Frequency and Abundance of Sparganium Erectum L. and Trapa Natans L

International Journal of Advanced Science and Technology Vol. 29, No. 11s, (2020), pp. 3284-3289

Frequency and abundance of Sparganium erectum L. and Trapa natans L. (macrophytes) altered by bird foraging in Hokersar wetland, Kashmir

Suzana Bashir1, 1. Centre of Research for Development, University of Kashmir, Hazratbal, J&K, India Azra N Kamili2, 2. Centre of Research for development, University of Kashmir, Hazratbal, J&K, India Manzoor A Shah and Humera Imtiyaz3 3. Deptt of Botany, University of Kashmir, Hazratbal, J&K, India Corresponding author: Suzana Bashir

Abstract Hokersar wetland in Kashmir, Himalaya hosts a large number over-wintering waterbirds as well as summer migratory and resident birds. All these birds largely depend on the macrophytes growing in the wetlands for nest building, for cover during breeding, moulting, preening and for food. High concentrations of waterbirds in wetlands are known to affect ecosystem dynamics, yet very few studies have examined their effects on the dynamics of macrophytes. In the present study two aquatic macrophytes, Sparganium erectum L and Trapa natans L typical of wetlands and eutrophic lakes, were taken into consideration for their use by the birds inhabiting the wetland. Sparganium erectum is found growing in shallower waters while as Trapa natans thrived well in open deeper waters. Water birds were observed to depend on leaves, roots and seeds of the two plants and had an impact on the population dynamics of these plants. It was also observed that nutrient loading resulted in gregarious growth of these macrophytes and in turn waterbirds reduced the biomass and also reshaped the vegetation composition of the wetland. Our data support the view that waterbirds may paly crucial role in the sustenance of certain plant species with potential consequences for the functioning of the system as a whole. The fact that bird herbivory can have a large impact on macrophyte biomass and can facilitate a regime shift, so it is implied that the presence of waterfowl should be taken into account in the estimation of critical loadings to be used in water quality management.

INTRODUCTION

Macrophytes can influence the aquatic ecosystems in multiple ways and mediate biotic interactions.( Reviewed in Carpenter and Lodge., 1986). Aquatic vegetation provides food and refuge for waterbirds (Bartodzeij and Weymouth 1995). Petr (2000) was of opinion that aquatic macrophytes are of significance as a link in food chain after studying the interaction of macrophytes with other organisms in inland waters. Engelhardt, et. al (2001) studied effects of macrophyte species richness on wetland ecosystem functioning and services and concluded that management of wetlands and reviving wetland species might sustain functioning of wetlands. In shallow lakes, bird herbivory lowered macrophytic biomass as a result clear water state of the lake was changed to turbid water state (Alteva et al 2016). In most of the wetlands just a few, one or two macrophytes dominate and these macrophytes provide habitat to microbial species and create conditions appropriate for thriving of wide array of flora and fauna (Viaroli P et al 2016).

Aquatic plants contribute to maintaining key functions and related biodiversity in freshwater ecosystems, and to provide the needs of human societies. The way the ecological niches of macrophytes are determined by abiotic filters and biotic ones is considered. A simple, broadly applicable model of the distribution of growth forms according to abiotic filters is proposed. Macrophytes contribute to maintaining key functions and related biodiversity in freshwater ecosystems, and to provide the needs of human societies. Wetlands are known to invasion by plant species after fluctuations in the hydrologic regime, leading to changes in macrophytic community structure and affect the ecosystem health and function. In this paper ecology and control of two

International Journal of Advanced Science and Technology Vol. 29, No. 11s, (2020), pp. 3284-3289 macrophytes Trapa natans a native aquatic plant species and Sparganium erectum an invasive wetland plant species thriving in Hokersar wetland is investigated.

Trapa natans L is a rooted, aquatic, annual plant seen floating on water surface. The seeds are dispersed to long distances by moving currents and waterfowl. Now a days it is considered as a rare plant in Europe and an invasive species in North America, whereas it has no significant threat in Asia and Africa although wetlands are in great risk. Its gregarious growth can cause competition for nutrients and space and its decomposition might contribute to lower levels of dissolved oxygen in shallow water. In the present study the plant was found growing well in the open water areas of the wetland. It was a dominant plant with of frequency of 54% and abundance of 7.54. The plant emerged in the open water areas of the wetland in May and lasted till December. Maximum frequency was recorded during the months of July and August. The flowering was observed during May and June while as fruit and seed set was seen during July and August. Seeds fall in water, sink and form new plants in the next spring season.

Sparganium erectum L is a perennial rhizomatous semi-terrestrial plant with roots permanently under water. It is an invasive species in our lakes and wetlands. It grows from slender rhizomes with slender terete stems. Branched Bur-reed grows to a height of about 1.5m. The leaves and corm die back over the winter, being replaced from the tip of remaining rhizomes and the leaves begin to grow in April. Maximum frequency and abundance was witnessed during major part of its growing season. The plant flowers during the months of June -July and three seeded achene fruits are developed in July and August. Achenes fall in water, sink and form new plants

Materials and methods

Two sites with different abundance were selected for estimation of standing biomass of the two macrophytes from March 2017 -2018 to October 2017-2018. Abundance, frequency and biomass was calculated following Downing and Anderson 1985. The feeding behaviour of birds both breeding and over-wintering in the wetland was observed.

Results

Common Moorhens were observed to uproot plants of Sparganium erectum at the juvenile stage and feed on the rhizome and soft tender leaves. The Common Moorhens and Purple Moorhens used the leaves of Sparganium erectum for nest building. The winter migrants ducks, geese, pintails, teals and shelducks on their arrival in the wetland fed on the seeds of this plant species. The Purple Moorhens were seen feeding on the nuts of Trapa natans. In the month of September the overwintering birds i.e., ducks and geese arrive in the wetland in large numbers and they feed on the leaves and nuts of Trapa natans. Injuries to plants, their leaves and stem could be observed due to bird herbivory. Biomass difference was significant between the areas where the plants grew in abundance but were more grazed by the birds and the areas where the plants were less abundant and grazing by birds was low. The grazing of birds in certain areas of the wetland was less due to human disturbances.

Table 1; Biomass in different abundance degrees as recorded from March2017-October 2017.

Highly Abundant Not so Abundant Rel abundance 90%-95% Rel Abundance 40%-50% Trapa natans

International Journal of Advanced Science and Technology Vol. 29, No. 11s, (2020), pp. 3284-3289

March 12.7±3.0 8.2±2.5 April 16.8±4.9 9.5±1.3 May 24.2±5.5 15.0±2.1 June 31.3±2.3 18.2±1.0 July 50.1±2.0 23.0±2.5 August 98.8±3.2 30.5±5.2 September 61.2±1.3 26.2±2.1 October 26.8±2.5 18.5±3.0

Sparganium erectum March 521 .0 ±8.3 282.2 ±5.1 April 846.4 ±4.3 631.5 ±3.8 May 1632.6 ± 3.0 1202.4 ± 6.6 June 2430.5 ±5.6 1853.5±3.8 July 2452.3 ±3.8 1899.5 ±5.3 August 2448.2 ±4.9 1920.2±12.2 September 2392.4± 9.5 2003.1 ±5.8 October 1802.5± 5.5 1389.8 ±2.3

Fig. 1: Total Biomass in gms m² of Trapa natans a s recorded from two sites having different abundance degrees from March 2017 to October 2017

H A is Highly abundant and N S A is Not so abundant

Fig 2:Total biomass in gms m² of Sparganium erectum as recorded from recorded from two sites having different abundance degrees from March 2017 to October 2017.

International Journal of Advanced Science and Technology Vol. 29, No. 11s, (2020), pp. 3284-3289

Fig 3: Frequency and Abundance of Sparganium erectum and Trapa natans as recorded from Hokersar wetland during different study periods.

Discussion

Frequent floods, turbidity of water, nutrient input and fluctuating water levels in the wetland together with human impact affect growth and distribution of macrophytes. Moss.B et al 2013 found that increased N loading reduces plant biodiversity, changes the structure and is associated with eventual loss of macrophyte communities.

Sparganium erectum was a dominant plant with a maximum frequency of 60% in the wetland in the last decade but now it is categorised as a frequent plant with a frequency of 38%. Trapa natans was categorised as a frequent plant species with a frequency of 20% during the study by Bashir.S 2003, and now it has a frequency of 54%. The abundance values recorded during the present study was 6.84 and 7.54 for Sparganium erectum and Trapa natans respectively and the abundance values recorded as reported by Bashir.S 2003 were 8.35 for Sparganium erectum and 3.0 for Trapa natans. According to Kumar and Pandit 2008, Sparganium erectum growing in the wetland exhibited a

International Journal of Advanced Science and Technology Vol. 29, No. 11s, (2020), pp. 3284-3289 frequency of 61.93, and an abundance of 8.96 and Trapa natans thrived with a frequency of 45.5 and an abundance of 4.08.

Khan (2004 and 2009) and Pandit (1984) Kumar and Pandit (2008) have reported that the Sparganium erectum is the dominant specie in the Hokersar wetland , Trapa natans has been reported to grow in the wetland. The macrophytic biomass fluctuated from 35 - 1100 gm ̄² showing considerable site-specific variation. Khan and Shah (2010) reported highest biomass value from the marshy littoral regions while as relatively low values were obtained from open water areas of the wetland. The biomass showed an evident increase from the beginning of spring (March - May) reaching minimum during winter months. Sparganium erectum was reported as the dominant emergent macrophyte and Salvinia natans was the dominant free floating macrophyte reported from the open water areas of Hokersar wetland (Khan and Shah 2010). The vegetation composition in the wetlands is usually quite diverse (Khan et al.2004), occurrence of only 47 species presently in the Hokersar wetland, against 67 species reported by Kaul and Zutshi (1989), indicates a declining trend in aquatic biodiversity. The decrease in biodiversity may be due to accelerated eutrophication, and anthropogenic pressures. Gangoo and Makaya (2000) reported a decrease in macrophyte plant species of Hokersar. Zutshi 2014, water of Hokersar is turbid for major part of the year, having an impact on the composition and structure of plant communities and in turn on the food availability to migratory birds. Plants at the extremes of an environmental gradient survive because of their great ecological tolerance to such environmental conditions. The life-form gradient of vegetation is maintained by competitive exclusion and displacement. Lolu et al 2016, found that emergent macrophytes like Sparganium erectum, Phragmites australis and Typha angustata growing in Hokersar wetland witnessed considerable changes in biomass during different seasons. Over the years, Hokersar wetland witnessed a shift in the vegetation structure to the extent some economically important plant species (Nelumbo nucifera, Euryale ferox and Acorus calamus) have all-together disappeared.

Moderate disturbances (by floods or drawdowns) decrease biotic interactions in aquatic plant communities and as a consequence favour biodiversity and decrease successional rate. Although Baschuk.M.S, et al (2012) found that temporary water level changes influenced the growth of emergent macrophytes but then it had no effect on the spatial arrangement of vegetation cover and also found that vegetation cover in high water wetlands remained unchanged throughout the study period. Free‐floating and tall species with floating leaves are most competitive for light, and usually dominate macrophyte communities when nutrient levels in the water are sufficiently high. Yallop ,et al (2004) suggested that overwintering water birds have the potential to remove a large proportion of the above ground macrophyte standing crop in the lagoons

In the framework of global change, eutrophication of freshwaters, together with decreases in natural disturbance regimes in river floodplains, increases in groundwater abstraction and the increase of temperature may all contribute in decreasing macrophyte biodiversity. Trapa natans can become an abnoxious weed in the wetland but bird foraging has kept it in check. Bakker E.S 2013, is of the view that the disturbances such as herbivory can limit dominance by eutrophic species and improve macrophyte diversity. According to Yallop, et al 2004 overwintering waterbirds have the potential to remove a large proportion of the above ground macrophyte standing crop in the lagoons and also observed that changes in macrophyte composition may be partially linked to bird herbivory. In a study in American wetlands the grazing of below ground biomass was significantly reduced by mute swan (Stafford et al ,2012). Tatu, et.al (2007) found a negative impact of mute swan on aquatic plant height and shoot density in Chesapeake Bay. Selective foraging by birds works in tandem with the anthropogenic pressures changing the plant community in Hokersar wetland (Bashir et al 2003).

Conclusion

Trapa natans can become an abnoxious weed in the wetland but bird foraging has kept it in check. Sparganium erectum which was dominant in Hokersar during the last decade is less abundant and less frequent and the frequency of Trapa natans is on surge. Hydrology has a significant impact on diversity and abundance of various floating leaf macrophytes and emergent wetland plants. The

International Journal of Advanced Science and Technology Vol. 29, No. 11s, (2020), pp. 3284-3289 changing community features of macrophytes in wetlands is temporal and there can be various factors responsible for the variations. In this shift in the community status of the macrophytes , the major reason can be attributed to bird foraging.

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