Tree Species Composition and Structure of a Vegetation Plot in a Montane Forest in the Department of Amazonas, Peru

Abstract

The diversity and floristic composition of a primeval forest was studied, located in the district of Yambrasbamba–Bongará–Amazonas, delimiting a 1 ha area, and at an altitude of 1890 m.a.s.l. All individuals with diameter at breast height (DBH) ≥ 10 cm were inventoried. The plant diversity in the area was measured and a description of its composition and floristic structure was made. The following were recorded: a total of 640 trees distributed in 39 families, 60 genera and 152 species. The value of the Simpson’s index (D) was 0.974 and that of the Shannon–Wiener index was 4.264, indicating that the species had a high abundance of individuals. In turn, Fisher’s alpha value (α) was 23.744, indicating a regular diversity in montane forests in relation to different altitudinal gradients. The families with the highest number of individuals were Melastomataceae, Rubiaceae, Euphorbiaceae, Phyllanthaceae, and Lauraceae. The most abundant species were Alchornea acutifolia Müll.Arg. with 47 individuals (7.34%), Chimarrhis glabriflora Ducke with 39 individuals (6.09%), Hieronyma alchorneoides Allemão with 39 individuals (6.09%), and Cyathea lasiosora (Kuhn) Domin with 33 individuals (5.16%). A comparative analysis was carried out of plots of montane and premontane forests, and the studied plot presented had the third-highest register of families and genera, behind the plots studied in the provinces of Oxapampa and Chanchamayo.

1. Introduction

Indiscriminate logging is endangering the natural succession dynamics of forests, driven by the economic importance of the timber industry in the global market (annually, USD 450 billion) [1]. Additional threats include mining and oil industries, land use changes, forest fires, and excessive grazing [2,3].

Mountain forests, which give rise to the most diverse biological ecosystems and, at the same time, provide numerous essential services, cover up 12.3% of the Earth’s surface [4]. For example, they harbor 80% of the biodiversity of flora and fauna species and play a fundamental role in the global regulation of hydrological cycles [5,6]. Additionally, these forests mitigate the effects of climate change by capturing 13% of carbon dioxide (CO₂) emissions produced by anthropogenic activities [7].

Currently, various international institutions are making efforts, such as the United Nations Sustainable Development Goals (SDGs-2030), the Aichi Biodiversity Targets, the United Nations Framework Convention on Climate Change (UNFCCC), and the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), which seek to promote mountain biodiversity conservation as a potent alternative to mitigate climate change [8,9].

The world is facing increasing environmental degradation, jeopardizing the sustainability and floristic diversity (alpha and beta) of forests. In this context, Private Conservation Areas (PCAs) are innovative initiatives by national authorities to preserve representative samples of natural ecosystems [10]. Peru has 62 PCAs, making it one of the only two countries in South America where local communities create and manage them through sustainable natural resource use [11].

Peru boasts a vast amount of biological biodiversity, including mountain forests (located at an altitude between 1500–3500 m above sea level) that harbor a significant amount of worldwide flora and fauna [12]. Peruvian Amazon forests offer a great diversity of species groups due to their megadiverse ecosystems.

Currently, there are several Permanent Plots (PPs) for studying ecosystem vegetation [13,14]. Relatively small changes in the structure and/or function of these forests can have global consequences on biodiversity, carbon cycling, and climate change. These 1 ha plots are established for the purpose of investigating ecological aspects and forest management issues only and the trees studied have a DBH ≥ 10 cm [15].

In Peru, and especially in the department of Amazonas, very little is known about the structure and composition of tree species in montane forests, for the same reason as in the Amazon Region: there is only one PP, reporting 395 individuals distributed in 22 families, 27 genera, and 29 species [16]. However, various ecosystems can be found due to their geographical location, altitude, and climate. Precisely within this region, at an altitude between 1750 to 1900 m above sea level in the peasant community of Yambrasbamba (Bongará Province), is located the Private Conservation Area Pampa del Burro (ACPPB for its abbreviation in Spanish) covering an area of 2776.96 hectares [17]. This place stands out because five new species of orchids of the genus Epidendrum have recently been discovered [17]. Consequently, great genetic potential is evidenced, and it is necessary to continue with exploratory research to record the floristic diversity of this Private Conservation Area (PCA).

Given the need for information on the montane forests of the region, it was decided to construct a permanent research plot; our consideration of the plot size (1 ha) had to do with the characteristics of the Sample Unit (SU), since it must have the capacity to reflect the existence of species without underestimating their quantity. The statistical criterion used to determine the size of 1 ha was the behavior of the species–area curve, which inflects at the point where a significant number of new species records are no longer added to the SU.

With this expectation, the purpose of this research was to understand the floristic diversity in a PCA with permanent vegetation of the type of mountain forest. The main objective was to recognize the diversity and floristic composition of the primeval forest in the 1 ha study plot.

2. Materials and Methods

2.1. Study Area

The study area is a primeval forest conserved for 500 years within the Private Conservation Area (PCA) Pampa del Burro, in the district of Yambrasbamba, Bongará province, Amazonas department, Peru, between coordinates 172,309 E and 9,379,615 N, at an altitude of 1890 m above sea level.

2.2. Establishment of Permanent Plot

Once the plot was established, the field manual for remeasurement and establishment of plots was followed according to the standard used by [15].

1. Delimitation of the Plot

A square shape was applied to the permanent plot, as its edge is manageable. PVC pipes were used at each corner to mark the plot, forming a square of 100 × 100 m. Subplots were constructed with one-inch PVC pipe. Measurements were carried out with the aid of a compass to determine the direction and a clinometer (device that corrects distances on inclined terrain).

2. Marking in the Vegetation

All individuals with diameter at breast height (DBH) greater than or equal to 10 cm were located after delimitation. For each tree surveyed, height values were also measured and then marked with a plate located 1.8 m above the ground.

3. Collection of Botanical Material

Vegetative samples were taken to determine each surveyed species. Morphological characteristics of each species (resin, color, odor, latex, and taste) were considered, as well as exudates or aromas on their bark to facilitate identification, and then the samples were preserved in 96° alcohol. The collected samples were deposited in the KUELAP herbarium of the facultad de Ingeniería y Ciencias Agrarias de la Universidad Nacional Toribio Rodríguez de Mendoza de Amazonas (Faculty of Engineering and Agricultural Sciences of the National University Toribio Rodríguez de Mendoza de Amazonas).

2.3. Processing of Botanical Material

The data were entered into a Microsoft Excel 2022 table of species, with the following information: tree code, botanical family, genus/species, circumference at breast height (CBH), total height, geographic coordinates “X”–“Y” (with respect to the horizontal and vertical axis of each subplot), and basal area.

The calculation of basal areas, absolute and relative abundances, absolute and relative frequencies, dominances, evenness, and importance value index (IVI) was carried out in Excel 2016 spreadsheets. The Shannon–Wiener index (to evaluate the equity or proportionality of species within the plot based on their abundance, the values of this index range from 1.5 to 3.5, up to 4.5); Simpson’s index (to determine the diversity of the plot, based on the most important species, its values range from 0 to 1); and Fisher’s alpha index (to compare the diversity of the plot against other plots) were calculated. Analysis was performed using Past 4.04 software. Additionally, a comparative analysis was conducted between the study plot and other plots studied in Peru.

• Shannon–Wiener Index (H′)

  $$H^{\prime }=\sum _{i=1}^s{p}_i{\log }_2{p}_i$$

  where

  H′ = Shannon–Wiener Index

  $$p_i=\frac{Numberofindividualsofspeciesi}{Totalnumberofindividualsinthesample}$$

  S = Total number of species
• Simpson’s Index

  $$D=\sum _{i=1}^s{p_i}^2$$

  where

  D = Simpson’s Index

  $$p_i=\frac{Numberofindividualsofspeciesi}{Totalnumberofindividualsinthesample}$$

  S = Total number of species
• Fisher’s Diversity Index

  $$S=\alpha \ln \left(\frac{1+N}{\alpha }\right)$$

  where

  S = Total number of species

  α = Fisher diversity index

  N = Total number of individuals

3. Results

3.1. Structure and Generalities of Forest Type

The plot presented a total of 640 individuals (

Table 1. General results of structure and diversity of the 1 ha montane forest plot in the Pampa del Burro PCA.

Plot	Number of Individuals	Total Basal Area (m2)	Number of Families	Number of Genera	Number of Species	Evenness Coefficient	Simpson’s Index	Shannon–Wiener Index	Fisher’s α
Montane Forest	640	201.06	39	60	152	0.24	0.974	4.264	23.744

). The total basal area was 201.06 ${\mathrm{m}}^2$, which is explained because the plot generally recorded more medium-sized trees between 28.89–45.28 cm DBH.

Figure 1 illustrates the structure of the forest type based on DBH and the number of individuals found in the 1 ha plot. The forest type exhibits a significant number of small trees (12.50–28.89 cm DBH), but also shows a much higher frequency of trees between 28.90–61.67 cm DBH. There is an abundance of Alchornea acutifolia Müll.Arg. species (total basal area 2045.41 m²) and, to a lesser extent, Siparuna tomentosa (Ruiz and Pav.) A.DC. Miconia pterocaulon Triana, Miconia astroplocama Donn.Sm., and Gordonia fruticosa (Schrad.) H.Keng species (total DBH < 28.90 cm).

The frequency of large trees (110.84–160.00 cm DBH) is much lower (28 individuals). In the plot, the largest trees are individuals of Ficus maxima Mill. species (DBH = 160 cm), Clusia ducuoides Engl. (DBH = 152 cm), and Hieronyma oblonga (Tul.) Müll.Arg. (DBH = 140 cm).

3.2. Diversity

The plot presented 152 species (Table 1). To verify if the plot is more diverse, indices were calculated; according to the Fisher’s α, Simpson’s, and Shannon–Wiener indices, the plot is diverse.

3.3. Species–Area Curve

The species–area curve (Figure 2) was obtained using the EstimateS program Version 9.1 [18], which helped us to obtain the statistical average of the species richness in the forest. Then, the species–area curve was plotted using the STATISTICA program Version 6 [19] and the Clench equation V2 = (a × v1)/(1 + (b × v1)) was determined, which helped us to find the asymptote (a/b), whose value represents the number of estimated species in the studied forest [20].

3.4. Mixing Coefficient

The mixing coefficient, which shows the relationship between the total number of individuals and species in the analyzed plot, was 1:4 (0.2375). This means that it was possible to find one different species for every four sampled individuals.

3.5. Diversity Index, Evenness, and Dominance

The Simpson’s index (D) calculated for the plot evaluated in the Pampa del Burro PCA was 0.974, while the value of the Shannon–Wiener index was 4.264. For the same plot, the Margalef species richness index was 4.765 and the evenness was 0.849. The value of the Fisher’s alpha index (α) was 23.744.

3.6. Floristic Composition

Most Abundant Families, Genera, and Species

The six most abundant families (number of individuals ≥ 10) found in the plot were Lauraceae with 87 individuals (13.59%), Phyllanthaceae with 69 individuals (10.78%), Euphorbiaceae with 60 individuals (9.38%), Rubiaceae with 56 individuals (8.75%), Melastomataceae with 49 individuals (7.66%), and Sapotaceae with 39 individuals (6.09%); together, they accounted for more than 50% of the individuals found.

The five most abundant genera (number of individuals ≥ 20) found in the plot were Hieronyma with 69 individuals (10.78%), Alchornea with 57 individuals (8.91%), Chimarrhis with 51 individuals (7.97%), Miconia with 45 individuals (7.03%), and Chrysophyllum with 49 individuals (7.66%); together, they represented 40.78% of the individuals found.

The most abundant species (number of individuals ≥ 10) found in the plot were Alchornea acutifolia Müll.Arg. with 47 individuals (7.34%), Chimarrhis glabriflora Ducke with 39 individuals (6.09%), Hieronyma alchorneoides Allemão with 39 individuals (6.09%), Cyathea lasiosora (Kuhn) Domin with 33 individuals (5.16%), Chrysophyllum sanguinolentum (Pierre) Baehni with 23 individuals (3.59%), Clusia ducuoides Engl. with 20 individuals (3.13%), and Hieronyma sp. with 20 individuals (3.13%); together, they represented 34.53% of the individuals found. In the installed plot, 11.72% of the recorded species were represented by only one individual.

3.7. Structure Analysis

1. Horizontal Structure

For the horizontal structure analysis, the Importance Value Index (IVI) and the distribution by diameter, altitude, and basal area classes were calculated.

(a) Relative Abundance

The five most abundant species, in decreasing order, were Alchornea acutifolia Müll.Arg. with 47 individuals (7.34%), Chimarrhis glabriflora Ducke with 39 individuals (6.09%), Hieronyma alchorneoides Allemão with 39 individuals (6.09%), Cyathea lasiosora (Kuhn) Domin with 33 individuals (5.16%), and Chrysophyllum sanguinolentum (Pierre) Baehni with 23 individuals (3.59%).

(b) Relative Frequency

The five species recorded with the highest frequency in the 25 evaluated subplots were Alchornea acutifolia Müll.Arg. (5.05%), Hieronyma alchorneoides Allemão (4.09%), Chimarrhis glabriflora Ducke (3.85%), Cyathea lasiosora (Kuhn) Domin (3.37%), and Nectandra laurel Klotzsch ex Nees (3.37%).

(c) Relative Dominance

The five most dominant species were Alchornea acutifolia Müll.Arg. with 2045.41 m² (10.71%), Hieronyma alchorneoides Allemão with 905.51 m² (4.74%), Hieronyma sp. with 885.68 m² (4.64%), Chimarrhis glabriflora Ducke with 772.50 m² (4.04%), and Chrysophyllum sanguinolentum (Pierre) Baehni with 742.70 m² (3.89%).

3.8. Importance Value Index

The five species with the highest ecological weight (based on their abundance, frequency, and dominance) were Alchornea acutifolia Müll.Arg. (23.10%), Hieronyma alchorneoides Allemão (14.92%), Chimarrhis glabriflora Ducke (13.98%), Cyathea lasiosora (Kuhn) Domin (11.55%), and Chrysophyllum sanguinolentum (Pierre) Baehni (10.37%).

2. Vertical Structure

(a) Distribution of Individuals by Diameter Class

The individuals have been divided into nine diameter classes according to the DBH record (

Table 2. Ranges and frequencies of diameter classes of individuals recorded in the Pampa del Burro PCA.

Diameter Class	Range (cm)	Number of Individuals	Absolute Frequency (%)	Relative Frequency (%)
I	[12.50–28.89]	22	3.44%	3.44%
II	(28.89–45.28]	234	36.56%	40.00%
III	(45.28–61.67]	185	28.91%	68.91%
IV	(61.67–78.06]	96	15.00%	83.91%
V	(78.06–94.44]	43	6.72%	90.63%
VI	(94.44–110.83]	32	5.00%	95.63%
VII	(110.83–127.22]	21	3.28%	98.91%
VIII	(127.22–143.61]	5	0.78%	99.69%
IX	(143.61–160.00]	2	0.31%	100.00%
Total		640	100.00%

). Table 2 shows that the first four diameter classes (12.50 to 78.08 cm) contain 83.91% of the individuals (537 individuals), while the last two classes (127.22 to 160.00 cm) have only seven individuals (1.09%). According to the minimum (12.50 cm) and maximum DBH (160.00 cm) recorded, these corresponded to the species Chimarrhis glabriflora Ducke and Ficus maxima Mill., respectively. Additionally, it can be said that diameter class II, ranging from 28.89 to 45.28, is the most prominent, and the number of individuals per diameter class decreases as the DBH of the individual increases.

(b) Distribution of Individuals by Altitudinal Class

Table 3. Ranges and frequencies of altitudinal classes of individuals recorded in the Pampa del Burro PCA.

Altitudinal Class	Range (cm)	Number of Individuals	Frequency (%)	Cumulative Frequency (%)
I	[4.00–13.11]	285	44.67%	44.67%
II	(13.11–22.22]	315	49.37%	94.04%
III	(22.22–31.33]	33	5.17%	99.22%
IV	(31.33–40.44]	1	0.16%	99.37%
V	(40.44–49.56]	0	0.00%	99.37%
VI	(49.56–58.67]	0	0.00%	99.37%
VII	(58.67–67.78]	2	0.31%	99.69%
VIII	(67.78–76.89]	1	0.16%	99.84%
IX	(76.89–86.00]	1	0.16%	100.00%
Total		638	100.00%

and Figure 3 show the composition of nine altitudinal classes of the individuals recorded in the plot. The results indicate that classes I and II (between 4.00–22.22 m) concentrate 94.04% of the individuals (600 individuals). It is observed that only five individuals are concentrated between classes IV to IX, representing 0.78%. According to the minimum (4.00 m) and maximum height (86.00 m) recorded, these values correspond to the species Cyathea lasiosora (Kuhn) Domin and Myrcia minutiflora Sagot, respectively. Additionally, it can be observed that height class II, ranging from 13.11–22.22 m, is the most predominant, and the number of individuals decreases as the height of the individuals increases.

(c) Distribution of Individuals by Basal Area Class

Table 4. Ranges and frequencies of basal area classes of individuals recorded in the Pampa del Burro PCA.

Basal Area Class	Range (m2)	Number of Individuals	Frequency (%)	Cumulative Frequency (%)
I	[1.23–23.43]	363	56.72%	56.72%
II	(23.43–45.64]	165	25.78%	82.50%
III	(45.64–67.84]	47	7.34%	89.84%
IV	(67.84–90.04]	29	4.53%	94.38%
V	(90.04–112.25]	26	4.06%	98.44%
VI	(112.25–134.45]	4	0.63%	99.06%
VII	(134.45–156.65]	4	0.63%	99.69%
VIII	(156.65–178.86]	0	0.00%	99.69%
IX	(178.86–201.06]	2	0.31%	100.00%
Total		640	100.00%

and Figure 4 show the distribution of individuals by basal area class in the plot. The results indicate that between classes I and II (between 1.23 to 45.64 cm), 82.50% of the individuals are concentrated (528 individuals), while between classes 6 to 9, 1.56% of the individuals are concentrated (10 individuals). According to the minimum (1.23 m²) and maximum basal area (201.06 m²) recorded, these correspond to the species Chimarrhis glabriflora Ducke and Ficus maxima Mill., respectively. Additionally, it can be observed that basal area class I, ranging from 1.23–23.43, is the most predominant.

(d) Comparative Analysis Between the Pampa del Burro PCA Plot (P-PB) and Other Plots Established in Montane Forests Across the Country

Table 5. Comparison of abundance and diversity of nine permanent plots studied in montane and premontane forests of Peru.

Reference	PP Location	PP Abbreviation	Life Zone	Altitude (m.a.s.l.)	No. of Ind	No. of Fam	No. of Gen.	No. of Spp	CM	Shannon–Wiener I.	Fisher’s I.
Current Study	AM-Yambrasbamba	P-PB	bh-M	1890	640	39	60	152	0.238	4.264	23.74
[16]	AM-San Carlos	P-SC	bh-MB	2158	395	22	27	29	0.073	2.62	7.21
[14]	JU-Puyu Sacha Alto	P-PA	bh-MB	2770	480	22	27	45	0.094	-	12.16
	JU-Puyu Sacha Ribera	P-PR	bh-MB	2275	576	38	57	112	0.194	-	41.47
	JU-Puyu Sacha Ladera	P-PL2	bh-MB	2078	696	48	74	146	0.210	-	56.33
	JU-Génova Cumbre	P-GC	bh-P	1150	508	40	82	109	0.215	-	42.59
	JU-Génova Terraza 1	P-GS	bh-P	1150	512	32	52	70	0.137	-	21.93
	JU-Génova Ladera	P-GL	bh-P	1075	425	28	55	72	0.169	-	24.87
[21]	JU-Puyu Sacha	P-PS	bh-MB	2060	638	28	37	52	0.08	-	13.38

and Figure 5 present the richness of the families, genera, and species in nine permanent plots (1 ha) established in montane and premontane forests of Peru. It is observed that the present study has the third-highest record of families (39) and genera (60), ranking only behind plots studied in the Peruvian central jungle (montane stratum: Puyu Sacha Ladera (P-PA) and premontane stratum: Génova Cumbre (P-GC)). The number of species recorded and identified in the permanent plot of this study is higher than any of the permanent plots presented in Table 5.

The clustering analysis based on the number of families of the nine compared permanent plots shows two well-defined groups. Group one comprises plots P-GS, P-GL, P-BS, P-SC, and P-PA, which are located in the montane and premontane strata (1075 to 2770 m.a.s.l.). Group 2 is formed by plots P-PB, P-PR, P-PL2, and P-GC, characterized by encompassing the highest number of species.

4. Discussion

4.1. Alpha Diversity and Floristic Composition

The findings from the permanent plot established in the Pampa del Burro PCA revealed an abundance of 640 individuals (DBH ≥ 10 cm) per hectare. This surpasseed the values reported for five out of six plots established in montane and premontane forests of the central Peruvian jungle, where the number of individuals ranged from 425 to 696 [14]. Furthermore, contrasting with other montane forests located in Bolivia and Ecuador, those forests exhibited a higher number of observed individuals. However, it is noteworthy that these studies recorded the floristic composition for the tree, shrub, and herbaceous strata, which increases the likelihood of finding a higher number of individuals [22,23]. According to the analysis of these studies, to better understand species diversity patterns, it is necessary to include all strata in future exploratory studies in the Pampa del Burro Private Conservation Area and in other areas of the country.

In the present study, the families with the highest number of species were Lauraceae (29 species), Myrtaceae (14 species), Melastomataceae (11 species), and Rubiaceae (9 species). These data are similar to the results of studies conducted in montane forests of protected natural areas in Oxapampa [24], the central jungle of Peru [14], Las Palmas-Chota [25], and El Sayo, Ecuador [26]. Moreover, it has also been reported that the Melastomataceae and Lauraceae families are generally very abundant in the mountainous areas of southern Bahia (Brazil) and Yunnan (China), respectively [27,28]. Overall, ref. [14] note that these families are predominant in montane forests and have a wide distribution, abundance, and diversity.

Plot P-PB, with an area of 1 ha (100 × 100 m = 10,000 m²), was divided into 25 subplots of 0.04 ha (20 × 20 m). In P-PB, 152 forest species were inventoried. From the species–area curve (Figure 2), the Clench equation V2 = (a × v1)/(1 + (b × v1)) was obtained, equal to y = (13.813 × x)/(1 + (0.053 × x)), where a = 13.813 and b = 0.053. Since 152 species were inventoried in P-PB and the estimated number of species in the forest was 261, then the estimated proportion of species recorded in the forest was 58%. If we have estimated species proportions higher than 70%, it means that the diversity of the forest has been captured [20]. In the case of P-PB, only 58% of the forest species have been recorded, so the size of the 1 ha plot was not sufficient to record the diversity; as such, it is recommended that another sampling unit be set up.

Based on the values of the Shannon–Wiener index (4.264) and Simpson’s index (0.994), it can be inferred that the diversity of the Pampa del Burro Private Conservation Area is high. The results of this study demonstrate the importance of the Pampa del Burro Private Conservation Area for the conservation of floristic diversity in the Amazonas region. Additionally, these results surpass those obtained for the El Sayo protective forest in Ecuador, which presented a Shannon–Wiener index of 3.39 (average diversity) [26], and for the montane forest of Lanchurán (Piura), where the Shannon–Wiener and Simpson’s indices were 2.552 and 0.908, respectively [29].

4.2. Structural Analysis

To assess stand structure, the Importance Value Index (IVI) and the distribution of individuals by diameter, height, and basal area classes were utilized. If we classify species by their IVI, Alchornea acutifolia Müll.Arg. (23.10% IVI), Hieronyma alchorneoides Allemão (14.92% IVI), and Chimarrhis glabriflora Ducke (13.98% IVI) emerge as the most dominant and ecologically important species in the montane forest of the Pampa del Burro Private Conservation Area. In this regard, ref. [30] asserts that species with high IVI values should be the focus of habitat conservation, management, and recovery plans. This is because their populations can sustain the ecosystems they grow in by creating microclimates that favor the germination of seeds of early succession species [31].

The analysis of diameter distribution reveals a J-shaped curve, with the highest number of individuals grouped in class II (DBH between 28.89–45.28 cm). This distribution pattern indicates that we are dealing with an uneven-aged stand with a greater number of relatively young individuals, since the number of individuals drastically decreases as we ascend in size classes [32,33,34]. The distribution of classes by height and basal area shows the same behavior as the diameter distribution, with the number of individuals decreasing in higher classes. This characteristic may indicate constant levels of regeneration [35].

4.3. Comparative Analysis of Montane Forests

Studies on diversity and floristic composition conducted at various altitudinal levels enrich and contribute to identifying the variations exhibited by tree species in their environment. Ref. [36] supports this by stating that altitudinal range variation affects floristic diversity. Similarly, ref. [37] points out that environmental variability attributed to altitudinal ranges plays a significant role in the presence of flora in any location.

Comparisons were made between montane and premontane forests in nine permanent plots (1 ha) to analyze diversity and floristic composition. The study plot (P-PB) exhibited a wide range of families (39) and genera (60) of tree species. Studies by [14] found a large number of families (48) and genera (74) in the plot (P-PL2), located in montane strata of the central Peruvian jungle; these findings are similar to those of the present study.

Lauraceae, Rubiaceae, and Melastomataceae were the families with the highest number of species in montane forests of protected areas in Oxapampa [24]. Consequently, these families are the most abundant within their floristic diversity, possibly due to the geographic location similarity of the study areas. According to [38], Melastomataceae and Rubiaceae are among the six most diverse angiosperm families in Neotropical montane forests, with altitudes ranging from 1500 to 3500 m.a.s.l., while Lauraceae was the family with the third-most species (17) in a premontane forest [14].

Furthermore, ref. [16] found a lower number of families (22) and genera (27) in a plot (P-SC) established in a montane forest in the Amazonas region, where the genera with the most species were Miconia and Cedrela. Compared to the nine plots, the present study had a greater diversity of species recorded and identified. This could indicate a higher floristic species-level affinity due to the wide distribution, abundance, and diversity in montane stratum forests.

5. Conclusions

The detailed survey of the P-PB plot of 1 ha of forest in the Pampa del Burro ACP shows a high alpha diversity with respect to other montane forests, making it a very diverse area among the montane forests of Peru.

For tree composition and diversity, the plot has the third-highest number of families (39) and genera (60) in Peru, placing it behind only the plots studied in similar ecosystems located in the provinces of Oxapampa and Chanchamayo.

Due to the floristic diversity present in the study area, it is recommended to carry out complementary studies related to its faunal diversity and to see how they relate to each other.

This research highlights the importance of avoiding and preventing deforestation in areas of protection, ecological conservation, and high biological diversity and of defining and implementing instruments that discourage unregulated occupation.