Current World Environment

Introduction

The Himalayan chain of mountains extending from west to east for about 2500 km and the width varying between 150 to 450 km, is known to be the youngest, largest and highest chain of mountain in the world.¹ High diverse compositional pattern of the forests is characteristic of this region.¹ The Central Himalayan forests are covered by oak, pine and their associated species. In Indian Himalayan region, most of the temperate forests are occupied by Oak species. Oak considered as the dominant and climax tree species and nearly 35 species of Quercus are present in this region.^3,4,5 The pine forests occur in between 500 to 2000 m and the oak forest in between 1000 and 3500 m elevation.⁶ Between these ranges mixed oak-pine forest are also present. According to Champion and Seth,⁷ in Western and Central Himalayan region three common oak species viz. Quercus leucotrichophora (1800-2300m) Q. floribunda (2000-2500m) and Q. semecarpifolia (2500-3300m) and pine species mostly Pinus roxburghii  and other species like P. wallichina, P. bhutanica, P. gerardiana and P. densata etc. provide a simple and convenient basis for sub division of the altitudinal zones. From the ecological point of view, Nainital and its surroundings become interesting because altitudinal variation over short distances result in the occurrence of forests representing all the above species of oaks and pine.^8,9 These species substantial noteworthy in this region since they serve as lifeline by providing generous ecosystem services to the associated communities.¹⁰ The oak forests are distinguished in comparison to the other forests in reference to containing and maintain higher number of species diversity, litter production and enhance soil quality and fertility.^3,11

The distribution of age structure in a population can predict the status of regeneration in forest ecosystem.^12,13,14 The interaction of a species with biotic or abiotic factors affects their regeneration markedly.¹⁵ For the better growth and to sustain their regeneration in a plant community it is necessary to have the balanced between the presence of older trees, number of younger age tree/sapling and seedlings.¹⁶ The successful regeneration of a forest might be depends on: (i) capability to produce seedlings, (ii) endurance of seedlings and saplings (iii) growing probability of seedlings and saplings.¹⁷ These above mentioned constraints give an imminent into regeneration potential of a species in a natural ecosystem. Several researchers^18,19,20 have already envisaged the regeneration status according to diameter and age structure of tree species in their population.

Numerous noticeable changes are appearing in the Himalayan forest especially in their composition, structure and ability to regenerate. The major causes behind these changes are listed as biotic pressure and uncontrolled anthropogenic activities. The unrestrained lopping, cutting and felling of trees for the requirment of fodder and fuel disturbed the forest ecosystem significantly.^21,22 Grazzing  of young seedlings by the animal also promote the degradation therefore, adversely affacts the regeneration of the forest. To keep all these things in view, this study was design with the following objectives: (i) to provide the quantitative details of tree composition and structure of different forests (ii) to assess the population structure and regeneration potential of trees associated with different forests of Nainital, Uttarakhand. This study will be helpful to know the present scenario of forest ecosystem of Central Himalayan region and their future prospective to develop the strategy of conservation in this region.

Materials and Methods

Study Site

The studied forests were selected in between 550-2000 m above at mean sea level (between 29^o19’-29^o28’ E latitude and 79^o22’-79^o38’ E longitude) in Nainital district (Uttarakhand state) of Central Himalayan, India (Fig. 1). These forests were categorized on the bases of species composition (i.e., Banj-oak forest, Chir-pine forest and Mixed oak-pine forest).  (i). Banj-oak forest site: This forest site was situated in Kailakhan village, about 2 km far from Nainital town. The was located at North-East aspect at 2,084 m (6837 ft.) above sea level between 29^o38 E latitude and 79^o51’ E longitude. The forest exhibits dominance of Banj Oak trees and Quercus leucotrichophora was the dominant tree species. (ii). Chir-pine forest site: This forest site was situated in Mangoli van panchayat, about 18 km far from Nainital town. The site was located at North-East aspect at 550 m above sea level between 29^o38 E latitude and 79^o46’ E longitude. The forest showed the dominance of Chir-pine trees and Pinus roxburghii was considered as the dominant tree species (iii). Mixed Oak-Pine forest site: This forest site was located about 7 km away from Nainital town in North-East aspect at 1654 m above sea level  in between 29^o39 E latitude and 79^o45’ E longitude. This site exhibits co-dominance of Banj-oak and Chir-pine trees. Quercus leucotrichophora  and Pinus roxburghii were the dominant tree species in this forest site. All these forests sites were again divided into three transit positions i.e., hill-base (HB), hill-slope (HS) and hill-top (HT). Therefore a total of three forest type and nine transit position (3 in each) were studied.

The soil of study site is acidic in nature with an average pH of 5.5.  The climate of the study area was considered as monsoon temperate with an annual precipitation of 2347 mm in which, about 75 % rainfall was occurs during the 3 months of monsoon. The mean monthly temperature ranged from 6 ^oC to 25 ^oC during the summer season and from 1.7 ^oC to 4 ^oC during the winter season.

Tree layer vegetation was analyzed by placing 30 random quadrats (10 quadrats in each position) of 10 m  x 10 m in each forest type. The size of the quadrat and their samples numbers were determined following Saxena and Singh.²³ The tree layer vegetation was categorized into seedling (having girth class < 10 cm), sapling (with girth class 10.1-30 cm.) and tree (with girth class ≥ 30.1 cm). The quantitative analysis of vegetation was computed by following Misra.²⁴ The species richness was calculated merely by the counting of different species present in all the quadrats²⁵ in each forest type. Shannon Weiner’ diversity Index²⁶ and concentration of dominance²⁷ were determined for each species at each forest and position.

In order to develop population structure and to understand regeneration of differ­ent species, individuals were measured for circumference at breast height (cbh) with a tape. On the basis of cbh, the trees were arbitrarily classified into six size classes in addition to seedling and sapling class.¹⁷

Results

Species Composition

The detail information about the dominant species of the different forests along with its associated vegetation cover is shown in Table 1 and Table 2. In Banj oak forest, total nine tree species were reported, in which the maximum species richness was occurred in Hill base region (6 species). The total density of tree, sapling and seedling was reported as 1790 ind.ha^-1 (520 ind.ha^-1 at HS to 700 ind.ha^-1 at HB), 80 ind.ha^-1 (20 ind.ha^-1 in each at HB and HT to 40 ind.ha^-1 at HS) and 90 ind.ha^-1 (20 ind.ha^-1 in each at HB and HS to 50 ind.ha^-1 at HT), respectively. The total basal area of tree was 208.37 m²ha^-1 (55.72 m²ha^-1 at HT to 90.83 m²ha^-1 at HB) and sapling layer was estimated 11.63 m²ha^-1 (1.16 m²ha^-1 at HB to 8.82 m²ha^-1 at HS).

The Chir pine forest was constructed by the 5 tree species, of which the maximum number of species was recorded in Hill base region (4 species). The values of tree and sapling density were calculated as 1670 ind.ha^-1 (480 at HB to 620 ind.ha^-1 at HS) and 160 ind.ha^-1 (20 ind.ha^-1 at HT to 80 ind.ha^-1at HS), respectively. The seedling density was reported only 10 ind.ha^-1 at HB while completely absent at HS and HT. The total basal area of the tree layer was 176.54 m²ha^-1 (43.44 at HS to 83.07 m²ha^-1 at HB) while sapling layer constructed only 0.66 m²ha^-1 (0.13 m²ha^-1 at HT to 0.36 m²ha^-1 at HS).

In mixed oak pine forest, collectively 5 tree species were encountered. The maximum number of species were reported in Hill base (5 species) followed by Hill slope region. The total density of tree and sapling layer was reported 1830 ind.ha^-1 (570 at HS to 670 ind.ha^-1 at HB) and 200 ind.ha^-1 (60 at HS to 70 ind.ha^-1 at HB and HT), respectively. The seedlings were completely absent at HS while highest occurred in HB (40 ind.ha^-1).The total basal area of tree layer was estimated 87.22 m²ha^-1 varied in between 27.20 (HS) to 32.29 m²ha^-1 (HT) and sapling layer as 0.59 m²ha^-1 (0.16 m²ha^-1 at HS to 0.23 m²ha^-1 at HB).

Diversity Parameters

In Banj oak forest, the species diversity of tree, sapling and seedling was reported as 1.970, 1.792 and 1.952 while the concentration of dominance as 2.573, 2.120 and 2.020, respectively. In Chir pine forest, the value of species diversity was calculated as 0.634 for tree layer, 1.242 for sapling layer and nil for the seedling layer. The values of concentration of dominance for tree, sapling and seedling were 2.79, 2.22 and 1, respectively. In mixed oak pine forest, the species diversity for tree was 3.14, for sapling 2.13, and for seedling 0.811. The values of concentration of dominance were 1.58, 2.04 and 1.62 for tree, sapling and seedling, respectively.

Population Structure and Regeneration Pattern

The relative percentage of trees, saplings and seedlings of different size classes at each forest site were calculated to develop the population structure (Fig. 2). The Banj oak forest showed poor regeneration due to the density of mature tree > sapling > seedling. Across the position, the sapling density was relatively low and contains higher number of old trees. At Hill top C. deodara was represented by only seedling and sapling which indicating that these species are new to this area.

The Chir pine forest showed poor regeneration having the much greater density of trees than the saplings and seedlings. At Hill base, P. roxburghii was the dominant tree species while L. spectablish found only at sapling and seedling stage which indicated that these are new to that particular area. At Hill slope and Hill top single species P. roxburghii was present at sapling and tree stage only.

Mixed Oak pine forest also exhibited poor regeneration because tree density was greater in comparison of sapling and seedling across the positions. Mixed Oak pine forest was dominated by Q. leucotrichophora and P. roxburghii. R. valagaris, B. reulosa and M. esculenta were the associated species which indicated the diversity status of the forest.

Discussion

The Floristic inventory and diversity parameter helps to know the composi­tion and assortments of the forests,²⁸ which also recommend valuable information regarding to conservation aspects. Forest is considered as a complex fragile ecosystem, therefore it is urgent need to know the actual picture of forests in relation to their composition, structure and diversity as well for their conservation and management. Across the forest type, the density varied from 1670 (Chir pine forest) to 1830 ind.ha^-1 (Mixed oak pine forest). The present tree density was comparatively higher as reported for natural forests of Garhwal Himalaya (1363- 685 ind.ha^-1),²⁹ natural (515 ind.ha^-1)³⁰ and planted forests (484 ind.ha^-1),³⁰ Q. floribunda dominated natural forest (1190- 490 ind.ha^-1)³¹ Q. floribunda dominated forest (930 ind.ha^-1)³² and for disturbed (780- 260 ind.ha^-1)³³ and protected forests (970-460 ind ha^-1).³³ The present values were placed lower than as reported for natural (3429 ind.ha^-1) and planted forests (1865 ind.ha^-1) ³⁴ of north India region.

Basal area gives an idea of stand volume and considered as a vital indicator of carbon storage. The total tree basal area varied in between 87.22 (Mixed oak pine forest) and 208.37 m²ha^-1 (Banj oak forest), which is comparatively less as reported for natural forest (216 m²ha^-1). ³⁵ The present values were placed higher from the range 25.47 to 19.47 to m² ha^-1 and 49.65 to 10.16 m² ha^-1 as reported for disturbed oak forest^33,35 of Nainital catchment, respectively.

The species diversity of a forest is prejudiced by many factors such as altitude, climate, soil, vegetation cover, biotic pressure etc.³. In the present study, total tree diversity was varied from 0.634 (Chir pine forest) to 3.144 (Mixed oak pine forest), which is comparatively higher as reported for planted forest (0.56)³⁴ and for natural forest (0.412-1.769).³¹ The present values were lower as reported for sal plantation (5.53-1.58).^{36, 37}

The biological and ecological characteristics of a population are reflected by their population structure³⁸ and the regeneration profile is provided by the pattern of allocation of individuals in different size classes. The ratio of various age groups in a population determine the reproductive status and determine the future course³⁹ of the population. Population structure of tree species showed the state of forests whether they are sustainable or needs to certain management practices. The overall J-shaped population structure revealed dominancy of trees and lowest number of seedlings across the studied forests (Fig. 3), which undoubtedly indicated that regeneration status is poor in these forests. The less number of seedlings in all the forests may be due to the low viability of seeds, disturbances brought by frequent fire incidence, erosion of soil and water, uncontrolled grazing by animals, cuttings of under canopy plant species by villagers for their domestic cattle etc.^12,20,40 The seedlings, saplings and trees of a plant species exhibit the population dynamic which is used to decide their regeneration status.^41,42 According to Good and Good¹⁷ the soil nutrients, water and sunlight conditions may be the major factors for successful regeneration of the tree species.
 

Table 1: Status of vegetation composition in different forest sites Click here to View table

Table 2: Diversity Parameters of Different Forest Sites

Forest sites	Transect	TREE			SAPLING			SEEDLING
		SR	H’	Cd	SR	H’	Cd	SR	H’	Cd
Banj oak forest	HB	6	0.660	0.786	1	0	1.000	2	0.996	0.500
	HS	4	0.370	0.888	2	0.796	0.620	1	0	1.000
	HT	2	0.940	0.899	2	0.996	0.500	2	0.956	0.520
Chir pine forest	HB	4	0.634	0.796	3	1.242	0.225	1	0	1.000
	HS	1	0	1.000	1	0	1.000	A	-	-
	HT	1	0	1.000	1	0	1.000	A	-	-
Mixed oak pine forest	HB	5	1.224	0.464	3	1.145	0.543	2	0.811	0.625
	HS	3	1.099	0.507	1	0	1.000	A	-	-
	HT	2	0.821	0.610	2	0.988	0.501	1	0	1.000

SR=Species richness, H’=diversity, Cd=concentration of dominance

 

Figure 1: Map showing the location of studied forests (in red dots) in Nainital district (Uttarakhand state) of India  Click here to View figure

 

Figure 2: Population structure of different forest in Banj-oak forest, Chir pine forest and mixed Oak-pine forest  Click here to View figure

 

Figure 3: Regeneration status of studied forests (Banj oak forest, Chir pine forest and Mixed oak forest) Click here to View figure

Acknowledgments

All authors are grateful to the Head, Department of Botany, DSB campus, Nainital for providing required conveniences. The second author (KP) sincerely acknowledges the BSR (UGC), New Delhi for financial support.

Conflict of interest

There are no known declared conflicts of interest related with this piece of research work.

References
 

1. Singh, J.S. and Singh, S.P. An integrated ecological study of Eastern Himalaya with emphasis on natural resources (vol.1-3) Kumaun University, Nainital. 1984;378.
2. Troup, R.S. The Silviculture of Indian trees Vol. 1-111. Claren­don Press, Oxford. 1921;1195.
3. Bargali, K., Joshi, B., Bargali, S.S., and Singh, S.P. Diversity within oaks. International oaks. 2014;25:57-70.
4. Bargali, K., Joshi, B., Bargali, S.S., and Singh, S.P. Oaks and the biodiversity they sustain. International Oaks. 2015;26:65-76.
5. Padalia, K., Parihaar, R.S., Bhakuni, N., and Kapkoti, B. Leaf litter decomposition of two Central Himalayan oaks. Current World Environment. 2015;10(2):509-516.
   CorssRef
6. Bargali, K., Bargali, S.S. Nutrient utilization efficiencies of two Central Himalayan tree species. Journal of Tropical Forest Science. 2000;12 (3):450-458.
7. Champion, H.G., and Seth, S.K. A Revised survey of the forest types of India. Govt of India publication, New Delhi. 1968.
8. Bargali, S.S., and Singh, R.P. Pinus patula plantations in Kumaun Himalaya. I. Dry matter dynamics. Journal of Tropical Forest Science. 1997a;9(4):526-535.
9. Bargali, S.S., and Singh, R.P. Pinus patula plantations in Kumaun Himalaya II. Nutrient dynamics. Journal of Tropical Forest Science. 1997b;10(1):101-104.
10. Gosain, B.G., Negi, G.C.S., Dhyani, P.P., Bargali, S.S., and Saxena, R. Ecosystem services of forests: Carbon Stock in vegetation and soil components in a watershed of Kumaun Himalaya, India. International Journal of Ecology and Environmental Science. 2015;41(3-4):177-188.
11. Shrestha, B.B. Quercus semecarpifolia in the Himalayan region: Ecology, exploitation and threats. Himalayan Journal of Sciences. 2003;1(2): 26-128.
12. Adhikari, B., Kapkoti, B., Lodhiyal, N., and Lodhiyal, L.S. Structure and regeneration of Sal (Shorea robusta Gaertn. f.) forest in Shiwalik region of Kumaun Himalaya, India. Indian Journal of Forestry. 2017;40(1):1-8.
13. Pande R, Bargali K, Pande N. Impacts of disturbance on the population structure and regeneration status of tree species in a Central Himalayan Mixed-Oak Forest, India. Taiwan Journal of Forest Science. 2014;29(3):179-192.
14. Rana, S., Bargali, K., Bargali, S.S. Assessment of plant diversity, regeneration status, biomass and carbon stock in a Central Himalayan cypress forest. International Journal of Biodiversity and Conservation. 2015;7(6):321-329.
    CrossRef
15. Poorter, R.W., and Arets, E.J.M. Light environment and tree strategy in a Bolvian tropical moist forest: an elevation of the light partitioning hypothesis. Plant Ecology. 2003;166:295-306.
    CrossRef
16. Taylor, A.H., and Zisheng, Q. Regeneration pattern in old growth Abies-Betula forests in the Wolony Natural Reserve, Sichuan, China. Journal of Ecology. 1988;76:1204-1218.
    CrossRef
17. Good, N.F., and Good, R.E. Population dynamics of tree seedling and saplings in mature Eastern hardwood forest. Bulletin of the Torrey Botanical Club. 1972;99(4):172-178.
18. Bargali, S.S., Rana, B.S., Rikhari, H.C., and Singh, R.P. Population structure of Central Himalayan blue pine (Pinus wallichiana) forest. Environment and Ecology. 1989;7:431-436.
19. Bhuyan, P., Khan, M.L., and Tripathi, R.S. Tree diversity and population structure in undisturbed and human- impacted stands of tropical wet evergreen forest in Arunachal Pradesh, Eastern Himalaya. Biodiversity and Conservation. 2003;12:1753-1773.
20. Pandey, R., Bargali S.S., and Bargali, K. Does seed size affect water stress tolerance in Quercus leucotrichophora camus at germination and early seedling growth stage? Biodiversity International Journal. 1(1):00005. doi:10.15406/bij.2017.01.00005
21. Bargali, K., Usman, and Joshi, M. Effect of forest covers on certain site and soil characteristics in Kumaun Himalayas. Indian Journal of Forestry. 1998;21(3):224-227.
22. Kumar, M., Sharma, C.M., and Rajwar, G.S. A study on the community structure and diversity of a sub-tropical forest of Garhwal Himalayas. Indian Forester. 2004;130(2):207-214.
23. Saxena, A.K., and Singh, J.S. A phytosociological analysis of woody species in forest communities of a part of Kumaoun Himalaya. Vegetatio, 50(1):3-22.
24. Misra, R. Ecology Workbook. Oxford and IBH Publishing Company, Calcutta 1968.
25. Whittaker, R.H., Likens, G.E., Bormann, F.H., Eaton, J.S., and Siccama, T.G. The Hubbard Brook ecosystem study. Forest Nutrient Cycling Aand Element Behavior Ecology. 1979;60:203-220.
26. Shannon, C. E., and Weiner, W. The mathematical theory of communities. University of Illinois Press, Urbana. 1963.
27. Simpson, E.H. Measurement of Nature. 1949;163(4148):688.
28. Phillips, O.L., Martinez, R.V., Vargas, P.N., Monteagudo, A.L., Zans, M.C., Sanchez, W.G., Cruz, A.P., Timana, M., Yli-Halla and Rose, S. Efficientplot-based floristic assessment of tropical forests. Journal of Tropical Ecology. 2003;19:629-645.
29. Pokhriyal, P., Chauhan, D.S., and Todaria, N.P. Effect of altitude and disturbance on structure and species diversity of forest vegetation in a watershed of central Himalaya. Tropical Ecology. 2012;53(3):307-315.
30. Chauhan, D.S., Dhanai, C.S., Singh, B., Chauhan, S., Todaria, N.P., and Khalid, M.A. Regeneration and tree diversity in natural and planted forests in a Terai - Bhabhar forest in Katarniaghat Wildlife Sanctuary, India. Tropical Ecology, 2008;49(1):53-67.
31. Lodhiyal, N., Dhek, S., Lodhiyal, L.S., Bhakuni, N., and Kapkoti, B. Species diversity and regeneration of Tilonj Oak (Quercus floribunda ) dominated forests of Nainital in Kumaun Himalaya. International Journal of Biodiversity and Conservation. 2015;7(1):21-27.
32. Kumar, A., and Ram, J. Anthropogenic disturbances and plant biodiversity in forests of Uttarakhand, Central Himalaya. Biodiversity and Conservation. 2005;14:300-331. http://dx.doi.org/10.1007/s10531-004-5047-4.
33. Bargali, K., Bisht, P., Khan, A., and Rawat, Y.S. Diversity and regeneration status of tree species at Nainital Catchment, Uttarakhand, India. International Journal of Biodiversity and Conservation. 2011;5(5):270-280.
34. Tripathi, K.P., and Singh, B. Species diversity and vegetation structure across various strata in natural and plantation forests in Katerniaghat Wildlife Sanctuary, North India. Tropical Ecology. 2009;50(1):191-200.
35. Tripathi, B.C., Rikhari, H.C., Bargali, S.S., and Rawat, Y.S. Species composition and regeneration in disturbed forest sites in the oak zone in and around Nainital. Proceedings of Indian National Science Academy. 2009;57(6):381-390(1991).
36. Pandey, S.K., and Shukla, R.P. Plant diversity and community pattern along the disturbance gradient in plantation forests of Sal (Shorea robusta Gaertn.). Current Science. 1999;77:814-818.
37. Shukla, R.P., and Pandey, S.K. Plant diversity and community features of the forested landscape adjacent to foot-hills of Central Himalyas. pp. 15-37. In: Tiwari, S.C., & Dabral, P.P., (eds.) Natural Resources, Conservation and Management for Mountain Development. International Book Distributor, Dehradun. 2000.
38. Saxena, A.K., and Singh, J.S. Tree population structure of certain Himalayan forest associations and implications concerning their future composition. Vegetatio. 1984;58:61-69.
    CrossRef
39. Odum, E.P. Fundamentals of Ecology (III ed.)B. Saunders Co., Philadelphia, U.S.A. 1971;574.
40. Kapkoti, B., Adhikari, B., Lodhiyal, N., and Lodhiyal, L.S. Struture and diversity of Sal forests in government and community management systems in Kumaun region of Central Himalaya. Current World Environment. 2016;11(1):126-132.
    CrossRef
41. Teketay, D. Seedling populations and regeneration of woody species in dry Afromontane forests of Ethiopia. Forest Ecology and Management. 1997;98:149-165.
    CrossRef
42. Baboo, B., Sagar, R., Bargali, S.S., and Verma, H. Tree species composition, regeneration and diversity within the protected area of Indian dry tropical forest. Tropical Ecology. 2017;58(3):409-423.