Phenological Study of Dacryodes edulis(Local Pear) growing in Ihiala, Anambra State, South-East, Nigeria

Introduction

Plant phenology, the timing of plants’ life cycle transitional events, plays an important role in tracking climate change, diagnosing agricultural management practices and investigating, ecosystem processes (3,8, 16).                                 

Plant phenology has been proposed as an indicator of climate difference and global change by the European Environmental Agency and the Inter-governmental panel on climate change (10).

Phenology has proven to be a multi-disciplinary science encompassing ecology, evolutionary biology and biometerecology (24). Also, the study of phenology have paved way for more understanding of resource availability and management for populations of many animal species in tropical ecosystems (2) and also indispensable in conservation, biodiversity monitoring and  management (12).

Since 1990, phenology has been one of the most active disciplines to evaluate the effects of climate change on ecosystems (17). Ecological responses to climate has been deduced through phenological data gotten by simple observation as this responds to climate variability at different levels (14). Many authors have reported changes in responses of organisms to current climate change (17, 14). The phenological changes are complex and subject to species, locations and seasons (16).

Depending on these factors, plant phenology may respond to changes in temperature, precipitation, snow melt or day length and plants may respond to cues differently in different seasons (7).

In spite of more studies on phenology over the last few decades (12), and the use of advanced technologies and other methods (1), there is still paucity of phenological data for most tropical fruit tree species. This has made it impossible for researchers to say in clear terms how the plants have been impacted in the face of our changing climate. The study is aimed at determining the seasonal appearance of phenophases in Dacryodes edulis, commonly called ‘local pear’ found in Ihiala, Anambra State, Southeast, Nigeria, a tropical climate is the specific aim of the study. The  main objectives of the study was to obtain and document phenological data and baseline information for D. edulis; evaluate the effects of seasons on the appearance of the phenophases and determine how stable or resilient the phenophases of the species have been in the face of changing climate.

MATERIALS AND METHODS

Study Area Characteristics:

The study was carried out at Ihiala, Nigeria. Ihiala is in a tropical region with dry deciduous vegetation and experiences two seasons- raining season (March-October) with temperatures ranging from 29.0⁰ to about 34.0⁰C and the dry season November- February) where temperature can reach 37.9⁰C.

Ihiala is a semi-urban area with enough fruit trees and is located in the south-eastern Nigeria between latitude 6⁰10’o’’N and longitude 6⁰46’o’E.

The average daily minimum and maximum temperatures of Ihiala is 22⁰C and 37⁰C respectively, with mean annual rainfall of 281.94mm (Weather spark.com, Anambra, Nigeria, 2022).

Data Collection

Samples: – Twenty (20) perennial tree samples (same species) of Dacryodes edulis (G.don) which have been actively flowering and fruiting over the years were ear-marked for the study at Afam village, Ihiala. Owners of the trees were informed to avoid acts of disruption like cutting down the tree. The timing of the initiation and completion of the following phenophases- budding, leafing, flowering,  fruiting and ripening were observed and recorded for all the (20) sample trees species for (3) cycles/years at 2 weeks interval.

This study was carried out for 3 years.

First cycle/year observation lasted from August, 2018- July, 2019.

Second cycle/year observation lasted from August, 2019-July 2020

Third Cycle/years observation lasted from January, 2022-December, 2022.

2.3 Data Analysis

The Biologische Bundesantalt and Chemische industries (BBCH) scale method of (11). (1993) in which the principal growth phases of the tree under study was sequentially arranged according to their natural appearance in the course of the year. In this method, the entire developmental cycles of the fruit tree was subdivided into ten (10) clearly recognizable and distinguishable long-lasting phenological phases, that is, the principal growth phases, thus;

-.          Budding.

–           Leafing  

–           Tillering

–           Shoot development

–           Development of harvestable vegetative plant parts or vegetatively propagated organs

–           Development of Inflorescence

–           Flowering

–           Fruiting

–           Ripening

–           Senescence/beginning of dormancy.

–           Ordinal numbers 0 to 9 was used to describe the principal growth stages in ascending order.

However, not all the principal growth stages were observed, as attention was on leaf development, flowering, development of fruit, fruit ripening.

The following are the principal growth stages

S/N      STAGES         DESCRIPTION                                          

1.      0    Budding
2.      1     Leafing
3.      2     Tillering
4.      3     Shoot development
5.      4     Development of harvestable  

Vegetative plantparts

•      5     Development ofInflorescent
•      6     Flowering  
•      7Fruiting
•      8     Ripening
•      9     Senescence, beginning

Of dormancy

BBCH Scale (11)

Since the principal growth stages cannot be sufficiently used to define exactly the stages in the developmental cycles before senescence, the secondary growth stages were introduced. They are the intermediate values between 0 and 9. These values, however, were expressed as percentage values in this study.

2 digit codes, BBCHXY, which resulted from the integration of the principal and secondary growth stages were used to define the phenophases overtime. The first ordinal number X denotes the principal growth stage, while the second ordinal number Y denotes the percentage of the development in the secondary stages. For example, the phenological leaf fall or leaf fall phenophase was defined with BBCH85, that is 8 is the principal growth stage for ripening secondary growth stage 5 in this case, stands for 50% of the fruits have ripened. Also, code BBCH10 depicts the beginning of leaf development, while BBCH19 is for the end leaf development.

The observer made use of visual observation in observing opening of flower buds and petals, colour changes and changes in size and number in the principal growth stages for the phenophases. The researcher ensured uniform conditions by observing the trees at 1.00pm. This was to ensure optimum sensitivity for colours for the eyes.

The researcher was interested in the species since it thrives in Nigeria especially in the region under study, where it is widely cultivated for its edible fruits. It was selected based on its easy-to-observe crown architecture and accessibility to its location in the region.

Photographs of different phenophases of the fruit tree was taken for proper identification. Also climate/ weather averages in Ihiala were collected to integrate with the records.

RESULTS AND DISCUSSION.

The results on the phenological studies  of Dacryodes edulis (G.Don) growing in Ihiala showing the timing of their different phenophases (Bud formation, leaf development, flowering, fruit development and ripening) during the study period (August, 2018-July, 2019; August, 2019-July, 2020; August, 2021-July, 2022).

That is, 3-seasons, are shown in Tables below.

The dash (-) represents gradual development of the phenophase.

Significant increase in bud formation was observed between 3^rd and 4^th week of July (BBCH04) through 3^rd and 4^th week of September (BBCH07). 80% of the leaves developed by 1^st and 2^nd week of October (BBCH18). By ending December, 20% of the leaves has fallen (BBCH92) and 60% has fallen by 1^st and 2^nd week in February (Table 1).

Flowering commenced by 3^rd and 4^th week in January (20%) (BBCH62) and by 1^st and 2^nd week of April (BBCH68) 80% flowering was achieved. Fruiting occurred 20% by 3^rd and 4^th week of February (BBCH72) and 3^rd and 4^th week of July, 80% fruiting has occurred (BBCH78) (Table 1). 20% ripening occurred in 1^st and 2^nd week in May (BBCH82) and continued till 1^st and 2^nd week August when about 80% of fruits has ripened (BBCH88) (Table 1).

Table 2: Phenophases of Dacryodes edulis (G. Don) Lam.

Note: The asterisks (*) in the table denote the absence of observed phenophases.

Note: The dash (-) represents gradual development of the phenophase.

Significant increase in bud formation was observed between 3^rd and 4^th week of July (BBCH02) through 1^st and 2^nd week of November (BBCH07). 80% of the leaves developed by 1^st and 2^nd week of October (BBCH18). By ending week December, 20% of the leaves has fallen (BBCH92), and 60% has fallen by 1^st and 2^nd week in February (BBCH96) table (2). Flowering commended by 3^rd and 4^th week in January (20%) (BBCH62) and by 1^st and 2^nd week of April (BBCH68) 80% flowering was achieved.

Fruiting occurred 20% by ending of February (BBCH72) and by ending July, 80% fruiting has occurred (BBCH78). 20% Ripening occurred in 3^rd and 4^th week in May (BBCH82) and continued till ending September when about 90% of fruits has ripened (BBCH89) (Table 2).

Bud formation, leaf development and leaf fall are gradual and steady in Dacryodes edulis. However, increased bud formation was observed between early June (BBCH05) and latter September (BBCH09) (Table 3). Also, increased leaf development was observed between ending July and early October (BBCH18) (table 3). Bud formation, leaf development and leaf fall were overlapping. Flowering commenced early January (BBCH62) through early April (BBCH69).

Fruiting occurred from early February (BBCH72) through ending August (BBCH79). Ripening occurred 20% by early May (BBCH82) and continued through ending August when about 90% of fruits has ripened (BBCH89) (Table 3).

DICUSSIONS

Dacryodes edulis (Tables 1, 2, 3)- The study revealed that the studied fruit trees showed vegetative and reproductive phenophases following in quick succession. This supports (19) assertion that plant vegetative and reproductive growth and development shows rhythmic appearances over time. Bud formation, leaf development and leaf fall phenophases were overlapping without the tree being leafless at any period, that is, semi-deciduous. This vegetative phase occur before the tree’s reproductive phase: Flowering and fruiting. The reproductive phenophases require more nutrients which is coincidentally provided by a mulching mat of fallen leaves (July – November) which decays with the coming rains in March, against peak flowering time of April in D.edulis. According to (21) the period of vegetative phenology strongly determines the flowering period. In woody species, phenological events are interdependent (20). Flowering in D.edulis occurred more during dry season (January – April), fruiting occurred more towards rainy (February – July) while ripening occurred more during rainy season (May-August/September). This suggests that seasons in the area influence the reproductive phenophases in D.edulis. Changing seasons influence the appearance of phenophases in Delonix regia (6); also in Irvingia gabonensis (14)

The fruiting and ripening time in Dacryodes edulis may have lagged by 2-4 weeks comparing the three (3) seasons of this report and also with the reports of (24) that recorded July as peak ripening period. Phenological shifts are ubiquitous phenomenon and can be interpreted as a sensitive indicator of the ecological impacts of climate change (21). Reproductive stages of fruit trees are most susceptible to climate change with implication on quantity and quality of the fruits produced (18). Shifts (leading or lagging) in timing of the phenophases of these fruit trees, especially flowering and fruiting, causes disruption of the pollen-pollinator relationship, also shifts into period of higher temperature cause poor pollen production, pollen desiccation and consequently poor food production or yield (1, 9). The result implied that D.edulis trees flower and fruit once in a year, also that mature ripe fruits drop from the trees from May to August/September. Seeds for propagation therefore, can be collected within May and September. The study equally revealed high level of synchronization in the appearance of phenophases in D.edulis. There is virtually no isolated initiation and completion of any phenophases by individual trees.

CONCLUSION

This study has revealed the phenological data for D. edulis for the region and where similar climatic conditions prevail. It could be of great help in knowing the timing of different phenophases in D. edulis for people who wish to plan their orchards. The phenological data and pattern revealed by this study will serve as a valuable indicator of ecological responses to climate change in the area as well as be of great help for comparison over  long duration of time to see if there will be further change in the phenological patterns of D. edulis.

REFERENCES

1. Bhriguvanshi, S.R. (2010). Impact of climate change on mango and tropical fruits. In: Singh, H.P Singh, J.P, Lal, S.S, Westrille Publishing House, New Delhi, India. pp. 224.
2. Bullock, S.H., Solis Magallance, J.A. (2015). Phenology of Canopy Trees of a Tropical deciduous forest in Mexico. Biotropica, 22, 22- 35.
3. Chuine, I. (2010). Why does phenology drives species distribution? Philosophical Transactions of the Royal Society B: Biological Sciences, 365, 3149- 3160.
4. Chmielewski, E.M., Heider, S., Moryson, S. and Bruns, E., (2013). International Phen Gao, B. J, and Wang, X. (2020a). Impact of Frozen Soil Changes on Vegeta Phenology in the Source Region of the Yellow River from 2003 to 2015.
5. Chmielewski, F.M. (1996). The international phenological; gardens across Europe.Present state and perspectives. Phenological  Seasonality 1, 19-23.
6. Echereme, Chidi B., Mbaekwe, Ebenezer I. and Ekwealor, Kenneth, U. (2015). Phenological study of Delonix regia. International Journal of Scientific and Research Publications. Vol. 5, Issue 9.
7. Flynn, D.F.B. and Wolkovich, E.M. (2018). Temp and Photoperiod drive spring phenology across all species in a temperate forest community. New phytologist 219(4): 1353-1362.
8. Gao,  B., Li, J., and Wang, X. (2020). Impact of Frozen Soil Changes on Vegetation Phenology in the Source Region of the Yellow River from 2003 to 2015. Theoretical Applied Climatology 141, 1219–1234.
9. Gorisamo, Alemu; Clen, Jing M.; Wu, Chapyang (2013). Citizen science: linking the recent rapid advances of plant flowering in canada with climate variability”. Scientific Reports. 3(1): 2239.
10. IPCC (2007). Climate change 2007, impacts, adaptation and vulnerability.Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Pp.43
11. Meier, N., Bachmann, T., L., Buhtz, E., Hach, H., Klose, R., Marlander, B. and Weber, E.(1993). Phanologische Enttwicklungsstadien dear Beta Ruben (Beta Vulgaris L.) Coddierung und Bschreibung Nach dear erweiterten BBCH-ska la not Abbildungen, Nachrichtenbl. Deut. Pflanzenschutzd, 45: 37-41.
12. Morellato, L.P.C, Alberton, B., Alvarado, S.T., Borges, B., Buisson, E., Camargo, M.G.G.; Cancian, L.F., Carstensen, D.W., Escobar, D.F.E. and Leite, P.T.P. (2016, ). Linking plant phenology to conservation biology. Biological conservation 195, 60-72.
13. Morellato, L.P.C., Camargo, M.G.G. and Gressler, E.A., (2013). Review of plant phenology in
    1. South and Central America. In Phenology: An integrative Environmental Science, Schwartz, M.D.; Ed.; Springer: Dordrecht, The Netherlands, Pp. 91–113.
14. Ochia, A.M., Ekwealor, K.U., Okigbo, R.N. and Iroka, F.C. (2021). Phenological study of Irvingia gabnsis growing in Ihiala, Anambra State, Nigeria. Journal of Advances in Biology and Biotechnology, 24(7):26-31.

1. Pau, S., Wolkovich, E.M., Cook, B.L., Davies, T.J., Kraft, N.J.B., Bolmgren, K., Batancourt, J.L. and Cleland, E. (2011). Predicting phenology by integrating ecology, evolution and climate science. Global change biology 117, 3633-3643.
2. Piao, S. L, (2015). Leaf onset in the northern hemisphere triggered by daytime temperature. Nature Communications 6: 6911.
3. Piao, S., Liu, P., Chen, A. and Wan, A.J., (2019). Plant phenology and global climate change; Current progresses and challenges. Global change Biology. 25(6).
4. Ramos, C.; Introgholo, D.S; Thompson, R.B. (2011) Global Change challenges for horticultural systems. In: Araus, J.L, Slafer, G.A., editors crop stress management and Global climate change. CAB International. 
5. Singh, K.P. and Kushwaha, C.P. (2015). Diversity of flowering and fruiting phenology of trees in a tropical deciduous forest in India. Annals of Botany 97(2), 265-276.
6. Van Schaik, C. P., Terborgh, J. W., and Wright, S. J. (1993). The phenology of tropical forests: Adaptive significance and consequences for primary consumers. Annual Review of Ecology and Systematics, 24, 353-377.
7. Walther, G.R., Post, E., Convey, P., Menzel, A., Parmesan, C., Beebee, T.J.C., Fromentin, T.M., Hoegh-Guldberg, O. and Bairlein, F. (2020). Ecological responses to recent climate change. Nature; 416:389-395.
8. Waruhiu Annabelle N.; Joseph Kerigue; Alain R. Atangana; Zac Tchoundjeu and Roger, R.B Leakey (2004). Food, Agriculture and Environment Vol. 2 (1): 340 – 346.
9. Weather spark.com>(2022). Anambra (Nigeria)
10. Wolkovich, E.M., Cook, B.I. and Davies, T.J (2014). Progress towards an interdisciplinary science of plant phenology: building predictions across space, time and species diversity. New phytologist 201: 1156- 1162.