Highlights:
Sites where moss extraction occurs exhibit the highest moss biomass.
Ecotourism sites show the highest water storage capacity among mosses.
All sites were dominated by Thuidium delicatulum (Hedw.) Schimp. var. delicatulum.
Moss-extraction sites experience limited coverage of herbaceous and shrub vegetation.
Introduction
Bryophytes (hornworts, liverworts, and mosses) constitute the second most diverse group of plants, comprising approximately 13 000 species (Goffinet et al., 2008). Since they lack effective mechanisms for water content regulation (poikilohydry), environments suitable to their development and reproduction are those that are humid, with moderate temperatures and indirect exposure to sunlight (Vanderpoorten & Goffinet, 2009).
Bryophytes play an important role in maintaining moisture in terrestrial ecosystems, since they can store a high volume of water, about 50 % of the total intercepted rainwater (Delgadillo-Moya, 2014; Vanderpoorten & Goffinet, 2009). Mosses, especially, contribute significantly to plant biomass in several ecosystems; moreover, they are pioneer organisms, because they favor soil formation and water retention in the system.
Mosses are highly sensitive to changes in environmental conditions, which is related to their anatomical (e.g., poorly differentiated tissues and one-cell-thick phyllids) and physiological (poikilohydria) characteristics. Climate change and disturbance (e. g. deforestation, fragmentation and land use change) can affect the abundance and distribution of mosses, because increased temperature favors water loss by evapotranspiration, which decreases metabolic activity and causes tissue damage (Oishi, 2018; Siwach et al., 2021; Toro Manriquez et al., 2020).
Regarding direct uses, mosses are used for air pollution monitoring, because they absorb particles and chemical compounds from the atmosphere that they store in their tissues (Siwach et al., 2021). Additionally, these bryophytes serve as a non-timber forest resource of economic importance in Mexico, especially during the Christmas season (Acatitla Pluma et al., 2020); however, the intensive extraction and sale of mosses prevent the regeneration of their populations and cause environmental deterioration of the soil and forest, which could represent a risk for the survival of these species (Anastacio Martínez et al., 2017; Hernández-Rodríguez & Delgadillo-Moya, 2021).
Delgadillo-Moya (2014) mentions that information on floristic diversity, ecological importance and potential uses of mosses in Mexico is still scarce. In the particular case of the state of Hidalgo, there have been some studies focused on the richness and distribution of this group of plants, but most of the territory has not been explored (Delgadillo et al., 2014). The present research had the following objectives: 1) to analyze whether there is variation in the biomass and water storage capacity of moss species in sites for conservation, ecotourism and extraction in the oyamel fir forest of Parque Nacional El Chico, Hidalgo, Mexico, and 2) to estimate whether the coverage of the herbaceous and shrub stratum differs between sites according to the conditions of use. The aforementioned to provide information on the effect of moss extraction in this oyamel fir forest.
Materials and Methods
Study area
The Parque Nacional El Chico (PNC) is located in the Sierra de Pachuca, within the Transmexican Volcanic Belt. The predominant climate in the area is C(m)(w)b(i’)gw’’; that is, temperate subhumid with summer rainfall, mean annual temperature between 12 and 18 °C and total annual precipitation of 1 479.5 mm (Comisión Nacional de Áreas Naturales Protegidas [CONANP], 2005; Razo-Zárate et al., 2013). The dominant vegetation in the PNC consists of temperate sub-humid forests of Abies (62.9 %), %), Quercus-Abies (10.55 %), Juniperus (4.67 %), Quercus (3.97 %), Abies-Quercus (3.93 %), Quercus-Pinus (2.25 %), Pinus (1.87 %), Cupressus (1.16 %) and Pinus-Quercus (0.87 %); in addition, there is secondary grassland-scrub (2.18 %) and, in the rest of the area, aquatic, ruderal and arvense, rupicolous and xerophytic vegetation. In general, these vegetation types develop among numerous rocky formations, small valleys, lagoons and rivers (CONANP, 2005).
Moss sampling sites and units
Sampling sites in the oyamel fir forest of the PNC, dominated by Abies religiosa (Kunth) Cham. & Schltdl., were chosen based on the following criteria: 1) three sites without moss extraction, located in the core zone (CZ), 2) three sites without moss extraction, but with ecotourism activities (adjacent to the CZ) and 3) four sites where moss extraction is allowed (in the periphery of the PNC). The sampling sites are distributed in an altitudinal range between 2 780 and 2 900 m (Figure 1).

Figure 1 Location of the sampling sites, within (core zone) and on the periphery (ecotourism and moss extraction zone) of Parque Nacional El Chico, Hidalgo, Mexico.
At each sampling site, two 10 m x 10 m plots were established randomly, separated by a distance of 10 to 15 m from each other, according to the BRYOLAT methodology (Gabriel et al., 2014). Each plot was divided into 25 squares (2 m x 2 m), to subsequently select three of them at random. Each square was divided into micro squares of 5 cm x 5 cm, to carry out the sampling in three of them randomly selected. Therefore, sampling was performed in 18 microplots at each site: one site, two plots, three squares per plot, three microplots per square, i. e. 1 × 2 × 3 × 3 = 18.
Estimation of biomass and water storage capacity
Biomass and water storage capacity (WSC) of mosses were estimated in the following order: (1) separation of samples per site, (2) determination of the species present in each sample, (3) estimation of dry weight or biomass (DB), for which samples were placed on newspaper and allowed to dry for one week at room temperature, and (4) estimation of saturated or wet biomass or weight (WB), for which samples were hydrated for 30 minutes and placed in a mesh for one hour in order to preserve their integrity and remove excess water by runoff (Oishi, 2018). Weights were determined using a triple beam balance or an analytical balance, according to the amount of biomass. The WSC of the species/samples was determined using the formula described by Oishi (2018): WSC (g∙100 cm-2) = WB - DB.
Coverage of the herbaceous and shrub strata
In each locality, two randomly selected plots measuring 10 m x 10 m were established to determine the percentage of coverage for the herbaceous and shrub strata, following the scale proposed by Braun-Blanquet (Mueller-Dombois & Ellenberg, 1974), modified by Mejía Canales et al. (2018). In this scale, 5 = 75 to 100 %, 4 = 50 to 74.9 %, 3 = 25 to 49.9 %, 2 = 10 to 24.9 %, and 1 = less than 9.9 %. For this purpose, a visual estimation was made of the approximate percentage of the total ground area covered by the herbaceous or shrub stratum, without taking into account the overlap between individuals (Fehmi, 2010) or the taxonomic identity of species in both strata. The coverage percentages of the two plots in each locality were averaged to obtain a single value on the Braun-Blanquet scale.
Tree canopy cover
Tree canopy cover was estimated using a convex spherical densiometer. For this purpose, five measurements were made in each sampling plot (two per site), in each corner and in the central part; in each position the canopy cover was estimated considering the four cardinal points, as indicated in the manual of use of the densiometer (Lemmon, 1956). From these 10 measurements (five for each plot), the average canopy coverage per sampling site was calculated. The results were considered an indirect measure of the amount of light that moss species receive in the forest (Baudry et al., 2014).
Identifying species
Moss specimens were identified to family and genus level using the taxonomic keys of Gradstein et al. (2001) and to species level using the keys of Sharp et al. (1994). The nomenclature of species and taxonomic authors was updated based on information from the WFO project website (2023).
Data analysis
The values of dry biomass, wet biomass, and water storage capacity per sampling site showed no normal distribution. Therefore, the data obtained for each sampling site were compared using the non-parametric Mann-Whitney test. This test compares two independent samples (pairs of sampling sites) when the data are not normally distributed, generating a test statistic U and a P-value, which are used to determine whether the two groups (pairs of sampling sites) are significantly different. The analysis was conducted using the PAST software version 4.03 (Hammer et al., 2001), which automatically estimates a Bonferroni adjustment or correction of the P-value based on the number of comparisons made between sites independently. This is done to avoid errors in the interpretation of the results (Matamoros & Ceballos, 2017).
Results
Moss species with the highest biomass in the oyamel fir forest
We identified five species of mosses with structural importance in the 10 sampling sites, but Thuidium delicatulum (Hedw.) Schimp. var. delicatulum had the highest biomass values. Two other varieties were determined in this species: Thuidium delicatulum var. peruvianum and T. delicatulum var. radicans, but they showed low biomass values. The other most representative moss species in terms of biomass value were Bryum argenteum Hedw., Ceratodon purpureus (Hedw.) Brid., Cyrto-hypnum mexicanum (Mitt.) W. R. Buck & H. A. Crum and Helicodontium capillare (Hedw.) A. Jaeger (Table 1). The general characteristics of the identified species and varieties with data on their habitat (vegetation type), altitude, climate and geographic distribution are described in Annex 1.
Table 1 Record of moss species (1 = present, 0 = absent) according to sampling site: Core zone (A = Cedros, B = Los Shishis, C = Los Conejos), tourist zone (D = Camino hacia Conejos, E = Peña de la Orozca, F = Orozca) and moss extraction zone (G = Esquillero, H = Esquillero, I = Cruz Blanca, J = Viga Tirada) in an Abies religiosa forest at Parque Nacional El Chico, Hidalgo.
Species | Sampling sites | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
A | B | C | D | E | F | G | H | I | J | |
Bryum argenteum Hedw. | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 |
Ceratodon purpureus (Hedw.) Brid. | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Cyrto-hypnum mexicanum (Mitt.) W. R. Buck & H. A. Crum | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 |
Helicodontium capillare (Hedw.) A. Jaeger | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Thuidium delicatulum (Hedw.) Schimp. var. delicatulum | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
T. delicatulum var. peruvianum (Mitt.) H. A. Crum | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 0 |
T. delicatulum var. radicans (Kindb.) H. A. Crum, Steere & L. E. Anderson | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
Water storage capacity, wet biomass and dry biomass
Table 2 indicates that the species T. delicatulum var. delicatulum predominated widely over the others due to its presence and structural values: dry biomass, wet biomass, and WSC (water storage capacity). Figure 2 shows the results of the Mann-Whitney test, which indicates that dry biomass, wet biomass, and WSC of the mosses vary significantly (P < 0.05) among most of the analyzed sites. The core zone sites (A, B, and C) were similar to each other in the three analyzed variables but had lower values of biomass and WSC than most of the sampling sites in the ecotourism zones (E and F) and moss extraction zones (I and J). Regarding the ecotourism zone sites (D, E, and F), only site D differed from the others in the three analyzed variables; however, they did show statistically significant differences (P < 0.05) compared to most of the core zone sites and moss extraction zone sites. On the other hand, the moss extraction sites (G, H, I, and J) differed from each other in the three analyzed variables; sites G and H with low values of dry biomass, wet biomass, and WSC differed significantly from sites I and J. When comparing the extraction zone sites with the core zone and ecotourism zone sites, it was observed that two of them (I and J) had significantly higher values in the three analyzed variables (Figure 2).

Figure 2 The Mann-Whitney test was conducted for I) water storage capacity (yellow color), II) wet biomass (green color), and III) dry biomass (blue color) of mosses identified in a forest of Abies religiosa. Whiskers indicate the maximum and minimum values of the variables at each site, and the vertical line within the boxes represents the median, indicating where 50 % of the data lies. The letters at the bottom of the figure (x-axis) represent the names of the sites: A: Cedros, B: Los Shishis. C: Los Conejos, D: Camino hacia Conejos, E: Peña Orozca, F: La Orozca, G: Esquillero 7, H: Esquillero 8, I: Cruz Blanca and J: Viga Tirada. Each site was compared with each of the other nine sites; the letters at the top of each box correspond to the sites that exhibited statistically significant differences (P < 0.05) when compared with the site positioned on the x-axis according to the Bonferroni test. For example, in the first graph, sites A, B, C, and D had no significant differences between them, so no letters are included at the top of the corresponding boxes. In contrast, sites E and F (x-axis) had significant differences compared to sites C and D.
Table 2 Record of dry biomass (DB), wet biomass (WB), wet biomass to dry biomass ratio (WB/DB) and water storage capacity (WSC) per moss species in an Abies religiosa forest at Parque Nacional El Chico, Hidalgo.
Taxon | DB (g∙cm-2) | WB (g∙cm-2) | WB/DB (%) | WSC (g∙cm-2) |
---|---|---|---|---|
Bryum argenteum | 22.35 | 126.44 | 5.7 | 1.041 |
Ceratodon purpureus | 24.7 | 124.08 | 5 | 0.994 |
Cyrto-hypnum mexicanum | 35.2 | 185.61 | 5.3 | 1.503 |
Helicodontium capillare | 5.6 | 34.33 | 6.1 | 0.287 |
Thuidium delicatulum var. delicatulum | 585.12 | 4 455.51 | 7.6 | 36.445 |
T. delicatulum var. peruvianum | 35.46 | 170.31 | 4.8 | 1.349 |
T. delicatulum var. radicans | 3.6 | 23.6 | 6.6 | 0.2 |
On the other hand, Table 3 indicates that the percentage of coverage of herbaceous and shrubby species, estimated using the Braun-Blanquet scale, differed among the sampling sites based on the type of disturbance or management (conservation, ecotourism, and moss extraction). The core zone and ecotourism sites at PNC exhibited well-developed herbaceous and shrubby layers (50 % or more coverage), but the shrubby layer was less prominent in the core zone (25 % or more coverage). In contrast, in the moss extraction zone sites, the coverage of both herbaceous and shrubby layers was low (25 % or less), leading to the forest floor being covered by plants with a creeping habit; specifically, mosses. It is important to mention that in all sampling sites, the dominant tree species was A. religiosa, and the canopy coverage was relatively uniform (between 92.5 % and 98 %).
Regarding the herbaceous and shrub strata, in all sites, the most common species and with the highest contribution to the percentage of cover were: Acaena elongata L., Ageratina glabrata (Kunth) R. M. King & H. Rob., Alchemilla procumbens (Rose) Rydb., Baccharis conferta Kunth, Ribes ciliatum Humb. & Bonpl. ex Roem. & Schult., Roldana angulifolia (DC.) H. Rob. & Brettell, Salvia elegans Vahl, Sigesbeckia jorullensis Kunth and Symphoricarpus microphyllus Kunth. It should be emphasized that the percent cover of herbs and shrubs was estimated at the stratum level, not at the species level.
Table 3 Cover of the herbaceous, shrub, and canopy strata; water storage capacity (WSC), and biomass (WSC/dry biomass) of mosses, at each sampling site in a forest of Abies religiosa at Parque Nacional El Chico, Hidalgo. The coverage of shrub and herbaceous strata was qualitatively determined through visual observation, considering the space occupied by each stratum.
Site | Strata cover (%) | Elevation (m) | WSC (g∙cm-2) | Biomass (g∙cm-2) | ||
---|---|---|---|---|---|---|
Herbaceous | Shrub | Canopy | ||||
A. Cedros | 50-74.9 | 25-49.9 | 97 | 2 871 | 0.171 | 0.053 |
B. Los Shishis | 50-74.9 | 50-74.9 | 93 | 2 919 | 0.161 | 0.051 |
C. Los Conejos | 75-100 | 50-74.9 | 93 | 2 822 | 0.115 | 0.599 |
D. Camino Conejos | 50-74.9 | 25-49.9 | 96 | 2 822 | 0.096 | 0.049 |
E. La Peña Orozca | 50-74.9 | 25-49.9 | 96 | 2 850 | 0.245 | 0.044 |
F. La Orozca | 50-74.9 | 25-49.9 | 94 | 2 851 | 0.254 | 0.042 |
G. Esquillero 1 | 10-24.9 | <9.9 | 93 | 2 957 | 0.087 | 0.140 |
H. Esquillero 2 | <9.9 | <9.9 | 98 | 2 957 | 0.064 | 0.073 |
I. Cruz Blanca | <9.9 | <9.9 | 95 | 2 891 | 0.233 | 0.054 |
J. Viga Tirada | <9.9 | <9.9 | 94 | 2 901 | 0.245 | 0.042 |
Discussion
In all examined sites, T. delicatulum var. delicatulum stood out as the most significant moss species in terms of biomass and WSC values. The widespread presence and structural importance, reflected in higher biomass, across all sites suggest that this taxon possesses a notable capacity for adaptation and phenotypic plasticity compared to other coexisting moss species within the altitude gradient of 2 822 to 2 957 m and the analyzed vegetation types (Anastacio Martínez et al., 2021). Consistent with these findings, Cárdenas (1999) notes that this moss variety thrives in mature forests or at different stages of succession with varying degrees of disturbance, where trees of the genera Abies, Juniperus, and Quercus dominate, mainly; that is, they grow in heterogeneous microenvironmental conditions either under the shade of the canopy or with exposure to radiation (soil, trunks, roots or branches), in dry or humid places, in an altitudinal interval that ranges between 2 830 and 2 900 m. In any case, all identified mosses share characteristics: wide geographic distribution on the planet, presence and structural importance in various types of vegetation and at different stages of succession, which indicates that they can survive in a wide range of environmental conditions (Hernández-Rodríguez et al., 2021; Sharp et al., 1994).
The results clearly show the impact of tourism and extraction activities on the most structurally important moss species in the oyamel fir forest of Parque Nacional El Chico, Hidalgo, since there are significant differences in the wet biomass, dry biomass and WSC of mosses between sampling sites. These differences are related to the type of forest management or use (extraction, tourism or conservation); however, it was also found that, in some sites, variables were independent of the type of forest use or management, so it is likely that other factors at local (exposure, slope, soil type, light input and floristic composition) and regional (temperature and humidity) scales influence the structure of the moss stratum (Fojcik et al., 2019; Stefanska-Krzaczek et al., 2022; Toro Manriquez et al., 2020). In this sense, several authors indicate that the presence and abundance of moss species is related to other plant groups and to multiple environmental factors such as solar radiation, canopy cover, humidity, and soil properties (Oishi, 2018; Siwach et al., 2021; Toro Manriquez et al., 2020).
In the present study, biomass and WSC values of mosses and percent cover of herbaceous and shrub strata in the oyamel fir forest of Parque Nacional El Chico differed markedly between managed/used (moss extraction/ecotourism) and unmanaged (core zone) sites. This is consistent with results in other studies indicating that bryophyte richness, distribution, and biomass are closely associated with the composition and structural values of coexisting vascular plant species (Fojcik et al., 2019; Hernández-Rodríguez et al., 2021; Stefanska-Krzaczek et al., 2022; Toro Manriquez et al., 2020).
The cover of the herbaceous and shrub stratum is negatively related to the total cover or biomass of bryophytes, due to competition for water, light and growth substrate (Fojcik et al., 2019). In the study area, the understory structure was evidently modified in two of the sites where moss is extracted, there the cover of herbaceous and shrub strata was drastically reduced and the biomass and WSC of mosses increased. However, at two remaining sites, biomass and WSC were not significantly different from the values estimated at the core zone sites. In these cases, it is possible that the upper tree layer dominated by A. religiosa in all sampling sites, by remaining intact, is generating a buffering effect by providing partial protection against desiccation and the passage of enough light for moss growth and reproduction (Hernández-Rodríguez et al., 2021; Toro Manriquez et al., 2020). In the synecological analysis conducted by Hernández-Álvarez et al. (2021), the species composition of the herbaceous and shrub stratum of the oyamel fir forest showed no difference between sites; the species identified were characteristic of this type of vegetation, so the differences between sites were at the structural level (cover).
In general, the results indicate that there are evident changes in understory structure (herbs and shrubs) and in biomass and WSC of mosses, among sites with different use and management. Therefore, a detailed study of forest structure and quantification of local environmental factors (light, temperature, humidity, exposure and slope) under different management conditions (Gabriel et al., 2014; Hernández-Rodríguez et al., 2021; Herrera-Paniagua et al., 2018; Zepeda-Gómez et al., 2014) and over time, through a monitoring program, are necessary. In this way, it would be possible to define more precisely what the near future of the PNC’s oyamel fir forest, ecotourism activities, and moss extraction will be if they continue as they have been doing so far.
The extraction of mosses from forests in Mexico should be a controlled activity. Most species of this group of plants are intensively extracted and the most affected ones such as T. delicatulum (Acatitla Pluma et al., 2020; Anastacio Martínez et al., 2017) are not yet included in any risk category within the Mexican Official Standard NOM-059-2010 (Secretaría del Medio Ambiente y Recursos Naturales [SEMARNAT], 2010) because there is a lack of quantitative biological information on the current status of their populations.
Conclusions
Moss species in the oyamel fir forest of Parque Nacional El Chico have high water store capacity (WSC) and wide coverage (biomass) at all sampling sites. Dry biomass, wet biomass and WSC values differed among sites, in general, depending on forest use and management (conservation, ecotourism or extraction). At moss extraction sites, herbaceous and shrub plant species cover was low compared to ecotourism and conservation sites, which probably favored the increase in moss biomass. The canopy cover could be maintaining the radiation and humidity conditions necessary for moss growth in some of the sites with use and management. Therefore, it is important to implement a monitoring program and moss management and conservation measures to maintain the basic ecological structure of the oyamel fir forest.