Characteristic Tree Species Research Articles

Fire Impacts and Dynamics of Seasonally Dry Tropical Forest of East Java, Indonesia

(1) Background: Seasonally dry tropical forests (SDTFs) are globally important ecosystems which receive less research attention compared to tropical rainforests but are equally under serious threat. The objectives of this paper are to characterize the vegetation structure, diversity and composition of SDTF of Baluran National Park, East Java, Indonesia, and to assess the impact of burning this SDTF and its post-fire recovery. (2) Methods: In the field, we measured floristic composition and dominance at sites with different fire histories in both SDTF and adjacent savannas of Baluran. Remote sensing image analysis was also employed using the MODIS burn area product and various thematic maps. (3) Results: SDTF at Baluran has moderately high tree cover, is less diverse in species than rainforest, and has a prominent vegetative response to fire, especially in the tree layer. The immediate post-fire period in SDTF featured lower densities of tree seedlings and saplings, more grasses and herbs, and lower species richness than older unburned forest. Species composition varied with fire age and vegetation type, with relatively rapid recovery with time since fire evident, although there was some convergence of long-unburned savanna and SDTF sites in terms of floristics. (4) Conclusions: The SDTF of Baluran recovers after fire principally via resprouting but also via seedling regeneration, with structural attributes returning more quickly (<10 years) than floristic composition (>10 years). We did not find consistent evidence of ecosystem transitions between SDTF and savanna despite a small number of long-unburned savanna sites having floristic similarities to dry forest (particularly in terms of characteristic tree species), and we identify the need for more study to determine the degree and mechanisms of forest–savanna transitions in the region, with a future research agenda outlined. Relatively large areas of savanna–dry forest transitions demonstrated from remote sensing analyses were primarily attributed to spread of Acacia nilotica (an alien invasive small tree or shrub) into long-unburned savanna, and its decline in areas where the species is being successfully controlled via burning and cutting. Knowledge of such ecological shifting is important for the ecosystem management, especially in terms of their usage by large mammals.

Species delimitation and genetic structure of two endemic Magnolia species (section Magnolia; Magnoliaceae) in Mexico.

Magnolias are characteristic tree species of the Tropical Montane Cloud Forest (TMCF) in Mexico, an ecosystem that is highly threatened by habitat fragmentation and climate change. In this study, based on DNA sequences from five regions (chloroplast: trnT-trnL, trnK5-matK, trnS-trnG, rpl32-trnL, nuclear: ITS) and seven nuclear microsatellite markers, we aimed to delineate species boundaries between two-endemic species of the TMCF, Magnolia pedrazae and Magnolia schiedeana, and to estimate levels of genetic structure and diversity among populations. Phylogenetic and haplotype network analyses for the chloroplast and ITS regions did not support genetic differentiation as two distinctive species. Results from Bayesian and multivariate cluster analyses based on microsatellite loci showed high genetic differentiation across most populations, which was consistent with a strong and significant pattern of isolation by geographical distance. We found moderate to high levels of population genetic diversity, but it was lower in small populations relative to large populations. Our results suggest a contemporary decrease of genetic connectivity among populations, likely as a consequence of the current decline of suitable TMCF habitat. Managing landscape connectivity among remnant Magnolia populations within protected natural parks and surroundings, and with emphasis of small populations, would be key for the species conservation.

Genetic control of silvicultural traits in Balfourodendron riedelianum (ENGL.) ENGL.

Abstract The Atlantic Forest has very high levels of biodiversity and is considered one of the most important and threatened biomes in the world. Balfourodendron riedelianum is one of the forest’s characteristic tree species that is currently under considered endangered due to timber extraction and forest fragmentation. With the goal of generating information that may contribute to the genetic conservation of B. riedelianum, genetic parameters are estimated for quantitative traits important for silviculture in a provenance and progeny test located in the Experimental Station of Luiz Antônio, São Paulo State, Brazil. The test was established in 1986 and consists of three provenances, from which open-pollinated seeds from 19 seed trees were collected. The following traits were evaluated at 32 years of age: diameter at breast height (DBH), total height (H), stem height (SH), stem straightness (SS), and forking (FOR). The estimates were carried out using the REML/BLUP method. Significant genetic variation among progenies was detected for all traits (except SH) and between provenances for DBH. The coefficient of individual genetic variation (CV gi ) ranged from 2.5 to 9.5 %. The mean heritability among progeny ( h f 2 $h_f^2$ ) was substantial for DBH (0.44) and FOR (0.36), enabling the selection of families with the highest DBH and lowest FOR for population improvement. Genotypic and phenotypic correlations among traits were also found. We conclude that there is genetic variability in the population that can be exploited in future breeding programs and for the genetic conservation of the species.

Climate change versus deforestation: Implications for tree species distribution in the dry forests of southern Ecuador.

Seasonally dry forests in the neotropics are heavily threatened by a combination of human disturbances and climate change; however, the severity of these threats is seldom contrasted. This study aims to quantify and compare the effects of deforestation and climate change on the natural spatial ranges of 17 characteristic tree species of southern Ecuador dry deciduous forests, which are heavily fragmented and support high levels of endemism as part of the Tumbesian ecoregion. We used 660 plant records to generate species distribution models and land-cover data to project species ranges for two time frames: a simulated deforestation scenario from 2008 to 2014 with native forest to anthropogenic land-use conversion, and an extreme climate change scenario (CCSM4.0, RCP 8.5) for 2050, which assumed zero change from human activities. To assess both potential threats, we compared the estimated annual rates of species loss (i.e., range shifts) affecting each species. Deforestation loss for all species averaged approximately 71 km2/year, while potential climate-attributed loss was almost 21 km2/year. Moreover, annual area loss rates due to deforestation were significantly higher than those attributed to climate-change (P < 0.01). However, projections into the future scenario show evidence of diverging displacement patterns, indicating the potential formation of novel ecosystems, which is consistent with other species assemblage predictions as result of climate change. Furthermore, we provide recommendations for management and conservation, prioritizing the most threatened species such as Albizia multiflora, Ceiba trichistandra, and Cochlospermum vitifolium.

A spatially explicit patch model of habitat quality, integrating spatio-structural indicators

Habitat quality – referring to the structure of a habitat – is crucial for the habitat functions and biodiversity-related ecosystem services. Its effective assessment and monitoring is important to meet not only scientific interest, but also practical conservation regulations. We herein present the approach of using a composite indicator of riparian forest quality, both quantitatively (habitat quality index HQI [0|1]) and categorically (quality types QT1…4), integrating a set of spatio-structural indicators derived from earth observation data. We apply the geon concept to aggregate multiple sets of statistically profound and conceptually meaningful indicators to the well-established patch concept. The main difference is that instead of using a priori units (e.g. existing patch delineations), new patches (geons) are derived that directly represent the phenomenon of habitat quality. Patch boundaries correspond to the gradients imposed by the multivariate behavior of the underlying indicators. The approach provides a truly spatially explicit assessment, while at the same time retaining the potential for decomposability on the level of individual indicators. The example of a riparian forest is chosen, as riparian zones are complex ecosystems with a high biodiversity that are highly threatened. In our case, riparian forest habitat quality was assessed using four indicators: (I) tree species composition, (II) horizontal forest structure, (III) vertical forest structure, and (IV) water regime. The distribution of habitat quality (HQI) highlights hot- and cold-spots, where conservation measures may be needed. Cluster analysis reveals four types of patches that are characterized by a specific behavior of the aggregated indicators (QT1=fair composition, QT2=(old growth) forest plantations, QT3=characteristic tree species, QT4=forest gaps). This categorization enables the prevailing or lacking aspects of quality to be determined based on the decomposability of the index. In addition, the resulting patches were evaluated using landscape metrics. The findings achieved on a statistically significant level show that patches with high HQI scores are better connected and form large patches with a characteristic tree species composition. In contrast, areas with low HQI values are characterized by a non-favorable tree species composition and the existence of clear-cut areas or access roads. A comparison with an assessment using a traditional composite indicator approach reveals the sensitivity of the different sets of indicators and assessment methods. The presented habitat quality index can be considered as suitable for the assessment and monitoring of riparian forest quality, supporting spatially explicit conservation measures and the evaluation of applied measures.

Xylem anatomy and calculated hydraulic conductance of four Nothofagus species with contrasting distribution in South-Central Chile

Nothofagus obliqua, N. dombeyi, N. alpina and N. antarctica are characteristic tree species of the temperate forests on the western slopes of the Andes with centres of distribution that differ in their temperature and moisture regimes. We tested branch wood from co-occurring specimens of these species for the inherent differences in xylem anatomy and theoretical hydraulic conductance to evaluate their resistance to drought or frost. The hydraulic conductivity of the xylem was calculated using a modified Hagen–Poiseuille equation and related to wood density. Conduit dimensions were used to predict the water potential that would cause 50 % loss of hydraulic conductivity (Ψ 50). Nothofagus alpina, which mainly grows at sites with low frost frequency, exhibited the largest conduits and the highest mean values for conduit area, fraction of conduit area in the cross-section and hydraulic conductivity, but the lowest wood density. Opposite relationships were found in the plastic N. antarctica, whose xylem seems to be least vulnerable to freezing-induced, but also to drought-induced embolism. Calculated Ψ 50 was highest (least negative) in N. alpina, indicating a relatively high susceptibility to cavitation. The xylem of the thermophilic N. obliqua and of N. dombeyi, which mainly occurs under oceanic climate, but can also survive at sporadically dry and warm sites, is not particularly adapted to periods of drought stress. Across all species, wood density was negatively correlated with the calculated hydraulic conductance. The xylem traits of N. alpina might contribute to its relatively high growth rate and facilitate its spread into forest gaps.

The Effects of Herbivory by a Mega- and Mesoherbivore on Tree Recruitment in Sand Forest, South Africa

Herbivory by megaherbivores on woody vegetation in general is well documented; however studies focusing on the individual browsing effects of both mega- and mesoherbivore species on recruitment are scarce. We determined these effects for elephant Loxodonta africana and nyala Tragelaphus angasii in the critically endangered Sand Forest, which is restricted to east southern Africa, and is conserved mainly in small reserves with high herbivore densities. Replicated experimental treatments (400 m2) in a single forest patch were used to exclude elephant, or both elephant and nyala. In each treatment, all woody individuals were identified to species and number of stems, diameter and height were recorded. Results of changes after two years are presented. Individual tree and stem densities had increased in absence of nyala and elephant. Seedling recruitment (based on height and diameter) was inhibited by nyala, and by elephant and nyala in combination, thereby preventing recruitment into the sapling stage. Neither nyala or elephant significantly reduced sapling densities. Excluding both elephant and nyala in combination enhanced recruitment of woody species, as seedling densities increased, indicating that forest regeneration is impacted by both mega- and mesoherbivores. The Sand Forest tree community approached an inverse J-shaped curve, with the highest abundance in the smaller size classes. However, the larger characteristic tree species in particular, such as Newtonia hildebrandtii, were missing cohorts in the middle size classes. When setting management goals to conserve habitats of key importance, conservation management plans need to consider the total herbivore assemblage present and the resulting browsing effects on vegetation. Especially in Africa, where the broadest suite of megaherbivores still persists, and which is currently dealing with the ‘elephant problem’, the individual effects of different herbivore species on recruitment and dynamics of forests and woodlands are important issues which need conclusive answers.

Isolation and characterization of 12 microsatellite loci for the tropical tree species Shorea maxwelliana and S. laevis (Dipterocarpaceae)

Shorea maxwelliana and S. laevis are characteristic tree species of lowland dipterocarp forests. A set of polymorphic microsatellite markers was isolated for gene flow research, particularly targeting the endangered S. maxwelliana. Micro-satellites were isolated from a microsatellite-enriched library of S. laevis. Primer pairs were designed for 144 loci, 12 of which exhibited high levels of polymorphism in S. maxwelliana, nine of these were also polymorphic for S. laevis. The number of alleles and observed heterozygosity ranged from 3 to 13 and 0.467 to 0.900, respectively. These markers will facilitate the direct estimation of gene flow within and among populations of both species.

Plant regeneration in Stone pine (Pinus pinea L.) by somatic embryogenesis

Regeneration of plants by somatic embryogenesis (SE) was achieved in Stone pine (Pinus pinea), one of the most characteristic tree species of the Mediterranean ecosystem. The initial explants were megagametophytes containing zygotic embryos from five selected half-sib families collected at different dates over 2 consecutive years. Rates of extrusion and initiation of SE differed in both years. However, qualitative patterns were very similar: for most families, the responsive developmental window was from late cleavage polyembryony to early cotyledonary stage. The highest overall mean frequencies of extrusion and SE initiation (7 and 0.9%, respectively, for the five families and the eight 2006 collections) were obtained on a modified Litvay’s medium with 9 μM 2,4-D and 4.5 μM BAP, supplemented with L-glutamine and casein hydrolysate. Families showed large differences in frequencies of SE initiation from year to year. Only seven embryogenic lines were induced in 2005, representing three of the five families tested, whereas 34 lines from all the families were obtained in 2006. Proliferation of embryonal masses (EM) was significantly improved when they were subcultured after dispersing in liquid medium and collected on filter paper disks, instead of being subcultured as small clumps. This effect showed a significant interaction with genotype. Several preconditioning treatments and culture media combinations were tested for embryo development and maturation. The high proliferation rate of EM hampered somatic embryo development. However, up to 42 mature embryos from different lines of three of the five families were obtained, 23 of them germinated and seven converted into somatic seedlings.

Germination of acorns and development of oak seedlings (Quercus robur L.) following flooding

Seeds and seedlings of &lt;i&gt;Quercus robur, &lt;/i&gt; a characteristic tree species of the hardwood floodplain forests along the Rhine River, demonstrated high resistance to complete inundation under controlled conditions. In both experimental trials no significant difference between the different flooding periods (8, 10, and 12 weeks) could be established either for shoot emergence or for the measured morphological growth parameters. Flooding delayed the germination of submerged acorns till the end of inundation. However, seeds of the flooding treatments had significantly higher germination rates than the non-flooded acorns of the control. Likewise, dry weights of seedlings from the flooded seeds were significantly higher than those of seedlings from seeds not flooded. Aboveground growth in the 24-week growth period following flooding was reduced in favour of root development in either trial of the experiment. Restricted leaf development and reduced shoot elongation stalled the growth of young oaks in the seedling trial. The results confirm knowledge from earlier experiments about the flood tolerance of &lt;I&gt;Quercus robu&lt;/I&gt;r seed and seedlings. They also serve to explain why oak seedlings are widespread on the Rhine floodplain after mast years, but gradually disappear in successive years.

Late Holocene vegetation changes and human impact in the Changbai Mountains area, Northeast China

Pollen analytical data from Jinchuan site in the Changbai Mountains, located within the mixed temperate broadleaved forest zone of Northeast China, were used for the reconstruction of vegetation changes and dynamics of human habitation activities in the last 6000 cal. years in the periphery to the Chinese civilization areas of former Manchuria. The beginning of the present type of vegetation dominated by mixed forests with the characteristic tree species Korean pine ( Pinus koraiensis Siebold & Zuccarini) was dated to 3100 cal. BC. Expansion of Korean pine occurred in two steps. The second phase of enhanced expansion of pine along with other coniferous taxa of higher altitudes such as Abies and Picea was dated to around 70 AD. The pattern of Late Holocene spread of coniferous elements ( P. koraiensis, Picea, Abies) and retreat of deciduous oaks was associated with phases of climatic cooling and presumably changes in effective precipitation. The oldest record of habitation processes identified in pollen assemblages from Jinchuan was dated to around 140 AD. The buckwheat ( Fagopyrum esculentum) cultivation was documented since the first half of the 9th century AD. The 18th century immigration of the Chinese population of Han ethnicity was reflected in the fossil archive, due to economic activities of the settlers connected with exploitation of forest resources through cutting of pine trees, protection of walnut stands, and cultivation of Hordeum/ Triticum cereals.

Afforestation of Marginal Lands for Commercial Timber Production and to Meet the Needs of the Rural Community in Swaziland

SUMMARY The forestry industry predominantly depends on privately-owned forests which are foreign-owned, capital intensive and export oriented. The man-made forests cover 102 000 ha, about 6% of the total area of Swaziland. The two largest plantations, Usutu and Peak Timbers, account for 71% of the total plantation area in the Kingdom. Pines and eucalypts are the two main genera planted for pulp, mining timber, sawtimber and droppers. There are nine companies engaged in the processing of wood into various products. The land classified as marginal in Swaziland on account of low rainfall (less than 600 mm) occurs in low-veld, with characteristic tree species like Acacia nigrescens (umkhaya), Acacia tortilis (sitfwetfwe) and a fruit tree Sclerocarya caffra (umganu). In this region, plantation agriculture of citrus trees and sugar cane is only possible under irrigation. In terms of low inherent soil fertility in the highveld, plantation forests are grown on acidic granite and gneiss and also on land whose aver...