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30 results for “lowland tropical forests”

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zenodo40/100

Fig. 31. Tropical lowland evergreen rain forest along the Sungai Sadaunta, 700 m in A Systematic Review Of Sulawesi Bunomys (Muridae, Murinae) With The Description Of Two New Species

Fig. 31. Tropical lowland evergreen rain forest along the Sungai Sadaunta, 700 m (in 1976). Examples of Bunomys chrysocomus were caught amid the rocks in the foreground, deep within the forest, and occasionally on trunks and branches spanning the stream. Similar dense streamside forest and bridging trunks and limbs from old treefalls characterize much of the habitat along the Sungai Sadaunta where B. chrysocomus as well as B. karokophilus, n. sp., were encountered (see Natural History in account of B. chrysocomus).

opencc-by-4.0Dec 2014View details →

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Fig. 29. Tropical lowland evergreen rain forest along the Sungai Sadaunta, 750–850 m in A Systematic Review Of Sulawesi Bunomys (Muridae, Murinae) With The Description Of Two New Species

Fig. 29. Tropical lowland evergreen rain forest along the Sungai Sadaunta, 750–850 m (in 1974). Typical forest composition on terraces just above the stream: dense undergrowth of shrubs and tree saplings, woody vines looping through the understory. Beneath the dense cover, the ground is wet, the air cool. Most Bunomys chrysocomus were trapped in this kind of stream terrace habitat, either on the ground beneath the shrubs, alongside decomposing, moss-covered trunks and limbs lying on the terrace, or among moss-covered rocks. Bunomys karokophilus, n. sp., was encountered in similar habitat.

opencc-by-4.0Dec 2014View details →

dryad36/100

Data from: Can light-saturated photosynthesis in lowland tropical forests be estimated by one light level?

Leaf-level net photosynthesis (An) estimates and associated photosynthetic parameters are crucial for accurately parameterizing photosynthesis models. For tropical forests such data are poorly available and collected at variable light conditions. To avoid over- or underestimation of modelled photosynthesis, it is critical to know at which photosynthetic photon flux density (PPFD) photosynthesis becomes light saturated. We studied the dependence of An on PPFD in two tropical forests in French Guiana. We estimated the light saturation range, including the lowest PPFD level at which Asat (An at light saturation) is reached, as well as the PPFD range at which Asat remained unaltered. The light saturation range was derived from photosynthetic light-response curves, and within-canopy and interspecific differences were studied. We observed wide light saturation ranges of An. Light saturation ranges differed among canopy heights, but a PPFD level of 1000 µmol/m²/s was common across all heights, except for pioneer trees species that did not reach light saturation below 2000 µmol/m²/s. A light intensity of 1000 µmol/m²/s sufficed for measuring Asat of climax species at our study sites, independent of the species or the canopy height. Because of the wide light saturation ranges, results from studies measuring Asat at higher PPFD levels (for upper canopy leaves up to 1600 µmol/m²/s) are comparable with studies measuring at 1000 µmol/m²/s.

opencc-zeroDec 2019View details →

dryad36/100

Closely related tree species support distinct communities of seed-associated fungi in a lowland tropical forest

Previous theoretical work has highlighted the potential for natural enemies to mediate the coexistence of species with similar life-histories via density-dependent effects on survivorship. For plant pathogens to play this role, they must differ in their ability to infect or induce disease in different host plant species. In tropical forests characterized by high diversity, these effects must extend to phylogenetically closely related species pairs. Mortality at the seed and seedling stage strongly influences the abundance and distribution of tropical tree species, but the host preferences and spatial distributions of fungi are rarely determined. We examined how host species identity, relatedness, and seed viability influence the composition of fungal communities associated with seeds of four co-occurring pioneer trees (Cecropia insignis, C. longipes, C. peltata, and Jacaranda copaia). Seeds were buried in mesh bags in five common gardens in the understory of a lowland tropical forest in Panama and retrieved at intervals from 1-30 months. A subset of the seeds in each bag was used to determine germination success. One half of each remaining seed was tested for viability; the other half was used to culture and identify seed-infecting fungi. Seeds were infected by fungi after burial. Although fungal communities differed in viable vs. dead seeds, and across burial locations, community composition primarily varied as a function of plant species identity (30.7% of variation in community composition vs. 4.5% for viability and location together), even for congeneric Cecropia species. Phylogenetic reconstruction showed that relatedness of fungi mostly reflected differences between Jacaranda (Bignoniaceae) and Cecropia (Urticaceae). Although the proportion of germinable seeds decreased gradually over time for all species, intraspecific variation in survival was high at the same location (e.g., ranging from 0-100% for C. peltata) suggesting variable exposure or susceptibility to seed pathogens. Synthesis: Our study provides evidence under field conditions that congeneric tree species with similar life-history differ markedly in seed-associated fungal communities when exposed to the same soilborne fungi. This is a critical first step supporting pathogen mediated coexistence of closely related tree species.

opencc-zeroJan 2021View details →

dryad36/100

Litter decomposition rates across tropical montane and lowland forests are controlled foremost by climate

The "hierarchy of factors" hypothesis states that decomposition rates are controlled primarily by climatic, followed by biological and soil variables. Tropical montane forests (TMF) are globally important ecosystems, yet there have been limited efforts to provide a biome-scale characterization of litter decomposition. We designed a common litter decomposition experiment replicated in 23 tropical montane sites across the Americas, Asia, and Africa and combined these results with a previous study of 23 sites in tropical lowland forests (TLF). Specifically, we investigated (1) spatial heterogeneity in decomposition, (2) the relative importance of biological factors that affect leaf and wood decomposition in TMF and, (3) the role of climate in determining leaf litter decomposition rates within and across the TMF and TLF biomes. Litterbags of two mesh sizes containing Laurus nobilis leaves or birchwood popsicle sticks were spatially dispersed and incubated in TMF sites, for 3 and 7 months on the soil surface and at 10-15 cm depth. The within-site replication demonstrated spatial variability in mass loss. Within TMF, litter type was the predominant biological factor influencing decomposition (leaves > wood), with mesh and burial effects playing a minor role. When comparing across TMF and TLF, climate was the predominant control over decomposition, but the Yasso07 global model (based on mean annual temperature and precipitation) only modestly predicted decomposition rate. Differences in controlling factors between biomes suggest that TMF, with their high rates of carbon storage, must be explicitly considered when developing theory and models to elucidate carbon cycling rates in the tropics.

opencc-zeroJun 2022View details →

dryad36/100

Coping with branch excision when measuring leaf net photosynthetic rates in a lowland tropical forest

Measuring leaf gas exchange from canopy leaves is fundamental for our understanding of photosynthesis and for a realistic representation of carbon uptake in vegetation models. Since canopy leaves are often difficult to reach, especially in tropical forests with emergent trees up to 60 meters at remote places, canopy access techniques such as canopy cranes or towers have facilitated photosynthetic measurements. These structures are expensive and therefore not very common. As an alternative, branches are often cut to enable leaf gas exchange measurements. The effect of branch excision on leaf gas exchange rates should be minimised and quantified to evaluate possible bias. We compared light-saturated leaf net photosynthetic rates measured on excised and intact branches. We selected branches positioned at three canopy positions, estimated relative to the top of the canopy: upper sunlit foliage, middle canopy foliage, and lower canopy foliage. We studied the variation of the effects of branch excision and transport amongst branches at these different heights in the canopy. After excision and transport, light-saturated leaf net photosynthetic rates were close to zero for most leaves due to stomatal closure. However, when the branch had acclimated to its new environmental conditions – which took on average 20 minutes –light-saturated leaf net photosynthetic rates did not significantly differ between the excised and intact branches. We therefore conclude that branch excision does not affect the measurement of light-saturated leaf net photosynthesis, provided that the branch is recut under water and is allowed sufficient time to acclimate to its new environmental conditions.

opencc-zeroFeb 2020View details →

dryad36/100

Composition of non-volant small mammals inhabiting a degradation gradient in a lowland tropical forest in Uganda

A study aimed at assessing the structure of rodent and shrew assemblages inhabiting a degradation gradient while considering rainfall patterns was conducted in one of the few remaining lowland tropical forests in Eastern Africa. We collected a unique dataset of 1411 rodents and shrews, representing 24 species (19 rodents, 5 shrews). The most abundant species alternated in dominance as species abundance significantly fluctuated across the study period following a degradation gradient, While only generalist species were observed near the degraded forest edge, habitat specialists such as Deomys ferrugineus, Malacomys longipes and Scutisorex congicus, were observed in the primary forest interior suggesting a significant association between species and their associated habitats and habitat attributes. There was also an observed correlation between rainfall patterns and species abundance. Capturing more species in adjacent fallows and along the degraded forest edge suggests that many species are able to live in degraded habitats that offer a variety of food resources. The continued pressure on forest resources, however, may lead to changes in habitat structure. This, coupled with the dependence of forest ecological functions on rainfall, which is typically not the case, may ultimately cause the local extinction of highly specialized but less adaptable species.

opencc-zeroAug 2023View details →

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