The potentials of enclosures in increasing woody biomass & regeneration
(A case study of Begasheka and Debrekidan watersheds, Tigray, northern Ethiopia)
THE STUDY SITES
The study was conducted in Begasheka and Debreikidan watersheds, Tigray, northern
Ethiopia (Fig. 2)
1
Faculty of Dryland Agriculture and Natural Resources, Mekelle University, P.O.Box
231, Mekelle, Ethiopia
* Corresponding author: e-mail: ermias8@yahoo.com
Fax: +251 344 409304
Table 1 Life forms (from Debrekidan watershed) indicating regeneration status of
four dominate species
INTRODUCTION
Area closure development is one of the most commonly practiced
strategies to restore degraded dryland environments in most part of
Northern Ethiopia. However,
•Performance of closures are not well studied,
•High scarcity of fuel wood in the area, competes with protection
•Unwise utilization of resource developed after rehabilitation
Therefore, it was necessary to study the impact of area enclosures on
enhancing woody biomass accumulation, & regeneration pattern in order
to determine future development of enclosures.
Fig. 2 The study sites: Debrekidan (right-top)
and Begasheka (right-bottom) on the map of
Tigray
Plant name
Number of
seedlings
Number of
saplings
Becium grandifoliume
Dodonea Angstofolia
Euclea shcimpri
Acacia saligna
All species
238
57
22
10
399
5
64
85
32
243
METHODS
The procedures followed in the study is summarized in Fig. 3
Watersheds delineated using
GPS
Random plots generated using
excel
All woody plants
400
500
400
300
200
100
300
200
100
0
0
1
<0.3cm
Plot centers navigated using GPS
Number of
trees
2
17
30
10
89
All woody plants
No. of individuals
General:
Life forms 19 woody plant species were identified and the life form
composition is indicated in table 1
number of individuals
Ermias Aynekulu1* Emiru Birhane1 and Nigussu Begashaw1
0.3-5cm
diameter class
2
>5cm
3
4
5
Diameter class (cm)
Fig. 5 The structural composition of the all species was found to be healthy in
both Debrekidan (left) and Begasheka (right) watersheds
Inventory made on each plot
DSH vs Biomass
Fresh & oven-dried wt. of
samples taken based on
diameter class
6
DSH vs Biomass
Biomass & regeneration in the
enclosures
Fig. 1 Impact of enclousre in vegetation cover in Begasheka watershed: Unclosed
& degraded area (left) and enclousre (about 10 years) showing restoration of
vegetation (right).
Objective:
General Investigate the role of enclosures in rehabilitating degraded
drylands that would ultimately offer viable promises for both
environmental & socio-economic benefits to the society.
Specific
•Estimate the biomass accumulated in the enclosures in the study area
•Assess regeneration of species in the enclosures
Biomass (kg)
Regeneration &
diversity of species
analyzed
Fig. 3 Schematic diagram depicting the major
process of the study
2
y = -0,0223x + 0,7129x - 0,0282
R2 = 0,5552
7
Fig. 4 Biomass field data collection
(top and bottom)
From the two watersheds, 45 plots with a radius of 5.6 m were used in this study and
laid down randomly in the enclosures. Height, diameter at stump height (DSH),
diameter at breast height (DBH), Crown diameter, number, identity and life forms
were recorded. Single tree-sampling method, destructive, was used to estimate the
above ground woody biomass of each species. Sample trees were cut, dried in oven to
estimate their moisture content and biomass.
RESULTS
Summery
Biomass produced in the Begasheka and Debre-kidan were 6.86 ton/ha and 3.8 ton/ha
respectively.
745 individuals representing 30 species & 731 individuals representing 19 species
were found in Begasheka & Debre-kidan respectively.
Fig. 6 Diameter at Stump Height (DSH)
poorly explain the variability in biomass
(example from Debrekidan watershed)
5
4
3
2
1
0
0
5
10
15
20
DSH (cm)
CONCLUSION
From this reach it was possible to draw the following two major conclusions:
•The enclosures in both sites haven given a considerable amount of biomass
production & regeneration capacity which can offer some socio-economic
benefit in addition to the environmental service to the community
•Though, the regeneration pattern of most species in the enclosures is
expanding type, some species like Senna sengueana, Mytenus senegalnesis, & Olea
africana formed distorted type of natural regeneration curve, which is an
indicator of interference.