1. Introduction

Biodiversity has three different levels, namely genetic diversity, species diversity and ecosystem diversity. Genetic diversity refers to various kinds of genetic information contained in every living organism. Genetic diversity occurs within and between populations of species. Species diversity refers to the diversity of living species [1] [2]. Ecosystem biodiversity relates to the diversity of habitats and environments, biotic communities, and ecological processes [3], [4].

The protected forest area typically has a high diversity of tree species. The existence of trees in forest vegetation is very beneficial for other living organisms, including preserving endangered species and their habitats [5] The trees vegetation in protected forest areas play an important role in the regulation of groundwater, minimize of flooding, erosion control and maintenance soil fertility [6-11].

Mount Masinggi protected forest in North Bolaang Mongondow has an area of 71.51 ha. The location is in two administrative regions, namely 50 ha in the Huntuk Village and 21.51 ha in the Mome village. At this time Mount Masinggi protected forest are experiencing a variety of disturbances as a result of community activities around the forest, such as the agriculture crop cultivation and harvesting of forest products in excess, thus resulting in fewer species of trees in protected forest areas. In this context, [12] recommends three lines of intervention, namely: (a) protecting native forests and the overall ecological corridors, and carry out enrichment planting along streams and rivers to protect waterways, (b) develop agro forestry practices for biodiversity conservation tree in the buffer zones of protected forest, and (c) the establishment of plantations in severely damaged areas. Specifically in relation to the conservation of tropical forest tree species, [13] proposed a model of timber plantation forest of local species. The purpose of this study was to analyze diversity of tree species and factors affecting species distribution.

2. Research Method

Research was conducted in the protected forest areas of the Gunung Masanggi, by using the Shannon-Weiner methode to calculate the species diversity indexc. Data collection is done by making a lane or transects lines [14]. Each sample rectangular plot with a width of 20 m and a length of 50 m, and tree species are observed in these plots. The sample plots are arranged systematically with distance between sample plots of 2 m in a transect line. The species observed are the trees which are their diameter Ø> 20 cm.

3. Results and Discussion

3.1. Biodversity of Trees Stage

3.1.1. Types and Number of Tree Stage of Plant

According to classification of the Shannon-Wiener index, there are three categories of species diversity, namely (1) Index > 3 is a high diversity, a high number of individual in each species, and its stability is high, (2). Index 1-3 is a moderate diversity, the moderate number of individual in each species, and its stability is moderate, (3) Index < 1 is a low diversity, the low number of individual in each species and its stability is low. These results indicate that there is a diversity of tree species in the protected forest areas of Gunung Masinggi, and is is found as many as 27 species of trees.

Many of the protected highland forests are currently experiencing strong pressure from habitat losses due to conversion of forests and uncontrolled hunting. If biodiversity in highland protected forests should be conserved, then the protected forest areas must be confirmed by concerning several of local endemic taxa [15]. [16] showed that the conversion of natural forests into cultivated land (home gardens and mixed gardens) that are managed by local people in the highlands of Ethiopia did not result in losses of tree species; changes occurred in terms of species distribution, species density and spatial composition of tree species. [17] Reported that the species diversity index may reflect the role of tropical forests in storing biomass, and may also mixed gardens of multi-strata. Both of these ecosystems can be developed more widely to encourage carbon sequestration from the atmosphere.

[18] Reported a negative correlation between the TDC (Tree Diversity Change index) and the distance to the transect lane. This suggests that the species-richness decreased in near-lane and that species richness was maintained only in inner-areas. The negative correlation of the RE index (diameter distribution index) and altitude and a deeper zone indicate that the dynamic replacement of humid-condition species by dry-condition species occur at lower altitudes. A loss in species diversity along with a change towards dry-condition species was observed throughout the forest areas. Zones at lower altitudes or at the forest edges are more sensitive to these dynamics processes. This suggests that changes in any ecosystem functions have been taken place and that a minimum extension of cloud forest is required to maintain the ecological processes necessary for the sustainability of cloud forest [18].

In Table it can be seen that there are as many as 27 species of trees with a total of 62 individual trees. Among these species there are 10 individuals of Irvingia malayana Olive. Ii is a tree species with the highest number in the region covering an area of 1.3 ha sample plots. This tree-species is suitable to the environmental conditions of undisturbed mixed dipterocarp forests up to 600 m altitude; usually it grows well on hillsides and ridges with clay soils to sandy soils.

Species of Pterocarpus indicus Willd., Pometia pinnata, Myristica sp. and Bintangor Calophylum soulatrii suggested the four individual trees. Pterocarpus indicus Willd is the pioneer species that grow best in open areas. It can grow well on the variety of soil types. Normally it is found up to 600 m altitude, but seems to thrive up to 1300 m altitude. Their populations have declined because of overexploitation, sometimes illegal exploitation of the timber as well as the general habitat losses.

Species Cananga odorata, Threma orientalis and Duabanga moluccana Bl. suggested the three individual trees. Species Garuga floribunda, Homalium foetidum, and Ficus sp. suggested two individual trees. While the 13 other tree species have the least number of individuals, each of them suggested only one individual tree. Presents the species of Irvingia malayana Oliv. with a highest of relative density (RD) of 16.11%. Species Pterocarpus indicus Willd., Pometia pinnata, Myristica sp. and Calophylum soulatrii is the second highest, each of which has a relative density (RD) of 4.84%. Species Cananga odorata, Threma orientalis, and Duabanga mollucana BI. each having a relative density value (RD) of 3.23%. A total of 13 other tree species suggested a lower relative density (RD) of 1.61%.

3.1.2. Frequency of the Tree-Stage Plant

Frequency is used to present proportion between the numbers of samples that contain a particular species to the total sample. The frequency of tree species is the amount of sample plots where the discovery of a certain species to all of observed sample plots.

In the Table presents the highest level of relative frequency of 16.04 % owned by Irvingia malayana Oliv., its frequency is 0.77. Species of Pterocarpus indicus Willd., Pometia pinnata, Myristica sp. and Calophylum soulatrii have a high relative-frequency of 6.46%. Species of Cananga odorata, Threma orientalis, and Duabanga mollucana BI, suggested a relative frequency of 4.79%. A total of 13 other tree species have a relatively lower frequency that is 1.67%.

At this observation, frequency suggests the magnitude of discovery of organisms in the community or ecosystem. A more number of sample plots in which a certain species is found, it means the greater frequency of this species in the Forest Protected Areas of Gunung Masinggi.

3.1.3. Dominance of the Tree-Stage Plan

Dominance is a term used to express coverage of the tree species. Expressed “Coverage” by using the canopy coverage or basal area. These parameters are part of parameters used to indicate the dominant plant species in a vegetation community. In the Table presents the dominance index and relative dominance of the tree species.

Table shows some species of trees, in which the top level of dominance among them is the species of Irvingia malayana Oliv.) DR=16.05%, species of Pterocarpus indicus Willd and Calophylum soulatrii suggested the DR of 8.92% and 8.81%, and species of Myristica sp.suggested DR of 7.69%.

3.1.4. Important Value Indexes (INP) of the Tree-Stage Plant

Importance Value Index (IVI) is a quantitative parameter that can be used to express the degree of species dominance (level of mastery) in a vegetation community [19]. The dominant species in a vegetation community will have an importance value index is high, so that the most dominant species of course suggests the greatest impostance value index [20].

Based on their Importance Value Index (IVI), the dominant tree species is species of Irvingia malayana Oliv. (IVI = 48.2%), Pterocarpus indicus Willd and the IVI of 221.83% and 21.72%, respectively. Species of Myristica sp. (IVI=20.6%), Pometia pinnata (IVI=17.86%). The two trees species with IVI=13.98% are Cananga odorata and Duabanga moluccana Bl. While the species of Threma orientalis and Moraceae suggested IVI values of 13.81% and 13.42, respectively.

3.1.5. Dominance Index (DI)

The Dominance index (DI) reflects the level of species dominance (mastery) in a vegetation community. The dominance in a vegetation community can be centralized on a single species, some species or in many species. The dominance of a species also reflects the tolerance and adaptation to their environment and the growth rate of regeneration in their habitat [21-23].

The Dominance Value Index (DI) of 0.0634 is obtained from the sum of Importance Value Index (IVI) of each species divided by the total IVI of all species found in the certain plot. This ID is included in the “low category”. This means that the dominance is centered on a few species [24]. Thus there are several dominant species in Sub-region of Protected Forest of Gunung Masinggi. These species are Irvingia malayana Olive. Pterocarpus indices Wild. Pometia pinnate, Myristica sp., Calophylum soulatrii, Cananga odorata, Threma orientalis, and Duabanga mollucana BI.

3.1.6. Species Diversity Base on Shannon-Weiner Index (H’)

Results of data analysis obtained in the field by using a plots sample shows the Shannon-Weiner diversity index (H') of 1.1930. Based on the classification of Shannon-Weiner diversity index, this value of diversity index is included in the category "medium", the number of individual tree of each species at the level of "medium" and the stability of the community is "moderate". For this category, the value of Shannon-Weiner index (H ') = 1-3.

The diversity of tree species in Sub-region of the Gunung Masinggi protected areas suggested the "moderate" diversity. This category can be considered "good-enough", the existing density of vegetation at this location is increasingly decreased due to the many illegal logging and illegal cultivation is going on in this sub-region. This can lead to decrease quality of micro-habitats for forest tree species [25], and ultimately degrade composition of tree species in the forest ecosystem [26].

3.2. Factors Affecting the Species Diversity

Various important ecological principles are included in the concept of biodiversity of tree species. The concept of diversity was used by ecologists as a way to look at the possibility of a feedback system, as the more high of biodiversity, the more diverse of food chain and a higher possibility of symbiotic mutualism, commensalism, parasitism and others, as well as increase the possibility to mitigate any negative impacts of climate change [27]. The consequence of this is the more stable of vegetation community with the more stable of weather conditions, usually have higher biodiversity, compared with communities facing a fluctuation of weather conditions or disturbances by human activities [28-30].

Climate changes suggested any serious impacts on the biodiversity of trees community in protected forest areas [31]. Diversity is a reflection of the stability of a community and ecosystem stability [32]. The higher of biodiversity, ecosystems usually also more stable [33].

Biodiversity concerns the diversity and relative abundance of species in the vegetation community, including forest ecosystems [34-36].

4. Conclusions

1. The total of 27 tree species in the protected forest areas of the Mount-Masanggi reflects the moderate species diversity of the vegetation community.The density of 27 species were encountered at 47.73 with a frequency of 4.8 tree, the important value index (IVI) is dominated by Irvingia malayana Oliv. (IVI=48.2%), Pterocarpus indicus Willd. (IVI = 21.83%), Calophylum soulatrii (IVI =21.72%); and the lowest dominance is Dryobalanops aromaticum (IVI = 5.91%). The nine species of trees with a level of dominance of 0.0634 are found in the vegetation community of the Mount-Masinggi protected forest. These species are Irvingia malayana Oliv., Pterocarpus indicus Willd, Aglaia sp., Myristica sp., Pometia pinnata, Cananga odorata, Duabanga moluccana Bl., Threma orientalis and Moraceae sp. The species diversity of tree phases based on the Shannon-Weiner Index (H') in the protected forests of the Mount-Masinggi is 1.1930. This suggests the level of biodiversity "moderate".

2. The climate is balanced or uniform can affect the diversity of species in a location otherwise unstable climate or human activities vary and will affect the growth of species diversity.