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Habitat of Entandrophragma excelsum at Kilimanjaro with forest undergrowth (mainly Dracaena fragrans, upper left and lower right), epiphytes (mainly Drynaria volkensii, upper right), buttresses (middle left) and low lianas (Culcasia falcifolia, lower left and right)
Source publication
While world records of tree heights were set by American, Australian and
Asian tree species, Africa seemed to play no role here. In our study we show that
Entandrophragma excelsum (Meliaceae) found in a remote valley at Kilimanjaro has
to be included in the list of the world’s superlative trees. Estimating tree age from
growth rates monitored by hi...
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Citations
... Commercial coffee farms have also been established at this elevation belt. Relicts of natural forests are mostly restricted to steep valleys and gorges harboring the tallest trees in Africa (Hemp, 2006a;Hemp et al., 2017). Above the densely populated submontane zone begins the montane forest belt (1800 to 2800 m asl). ...
Deadwood is an important structural and functional component of forest ecosystems and biodiversity. As deadwood can make up large portions of the total aboveground biomass, it plays an important role in the terrestrial carbon (C) cycle. Nevertheless, in tropical ecosystems and especially in Africa, quantitative studies on this topic remain scarce. We conducted an aboveground deadwood inventory along two environmental gradients—elevation and land use— at Mt. Kilimanjaro, Tanzania. We used a huge elevation gradient (3690 m) along the southern slope of the mountain to investigate how deadwood is accumulated across different climate and vegetation zones. We also compared habitats that differed from natural forsts in land-use intensity and disturbance history to assess anthropogenic influence on deadwood accumulation. In our inventory we distinguished coarse woody debris (CWD) from fine woody debris (FWD). Furthermore, we calculated the C and nitrogen (N) content of deadwood and how the C/N ratio varied with decomposition stages and elevation. Total amounts of aboveground deadwood ranged from 0.07 ± 0.04 to 73.78 ± 36.26 Mg ha–1 (Mean ± 1 SE). Across the elevation gradient, total deadwood accumulation was highest at mid-elevations and reached a near-zero minimum at very low and very high altitudes. This unimodal pattern was mainly driven by the corresponding amount of live aboveground biomass and the combined effects of decomposer communities and climate. Land-use conversion from natural forests into traditional homegardens and commercial plantations, in addition to frequent burning, significantly reduced deadwood biomass, but not past selective logging after 30 years of recovery time. Furthermore, we found that deadwood C content increased with altitude. Our study shows that environmental gradients, especially temperature and precipitation, as well as different anthropogenic disturbances can have considerable effects on both the quantity and composition of deadwood in tropical forests.
... The moist tropical lowland forests of Africa are on average less species-rich than neotropical forests, but mean aboveground biomass is higher and average tree height greater (Hemp et al. 2017;Sullivan et al. 2017). In fact, biomass in tropical montane forests on Mt. ...
Tropical forests represent the largest store of terrestrial biomass carbon (C) on earth and contribute over-proportionally to global terrestrial net primary productivity (NPP). How climate change is affecting NPP and C allocation to tree components in forests is not well understood. This is true for tropical forests, but particularly for African tropical forests. Studying forest ecosystems along elevation and related temperature and moisture gradients is one possible approach to address this question. However, the inclusion of belowground productivity data in such studies is scarce. On Mt. Kilimanjaro (Tanzania), we studied aboveground (wood increment, litter fall) and belowground (fine and coarse root) NPP along three elevation transects (c. 1800–3900 m a.s.l.) across four tropical montane forest types to derive C allocation to the major tree components. Total NPP declined continuously with elevation from 8.5 to 2.8 Mg C ha ⁻¹ year ⁻¹ due to significant decline in aboveground NPP, while fine root productivity (sequential coring approach) remained unvaried with around 2 Mg C ha ⁻¹ year ⁻¹ , indicating a marked shift in C allocation to belowground components with elevation. The C and N fluxes to the soil via root litter were far more important than leaf litter inputs in the subalpine Erica forest. Thus, the shift of C allocation to belowground organs with elevation at Mt. Kilimanjaro and other tropical forests suggests increasing nitrogen limitation of aboveground tree growth at higher elevations. Our results show that studying fine root productivity is crucial to understand climate effects on the carbon cycle in tropical forests.
... Trees over 80 m tall have long been recognized in temperate regions-notably the conifer Sequoia sempervirens in California and the broadleaf Eucalyptus regnans in Tasmania, but the discovery of such tall trees in the tropics is recent. Record-sized tropical trees have also recently been discovered in Africa (H ∼ 81.5m, Hemp et al., 2017) and South America (H ∼ 88.5 m, Gorgens et al., 2019). ...
The factors that limit the maximum height of trees, whether ecophysiological or mechanical, are the subject of longstanding debate. Here, we examine the role of mechanical stability in limiting tree height and focus on trees from the tallest tropical forests on Earth, in Sabah, Malaysian Borneo, including the recently discovered tallest tropical tree, a 100.8 m Shorea faguetiana named Menara. We use terrestrial laser scans, in situ strain gauge data and finite element simulations, to map the architecture of tall tropical trees and monitor their response to wind loading. We demonstrate that a tree's risk of breaking due to gravity or self‐weight decreases with tree height and is much more strongly affected by tree architecture than by material properties. In contrast, wind damage risk increases with tree height despite the larger diameters of tall trees, resulting in a U‐shaped curve of mechanical risk with tree height. Our results suggest that the relative rarity of extreme wind speeds in north Borneo may be the reason it is home to the tallest trees in the tropics.
Abstract in MALAY is available with online material.
... Those plots with dominance of Polylepis pauta and lower prevalence of Baccharis padifolia had a positive relationship with higher AGB-C gains. These results suggest the importance large-statured trees, community species composition and their abundances in controlling C of dynamics as previously reported for high tropical and lowlands forests [84,[89][90][91][92]. Further explanation of these differential sequestration rates may be related to the recent heterogeneous human impact that each plot experienced. ...
Few studies exist that document how high-elevation Andean ecosystems recover naturally after the cessation of human activities and this can limit the implementation of cost-effective restoration actions. We assessed Andean forest (Polylepis stands) and páramo grassland recovery along an elevation gradient (3,600–4,350 m.a.s.l.) in the Yanacocha Reserve (Ecuador) where natural recovery has been allowed since 1995. Within the Yanacocha Reserve in 2012 and 2014 the aboveground biomass (AGB), aboveground necromass (AGN) and belowground biomass (BGB) carbon (C) stocks were measured and C sequestration rates calculated as proxy of ecosystem recovery. The soil organic carbon (SOC) stock to 36-cm depth was also quantified during the 2012 survey. To explore potential drivers of spatiotemporal variation of the forest and páramo C stocks they were related to abiotic and biotic variables. Andean forest C stocks were influenced mainly by disturbance history and tree-species composition. Páramo C stocks´ spatial variation were related to the elevation gradient; we found a positive significant trend in páramo AGB-C stocks with elevation, whereas we found a significant negative trend in AGN-C stocks. Likewise, significant temporal changes were found for AGB-C and AGN-C stocks. Net increases in AGB-C stocks were the largest in the Andean forest and páramo, 2.5 Mg C ha⁻¹ year⁻¹ and 1.5 Mg C ha⁻¹ year⁻¹ respectively. Carbon sequestration rates were partly explained by environmental variables. In the Andean forest, plots with low dominance of Baccharis padifolia were observed to present higher AGB-C and lower BGB-C sequestration rates. In the páramo, higher sequestration rates for AGB-C were found at higher elevations and associated with higher levels of growth-forms diversity. Temporal changes in BGB-C stocks on the contrary were non-significant. Our results indicated that terrestrial aboveground C sequestration rates might be an appropriate indicator for assessing Andean forest and páramo recovery after human disturbance.
... Also, in the southwest mountainous areas and the Pearl River Basin of China, the preservation of widely distributed large old trees and remaining natural forest fragments (called fengshui forests) is associated with local customs and beliefs (Hu et al., 2011;Tang et al., 2012Tang et al., , 2013. In addition, the nature worship culture in some parts of Africa and Asia has promoted the persistence of local big trees (Anthwal et al., 2010;Hemp et al., 2017). For example, species such as Ficus religiosa and Ficus benghalensis are protected as sacred trees by local people in Indian subcontinent, as they believe that holy spirits reside in such trees (Anthwal et al., 2010). ...
... Some are important for their edible fruit. Most Meliaceae species are tropical trees with compound leaves, and the family includes the largest-known tree in Africa -an Entandrophragma excelsum Sprague, 81.5 m high on Mt Kilimanjaro (Hemp et al., 2017). ...
... Trees of swamp forest, riverine forest, terra firme rain forest, dry, open, semi-deciduous forest, savanna woodland, and deciduous thicket; from the lowlands to 2220 m (Entandrophragma excelsum in East Africa). In 2016 a specimen of Entandrophragma excelsum 81.5 m high was discovered on Mt Kilimanjaro, and this is Africa's tallest recorded tree (Hemp et al., 2017). ...
... This forest was once widely distributed, but it is nowadays threatened by increasing anthropogenic transformation of the natural environment. As such, the latest remnants are confined to deep gorges, and they include critically endangered species and also the tallest trees of Africa (Hemp, 2006b;Hemp et al., 2017). Further, phylogenetic diversity in the lower montane forest was maximum across all vegetation strata, with the exception of trees, whose phylogenetic diversity peaked in the Ocotea forest, and epiphytes, which showed clustering instead (Table 1a). ...
Accumulating evidence suggests that species sensitivity to climatic change is strongly related to their ecological niches, which are somewhat evolutionary conserved. Insofar as this is true, climate change-driven extinctions may be non-random with respect to phylogeny, and entire branches of the tree of life might be lost. In mountainous regions, where macroecological conditions change abruptly with elevation, evolutionarily lineages may show deep phylogenetic turnover along elevational belts, and such “layering” of the phylogeny may lead to disproportionate losses of phylogenetic diversity. Here, we explored phylogenetic alpha and beta diversity patterns of plant assemblages among six elevational belts at Kilimanjaro (i.e. savanna woodland, lower montane forest, middle-montane Ocotea forest, upper-montane Podocarpus forest, Erica subalpine bushland and Helichrysum alpine scrubland). Specifically, we aimed at determining the degree of elevational turnover of plant evolutionary lineages as a diagnostic tool to assess phylogenetic diversity threats owing to shifting environmental conditions. We found relatively deep phylogenetic discontinuities that roughly matched the main modern vegetation types in East Africa, this is, subalpine-alpine vegetation, montane forests and savannas lowlands. However, the upper-montane Podocarpus forest was phylogenetically closer to subalpine-alpine vegetation than to middle (Ocotea) and lower montane forests, despite all these forest belts constituted a floristically integrated unit. Phylogenetic diversity followed a hump-shape relationship with elevation, with significantly high values in lower montane forest and lower than expected scores in savanna, subalpine and alpine belts. Overall, the phylogenetic layering of Kilimanjaro flora reported here suggests that a disproportionate amount of phylogenetic diversity in mountainous regions might be at risk, although the generality of this pattern is yet to be confirmed. In the particular case of Kilimanjaro, human population growth represents a pervasive threat to montane forest, and particularly to the phylogenetically singular remnants of lower montane forest. Besides, climate-change induced fires in the subalpine belt are causing over-riding shrinkage of the upper-montane Podocarpus forest from the timberline. Should these continuing pressures of global change persist, the montane forests of Kilimanjaro may experience substantial shrinking within the next decades, trapped between the “hammer and the anvil” of climate and land-use change.
... Mg) contained more than three times as much AGB as the species with the next highest amount of AGB, Eschweilera sp2 (86.6 Mg). Although most studies in the Neotropics have found a decrease in AGB at higher elevations (Girardin et al. 2010(Girardin et al. , 2014; but see Unger et al. 2012), recent studies of elevational gradients in Africa and Papua New Guinea have recorded highland forests with AGBs similar to their corresponding lowland forests (Cuni-Sanchez et al. 2017;Hemp et al. 2017;Venter et al. 2017). Our results suggest that large AGB stocks due to the presence of large-statured trees in highland forests are a phenomenon that is not exclusive to the Paleotropics and can occur in Neotropical montane forests as well. ...
... The high yield of some numerically dominant large-statured hardwood species in the highlands appears to be the main explanation for the lack of correlation between species richness and aboveground biomass productivity along the elevational gradient. As discussed above, high AGB in tropical highlands, although widespread in some other systems (Cuni-Sanchez et al. 2017;Hemp et al. 2017;Marshall et al. 2012;Venter et al. 2017), is not typical of all Neotropical mountain forests. The factors allowing for the dominance of large trees in some tropical highland forests may be evolutionary (Culmsee et al. 2010) or ecological (Larjavaara 2014) and clearly warrants additional study. ...
Tropical forests are paramount in regulating the global carbon cycle due to the storage of large amounts of carbon in their biomass. Using repeat censuses of permanent plots located at 15 sites in the Andes Mountains of northwest Colombia, we evaluate: (1) the relationship between aboveground biomass (AGB) stocks, AGB dynamics (mortality, productivity, and net change), and changes in temperature across a ca. 3000-m elevational gradient (≈ 16.1 °C); (2) how AGB mortality and AGB productivity interact to determine net AGB change; and (3) the extent to which either fine-grain (0.04-ha) or coarse-grain (1-ha) processes determine the AGB dynamics of these forests. We did not find a significant relationship between elevation/temperature and biomass stocks. The net AGB sequestered each year by these forests (2.21 ± 0.51 Mg ha⁻¹ year⁻¹), equivalent to approximately 1.09% of initial AGB, was primarily determined by tree growth. Both forest structural properties and global warming influenced AGB mortality and net change. AGB productivity increases with greater inequality of tree sizes, a pattern characteristic of forest patches recovering from disturbances. Overall, we find that global warming is triggering directional changes in species composition by thermophilization via increased tree mortality of species in the lower portions of their thermal ranges and that the inclusion of small-scale forest structural changes can effectively account for endogenous processes such as changes in forest structure. The inclusion of fine-grain processes in assessments of AGB dynamics could provide additional insights about the effects that ongoing climate change has on the functioning of tropical montane forests.
... At local scales, topography and landscape configuration can have significant effects on large trees (Ikin et al., 2015;Lindenmayer et al., 2016;Moga et al., 2016;Thomas et al., 2013). For example, areas around Mount Kilimanjaro, the highest mountain in Africa, support Africa's tallest trees (Hemp et al., 2017). At regional scales, the diversity and density of large old trees is influenced by climate variables (Larjavaara, 2014;Lutz et al., 2009;Slik et al., 2013), soil properties (Venter et al., 2017), and natural disturbances (Lindenmayer and Laurance, 2017). ...
Large old trees are keystone ecological structures that provide vital ecosystem services to humans. However, there are few large-scale empirical studies on patterns of diversity and density of large old trees in human-dominated landscapes. We present the results of the first nationwide study in China to investigate the patterns of diversity and density of large old trees in human-dominated landscapes. We collated data on 682,730 large trees ≥100 years old from 198 Chinese regions to quantify tree species diversity, tree density and maximum tree age patterns. We modelled the effects of natural environmental variables (e.g. climate and topography) and anthropogenic variables (e.g. human population density and city age) on these measures. We found a low density of large old trees across study regions (0.36 trees/km2), and large variation in species richness among regions (ranging from 1 to 232 species). More than 95% of trees were <500 years old. The best fit models showed that: (1) Species diversity (species richness adjusted by region size) was positively associated with mean annual rainfall and city age; (2) Density of clustered trees, which are mostly remnants of ancient woods, was negatively influenced by human population density and rural population (% of total population). In contrast, the density of scattered trees, which are mostly managed by local people, was positively correlated with mean annual rainfall and human population density. To better protect large old trees in cities and other highly-populated areas, conservation policy should protect ancient wood remnants, mitigate the effects environmental change (e.g. habitat fragmentation), minimize the negative effects of human activities (e.g. logging), and mobilize citizens to participate in conservation activities (e.g. watering trees during droughts).
... This could indicate a wet forest vegetation or, since the charcoal content is simultaneously very high, expansion of pyrophytic ferns such as Petridium and Hypolepis covering burned areas(Hemp, 2001(Hemp, , 2002. However, a wet forest vegetation might also be supported by the increase of Araceae, potentially the liana Culcasia falcifolia today restricted to wet submontane gorge and riverine forests of the Kilimanjaro southern slope(Hemp et al., 2017). Finally, plant taxa characteristic of the colline or sub-montane zone (e.g. ...
