Colonization in Mediterranean old‐fields: the role of dispersal and plant–plant interactions

Abstract

Questions How do the dominant species in a Mediterranean community (Juniperus sabina, Juniperus communis and Pinus sylvestris) colonize abandoned fields? At what rates? Does dispersal limitation shape species colonization patterns? Does J. sabina act as nurse plant for the other two species? If so, in which stages of development: seedlings and saplings or older individuals? Location Abandoned crop fields in the Alto Tajo Natural Park, central‐eastern Spain. Methods We mapped all individuals of the three species in three 4–14‐ha plots, and aged them using dendrochronology. Spatial patterns in 2000, 1980 and 1960 were reconstructed according to estimated ages in 2014. We used a battery of spatial point‐pattern analyses to evaluate dispersal in junipers, dispersal in pines, and the role of J. sabina as nurse plant for the other two species. Results Both junipers colonized earlier than pines, probably due to their more effective endozoochorous dispersal. Late‐coming pines, once established, expanded faster due to their higher seed productivity. Recent recruits of J. communis and P. sylvestris showed a random relationship with J. sabina canopies, whereas spatial patterns of older individuals in relation to J. sabina canopies ranged from attraction (plot 2 and marginally plot 1), suggesting facilitation, to repulsion in plot 3. These differences in spatial patterns between plots could be related to a shift in dominant herbivores, from sheep (plots 1 and 2) to red deer (plot 3). Conclusions Dispersal and plant–plant interactions drove colonization in Mediterranean old fields. The inclusion of a temporal perspective in the analysis of spatial patterns allowed the detection of shifting interactions between J. sabina and the other two species, depending on their life stage. This is a clear advance compared with the usual static analyses, as it provides additional clues to interpret the mechanisms and processes underlying their origin.

Past the climate optimum: Recruitment is declining at the world's highest juniper shrublines on the Tibetan Plateau

“…Juniper shrubs form well-defined annual growth rings that have proven to be reliable for dendrochronological dating (Liang et al 2012). Thus, we used standard dendroecological techniques to estimate the ages of all the measured shrubs, as has often been done in treeline and shrubline studies (Camarero and Guti errez 2004, Liang et al 2011, Garc ıa-Cervig on et al 2017, Sigdel et al 2018. Additionally, a total of 277 juniper shrubs with different basal stem diameters located just outside the shrubline plots were selected to represent different age classes.…”

Past, present, and future geographic range of the relict Mediterranean and Macaronesian Juniperus phoenicea complex

“…The high demands of J. phoenicea for access to light, its pioneering character (Asensi et al., 2007; Díez‐Garretas et al., 1996; Franco, 1986; García et al., 2014; Garcia‐Cervigon et al., 2017; Lloret & García, 2016; Lloret & Granzow‐de la Cerda, 2013; Minissale & Sciandrello, 2013), and ornitochorology (Arista et al., 1997; Garcia‐Cervigon et al., 2017) facilitate the rapid colonization of new terrains (García et al., 2014). On the other hand, the relatively long‐life span of the species, especially specimens growing in harsh conditions (Camarero & Ortega‐Martínez, 2019; Mandin, 2005; Mathaux et al., 2016), may have allowed it to persist in some localities even without optimal conditions.…”

“…Like most junipers, they are light demanding, moderately thermophilic and relatively drought-resistant (Asensi et al, 2007;Browicz & Zieliński, 1982;Charco, 1999;Lloret & García, 2016;Otto et al, 2012;Quézel & Médail, 2003;Rubio-Casal et al, 2010;Zohary, 1973). These three species occasionally manifest a pioneer nature (García et al, 2014;Garcia-Cervigon et al, 2017). The taxonomic differences between J. phoenicea s.s., J. turbinata, and J. canariensis may be the result of their divergent evolutionary story from the moment they split from their ancestor in the Oligocene (Mao et al, 2010).…”

“…Like most junipers, they are light demanding, moderately thermophilic and relatively drought‐resistant (Asensi et al., 2007; Browicz & Zieliński, 1982; Charco, 1999; Lloret & García, 2016; Otto et al., 2012; Quézel & Médail, 2003; Rubio‐Casal et al., 2010; Zohary, 1973). These three species occasionally manifest a pioneer nature (García et al., 2014; Garcia‐Cervigon et al., 2017).…”

A comparative analysis between SNPs and SSRs to investigate genetic variation in a juniper species (Juniperus phoenicea ssp. turbinata)

“…Several Juniperus species have increased their population sizes and geographical distribution during the past decades driven by land-use changes, namely rural abandonment, and increasingly arid conditions (Van Auken 2008). For example, fragmented populations of Juniperus phoenicea have rapidly expanded across a matrix of surrounding Mediterranean shrublands (García et al 2014); former remnant patches of J. thurifera now have developed into extensive savanna-like forests in former agricultural landscapes of the central Iberian Peninsula (Escribano-Ávila et al 2012;García-Cervigon et al 2016), and J. monosperma has become the dominant species of the piñon-juniper ecotone in northern New Mexico following an extreme drought event in the 1950s (Allen and Breshears 1998). At a very different temporal scale, phylogeographical studies have retraced the postglacial expansions of juniper taxa that represent today the major tree species of many central Asian highlands and mountain ranges (Opgenoorth et al 2010).…”