**8. Ecological significance of** *Terminalia arjuna* **in Cauvery river**

#### **8.1. Ecosystem engineers**

*Terminalia arjuna* in the Cauvery riverine ecosystem can be referred as 'Ecosystem Emgineers" as it modifies the physical environment by releasing resources to be used by other species. The activities of many organisms provide habitat that would not otherwise be available, often by means of disturbance to the physical habitat. Because of structural alterations they support many organisms and are often referred to as ecosystem engineers (Jones *et al*., 1994). *Terminalia arjuna* stabilizes river banks, trap sediments, increases nutrient availability in the top soil so Protection of Riparian Habitats to Conserve Keystone Species with Reference to *Terminalia arjuna* – A Case Study… http://dx.doi.org/10.5772/58355 101

**Figure 3.** Species *Terminalia arjuna* growing along the banks of River Cauvery

tailed Macaque (*Macaca silenus*) and so on. The forest landscapes here act as corridors for wildlife, as they are in contiguous with large protected areas such as Nagarahole National

The river bordering the Cauvery Wildlife Sanctuary in lower reaches of the river has a population of otters, crocodiles and many varieties of fishes along with the famous Masheer. This area is the breeding ground for a number of reptilian species like crocodiles, turtles, python, cobra, russell's viper, banded krait and masheer fish besides wild boar, barking deer, four-horned antelope, green-billed malkoha, white-browed bulbul, pigmy woodpecker. Around 1000 elephants (*Elepha maximus*) graze through these riparian areas, as it also provides connectivity to Biligiri Rangan Hills Temple (BRT) wildlife Sanctuary and Mudumalai Tiger Reserve, which are in conjunction with Mysore – Nilgiri corridor (largest population of Asian

**7.** *Terminalia arjuna* **as a keystone species in Cauvery riverine ecosystem**

Distributed throughout moist deciduous places of southern India, frequenting the banks of the water courses. Identified by thick grey smooth bark, exfoliating in large thin irregular sheets and buttressed trunk. It thrives best on loose moist, fertile alluvial loams and light deep sandy soils, often overlying more or less imprevious rock. The soil should have ample water supplies but should normally be well-drained. The soil under this tree becomes rich in calcium as the leaves are rich in this element. *Terminalia arjuna* species is deciduous, dominant canopy species and a representative riparian elements in riparian forests in lower reaches of Cauvery river. It can live grows to approximately 30m-45 in height, with a diameter at breast height (DBH) ranging from 300 cm – 600 cm. The *Terminalia arjuna* species is well adapted in the riparian zone by developing the buttressed type of root system to withstand the flood events.

*Terminalia arjuna* scattered along the lower of stretch of riparian forest is identified as a Keystone species. These scattered trees will acts as keystone structures as it supports wide array of species groups (e.g. arthropods, birds or mammals) for food resource and as shelter or nesting site (Munzbergova and Ward 2002; Plieninger *et al*., 2003; Tews *et al*., 2004).

*Terminalia arjuna* in the Cauvery riverine ecosystem can be referred as 'Ecosystem Emgineers" as it modifies the physical environment by releasing resources to be used by other species. The activities of many organisms provide habitat that would not otherwise be available, often by means of disturbance to the physical habitat. Because of structural alterations they support many organisms and are often referred to as ecosystem engineers (Jones *et al*., 1994). *Terminalia arjuna* stabilizes river banks, trap sediments, increases nutrient availability in the top soil so

**8. Ecological significance of** *Terminalia arjuna* **in Cauvery river**

Park, Talacauvery, Brahmagiri and Pushpagiri Wildlife Sanctuaries.

elephants is found here).

100 Biodiversity - The Dynamic Balance of the Planet

**8.1. Ecosystem engineers**

as to provide a competitive advantage for adventitive forbs and grasses with higher nutrient requirements than their native counter parts.

**Figure 4.** Species *T. arjuna* with its interlocking root system

The interlocking root system of this tree reduces the efficiency of rivers to withstand flood events and the butresses roots of this species are effective soil binders. Thus play a significant role in modifying the physical environment in ways that release resources for other species. Flood is a regular event in the downstream of River Cauvery, *Terminalia arjuna* act as barrier against erosion and stabilizes river bank in the riparian forest. It is the lone species along the riparian corridor acting as an emergent layer with good amount of canopy contributing to maintenance of micro climatic conditions viz., soil moisture and nutrirents. It is also necessary for the survival of the other evergreen species such as *Olea dioca*, *Syzygium sp*, *Madhuca neriifolia*, *Madhuca latifolia* etc during the seedling and sapling stage in the lower riparian stretch. The laden and gravels retained between the roots of *T.arjuna* retains soil moisture required for vegetation establishment and also provides a new substrates for the colonization of riparian plants. This species with good canopy cover limits the establishment or invasive from the adjacent scrub and dry land harboring *Canthium sp*, *Alangium salviforum*, *Acacia catechu* etc., as potential dominants. Thereby competition with semi-evergreen species is avoided. Hence absence of this species along the riparian corridor might cause a major change in the riparian vegetation structure and composition.

#### **9. Resource providers**

*Terminalia arjuna* acts as resource provider, as the leaves and flowers of this species falling into the water form diet for a number of fishes. The tree-lined river bank also provides shelter and shade to fish. Shade also keeps the growth of water weeds in balance, and regulates the temperature of water. The smooth coated otter (*Lutra perspicillata*) catego‐ rized as 'vulnerable' by 2004 IUCN Red List in the Cauvery Wildlife Sanctuary (CWS), needs a healthy aquatic ecosystem with plenty of fish. The shade provided by trees along the water's edge help to promote fish abundance with obvious benefits for the otter. Besides, gaint trees of *Terminalia arjuna* in the riparian zone act as a good potential nesting sites for bees and numerous bats which roost during day time. The bats play an important role as pollinators and seed dispersal agents. The riparian vegetation in the middle reaches of the Cauvery river is fragmented by various types of anthropogenic pressures resulted in shrinkage of several endemic species in riparian zone (Sunil et al., 2010). As the larger forks and branches of *Terminalia arjuna* provides a habitat for natural pollinators like honey bees, bats etc., influences the chance of recovery of native species in the fragmented patches of the riparian buffer in the middle reaches of the river. The huge canopy offered by *T.arju‐ na* species forms a thick patches in the riparian zone serving as important buffers in the semi-arid ecosystem, enable to provide a vital links to sensitive wildlife species such as *Ratufa macroura* (grizzled giant squirrel), an IUCN Red listed –near threatened species (Baskaran et al., 2011) which demands thick canopy cover along the riparian zones for breeding and feeding purpose (Joshua and Johnsingh, 1994).

**Figure 5.** *T. arjuna* acting as the roosting sites for the bats during the day time

**10. Control of Invasive species in riparian zones**

(Sunil et al., 2011).

Riparian habitats are more susceptible to exotic species invasion due to the nutrient rich laden sediments and periodic flooding followed by hydrochory (Pyse and Prach 1994; Gregory and Naiman 2000). Invasion of non-native species in the riparian zone constitutes most serious threats to the biodiversity through the displacement of native plants (Shigenari and Izumi 2004). The Cauvery river in the lower reaches is is surrounded by dry deciduous to scrub type forests, and moist deciduous to semi-evergreen type trees along the river bank. Since the riparian zone stands distinctly here by harboring moist deciduous to semi-evergreen type vegetation, during dry season they assumes a very significant place for wildlife (Natta et al. 2003) particularly to the otters and wide elephant herds found in the sanctuary. But, the riparian vegetation here stands in high risk areas, as there is a chance of invasion of several pioneer species resided in the adjoining dry deciduous and scrub type vegetation into the riparian areas (Manjunath, 2001). Some of the fragmented corridors in riparian forest has already witnessed the invasion of scrub type species by lessening the native riparian species

Protection of Riparian Habitats to Conserve Keystone Species with Reference to *Terminalia arjuna* – A Case Study…

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Riparian species demands shade and moisture in soil in the early stages of their germinations. Huge canopy offered by *Terminalia arjuna* provide sufficient shade and holds soil moisture Protection of Riparian Habitats to Conserve Keystone Species with Reference to *Terminalia arjuna* – A Case Study… http://dx.doi.org/10.5772/58355 103

**Figure 5.** *T. arjuna* acting as the roosting sites for the bats during the day time

The interlocking root system of this tree reduces the efficiency of rivers to withstand flood events and the butresses roots of this species are effective soil binders. Thus play a significant role in modifying the physical environment in ways that release resources for other species. Flood is a regular event in the downstream of River Cauvery, *Terminalia arjuna* act as barrier against erosion and stabilizes river bank in the riparian forest. It is the lone species along the riparian corridor acting as an emergent layer with good amount of canopy contributing to maintenance of micro climatic conditions viz., soil moisture and nutrirents. It is also necessary for the survival of the other evergreen species such as *Olea dioca*, *Syzygium sp*, *Madhuca neriifolia*, *Madhuca latifolia* etc during the seedling and sapling stage in the lower riparian stretch. The laden and gravels retained between the roots of *T.arjuna* retains soil moisture required for vegetation establishment and also provides a new substrates for the colonization of riparian plants. This species with good canopy cover limits the establishment or invasive from the adjacent scrub and dry land harboring *Canthium sp*, *Alangium salviforum*, *Acacia catechu* etc., as potential dominants. Thereby competition with semi-evergreen species is avoided. Hence absence of this species along the riparian corridor

might cause a major change in the riparian vegetation structure and composition.

breeding and feeding purpose (Joshua and Johnsingh, 1994).

*Terminalia arjuna* acts as resource provider, as the leaves and flowers of this species falling into the water form diet for a number of fishes. The tree-lined river bank also provides shelter and shade to fish. Shade also keeps the growth of water weeds in balance, and regulates the temperature of water. The smooth coated otter (*Lutra perspicillata*) catego‐ rized as 'vulnerable' by 2004 IUCN Red List in the Cauvery Wildlife Sanctuary (CWS), needs a healthy aquatic ecosystem with plenty of fish. The shade provided by trees along the water's edge help to promote fish abundance with obvious benefits for the otter. Besides, gaint trees of *Terminalia arjuna* in the riparian zone act as a good potential nesting sites for bees and numerous bats which roost during day time. The bats play an important role as pollinators and seed dispersal agents. The riparian vegetation in the middle reaches of the Cauvery river is fragmented by various types of anthropogenic pressures resulted in shrinkage of several endemic species in riparian zone (Sunil et al., 2010). As the larger forks and branches of *Terminalia arjuna* provides a habitat for natural pollinators like honey bees, bats etc., influences the chance of recovery of native species in the fragmented patches of the riparian buffer in the middle reaches of the river. The huge canopy offered by *T.arju‐ na* species forms a thick patches in the riparian zone serving as important buffers in the semi-arid ecosystem, enable to provide a vital links to sensitive wildlife species such as *Ratufa macroura* (grizzled giant squirrel), an IUCN Red listed –near threatened species (Baskaran et al., 2011) which demands thick canopy cover along the riparian zones for

**9. Resource providers**

102 Biodiversity - The Dynamic Balance of the Planet

### **10. Control of Invasive species in riparian zones**

Riparian habitats are more susceptible to exotic species invasion due to the nutrient rich laden sediments and periodic flooding followed by hydrochory (Pyse and Prach 1994; Gregory and Naiman 2000). Invasion of non-native species in the riparian zone constitutes most serious threats to the biodiversity through the displacement of native plants (Shigenari and Izumi 2004). The Cauvery river in the lower reaches is is surrounded by dry deciduous to scrub type forests, and moist deciduous to semi-evergreen type trees along the river bank. Since the riparian zone stands distinctly here by harboring moist deciduous to semi-evergreen type vegetation, during dry season they assumes a very significant place for wildlife (Natta et al. 2003) particularly to the otters and wide elephant herds found in the sanctuary. But, the riparian vegetation here stands in high risk areas, as there is a chance of invasion of several pioneer species resided in the adjoining dry deciduous and scrub type vegetation into the riparian areas (Manjunath, 2001). Some of the fragmented corridors in riparian forest has already witnessed the invasion of scrub type species by lessening the native riparian species (Sunil et al., 2011).

Riparian species demands shade and moisture in soil in the early stages of their germinations. Huge canopy offered by *Terminalia arjuna* provide sufficient shade and holds soil moisture during the germination stage of riparian tree species. Some native species which supports avifaunal abundance such as *Ixora bracheata, Syzygium cumini, Syzygium jambose, Diospyros melanoxylon* and *Madhuca latifolia* resembles healthy association to the keystone species *Terminalia arjuna*. Also, it checks the growth of pioneer species in the riparian zone, thereby competition with riparian and semi-evergreen species harbored in riparian zone is avoided. Decline in native species such as *Syzygium cumini, Syzygium jambose, Madhuca sp* along the river bank might lead to the decline of natural source of leaves, twigs, fruit and insects that under‐ pins the aquatic food web (Lovett *et al*., 2007). Hence, canopy species like *T.arjuna* is much inevitable in this region where their absence might cause a major change in the riparian vegetation structure and composition which inturn affects the aquatic ecosystem in the region.

strength of the monsoon rainfall (Ferdin, et al., 2010). Providing clean water and improving the chemical quality of waters for both human consumption needs and ecosystem health have become important policy goals in the worldwide. Management of riparian vegetation is one strategy to achieve these goals. *Terminalia arjuna* is one of the key species in the Cauvery river to fulfill the strategy to maintain the river quality healthier. The widespread rootmat of this species protect the waterway from erosion and pollutants entering the river. It acts has a natural wall along the river bank resists soil erosion during flooding thereby avoiding the water loss due to the bank widening. Keeping increasing water scarcity and flood disaster in the lower reaches during monsoon, conservation and management of *Terminalia arjuna* in the upper reaches helps to reduce flood velocities and increase the further flow towards lower reaches,

Protection of Riparian Habitats to Conserve Keystone Species with Reference to *Terminalia arjuna* – A Case Study…

http://dx.doi.org/10.5772/58355

105

We thank University Grant Commission for providing financial assistance, Karnataka State Forest Department in for extending the permission to carry out the studies and helping in field

thereby maintaining the river water healthier.

, C. Sunil and R.K. Somashekar

Department of Environmental Sciences, Bangalore University, Bangalore, India

[1] Amitha Bachan, KH. 2003. *Riparian Vegetation along the middle and lower zones of the Chalakkudy River*, Kerala, India. Limnological Association of Kerala, Iringalakkuda.

[2] Baskaran, N., Senthilkumar. K and Saravanan, M. 2011. A new site record of the Grizzled Giant Squirrel Ratufa macroura (Pennant, 1769) in the Hosur forest divi‐ sion, Eastern Ghats, India and its conservation significance. Journal of Threatened

[3] Blom, CWPM., Bogemann, GM., Laan, P., van der Sman, A.J.M., van de Steeg, H.M. and Voesenek, LACJ. 1990. Adaptation to flooding in plants from river areas. Aquat‐

\*Address all correspondence to: nagenvi@gmail.com

**Acknowledgements**

work.

**Author details**

B.C. Nagaraja\*

**References**

Taxa 3(6): 1837–1841.

ic Botany 38: 29 - 47.

canopy of *Terminalia arjuna* species. **Figure 6.** A and B. Seedlings of *Syzygium cumini*, *Ixora bracheata*, *Madhuca latifolia* and *Dalbergia latifolia* growing in area under canopy of *Terminalia arjuna* species.

Figure 6. A and B. Seedlings of *Syzygium cumini, Ixora bracheata, Madhuca latifolia* and *Dalbergia latifolia* growing in area under

#### generation of electricity (Varunprasath and Daniel, 2010). Over 90% of the river water is abstracted for irrigation. Population density in Cauvery is perhaps among the highest in the world (350 people/ km<sup>2</sup> ; Smakhtin et al., 2006) **11. Social significance of** *Terminalia arjuna* **in Cauvery riverine ecosystem**

The primary uses of Cauvery river are providing water for irrigation, household consumption, industries and the

indicating that potential for human disturbance is inevitable along the basin. The watershed regions of the Cauvery

**Social significance of** *Terminalia arjuna* **in Cauvery Riverine ecosystem** 

river is strongly affected by water stress in recent years (Ferdin, et al., 2010). Besides meeting industrial and agricultural needs, drinking water demands from the two major urban centres namely Bangalore (6th largest city in India) and Mysore with a millions population is increasing at an faster rate. The river being completely dependent on the monsoon for replenishment, the amount of water the Cauvery can provide to the various users varies with the fluctuating strength of the monsoon rainfall (Ferdin, et al., 2010). Providing clean water and improving the chemical quality of waters for both human consumption needs and ecosystem health have become important policy goals in the worldwide. Management of riparian vegetation is one strategy to achieve these goals. *Terminalia arjuna* is one of the key species in the Cauvery river to fulfill the strategy to maintain the river quality healthier. The widespread rootmat of this species protect the waterway from erosion and pollutants entering the river. It acts has a natural wall along the river bank resists soil erosion during flooding thereby avoiding the water loss due to the bank widening. Keeping increasing water scarcity and flood disaster in the lower reaches during monsoon, conservation and management of *Terminalia arjuna* in the upper reaches helps to reduce flood velocities and increase the further flow towards lower reaches, thereby maintaining the river water healthier. The primary uses of Cauvery river are providing water for irrigation, household consumption, industries and the generation of electricity (Varunprasath and Daniel, 2010). Over 90% of the river water is abstracted for irrigation. Population density in Cauvery is perhaps among the highest in the world (350 people/ km2 ; Smakhtin et al., 2006) indicating that potential for human disturbance is inevitable along the basin. The watershed regions of the Cauvery river is strongly affected by water stress in recent years (Ferdin, et al., 2010). Besides meeting industrial and agricultural needs, drinking water demands from the two major urban centres namely Bangalore (6th largest city in India) and Mysore with a millions population is increasing at an faster rate. The river being completely dependent on the monsoon for replenishment, the amount of water the Cauvery can provide to the various users varies with the fluctuating

**Acknowledgement:** We thank University Grant Commission for providing financial assistance, Karnataka State

Forest Department in for extending the permission to carry out the studies and helping in field work.

*1.* Amitha Bachan, KH. 2003. *Riparian Vegetation along the middle and lower zones of the Chalakkudy River, Kerala, India*. Limnological Association of Kerala, Iringalakkuda.

conservation significance. *Journal of Threatened Taxa* 3(6): 1837–1841.

2. Baskaran, N., = Senthilkumar. K and Saravanan, M. 2011. A new site record of the Grizzled Giant Squirrel *Ratufa macroura* (Pennant, 1769) in the Hosur forest division, Eastern Ghats, India and its

References

strength of the monsoon rainfall (Ferdin, et al., 2010). Providing clean water and improving the chemical quality of waters for both human consumption needs and ecosystem health have become important policy goals in the worldwide. Management of riparian vegetation is one strategy to achieve these goals. *Terminalia arjuna* is one of the key species in the Cauvery river to fulfill the strategy to maintain the river quality healthier. The widespread rootmat of this species protect the waterway from erosion and pollutants entering the river. It acts has a natural wall along the river bank resists soil erosion during flooding thereby avoiding the water loss due to the bank widening. Keeping increasing water scarcity and flood disaster in the lower reaches during monsoon, conservation and management of *Terminalia arjuna* in the upper reaches helps to reduce flood velocities and increase the further flow towards lower reaches, thereby maintaining the river water healthier.
