CHNAES-00631; No of Pages 8 Acta Ecologica Sinica xxx (2018) xxx
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Determination of resource based stocking density of wild ungulates living in the floating meadows of Keibul Lamjao National Park, India Chongpi Tuboi, Syed Ainul Hussain ⁎ Department of Landscape Level Planning and Management, Wildlife Institute of India, Post Box # 18, Chandrabani, Dehra Dun 248001, Uttarakhand, India
a r t i c l e
i n f o
Article history: Received 8 April 2018 Received in revised form 19 November 2018 Accepted 20 November 2018 Available online xxxx Keywords: Stocking density Forage biomass Floating meadows Eld's deer Carrying capacity
a b s t r a c t The stocking density of the globally threatened Eld's deer (Rucervus eldii eldii) and hog deer (Axis porcinus), living in the floating meadows of Keibul Lamjao National Park, India, were derived from the forage demand of each species and the availability of forage biomass in the meadows. The biomass production was estimated by harvesting the above-ground biomass every month for 2 years from 432 plots of size 1 m × 1 m that were protected by ungulate-proof enclosures. The actual intake of the ungulates was estimated from the percentage of dry matter consumed for each food plant species through micro-histological analysis. The populations of Eld's deer and hog deer that the meadows can support were calculated on the basis of the consumable dry matter available in the park, considering the variable thickness of the floating meadows. The estimated overall stocking densities of Eld's deer and hog deer were 0.141 ± 0.06 and 0.265 ± 0.12 individuals ha−1 or 15,581.54 ± 1171.6 kg of ungulate biomass. The stocking density varied significantly with meadow type for both the species, being higher for thick meadows. The best available areas of the park having 864.29 ha, can support 170.41 ± 11.4 Eld's deer and 319.36 ± 22.94 hog deer or 17,356.38 ± 912.02 kg of ungulate biomass with a maximum of 173.6 ± 4.21 Eld's deer and 325.46 ± 9.45 hog deer or 17,684.56 ± 697.3 kg of ungulate biomass in the monsoon season. The thin meadows with an area of 732.34 ha can support another 119.37 ± 12.78 and 225.44 ± 23.88 Eld's deer and hog deer respectively or 12,201.35 ± 922.74 kg of ungulate biomass. In similar resource constraint habitat, this study will be helpful in determining the optimal stocking density for the science based management of rangelands, especially for the conservation of wild grazers. © 2018 Ecological Society of China. Published by Elsevier B.V. All rights reserved.
1. Introduction Determining the correct stocking rate of a rangeland has been one of the basic problems faced by managers [1]. Timely and accurate estimation of biomass production and forage quality during the grazing season is important for managers in determining the appropriate stocking rate and pasture utilization. The phytomass or standing crop biomass is most often measured to set stocking rates or assess the capacity of an ecosystem to support grazing animals. Most decisions regarding adjustment of stocking rates are made at the end of the growing season [1]. The standing crop is estimated and the animal numbers are adjusted so that there is minimal residue (dry matter) when growth is initiated in the following year [1,2]. “Ecological carrying capacity” is usually defined as the maximum number of animals a defined area can support in relation to available resources [2,3]. For any estimate of long-term grazing capacity, it is important to know the average forage production of a range over a series of years, as the production tends to fluctuate considerably between years ⁎ Corresponding author. E-mail address:
[email protected] (S.A. Hussain).
in response to changing climatic conditions. On ranges dominated by perennial forage, a 30% downward adjustment of the standing crop at the end of the growing season should give a reasonable estimate of the average long-term forage production if the growing conditions are considered good (N125% of annual average precipitation), and an upward adjustment of 30% should work well when the growing conditions are poor (b70% of average annual precipitation). In years, when the precipitation deviates by 50% or more from the average, reliable estimates of the grazing capacity will not be possible in most cases [4,5]. The forage demand can be measured as the amount of forage consumed per day and is often standardized by being expressed in animal-units. In contrast to seasonal livestock grazing, management of forage for wild ungulates requires the forage to be characterized at the scale of “animal-unit-years” as the animals are present on the landscape for a full 12-month period without supplementation. As such, monthly or seasonal diets and intakes of wild ungulates are summed to determine the annual demand. Despite the fact that most wild ungulates co-exist in multispecies systems [6,7], there is limited information available on the concurrent daily intakes of sympatric species [8]. In the absence of predation in natural communities, populations of herbivores are governed by food supply, and the balance between
https://doi.org/10.1016/j.chnaes.2018.11.008 1872-2032/© 2018 Ecological Society of China. Published by Elsevier B.V. All rights reserved.
Please cite this article as: C. Tuboi and S.A. Hussain, Determination of resource based stocking density of wild ungulates living in the floating meadows of..., Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2018.11.008
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C. Tuboi, S.A. Hussain / Acta Ecologica Sinica xxx (2018) xxx
Fig. 1. Map showing location of Loktak Lake and the land use land cover type of Keibul Lamjao National Park, India.
herbivores and the carrying capacity of the environment is secured by auto-regulation mechanisms [9]. Specialization of ungulate species to exploit certain components of the food supply enables optimal and economic utilization of all accessible food sources of a landscape [10]. Reliable estimates of the daily dry matter intake of ungulates are central to assessing the carrying capacity and determining animal-unit equivalents [11]. In a multispecies system, the dry matter intake varies among species, but a generalized value can be determined for a species from its digestive capacity and body size [12]. The wild ungulates of Keibul Lamjao National Park (KLNP), India, live on floating meadows, which cover around 65% of the park; the rest of the area consists of open water and small hillocks. The floating meadows are made up of a heterogeneous mixture of dead and decaying plant material. The primary colonizers of the meadows are species such as Salvinia, Azolla and Eichhornia. These are followed by short grasses such as Cyperus, Polygonum and Capillipedium species. Subsequently, tall grasses such as Zizania latifolia, Phragmites karka and Saccharum spontaneum colonize the meadows. The floating meadows vary in thickness and float with about one-fifth of their thickness above water and four-fifths under water [13,14]. In the past, these meadows used to settle down during the summer and get replenished with nutrients and soil particles from the lake bed, and float again
when the water level rises during monsoon. The construction of the Ithai barrage, in the downstream stretch of the Manipur River has altered the natural hydrological regime of the lake. The meadows are now continuously floating even during summer and are not replenished, and losing soil particles, which enhance rhizome formation, from the bottom. This has led to thinning of the meadows [15–17]. The park is surrounded by human habitation and hence is not connected to the surrounding landscape. Heavy anthropogenic influences in the surrounding areas, have aggravated these impacts and affected the water quality and hydrological regime of the lake significantly [13,15,17]. The KLNP is located in the south-eastern part of the Loktak Lake. The park has great conservation significance as in addition to being one of the few floating national parks of the world, it is also the last remaining natural home of the globally threatened Eld's deer (Rucervus eldii eldii) in India. To support the weight of Eld's deer and the hog deer (Axis porcinus), the thickness of the floating meadows needs to be N1 m. Hence, the thinning of the floating meadows has serious implications for the conservation of these animals [18,19]. In addition, the floating meadows aid in maintaining the water quality of the lake by acting as a biological sink for nutrients. There is no predator in the park that preys on Eld's deer. However, the uniqueness of the habitat and its
Table 1 Annual forage demand of Eld's deer and hog deer in Keibul Lamjao National Park, India.
Eld's deer Hog deer
Body weight W (kg)
Percent Body weight DDI
Daily intake (kg)
Annual forage demand FD = W × DDI × 365 (kg)
110 ± 5.4 50 ± 2.04
2.5 2.5
2.75 1.25
1003.75 456.25
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4000
2.1. Determination of forage biomass available to wild ungulates To estimate the forage biomass available to the wild ungulates, following Milner and Hughes [22], the forage species were harvested every month for 24 months from 18 quadrats (size, 1 m × 1 m) that were protected by ungulate-proof enclosures. Since the date of harvesting can affect the accuracy of forage biomass due to seasonal changes in the species composition, the phenological stage, herbage accumulation below the grazing horizon and accumulation of dead material [23], the plots were harvested on a fixed day each month. The harvested plants were sorted by species and placed in labelled paper bags. The bags containing vegetation were weighed using a pan balance. They were oven dried at 80 °C and weighed again to determine the dry weight. The difference between the fresh and oven-dried weight is the total biomass of a species. The actual portion of the plant consumed was determined from field observations, and the actual biomass was quantified following Chapman et al. [24]. The percentage of a plant part utilized was determined, by comparing the quantity utilized from stalks of feeding sign observed in the field with entire stalks in the undisturbed control plots. The biomass of an individual species after feeding, as recorded from field
86.7%
2500
73.68%
2000 1500 1000
26.32% 13.28%
500 0 Mean annual
Forage
Extracted
Available
Utilized
Left unused
Fig. 2. Percentage of annual forage biomass (g m−2) available to the wild ungulates in Keibul Lamjao National Park, India.
observations was subtracted from the total biomass of the food plants in the control plots (n = 6) to calculate the biomass consumed. 2.2. Stocking density To determine how many deer the floating meadows can support (stocking rate), two important questions were addressed: (a) How much forage does a particular species consume? (b) How much forage is available? The stocking density was calculated from an estimate of the annual production of consumable biomass, linked to the animal's requirements. Ruminants consume about 2% of their body weight per day as dry matter. This is an average value across periods when the forage is dormant and when it is actively growing [1]. It has been suggested that if a piece of land is to be grazed only during the dormant period, when the forage is of poor quality, the daily forage demand is 1.5% of the body weight; during active growth, when the quality of the forage is good, the demand is 2.5% [8]. Since the park has good quality forage [15], the forage demand for the present study was taken as 2.5% of body weight. On the basis of review of literature, the body weight of an adult Eld's deer was considered to be 110 ± 5.4 kg [25–28] and that of an adult hog deer was considered to be 50 ± 2.04 kg [29-32] for the present study. 2.3. Biomass available to ungulates The percentage utilization of each forage species was determined on the basis of 20 forage species used by Eld's deer and the hog deer [15]. The biomass available to the ungulates is the total biomass of the forage plants (g m−2) minus the biomass of non-palatable species and biomass extracted by local communities. For each ungulate species, the forage intake (kg ha−2) and percent dry matter in the diet were summed to 40
35.4%
35 % Contribution
2. Methods
77.95%
3000
1.1. Study area The present study was conducted in the floating meadows of KLNP, located in the Barak-Chindwin River Basin. The park lies between latitudes 24°26′ N and 24°31′ N and longitudes 93°49′ E and 93°52′ E, in the south-eastern fringes of the Loktak Lake, Manipur (Fig. 1). KLNP is the only natural home of the globally threatened Eld's deer, Rucervus eldii eldii (McClelland, 1842), locally known as ‘sangai’. The park received national and international attention when Loktak Lake was declared a site of international importance on 23 March 1990, under the Ramsar Convention. The park occupies an area of 40 km2, of which 26 km2 is under a thick and contiguous mat of floating meadows and 14 km2 is open water and hillocks [15,17]. The presence of floating meadows covered with vegetation is a characteristic feature of Loktak Lake. These floating meadows, locally known as phumdis, are of all sizes and thicknesses. On the basis of the meadow thickness, the park has been divided into the western thick meadow zone, eastern thin meadow zone, northern open water and very thin meadow zone. The maximum thickness recorded is 8 ft [20]. Low temperatures and heavy dew characterize the climatic conditions of the park during night time from November to February. Frost occurs in early morning hours and during winter nights, from December to January. The temperature ranges from a maximum 34.4 °C to a minimum of 1.7 °C. The temperature rises from March to May. Heavy rainfall occurs from June to September, and there is little rainfall from December to February. The annual rainfall is 1460 mm. The humidity is highest in August, measuring up to 81%, and is least in March, at 49%. A total of 185 plant species representing 50 families and 121 genera have been recorded. The family Poaceae is the dominant family, followed by Cyperaceae and Asteraceae [21].
100%
3500 Biomass g m¯²
continued deterioration, along with the critically low numbers of Eld's deer and the hog deer in the park, demand immediate management intervention. There is a need to study the carrying capacity of this unique ecosystem for the long-term conservation of these globally threatened species. The standing crop biomass is the parameter most often measured to set stocking rates or assess an ecosystem's capability to support grazing animals. The paper aims to determine stocking densities for the wild ungulates of the park, based on the capacity of plant resources to support them. Since each meadow type has its own plant community, the availability of resources in each habitat type was used for setting stocking densities in that habitat.
3
30 25 20 15 10
14.1%
12.5% 9.2%
8.4%
7.9%
7.4%
5.1%
5 0
Species Fig. 3. Percentage contributions of individual species to forage biomass in Keibul Lamjao National Park, India.
Please cite this article as: C. Tuboi and S.A. Hussain, Determination of resource based stocking density of wild ungulates living in the floating meadows of..., Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2018.11.008
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% Plant part consumed
4
50 45 40 35 30 25 20 15 10 5 0
45.8% 40.6% 37.3%
37.3% 32.3% 32% 31.9% 31.5% 29.7% 29.6% 24.5% 22.1%
21.3% 20.4% 20.8%
18.2%
17.9% 16.4% 10.6% 6.3%
Species Fig. 4. Species-wise percentage of plant part consumed by wild ungulates in Keibul Lamjao National Park, India.
obtain annual totals. The total usable forage biomass available for utilization by the wild ungulates was calculated using the equation developed by Holechek [1]: TFAe ¼ ðFPÞ−ðPBe Þ
ð1Þ
where, TFAe = total forage (total biomass of 20 forage species, in kilograms) available for grazing after human extraction, FP = forage production (of 20 forage species, in kilograms per hectare) in the control plot and PBe = percentage of biomass extracted by humans. The forage available to Eld's deer and the hog deer in 864.29 ha of thick meadows was calculated as. FA ¼ TFAe PP A
ð2Þ
where FA = actual forage (in kilograms) available for ungulates in 864.29 ha, TFAe = total forage (in kilograms) available for grazing after human extraction, PP = percentage of plant part utilized by the ungulates and A = area (in hectares). The actual intake by ungulates was determined from the percentage of dry matter consumed of each food plant species using the microhistological analysis [33]. Five slides were prepared separately for each food plant species for Eld's deer and hog deer. Twenty microscopic fields per slide were observed, resulting in 100 observations for each species [15]. The dry weight consumed was calculated from the density and relative density of each observation. Fragments recognized as epidermal tissue were noted as positive evidence for the presence of a plant species at a location in the slide. Frequency percentages were tabulated for each species in the mixture. Each frequency percentage was converted to a particle density per field of observation in the slide using the table developed by Fracker and Brischle [34], and the relative density, expressed as a percentage, of each species in the mixture was calculated. The relative density of a species was used to estimate the percentage dry weight of that species in the mixture. Regression equations that express the relationship between the estimated percentage
dry weight (X) and the actual percentage dry weight (Y) were developed: 0 Eld s deer : Relative density 0:811 þ 1:179; R2 ¼ 0:906; pb:05 Hog deer : Relative density 0:831 þ 0:099; R2 ¼ 0:871; pb:05 Using these equations, the percentage dry weights consumed by Eld's deer and hog deer were calculated. Thus, CDM ¼ ðFAÞ–ðDWÞ
ð3Þ
where CDM = consumable dry matter in individual meadow types: FA = forage available after extraction, DW = percentage dry weight consumed The forage dry matter consumption in grams per animal per year is calculated using the following equation given by Holechek [1]: FD ¼ W DDI 365
ð4Þ
where FD = forage demand (kg) per animal per year, W = weight of animal (kg) [Eld's deer, 110 ± 5.4 kg; hog deer, 50 ± 2.04 kg], DDI = daily dry matter intake (i.e., 2.5% body weight), 365 = number of days the pasture is grazed (Table 1). The population of Eld's deer and hog deer that the meadows can support was estimated on the basis of the consumable dry matter available in the park under different meadow conditions as, EP ¼ CDM=FD ½Equation ð3Þ=Equation ð4Þ
ð5Þ
where EP = estimated population, CDM = consumable dry matter in a particular meadow type or hard ground, FD = forage demand (kg) per animal per year.
Table 2 Extents of floating meadows of different thickness in Keibul Lamjao National Park, India. Different meadow types
Thick Thin Very thin
Range of thickness of meadows (cm)
N120 60–120 b60
Total points sampled
655 555 480
Mean thickness (cm)
163.01 105.58 47.44
Support for Eld's deer
Good Fair poor
% Area
38.76 32.84 28.4
Total area of meadows (km2)
22.3 22.3 22.3
Extent of different types of meadows (km2)
(ha)
8.64 7.32 6.33
864.29 732.34 633.37
Please cite this article as: C. Tuboi and S.A. Hussain, Determination of resource based stocking density of wild ungulates living in the floating meadows of..., Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2018.11.008
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Table 3 Percent forage available, usable biomass and percentage consumable dry matter for Eld's deer and hog deer in thick meadows (864.29 ha) across the seasons of the study years in Keibul Lamjao National Park, India. Year
2008–09
2009–10
Season
Summer Monsoon Winter Overall Summer Monsoon Winter Overall
% plant part utilized
Usable biomass (kg)
27.52 ± 2.7 27.52 ± 2.7 27.18 ± 2.9 27.52 ± 2.7 29.37 ± 2.7 29.37 ± 2.7 29.37 ± 2.7 27.04 ± 2.6
3,216,683.05 2,983,008.38 2,263,929.00 2,811,236.32 2,692,871.56 2,714,715.73 2,035,837.53 2,425,382.9
The stocking density of the area was calculated using the equation. SD ¼ EP=A; ½Eq:ð5Þ=area
ð6Þ
where SD = stocking density, EP = estimated population, A = area of a particular meadow type or hard ground. The ungulate biomass was calculated using the equation. UB ¼ SD A W ½Equation ð6Þ area weight of animal
ð7Þ
where UB = ungulate biomass, SD = stocking density, A = area of a particular meadow type or hard ground, W = weight of animal (kg) [Eld's deer, 110 ± 5.4 kg; hog deer, 50 ± 2.04 kg]. 2.4. Floating meadow thickness The entire park was divided into 1000 m × 1000 m grids. In each grid, two or three 500 m long transects were laid, and thickness of the meadow was measured every 50 m using marked bamboo poles. The thickness was measured at 1659 points, and the extent of the meadows was derived from the total area of the meadows within the park, which was estimated to be 2230 ha [19]. The meadow thicknesses were divided into three types depending on the ability to support the weight of Eld's deer. The area covered by each thickness type was calculated from the transect data. The stocking density of the park was calculated across the seasons and meadow types on the basis of the consumable forage available for use by Eld's deer and hog deer in each season and meadow type during the two study years. 3. Results 3.1. Overall forage biomass Of the 41 plant species recorded in the enclosures, 20 were identified as forage species on the basis of micro-histological analysis of pellets of Eld's deer and hog deer [15]. The total annual biomass production of these species was 3545.99 ± 198.2 g m−2 (n = 41 species, 24 months), and the forage biomass was 2764.26 ± 139.93 g m−2
% Consumable dry matter Eld's deer
hog deer
6.74 ± 1.8 6.26 ± 1.7 6.74 ± 1.8 6.26 ± 1.7 7.11 ± 1.9 7.11 ± 1.9 7.11 ± 1.9 6.21 ± 1.6
5.73 ± 1.7 5.38 ± 1.6 5.73 ± 1.7 5.38 ± 1.6 6.15 ± 1.7 6.15 ± 1.7 6.15 ± 1.7 5.16 ± 1.5
(n = 20 species, 24 months), which is 77.9% of the total biomass. Of the total forage biomass available, 13.3% (367.65 ± 148.25 g m−2) was extracted by the local communities. Thus, the mean annual forage biomass available to the wild ungulates was only 86.7% (2396.613 ± 315.97 g m−2) of the total forage biomass, out of which an estimated 26.32% (630.79 ± 111.5 g m−2) is utilized by the wild ungulates in the park (Fig. 2). N85% of the forage biomass was contributed by Zizania latifolia, Arundo donax, Setaria spp., Capillipedium spp., Phragmites karka, Leersia hexandra and Saccharum spontaneum. Z. latifolia contributed the most to the forage biomass (35.4%, 3297.77 g m−2), followed by A. donax (12.5%, 1163.32 g m−2) and Setaria spp. (9.2%, 855.53 g m−2). The smallest contribution was that of Alternanthera philoxeroides (only 0.01%, 0.59 g m−2) (Fig. 3). Z. latifolia is an invasive plant that can re-grow even from a small rhizome. It overtops and suppresses other marginal species. The plant species with the highest part utilization was Z. latifolia, with 45.8% being utilized by the wild ungulates, followed by Oenanthe javanica (40.6%), Setaria spp. and Carex cruciata (37.3%). The plant species least utilized was Scirpus lacustris, with only 6.3% being utilized by the wild ungulates (Fig. 4). The estimated population of Eld's deer and hog deer was b100 individuals during 2006–08. 3.2. Stocking density The daily intake of the wild ungulates was calculated by considering the weight of Eld's deer to be 110 ± 5.4 kg [25–28] and that of hog deer to be 50 ± 2.04 kg [29–32]. Since ungulates consume 2.5% of their body weight daily, the annual forage demands of Eld's deer and hog deer were 1003.75 kg year−1 and 456.25 kg year−1, respectively (Table 1). The thickness of the meadows was N120 cm in 864.29 ha (thick meadows), 60–120 cm in 732.34 ha (thin meadows) and b60 cm in 633.37 ha (very thin meadows) (Table 2) [35]. The park does have a small patch of hard ground (approximately 0.58 ha), which gets submerged when the water level is high, particularly between July and November. The actual total biomass available for use in the thick meadows (864.29 ha) was greater during 2008–09 (28,11,236.32 kg) compared with 2009–10 (24,25,382.9 kg) (Table 3). The actual total biomass available for use in the thin meadows (732.34 ha) was also greater during
Table 4 Percent forage available, usable biomass and percentage consumable dry matter for Eld's deer and hog deer in thin meadows (732.34 ha) across the seasons of the study years in Keibul Lamjao National Park, India. Year
2008–09
2009–10
Season
Summer Monsoon Winter Overall Summer Monsoon Winter Overall
% plant part utilized
26.08 ± 3.1 26.08 ± 3.1 26.47 ± 2.9 26.47 ± 2.9 27.27 ± 3.1 27.27 ± 3.1 27.60 ± 2.9 27.60 ± 2.9
Usable biomass (kg)
1,791,410.18 2,647,540.49 1,882,248.01 2,201,489.44 1,723,016.24 2,441,962.91 1,348,181.81 1,915,206.37
% Consumable dry matter Eld's deer
hog deer
6.06 ± 1.7 6.06 ± 1.7 5.65 ± 1.7 5.65 ± 1.7 6.35 ± 1.8 6.35 ± 1.8 5.89 ± 1.8 5.89 ± 1.8
5.15 ± 1.6 5.15 ± 1.6 4.87 ± 1.5 4.87 ± 1.5 5.43 ± 1.7 5.43 ± 1.7 5.11 ± 1.6 5.11 ± 1.6
Please cite this article as: C. Tuboi and S.A. Hussain, Determination of resource based stocking density of wild ungulates living in the floating meadows of..., Acta Ecologica Sinica, https://doi.org/10.1016/j.chnaes.2018.11.008
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Table 5 Percent forage available, usable biomass and percentage consumable dry matter for Eld's deer and hog deer in hard ground area (58 ha) across the seasons of the study years in Keibul Lamjao National Park, India. Year
2008–09
2009–10
Season
Summer Monsoon Winter Overall Summer Monsoon Winter Overall
% plant part utilized
Usable biomass (kg)
27.49 ± 4.2 27.49 ± 4.2 27.49 ± 4.2 27.49 ± 4.2 27.49 ± 4.2 27.49 ± 4.2 25.32 ± 2.6 27.33 ± 2.9
25,989.47 52,580.19 18,536.29 34,584.54 63,712.82 36,309.4 50,115.33 48,898.85
2008–09 (22,01,489.44 kg) compared with 2009–10 (19,15,206.37 kg) (Table 4). However, the actual total biomass available for use in the hard ground area (58 ha) was greater during 2009–10 (48,898.85 kg) compared with 2008–09 (34,584.54 kg) (Table 5). The percentage dry weight consumed by Eld's deer ranged between 6.21 ± 1.6 and 7.11 ± 1.9 in the thick meadows; between 5.65 ± 1.7 and 6.35 ± 1.8 in the thin meadows and between 3.84 ± 2.4 and 5.77 ± 3.2 in the hard ground area. The percentage dry weight consumed by hog deer ranged between 5.38 ± 1.6 and 6.15 ± 1.7 in the thick meadows; between 4.87 ± 1.5 and 5.43 ± 1.7 in the thin meadows and between 4.76 ± 3.1 and 6.91 ± 4.3 in the hard ground area (Tables 3–5). The stocking density of Eld's deer was 0.156 ± 0.07 and 0.125 ± 0.06 individuals ha−1 during 2008–09 and 2009–10, respectively. The overall stocking density of the two study years was 0.141 ± 0.06 individuals ha−1. The stocking density was highest during the monsoon (0.196 ± 0.09 individuals ha−1), followed by summer (0.181 ± 0.08 individuals ha−1) and was least in winter (0.125 ± 0.06 individuals ha−1). The stocking density was highest in the thick meadows (0.197 ± 0.1 individuals ha−1), followed by the thin meadows (0.163 ± 0.02 individuals ha−1) and the hard ground area (0.039 ± 0.01 individuals ha−1) (Table 6). The stocking density of hog deer was 0.295 ± 0.14 individuals ha−1 and 0.234 ± 0.11 individuals ha−1 during 2008–09 and 2009–10, respectively. The overall stocking density for the two study years was 0.265 ± 0.12 individuals ha−1. The stocking density was highest during the monsoon (0.366 ± 0.17 individuals ha−1), followed by summer (0.344 ± 0.16 individuals ha−1) and winter (0.232 ± 0.11 individuals ha−1). The stocking density was highest in the thick meadows (0.370 ± 0.03 individuals ha−1), followed by thin meadows (0.308 ± 0.03 individuals ha−1) and hard ground (0.102 ± 0.02 individuals ha−1) (Table 6). Overall, the park can support 15,581.54 ± 1171.6 kg of ungulate biomass. The thick meadows can support 17,356.38 ± 912.02 kg of ungulate biomass while the thin meadows and hard ground area can support 12,201.35 ± 922.74 kg and 244.57 ± 34.17 kg of ungulate biomass
% Consumable dry matter Eld's deer
hog deer
5.77 ± 3.2 5.77 ± 3.2 5.77 ± 3.2 5.77 ± 3.2 5.77 ± 3.2 5.77 ± 3.2 4.61 ± 2.7 3.84 ± 2.4
6.91 ± 4.3 6.91 ± 4.3 6.91 ± 4.3 6.91 ± 4.3 6.91 ± 4.3 6.91 ± 4.3 5.22 ± 3.7 4.76 ± 3.1
respectively. Across the seasons, the park can support 17,684.56 ± 697.3 kg, 16,295.89 ± 545.31 kg and 11,925.44 ± 732.24 kg of ungulate biomass in monsoon, summer and winter respectively (Table 6). 4. Discussion Ecosystem management is emerging as the central focus for land managers [36].The importance of maintaining a reasonable balance between the ungulates and the vegetation that supports them has increased. The concept of carrying capacity was originally developed for domestic grazers and thus did not accommodate the wide variety of diets found in wild herbivores. In this study, the resource-based carrying capacity was used to determine the number of Eld's deer and hog deer that can be supported by the current rate of biomass production at KLNP. The study area has three separate types of meadows, apart from hard ground, which gets inundated for a few months in a year. The standing crop biomass of forage species in the three management units was found to be diverse [15]. The impact of the current levels of grazing on the ecological stability and secondary succession of vegetation (seasonal plant communities) of the park is not known. For managers, maintaining or enhancing the ecological stability of the vegetation that constitutes the forage resource of wild ungulate grazers is a primary concern [1,37]. A synergistic relationship does exist between the ungulate grazers, as a result of which the removal of one ungulate grazer will alter the behaviour and, or distribution of the other. Such alterations could locally decrease the stability of the plant community and increase intra-specific competition. Overstocking an area is damaging not only to the animal health and productivity but also to the environment, leading to soil erosion and nutrient pollution of water bodies [38]. Maintaining a balance between the stocking rate and the productivity of an area by estimating the carrying capacity correctly is an important step in establishing a sustainable habitat. Even though the extent of KLNP is 4000 ha, only 864.29 ha had meadows of the thickness best suited for Eld's deer; the remaining 732.34 ha was covered with meadows of thickness b120 cm, which
Table 6 Estimated stocking density (individuals ha−1) and number of individuals (in 864.29 ha) of Eld's deer and hog deer, across the meadow types, seasons and study years in Keibul Lamjao National Park, India. Parameters
Meadow type
Seasons
Years
Thick meadows Thin meadows Hard ground Summer Monsoon Winter 2008–09 2009–10 2008–10
Stocking density (individuals ha−1) Eld's deer
Total number of individuals
Stocking density (individuals ha−1) hog deer
Total number of individuals
Overall ungulate biomass (kg)
Stocking density (individuals ha−1) Sangai & hog deer
Total number of individuals
0.197 ± 0.01 0.163 ± 0.02 0.039 ± 0.01 0.181 ± 0.08 0.196 ± 0.09 0.125 ± 0.06 0.156 ± 0.07 0.125 ± 0.06 0.141 ± 0.06
170.41 ± 11.4 119.37 ± 12.78 2.27 ± 0.39 159.08 ± 1.45 173.6 ± 4.21 117.08 ± 8.97 159.6 ± 13.61 145.5 ± 18.85 152.55 ± 16.05
0.370 ± 0.03 0.308 ± 0.03 0.102 ± 0.02 0.344 ± 0.16 0.366 ± 0.17 0.232 ± 0.11 0.295 ± 0.14 0.234 ± 0.11 0.265 ± 0.12
319.36 ± 22.94 225.44 ± 23.88 5.89 ± 1.03 301.87 ± 2.48 325.46 ± 9.45 219.45 ± 17.87 301.92 ± 25.83 273.28 ± 35.85 287.65 ± 30.39
17,356.38 ± 912.02 12,201.35 ± 922.74 244.57 ± 34.17 16,295.89 ± 545.31 17,684.56 ± 697.3 11,925.44 ± 732.24 16,326.04 ± 1041.58 14,834.52 ± 1332.89 15,581.54 ± 1171.6
0.182 ± 0.041 0.201 ± 0.04 0.136 ± 0.032 0.232 ± 0.11 0.249 ± 0.11 0.158 ± 0.07 0.200 ± 0.09 0.159 ± 0.07 0.180 ± 0.08
157.34 ± 35.81 147.0 ± 31.39 7.9 ± 1.84 203.8 ± 1.81 221.59 ± 6.49 149.1 ± 11.86 204.83 ± 17.86 185.35 ± 24.12 195.11 ± 20.71
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can support the weight of Eld's deer, but this is not the best habitat. The 58 ha stretch of dry, hard ground grassland, present in the western side of the park, also plays a crucial role, especially when the park is inundated and the water level is high during the monsoon and early winter [15,16,21]. The thick meadows had the highest stocking density, followed by the thin meadows and the hard ground, which indicates that maintaining the thickness of the meadows is crucial for sustaining a steady population of Eld's deer in the park. This study shows that food is not a constraint in the park but that space seems to be a constraint. For maximum wildlife population on a land, the economic grazing or browsing capacity is therefore usually set at 70–80% of the ecological grazing or browsing capacity [39]. In the case of KLNP, only 26.32% of the total forage available to the wild ungulates is being utilized. As mentioned previously, overstocking a particular habitat can be detrimental to the ecosystem and the wild animals. By comparing the actual number of animals present on a rangeland with that recommended on the basis of the available plant resources, the overstocking can be quantified. This overstocking can be rectified by managing the wildlife selectively without disturbing the ratio of the different feeding classes [40]. In the case of KLNP, the actual number of Eld's deer and the sympatric hog deer present are far lower than the carrying capacity estimated through this study. So, there is scope for increasing the population of the wild ungulates in the park based on the availability of food resources. However, due to the thinning of the meadows, there is a constraint of space, which may in the long run have negative impacts on the Eld's deer and hog deer populations due to density-dependent factors [16]. In this study, the available forage biomass was used to estimate the population size of each ungulate species that can survive the critical period of this particular habitat [41].The results suggest that maintaining the thickness of the meadows is imperative for the long-term survival of the wild ungulates in KLNP. The analysis of the stocking density carried out in this study indicates that the concept is useful in deterministic and slightly variable environments. Measurement of stocking density is an implicit part of maximum sustainable yield models [42]. In this study, the guidelines proposed for different types of habitats were used to determine the number of individuals the park can stock [1, 43–46]. The vegetation composition and forage biomass determine the number of animals an area can support according to their feeding strategies. The stocking densities as determined by the study indicate the number of animals KLNP can support with the available resources. The stocking density can also be calculated on a time scale of interest, over which the potential dynamics of the population must be studied. This will allow for adaptive management as more knowledge about a specific area becomes available with time [45, 46]. In this sense, the stocking density is not a measure of the long-term equilibrium density but of a short-term potential density as a function of the availability of resources.
Acknowledgements This study was conducted under the project “Conservation Ecology of Eld's Deer and its Wetland Habitat”, sponsored by the Wildlife Institute of India through its grant-in-aid fund. We are grateful to the Department of Forests, Government of Manipur, for granting us logistic support. We thank the Director and the Dean at the Wildlife Institute of India for their support. We thank Sutirtha Dutta, Sangeeta Angom, Shivani Barthwal and Sayantika Bannerjee for all the discussions and critical inputs at different stages of the study. We would like to thank the anonymous reviewer for their valuable comments and suggestions. References [1] J.L. Holechek, An approach for setting the stocking rate, Rangelands 10 (1988) 10–14.
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