Tropical Premontane Forest Research Articles

Effects of landscape structure on restoration success in tropical premontane forest

Reversing large-scale habitat degradation and deforestation goes beyond what can be achieved by site-level ecological restoration and a landscape ecology perspective is fundamental. Here we assess the relative importance of tree cover and its configuration on forest-dependent birds and late-successional tree seedlings in restoration sites in southern Costa Rica. The abundance and species richness of birds increased in landscapes with more corridors, higher tree cover, and lower levels of fragmentation, highlighting the importance of riparian corridors for connectivity, and continuous tree cover as suitable habitat. Landscape variables affected abundance and species richness of seedlings similarly, but effects were weaker, possibly because seedlings face establishment limitation in addition to dispersal limitation. Moreover, the scale of landscape effects on seedlings was small, likely because proximal individual trees can significantly influence recruitment in restoration plots. Results underscore the importance of incorporating landscape-level metrics to restoration projects, as knowing the extent, and how the landscape may affect restoration outcomes can help to infer what kind of species will arrive to restoration plots.

Restoration plantations accelerate dead wood accumulation in tropical premontane forests

Dead wood stores 10–20% of global forest carbon stocks, but its recovery and restoration in secondary tropical forests are poorly documented. In this study, we evaluated (1) the recovery pattern of dead wood volumes across a chronosequence of secondary tropical forests that used to be former coffee plantations, and (2) the efficiency of two common restoration strategies to recover dead wood volumes similar to those found in old-growth forests, all in a tropical premontane landscape in southern Costa Rica. Restoration strategies consisted of plantations and natural regeneration. Plantations consist of plots where two endemic (Terminalia amazonia and Vochysia guatemalensis) and two naturalized (Inga edulis and Ertyhrina poeppegiana) species were planted in rows. Natural regeneration consists of plots where no trees were planted, but where agriculture or cattle are excluded though fencing and vegetation is allowed to regenerate naturally. We hypothesized that (1) dead wood volumes increase with forest age following a logistic shape, and that (2) restoration plantations recover dead wood volumes more quickly compared to naturally regenerated forests. We measured dead wood volumes in a total of 35 forest fragments that were former coffee plantations or are currently old-growth forests and 10 restoration plots containing either natural regeneration or restoration plantations that were former fallow or pasture using strip transects. Dead wood volumes significantly increased with forest age following a logistic shape, starting with very low values in early ages (3–5 years), increasing rapidly (6–50 years), and ending with high and relatively stable values after 50 years of age. In addition, plantations (16 to 17 years old) recovered 41% of dead wood volumes found in old-growth forests > 100 years old, whereas naturally regenerated forests of the same age only recovered 1.7% of dead wood volumes found in old-growth forests. Our study shows that restoration plantations not only accelerate the recovery of above ground biomass, but also accelerate the recovery of dead wood in premontane Neotropical ecosystems. This indicates that tree planting positively affects carbon storage, and potentially the preservation of dead wood-associated biodiversity.

The effect of environmental variables on nightly activity patterns of insectivorous bats monitored over ten years in a tropical premontane forest, Costa Rica

ABSTRACT We investigated the role of environmental and temporal variables on the activity of 20 species of aerial insectivorous bats at a site in tropical premontane forest in Monteverde, Costa Rica. The primary study site was an opening in secondary forest adjacent to the Children’s Eternal Rainforest. We passively monitored the echolocation calls of all bats detected by an Anabat II detector all night for 1,147 nights from November 2000 through August 2010, from which we were able to identify the species in more than 250,000 bat passes. Simultaneously, we recorded environmental variables. Five species accounted for most of the activity, but the relative frequency of these species fluctuated widely over the ten-year period. The likelihood of any one of the three most common species being present was significantly influenced by wind, rain, phase of the moon, the time of night, the season of the year, and the presence of the other two species. In general, strong winds are associated with an increase in bat activity, moderate to heavy rain seems to halt bat activity, full moon appears to depress bat activity, and bats seem to be most active early in the evening. The number of bat passes at the study site declined over the ten-year period, possibly at least partially due to bat preference for foraging near bright lights, which increased markedly during the period due to development for tourism.

Long-Term Vegetation Dynamics in a Megadiverse Hotspot: The Ice-Age Record of a Pre-montane Forest of Central Ecuador.

Tropical ecosystems play a key role in many aspects of Earth system dynamics currently of global concern, including carbon sequestration and biodiversity. To accurately understand complex tropical systems it is necessary to parameterise key ecological aspects, such as rates of change (RoC), species turnover, dynamism, resilience, or stability. To obtain a long-term (>50 years) perspective on these ecological aspects we must turn to the fossil record. However, compared to temperate zones, collecting continuous sedimentary archives in the lowland tropics is often difficult due to the active landscape processes, with potentially frequent volcanic, tectonic, and/or fluvial events confounding sediment deposition, preservation, and recovery. Consequently, the nature, and drivers, of vegetation dynamics during the last glacial are barely known from many non-montane tropical landscapes. One of the first lowland Amazonian locations from which palaeoecological data were obtained was an outcrop near Mera (Ecuador). Mera was discovered, and analysed, by Paul Colinvaux in the 1980s, but his interpretation of the data as indicative of a forested glacial period were criticised based on the ecology and age control. Here we present new palaeoecological data from a lake located less than 10 km away from Mera. Sediment cores raised from Laguna Pindo (1250 masl; 1°27′S, 78°05′W) have been shown to span the late last glacial period [50–13 cal kyr BP (calibrated kiloyears before present)]. The palaeoecological information obtained from Laguna Pindo indicate that the region was characterised by a relatively stable plant community, formed by taxa nowadays common at both mid and high elevations. Miconia was the dominant taxon until around 30 cal kyr BP, when it was replaced by Hedyosmum, Asteraceae and Ilex among other taxa. Heat intolerant taxa including Podocarpus, Alnus, and Myrica peaked around the onset of the Last Glacial Maximum (c. 21 cal kyr BP). The results obtained from Laguna Pindo support Colinvaux’s hypothesis that glacial cooling resulted in a reshuffling of taxa in the region but did not lead to a loss of the forest structure. Wide tolerances of the plant species occurring to glacial temperature range and cloud formation have been suggested to explain Pindo forest stability. This scenario is radically different than the present situation, so vulnerability of the tropical pre-montane forest is highlighted to be increased in the next decades.

A new dagger nematode, Xiphinema poasense n. sp. (Nematoda: Longidoridae), from Costa Rica

A new dagger nematode,Xiphinema poasensen. sp., is described and illustrated from three populations extracted from soil associated with a combined plantation ofEucalyptussp.,Cupressussp. andPennisetumsp. and wild plants from a tropical pre-montane forest in Costa Rica. The new dagger nematode is characterised by a moderate body size 2612 (2416-3042) μm long, a rounded lip region 15.0 (13.5-16.5) μm broad, separated from the body contour by a shallow depression, amphidial fovea large, stirrup-shaped, a very long odontostyle (175 (164-188) μm), stylet guiding ring located 167 (136-181) μm from anterior end, vulva situated anterior to mid-body (36-40%), anterior genital branch complete but strongly reduced, without uterine differentiation, female tail short, hemispherical to convex-conoid with a c′ ratio = 0.7 (0.6-0.8) and bearing two pairs of caudal pores, and male absent. Integrative diagnosis was completed with molecular data using D2-D3 expansion segments of 28S rRNA, ITS1 region, partial 18S-rRNA and the partial mitochondrial gene cytochrome c oxidase subunit 1 (coxI). The phylogenetic relationships based on D2-D3 segments of this species with otherXiphinemaspp. of theX.non-americanumgroup indicated thatX. poasensen. sp. clustered with other species with a reduced anterior genital branch from the morphospecies Group 2,viz.,X. costaricenseandX. krugi. However, the phylogeny ofcoxIand partial 18S rRNA gene revealed that the new species did not cluster withXiphinemaspecies having the anterior genital branch absent or reduced (i.e., morphospecies Groups 1 and 2, respectively).

Plasticity in nitrogen uptake among plant species with contrasting nutrient acquisition strategies in a tropical forest.

Nitrogen (N) availability influences the productivity and distribution of plants in tropical montane forests. Strategies to acquire soil N, such as direct uptake of organic compounds or associations with root symbionts to enhance N acquisition in exchange for carbon (C), may facilitate plant species coexistence and ecosystem N retention. Alternatively, rapid microbial turnover of soil N forms in tropical soils might promote flexible plant N-uptake strategies and mediate species coexistence. We tested whether sympatric plant species with different root symbiont associations, and therefore potentially different nutrient acquisition strategies, partition chemical forms of N or show plasticity in N uptake in a tropical pre-montane forest in Panama. We traced the movement of three 15 N forms into soil pools, microbes, and seedlings of eleven species differing in root traits. Seedlings were grown in a split-plot field transplant experiment, with plots receiving equimolar mixtures of ammonium, nitrate, and glycine, with one form isotopically labeled in each block. After 48 h, more 15 N was recovered in microbes than in plants, while all pools (extractable organic and inorganic N, microbial biomass, and leaves) contained greater amounts of 15 N from nitrate than from ammonium or glycine. Furthermore, 13 C from dual-labeled glycine was not recovered in the leaves of any seedling, suggesting the studied species do not directly take up organic N or transform organic N prior to translocation to leaves. Nitrogen uptake differed by root symbiontgroup only for nitrate, with greater 15 N recovery in plants with arbuscular mycorrhizal(AM) associations or proteoid roots compared to orchids. Some root trait groups differed in 15 N recovery among N forms, with greater nitrate uptake than ammonium or glycine by AM-associated and N2 -fixing plants. However, only five of eleven species showed differences in uptake among N forms. These results indicate flexibility in uptake of N forms in tropical plants across root trait groups, with only a few species displaying weak preferences for a specific N form.

Losing legs and walking hard: effects of autotomy and different substrates in the locomotion of harvestmen in the genusPrionostemma

Autotomy, the strategy of voluntarily releasing a leg during an encounter with a potential predator or in agonistic interactions between conspecifics, is common in animals. The potential costs of this behavior have been scarcely studied. In addition, locomotion and substrate-dependent performance might be affected by autotomy. We did a comparative and observational study to investigate whether losing legs affects the escape speed and trajectory of harvestmen in the genus Prionostemma Pocock, 1903 (Eupnoi: Sclerosomatidae) on different substrates: soil (the least roughened), smooth bark and mossy bark (the most roughened) in a tropical premontane forest in Costa Rica. We observed that 71% of the individuals found were missing at least one leg. Harvestmen, regardless of leg condition, walked faster and made fewer turns in their trajectory in the soil. While climbing, they were faster on smooth bark than in moss. On all substrates, autotomized individuals were slower and had a more erratic trajectory than intact ones. The type of missing legs (sensory or locomotor) had no influence on the speed or trajectory. We experimentally induced autotomy and found that walking speed on soil decreases if individuals lose a leg. Our findings confirm that losing legs affects locomotion, and we provide novel insights on how locomotion in these harvestmen depends on surface roughness. Our data suggest that moss could be a type of substrate that requires more elaborate skills in balance, orientation and texture recognition than smooth bark.

Increases in Soil Aggregation Following Phosphorus Additions in a Tropical Premontane Forest are Not Driven by Root and Arbuscular Mycorrhizal Fungal Abundances

Tropical ecosystems have an important role in global change scenarios, in part because they serve as a large terrestrial carbon pool. Carbon protection is mediated by soil aggregation processes, whereby biotic and abiotic factors influence the formation and stability of aggregates. Nutrient additions may affect soil structure indirectly by simultaneous shifts in biotic factors, mainly roots and fungal hyphae, but also via impacts on abiotic soil properties. Here, we tested the hypothesis that soil aggregation will be affected by nutrient additions primarily via changes in arbuscular mycorrhizal fungal (AMF) hyphae and root length in a pristine tropical forest system. Therefore, the percentage of water-stable macroaggregates (> 250µm) (WSA) and the soil mean weight diameter (MWD) was analyzed, as well as nutrient contents, pH, root length and AMF abundance. Phosphorus additions significantly increased the amount of WSA, which was consistent across two different sampling times. Despite a positive effect of phosphorus additions on extraradical AMF biomass, no relationship between WSA and extra-radical AMF nor roots was revealed by regression analyses, contrary to the proposed hypothesis. These findings emphasize the importance of analyzing soil structure in understudied tropical systems, since it might be affected by increasing nutrient deposition expected in the future.

Performance of Seedlings of a Shade-Tolerant Tropical Tree Species after Moderate Addition of N and P

Nitrogen deposition to tropical forests is predicted to increase in future in many regions due to agricultural intensification. We conducted a seedling transplantation experiment in a tropical premontane forest in Ecuador with a locally abundant late-successional tree species (Pouteria torta, Sapotaceae) aimed at detecting species-specific responses to moderate N and P addition and to understand how increasing nutrient availability will affect regeneration. From locally collected seeds, 320 seedlings were produced and transplanted to the plots of the Ecuadorian Nutrient Manipulation Experiment (NUMEX) with three treatments (moderate N addition: 50 kg N ha-1 yr-1, moderate P addition: 10 kg P ha-1 yr-1 and combined N and P addition) and a control (80 plants per treatment). After 12 months, mortality, relative growth rate, leaf nutrient content and leaf herbivory rate were measured. N and NP addition significantly increased the mortality rate (70 % vs. 54 % in the control). However, N and P addition also increased the diameter growth rate of the surviving seedlings. N and P addition did not alter foliar nutrient concentrations and leaf N:P ratio, but N addition decreased the leaf C:N ratio and increased SLA. P addition (but not N addition) resulted in higher leaf area loss to herbivore consumption and also shifted carbon allocation to root growth. This fertilization experiment with a common rainforest tree species conducted in old-growth forest shows that already moderate doses of added N and P are affecting seedling performance which most likely will have consequences for the competitive strength in the understory and the recruitment success of P. torta. Simultaneous increases in growth, herbivory and mortality rates make it difficult to assess the species’ overall performance and predict how a future increase in nutrient deposition will alter the abundance of this species in the Andean tropical montane forests.

Inventory of the orchids in the humid tropical premontane forest on Uchumachi Mountain, nor Yungas region of La Paz, Bolivia

Para conocer la diversidad e importancia de las orquídeas en el bosque húmedo tropical premon- tano del Cerro Uchumachi (Nor Yungas, La Paz, Bolivia), se realizó un inventario de orquídeas durante 8 meses (febrero a septiembre de 2006) en un área aproximada a 80 ha, utilizando transectas lineales que ubican la principal en el camino carretero comprendido entre dos comunidades. Se establecieron 95 parcelas de 20 m x 20 m, en las que se efectuaron la recolección, herborización, descripción botánica y taxonomía de las mis- mas. La búsqueda y recolección de orquídeas en las transectas dieron como resultado valores de: densidad absoluta, densidad relativa, y frecuencia. Se encontraron un total de 2159 orquídeas de 16 géneros y 31 especies, pero se crea que existen más que no han sido identificados por la falta de floración durante el tiempo del estudio. La especie de mayor densidad fue Epidendrum funckii con una densidad relativa de 33.72%. Asimismo la especie que se presentó con más frecuencia en las parcelas fue Pleurothallis xantochlora con 22.11%.

Impact of the invasive plant Syzigium jambos (Myrtaceae) on patterns of understory seedling abundance in a Tropical Premontane Forest, Costa Rica

Habitat fragmentation, along with other human-induced disturbances, increase the vulnerability of native habitats to be invaded by aggressive, ecologically released, exotic species. Syzigium jambos (L.) Alston (Myrtaceae, Rose Apple) is an important invader still spreading throughout Hawaii, the Antilles, Central and South America. This study examines the effects of S. jambos on plant understory diversity in a 25 ha Tropical Premontane Moist Forest in Atenas, Alajuela, Costa Rica, a protected watershed that supplies drinking water for several human communities. Our final objective is to develop a management strategy combining water protection with the preservation of a representative sample of the original plant diversity in the area. Thirty 2 x 2 m plots were distributed throughout the Municipal Forest maintaining a minimum of 10 m between plots, and 2 m from trails, to sample all understory seedlings and saplings of S. jambos, Coffea arabica (coffee) and tree seedlings. We found a clear dominance of S. jambos over all other understory plants. Of the total 1,285 sampled plants, S. jambos comprised 51%, coffee seedlings represented 14.78%, being the rest tree seedlings. Syzigium jambos had the highest density (5.46 plants/m2, S.D. = 6.44) compared to tree (3.67 plants/m2, S.D. = 3.44) and coffee seedlings (1.58 plants/m2, S.D. = 2.13). There was a highly significant negative relationship between the relative abundance of S. jambos and tree (r2 = 0.52, p < 0.00001) and coffee seedlings (r2 = 0.28, p < 0.002). The abundance of coffee seedlings did not affect the abundance of tree seedlings (r2 = 0.01, p < 0.58). Since the canopy of the Municipal Forest is relatively closed and composed of a monolayer of trees with almost no overlapping crowns, we found no relationship between canopy cover and the abundance of S. jambos. The height distribution indicated that the majority of S. jambos individuals were seedlings and saplings (height < or = 1.5 m), with only 4.6% classified as adults, (height > or = 2 m). The results show a clear role of S. jambos as an aggressive, invasive species within the Municipal Forest. This invasion is enhanced by both the ecological characteristics of the species and the fragmentation of the forest by coffee farming around the site. Among a variety of management possibilities, an ecosystem-level approach of manually removing S. jambos over time while replanting native species appears to be the preferred strategy, given the intended continued use of the Municipal Forest as a source of drinking water and as a representative sample of the original vegetation of the area.

Testing applied nucleation as a strategy to facilitate tropical forest recovery

Summary Active forest restoration typically involves planting trees over large areas; this practice is costly, however, and establishing homogeneous plantations may favour the recruitment of a particular suite of species and strongly influence the successional trajectory. An alternative approach is to plant nuclei (islands) of trees to simulate the nucleation model of succession and accelerate natural recovery. We evaluated natural tree recruitment over 4 years in a restoration study replicated at eight former pasture sites in the tropical premontane forest zone of southern Costa Rica. At each site, two active restoration strategies were established in 50 × 50 m plots: planting trees throughout, and planting different‐sized tree islands (4 × 4, 8 × 8, 12 × 12 m) within the plot. Restoration plots were compared to similar‐sized controls undergoing passive restoration. Sites were spread across c. 100 km2 and distributed along a gradient of surrounding forest, allowing us to compare the relative importance of adjacent forest to that of within‐site treatment on tree recruitment. Recruitment of animal‐dispersed tree species was more than twofold higher in active (μ = 0·45 recruits m−2) as compared to passive restoration; recruitment was equivalent in plantation and island treatments, even though only 20% of the area in island plots was planted originally. The majority of recruits (&gt;90%) represented early successional species (n = 54 species total). Density of animal‐dispersed recruits was greater in large (0·80 ± 0·66 m−2) than small (0·28 ± 0·36 m−2) islands and intermediate in medium‐sized islands. Seedling recruitment (&lt;1 m tall) was greater in the interior of islands as compared to plantations, whereas sapling recruitment was similar, suggesting that island interiors may develop greater density of woody recruits as succession proceeds. Surrounding forest cover did not influence density or species richness of recruits among sites, although this factor may become more important over time. Synthesis and applications. Applied nucleation is a promising restoration strategy that can accelerate forest recovery to a similar degree as plantation‐style restoration but is more economical. Appropriate island size is on the order of c. 100 m2. Practitioners should consider the methodology as an alternative to large‐scale plantings.

Tree turnover in a premontane neotropical forest (1998–2009) in Costa Rica

Tropical premontane forests between 700 and 1,400 m.a.s.l. represent a particular component of the gamma diversity of neotropical ecosystems; however, the extent of information about their dynamics lags behind the more studied lowland rain forests. Data from three 1-ha permanent plots in a premontane forest in Costa Rica collected during an 11-year period (1998–2009) suggested a high tree turnover rate for this ecosystem (high mortality rate, λ = 2.4% and annual recruitment, μ = 2.6%). The floristic composition did not significantly change during the study period, but its high dynamism (2.4%) exceeded that of several reported values from highly diverse neotropical lowland rain forests. The documented decrease in abundance (8.6%) and basal area (14.3%) of trees ≥10 cm in DBH differs from the general trend of increase described for several lowland tropical rain forests in recent decades. We detected a significant population reduction (>15% of individuals from 1998 to 2009) in several relatively abundant tree species, whereas the populations of the three most dominant species remained nearly constant. The high tree turnover recorded for this premontane forest might not have affected tree diversity; but it might be promoting recruitment and growth of some tree species that may eventually become over-dominant in this ecosystem.

Tree Responses to Edge Effects and Canopy Openness in a Tropical Montane Forest Fragment in Southern Costa Rica

Tropical forests frequently experience the opening and closing of canopy gaps as part of their natural dynamics. When fragmented, the forests are also exposed to edges, which (at least in the lowlands) cause increased mortality on the fragment's periphery and—depending on the fragment size—also on the forest interior. Here we explore if the presence of edges increase the rate at which the canopy opens in a montane forest and if and how that interaction affects the vegetation composition and structure. At Las Cruces Biological Station (SW Costa Rica), we surveyed four 150 m edge-to-interior transects to evaluate changes in vegetation structure (stem density and basal area for all plants with DBH &gt; 5 cm) and species richness and composition as a function of both distance to the edge and canopy openness. Edge proximity did not increase canopy openness. Canopy openness, however, did affect stem density, species richness, and composition. Consequently, heterogeneity in forest structure, diversity, or composition could not be attributed to indirect edge effects. Forest edges, however, had a direct effect on species composition, but with a negligible effect on species diversity and forest structure. Overall, these results reveal that the structure, diversity, and composition of tree communities in this tropical premontane forest fragment are more strongly influenced by canopy openness than by the proximity of edges.

Establishment of Epiphytic Bromeliads in Successional Tropical Premontane Forests in Costa Rica

ABSTRACTPlant community composition is the combined result of species‐specific competitive abilities and the availability of propagules. For epiphytic plants, current hypotheses consider that dispersal‐related factors are most important. By controlling seed dispersal constraints, we experimentally examined whether the community composition of epiphytic bromeliads in a tropical premontane area is determined during early phases of seedling recruitment. Also, we tested whether establishment success was related to eco‐physiological traits of the species. A total of 7200 seeds were artificially affixed on several host trees in two secondary forest patches and in a mature forest stand. Four bromeliad species with differing physiological characteristics (CAM, C3‐CAM, and C3) and habitat preference (secondary vs. primary forest) were selected. We found that differences in seed germination probability among habitats and species were not likely to influence community assembly. After 2 yr, seedling survival and plant development were relatively higher in the early‐successional forest. Seedling establishment success was not associated with specific physiological and morphological adaptations or habitat preference of the studied species. Our results were not consistent with the described community composition and rates of population recruitment of the studied species in the same successional habitats. The results support the hypothesis that chance and historic events related to seed dispersal have an important influence on community assembly of epiphytic plants. In addition, differences in growth rates and reproductive turnover among species are expected to influence the relative abundance and recruitment rates in a particular habitat.

Threats to biological diversity caused bycoca/cocaine deforestation in Peru

SummaryIndirect sources were used to characterize the nature and magnitude of threats to the native plants and forest ecosystems caused by the cultivation and control ofcoca, the precursor to cocaine, in the Huallaga valley of Peru, whence the majority of the world's cocaine originates. Deforestation is concentrated between 500 and 2000 m in the tropical premontane forest belt. Recent listing of Peru's seed plants permitted a quantification of plant species known from the department of San Martin between 500–2000 m and thus at risk due to forest degradation. This flora consists of 169 plant families, almost 900 genera, and about 2600 species. Fifteen percent of the species are restricted in distribution to Peru, while 6% are known only from San Martin. An additional 778 species, including 46 narrow endemics, are known from vegetation types found below 500 m. More than 223 000 ha of land were found to be in ‘hill agriculture’, consisting predominantly ofcocafields and this suggests that the total impact ofcoca/cocaine deforestation is greatly under-estimated by using simply the area ofcocaunder cultivation. Degraded tropical pre-montane forest may amount to as much as 1 000 000 ha in all of Peru.