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In the tropics, some agricultural lands are abandoned for economic or technical reasons, leading to the recovery of woody vegetation. Our research aimed to identify the main drivers of spontaneous recovery of vegetation in a basin located in the Colombian Andes. This was done by combining spatially explicit environmental and socioeconomic variables at landscape (e.g. distances to human settlements, to roads, and to forests and mean annual precipitation) and local scales (e.g. depth of the organic layer, soil bulk density, and canopy openness). These variables were measured in 28 temporal plots of 500 m2 each, established in land cover transitions that showed the recovery of woody vegetation. The recovered woody vegetation between 1986 and 2012 exhibited a gregarious spatial pattern at the landscape scale. Ordination analysis showed distinct floristic composition among transitions and remnant forests, and species associated to each one through an indicator species analysis. Multivariate analyses revealed the relationship between the transitions and variables at both scales. Woody vegetation recovery occurred near remnant forests and far from human settlements at the landscape scale. The soil conditions (content and depth of the organic horizon and bulk density) were the main drivers at the local scale. Our findings also highlight the necessity to define different restoration approaches such as incorporation of sites where socioeconomic and environmental conditions favor the spontaneous recovery of vegetation into the existing network of protected areas in the region, and to implement active restoration projects in perturbed sites to accelerate the recovery process of Andean forests.

Extreme events affect coastal vegetation in several ways. They cause massive tree defoliations and mortality that carry changes in vegetation structure and floristic composition. In order to assess these changes in dry tropical forests, coastal vegetation and mangroves in El Rosario archipelago, and their relationship with extreme events between 2002 and 2014, Quickbird and Worldview Satellite images with uneven periodicity were analyzed and the Normalized Difference Vegetation Index (NDVI) was calculated for these vegetation covers. Time series analysis was performed to oceanographic and climate variables such as maximum wind velocity, daily precipitation, significant wave height, peak wave period and maximum and minimum air temperatures. The first two axes of a redundancy analysis explained 65% of data variance (p value ≤ 0.05) and showed that the decrease of the NDVI and extension of beach vegetation were related to increases in wind frequency and intensity. However, mangrove vegetation was benefited by the increase in the frequency of short drought events, although their NDVI decreased when these drought events became longer. Drought events were related to El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) anomalies that had the strongest effects on coastal vegetation and dry forest, as shown by the minimum values of NDVI recorded in 2010. Mangrove vegetation was more resilient to such droughts and strong winds than coastal and dry forest vegetation due to their location along bays or surrounding internal lagoons.

Within the tropics, the species richness of tree communities is strongly and positively associated with precipitation. Previous research has suggested that this macroecological pattern is driven by the negative effect of water-stress on the physiological processes of most tree species. This implies that the range limits of taxa are defined by their ability to occur under dry conditions, and thus in terms of species distributions predicts a nested pattern of taxa distribution from wet to dry areas. However, this ‘dry-tolerance’ hypothesis has yet to be adequately tested at large spatial and taxonomic scales. Here, using a dataset of 531 inventory plots of closed canopy forest distributed across the western Neotropics we investigated how precipitation, evaluated both as mean annual precipitation and as the maximum climatological water deficit, influences the distribution of tropical tree species, genera and families. We find that the distributions of tree taxa are indeed nested along precipitation gradients in the western Neotropics. Taxa tolerant to seasonal drought are disproportionally widespread across the precipitation gradient, with most reaching even the wettest climates sampled; however, most taxa analysed are restricted to wet areas. Our results suggest that the ‘dry tolerance' hypothesis has broad applicability in the world's most species-rich forests. In addition, the large number of species restricted to wetter conditions strongly indicates that an increased frequency of drought could severely threaten biodiversity in this region. Overall, this study establishes a baseline for exploring how tropical forest tree composition may change in response to current and future environmental changes in this region. © 2016 The Authors

Throughout the last 15 years, researchers at the National University of Colombia at Medellin have studied Colombian mangroves. Remote sensing, pollen analysis of superficial and deep sediments, Holocene coastal vegetation dynamics, sediment dating using 14 C and 210 Pb, sampling in temporary plots, sampling in temporary and permanent plots, and other techniques have been applied to elucidate long- and shortterm mangrove community dynamics. The studied root fouling community is structured by several regulatory mechanisms; habitat heterogeneity increases species richness and abundance. Fringe mangroves were related to Ca concentration in the soil and the increased dominance of Laguncularia racemosa and other nonmangrove tree species, while the riverine mangroves were associated with Mg concentration and the dominance of Rhizophora mangle. The seedling and mangrove tree distributions are determined by a complex gradient of natural and anthropogenic disturbances. Mangrove pollen from surface sediments and the existing vegetation and geomorphology are close interrelated. Plant pollen of mangrove and salt marsh reflects environmental and disturbance conditions, and also reveals forest types. Forest dynamics in both coasts and their sensitivity of to anthropogenic processes are well documented in the Late Quaternary fossil record. Our studies of short and long term allow us to predict the dynamics of mangroves under different scenarios of climate change and anthropogenic stress factors that are operating in Colombian coasts. Future research arises from these results on mangrove forests dynamics, sea-level rise at a fine scale using palynology, conservation biology, and carbon dynamics.

Local geomorphology plays an important role in the response of mangrove communities to both sea-level rise and precipitation changes, mostly because it exerts an important control of the erosion–progradation balance. Here we present contrasting changes in the palynological records of two sediment cores retrieved from locations occupied by mangroves in the northeastern Caribbean coast of Colombia: Calancala and Navio Quebrado. Sediments were treated with standard procedures used in palynologycal analysis, and dated with AMS 14C and 210Pb. Age-depth models of both cores were constructed by linear interpolation between dated samples. The main modern differences between the studied sites are fresh water availability and sediment supply throughout the year. While Calancala, located at the Rancheria River Delta, has direct fresh water influence throughout the year, coastal lagoon Navio Quebrado is only sporadically influenced by fresh water sources. According to our findings, two main factors contributed to mangrove establishment in the Colombian Caribbean: i) high and accelerated sea-level rise around 6000 cal yr BP originating coastal lagoons that favored mangrove establishment, and ii) marine still stand and high precipitation around 3000 cal yr BP leading to a second wave of mangrove expansion. A drought between about 2850 and 2450 cal yr BP and the strengthening of easterly trade winds caused a change from Rhizophora-dominated to Avicennia-dominated stands. Increased precipitation after 2500 cal yr BP and subsequent increase of fluvial sediment input promoted recovery of Rhizophora-dominated mangroves. Sea-level rise during the last 150 yr has caused landward mangrove expansions in deltas and progradation of coastal environments. However, the general pattern shows a net loss of mangrove vegetation as the result of coastal erosion.

The precise characterisation of present-day mangrove ecosystems from modern pollen rain facilitates the accurate use of fossil pollen data for late Quaternary sea level and environmental reconstructions. Here, we investigate whether the analysis of pollen rain data corroborates existing floristic and structural characterisation of different mangrove types at the Caribbean island of San Andres, Colombia. At 82 plots along 20 transects of four distinct mangrove types, samples were obtained of (i) surface sediments for pollen analysis, and (ii) a range of environmental parameters (including inundation levels, salinity and pH). This information was compared to previously sampled mangrove composition and tree basal area. In surface sediment samples 82 pollen taxa were found, from which 19 were present in the vegetation plots. However, because pollen may be transported by wind and/or watercourses, the overall floristic composition of the different forest types may not necessarily be reflected by the pollen spectra. Local vegetation (i.e. mangroves and beach) represented > 90% of the pollen spectra, while the regional one (i.e. hinterland forests) represented The groups were characterised based on (i) the dominance of at least one of the true mangrove species from pollen data ordination and the presence of associated species, and (ii) their relationship with environmental parameters. Rhizophora was present in all plot samples, but did not contribute to forest type separation. In fact, just three true mangrove species proved reliable indicators of (i) high salinity and fringe mangroves (i.e. Avicennia), (ii) high pH levels and landward mangroves (i.e. Conocarpus), and (iii) natural or anthropogenic caused disturbance of forest stands (Laguncularia and associated Acrostichum fern). Hence our study confirms that mangrove pollen spectra can be accurately used to describe different mangrove environments for fossil based palaeoecological reconstructions.

Article history:Received 18 September 2008Received in revised form 23 March 2009Accepted 1 April 2009Available online 15 April 2009Keywords:mangrovespollen analysissurface sedimentsCaribbean Distribution patterns of mangrove pollen taxa in recent surface sediments of the lagoon system of Cispata arecompared with geomorphological and vegetational patterns. The pollen spectra of 51 samples show the floralcomposition and structure of mangrove stands in three main geomorphic units in the study area. The oldestmangrove stands, with the highest tree mean diameter at breast height and total height, are represented inthe pollen spectra by the highest mean percentages (N65%) mainly Rhizophora mangle. The area withestuarine conditions shows, mean mangrove pollen percentages between 35 and 50% reflecting themangrove colonization process since 1930, as well as current anthropogenic disturbance. Lowest proportionsof mangrove pollen (b25%) are found in the foothills, reflecting high disturbance of mangroves and thetransition from mangroves to terra firme forest. Distribution patterns of the pollen and spores indicate thatwater transport is more important than wind transport over short distance and reflect local vegetation. Fernspores and pollen grains of secondary forest taxa and grasslands are widely distributed and reflect regionalvegetation. Rhizophora pollen proportions reflect its relative abundance in the forest stands. Even lowproportions of Avicennia pollen indicate this species’ dominance in sparse stands and saline back swampconditions. Conocarpus presence provides evidence of supratidal location of stands. An inverse relationshipbetween proportions of Laguncularia pollen and Acrostichum spores demonstrates successional processestriggered by anthropogenic disturbance. This is the first report on pollen in surface sediments in theColombian Caribbean. As such, the data should prove valuable in efforts to apply interpretations of marinerecords to reconstruct past environmental and climate changes in the Caribbean.© 2009 Elsevier B.V. All rights reserved.

The Late Quaternary paleoenvironmental history from Pacific slopes of the western Andes is reconstructed by pollen analysis of 32 samples from two marine sediment cores from the Panama Basin, eastern equatorial Pacific: core ODP 677B (83°44.2200′ W, 1°12.1440′ N, 3473 m water depth) is 185 cm long and spans the last 39,410 years, core TR 163-38 (81.583° W, 1.337° N, 2200 m water depth) is 103 cm long and covers the last 17,380 years. Six ecological groups were established: mangrove, brackish and fresh water swamps, terra firma lowland forests, broad range taxa, Andean forests, and open vegetation. A good correspondence was found between the changes of these ecological groups in the two cores. The records evidence the continuous presence of all vegetation types during the last 39,410 years and specially the uninterrupted occurrence of tropical rain forest. They record a development from: (1) a cold and humid phase (39,410–28,120 yr cal BP) with moderately high sea levels, (2) the coldest and driest phase in the record (28,120–14,500 yr cal BP) accompanied by the lowest sea levels, (3) a transitional phase when sea level rose and humid conditions dominated, (4) a stage (11,300–5600 yr cal BP) of the highest sea levels and moisture conditions including a drier period ∼7000 yr BP, to (5) a final period (5600 yr cal BP–Present) when sea level reached its present height, humidity persisted, and indicators of disturbance expanded. Peaks in pollen and spore concentration, associated with high river discharge periods, indicate periods of higher precipitation around 33,500, 28,000 and 12,000–9000 yr cal BP. Although main vegetation responses seem to reflect rainfall and moisture variations, a good correspondence was found between δ18O values and percentages of Andean and lowland pollen, suggesting that vegetation also responded to tempearture changes.

Successional sequences from forested wetlands in the Middle Atrato River Basin were reconstructed using characterisation of present vegetation communities and palynological analysis. A 4.8 km transect, drawn across a river meander, and two 6 and 8 m deep sediment cores (San Martin and Villanueva) were collected in the floodplain within two different vegetation assemblages. Based on the floristic and environmental characteristics of the local vegetation communities, ecological changes spanning the last 4 ka (cal years BP) were analysed in San Martin and Villanueva cores. Present vegetation is dominated by four communities determined by flood tolerance and drainage conditions. We found Euterpe oleraceae , Mauritiella macroclada – Campnosperma panamensis and Oenocarpus bataua forests, and mixed forest and open vegetation in a gradient from poor to improved drainage conditions. Vegetation changes in the palynological record suggest that sedimentation and erosion processes on flood basins are due to changes in drainage conditions and to variable flooding levels. A wet period in the 4 to 2.7 ka interval is postulated, which might be related to sea level rise or local subsidence. Lower flooding levels and improved drainage conditions dominated the 2.7 to ∼ 1.6 ka interval, whereas a flooding event (and a hiatus) occurred between 1.5 and 0.5 ka. This flooding event might be synchronous with analogous events as recorded in the Colombian Amazonia between 1.6 and 1.45 ka. Forest disturbance, probably of anthropogenic origin, is recorded in both sites since 0.5 ka.