## 4 Discussion  
The forests of Pakistan, like other vegetation types, has variation in species composition and diversity due to topographic and edaphic variables. The current study outlines three major phytocenosis of _Monotheca buxifolia_ at different altitudinal ranges. The presence of _M. buxifolia_ as a dominant species with varying stem density explains the wide distribution of the species in the studied area. These results are more similar to the findings of [PERSON] et al. (2018, 2019), by reporting _M. buxifolia_ as a dominant tree species in the studied area. Prominent existence of this species was also observed by [PERSON] et al. (2017) and [PERSON] et al. (2019), working on _Olea ferruginea_ and _Quercus baloot_ vegetation, respectively. _O. ferruginea_ and _Acacia modesa_ were strong associates of the dominant species, with importance values that ranged from 2.40 \(\pm\) 1.28 to 7.82 \(\pm\) 2.20%. The remaining 24 species, including _Morus alba_, _Ficus palmata_, _Broussonteina papyrifera_, _Juglans regia_, _Pinus roxburghii_, etc., were poorly distributed (importance value 0.11 \(\pm\) 0.11 to 2.11 \(\pm\) 0.98%). _Pinus gerardiana_, _Prunus armeniaca_, _Pinus roxburghii_, _Ploenix dactylifera_, and _Punica granatum_ were positioned in high elevation, while _Dalbergia sissoo_, _Acacia nilotica_, _Alizia lebbeck_ and _Capparis decidua_ were more familiar in lower elevation. _Morus alba_, _Melia azadarach_, _Ficus palmata_, _Ailanthus altissima_, _Grewia oppositifolia_, and _Populus nigra_ were found in both lower and upper elevations. The distribution pattern of tree species in _Monotheca_ phytocenosis can be strongly linked with the  
Figure 3: Relationships between Basal area with volume and biomass carbon along different altitudinal gradients. Note. BAEI = Basal area at elevation zone-I, BAEII = Basal area at elevation zone-II, BAEI = Basal area at elevation zone-III, MBA = Mean basal area, VEI = Volume at elevation zone-I, VEII = Volume at elevation zone-II, VEIII = Volume at elevation zone-III, MV = Mean volume, BMCEI = Biomass carbon at elevation zone-I, BMCEII = Biomass carbon at elevation zone-II, BMCEIII = Biomass carbon at elevation zone-III, MBMC = Mean biomass carbon. findings of [PERSON] et al. [36] and [PERSON] et al. [37]. Exotic species such as _E. globulus_, _B. papyrifera_, and _A. altissima_ are introduced by locals and have negative ecological consequences for native species [55]. Removal of the invasive plants is highly recommended from the natural population for successful forest resource management [36]. Results of ANOVA and post hoc Tukey HSD revealed that Simpson index and richness of lower elevation had the highest diversity in comparison to middle and high elevation ranges. Log series and [PERSON]'s index had the same result: high diversity for lower elevation followed by higher elevation (Table 2). Data was collected at three different latitudinal ranges; forests at low elevation ranges were more dense and diverse. However, those forests which were located at higher altitudinal ranges are comparatively scarce. Decline in the tree density, basal area, and species richness with increasing altitude is significant in Himalayan forests [15; 56]. The current study observed a significant loss in vegetation along the altitudinal strata due to eco-physiological constraints, low temperature, and productivity [57]. In terms of the association between species diversity and elevation gradient, the current study supports the existing literature [17; 36; 37]. Our results suggest that being highly diversified holds a significant relationship with elevation. This may be attributed to several factors, such as temperature, precipitation, soil properties, and intensity of disturbance. The favorable association between plant species richness and altitudinal gradient has already been proven in various studies [4; 58; 59]; it revealed that species richness is highly influenced by altitudinal linked factors [60].