Highlights:
Diversity was higher for selection treatments than for thinning treatments.
In 10 years, tree structure maintained its hierarchical values of the importance index value index (IVI).
Pinus cooperi, P. durangensis and Quercus sideroxyla were the species with the highest IVI.
The volume removed by wood extraction was recovered with tree growth.
Introduction
Forest management involves decisions and activities for sustainable use, conservation and promotion of forest resources (Aguirre-Calderón, 2015). The objective of sustainable forest management is to meet the current needs of society without compromising the provision of ecosystem goods and services in the future (Aguirre-Calderón, 2015; Monarrez-Gonzalez et al., 2020).
In areas under forest management, silvicultural treatments modify forest structure, and therefore it is essential to know this, in combination with stand dynamics to guarantee sustainability (Castellanos-Bolaños et al., 2008). Tree structure, composition and diversity are characteristics that should be studied in managed forests, which can be modified by natural (fires, pests, diseases and droughts) and anthropogenic events (Guevara-Fisher et al., 2021; Hernández-Salas et al., 2013). This information provides information on the current condition of the forest and helps determining the appropriate silvicultural practices to conserve the attributes of forest ecosystems (Rendón-Pérez et al., 2021).
Silvicultural methods MMOBI (Mexican Management Method for Uneven-aged Forests) and SDM (Silvicultural Development Method) are applied in the forests of the state of Durango (northwestern Mexico). The MMOBI is aimed at the application of selective cutting, in groups or individually, to maintain an irregular structure composed of trees of different sizes on sites of low productivity. The SDM is carried out with periodic harvests to ensure the renewal of the forest, inducing tree mass to even-aged forests by applying regeneration clear-cuts or parent trees, and intensive clear-cuts such as thinning on sites where seasonal qualities are high (Santiago-Ramírez et al., 2019; Solís-Moreno et al., 2006; Soto-Cervantes et al., 2021).
Forest management needs information on diversity, tree structure, growth dynamics and forest productivity, which is collected from regular evaluations for the detection of changes generated by silvicultural practices (López-Hernández et al., 2017). Therefore, the objective of this study was to compare the diversity and tree structure of a temperate forest under the silvicultural treatments of selection and thinning in Durango, Mexico.
Materials and Methods
Study area
The study was carried out in five ejidos (La Victoria, La Ciudad, El Brillante, La Campana and San Esteban) in the town of El Salto, municipality of Pueblo Nuevo, Durango, northwestern Mexico, geographically framed between parallels 23° 42’, 34.48” and 23° 49’ 28.18” NL and meridians 105° 30’ 11.83” and 105° 40’ 6.56” WL in the Sierra Madre Occidental mountain range (Figure 1). The area has an average elevation between 2 500 and 2 900 m. Soil types are Lithosol, Cambisol and Regosol and the predominant texture is coarse to medium (Instituto Nacional de Estadística y Geografía [INEGI], 2015). The climates are (A)C(W2), C(W2), C(E)(M) and C(E)(W2) with average annual precipitation of 945.3 mm and average temperature of 11.5 °C (INEGI, 2009).
Data collection
We selected 12 sites with evidence of forest management using silvicultural methods of selection and thinning using the Permanent Sites of Forestry and Soil Research (SPIFyS), belonging to UMAFOR 1008. The sites were established in 2007 and 2008 (inventory 1), following the methodology described by Corral-Rivas et al. (2009). Two remeasurements were carried out five and 10 years later (inventory 2 and 3, respectively) using the guide for the establishment, monitoring and evaluation of permanent monitoring sites in productive forest landscapes (Corral-Rivas et al., 2013). The silvicultural treatment applied to each site differed according to the year of cutting from the management programs for each ejido (Table 1).
The size of the sites was 2 500 m2, from which the following tree measurement information was collected: number of trees, species, diameter at breast height (>7.5 cm) and total height (m). The forest communities in the region are composed of mixed forests of Pinus and Quercus, Juniperus, Arbutus and Alnus. The stands are second-growth subjected to forest exploitation for more than 100 years (Colín et al., 2018; Lujan-Soto et al., 2015).
Table 1 Sites analyzed according to silvicultural treatment applied in a temperate forest in the locality of El Salto, Pueblo Nuevo, Durango.
Site | Ejido | Inventory 1 | Inventory 2 | Inventory 3 | Cutting year |
---|---|---|---|---|---|
Selection | |||||
1 | La Victoria | 01/10/2007 | 21/11/2012 | 01/12/2017 | 2013 |
2 | La Victoria | 01/11/2007 | 27/11/2012 | 02/12/2017 | 2012 |
3 | La Ciudad | 01/03/2008 | 25/04/2013 | 02/07/2018 | 2009 |
4 | La Ciudad | 01/03/2008 | 19/04/2013 | 05/07/2018 | 2009 |
5 | La Campana | 01/03/2008 | 09/04/2013 | 26/06/2018 | 2008 |
6 | La Campana | 01/03/2008 | 15/04/2013 | 27/06/2018 | 2015 |
Thinning | |||||
7 | El Brillante | 01/12/2008 | 16/12/2013 | 21/09/2018 | 2009 |
8 | El Brillante | 01/12/2008 | 11/12/2013 | 23/09/2018 | 2012 |
9 | El Brillante | 01/12/2008 | 21/12/2013 | 05/10/2018 | 2009 |
10 | La Ciudad | 01/03/2008 | 20/04/2013 | 26/06/2018 | 2017 |
11 | San Esteban | 09/03/2008 | 04/04/2013 | 04/07/2018 | 2013 |
12 | La Campana | 01/03/2008 | 11/04/2013 | 28/06/2018 | 2009 |
Data analysis
Diversity
Species diversity for each treatment in each inventory was estimated with the Shannon diversity index (Hˊ) (Shannon & Weaver, 1949):
where,
ln = natural logarithm
pi = proportion of trees of species i found (obtained from the ratio ni/N)
ni = number of trees of species i
N = total number of trees
Values obtained using the Shannon index were compared with the Hutcheson's t diversity-abundance similarity or difference hypothesis test between selection and thinning treatments, in the three inventories (Corral-Rivas et al., 2005; Hernández-Salas et al., 2013; Solís-Moreno et al., 2006). Degrees of freedom (df) and variances were estimated with the following equations:
where,
Hˊ= diversity of site n
Var Hˊ= variance of site n
N = total number of trees of site n
S = number of species
Ecological parameters and importance value index
In each evaluation period and for each silvicultural treatment, the relative values of abundance, according to the number of trees; dominance, according to basal area; frequency, based on the presence of species; and importance value index (IVI), with the sum of the previous ecological indicators in percentage values from 0 to 300, and dividing the value by three (Alanís-Rodríguez et al., 2020), were determined for each tree species (Table 2).
Table 2 Estimated ecological parameters and importance value index of tree species.
Parameters and index | Formula | Variables |
---|---|---|
Relative abundance (RA) | RA=n/N*100 | n = number of individuals of species i |
𝑁 = total number of individuals | ||
Relative dominance (RD) | RD=g/G*100 | 𝑔 = basal area of species i |
𝐺 = total basal area | ||
Relative frequency (RF) | RF=m/M*100 | 𝑚 = frequency of species i in the sampling sites |
𝑀 = total number of sampling sites | ||
Importance value index (IVI) | IVI=(RA+RD+RF)/3 |
Volume
For most species recorded, the stem volume was determined using equations generated by the Forest Biometric System (SiBiFor) belonging to UMAFOR 1008 through the digital library of the biometric system for the planning of sustainable forest management of ecosystems with timber potential in Mexico, based on the equation of Schumacher and Hall; only for Arbutus spp. was the equation generated by Cruz-Cobos et al. (2016) (Table 3).
Table 3 Equations of the stem volume (V) for the species present in UMAFOR 1008 in the region of El Salto, Pueblo Nuevo, Durango.
Species | Equation | Author |
---|---|---|
Alnus firmifolia Fernald | V=0.000139*(DBH1.3542668)*(H1.2736221) | ITES-2016 |
Alnus jorullensis Kunth | V=0.0000862*(DBH1.8865539)*(H0.8017336) | ITES-2016 |
Arbutus spp. | V=0.0000116*(DBH2.078374)*(H0.501168) | Cruz-Cobos et al. (2016) |
Juniperus deppeana Steud. | V=0.0000759*(DBH1.9206334)*(H0.803164) | UJED-2016 |
Pinus cooperi C. E. Blanco | V=0.0000454*(DBH2.0745395)*(H0.8923251) | UJED-2016 |
Pinus durangensis Martínez | V=0.0000546*(DBH1.9482123)*(H0.9702588) | UJED-2016 |
Pinus leiophylla Schiede ex Schltdl. & Cham. | V=0.0000372*(DBH2.0194624)*(H1.0269951) | UJED-2016 |
Pinus strobiformis Engelm. | V=0.0000607*(DBH1.9179198)*(H0.9319899) | UJED-2016 |
Pinus teocote Schiede ex Schltdl. & Cham. | V=0.0000676*(DBH1.9076677)*(H0.9455744) | UJED-2016 |
Prunus serotina Ehrh. | V=0.0000862*(DBH1.8865539)*(H0.8017336) | ITES-2016 |
Quercus rugosa Née | V=0.0000373*(DBH2.0588513)*(H0.9271271) | UJED-2016 |
Quercus spp. | V=0.0000626*(DBH2.0409771)*(H0.7503735) | UJED-2016 |
Quercus sideroxyla Bonpl. | V=0.0000456*(DBH2.0193611)*(H0.8856513) | UJED-2016 |
DBH: diameter at breast height; H: total height. The ITES (Instituto Tecnológico de El Salto) and UJED (Universidad Juárez del Estado de Durango) equations can be consulted and downloaded at http://fcfposgrado.ujed.mx/sibifor/inicio/
Statistical analysis
The normal distribution of the data for each ecological parameter (abundance, dominance and frequency), IVI and forest volume was verified with the Shapiro-Wilk test and homogeneity of variances with the Levene test. Based on the normality result, a one-factor ANOVA (equality of means) or, instead, the non-parametric Kruskal-Wallis test (equality of medians) was used to determine if there are statistical changes among the inventories for each treatment and for the 12 sites; the significance level for the tests was α = 0.05. All analyses were performed in IBM SPSS Statistics 25.
Results
A total of 18 species belonging to six families and six genera were recorded for the three inventories. The families Pinaceae and Fagaceae and the genera Pinus and Quercus were the most representative with five species, followed by the family Ericaceae and the genus Arbutus with four species. Prunus serotina Ehrh. was the least representative species with one species (Table 4).
Table 4 Species and families recorded in the 12 study sites of a temperate forest for three inventories conducted over a 10-year period in the region of El Salto, Pueblo Nuevo, Durango.
Species | Common name | Family |
---|---|---|
Alnus firmifolia Fernald | Aliso | Betulaceae |
Alnus jorullensis Kunth | Aliso | Betulaceae |
Arbutus arizonica (A. Gray) Sarg. | Madroño de Arizona | Ericaceae |
Arbutus bicolor S. González, M. González & P. D. Sørensen | Madroño | Ericaceae |
Arbutus madrensis S. González | Madroño roñoso | Ericaceae |
Arbutus tessellata P. D. Sørensen | Madroño pegajoso | Ericaceae |
Juniperus deppeana Steud. | Táscate | Cupressaceae |
Pinus cooperi C. E. Blanco | Pino chino | Pinaceae |
Pinus durangensis Martínez | Ocote | Pinaceae |
Pinus leiophylla Schiede ex Schltdl. & Cham. | Pino prieto | Pinaceae |
Pinus strobiformis Engelm. | Pino blanco | Pinaceae |
Pinus teocote Schiede ex Schltdl. & Cham. | Pino colorado | Pinaceae |
Prunus serotina Ehrh. | Capulín | Rosaceae |
Quercus rugosa Née | Encino blanco | Fagaceae |
Quercus arizonica Sarg. | Roble de Arizona | Fagaceae |
Quercus crassifolia Bonpl. | Encino prieto | Fagaceae |
Quercus obtusata Bonpl. | Encino roble | Fagaceae |
Quercus sideroxyla Bonpl. | Encino colorado | Fagaceae |
Diversity
The area with selection treatment showed higher values in Shannon's diversity index (Hˊ) for the three inventories (Figure 2). Hutcheson's test revealed significant statistical differences among treatments in the three evaluation periods: inventory 1 (t = 2.87, t(α = 0.05, 962) = 1.98); inventory 2 (t = 3.73 t(α = 0.05, 907) = 1.98) and inventory 3 (t = 4.89 t(α=0.05, 1004) = 1.98).

Figure 2 Shannon diversity index (Hˊ) of a temperate forest under selection and thinning treatments, for three inventories conducted over a 10-year period in the region of El Salto, Pueblo Nuevo, Durango. In each inventory, different letters indicate significant difference according to Hutcheson's t-test (P = 0.05).
Ecological indicators
Sites with selection treatment
Abundance in the six sites with selection treatment decreased from 454 ± 55.12 trees∙ha-1 in inventory 1 a 426.67 ± 47.7 in inventory 2 but increased to 465.33 ± 46.98 trees∙ha-1 for inventory 3; these changes were not statistically significant (X2 = 0.012, gl = 2, P = 0.99). Figure 3A shows the behavior of the number of trees per diameter category in selection treatment, diameter categories in the three inventories show a normal trend in the data, characteristic of mature stands. In the first evaluation period there were 13 species, in the second period P. serotina was incorporated and finally in the third period there were 16 species with the incorporation of Arbutus arizonica (A. Gray) Sarg. and Arbutus tessellata P. D. Sørensen.
Basal area in inventory 1 recorded a total value of 24.1 ± 3.5 m2∙ha-1, decreased 0.77 m2∙ha-1 for inventory 2 and increased to 25.65 ± 3.24 m2∙ha-1 in inventory 3; statistically, these changes were not significant (X2 = 0.028, gl = 2, P = 0.98). In the final period, basal area increased 6.4 % in relation to inventory 1.
The relative frequencies of each species in the three inventories were statistically equal (F = 0.096, gl = 2, P = 0.91). The genus Pinus had a relative frequency of 50 % in inventory 1 that decreased 11.22 % for inventory 3, while Arbutus increased 10.55 % in the same period and Quercus decreased 0.68 %.
According to the Kruskal-Wallis test, the IVI had no significant differences between inventories 1, 2 and 3 (X2 = 0.27, gl = 2, P = 0.87). Pinus durangensis Martínez was the most representative species in the three evaluation periods with 35.98 % that decreased 3.38 % for inventory 3, followed by Q. sideroxyla with IVI of 17.8 % in the first period that increased to 18.5 % for inventory 3, and P. cooperi that increased 0.04 % in the 10-year interval (Table 5).
Table 5 Ecological parameters and importance value index (IVI) in a temperate forest under selection method for three inventories conducted over a 10-year period in the region of El Salto, Pueblo Nuevo, Durango.
Species | Abundance (trees∙ha-1) | RA (%) | Basal Area (m2∙ha-1) | RD (%) | Frequency | RF (%) | IVI (%) |
---|---|---|---|---|---|---|---|
Selection inventory 1 | |||||||
Pinus durangensis | 192.0 | 42.29 | 12.38 | 51.37 | 6 | 14.29 | 35.98 |
Quercus sideroxyla | 88.6 | 19.53 | 4.72 | 19.59 | 6 | 14.29 | 17.80 |
Pinus cooperi | 73.3 | 16.15 | 3.62 | 15.02 | 5 | 11.90 | 14.36 |
Pinus strobiformis | 34.6 | 7.64 | 1.02 | 4.23 | 4 | 9.52 | 7.13 |
Juniperus deppeana | 27.3 | 6.02 | 0.47 | 1.96 | 5 | 11.90 | 6.63 |
Pinus teocote | 6.6 | 1.47 | 0.23 | 0.95 | 4 | 9.52 | 3.98 |
Arbutus bicolor | 9.3 | 2.06 | 0.32 | 1.34 | 3 | 7.14 | 3.51 |
Quercus crassifolia | 4.6 | 1.03 | 1.08 | 4.48 | 1 | 2.38 | 2.63 |
Pinus leiophylla | 7.3 | 1.62 | 0.14 | 0.60 | 2 | 4.76 | 2.33 |
Alnus jorullensis | 6.6 | 1.47 | 0.05 | 0.22 | 2 | 4.76 | 2.10 |
Arbutus madrensis | 2.0 | 0.44 | 0.03 | 0.14 | 2 | 4.76 | 1.78 |
Quercus rugosa | 0.6 | 0.15 | 0.02 | 0.07 | 1 | 2.38 | 0.86 |
Alnus firmifolia | 0.6 | 0.15 | 0.01 | 0.02 | 1 | 2.38 | 0.85 |
Total (±SD) | 454.0 ± 55.12 | 100 | 24.1 ± 3.5 | 100 | 42 ± 4.8 | 100 | 100 ± 9.97 |
Selection inventory 2 | |||||||
Pinus durangensis | 165.3 | 38.75 | 11.39 | 48.84 | 6 | 14.63 | 34.07 |
Quercus sideroxyla | 100.0 | 23.44 | 5.32 | 22.81 | 6 | 14.63 | 20.29 |
Pinus cooperi | 58.6 | 13.75 | 2.84 | 12.17 | 5 | 12.20 | 12.71 |
Pinus strobiformis | 31.3 | 7.34 | 1.01 | 4.32 | 3 | 7.32 | 6.33 |
Juniperus deppeana | 24.0 | 5.63 | 0.49 | 2.10 | 4 | 9.76 | 5.83 |
Pinus teocote | 6.6 | 1.56 | 0.27 | 1.16 | 4 | 9.76 | 4.16 |
Arbutus bicolor | 10.0 | 2.34 | 0.37 | 1.57 | 3 | 7.32 | 3.74 |
Quercus crassifolia | 6.6 | 1.56 | 1.29 | 5.51 | 1 | 2.44 | 3.17 |
Alnus jorullensis | 6.6 | 1.56 | 0.10 | 0.41 | 2 | 4.88 | 2.28 |
Alnus firmifolia | 6.6 | 1.56 | 0.06 | 0.28 | 2 | 4.88 | 2.24 |
Arbutus madrensis | 2.6 | 0.63 | 0.04 | 0.19 | 2 | 4.88 | 1.90 |
Pinus leiophylla | 6.6 | 1.56 | 0.13 | 0.55 | 1 | 2.44 | 1.52 |
Quercus rugosa | 0.6 | 0.16 | 0.02 | 0.08 | 1 | 2.44 | 0.89 |
Prunus serotina | 0.6 | 0.16 | 0.00 | 0.01 | 1 | 2.44 | 0.87 |
Total (±SD) | 426.67 ± 47.7 | 100 | 23.33 ± 3.17 | 100 | 41 ± 4.4 | 100 | 100 ± 9.42 |
Selection inventory 3 | |||||||
Pinus durangensis | 170.6 | 36.68 | 12.51 | 48.78 | 6 | 12.24 | 32.6 |
Quercus sideroxyla | 108.0 | 23.21 | 5.18 | 20.18 | 6 | 12.24 | 18.5 |
Pinus cooperi | 54.0 | 11.60 | 3.21 | 12.52 | 5 | 10.20 | 11.4 |
Pinus strobiformis | 38.6 | 8.31 | 1.42 | 5.52 | 3 | 6.12 | 6.7 |
Juniperus deppeana | 28.0 | 6.02 | 0.59 | 2.31 | 4 | 8.16 | 5.5 |
Arbutus bicolor | 12.0 | 2.58 | 0.42 | 1.66 | 4 | 8.16 | 4.1 |
Pinus teocote | 8.0 | 1.72 | 0.37 | 1.45 | 4 | 8.16 | 3.8 |
Quercus crassifolia | 6.6 | 1.43 | 1.32 | 5.15 | 2 | 4.08 | 3.6 |
Alnus firmifolia | 16.6 | 3.58 | 0.20 | 0.79 | 3 | 6.12 | 3.5 |
Arbutus madrensis | 3.3 | 0.72 | 0.06 | 0.22 | 3 | 6.12 | 2.4 |
Arbutus tessellata | 2.6 | 0.57 | 0.02 | 0.08 | 3 | 6.12 | 2.3 |
Alnus jorullensis | 6.6 | 1.43 | 0.14 | 0.56 | 2 | 4.08 | 2.0 |
Pinus leiophylla | 8.0 | 1.72 | 0.17 | 0.66 | 1 | 2.04 | 1.5 |
Quercus rugosa | 0.6 | 0.14 | 0.02 | 0.08 | 1 | 2.04 | 0.8 |
Prunus serotina | 0.6 | 0.14 | 0.01 | 0.02 | 1 | 2.04 | 0.7 |
Arbutus arizonica | 0.6 | 0.14 | 0.00 | 0.02 | 1 | 2.04 | 0.7 |
Total (±SD) | 465.33 ± 46.98 | 100 | 25.65 ± 3.24 | 100 | 49 ± 3.5 | 100 | 100 ± 8.41 |
RA: relative abundance; RD = relative dominance; RF relative frequency. ±SD: standard deviation.
Sites with thinning treatments
Abundance in the six sites with thinning treatment showed no statistically significant changes in the three evaluation periods (X2 = 0.14, gl = 2, P = 0.93). A total of 857.33 ± 115.86 trees∙ha-1 was recorded in inventory 1, which was reduced to 833.33 ± 104.98 trees∙ha-1 for inventory 3. Thirteen species were recorded in inventory 1 and 15 species were recorded in inventories 2 and 3 by the addition of Alnus jorullensis Kunth and Quercus rugosa Née. Figure 3B shows the number of trees per diameter category in the three inventories, most of them are in the lower categories with a trend of inverted J-shaped data, characteristic of young stands.
Basal area of inventory 1 was 24.4 ± 3.01 m2∙ha-1 which decreased to 23.23 ± 2.95 m2∙ha-1 for inventory 2 and, finally increased to 26.69 ± 3.42 m2∙ha-1. According to the Kruskal-Wallis nonparametric test, these changes were not significant (X2 = 0.32, gl = 2, P = 0.85). Pinus had a relative dominance of 79.82 ± 18.94 % in inventory 1 that increased to 81.94 ± 18.99 % for inventory 3; statistically no significant changes were recorded (X2 = 0.06, gl = 2, P = 0.97). Quercus reduced its relative dominance by 1.91 % between the three evaluation periods, but without statistically significant changes (X2 = 0.37, gl = 2, P = 0.83).
Relative frequencies also showed no statistically significant changes among the three inventories (X2 = 0.16, gl = 2, P = 0.92). Pinus (X2 = 3.47, gl = 2, P = 0.18) and Quercus (X2 = 3.97, gl = 2, P = 0.14) showed no significant statistical changes during the study period; Pinus had the highest values in the three evaluation periods 51.35 ± 4.44 %, 48.72 ± 4.21 % and 47.5 ± 4.11 %, followed by Quercus with 18.92 ± 6.24 %, 20.51 ± 5.13 % and 20.0 ± 5.0 %.
According to IVI, there were no significant statistical changes between inventories 1, 2 and 3 (X2 = 0.42, gl = 2, P = 0.81); P. cooperi was the species with the highest IVI percentage in the three inventories, followed by P. durangensis and Q. sideroxyla (Table 6).
Table 6 Parameters, ecological indicators and importance value index (IVI) in a temperate forest under the thinning method in three inventories conducted over a 10-year period in the region of El Salto, Pueblo Nuevo, Durango.
Species | Abundance (trees∙ha-1) | RA (%) | BA (m2∙ha-1) | RD (%) | Frequency | RF (%) | IVI (%) |
---|---|---|---|---|---|---|---|
Thinning inventory 1 | |||||||
Pinus cooperi | 361.3 | 42.15 | 8.93 | 39.86 | 5 | 13.51 | 31.84 |
Pinus durangensis | 271.3 | 31.65 | 7.44 | 33.21 | 5 | 13.51 | 26.13 |
Quercus sideroxyla | 106.0 | 12.36 | 3.36 | 15.02 | 5 | 13.51 | 13.63 |
Juniperus deppeana | 18.0 | 2.10 | 0.39 | 1.76 | 6 | 16.22 | 6.69 |
Pinus strobiformis | 28.6 | 3.34 | 0.66 | 2.96 | 5 | 13.51 | 6.61 |
Pinus leiophylla | 22.6 | 2.64 | 0.60 | 2.67 | 2 | 5.41 | 3.57 |
Pinus teocote | 12.0 | 1.40 | 0.25 | 1.12 | 2 | 5.41 | 2.64 |
Arbutus bicolor | 1.3 | 0.16 | 0.14 | 0.64 | 2 | 5.41 | 2.07 |
Pinus arizonica | 12.0 | 1.40 | 0.24 | 1.06 | 1 | 2.70 | 1.72 |
Arbutus arizonica | 11.3 | 1.32 | 0.24 | 1.06 | 1 | 2.70 | 1.70 |
Arbutus tessellata | 11.3 | 1.32 | 0.11 | 0.47 | 1 | 2.70 | 1.50 |
Quercus obtusata | 0.6 | 0.08 | 0.02 | 0.10 | 1 | 2.70 | 0.96 |
Arbutus madrensis | 0.6 | 0.08 | 0.01 | 0.06 | 1 | 2.70 | 0.95 |
Total (±SD) | 857.3 ± 11.8 | 100 | 22.40 ± 3.01 | 100 | 37.0 ± 1.9 | 100 | 100 ± 10.15 |
Thinning inventory 2 | |||||||
Pinus cooperi | 364.6 | 43.24 | 9.53 | 40.98 | 5 | 12.82 | 32.35 |
Pinus durangensis | 256.0 | 30.36 | 7.44 | 32.00 | 5 | 12.82 | 25.06 |
Quercus sideroxyla | 96.0 | 11.38 | 3.13 | 13.47 | 5 | 12.82 | 12.56 |
Pinus strobiformis | 30.0 | 3.56 | 1.01 | 4.33 | 5 | 12.82 | 6.90 |
Juniperus deppeana | 22.0 | 2.61 | 0.49 | 2.09 | 6 | 15.38 | 6.69 |
Pinus leiophylla | 23.3 | 2.77 | 0.66 | 2.85 | 2 | 5.13 | 3.58 |
Pinus teocote | 12.6 | 1.50 | 0.30 | 1.30 | 2 | 5.13 | 2.64 |
Arbutus madrensis | 1.3 | 0.16 | 0.02 | 0.08 | 2 | 5.13 | 1.79 |
Quercus arizonica | 12.0 | 1.42 | 0.28 | 1.19 | 1 | 2.56 | 1.73 |
Arbutus tessellata | 11.3 | 1.34 | 0.12 | 0.53 | 1 | 2.56 | 1.48 |
Arbutus arizonica | 7.3 | 0.87 | 0.18 | 0.77 | 1 | 2.56 | 1.40 |
Arbutus bicolor | 4.6 | 0.55 | 0.06 | 0.25 | 1 | 2.56 | 1.12 |
Quercus obtusata | 0.6 | 0.08 | 0.02 | 0.11 | 1 | 2.56 | 0.92 |
Quercus rugosa | 0.6 | 0.08 | 0.01 | 0.02 | 1 | 2.56 | 0.89 |
Alnus jorullensis | 0.6 | 0.08 | 0.01 | 0.02 | 1 | 2.56 | 0.89 |
Total (±SD) | 843.33 ± 108.82 | 100 | 23.25 ± 2.95 | 100 | 39.0 ± 1.96 | 100 | 100.0 ± 9.83 |
Thinning inventory 3 | |||||||
Pinus cooperi | 361.3 | 43.36 | 11.49 | 43.04 | 5 | 12.50 | 32.97 |
Pinus durangensis | 241.3 | 28.96 | 8.01 | 30.00 | 5 | 12.50 | 23.82 |
Quercus sideroxyla | 94.6 | 11.36 | 3.47 | 12.99 | 5 | 12.50 | 12.28 |
Pinus strobiformis | 32.6 | 3.92 | 1.31 | 4.92 | 5 | 12.50 | 7.11 |
Juniperus deppeana | 24.6 | 2.96 | 0.58 | 2.16 | 6 | 15.00 | 6.71 |
Pinus leiophylla | 23.3 | 2.80 | 0.66 | 2.49 | 2 | 5.00 | 3.43 |
Pinus teocote | 15.3 | 1.84 | 0.40 | 1.50 | 2 | 5.00 | 2.78 |
Arbutus tessellata | 12.0 | 1.44 | 0.14 | 0.54 | 2 | 5.00 | 2.33 |
Arbutus madrensis | 1.3 | 0.16 | 0.03 | 0.10 | 2 | 5.00 | 1.75 |
Quercus arizonica | 12.0 | 1.44 | 0.31 | 1.15 | 1 | 2.50 | 1.70 |
Arbutus arizonica | 7.3 | 0.88 | 0.18 | 0.67 | 1 | 2.50 | 1.35 |
Arbutus bicolor | 5.3 | 0.64 | 0.08 | 0.30 | 1 | 2.50 | 1.15 |
Quercus obtusata | 0.6 | 0.08 | 0.03 | 0.10 | 1 | 2.50 | 0.89 |
Quercus rugosa | 0.6 | 0.08 | 0.01 | 0.02 | 1 | 2.50 | 0.87 |
Alnus jorullensis | 0.6 | 0.08 | 0.01 | 0.02 | 1 | 2.50 | 0.87 |
Total (±SD) | 833.33 ± 104.98 | 100 | 26.69 ± 3.42 | 100 | 40 ± 1.91 | 100 | 100 ± 9.32 |
RA: relative abundance; BA = basal area, RD = relative dominance; RF = relative frequency. ±SD: standard deviation.

Figure 3 Number of trees per tree measurement categories in a temperate forest with areas intervened by the selection method (A) and thinning (B), during three inventories over a period of 10 years in the region of El Salto, Pueblo Nuevo, Durango.
Individually, the sites showed no statistically significant changes (P < 0.05) in tree measurement variables during the three inventories (Table 7). Over the 10-year period, sites 1, 2, 6 and 8 increased in density (Figure 4A). The basal area of sites 6 and 12 decreased 0.38 m2∙ha-1 and 0.25 m2∙ha-1, respectively, over the same period (Figure 4B). Finally, for the stem volume, site 6 decreased 6.14 m3∙ha-1, while site 8 decreased 19.91 m3∙ha-1 (Figure 4C).
Table 7 Tree measurement variables of sites sampled in a temperate forest during three inventories (Inv) over a period of 10 years in the region of El Salto, Pueblo Nuevo, Durango.
Sitio | Density (trees∙ha-1) | Basal area (m2∙ha-1) | Stem volume (m3∙ha-1) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Inv1 | Inv2 | Inv3 | P (<0.05) | Inv1 | Inv2 | Inv3 | P (<0.05) | Inv1 | Inv2 | Inv3 | P (<0.05) | |
Selection | ||||||||||||
1 | 636 | 668 | 764 | 0.97 K-W | 21.13 | 18.36 | 22.01 | 0.92 K-W | 173.61 | 147.27 | 182.16 | 0.92 K-W |
2 | 228 | 192 | 260 | 0.60 K-W | 21.23 | 21.21 | 23.66 | 0.65 K-W | 200.29 | 212.43 | 239.87 | 0.71 K-W |
3 | 296 | 264 | 276 | 0.48 K-W | 25.22 | 24.65 | 28.05 | 0.70 K-W | 321.23 | 328.21 | 374.7 | 0.72 K-W |
4 | 764 | 660 | 656 | 0.74 F | 30.41 | 27.06 | 31.58 | 0.95 F | 323.76 | 292.02 | 356.83 | 0.88 F |
5 | 432 | 384 | 420 | 0.94 F | 22.49 | 22.16 | 24.87 | 0.85 F | 191.2 | 194.26 | 215.85 | 0.87 K-W |
6 | 368 | 392 | 416 | 0.96 K-W | 24.12 | 26.52 | 23.74 | 0.96 K-W | 244.01 | 293.31 | 237.87 | 0.98 K-W |
Thinning | ||||||||||||
7 | 1 080 | 1072 | 1068 | 0.97 K-W | 17.45 | 25.62 | 31.25 | 0.74 K-W | 95.68 | 177.58 | 250.89 | 0.74 K-W |
8 | 372 | 628 | 672 | 0.93 K-W | 20.41 | 23.08 | 25.86 | 0.76 K-W | 233.21 | 260.46 | 301.89 | 0.86 K-W |
9 | 960 | 872 | 868 | 0.67 K-W | 22.08 | 16.85 | 23.54 | 0.82 K-W | 210.49 | 119.64 | 190.58 | 0.69 K-W |
10 | 1 112 | 1116 | 976 | 0.98 K-W | 26.12 | 29.87 | 29.21 | 0.93 K-W | 264.96 | 323.98 | 321.38 | 0.93 K-W |
11 | 952 | 844 | 888 | 0.93 K-W | 17.54 | 17.02 | 19.74 | 0.80 K-W | 76.70 | 78.03 | 93.85 | 0.87 K-W |
12 | 668 | 528 | 528 | 0.97 K-W | 30.8 | 27.05 | 30.55 | 0.87 K-W | 295.16 | 273.71 | 308.37 | 0.83 K-W |
F: ANOVA; K-W: Kruskal-Wallis non-parametric test.
Discussion
Diversity
Species diversity assessed by the Shannon index between treatments for each inventory differed consistently, with higher values in the selection treatment. The application of the selection treatment directed at species of the genus Pinus, being of greater commercial value, promotes greater equity of the proportion of species within the stands; in contrast, applying a thinning treatment preserves the dominance of some species, because the cuts are directed at undesirable species. Solís-Moreno et al. (2006) recorded values of Hˊ= 0.72 and Hˊ= 1.21 in two plots with thinning and selection methods, respectively, which are lower than those reported in this study. Hernández-Salas et al. (2013) reported values of Hˊ 1 = 0.400, Hˊ 2 = 0.401 and Hˊ 3 = 0.347 in areas with regular management during three evaluation periods (1986,1996 and 2006) in temperate forests of Chihuahua. The difference between the values recorded by other authors and those obtained in this study is determined by the proportion of species recorded.
Ecological indicators
Abundance in each treatment showed no statistically significant changes in the three evaluation periods. López-Hernández et al. (2017) and Graciano et al. (2017) mention that high species abundance and low frequency are characteristic of ecosystems with heterogeneous structure, generated by irregular forest management, which would result in areas operated using SDM. Most natural forests are made up of trees of various age classes, and their distribution and size is not uniform (Gadow et al., 2007). On the other hand, a high percentage of forests are formed by strata where tree dominances of shapes, sizes and species mix are distinguished, and whose distribution and size depend, among other things, on the growth rate and shade tolerance (López-Hernández et al., 2017); this is a structural characteristic of areas operated with MMOBI, which would consequently generate a regular forest.
Basal area changes between evaluation periods were not statistically different for each treatment; however, the area managed by thinning showed a greater increase in the 10-year period. This increase is due to the opening of the canopy and the elimination of competition, giving rise to a mostly accelerated growth of the remaining trees in the lower diameter categories.
Pinus and Quercus were the most frequent for both treatments. These genera have been reported with the highest relative frequency values in studies of temperate forests in Mexico (Graciano-Ávila et al., 2020; López-Hernández et al., 2017; Monarrez-Gonzalez et al., 2020; Rendón-Pérez et al., 2021; Santiago-Ramírez et al., 2019; Silva-García et al., 2021).
P. durangensis, Q. sideroxyla and P. cooperi were the species of greatest ecological value. Several authors have reported at least one of these as the most representative for the state of Durango (Delgado-Zamora et al., 2016; Graciano-Ávila et al., 2020; Guevara-Fisher et al., 2021; Monarrez-Gonzalez et al., 2020; Silva-García et al., 2021).
Site 6, logged seven years after inventory 1, had a decrease in basal area and stem volume, but not in the number of trees, while site 9, logged one year after inventory 1, had a decrease in the number of trees and stem volume, but an increase in basal area. In a temperate forest under management in Chihuahua, Mexico, Hernández-Salas et al. (2018) evaluated the growth dynamics of 46 circular plots of 0.1 ha, established in 1986, to be logged one year after to be logged one year after planting and remeasured in 1996 and 2006, before a new silvicultural intervention. These authors mention that the abundance, basal area and volume of trees, prior to cutting (in the first inventory), are affected when they are remeasured (second and third inventory) due to logging or recruitment of individuals (regeneration); therefore, the differences between evaluations are not necessarily increases, as they sometimes decrease, so that it is not possible to determine the net yield of the tree stand. In the present study, for the 12 sites evaluated, the number of trees sometimes did not recover, but the basal area or volume of the forest stand was recovered, regardless of the year of cutting and silvicultural treatment applied; therefore, there is high productivity in the recovery of the tree stand by means of basal area or volume of the forests under harvest in the state of Durango.
Conclusions
The diversity of species in plant communities, managed by the MMOBI (Mexican Method of Irregular Forest Management) silvicultural method, is higher than SDM (Silvicultural Development Method). This difference is recurrently maintained despite the application of silvicultural treatments of selection (MMOBI) and thinning (SDM). Number of trees, basal area, frequency and volume of forest cover do not differ between evaluation periods (inventories), so the structure of the forest is not affected at the time of being intervened. Forest assessments and monitoring are important to continue analyzing the impact of forest management, whether negative through changes in tree diversity and structure or positive by conserving forest attributes. Collecting periodic information on forest dynamics will help forest managers in their decision making and to analyze the response of ecosystems when forest management is applied.