Climate change-driven forest fires marginalize the impact of ice cap wasting on Kilimanjaro

The disappearing glaciers of Kilimanjaro are attracting broad interest. Less conspicuous but ecologically far more significant is the associated increase of frequency and intensity of fires on the slopes of Kilimanjaro, which leads to a downward shift of the upper forest line by several hundred meters as a result of a drier (warmer) climate since the last century. In contrast to common belief, global warming does not necessarily cause upward migration of plants and animals. Here, it is shown that on Kilimanjaro the opposite trend is under way, with consequences more harmful than those due to the loss of the showy ice cap of Africa's highest mountain.     

The Banana Forests of Kilimanjaro: Biodiversity and Conservation of the Chagga Homegardens

Natural flora, vegetation, diversity and structure of 62 traditional coffee–banana plantations on Kilimanjaro were investigated and compared with the other vegetation formations on this volcano on basis of over 1400 plots following the method of Braun-Blanquet. The vegetation of the so-called Chagga homegardens belongs floristically to the formation of ruderal vegetation forming two main communities that are determined by altitude. These coffee–banana plantations maintain a high biodiversity with about 520 vascular plant species including over 400 non-cultivated plants. Most species (194) occurring in the Chagga homegardens are forest species, followed by 128 ruderal species, including 41 neophytes. Typical of the agroforestry system of the Chagga homegardens is their multilayered vegetation structure similar to a tropical montane forest with trees, shrubs, lianas, epiphytes and herbs. Beside relicts of the former forest cover, which lost most of their former habitats, there are on the other hand (apophytic) forest species, which were directly or indirectly favoured by the land use of the Chagga people. High demand of wood, the introduction of coffee varieties that are sun-tolerant and low coffee prizes on the world marked endanger this effective and sustainable system.     

Ecology of the Pteridophytes on the Southern Slopes of Mt. Kilimanjaro. Part II: Habitat Selection

Abstract: Based on the evalutation of 957 vegetation plots on the southern slope of Mt. Kilimanjaro, habitat preferences for 140 species of pteridophytes were evaluated. Using the average percentage cover value, and taking into account the pteridophyte flora's composition, life form spectra and its spectra of seasonal growth pattern, eight vegetation formations were recognized. Ferns contributed less than 1 % of the vegetation cover of salt marshes, ruderal vegetation, grasslands and (sub-)alpine heathlands. In contrast, pteridophytes constituted the most important vascular plant group on rocks, where 64 species were found, forming about two-thirds of the vegetation cover. With respect to alpha and beta diversity and fern biomass, luxuriant montane forest was the main habitat for pteridophytes on Mt. Kilimanjaro. Here 130 pteridophyte species (93 % of the whole pteridophyte flora of the study area), on average, contributed 16 % of the total vegetation cover. Epiphytic ferns, tree ferns and filmy ferns had their main distribution between 1900 and 2400 m, in a zone coinciding with the maximum rainfall on Mt. Kilimanjaro's southern slope.
Poikilohydrous species were typical of dry habitats, such as on rocks, in meadows or along roadsides, but they also occurred in the often sun-exposed epiphyte layer in moist montane forests. Deciduous species, which were in many cases fire resistant, had a similar distribution; however, inside the forest belt they were restricted to the lower and upper parts, where fires are a common phenomenon. Evergreen species were the dominant group in swamps, forests and forest clearings.
Compared to other volcanoes in East Africa, Mt. Kilimanjaro is distinctly richer in fern species in general and in filmy ferns, tree ferns and epiphytic ferns in particular, suggesting that the forest belt of the southern slope of Mt. Kilimanjaro is wetter than those of other high mountains in East Africa.     

Postfire Vegetation Recovery in Highland Pine Forests of the Dominican Republic

We surveyed postfire vegetation at five sites at high elevations (> 2000 m) in the Cordillera Central, Dominican Republic. Highlands of the Cordillera Central are dominated by a single pine species, Pinus occidentalis, but plant communities are rich with endemics and conservation and fire management efforts in these systems are ongoing. The burns were 2–7 yr in age and had consumed nearly all shrub crowns. Pines suffered high mortality (> 50%, all sites combined), but shrubs resprouted at high rates (88%, N = 957) after fire. All shrub taxa produced basal resprouts; eight of 11 shrub taxa measured had resprouting rates > 90 percent, while Baccharis myrsinites had the lowest (56%). Most taxa grew to prefire height quickly (within 5–7 yr), with regrowth of stem diameters lagging behind. Patterns and rates of shrub recovery resembled those documented in high elevation shrublands in Costa Rica and Brazil. Pinus occidentalis does not resprout, but larger individuals can survive fire. Survival increases dramatically when trees attain > 13-cm dbh, when bark becomes thick enough to protect cambial tissue. Overall, pines are regenerating much more slowly than shrubs, but seedling establishment varied considerably between sites. Frequent fires may cause a decline in pines and an increase in shrub- or grass-dominated communities. Succession in these high elevation fire-dependent pine forests favors taxa already present in the preburn vegetation, with woody composition changing little after fire, in contrast to lower-elevation cloud forest, where postfire vegetation has been shown to bear little resemblance to mature forest even after several years.     

Vegetation Zonation in a Neotropical Montane Forest: Environment,Disturbance and Ecotones

Gradual changes in vegetation structure and composition are expected to result from continuous environmental change with increasing elevation on mountains. Hence, the occurrence of abrupt or discrete ecotones in vegetation patterns is intriguing and may suggest key controls on community assembly in montane forests. We review tropical montane forest (TMF) zonation patterns focusing on a case study from the Cordillera Central, Hispaniola where a striking discontinuity in forest composition occurs consistently at ～2000 m elevation, with cloud forest below and monodominant pine forest above. We propose that a discontinuity in climatic factors (temperature, humidity) associated with the trade‐wind inversion (TWI) is the primary cause of this and other ecotones in TMFs that occur at a generally consistent elevation. Low humidity, fires and occasional frost above the TWI favor pine over cloud forest species. Fires in the high‐elevation pine forest have repeatedly burned down to the ecotone boundary and extinguished in the cloud forest owing to its low flammability, reinforced by high humidity, cloud immersion and epiphytic bryophyte cover. Small‐scale fire patterns along the ecotone are influenced by topography and where forest structure is impacted by hurricanes and landslides. Analogous patterns are observed worldwide in other TMFs where the TWI is important, high‐elevation fires are frequent, and the flora contains frost‐tolerant species (often of temperate lineage). The response of this and other TMFs to anthropogenic climate change is highly uncertain owing to potentially countervailing effects of different climatic phenomena, including warming temperatures and decreased frost; changes in the TWI, high‐elevation drought or cloudiness; and increased frequency or intensity of hurricanes and El Niño‐Southern Oscillation events.     

Recovery from clearing,cyclone and fire in rain forests of Tonga,South Pacific: Vegetation dynamics 1995–2005

Abstract In late 2001 a category 3 cyclone impacted forest plots that were established in Tonga in 1995, and additionally, one plot was accidentally burned by an escaped land‐clearing fire. Subsequent surveys provide observations of 10 years of forest dynamics in this poorly studied region, and the first reported observations of large interannual variation in juvenile (seedling and sapling) abundance in the western tropical Pacific. The severely disturbed (burned) plot was initially colonized by a non‐native early pioneer, Carica papaya L., but 3.5 years later a native pioneer, Macaranga harveyana (Muell. Arg.) Muell. Arg., was the most abundant tree species. The seedling layer included some long‐lived pioneers and shade‐tolerant species. Two mature forest plots affected only by the cyclone changed very little over a decade. Late‐successional shade‐tolerant species that dominated the overstory were also abundant as seedlings and saplings. This is in contrast with a 30‐ to 40‐year‐old, formerly cultivated, secondary forest plot that still shows no recruitment of late‐successional dominants, in spite of the proximity of remnant forest patches. This study suggests differing pathways of succession following shifting cultivation versus cyclone and fire disturbances in Tonga. Land use legacies appear to have a long‐lasting effect on community composition.     

Comparative landscape genetics of two river frog species occurring at different elevations on Mount Kilimanjaro

Estimating population connectivity and species' abilities to disperse across the landscape is crucial for understanding the long‐term persistence of species in changing environments. Surprisingly, few landscape genetic studies focused on tropical regions despite the alarming extinction rates within these ecosystems. Here, we compared the influence of landscape features on the distribution of genetic variation of an Afromontane frog, Amietia wittei, with that of its more broadly distributed lowland congener, Amietia angolensis, on Mt. Kilimanjaro, Tanzania. We predicted high gene flow in the montane species with movements enhanced through terrestrial habitats of the continuous rainforest. In contrast, dispersal might be restricted to aquatic corridors and reduced by anthropogenic disturbance in the lowland species. We found high gene flow in A. wittei relative to other montane amphibians. Nonetheless, gene flow was lower than in the lowland species which showed little population structure. Least‐cost path analysis suggested that dispersal is facilitated by stream networks in both species, but different landscape features were identified to influence connectivity among populations. Contrary to a previous study, gene flow in the lowland species was negatively correlated with the presence of human settlements. Also, genetic subdivision in A. wittei did not coincide with specific physical barriers as in other landscape genetic studies, suggesting that factors other than topography may contribute to population divergence. Overall, these results highlight the importance of a comparative landscape genetic approach for assessing the influence of the landscape matrix on population connectivity, particularly because nonintuitive results can alter the course of conservation and management.     

人类活动干扰下区域植被动态变化——以西双版纳为例

云南省西双版纳地区是我国典型热带雨林区,随着社会经济发展,人类活动对区域植被格局与动态产生强烈影响。利用NDVI变化趋势分析、土地利用转移矩阵和基于MODIS数据的干扰指数（MGDI）3种方法,分析了2000-2010年人类活动干扰下研究区植被动态变化,构建了人类活动干扰指数,并利用冗余分析的方法,分析其与植被特征的相关性。结果表明：通过NDVI变化趋势得出,2000-2010年间,研究区植被覆盖度总体较高,植被变化趋势的斜率均大于0,说明植被总体趋于改善;基于土地利用转移矩阵结果表明,植被变化主要发生在常绿阔叶林、常绿针叶林转变为乔木园地、灌木园地、人工园地或居住用地;基于MODIS影像结果得出,西双版纳地区MGDI分布很不均匀,且2000-2010不同土地覆被类型MGDI相差不大。构建的人类活动干扰指数结果显示人类干扰强度由中心向边缘呈递增趋势,呈分散分布,这与人类活动的分布规模和强度相关。通过冗余分析可知,NDVI与人类活动相关性较大,MGDI与人类活动相关性不大。总体上来说,上述3种方法能够从不同侧面反映出人类活动干扰下植被长时间的变化趋势。因此,对于西双版纳地区,局地的人类活动特别是旅游、基础设施建设、农业活动等对热带雨林自然生态系统的干扰不容忽视。     

Diversity and composition of Arctiidae moth ensembles along a successional gradient in the Ecuadorian Andes

Andean montane rain forests are among the most species‐rich terrestrial habitats. Little is known about their insect communities and how these respond to anthropogenic habitat alteration. We investigated exceptionally speciose ensembles of nocturnal tiger moths (Arctiidae) at 15 anthropogenically disturbed sites, which together depict a gradient of forest recovery and six closed‐forest understorey sites in southern Ecuador. At weak light traps we sampled 9211 arctiids, representing 287 species. Arctiid abundance and diversity were highest at advanced succession sites, where secondary scrub or young forest had re‐established, followed by early succession sites, and were lowest, but still high, in mature forest understorey. The proportion of rare species showed the reverse pattern. We ordinated moth samples by non‐metric multidimensional scaling using the chord‐normalized expected species shared index (CNESS) index at various levels of the sample size parameter m. A distinct segregation of arctiid ensembles at succession sites from those in mature forest consistently emerged only at high m‐values. Segregation between ensembles of early vs. late succession stages was also clear at high m values only, and was rather weak. Rare species were responsible for much of the faunal difference along the succession gradient, whereas many common arctiid species occurred in all sites. Matrix correlation tests as well as exploration of relationships between ordination axes and environmental variables revealed the degree of habitat openness, and to a lesser extent, elevation, as best predictors of faunal dissimilarity. Faunal differences were not related to geographical distances between sampling sites. Our results suggest that many of the more common tiger moths of Neotropical montane forests have a substantial recolonization potential at the small spatial scale of our study and accordingly occur also in landscape mosaics surrounding nature reserves. These species contribute to the unexpectedly high diversity of arctiid ensembles at disturbed sites, whereas the proportion of rare species declines outside mature forest.     

Effects of Selective Vegetation Thinning on Seed Removal in Secondary Forest Succession1

Seed removal was assessed for two tree species in three forest types: (1) secondary forest with and (2) without selective vegetation thinning, and (3) mature forest. Selective vegetation thinning meant the removal of all stems ≤3 cm in diameter of secondary‐forest species and was intended as a management technique to accelerate succession toward mature forest. Thinning did not have an effect on seed removal. One of the species showed lower seed removal in mature forest compared to secondary forest.     

Geological History,Flora, and Vegetation of Xishuangbanna,Southern Yunnan,China1

Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical Southeast (SE) Asia to subtropical East Asia, and is at the junction of the Indian and Burmese plates of Gondwana and the Eurasian plate of Laurasia. The flora of the region consists of a recorded 3336 native seed plant species, belonging to 1140 genera in 197 families, among which 83.5 percent are tropical genera and 32.8 percent are endemic to tropical Asia, suggesting a strong affinity to tropical Asian flora. The vegetation of Xishuangbanna is organized into four forest types: tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad‐leaved forest, and tropical monsoon forest. The tropical rain forest in Xishuangbanna has the same floristic composition of families and genera as some lowland equatorial rain forests in SE Asia, and is dominated (with a few exceptions) by the same families both in species richness and stem dominance. The exceptions include some deciduous trees in the canopy layer, fewer megaphanerophytes and epiphytes, and a higher abundance of lianas and microphyllic plants. We consider the tropical rain forest of Xishuangbanna as a type of tropical Asian rain forest, based on their conspicuous similarities in ecological and floristic characteristics.     

Gap-phase regeneration in a tropical montane forest: the effects of gap structure and bamboo species

To study the influence of gap structure and bamboo species on the regrowth of montane Atlantic forest, colonization by plants was characterized in 30 treefall gaps (30.3–500.5 m²). The study was conducted at Santa Virgínia (45°30 W, 23°17 S), a 4970-ha reserve of Atlantic montane forest in southeastern Brazil. Area covered by bamboos ranged from 0% to 100% of gap area. Average height of surrounding canopies ranged from 12 to 30 m. As gap are covered by bamboo and average height of surrounding canopies increased, both density and richness of pioneer woody species decreased. Density and richness of shade-tolerant species were negatively influenced by gap area. Low-light-demanding species of Miconia, Leandra and Rapanea accounted for the majority of both pioneer species and individuals sampled, whereas high-light demanding pioneers of Cecropia, Alchornea and Tibouchina were poorly represented. We suggest that in the Atlantic montane forest bamboo species compete for gaps, excluding other light-demanding pioneers. This results in an overall reduction of pioneer species richness in the Atlantic forest.     

Biophysical analysis of afromontane forest community types at Mount Kasigau,Kenya

This study examines how biophysical site conditions differ in relation to the distribution of forest community types at Mount Kasigau, Kenya, in the Eastern Arc. Topographic measures of elevation, slope, curvature and aspect were derived from a 30‐m DEM and temperature and moisture conditions collected from 19 field data loggers for June 2011–2012 measured seasonal change along the steep elevational gradient (1000 m) from bushland to evergreen forest. Nonparametric statistical analyses then compared topographic and climatic conditions among eight ecologically classified forest types. Steep lapse rates in temperature and available moisture support abrupt changes in canopy physiognomy, but dew points declined with elevation. The Kruskal–Wallis test showed significant differences in the elevation, slope, temperature, dew point and relative humidity conditions among the eight forest types. These biophysical conditions are more discrete for Acacia‐Commiphora bushland and cloud forest but not significantly different between riverine forest, lower montane woodlands I and II and Euphorbia quinquecostata woodland, and between semi‐evergreen woodland and evergreen forest. Biophysical conditions and their influence on the distribution of forest types across a heterogeneous mountain landscape are important to understand and monitor in this unpredictably changing tropical seasonal climate.     

Forest succession in Kibale National Park, Uganda: implications for forest restoration and management

Forest succession was studied in four plots in former grasslands at the Ngogo study area in Kibale National Park, Uganda. The plots were located in areas that had been protected from fire for 0.58, 25, 9 and ≈30 years for plots 1, 2, 3 and 4, respectively. Species richness reflected the length of time that the plot had been protected from fire; it was highest in plot 4 and lowest in plot 1. Species density, stem density and basal area were all highest in plot 4 and lowest in plot 1. The species densities of plots 2 and 3 were not different. Similarly, plots 2 and 4 did not differ with regard to stem density or basal area. Animal seed dispersers played a vital role in the colonization of grasslands by forest tree species.     

Vegetation Recovery 16 Years after Feral Pig Removal from a Wet Hawaiian Forest

Nonnative ungulates can alter the structure and function of forest ecosystems. Feral pigs in particular pose a substantial threat to native plant communities throughout their global range. Hawaiian forests are exceptionally vulnerable to feral pig activity because native vegetation evolved in the absence of large mammalian herbivores. A common approach for conserving and restoring forests in Hawaii is fencing and removal of feral pigs. The extent of native plant community recovery and nonnative plant invasion following pig removal, however, is largely unknown. Our objective was to quantify changes in native and nonnative understory vegetation over a 16 yr period in adjacent fenced (pig‐free) vs. unfenced (pig‐present) Hawaiian montane wet forest. Native and nonnative understory vegetation responded strongly to feral pig removal. Density of native woody plants rooted in mineral soil increased sixfold in pig‐free sites over 16 yr, whereas establishment was almost exclusively restricted to epiphytes in pig‐present sites. Stem density of young tree ferns increased significantly (51.2%) in pig‐free, but not pig‐present sites. Herbaceous cover decreased over time in pig‐present sites (67.9%). In both treatments, number of species remained constant and native woody plant establishment was limited to commonly occurring species. The nonnative invasive shrub, Psidium cattleianum, responded positively to release from pig disturbance with a fivefold increase in density in pig‐free sites. These results suggest that while common native understory plants recover within 16 yr of pig removal, control of nonnative plants and outplanting of rarer native species are necessary components of sustainable conservation and restoration efforts in these forests.     

Inferring speciation history in the Andes with reduced‐representation sequence data: an example in the bay‐backed antpittas (Aves; Grallariidae; Grallaria hypoleuca s. l.)

In the Andes, humid‐forest organisms frequently exhibit pronounced genetic structure and geographic variation in phenotype, often coincident with physical barriers to dispersal. However, phylogenetic relationships of clades have often been difficult to resolve due to short internodes. Consequently, even in taxa with well‐defined genetic structure, the temporal and geographic sequences of dispersal and vicariance events that led to this differentiation have remained opaque, hindering efforts to test the association between diversification and earth history and to understand the assembly of species‐rich communities on Andean slopes. Here, we use mitochondrial DNA and thousands of short‐read sequences generated with genotyping by sequencing (GBS) to examine the geographic history of speciation in a lineage of passerine birds found in the humid forest of the Andes, the ‘bay‐backed’ antpitta complex (Grallaria hypoleuca s. l). Mitochondrial DNA genealogies documented genetic structure among clade but were poorly resolved at nodes relevant for biogeographic inference. By contrast, relationships inferred from GBS loci were highly resolved and suggested a biogeographic history in which the ancestor originated in the northern Andes and dispersed south. Our results are consistent with a scenario of vicariant speciation wherein the range of a widespread ancestor was fragmented as a result of geologic or climatic change, rather than a stepping‐stone series of dispersal events across pre‐existing barriers. However, our study also highlights challenges of distinguishing dispersal‐mediated speciation from static vicariance. Our results further demonstrate the substantial evolutionary timescale over which the diverse biota of the Andes was assembled.     

Population structure of montane bamboo and causes of its decline in Echuya Central Forest Reserve, South West Uganda

Montane bamboo is of immense importance to the people living adjacent to Echuya Forest Reserve. It is used for building poles, bean-staking and basket weaving. The bamboo in Uganda occurs mostly in protected areas. Over the past 50 years, the bamboo forest cover has been declining. This study aimed at determining bamboo density and distribution and the possible causes of its decline within Echuya. We used exploratory inventories, bamboo assessment plots and village interviews to determine bamboo population structure and possible causes of its decline in Echuya. Bamboo forest decline in Echuya may be blamed on several factors that interplay together. Poor harvest methods especially during the clear cutting of bamboo for bean-stakes and stakes for house wefts seems to be the remote cause of the bamboo forest decline. Other causes for the bamboo forest decline are damages caused by insect borers and climber loads on the bamboo stems. The remote causes have been exacerbated by the invasion of secondary forest tree species such as Macaranga kilimandscharica that have slowly taken over areas previously occupied by the bamboo forest. Seventy per cent of the local people interviewed agree that over-harvesting of bamboo is the major reason for its decline.     

Phosphorus Fertilization Increases the Abundance and Nitrogenase Activity of the Cyanolichen Pseudocyphellaria crocata in Hawaiian Montane Forests

Nitrogen-fixing epiphytes (especially lichens with a cyanobacterial symbiont—cyanolichens) have the potential to contribute significant amounts of nitrogen (N) to montane tropical forests, which are typically low in N—but the factors controlling the abundance and distribution of epiphytic cyanolichens are poorly understood. In long-term fertilization experiments in montane forests on a 4.l million-yr-old Oxisol on the island of Kauà'i and on a 152-yr-old lava flow on the island of Hawai'i, the epiphytic cyanolichen Pseudocyphellaria crocata increased significantly in abundance in canopies of host trees fertilized with phosphorus (P). There was no response to fertilization with N or other essential elements. Nitrogen-fixation rates were also elevated in lichens in P-fertilized plots at both sites. Phosphorus supply to host trees may be an important factor controlling N inputs to montane tropical forests by N-fixing epiphytes.