THE ECOLOGICAL STATUS OF CLEISTOPHOLIS PATENS IN BUDONGO FOREST RESERVE, UGANDA

Transcription

1 THE ECOLOGICAL STATUS OF CLEISTOPHOLIS PATENS IN BUDONGO FOREST RESERVE, UGANDA BUDONGO CONSERVATION FIELD STATION (RAPHIA CONSERVATION PROJECT) A SUMMARY OF THE MAJOR FINDINGS JULY 2010 Gilbert Atuhe

2 Abstract Cleistopholis patens is one of the tree species known to be a source of food for the Sonso chimpanzees in Budongo Forest Reserve. The chimpanzees visit the dead trees of this species and pick the rotten material which they chew and extract the juice. However not much is known about its ecological status in terms of abundance, distribution and other possible products and services that it may render to the local communities in Budongo. The objectives of this study were to determine and compare the abundance, distribution and population structure of Cleistopholis patens in the swamp and non-swamp habitats of Budongo Forest Reserve. A further objective was to document the uses of Cleistopholis patens, perceptions about the species population dynamics and local attitudes to its conservation. The study was carried out using ethnobotanical and quantitative ecological methods. The species was found to produce only five products and services. The most frequently mentioned products were herbal medicines and soft wood for light construction. Community responses revealed that the species was generally rare but only abundant in water logged and riverine areas. Communities were not sure about whether the population of Cleistopholis patens was increasing, constant or on the decline. The quantitative inventory supported the view that Cleistopholis patens thrives better in the swamp forest (58.7% of the plots) than other forest types (10.7%). The species had a higher density (38 individuals per hectare) in swamp forest compared to the non-swamp forest (1.7 individuals). The population of Cleistopholis in swamp forest had a moderately steep size class distribution (slope = ) while that of the non-swamp forest had flat size class distribution (slope = ). The proportion of the adult Cleistopholis trees (> 42.5cm DBH) was 7.7% and the mortality rate of seedlings was 48.8%. The species can only be threatened if the swamp and riverine areas of the forest are depleted because this would reduce on its regeneration capacity. Respondents were not motivated to conserve Cleistopholis patens because they had low appreciation of the species true value since it had no significant economic benefit.

3 1 Introduction Cleistopholis patens (Benth.) Engl. & Diels is a forest tree that can grow up to 25 m (Hamilton, 1991). It is one of the tree species whose bark and wood provide food to the chimpanzees in Budongo Forest Reserve (Tweheyo et al., 2004). In a similar way as Raphia farinifera (Reynolds et al., 2009), the chimpanzees visit the dead trees of this species and pick the decayed material which they chew, extract and swallow the juice. The conservation of Cleistopholis patens is therefore paramount because as a food resource it complements Raphia farinifera. Conservation of Cleistopholis patens can take effect if there is enough information regarding its abundance, distribution, habitat preference and assessment of other potential threats surrounding it. This study was carried out to document the ecological status and existing usage of Cleistopholis patens in the selected local communities of Budongo Forest Reserve.

4 2 Materials and methods Data collection Fieldwork for this study was carried out between April and June 2010 using both ethnobotanical and quantitative ecological methods. The ethnobotany study was conducted through focus group discussions which were held in three villages of Nyabyeya II, Maramu and Kanyege (Fig. 1). A reconnaissance visit was made to each village to test the leading questions and see whether people were actually aware of Cleistopholis patens. The reconnaissance revealed that not many individuals knew much about the tree. The approach therefore had to be in such a way that people gather and freely discuss in meetings, hence the focus group discussions. The discussions were more effective because a lot of information was obtained in a short time. The major questions of discussion were: whether the members were familiar with Cleistopholis patens, where the tree is usually found, what uses were put to the species, what changes had been observed regarding its abundance and what were the prevailing attitudes towards its conservation. The ecological study was carried out in compartments N1, N2, N3, N4 and N15 of Budongo Forest Reserve. These were specially chosen because they are within the home range of the Sonso Chimpanzees. 30 plots of 20 x 50 m were systematically placed in each of the compartments of which 15 were in the swamp forest and the rest in the non-swamp forest. The total area sampled was therefore 15 hectares. The first plot in each case was randomly located, then subsequent ones were placed alternately along a transect 1100m long at an interval of 20m. The direction of the transects was east to west and each was bearing 15 plots. Within each plot all individuals of living and dead Cleistopholis patens were counted and their DBH and CRC was measured. Other trees of DBH greater than 10cm were counted and the canopy openness of the plots was estimated visually at three points in the north to south direction. The undergrowth vegetation was measured at four positions within each plot using the squared board (Nudds, 1977). The condition of the plots and Cleistopholis were also noted. Data analysis Data from the ethnobotanical study was recorded as received from the focus group discussions were summarized in frequency diagrams. From the quantitative inventory, the species density for each habitat was calculated and compared using SPSS 16. A size class frequency distribution plot (SCD) for each habitat was produced by plotting the stem density against diameter class. A linear regression slope was also calculated for the SCD using software SPSS for windows in order to determine its shape (Lykke, 1988). Populations with steep negative slopes are considered to be stable whereas those with weak negative slopes depict poor recruitment and declining populations (Obiri et al., 2002). The regression slope was calculated by obtaining the diameter class mid-point (di) and the number of individuals per hectare (Ni) and plotting them as independent and dependent variables respectively. In order to cater for diameter class with zero individuals, Ni was transformed by ln (Ni+1) (Obiri et al., 2002). Canopy openness was used to compare the two habitats. A paired samples t-test was calculated in SPSS for the means of canopy openness and vegetation undergrowth for each plot in the swamp and non-swamp forest. The same test was used to compare the average number of trees greater than 10cm in diameter per plot in the swamp and non swamp forest. A regression-correlation was done between the mean canopy openness of swamp forest, mean vegetation undergrowth and number of Cleistopholis trees to determine their habitat preference.

5 3 Key findings Awareness of Cleistopholis patens Meetings were well attended in all the three villages with 40 people at Nyabyeya II, 39 people at Murram and 45 people at Kanyege. Cleostopholis patens (also known as adho by the Okebu or mubanda marogo in Runyoro) was known, on average, by 14 members who attended in each meeting. Cleistopholis patens was reported to be generally scarce except in waterlogged areas, near river Sonso and in some open sections of the forest. It was stated that the tree is able to grow large and tall but its rate of growth is slow. Three birds; the hornbill, grey parrot and owl were mentioned as to participate in the dispersal of Cleistopholis patens. The birds are found of eating the fruits of this species after which they drop the seeds under the mature tree (Peter Turyatemba, pers. com 2010). It was mentioned by members that chimpanzees and gazelles eat the bark and stem of trees which are lying on the forest floor. Another observation was that colobus monkeys dig into the soil and eat the roots of Cleistopholis patens. Figure 1: Focus group discussions: (Left) a lady explains some of the uses of Cleistopholis patens at Kanyege. (Right) focus group discussion held at Maramu village. Uses of Cleistopholis patens Cleistopholis patens was reportedly harvested, but only rarely to provide soft timber for making door frames, and soft boards due to its weak stem (n=15). Its timber is also susceptible to termite attack and cannot be used for heavy outdoor construction. Sometimes the dead branches of Cleistopholis and other species are gathered for firewood. The product mentioned by the majority of the participants was that its seeds ( kei kei in Alur, kivi kivi in Okebu and kuru in Acholi) are medicinal. In one application, they are roasted and ground and the powder is used to heal extreme headache. Seeds are also believed to protect people from charm when worn around the waist or put in the pocket. One member from Murram village reported that the bark of Cleistopholis patens is crashed to make medicine for malaria and measles. Other services included provision of shade and use of ash as food preservative (Fig. 2).

6 Medicine Timber/construction Fuel Shade Food Preservative (Ash) Figure 2: Products and services of Cleistopholis patens Attitudes to conservation People were poorly motivated to conserve Cleistopholis patens. None of the members who attended the meetings had established or managed the tree for its future availability. The majority attributed their lack of interest to a poor appreciation of the species true value since it had no significant economic benefit. Ecological status No. of respondents Most participants claimed that the species was common in the forest, especially near the swamp. They however were not sure whether its population was declining or increasing. The community perceptions were collaborated by the analysis of the population structure for the swamp and non-swamp forest (Fig. 3). Figure 3: Size class frequency distribution of Cleistopholis patens in Budongo Forest Reserve The population density of Cleistopholis patens in BFR ranged between 1.7 and 38 individuals per hectare in the non-swamp and swamp forests respectively. Cleistopholis was more widely distributed in swamp forest (58.7%) than in non-swamp forest (10.7%). The population of Cleistopholis in swamp forest had a

7 moderately steep size class distribution (slope = ; r 2 = 0.87, t = -10.2, p = 0.000) while that of the non-swamp forest had flat size class distribution (slope = ; r 2 =0.46, t = -3.67, p = 0.002). Generally the plot of the size class distribution (SCD) showed that the population was made up of mostly seedlings (17.2 stems per hectare) and very few adult individuals. The proportion of the adult Cleistopholis trees (> 42.5cm DBH) was 7.7% of the population. The mortality rate of seedlings was 48.8% before they become saplings (Fig. 3). The survey revealed that most Cleistopholis trees were healthy except for the damaged ones (n=4), those which were felled (n=2), dead (n=6) and rotten stumps (n=2) (See Fig. 4). Figure 4: (Left). A young Cleistopholis growing in the swamp. (Right). One of the dead Cleistopholis trees. There mean number of trees with DBH greater than 10cm were significantly more (t = 6.8, p<0.05) in non-swamp forest (n=48) than in swamp forest (n=32). The quantitative inventory indicated further that the canopy of the swamp forest was more open (33.2%) compared to non-swamp forest (27.7%) and this difference was significant (t = -3.1, p<0.05). The results also show that the non-swamp forest had less vegetation undergrowth compared to swamp forest (t=6.81, p<0.05; Fig. 5). There was no significant relationship between forest undergrowth and number of Cleistopholis trees (r 2 =0.06, t = -0.58, p>0.05). There was also no significant relationship between forest undergrowth and the size of Cleistopholis individuals (r 2 =0.04, t=1.48, p>0.05). Lastly, there was no significant relationship between canopy openness and number or size of Cleistopholis (r 2 =0.004, t= -0.43, p>0.05 and r 2 =0.008, t= 0.65, p>0.05 respectively). Figure 5: Measuring vegetation undergrowth using a squared board in non-swamp (left) and swamp forest (right).

8 4 Discussion Abundance and distribution of Cleistopholis patens Cleistopholis patens appears to be only abundant and widely distributed in the swamp forest of BFR. This fact is in agreement with the perception of the local community and the findings of Hamilton (1991). The analysis of the SCD indicated that the species had a relatively strong population structure in the swamp because forest (-0.248) and a weak population structure in the non-swamp forest ( ).This means that Cleistopholis patens has a better regeneration potential in swamp forest than in the non-swamp forest and its population, given that the adults attain fruiting age, is bound to increase. The swamp SCD plot depicted a generally low density of Cleistopholis (38 individuals per hectare) nevertheless the seedling survival rate was at 51% implying that that not many seedlings were lost to the population before they attained pole size or mature stems. The fact that the non-swamp forest had very few young trees and no mature stems implies that its population is declining in abundance (Baker et al., 2005). The species in this habitat is at risk because absence of adults in the population means there will not be enough seed by which the species will recruit (Hall and Bawa, 1993). For a population to maintain itself, it needs to have abundant juveniles which will recruit into adults (Lykke, 1998). In general, the scantiness of the distribution and absence of mature Cleistopholis patens is probably a result of selective logging during the 1970s and also by the few current timber dealers. Firewood collection is cannot be considered an important reason for its scarcity because the community members collected dead wood. Another factor for its skewed distribution could be that Cleistopoholis patens has got particular habitat preference which is related to the soil in the swamp. This assumption is based on the fact that other factors such as canopy openness and undergrowth did not have significant effect on the abundance and size of Cleistopholis patens. The testimony of the colobus monkeys feeding on the roots could be a sign that actually there is a particular nutrient which they are interested in that is only concentrated in the roots of Cleistopholis. Species use and attitudes to its conservation Cleistopholis patens is neither used extensively nor highly appreciated among the local community of Budongo. This assumption is based on the fact that very few participants were, on individual basis able to mention a single end-use put to the species. The majority of the participants claimed that the species was not important to them. There are two factors which seem to contribute to the low importance attached to Cleistopholis patens by the communities. These include the fact that the tree is slow growing and that its timber is soft, hence not marketable. Other factors worth noting include lack of propagation materials and knowledge.

9 5 Conclusion Cleistopholis patens is more abundant and stable in the swamp forest than in the non-swamp forest. At this point the factor worth noting for its abundance could be that there is more seedling survival in the swamp than in the non-swamp forest. Swamp forest, as opposed to nonswamp forest provides enough light and moisture for the germination of Cleistopholis seeds. The local community of Budongo is fairly aware of Cleistopholis patens and its abundance. They however do not have clear say about its population structure and whether or not it is has declined in population. This could be as a result of lack of knowledge of its identity and significance to the forest ecosystem. The level of utilization of Cleistopholis patens by the Budongo people is not as significant as for other trees in the forest probably due to the low level economic value attached to it. The few domestic and medicinal values cannot expose it to rapid and unsustainable harvesting that can lead to its extinction. There is a link between the habitat preference for Cleistopholis patens and the reason why colobus monkeys are interested in eating the roots of the species. The meeting point could probably be a nutrient or mineral in the swamp soil that is also responsible for its abundance there as opposed to the non-swamp forest. 6 Recommendation The conservation of Cleistopholis patens requires that communities living around Budongo Forest Reserve are sensitized about its true importance. Mature trees in the swamp forest should be protected to ensure they reach seeding stage. Conservation of the swamp/riverine forest of Budongo will contribute significantly to the survival of the chimpanzees because it is habitat for plant species which provide food for the primates. There is need for a detailed study about the regeneration, ex-situ conservation and strength properties of Cleistopholis in order to verify the claims made by the local community. Soils samples and roots of Cleistopholis patens from both the swamp and non-swamp forest could be analysed for mineral (nutrient) concentrations so as to prove whether there is an association for its distribution.

10 References Baker, P.J., Bunyavejchewin, S., Oliver, C. D. & Ashton, P.S. (2005). Disturbance history and historical stand dynamics of a seasonal tropical forest in western Thailand. Ecological monographs, 75: Hall, P. & Bawa, K. (1993). Methods to assess the impact of extraction of Non-Timber Tropical Forest Products on plant populations. Economic Botany, 47: Hamilton, A. (1991). A field guide to Ugandan forest trees. Makerere University, Kampala, Uganda. Lykke, A.M. (1998). Assessment of species composition change in savanna vegetation by means of woody plants size class distributions and local information. Biodiversity and Conservation, 7: Nudds, T.D. (1977). Quantifying the vegetative structure of wildlife cover. Wildlife society bulletin, 5: Obiri, J., Lawes, M. & Mukolwe, M. (2002). The dynamics and sustainable use of high-value tree species of the coastal Pondoland forests of the Eastern Cape Province, South Africa. Forest Ecology and Management, 166: Reynolds, V., Lloyd, A.W, Babweteera, F., English, C.J. (2009). Decaying Raphia farinifera palm trees provide a source of Sodium for wild chimpanzees in the Budongo Forest, Uganda. PLoS ONE, 4(7): e6194. Tweheyo, M., Lye, K.A., Weladji, R.B. (2004). Chimpanzee diet and habitat selection in the Budongo Forest Reserve, Uganda. Forest Ecology and Management, 188: