Changes in Regulating Ecosystem Services following Establishing Exclosures on Communal Grazing Lands in Ethiopia: A Synthesis
Table 4
Average (±SE, ) of species composition and diversity in exclosures and communal grazing lands and their differences.
Variables
Exclosure age (year)
Exclosures
Adjacent grazing lands
Differencesa
P valueb
Richnessc (number)
5
20.0 (1.7)
10.0 (0.3)
10.0
0.01
10
15.7 (1.8)
6.7 (4.1)
9.0
0.11
15
30.0 (6.8)
10.7 (2.7)
19.3
0.02
20
31.3 (4.2)
11.7 (4.8)
19.6
0.03
Diversity (Shannon-Wiener index)
5
1.4 (0.1)
1.3 (0.1)
0.1
0.17
10
1.4 (0.1)
0.7 (0.2)
0.7
0.01
15
2.0 (0.1)
0.9 (0.2)
1.1
0.00
20
2.1 (0.1)
1.4 (0.2)
0.7
0.00
Evenness (Shannon-Wiener index)
5
0.56 (0.04)
0.78 (0.03)
0.01
10
0.67 (0.03)
0.41 (0.10)
0.26
0.00
15
0.67 (0.03)
0.58 (0.12)
0.09
0.44
20
0.72 (0.05)
0.73 (0.04)
0.13
Herbaceous species (number)
5
2.7 (0.3)
0.7 (0.3)
2.0
0.01
10
2.0 (1.2)
1.3 (0.9)
0.7
0.67
15
3.0 (0.6)
0.7 (0.3)
2.3
0.02
20
4.7 (1.5)
1.3 (0.9)
3.3
0.12
Shrub species (number)
5
10.3 (1.7)
5.3 (0.7)
5.0
0.04
10
7.7 (0.9)
3.7 (2.3)
4.0
0.18
15
15.7 (1.8)
6.3 (1.7)
9.3
0.01
20
14.7 (1.8)
6.7 (2.2)
8.0
0.04
Tree species (number)
5
4.0 (0.6)
2.0 (0.6)
2.0
0.07
10
4.0 (0.6)
1.0 (0.6)
3.0
0.02
15
8.0 (3.1)
2.7 (0.7)
5.3
0.16
20
8.0 (1.0)
3.0 (1.0)
5.0
0.02
Economically important species (number)
5
6.3 (0.9)
2.7 (0.9)
3.7
0.04
10
5.0 (1.0)
2.0 (0.6)
3.0
0.06
15
9.0 (2.1)
4.0 (1.5)
5.0
0.12
20
8.0 (1.0)
2.7 (1.2)
5.3
0.03
Differences are calculated as exclosure values minus adjacent grazing land values. Differences in species richness are equivalent to the value of beta diversity provided that we did not encounter a species unique to the communal grazing lands. bThe P values are values obtained after paired t-test. cRichness refers the total number of plant species in an area including forbs, lianas, and grasses.