contribution)

Discussion

Forest structure, stocks of biomass and carbon varies with composition of tree species, age and density of plant species occurring in the forest. The tree species growing in Tarai region mainly dominated by Sal (S. robusta) and associated with trees and under canopy plant species. Present study was performed on structure, biomass and carbon content in respective forest site. The three forest sites were located at different area and direction. In each site there was a variation in tree density, species diversity, basal area, biomass and carbon. 

Table 5: Correlation between vegetational parameters through Pearson’s correlation matrix 

* Correlation is significant at the 0.05 level (2-tailed).  **. Correlation is significant at the 0.01 level (2-tailed). 

Figure 1: Relationship between total biomass and carbon stock of Sal forests.    Click here to view Figure

The tree density in sal forests varied from 290-690 indiv.ha^-1, these values comes within the range 35-863 indiv. ha^-1 of Sal forests of Shiwalik region^{2,5, 12-19}. The present values are somewhat close to 35-419 indiv. ha^-1of dry tropical forest¹⁴ and lower side than 756-911 indiv.ha^-1 of sal mixed forest^20-21. However, basal area of Sal forests ranged from 50.9 to 78.8 m² ha^-1, ¹⁸which was slightly higher side than the range 25.3-77.6m² ha^-1 and 23.2 - 47.8m² ha^-1 of tree species¹⁹. Tree species diversity was 1.1-2.1 in sal forest which falls within the range 0.7 - 2.6 of sal forest in Central Himalaya^13-15,18,20 and the range slightly higher side than 0.698-0.904 for dry tropical forest¹⁴.

Biomass and carbon stock of sal forests ranged from 473.3 to787.1t ha^-1 and 224.8-373.9t C ha^-1, respectively (Fig.1). The abovesaid values are on higher side than 66.5 to 710 t ha^-1of biomass and 33.5 to 337.3 t ha^-1carbon of sal forests of central Himalaya^{2,12,16,17,22-25}and lower side than 1280.8 t ha^-1 biomass and 577.8 t ha^-1 carbon stock of sal dominant forest⁵. However, the present values are nearly close to455-710t ha^-1of biomass and 216.1-337.3t ha^-1carbon of Sal forest², 380.0- 815.0 t ha^-1biomass and 181.0-387.0 t ha^-1carbonofsal mixed forest of Kumaun Himalaya¹³and 408.9 - 704.3t ha^-1 biomass^,194.2 - 339.5t ha^-1carbon of sal forests¹⁹(Table 4). The Pearson’s correlation indicates that the tree density was positively correlated with total basal area (r²= 0.94), biomass (r²= 0.93) and carbon stock (r²= 0.93) and negatively correlated with tree diversity (p<0.05) significant among the forest stands (Table 4). S. robusta shared maximum tree biomass (471.9 to 691 t ha^-1)and carbon content (224.2 to 328.3 t C ha^-1) in all forest sites. Biomass and carbon stocks are depicted in Fig.1.

Present findings had shown that there was a variation among various parameters studied in all forest sites. The site-1 had more tree density, diversity, biomass and carbon compared to other sal forest site-2 and site-3. On the basis of findings, it is concluded that the forests sites which had better management inputs and less extraction of usufructs had shown a good condition than the forest sites which had more anthropogenic pressure and poor management inputs as well as unscientific extraction of usufructs by nearby village. Apart from these, it is assumed that the existing soil and climatic condition of the area were also responsible for the vegetation structure and stocks of Sal forests of the region. Therefore, those forests which are degraded and have anthropogenic pressure should be conserved by providing better management and scientific inputs.  So that these forests could save large amount of carbon by sequestering the atmospheric carbon continuously and would also help in the battle against global warming and climate change.

Acknowledgment

The author would like to thank the Head of the Department of Forestry and Environmental Science, D. S. B. Campus, Kumaun University, Nainital for providing the laboratory facilities.

Conflict of Interest

The authors do not have any conflict of interest.

Funding source

There is no funding or financial support provided for this research work.

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