Relationship between the distribution of vegetation and the environment in the coastal embryo dunes of Jalisco, México

Abstract

Background: The poorly developed soils of the embryo dunes imply little capacity for plant support, however, the adaptation mechanisms of plants respond sensitively to environmental variations, even when these variations are small, which results in a set of specialized habitats and flora that are rarely shared with other terrestrial ecosystems. The coastal dunes of the Mexican Pacific remain vaguely studied, this is why this research explored the relationship between environmental properties and the presence of plant species in the embryo dunes of the coast of Jalisco, Mexico.

Methods: Twenty-nine sites were sampled, one or two sites per embryo dune, with a random stratified design. Geomorphological and vegetation data were collected at site. Laboratory determinations included soil color, particle size, organic matter, pH, electrical conductivity, magnetite content, and moisture retention. Statistical analysis included correlation analysis to identify relationships between environmental variables; principal component analysis (PCA) and cluster analysis to group dune sites by environmental properties; canonical correspondence analysis (CCA) to determine a possible significant relationship between the presence of plant species and environmental variables; cluster analysis to group dune sites by presence/absence of plant species and correlate both clusters to validate the relationship between them, the salient aspects of this relationship were described and the spatial distribution of the groups was mapped.

Results: Eleven plant species were identified, six of them exclusive to the embryo dunes and the rest ubiquitous. The incipient development of these soils is reflected in a low content of organic matter, silt, clay, and moisture retention, with scattered data on granulometry, electrical conductivity, organic matter, and magnetite. Some significant correlations were found between some environmental properties, and the CCA showed a significant relationship between the presence of plant species and environmental variables (p-value of the Monte Carlo test = 0.026). The cluster analysis of dune sites according to environmental variables and the cluster analysis by presence/absence of plant species produces the formation of five groups of sites with significant environmental differences and five groups of sites with significant floristic differences. A significant connection (r = 0.471, p = 0.01) between the two clustering schemes also evidences the meaningful relationship between the presence of plant species and the environmental characteristics of the embryo dunes of Jalisco, Mexico. Differences in habitat preferences were observed among plant species exclusive to the embryo dunes; thus, Abronia maritima, Uniola pittieri, and Pectis arenaria showed a preference for embryo dunes with poor edaphic conditions, in contrast to Okenia hypogaea, Canavalia rosea, and Scaevola plumieri, which were mostly found in embryo dunes with higher fertility.

Keywords: Dunes vegetation; Magnetite content; Mexican Pacific; Mobile coastal dunes; Soil formation; Soil-plant relationships.

Figure 1. Location of sample sites.

Map data © 2021 Esri, Garmin, GEBCO, NOAA NGDC, INEGI.

Figure 2. Exclusive plant species of embryo dunes in the study area.

(A) Abronia maritima, (B) Canavalia rosea, (C) Okenia hypogaea, (D) Pectis arenaria, (E) Scaevola plumieri, (F) Uniola pittieri. Photo credit: Miguel Ángel Macías-Rodríguez.

Figure 3. Scatter plot constructed with the PCA component scores.

The numbers framed within the plot correspond to the site number.

Figure 4. Ordination diagram that illustrates the relationships between environmental properties (lines) and plant species (dots).

Species: Abr: Abronia maritima, Aca: Acalypha monostachya, Can: Canavalia rosea, Dis: Distichlis spicata, Ipo: Ipomoea pes-capreae, Jou: Jouvea pilosa, Oke: Okenia hypogaea, Pec: Pectis arenaria, Pro: Prosopis juliflora, Sca: Scaevola plumieri, Uni: Uniola pittieri. Environment variables: alt: Altitude of the topoform, cob: Vegetation coverage, dis: Distance to the sea, lat: Latitudinal gradient, ori: Orientation of the topoform, af: Fine sand, amg: Very coarse sand, ce: Electrical conductivity, hum: Moisture retention, mg: Magnetite, mo: Organic matter, ph: pH.

Figure 5. Geographic distribution of groups of sites according to environmental variables (GVA).

Map data © 2021 Esri, Garmin, GEBCO, NOAA NGDC, INEGI.

Figure 6. Geographic distribution of groups of sites according to the presence of plant species (GEF).

Map data © 2021 Esri, Garmin, GEBCO, NOAA NGDC, INEGI.