Plant Ecol (2011) 212:1159–1177 DOI 10.1007/s11258-011-9895-1 Spatial distribution and floristic composition of trees and lianas in different forest types of an Amazonian rainforest Manuel J. Macı´a Received: 11 March 2010 / Accepted: 12 January 2011 / Published online: 26 January 2011 Ó Springer Science+Business Media B.V. 2011 Abstract A quantitative inventory of trees and Keywords Beta diversity Á Floodplain Á Floristic lianas was conducted (1) to compare floristic com- patterns Á Swamp Á Tierra firme position, diversity and stem density variation between three different forest types (tierra firme, floodplain and swamp), and (2) to analyse the relationships Introduction between floristic similarity and forest structure in two regions *60 km apart in Yasunı´ National Park, The flora of Ecuador is among the best-known in the Amazonian Ecuador. A total of 1,087 species with a Neotropics. However, in the Amazonian region there diameter at breast height C 2.5 cm were recorded in still remain important gaps of plant diversity knowl- 25 0.1-ha plots. Tierra firme was the habitat with the edge and comparisons of floristic diversity and highest number of species and stem density for trees species composition between habitats and regions and lianas, followed by floodplain and swamp in both (through quantitative inventories) are very scarce regions. Two hypotheses that have been indepen- (e.g. Balslev et al. 1987; Burnham 2004). In the dently proposed to describe plant distribution in lowlands of Amazonian Ecuador (0–500 m eleva- tropical rain forests, together explain species spatial tion), 3,996 plant species have been found (26.1% of distribution in this study. The fact that the 30 most all Ecuadorean vascular plants), of which 54.4% are important species per forest type (totalling 119 woody plants including trees, treelets, lianas and species) accounted for 48.2% of total individuals hemiepiphytes (Jørgensen and Leo´n-Ya´nez 1999). supports the oligarchy hypothesis. Likewise, 28 out Such a relatively well-known and diverse region of these 119 species are reported as restricted to a offers a good opportunity to understand spatial single forest type, which supports the environmental- distribution and similarity of species between differ- determinism hypothesis. In general, both canopy and ent habitats at regional scales. understorey trees and lianas showed rather similar This is the case of Yasunı´ National Park and the floristic patterns across different forest types and Huaorani Ethnic Reserve, referred to hereafter as regions. Yasunı´, which represent one of the best-known areas in plant diversity in northwestern Amazonia. Several quantitative floristic inventories of woody plants have M. J. Macı´a(&) been carried out in the last 23 years, indicating that ´ Departamento de Biologı´a, Area de Bota´nica, Universidad the alpha diversity of woody plants in Yasunı´ is Auto´noma de Madrid, Calle Darwin 2, 28049 Madrid, Spain among the highest in the tropics (Romoleroux et al. e-mail: [email protected] 1997; Pitman et al. 2002; Bass et al. 2010). For 123 1160 Plant Ecol (2011) 212:1159–1177 instance, there were 1,104 tree species and morpho- physiographic forest unit, mainly well-drained upland species in 152,353 individuals of free-standing tierra firme forests and to a lesser degree on well- woody stems with a diameter at breast height drained floodplain forests, but rarely on poorly (dbh) C 1 cm, in a tierra firme 25-ha permanent plot drained and permanently flooded forests or swamps. (Valencia et al. 2004). Another study of large Species counts of vascular plants exhibited lower trees C 10 cm dbh in 15 tierra firme 1-ha plots found alpha diversity and density in swamp forests than in a total of 1,017 species-level taxa in 9,809 individuals well-drained forests (Lieberman et al. 1985; Camp- (Pitman et al. 2001), while other papers also recorded bell et al. 1992). Tierra firme forests tend to be more high species counts for large trees in 1-ha plot species-rich and with higher stem density than inventories (Balslev et al. 1987;Cero´n 1997). For floodplain habitats (Campbell et al. 1986; Balslev lianas, there were 311 species among 4,348 climbing et al. 1987; Duivenvoorden 1994; Duque et al. 2002; stems C 1 cm dbh in 0.2-ha subsamples from 12 1-ha Burnham 2004), but the extent to which the species plots established in both tierra firme and floodplain composition varies with the geographic distance habitats (Burnham 2002, 2004). In another study, between different and similar habitats defined by there were 138 species and 606 individuals of inundation history is poorly known. lianas C 1 cm dbh in two 0.2-ha tierra firme forest This article includes a quantitative inventory of all plots (Nabe-Nielsen 2001). Finally, there have also woody plant habits (particularly trees and lianas) been quantitative inventories of particular families within the same plots. New analyses of Romero- such as Arecaceae (Svenning 1999; Vormisto et al. Saltos et al.’s (2001) data are performed to further 2004; Montu´far and Pintaud 2006), pteridophytes and explain the extent of diversity and density variation in Melastomataceae (Tuomisto et al. 2002, 2003a). two regions *60 km apart (Dicaro and Guiyero; Quantitative floristic inventories including all Fig. 1) and three different forest types (tierra firme, habits of woody plants are scarce in most tropical floodplain and swamp) in Yasunı´ by six life-form vegetation types, although patchily distributed in subdivisions. More specifically, I ask (i) whether tropical rain forests (e.g. Gentry and Dodson 1987; floristic similarity is higher between different forest Duivenvoorden 1994; Duque et al. 2002; Macı´a types of the same region than between similar forest 2008). Most of these studies have focused on a types of different regions, for different life-forms and Fig. 1 Location of the 76 W N study area and 25 0.1-ha Colombia Río Tiputini plots of tierra firme (cross), • Guiyero 04km floodplain (filled square) 0 and swamp (filled triangle) Amazonian Ecuador forest types inventoried Río Napo • 0 40' S around two indigenous Yasuní Research communities (Dicaro and Station Río Tiputini Yasuní Guiyero) in Yasunı´ Huaorani Reserve National National Park and the Park Tierra firme plot Huaorani Ethnic Reserve, Oil company road Floodplain plot Amazonian Ecuador. The Swamp plot climatic diagram shows temperature and Peru 0 50' S precipitation average Río Yasuní values ± standard deviation Climatic diagram 26 from the Yasunı´ Research 25 24 Ecuador Dicaro Station for the period 400 • 1995–2007 350 300 South America 250 (°C) Temperature 200 150 Río Dicaro 100 Precipitation (mm) 50 1 00' S Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 76 20' W 76 10' W 123 Plant Ecol (2011) 212:1159–1177 1161 size classes, and (ii) if the species diversity, stem selection of sites was based on Landsat TM satellite density and forest structure, through the relative imagery and according to accessibility. Each plot was distribution in diameter classes of trees and lianas, placed in well-developed forest with no signs of shows significant differences between these two recent anthropogenic disturbance, excluding big can- regions. opy gaps and avoiding heterogeneity in forest phys- iognomy or soils, and therefore installed in a single broad forest type (tierra firme, floodplain or swamp). Methods Plots within the same region were at least 500 m apart. Study area Trees and lianas with stems rooted within a plot and with a dbh (diameter measured at 1.3 m above Fieldwork was carried out in Yasunı´, the largest ground) equal to or greater than 2.5 cm were protected area in Amazonian Ecuador with measured, inventoried and identified to species or to *1.6 million ha. Yasunı´ is located at the foot of a field-temporary name allocated to a morphological the Andean range on a landscape of rolling piedmont species concept (morphospecies). Hemiepiphytes hills, mostly covered by mature tropical rain forest rooted within a plot were also inventoried using this and lacking large deforested areas. Mature forests method, measuring the diameters of their descending were studied within the Huaorani indigenous territo- roots and analysed separately from lianas, as recom- ries around the Dicaro and Guiyero communities, mended by Gerwing et al. (2006). Multiple stems *60 km apart, at 250–300 m elevation (Fig. 1). were measured separately, but all stems rooting in the Three different broad habitats can be recognised: same place were counted as one individual. Speci- (i) well-drained upland tierra firme forests, never mens were collected to voucher each name and in flooded by rivers, (ii) well-drained floodplain forests, doubtful cases to identify a stem. All specimens were periodically flooded by rivers or streams, and (iii) first sorted to species or morphospecies level. Then, permanently inundated, poorly drained swamp for- the sterile vouchers were identified by matching them ests. Probably more than 90% of the Yasunı´ land- with vouchers identified by specialists or professional scape is covered by tierra firme forests, whereas most botanists which are deposited at AAU, MO, NY, floodplain and swamp habitats are confined to narrow QCA and QCNE herbaria (acronyms according to bands close to streams and rivers (Macı´a personal Holmgren et al. 1990). Classical taxonomy have been observations). According to climatic data obtained used to facilitate floristic comparisons with past from Yasunı´ Research Station for the period papers, although there are recent changes (e.g. 1995–2007, mean annual precipitation is Bombacaceae, Sterculiaceae and Tiliaceae rather *2800 mm with a peak of rainfall during the months than Malvaceae). of May and June, and mean annual temperature is Duplicates of the specimens were distributed to *25°C (see also Romero-Saltos et al.