East African Journal of Environment and Natural Effect of Disturbances on Non-tree Species Richness, Diversity, Distribution, and Abundance in Seasonally Dry Riverine of Engareolmotonyi, Arusha, Northern Highlands of Tanzania.

The non-tree species including shrubs, herbs, sedge, grasses, and ferns are vital for the sustainability of the forest ecosystem. The study was conducted at Engareolmotonyi seasonally dry riverine forest, in northern Tanzania to determine the non-tree species richness (S), diversity, distribution, and abundance. A total number of 20 plots measuring 20 x 20 m


INTRODUCTION
The nontree species including shrubs (woody plants), herbs, sedge, grasses, and ferns contribute to the species richness of the tropical forest (Gentry & Dodson, 1987).It has been pointed out that nontrees, especially shrubs are known as important tree regeneration niches (Rodriguez-Garcia et al., 2011;Holeksa, 2003).The nontree species richness, diversity, distribution, and abundance have been revealed to be affected by human activities (Miller & Lugo, 2009).It has been pointed out that in the forests, the competitive interactions within the herb layer can determine the initial success of plants occupying higher strata, including the regeneration of dominant overstory tree species (Elliott et al., 2014).Despite a growing awareness that the herbaceous layer serves a special role in maintaining the structure and function of forests, this stratum remains an underappreciated aspect of forest ecosystems (Gillian, 2007).The nontree species serve as part and parcel of the riverine forest ecosystem patterns, even though little is known about their spatial existence (Da Silva & Bates, 2002).The plant species abundance and distribution are being analysed on their various spatial scales.The relationship between species abundance and geographic distribution is a central issue in modern ecological studies, and the relationship has important implications for the understanding of community structure and for the description of biodiversity patterns (Leite & Lopes, 2001).The diversity and distribution of plants are being affected by a number of parameters (Fonge et al., 2013), most of them being human agents including firewood and pole collection, charcoal, encroachment, and livestock grazing.

ointed out th
t in the forests, the competitive interactions within the herb layer can determine the initial success of plants occupying higher strata, including the regeneration of dominant overstory tree species (Elliott et al., 2014).Despite a growing awareness that the herbaceous layer serves a special role in maintaining the structure and function of forests, this stratum remains an underappreciated aspect of forest ecosystems (Gillian, 2007).The nontree species serve as part and parcel of the riverine forest ecosystem patterns, even though little is known about their spatial existence (Da Silva & Bates, 2002).The plant species abundance and distribution are being analysed on their various spatial scales.The relationship between species abundance and geographic distribution is a central issue in modern ecological studies, and the relationship has important implications for the understanding of community structure and for the description of biodiversity patterns (Leite & Lopes, 2001).The diversity and distribution of plants are being affected by a number of parameters (Fonge et al., 2013), most of them being human agents including firewood and pole collection, charcoal, encroachment, and livestock grazing.

The disturbances in the ecosystem can be both natural and human-caused, of which human causes are known to be more severe.It has been pointed out that information on human disturbance in natural vegetation remains scarce as yet (up to now) to be studied thoroughly (Sebald et al., 2019).Human disturbances on natural ecosystems shape forest systems by manipulating their composition, structure, and functional processes (Dale et al., 2001).Indeed, the forests of Tanzania, just like in other countr The disturbances in the ecosystem can be both natural and human-caused, of which human causes are known to be more severe.It has been pointed out that information on human disturbance in natural vegetation remains scarce as yet (up to now) to be studied thoroughly (Sebald et al., 2019).Human disturbances on natural ecosystems shape forest systems by manipulating their composition, structure, and functional processes (Dale et al., 2001).Indeed, the forests of Tanzania, just like in other countries are shaped by their land-use and disturbance antiquity (history) (URT, 2006;Lupala et al., 2015).In Tanzania, human disturbances having the greatest effects on forests include wildfire, encroachment, livestock grazing, the introduction of invasive plants, cutting for poles, and firewood collection (Rijo et al., 2013).It has been pointed out that forest disturbances influence how much carbon is stored in trees or dead wood and the wild biological diversity (Obiri, 2011;Kayombo et al., 2020).This survey aimed to determine the nontree species richness, diversity, distribution and abundance of Engareolmotonyi seasonally dry riverine forest.
es are shaped by their land-use and disturbance antiquity (history) (URT, 2006;Lupala et al., 2015).In Tanzania, human disturbances having the greatest effects on forests include wildfire, encroachment, livestock grazing, the introduction of invasive plants, cutting for poles, and firewood collection (Rijo et al., 2013).It has been pointed out that forest disturbances influence how much carbon is stored in trees or dead wood and the wild biological diversity (Obiri, 2011;Kayombo et al., 2020).This survey aimed to determine the nontree species richness, diversity, distribution and abundance of Engareolmotonyi seasonally dry riverine forest.


MATERIAL AND METHODS


Description of the Study Area

The study was conducted at the Engareolmotonyi seasonally dry riverine forest, which is about 17km northwest of Arusha city centre, and 3km north of Arusha-Nairobi Road junction at Ngaramtoni township centre.The riverine forest is bordered by the Forestry Training Institutes, the Olmotonyi campus on the west and east, the Olmotonyi village on the northeast.


Climate

The climate temperature is chill during winter and warmer towards autumn and s

Description of the Study Area
The study was conducted at the Engareolmotonyi seasonally dry riverine forest, which is about 17km northwest of Arusha city centre, and 3km north of Arusha-Nairobi Road junction at Ngaramtoni township centre.The riverine forest is bordered by the Forestry Training Institutes, the Olmotonyi campus on the west and east, the Olmotonyi village on the northeast.

Climate
The climate temperature is chill during winter and warmer towards autumn and summer.In winter, there is much less rainfall in Arusha than in summer.This climate is considered to beCwb according to the Köppen-Geiger climate classification.The average annual temperature of Arusha is 19.2 °C (66.7 °F), with rainfall ≥ 1100 mm (43.4 inches) (URT, 2020).

much less rainfall in Arusha
han in summer.This climate is considered to beCwb according to the Köppen-Geiger climate classification.The average annual temperature of Arusha is 19.2 °C (66.7 °F), with rainfall ≥ 1100 mm (43.4 inches) (URT, 2020).


Socio-economic activities of the local community

The area is surrounded by people with different activities including very few employees at t

Socio-economic activities of the local community
The area is surrounded by people with different activities including very few employees at the Forestry Training Institute, Olmotonyi, Meru Plantation, SUA centre, and Olmotonyi primary school, while the majority are just small-scale business dealers and agriculture crop growers through Taungya provided plots and very small plots at their homesteads.The local community hasa very high demand for woody fuel and livestock feeding forest resources and thus spending as much time as possible to jump into the conserved area of the natural training riverine forest of Engareolmotonyi.

Forestry Traini
g Institute, Olmotonyi, Meru Plantation, SUA centre, and Olmotonyi primary school, while the majority are just small-scale business dealers and agriculture crop growers through Taungya provided plots and very small plots at their homesteads.The local community hasa very high demand for woody fuel and livestock feeding forest resources and thus spending as much time as possible to jump into the conserved area of the natural training riverine forest of Engareolmotonyi.


Data Collection and Analysis

In this study, 20 plots of 20 x 20 m 2 (400 m 2 ) w

Data Collection and Analysis
In this study, 20 plots of 20 x 20 m 2 (400 m 2 ) were purposefully established, within which the sub-plots of 1 x 1 m 2 plot were set for herbs, sedge, grasses, and ferns; whereas the 2 x 5 m 2 subplots were established to identify the woody nontrees.The nontrees were identified for their botanical names and counted for their number of individuals.The observed human disturbance was recorded.Shannon index (H') of diversity will be applied to determine the nontree species diversity as per Kent andCoker (1994) &Fayiah et al. (2018), using H' = -∑pilnpi; where H' = Shannon wiener diversity index (index of diversity); ∑ = summation; pi ratio of the number of stems of an individual plant species to the total number of all number of individuals of all species of the sampled area; ln=natural logarithm.The relative frequency (RF) will be calculated through

2 plot w
re set for herbs, sedge, grasses, and ferns; whereas the 2 x 5 m 2 subplots were established to identify the woody nontrees.The nontrees were identified for their botanical names and counted for their number of individuals.The observed human disturbance was recorded.Shannon index (H') of diversity will be applied to determine the nontree species diversi

as per Kent andCoker (1994) &Fayiah et al. (2018
, using H' = -∑pilnpi; where H' = Shannon wiener diversity index (index of diversity); ∑ = summation; pi ratio of the number of stems of an individual plant species to the total number of all number of individuals of all species of the sampled area; ln=natural logarithm.The relative frequency (RF) will be calculated through

. Where RF = relative frequency; FI = frequency (occurrence in plots) of an individual plant species; ∑FA = overall total frequency of all plants in the sampled area.

According to (Zerbo et al., 2016), the frequency of species is used to examine their dist . Where RF = relative frequency; FI = frequency (occurrence in plots) of an individual plant species; ∑FA = overall total frequency of all plants in the sampled area.
According to (Zerbo et al., 2016), the frequency of species is used to examine their distribution pattern in a specific area.The nontree species abundance will be determined grounded on the relative density as reflected from the density (Fayiah et al., 2018).

bution pattern in a specific
rea.The nontree species abundance will be determined grounded on the relative density as reflected from the density (Fayiah et al., 2018).

The human disturbances occurrence (frequency) percentage (relative frequency) was determined (Sebald et al., 2019).


RESULTS


Nontree plant species richness (S), Diversity, Distribution and Abundance

The nontrees include the lower growing woody plants (shrubs), while the non-woody plants include the herbs, grasses, sedges, and ferns.A total of 50 non-trees species were identified, and of those, 30 were non-woody, while from 10 families (Table 2), 20 were wood nontrees (2.394) (Table 1), from 18 families.Non-woody plants had the largest H' (2.260), followed by woody nontrees (Table 1 & 2).Also, the largest relative frequency (RF) was determined from the non-woody plants (Table 1& 3), while the nontree woody plants got less RF (Table 1 & 2).(Erythrococcafischeri Pax a process that also affects the non-trees as the trees fell on them.The natural disturbances were from wild mammals including Papio anubis (Oliv baboons.


Plate 2: Snaring (A), Cutting of poles & small trees (B) & baboons foot tracks (C)

The relative frequency of disturbances ranged from 37.50% ± 3.13%.These study findings revealed the most dominant disturbance as a footpath (s) with a relative frequency (RF) of 37.50%), followed by cutting (21.88.14%), livestock fodder collection (12 The human disturbances occurrence (frequency) percentage (relative frequency) was determined (Sebald et al., 2019).

Nontree plant species richness (S), Diversity, Distribution and Abundance
The nontrees include the lower growing woody plants (shrubs), while the non-woody plants include the herbs, grasses, sedges, and ferns.A total of 50 non-trees species were identified, and of those, 30 were non-woody, while from 10 families (Table 2), 20 were wood nontrees (2.394) (Table 1), from 18 families.Non-woody plants had the largest H' (2.260), followed by woody nontrees (Table 1 & 2).Also, the largest relative frequency (RF) was determined from the non-woody plants (Table 1& 3), while the nontree woody plants got less RF (Table 1 & 2).(Erythrococcafischeri Pax a process that also affects the non-trees as the trees fell on them.The natural disturbances were from wild mammals including Papio anubis (Oliv baboons.

ntact plots and firewood collection (19.38%), blue monkey and baboon foot
racks (6.25), and snares had an RF of 3.13% (Table 4).


DISCUSSION

The nontree richness woody plants (shrubs) species richness (S) of 20 with an H' of 2.394 and the S of 30 for the non-woody plants (herbs, grasses, sedge, and ferns) with the H' of 2.260 and an overall "S" of 50 and an over average of 2.327 as per Kent andCoker (1992) &Mligo (2018) Quoted Kent and Coker (1992), reveals high plant diversity, like the H' for high diversity ranges from 3.5 ± 1.5 and exceptionally exceeding 4.5 a scale of 5 ± 0. The high S and H' entails minimum disturbances (Whitworth et al., 2016).Moderate human use of forest ecosystems does not s

DISCUSSION
The nontree richness woody plants (shrubs) species richness (S) of 20 with an H' of 2.394 and the S of 30 for the non-woody plants (herbs, grasses, sedge, and ferns) with the H' of 2.260 and an overall "S" of 50 and an over average of 2.327 as per Kent andCoker (1992) &Mligo (2018) Quoted Kent and Coker (1992), reveals high plant diversity, like the H' for high diversity ranges from 3.5 ± 1.5 and exceptionally exceeding 4.5 a scale of 5 ± 0. The high S and H' entails minimum disturbances (Whitworth et al., 2016).Moderate human use of forest ecosystems does not significantly affect the plant diversity, indicating that tropical tree diversity is compatible with human exploitation as long as the vegetation covers are being maintained by making sure that there is sustainable use of forest margins (Gradstein et al., 2007).On the other hand, excessive disturbance may lead to the locally extinction of plant species.The plant species with the largest frequency and relative frequency is meant to be the most distributed within the study area (Santamaria, 2002;Burnham & Santanna, 2015), and hence ensuring longer survival against disturbances, unlike the plant which is very limited in distribution.The number of individuals is used to determine the density of biological species a result that may end up revealing the abundance (Maszura et al., 2018), in a sense that more stems of any particular plant or organism mean more quantity of such plant in a given spatial area.
gnificantly affect the plant diversity, indicating that tropical tree diversity is compatible with human exploitation as long as the vegetation covers are being maintained by making sure that there is sustainable use of forest margins (Gradstein et al., 2007).On the other hand, excessive disturbance may lead to the locally extinction of plant species.The plant species with the largest frequency and relative frequency is meant to be the most distributed within the study area (Santamaria, 2002;Burnham & Santanna, 2015), and hence ensuring longer survival against disturbances, unlike the plant which is very limited in distribution.The number of individuals is used to determine the density of biological species a result that may end up revealing the abundance (Maszura et al., 2018), in a sense that more stems of any particular plant or organism mean more quantity of such plant in a given spatial area.

It has been reported that a plant species with the highest density fits for being judged as the most dominant, while the one with the least density and relative densi It has been reported that a plant species with the highest density fits for being judged as the most dominant, while the one with the least density and relative density (RD) is meant to be the least abundant (Harcourt & Parks, 2005) et al., 2015).The 9.38% of the intact plots meant that most of the riverine forest had been impacted (90.62%) (Table 4), even though the disturbances were rather so minimal in most sample plots, they were recorded, and thus still leaving the area with high plant diversity.It has been reported

(RD) is meant to be the least abundant (Harcourt & Parks, 2005) et al., 2015).The
.38% of the intact plots meant that most of the riverine forest had been impacted (90.62%) (Table 4), even though the disturbances were rather so minimal in most sample plots, they were recorded, and thus still leaving the area with high plant diversity.It has been reported

that severe or excessive disturbances in tropical forests damage plant species of which some of them may become extinct in a particular locality.Alroy (2017), who conducted a study in the tropical forests of the world, found that all the disturbed habitats put together included 41% fewer species than the undisturbed forests.


CONCLUSION

The consequences of disturbances being natural or human-influenced factors (Table 4) have an effect on the biodiversity richness, diversity, distribution, and abundance in the natural forests.The removal of plants for firewood, livestock fodder, and wild animals snaring sticks reduces the richness (S) diversity and also limits the distribution extension and the quantity (density).Trampling by either human beings or wild animals form paths and or footpaths on which lower plants are being damaged.Snaring requires cleaning the snaring site (Plate 2C), a situation that leads to damage of both nontree plants and the small tree regeneration including seedlings and saplings.The most distributed plants (Table 3) have a chance for survival, while the limited (Table 3) ones in distribution are prone to damage in case disturbance occurs in such locations.The plants with more stems have a chance of being distributed in a large area and hence minor damage on a small area that severe or excessive disturbances in tropical forests damage plant species of which some of them may become extinct in a particular locality.Alroy (2017), who conducted a study in the tropical forests of the world, found that all the disturbed habitats put together included 41% fewer species than the undisturbed forests.

CONCLUSION
The consequences of disturbances being natural or human-influenced factors (Table 4) have an effect on the biodiversity richness, diversity, distribution, and abundance in the natural forests.The removal of plants for firewood, livestock fodder, and wild animals snaring sticks reduces the richness (S) diversity and also limits the distribution extension and the quantity (density).Trampling by either human beings or wild animals form paths and or footpaths on which lower plants are being damaged.Snaring requires cleaning the snaring site (Plate 2C), a situation that leads to damage of both nontree plants and the small tree regeneration including seedlings and saplings.The most distributed plants (Table 3) have a chance for survival, while the limited (Table 3) ones in distribution are prone to damage in case disturbance occurs in such locations.The plants with more stems have a chance of being distributed in a large area and hence minor damage on a small area may have fallen under less or no significant damage on such taxon.Engareolmotonyi seasonally dry riverine forest is a potential area offering various ecosystem services including; regulation of temperature, protection of water services, habitat for wildlife, windbreak, dead firewood, home for wildlife (mammals, reptiles, and insects), training facility (ecology, forest conservation, environmental conservation, ecotourism, forest survey, forest inventory).Further study is needed to explore the ecotourism attractions and establish ecotourism venture as a non-wood income-generating project, education to local people on the effect of collecting grasses herbs together with tree seedlings, participatory management of the site, and restoration of the degraded riverine forest areas (forest gaps).
may have fallen under less or no significant damage on such taxon.Engareolmotonyi seasonally dry riverine forest is a potential area offering various ecosystem services including; regulation of temperature, protection of water services, habitat for wildlife, windbreak, dead firewood, home for wildlife (mammals, reptiles, and insects), training facility (ecology, forest conservation, environmental conservation, ecotourism, forest survey, forest inventory).Further study is needed to explore the ecotourism attractions and establish ecotourism venture as a non-wood income-generating project, education to local people on the effect of collecting grasses herbs together with tree seedlings, participatory management of the site, and restoration of the degraded riverine forest areas (forest gaps).

Figure 1 :
1
Figure 1: Location of Engareolmotonyi seasonally dry riverine forest


Plate 1 :
1
Part of Seasonally dry Engareolmotonyi riverine forest







Table 1 : Nontree richness(S), Shannon index of diversity (H'), and relative frequency (RF)
1
Steane & Mabb.,andHoslundia opposite Vahl.The most abundant species had an RD of 26.121 ± 15.30.3, while the medium dominant had the RF of 10.290 ± 4.222, and the rest were the least abundant with an RD of ≤ 4.222 (Table2).In this study, the following nontree woody plants were the most abundant grounded on the calculated RD; Abutilon longicuspe Hochst and Grewia similis K.Schum.The moderately abundant include: Phytolacca dodecandra Cav., Pavonia urensL.'H., and Lippia javanica (Burm.f.) Spreng.The nontree woody plant families with the la

Plate 1 :
Part of Seasonally dry Engareolmotonyi riverine forest

Table 1 : Nontree richness(S), Shannon index of diversity (H'), and relative frequency (RF)
Steane & Mabb.,andHoslundia opposite Vahl.The most abundant species had an RD of 26.121 ± 15.30.3, while the medium dominant had the RF of 10.290 ± 4.222, and the rest were the least abundant with an RD of ≤ 4.222 (Table2).In this study, the following nontree woody plants were the most abundant grounded on the calculated RD; Abutilon longicuspe Hochst and Grewia similis K.Schum.The moderately abundant include: Phytolacca dodecandra Cav., Pavonia urensL.'H., and Lippia javanica (Burm.f.) Spreng.The nontree woody plant families with the largest number of species were; Malvaceae, Fabaceae, and Lamiaceae (Table2).6| This work is licensed under a Creative Commons Attribution 4.0 International License.

Table 3 : Non-woody plant species richness (S), relative frequency (RF), Shannon index of diversity (H'), density (D) and relative density
The disturbances were both human and natural caused.Human disturbances or activities are among agents affecting the nontree species richness, diversity, distribution and abundance.This study identified the following human disturbances at Engareolmotonyi seasonally dry riverine forest; footpaths affected the undergrowth's especially the herbs, seedlings, and grasses; cutting poles and very small trees (Plate 2B); Papio nubis (Olive baboon) and Cercopithecus mitis (Blue monkeys foot tracks) (Plate 2C); a collection of livestock fodder plants involved the removal of herbs, grasses together with shrubs.The collected fodder plants were Cynodondactylon (L.) Pers, and Setaria megaphylla (Steud.)Dur.&Schinz.The other disturbances were tree cutting for poles (Clausena anisata (Wild.)Hook), firewood (Croton macrostachyus Hochst.Ex Delile) and cutting poles and snaring sticks (Plate 2A)