Flora 234 (2017) 77–83 Contents lists available at ScienceDirect Flora j ournal homepage: www.elsevier.com/locate/flora Moderate anthropogenic disturbance does not affect the demography of Magnolia schiedeana, an endangered species from Mexico a,b,∗ a,∗ Suria Gisela Vásquez-Morales , Lázaro Rafael Sánchez-Velásquez , a a a María del Rosario Pineda-López , Francisco Díaz-Fleischer , Norma Flores-Estévez , c Héctor Viveros-Viveros a Instituto de Biotecnología y Ecología Aplicada (Inbioteca), Universidad Veracruzana, Campus para la Cultura, las Artes y el Deporte, Zona Universitaria, CP 91090, Xalapa, Veracruz, Mexico b El Colegio de la Frontera Sur (Ecosur), Departamento de Conservación de la Biodiversidad, CP 29290, San Cristóbal de Las Casas, Chiapas, Mexico c Instituto de Investigaciones Forestales, Universidad Veracruzana, A.P. 551, Xalapa, Veracruz, Mexico a r t i c l e i n f o a b s t r a c t Article history: Among the many Magnolia species that are endangered by anthropogenic disturbance, some are known Received 22 May 2017 to have the capacity to produce new shoots. Demographic studies are an important tool to evaluate the Received in revised form 10 July 2017 impact of disturbances as well as the resilience and resistance of endangered species. Our study looked Accepted 12 July 2017 at the demographic dynamics of two Magnolia schiedeana populations, with an aim to determine the Edited by Fei-Hai Yu role played by disturbances. The questions were: 1) what demographic trends characterize this species? Available online 14 July 2017 2) What differences are there between disturbed and undisturbed populations? 3) Is M. schiedeana a disturbance-resilient species in general? 4) How important is the contribution of the resprouting trait to Keywords: ␭ in a population under anthropogenic disturbance? The demographic attributes evaluated were: elas- Endangered species ␭ Magnolia ticity, population growth rate ( ), and sensitivity to concrete disturbances (LTRE, Life Table Response ␭ Matrix models Experiment). The results indicated that the of the two populations did not differ significantly. The tran- Resilience sitions that contributed the most to ␭ and presented the largest variation were similar in both populations Resprouting under study. More than 90% of the contribution came from those individuals measuring ≤ 5 cm in diam- Tropical cloud forest eter. Surprisingly, M. schiedeana is not sensitive to moderate anthropogenic disturbance. Resprouting contributed to ␭ with less than 0.2%. © 2017 Elsevier GmbH. All rights reserved. 1. Introduction tors into account when defining conservation strategies and other courses of action (Cf. de Kroon et al., 2000; Sánchez-Velásquez Demographic studies in natural habitats are an important tool to et al., 2002; Ninot et al., 2008; Lázaro-Zermeno˜ et al., 2011). An evaluate both the extent to which endemic and endangered species extension of sensitivity analysis, the Life Table Response Experi- are impacted by disturbance, and their demographic resilience and ment (LTRE) incorporates a vital index and its variation (Mills and resistance (Caswell, 2001; Wiehle et al., 2016). The general condi- Lindberg 2002) for the analysis of the total contributions of each tion of a population, its vulnerability or resistance through different life-cycle transition and the variations among them (Ehrlén and life-cycle stages, and the extent to which all this is impacted by van Groenendael, 1998). disturbance, can be determined by demographic attributes, such The resprouting trait represents the ability of some woody as population growth rate (␭), elasticity and life table response (Li plants to generate secondary stems after the main stem or tree and Zhang, 2015). It is therefore important to take these indica- trunk is severed or broken; a common process in forests sub- jected to different types of disturbances, such as fires, storms, hurricanes, the harvesting of timber and the felling of trees and ∗ branches (Mwavu and Witkowski, 2008). Resprouting is an adap- Corresponding authors at: Instituto de Biotecnología y Ecología Aplicada tive resilient response to disturbances among various species at (Inbioteca), Universidad Veracruzana, Campus para la Cultura, las Artes y el Deporte, Zona Universitaria, CP 91090, Xalapa, Veracruz, Mexico. both early (e.g. Liquidambar styraciflua L., Alnus acuminata Kunth; E-mail addresses: sumoral [email protected] (S.G. Vásquez-Morales), Kormanik 1990; Avendano-Yᘠnez˜ et al., 2014) and late succes- [email protected] (L.R. Sánchez-Velásquez), [email protected] sional stages (e.g. Magnolia dealbata Zucc and Acer rubrum L; (M.d.R. Pineda-López), [email protected] (F. Díaz-Fleischer), nfl[email protected] Sánchez-Velásquez and Pineda-López, 2006; Sánchez-Velásquez (N. Flores-Estévez), [email protected] (H. Viveros-Viveros). http://dx.doi.org/10.1016/j.flora.2017.07.005 0367-2530/© 2017 Elsevier GmbH. All rights reserved. 78 S.G. Vásquez-Morales et al. / Flora 234 (2017) 77–83 and Pineda-López, 2010; Keyser and Loftis, 2015). Within the tran- Morales and Sánchez-Velásquez, 2011) and seeds can be dispersed sition matrix, resprouting may indicate either permanence or a by birds (Watanabe et al., 2002). The main pollinator is Cyclo- shift to smaller-size classes. Effective management, conservation cephala jalapensis Casey (Scarabaeidae: Dynastinae) (Dieringer and or restoration of tropical forests require an understanding of how Espinosa, 1994). plants respond to natural and anthropogenic disturbance events (Mwavu and Witkowski, 2008). 2.2. Study area The Magnoliaceae family has a worldwide distribution, compris- ing about 314 species (Rivers et al., 2016), 228 of which are listed In order to compare the demographic attributes of the two pop- under some protection category (IUCN, 2015). In Mexico, 30 species ulations of Magnolia schiedeana in question, two contrasting sites of the Magnoliaceae family, including Magnolia schiedeana Schltl., were selected in the state of Veracruz, Mexico, with the largest have been listed as endangered species (Semarnat, 2010; González- possible number of individuals in each of them. The site with dis- Espinosa et al., 2011; Rivers et al., 2016). Populations of Magnolia turbance (La Martinica) was crisscrossed by three paths, and it was schiedeana are sparsely distributed throughout the country, often defined basically by the presence of tree stumps and accumulated replaced by other plants or threatened by urban expansion. Mag- branches and timber pieces resulting from the illegal felling of trees nolia schiedeana is endemic to tropical cloud forest, a vegetation by machete or ax. The undisturbed site (Acatlán volcano), on the type and a threatened ecosystem (Hamilton et al., 1995) now cov- other hand, presented no paths and no evidence of these activi- ering only the central portion of the Gulf of Mexico drainage basin ties. Both sites are located in the biogeographic province known (Jiménez-Ramírez et al., 2007). as Transversal Neovolcanic Axis, at a distance of 15 kilometers Demographic studies of Magnolia species are scarce (Sánchez- from each other. The predominant type of soil in these sites is the Velásquez et al., 2016). Among the species most studied are M. andosol, and their mean annual temperature ranges between 16 dealbata (now referred to as M. vovidesii A. Vázquez, Domínguez- ◦ and 20 C. At La Martinica site, 37 stumps of M. schiedeana were Yescas & L. Carvajal) and M. schiedeana. Whereas the entire identified at the beginning of the study. This area is part of an life cycle of the former has been described (Sánchez-Velásquez Ecological Reserve adjacent to the town of Banderilla, Veracruz, and Pineda-López, 2010; Vázquez-García et al., 2013), the lat- ◦ ◦ Mexico (19 34’ 55” N; 96 56’ 55” W), with a mean annual rainfall ter has been the object of studies concerned with one stage of 1451 mm. Young trees of M. schiedeana are valued here for their of its life cycle and one of its vegetative structures (namely straight vertical trunks, and employed as racks to lay logs traded in the leaves) (Williams-Linera, 2000). There are also seed ecology the nearby markets. The Acatlán site sits high up on the slope of the studies of M. dealbata (seed pool and germination treatments) ◦ Acatlán volcano, in the municipality of Acatlán, Veracruz (19 41’ (Corral-Aguirre and Sánchez-Velásquez, 2006) and M. schiedeana ◦ 0.8” N; 96 51’ 14” W), where the mean annual rainfall is 1570 mm. (Vásquez-Morales and Sánchez-Velásquez, 2011). Aside from these Its lofty location near to the volcano’s summit keeps this population species, studies have been published on the production of polyfol- free from anthropogenic impact. licles in M. macrophylla Michx., M. schiedeana and M. praecocissima Both sites present a similar community composition that Koidz v. borealis (Doyle, 1989; Dieringer and Espinosa, 1994; Yasaka includes Clethra mexicana D. C., Fagus grandifolia var. mexicana Mar- et al., 2008), and on the roots of M. obovata Thunb. (Satomura et al., tinez, Liquidambar macrophylla L., Oreopanax xalapensis Decne and 2006). Although the Norma Oficial Mexicana (Semarnat 2010) lists Planch, Quercus xalapensis Humb and Bonpl. and Q. germana Cham Magnolia schiedeana as a threatened species, and some authors con- and Schlecht (Rzedowski, 1996; Williams-Linera, 2002). sider it a vulnerable species (Rivers et al., 2016) or an endangered species (González-Espinosa et al., 2011), the current status of its 2.3. Field data populations and their demographic attributes are unknown. In our study, we set out to identify the demographic attributes A census was carried out at both sites for four years (2010–2013) of two populations of M. schiedeana living under contrasting during the early rainy season (when fruits and seeds are produced), conditions (i.e., moderate anthropogenic disturbance, and no dis- and three annual cycles were obtained. At each population, the turbance). The attributes were: size structure, population growth diameter at breast height (dbh) was registered every year on indi- rate (␭), transition variations and the life-cycle transitions that con- viduals >1.3 m high, and all other individuals (≤1.3 m high) were tribute the most to ␭.