Adaptation and growth performance of different bamboo species in Dryland areas of Northern Ethiopia

Abstract Bamboos are among the large perennial grasses that are renowned for their remarkable vigor and quick development. However, the amount of bamboo available in natural settings is decreasing as a result of shifting agriculture, overexploitation, and forest fires. Furthermore, there is little genetic diversity in our country because just two species are found in a small number of agroecological zones. This makes it difficult to guarantee a steady supply of bamboo, despite its benefits to the environment and economy. Thus, the goal of this study was to evaluate the adaptability and growth performance of four bamboo species: Oxytenanthera abyssinica (A.Rich.) Munro, Phyllostachys edulis (Carrière) J Houz, Bambusa vulgaris Schrad. ex J.C. Wendl, and B-ambusa bambos (L) Voss'. The study was carried out at the Mekelle Agricultural Research Center compound for four years, from 2020 to 2023. Three replications of a strict RCBD design were used in the experiment. There were four plants each plot, for a total of 48 plants, and there was a three-meter gap between each plant and plot. A range of growth indicators, including new shoot emergence, culm diameter, internode length, culm height, and survival rate, were measured at three-month intervals in order to monitor changes among the species. B. bambos, B. vulgaris, and O. abyssinica showed no problems with survival or adaptation in the research locations, with the exception of small growth variances. Significant changes (p≤ 0.05) in the treatment parameters were shown by the statistical analysis. O. abyssinica displayed a noticeably greater quantity of freshly emerging bamboo shoots in comparison to other bamboo species. Conversely, P. edulis showed the lowest growth metrics in terms of internode length, culm height, culm diameter, and survival rate. P. edulis, B. vulgaris, O. abyssinica, and B. bambos had survival rates of 16.67 percent, 66.67 percent, 75 percent, and 91.67 percent, respectively. It is noteworthy that seasonal differences have a substantial impact on the height of culms and the growth of newly emergent shoots. B. vulgaris, B. bambos, and O. abyssinica all showed good growth and survival rates. As a result, it is advised to highlight and promote these species in related agroecological areas, as this can benefit multiple stakeholders’ livelihoods and economies.


Introduction
Among perennial grasses, bamboos are renowned for their remarkable strength and rapid growth (Chen et al., 2022;Lombardo, 2022).Classified as a giant grass, bamboo plants serve tree-like ecological functions (Nath et al., 2009;Yen et al., 2010;Yen & Lee, 2011).With approximately 1,662 woody and herbaceous species distributed across Asia, South America, Africa, and North and Central America, bamboo belongs to the Poaceae family and the Bambusoideae subfamily (Canavan et al., 2017;Nations, 2020;Sawarkar et al., 2020).
In Ethiopia, bamboo resources cover one million hectares, accounting for 67 percent of Africa's bamboo coverage and 7 percent of the global total (Mengesha Mulatu, 2012).Africa itself is home to 43 bamboo species, including two indigenous species found in Ethiopia: Arundinaria alpina K. Schum and Oxytenanthera abyssinica (A.Rich.)Munro (Bekele-tesemma, 2007).
Bamboo holds significant economic value as a rapidly growing and renewable raw material.It plays a crucial role as a non-timber forest product, often cultivated in rural community gardens (Anjulo et al., 2022;Murtodo & Setyati, 2015).Communities utilize bamboo extensively for construction, handicrafts, wood substitutes, composites, and as a source of nutritious elements beneficial for health (Hong et al., 2011).Moreover, bamboo's extensive root system aids in water management and erosion prevention, contributing to the delicate balance of the environment (Mentari et al., 2018).
Despite being one of Africa's bamboo-rich countries, Ethiopia experiences limited genetic diversity, Bamboo; adaptation; lowland; arid environment; Fast growth with only two bamboo species, A. alpina and O. abyssinica, confined to specific agroecological areas (Bekele-tesemma, 2007).This poses a significant challenge in ensuring a consistent bamboo supply for enterprises and regional handicrafts.Without substantial intervention measures, arbitrary forest loss and habitat destruction may deplete this valuable bamboo resource before its full economic and environmental benefits are realized.Bamboo holds immense potential in addressing environmental degradation and creating economic opportunities for a substantial segment of the population.However, the study and development of Ethiopia's bamboo resource has been relatively limited.
Therefore, it is crucial to introduce and evaluate the adaptability of high-value exotic bamboo species in the country.This will not only increase the income of bamboo-dependent small-scale farmers but also diversify the genetic resources of bamboo species and promote sustainable land management practices aimed at environmental conservation.The objectives of this study are to analyze the adaptability and growth performance of various bamboo species in the Mekelle research site and subsequently extend the findings to suitable agroclimatic zones in the Tigray region and other areas of Ethiopia.

Study area
The experiment was conducted at Mekelle Agricultural research center experimental site Tigray, Ethiopia (Figure 1).
Mekelle is located in the Tigray region of northern Ethiopia.Geographically, it is situated at approximately 13.5°N latitude and 39.5°E longitude.The soil types prevalent in this area are diverse but predominantly fall under the classification of vertisols or clayey soils, which have high water-holding capacity but can be prone to cracking during dry periods.
The altitude ranges between 1965 m to 2,254 m above sea level, contributing to a cooler climate compared to lower-lying regions.
It experiences a semi-arid climate characterized by distinct wet and dry seasons.Rainfall is bi-modal rainfall pattern with two rainy seasons from June to September and March to May.The average annual rainfall ranges from 500 to 800 millimeters.The study area maintains a mild climate with average daily temperatures ranging from 16 °C to 23 °C, rarely exceeding 30 °C or dropping below 10 °C (Figure 2).

Experimental design
The experiment was conducted using a Randomized Complete Block Design (RCBD) with three replications, where each treatment was assigned to a replication.The distance between and within plots and blocks was 3m x 3m.In June 2019, four plants per plot, or a total of 48 plants, were planted in the experimental site.
The following four bamboo species were used as treatments: 1. B. bambos: Also known as 'Giant Thorny Bamboo (Raju & Roy, 2016), ' it is native to South and Southeast Asia, with a wide distribution in tropical regions (Wijewickrama et al., 2020).It thrives in a humid tropical climate with moist soil (Sarojam & Kumar, 2001).patterns (Ojo & Sadiku, 2023).The newly formed shoots and leaves of B. vulgaris are consumed as food and possess antimicrobial properties (Goyal et al., 2013).It is also used in traditional medicine for various purposes, including treating measles and respiratory diseases (Owolabi & Lajide, 2015).The culms of B. vulgaris can reach heights of 10-20 meters with a diameter of 4-10 centimeters (Ohrnberger, 1999).

O. abyssinica: This clumping bamboo species is
native to the savannah woodlands of Africa and is endemic to the continent (Elbasheer & Raddad, 2013).Ethiopia contributes a significant portion of the total bamboo area in Africa, with O. abyssinica being the dominant species in the country (Oumer et al., 2020).It thrives in lowland areas with poor soils, rocky terrain, high temperatures (averaging 20-35 °C), and low rainfall down to approximately 600 mm (Mulatu et al., 2016).O. abyssinica has remarkable ecological potential, with a maximum diameter of 10.16 cm and a maximum height of 9.14 m (Lobovikov et al., 2007).4. P. edulis: Also known as Moso bamboo, it is a non-wood forest product and wood substitute that plays a crucial role in socioeconomic development (Shi et al., 2015).It is the most widely distributed economic bamboo species in southern China and has the ability to invade adjacent communities due to its clonal reproduction (Sun et al., 2023).Asexual reproduction is this plant's most prevalent and well-known method.This happens when the plant emerges from its underground rhizomes with new culms.It has a diameter of 6.3 cm to 10.1 cm and a density of 5333 culms per ha to 6900 culms per ha (Huang et al., 2014).P. edulis can reach impressive heights of up to 28 meters (Lewis & Miles, 2007;Yen & Lee, 2011).
These bamboo species were selected as treatments based on their distinct characteristics and suitability for the study.

Data collection Method
The experiment, conducted between 2019 and 2022, aimed to assess the adaptability and growth performance of four bamboo species in the arid regions of Northern Ethiopia.The evaluation focused on key parameters such as survival percentage, culm height (CH), internode length (IL), new shoot emergence (NES), and culm diameter (CD).Data collection occurred at three-month intervals to analyze the impact of seasonal variations on the survival and growth of each bamboo species.This comprehensive approach allowed for a thorough assessment of the adaptability potential and performance of the studied species in the dryland areas.

Data Analysis
The survival and growth performance data were subjected to a rigorous statistical analysis using a two-way analysis of variance (ANOVA) based on the General Linear Model (GLM) approach.This analysis was conducted at a significance level of 5% using the SPSS software for Windows version 27.To determine any significant differences among the means, Tukey's HSD test was employed.This approach allowed for precise separation of means whenever there was a statistically significant difference observed.By employing these robust statistical methods, the study ensured accurate and reliable interpretation of the survival and growth performance data.

Survival Rate
During the four-year experimental period, the selected dryland bamboo species demonstrated promising growth.The average survival rates for the four-year growing seasons were: B. vulgaris (66.67 percent), O. abyssinica (75%), B. bambos (91.67%), and P. edulis (16.67%).With the exception of P. edulis, all species thrived in the study area, indicating their suitability for the agroecology of the region.These high rates of survival can be attributed to their development capacity and adaptability.

The influence of Season on growth of Bamboo species
The interaction between bamboo species and seasons significantly influenced the growth characteristics of new emergent shoots, whereas culm height was not affected.The analysis of variance revealed significant variations in new emergent shoots and culm height among the bamboo species Table 1.
The analysis of variance indicated significant variations (p ≤ 0.05) in growth parameters among the bamboo species throughout the year (Table 2).However, the culm height of P. edulis remained consistent across all seasons.Interestingly, the summer season emerged as the most favorable period for bamboo growth, potentially due to the abundant water availability during this time.Similar results were reported by Gulabrao et al. (2012) and Shirin et al. (2021)for culm and root growth of bamboo species.

New Emerging shoots
The development of new rhizomes and shoots in lateral buds is strongly influenced by factors such as rhizome age, vigor, and nutrient storage (McDowell & Gang, 2012).The analysis results revealed significant variations in the number of new emerging shoots among the bamboo species, particularly in the case of O. abyssinica (Table 3).This species demonstrated superior adaptability and a remarkable ability to produce new emergent shoots compared to the other species.
In our study area, the new emerging shoots of O. abyssinica outperformed the results reported by Terefe et al., (2016a)in Bako, West Shoa, Ethiopia.However, the number of new emerging shoots (10.67) was lower in West Hararghe, Mechara, as reported by Diriba et al., (2021).On the other hand, during the experimental period, B. bambos, B. vulgaris, and P. edulis species exhibited poor performance in terms of the number of new shoots that emerged.

Culm Height (m) and Diameter (cm)
The lower internodes of culms exhibit a solid structure, while the upper internodes are hollow and extend to the apex of the culm.In the case of O. abyssinica, the culms start off as semi-solid at a young age but solidify as they mature (Mulatu et al., 2016).B. vulgaris and P. edulis, like other bamboo species, have visible nodes that create a segmented stem with a hollow interior, except at the nodes themselves.However, B. bambos culms can occasionally be almost solid in the upper part.
The length of the culm varies among the species.As shown in Table 3, P. edulis has significantly shorter culm height compared to the other species.However, there is no statistically significant difference in culm height between B. bambos, O. abyssinica, and B. vulgaris.The culm height of O. abyssinica aligns with previous research conducted in West Hararghe (Diriba et al., 2021).
Furthermore, the analysis examined and compared the culm diameter.The thickness or size of the culm serves as an indicator of bamboo quality and is indirectly related to culm diameter.The results revealed a significant difference in culm diameter among the species.B. bambos and B. vulgaris exhibited larger culm diameters compared to P. edulis, as shown in Table 3.However, there was no significant variation in culm diameter between B. bambos, B. vulgaris, and O. abyssinica.The overall culm diameter in our study was lower than that reported in other studies conducted in West Hararghe (Diriba et al., 2021), Kobo, North-east Ethiopia (Getachew et al., 2021) and Bako, West Shoa, Ethiopia (Terefe et al., 2016).This difference could be attributed to the lower amount of rainfall received in our study area.

Internode Length (cm)
The structure of cylindrical bamboo culms is divided into segments by diaphragms or nodes.The spaces  (Diriba et al., 2021) and better than the study conducted in Bako, West Shoa, Ethiopia (Terefe et al., 2016).Nonetheless, the internode length of the investigated bamboo species was shorter than those studied in Kobo, North East Ethiopia (Getachew et al., 2021).The variations in internode length across different study areas could be influenced by species, site conditions, and climate.

Conclusion and recommendation
In conclusion, the bamboo species that demonstrated the best growth parameters and survival rates in the study area were O. abyssinica, B. bambos, and B. vulgaris, in that order.With minor differences in growth performance for comparison, these selected bamboo species have shown good adaptability to the study area.
The summer season was found to be the optimal time for bamboo species to thrive.P. edulis, on the other hand, exhibited lower growth metrics compared to O. abyssinica, which displayed significant differences in new shoot emergence, internode length, culm height, and culm diameter.Based on these findings, we recommend O. abyssinica, B. bambos, and B. vulgaris for various production purposes due to their favorable characteristics such as survival rate, internode length, new shoot production, culm height, and diameter.These species are well-suited for regions with abundant rainfall.Therefore, the adaptation of bamboo species in the study area's agroecologies proves reliable when the rainfall exceeds 600 mm.We highly recommend further expanding the bamboo plantation to generate economic and livelihood benefits for various stakeholders.

Figure 1
Figure1Map of the study area.

Figure 2
Figure 2 climate diagram of Mekelle, northern ethiopia.monthly average for the years 2019 to 2022.

Table 1
effect of bamboo species, season of the year and their interactions on growth parameters of bamboo species (anoVa).

Table 2
Mean values of new emergent shoots and culm height (m) for each bamboo species across different seasons.thesamerow indicate significant differences among growth parameters in the season at p ≤ 0.05 between these nodes are called internodes.While most bamboo species have hollow internodes, some have solid ones.The length of the internodes can directly or indirectly indicate the quality of a bamboo product used for various purposes.In the present study, significant differences were observed in the internode length among the selected bamboo species.B. bambos and B. vulgaris exhibited longer internodes compared to P. edulis, as indicated in Table3.However, no statistically significant difference was found between O. abyssinica and P. edulis.The internode length of our studied bamboo species was similar to that of other bamboo species studied in West Hararghe

Table 3
Means comparisons between treatments at 0.05 significant levels Means with the same letter are not significantly different.av.nes = average of new emerging shoots; av.ch (m)=average of culm height in meter; av.cd (cm)= average of culm diameter in centimeter; average internode length