Coastal forests of eastern Africa: status, endemism patterns and their potential causes

Eastern African coastal forests are located within the Swahili regional centre of endemism and Swahili-Maputaland regional transition zone in eastern Africa, between 1d? North and 25d? South, and 34—41d? East. Approximately 3167 km² coastal forest remains: 2 km² in Somalia, 660 km² in Kenya, 697 km² in Tanzania, 16 km² in Malawi, 3 km² in Zimbabwe and perhaps 1790 km² in Mozambique. Most forests are small (≤ 20 km²), and all but 19 are under 30 km² in area. Over 80% of coastal forest is located on government land, principally Forest Reserves; only 8.3 km² is found in National Parks (6.2 km² in Kenya (Arabuko-Sokoke), 2 km² in Tanzania (Mafia Island) and tiny patches in Zimbabwe). Coastal forests are an important and highly threatened centre of endemism for plants (c 550 endemic species), mammals (6 species), birds (9 species), reptiles (26 species), frogs (2 species), butterflies (79 species), snails (>86 species) and millipedes (>20 species). Endemic species are concentrated in the forests of the Tana River, between Malindi in Kenya to Tanga in northern Tanzania, and in southern Tanzania. Forests with highest numbers of endemics are: lower Tana River, Arabuko-Sokoke, Shimba Hills (Kenya); lowland East Usambara, Pugu Hills, Matumbi Hills, Rondo and Litipo and other plateaux near Lindi (Tanzania); the Tanzanian offshore island of Pemba; Bazaruto archipelago (Mozambique), and tiny forest remnants of southern Malawi, eastern Zimbabwe and Mozambique. Most coastal forest endemics have a narrow distributional range, often exhibiting single-site endemism or with scattered or disjunct distributional patterns. They are best interpreted as relicts and not the result of recent evolution. Relictualization probably started with the separation of the ancient Pan African rainforest into two parts during the Miocene. The coastal forests are interpreted as a ‘vanishing refuge’ with the endemic species gradually becoming more and more relict (and presumably extinct) due historically to climatic desiccation and more recently to human destruction.     

Vegetation of Pande and Kiono Coastal forests,Tanzania

East African coastal forests possess considerable botanical importance as an area of high plant endemicity, but are little known ecologically. Quantitative botanical sampling techniques have been used to determine vegetation communities in Pande and Kiono coastal forests, Tanzania. Data from 76 quadrats established in six transects (three in each forest) and containing a total of 146 plant species have been classified using TWINSPAN. Seven species-associations and four sample-associations are recognised. Undisturbed forest supports six species-associations which are rich in plant species of restricted distribution, and these differ between the sites studied. Forest heavily disturbed by man supports one species-association composed of more generalist forest species and this association is similar between sites. Variation in vegetation types of undisturbed forests appears to be caused by edaphic conditions, rainfall and degree of exposure. Variation in the vegetation of disturbed forests appears to be controlled by the intensity of forest disturbance. Heavy human disturbance of coastal forests reduces their biodiversity values as plant-diversity and the habitats of rare plant species are lost.     

Elevational distribution of restricted range forest tree taxa in eastern Tanzania

The forests of eastern Tanzania are a globally important biodiversity hotspot. In this study 361 eastern Tanzanian restricted range forest tree taxa were assessed. Of these taxa, 223 occurred in the Eastern Arc, 150 in Coastal forests, 17 in Northern forests and 21 in the Lake Nyasa forests. The majority of the taxa had restricted elevational ranges with 76.3% occurring in no more than two 200 m elevational bands out of a total potential elevation range of 3000 m. The majority of the taxa occupied a small area in the eastern Tanzanian forests, with 201 taxa being only found at a few sites. In determining priority areas for conservation, selection of taxon definitions can have important effects. For example, tree size varies with elevation, so if only large trees are used then site selection will be biased towards particular areas.     

A new species of sunbird from Tanzania

During August 1981 a ten-day visit was paid to Mwanihana Forest Reserve, a rain forest on the eastern scarp of Uzungwa Mountains, eastern Tanzania. Stuart et al. (1981) and Stuart & Jensen (1981) have documented a number of notable range extensions of forest birds from this area, which, until recently, was unexplored by ornithologists. Jensen & Stuart (in press) described four new subspecies of birds and Homewood & Rodgers (in press) described a new subspecies of the Crested Mangabey Cercocebus galeritus from the same locality. Both the physiognomy of the rainforest and the composition of the avifauna suggest strong affinities between Mwanihana Forest, and the forested scarps of other basement block mountains in eastern Tanzania, most notably the Mgurus and the Ulugurus (Stuart, et al. 1981).
On 2 August 1981, while carrying out a mist-netting study in the forest at 1000 m, a male specimen was caught of a very distinct and hitherto undescribed sunbird. On a subsequent visit in September 1981, Miss T. A. van der Willigen, S. N. Stuart and Dr K. M. Howell secured a female specimen of this new species to be described as:     

Biogeographic patterns of the East African coastal forest vertebrate fauna

The archipelago-like coastal forest of East Africa is one of the highest priority ecosystems for biodiversity conservation worldwide. Here we investigate patterns of species richness and biogeographic distribution among birds, mammals and reptiles of these forests, using distribution data obtained from recently published reviews and information collated by the WWF Eastern Africa Coastal Forest Ecoregion Programme. Birds and mammals species were divided into forest specialists and generalists, and forest specialist reptiles into ‘coastal’ and ‘forest’ endemics. The species richness of birds and generalist mammals increased with area, and is probably a result of area-dependent extinction. Only in birds, however, species richness increased with decreasing isolation, suggesting possible isolation-dependent colonization. Forest diversity, associated to altitudinal range, is important for specialist birds and mammals, whose species richness increased with wider altitudinal range. The number of relict coastal endemic and forest endemic reptiles was higher in forests with wider altitudinal ranges and on relatively higher altitude, respectively. Such forests have probably provided a suitable (and perhaps stable) environment for these species through time, thus increasing their persistence. Parsimony analysis of distributions (PAD) and cluster analyses showed geographical distance and general ecological similarity among forests as a determinant factor in bird distribution patterns, with compositional similarity decreasing with increasing inter-forest distance. Compositional similarity patterns of mammals among the forests did not show a strong geographical correspondence or a significant correlation with inter-forest distance, and those of reptiles were not resolved, with very low similarity levels among forest faunas. Our results suggest that the relative importance (and causal relationship) of forest attributes affecting the distribution of the East African coastal forest vertebrate fauna varies depending on life history traits such as dispersal ability and forest specialization. The groupings in PAD are partly congruent with some of the previous classifications of areas of endemism for this region, supporting the ‘naturalness’ of these regions.     

Vertical distribution of fruit‐feeding butterflies with evidence of sex‐specific differences in a Tanzanian forest

Tropical forests accommodate rich species diversity, particularly among insects. Habitat heterogeneity along the vertical gradient extending from the forest understorey to the tree canopy influences diversity. The vertical distribution of forest insects is poorly understood across Africa, most especially eastern Africa. Food‐baited traps were used to study the vertical stratification of adult fruit‐feeding nymphalid butterflies in Mtai Forest Reserve, north‐eastern Tanzania. Traps were located in the forest canopy and understorey. A total of 277 individuals of 24 species were captured. Species composition differed by trap locations: 33% of the species captured were found in both the canopy and understorey strata; however, significantly more species were captured in the understorey (54%) than canopy (13%). Males were significantly more abundant than females and captured in both strata. A greater proportion of females were captured in the understorey than the canopy. The time of day affected capture rates, with more individuals caught in the afternoon; however, there was no association between the time period and the sex of individuals captured in canopy versus understorey locations. Understanding how the sexes of butterflies vary in understorey versus canopy offers new biological insights into the vertical stratification of insects.     

Areas of endemism for passerine birds in the Atlantic forest, South America

Aim To use the method of parsimony analysis of endemism to identify areas of endemism for passerine birds in the Atlantic Forest, South America, and to compare the locations of these areas with areas previously identified for birds as well as other taxa. Location The Atlantic Forest, eastern South America. Methods We analysed a matrix composed of the presence (1) or absence (0) of 140 endemic species in 24 quadrats of 1 × 1 degree distributed along the Atlantic Forest to find the most parsimonious area cladogram. Results Fourteen most parsimonious cladograms were found and then summarized in a single consensus tree. Four areas of endemism were identified: Pernambuco, Central Bahia, Coastal Bahia, and Serra do Mar. Main conclusions Avian areas of endemism in the Atlantic Forest have significant generality, as they are highly nonrandom and congruent with those of other groups of organisms. A first hypothesis about the historical relationships among the four areas of avian endemism in the Atlantic Forest is delineated. There is a basal dichotomy among areas of endemism in the Atlantic Forest, with Pernambuco forming a northern cluster and Coastal Bahia, Central Bahia and Serra do Mar comprising a southern cluster. Within the southern cluster, Central Bahia and Serra do Mar are more closely related to each other than to Coastal Bahia.     

Two new trypanosome species from East African cordylid lizards

Two species ofTrypanosoma are described from East African cordylid lizards.Trypanosoma zonuri n. sp. was found in a disjunct population ofCordylus cordylus on the western slope of Ngorongoro Crater in Arusha Region, northern Tanzania. It has the appearance of a delicate and fragile trypanosome, slightly over half the size of the robust, leaf-likeT. cordyli n. sp. that parasitisesCordylus t. tropidosternum in the Rondo Forest, Lindi Region, southern Tanzania. These are the first trypanosome species recorded from the saurian family Cordylidae in East Africa.     

Floristic similarities between lowland and montane areas of Atlantic Coastal Forest in Northeastern Brazil

Studies undertaken in the Atlantic Coastal Forest have revealed a notable floristic heterogeneity within this vegetation type in NE Brazil. However, there is still a great need for detailed comparisons of the floristic relationships between the various forest types found there. This work presents an analysis of the floristic similarity (at the species level) of these forest as revealed by floristic surveys, with the aim of better understanding and defining this vegetation. Using a binary matrix, grouping, ordering, and TWINSPAN analysis were performed on 742 tree/shrub species listed in 35 different plant surveys. These tree/shrub species were divided by these analysis into two large floristic groups – ombrophilous and semideciduous. The semideciduous group was formed, in general, by forest areas located at altitudes above 700 m (montane forests), and could itself be divided into two subgroups. The first subgroup was located more inland (Pernambuco), while the second subgroup was located nearer the coast (within the states of Pernambuco and Ceará). The ombrophilous group was quite heterogeneous, but could also be divided into two floristic subgroups: i) lowland forests (below 100 m a.s.l) in the states of Pernambuco, Paraíba, and in two areas of Bahia, as well as some montane forests (in Pernambuco, between 640 and 900 m a.s.l.); ii) lowlands forests in the states of Alagoas and Bahia. This latter subgroup is the largest and best defined, and has the highest degree of internal similarity. Nonetheless, it can be further subdivided into two smaller classes, one in Alagoas and the other in Bahia State. The results of this study demonstrate that the concept of the Atlantic Coastal Forest could also include montane ombrophilous forests in Pernambuco State, as these forests form a single floristic unit together with lowland forests in that state. This revised version was published online in June 2006 with corrections to the Cover Date.     

The biogeographical assignment of a west Kenyan rain forest remnant: further evidence from analysis of its reptile fauna

Aim The Kakamega Forest, western Kenya, has been biogeographically assigned to both lowland and montane forest biomes, or has even been considered to be unique. Most frequently it has been linked with the Guineo‐Congolian rain forest block. The present paper aims to test six alternative hypotheses of the zoogeographical relationships between this forest remnant and other African forests using reptiles as a model group. Reptiles are relatively slow dispersers, compared with flying organisms (Aves and Odonata) on which former hypotheses have been based, and may thus result in a more conservative biogeographical analysis. Location Kakamega Forest, Kenya, Sub‐Saharan Africa. Methods The reptile diversity of Kakamega Forest was evaluated by field surveys and data from literature resources. Faunal comparisons of Kakamega Forest with 16 other African forests were conducted by the use of the ‘coefficient of biogeographic resemblance’ using the reptile communities as zoogeographic indicators. Parsimony Analysis of Endemism and Neighbour Joining Analysis of Endemism were used to generate relationship trees based on an occurrence matrix with paup *. Results The analysis clearly supports the hypothesis that the Kakamega Forest is the easternmost fragment of the Guineo‐Congolian rain forest belt, and thus more closely related to the forests of that Central–West African complex than to any forest further east, such as the Kenyan coastal forests. Many Kenyan reptile species occur exclusively in the Kakamega Forest and its associated forest fragments. Main conclusions The Kakamega Forest is the only remnant of the Guineo‐Congolian rain forest in the general area. We assume that the low degree of resemblance identified for the Guineo‐Congolian forest and the East African coastal forest reflect the long history of isolation of the two forest types from each other. Kenyan coastal forests may have been historically connected through forest ‘bridges’ of the southern highlands with the Congo forest belt, allowing reptile species to migrate between them. The probability of a second ‘bridge’ located in the region of southern Tanzanian inselbergs is discussed. Although not particularly rich in reptile species, the area should be considered of high national priority for conservation measures.     

The Chilean coastal range: a vanishing center of biodiversity and endemism in South American temperate rainforests

Temperate forests of southern South America are globally important because of their high level of endemism. I argue here that within southern South America, rainforests of the Chilean Coastal Range should be the primary target for new conservation efforts. Historically, most protected areas in southern South America have been designated to preserve forests above 600 m, mainly in the Andes. However, Coastal Range forests have higher species richness and are under greater threat than Andean forests at similar latitudes. Coastal forests are characterized by the presence of numerous narrow-range endemics, among them two monotypic plant families. The higher frequency of endemic species in Coastal Range forests is attributed to its more stable biogeographic history compared to the Andes, particularly during the glacial events of the Quaternary. Due to the extent of human impact, the remaining fragments of coastal forests are quite distant from one another, and are disconnected from the larger protected areas of Andean forests. Only 439000 ha of Valdivian coastal forest still remain, including some remnants of primary forest. New private or public reserves should be created to protect the last remnants of continuous forest remaining on the Coastal Range of the Valdivian region (40–42° S). A different conservation strategy should be applied north of 40° S, where protected areas are too small and fragments are too scattered to maintain viable populations of most vertebrates. In this latter area, I recommend expanding existing reserves, restoring native forests, and interconnecting remnant forests through a corridor network.     

Understorey plant species richness and composition in metropolitan forest archipelagos: effects of forest size, adjacent land use and distance to the edge

Aim To address the relative role of adjacent land use, distance to forest edge, forest size and their interactions on understorey plant species richness and composition in perimetropolitan forests. Location The metropolitan area of Barcelona, north‐eastern Spain. Methods Twenty sampling sites were distributed in two forest size‐categories: small forest patches (8–90 ha) and large forest areas (> 18,000 ha). For each forest‐size category, five sites were placed adjacent to crops and five sites adjacent to urban areas. Vascular plant species were recorded and human frequentation was scored visually in 210 10 × 10 m plots placed at 10, 50 and 100 m from the forest edge, and additionally at 500 m in large forest areas. Plant species were grouped according to their ecology and rarity categories. A nonmetric multidimensional scaling (NMS) ordination was carried out to detect patterns of variation in species assemblage, and to explore the relationships between these patterns and the richness of the species groups and the studied factors. Factorial anovas were used to test the significance of the studied factors on the richness of species groups. Relationships between human frequentation and the studied variables were assessed through contingency tables. Results Forest‐size category was the main factor affecting synanthropic species (i.e. those thriving in man‐made or man‐disturbed habitats). Synanthropic species richness decreased with increasing distance from the forest edge and, when forests were adjacent to crops, it was higher in small forest patches than in large forest areas. Richness of rare forest species was lower in small forest patches than in large forest areas when forests were adjacent to urban areas. Richness of common forest species and of all forest species together were higher close to the forest edge than far from it when forests were adjacent to urban areas. Forests adjacent to urban areas were more likely to experience high human frequentation, particularly in those plots nearest to the forest edge. Main conclusions Forest‐size category and adjacent land use were the most important factors determining species richness and composition. The preservation of large forests adjacent to crops in peri‐urban areas is recommended, because they are less frequented by humans, are better buffered against the percolation of nonforest species and could favour the persistence of rare forest species.     

Chance versus determinism in canopy gap regeneration in coastal scarp forest in South Africa

Question: Is tree regeneration in canopy gaps characterized by chance or predictable establishment. Location: Coastal scarp forests, Umzimvubu district, Eastern Cape Province, South Africa. Methods: Estimation of richness of gap‐filling species across canopy gaps of different size. Data are compared with regeneration under the canopy. Probability of self‐replacement of gap forming species is calculated. Results: Forest area under natural gap phase was 7.8%, caused mostly by windthrow (54%). The abundance and average size of gaps (87.8 m²) suggests that species diversity may be maintained by gap dynamics. However, only four of 53 gap‐filler species displayed gap size specialization and these were pioneer species. An additional 13 species were more common in larger gaps but there was no gradient in composition of gap‐filler species across gap size (p= 0.61). Probabilities of self‐replacement in a gap were low (< 0.3) and common canopy species were equally abundant in gaps and the understorey. Species composition in gaps showed no pattern of variation, i.e. was unpredictable, which suggests absence of a successional sequence within tree‐fall gaps. There was also only a slight increase in species richness in gaps at intermediate levels of disturbance. Conclusions: Coastal scarp forest appears not to comprise tightly co‐evolved, niche‐differentiated tree species. Unpredictable species composition in gaps may be a chance effect of recruitment limitation of species from the species pool. Chance establishment slows competitive exclusion and may maintain tree diversity in these forests. These data suggest that current levels (≤ 3 gaps per ha) of selective tree harvesting may not cause a reduction in species richness in this forest.     

Resilient forest faunal communities in South Africa: a legacy of palaeoclimatic change and extinction filtering?

Aim To examine the influence of climatic extinction filtering during the last glacial maximum (LGM; c. 18,000 yr bp ) and of the subsequent recolonization of forest faunas on contemporary assemblage composition in southern African forests. Location South Africa, Mozambique, Swaziland, Zimbabwe. Methods Data comprised presence/absence by quarter‐degree grid cell for forest‐dependent and forest‐associated birds, non‐volant mammals and frogs. Twenty‐one forest subregions were assigned to one of three previously identified forest types: Afrotemperate, scarp, and Indian Ocean coastal belt. Differences among forest types were examined through patterns and gradients of species richness and endemism, assemblage similarity, species turnover, and coefficients of species dispersal direction. The influence of contemporary environment on assemblage composition was investigated using partial canonical correspondence analysis. Several alternative biogeographical hypotheses for the recolonization of forest faunas were tested. Results Afrotemperate faunas are relatively species‐poor, have low species turnover, and are unsaturated and infiltrated by generalist species. In northern and central regions, communities are supplemented by recolonization from scarp forest refugia, and among frogs by autochthanous speciation in localized refugia. Scarp faunas are relatively species‐rich, contain many forest‐dependent species, have high species turnover, and overlap with coastal and Afrotemperate faunas. Coastal forests are relatively species‐rich with high species turnover. Main conclusions Afrotemperate communities were affected most by climatic extinction filtering events. Scarp forests were Afrotemperate refugia during the LGM and are a contemporary overlap zone between Afrotemperate and coastal forest. Coastal faunas derive from post‐LGM colonization along the eastern seaboard from tropical East African refugia. The greatest diversity is achieved in scarp and coastal forest faunas in northern KwaZulu–Natal province. This historical centre of diversity has influenced the faunal diversity of nearly all other forests in South Africa. The response of vertebrate taxa to large‐scale, historical processes is dependent on their relative mobility: forest birds best illustrate patterns resulting from post‐glacial faunal dispersal, while among mammals and frogs the legacy of climatic extinction filtering remains stronger.     

Forest and the city: A multivariate analysis of peri-urban forest land cover patterns in 283 European metropolitan areas

Heterogeneous definitions of urban areas and poorly homogenized forest data at the country scale have hampered the comparative assessment of peri-urban forest structure in developed countries. The present study investigates selected landscape characteristics of peri-urban forests in 283 metropolitan areas in Europe controlling for the role of the local context and regional suburbanization trends. Using landscape metrics derived from Urban Atlas maps (a Copernicus/GMES initiative providing a comprehensive land-use assessment of European cities >100,000 inhabitants), significant differences in peri-urban forest structure were detected under five European regions. Specific class metrics (percent forest area, mean patch size, perimeter-to-area ratio) were correlated with urban morphology, landscape and territorial indicators. On average, forest cover is larger in northern and southern European metropolitan areas. Forest patch size increases from western to eastern Europe, with more regular patch shapes in central and eastern regions and less regular shapes in the rest of Europe. Forest class area increases with the area of discontinuous, medium-density settlements. Forest patch size increases with the average patch size of discontinuous dense urban fabric. Our evidence outlines a ‘sprawl model' shaping fringe landscapes characterized by discontinuous urban settlements mixed with fragmented – but possibly well protected – forest patches.     

Major gaps in the distribution of protected areas for threatened and narrow range Afrotropical plants

We investigated the major patterns of plant rarity in sub-Saharan Africa, and looked for the most significant gaps in the reserve network of the region in terms of representing the distribution of threatened and geographically rare plants. Comparisons of the species ranges captured by the network of reserves were made against the proportion of species captured by randomly generated sets of areas and against a theoretical near minimum set of areas that represent all species once. At this scale of analysis, the network of large IUCN-coded reserves (the official ‘protected areas’) performs poorly against random and systematic selection procedures. Significant gaps in the IUCN-coded protected areas are in coastal Gabon/Cameroon, in the various tropical montane forest areas (Cameroon Highlands, Eastern Arc Mountains, Ethiopian Mountains), in lowland coastal eastern Africa, and in the South African Cape. Some of these gaps, for example in the Eastern Arc and eastern African coastal regions, are covered on the ground by a network of Forest Reserves under the management of national Forestry Authorities. The networks of Forest Reserves in Ghana, Nigeria, Cameroon, Uganda, Kenya, Zimbabwe, Zambia and Sierra Leone also fill reservation gaps for rare African plants in these countries. Upgrading the conservation status of some key Forest Reserves, which has been gradually happening for some decades, is proposed as an efficient way to enhance the protected area network of the Afrotropical region for the conservation of rare African plant species.     

Bryophytes of Atewa Forest,Eastern Region,Ghana

Atewa Forest is a biodiverse tropical forest in the Eastern Region of Ghana, highly threatened by illegal mining, farming and hunting activities, and by proposals for industrial-scale bauxite mining. Conservation bodies are active in trying to save the forest and promote its future as a national park. Very little is known about its bryophyte flora, and this short expedition was intended as a first step to remedy that situation. Survey work in March 2014 was targeted mainly at areas thought likely to be bryophyte-rich, notably swamp forest and upland evergreen forest. A total of 164 species was recorded, including about 58 new to Ghana and at least one new species. The importance of Atewa Forest for biodiversity in western Africa is reinforced.     

Evidence for altitudinal migration of forest birds between montane Eastern Arc and lowland forests in East Africa

Burgess, N.D. & Mlingwa, C.O.F. 2000. Evidence for altitudinal migration of forest birds between montane Eastern Arc and lowland forests in East Africa. Ostrich 71 (1 & 2): 184–190.

In this paper we assess the evidence for altitudinal movements of forest birds from the montane forests of the Eastern Arc mountains of East Africa to nearby lowland forest patches. For 34 montane species, including all the Eastern Arc endemics except Banded Green Sunbird Anthreptes rubritorques there is no evidence that they undertake seasonal movements to lower altitudes. An additional 26 montane species, of somewhat wider distribution, have been recorded at low (<500 m) altitudes during the cold/dry season (June to September). Most records of these montane birds at lower altitudes are from sites adjoining montane forest areas, although a few records are from lowland coastal forests at 100–240 km distance from montane areas. Only five of the 26 species (White-chested Alethe Alethe fulleborni, White-starred Forest Robin Pogonocichla stellata, Orange Ground Thrush Zoothera gurneyi, Evergreen Forest Warbler Bradypterus mariae and Barred Long-tailed Cuckoo Cercococcyx montanus) are regularly and commonly reported in the lowlands. They are also found in the lowlands in small numbers during the warm/wet season (October to February), when they may breed. The abundance of at least four, and probably more, of the forest birds with a more widespread distribution in the lowland and montane forests of East Africa declines greatly at high altitudes from the onset of the cold/wet season (February) and only increases again at the start of the warm/wet season (September). It is not known how far these species move as they cannot be easily separated from resident populations in lowland forests, and there are no ringing recoveries in different forests. Altitudinal migration of a proportion of the Eastern Arc avifauna is the most likely explanation for available data, although source-sink metapopulation theories may be helpful to explain the distributions of some species. As the movement of forest birds from the Eastern Arc to the lowland forests does not involve the rare endemics, they are of lower conservation concern, but the presence of montane and lowland forest may be important for the long-term survival of some more widely distributed forest species.     

Biogeographic, environmental, and phylogenetic influences on reproductive traits in subtropical forest trees, South Africa

The distribution of subtropical forests in South Africa is largely a consequence of climatic change during the Quaternary period. We gathered data for 195 canopy tree species from Afrotemperate, scarp, and coastal forests in KwaZulu-Natal, South Africa and assessed patterns in reproductive traits using a comparative phylogenetic approach. The overlap in species composition among the forest types reflected the geographic position and colonisation history of the forests. Despite a high degree of phylogenetic conservatism in reproductive traits, there were differences in their expression among forest types. Afrotemperate forests had a higher incidence of wind pollination, consistent with the steep topography, seasonally dry environment, and limited resource availability in the habitat. Scarp forests had more dry brown fruits with abiotic (explosive and wind) dispersal. Coastal forests had the most species with fleshy fruits, zoochory, and large seeds, all traits that may have facilitated the colonisation or persistence of species in this more recent and dynamic community. Since many suites of traits occur together in diverse phylogenetic lines, they represent adaptive complexes that are influenced by biogeography and environmental conditions. Overall, this study demonstrates that biogeography, environmental factors, and phylogenetic history all influence the distribution of reproductive traits in these forest communities.     

南宁市几个功能区的植被群落结构特征分析

借助数量分析技术分析了广西南宁市植被结构特征。结果表明:(1)主要的绿化乔木有45种,灌木24种。这些植物基本上代表了南宁市绿化植物的主体,但在生物量比重等方面,还是少数种类占主要优势,亟待调整。(2)绿地植被群落的平均胸径与密度成极显著负相关,显示城市植被与自然植被的相似性,而总冠幅盖度与总密度和综合重要值之间成极显著正相关,则显示了城市人工植被的特殊性;(3)绿地面积与胸径成显著正相关,而与密度、冠幅盖度成极显著与近显著的负相关,与重要值成负相关,则显示空间资源对群落特征的影响与自然植被是相似的;(4)聚类分析与主分量分析反映了人工绿地的群体特征,分类结果与功能区划分基本一致,个别样地则不一致;无论格局多样化,还是格调较为均一的绿色景观,均反映了人文美学价值取向对绿地建设的影响;(5)整体上看,南宁市植被结构还存在较大的优化空间。