Environmental drivers of forest biodiversity in temperate mixed forests – A multi-taxon approach

Abstract. Rangkuti AB, Hartini KS, Susilowati A, Rambey R, Harahap MM, Arinah H, Irmayanti L, Pamoengkas P, Indriani F, Peniwidiyanti, Ruhidi A. 2023. Structure, composition and diversity of tree species in Martelu Purba Nature Reserve, North Sumatra, Indonesia. Biodiversitas 24: 78-85. Martelu Purba Nature Reserve is one of the conservation areas in North Sumatra that functions to protect biodiversity. However, there is limited information related to the vegetation community contained in the nature reserve. This study aimed to assess the diversity, structure and composition of tree species in the Martelu Purba Nature Reserve as well as to reveal the conservation status of the species in reserve. The research used the line transect method with a total of 112 observation plots representing various vegetation and environmental conditions. The results showed that there were 39 tree species belonging to 25 families, with 31, 25, 24, and 26 species at the tree, pole, sapling, and seedling stages, respectively. Shorea platyclados and Syzygium cerasiforme were species with the highest Important Value Index (IVI) at the tree and pole stages with 173.04% and 31.01%, respectively, while Gamblea malayana was the most important at the sapling and seedling stages with IVI of 66.43%, and 30.00%, respectively. The Shannon-Wiener diversity index (H') was categorized as low (1.58), the Margalef species richness index (DMg) was high at all growth stages, and the Evenness index (E) was high, indicating that all species were evenly distributed across the research plots. The distribution of tree diameter classes ranged from 20 - 40 cm for trees with the smallest diameter to 81-110 cm for trees with the largest diameter. Based on their conservation status, there were two species with conservation concerns, namely Coffea arabica (Endangered) and Lithocarpus maingayi (Vulnerable). The application of good silvicultural methods needs to be carried out in the context of conservation efforts. One example is through vegetative propagation of species with long flowering periods.

Forest Landscape Restoration and Ecosystem Services in A Luoi District, Thua Thien Hue Province, Vietnam

Tree species composition and diversity were assessed in Agoro-Agu Central Forest Reserve located in Lamwo district-Northern Uganda. Fifteen transects, each 2 km long, were established in the reserve. A procedure of nested quadrats was employed for a systematic sampling of mature trees, saplings and seedlings at 100 m interval(s). Vegetation analysis was conducted in Species Diversity and Richness (SDRiv) software. A total of 100 species of trees belonging to 36 families were recorded. The dominant tree species, also with high Importance Value Indices were Combretum molle G. Don, Albizia grandibracteata Taub. and Vachellia hockii De Wild. Tree species diversity was higher in the intact part (H’=3.46) than in the degraded part (H’=2.86). Lower diversity in the degraded part of the reserve could be due to human disturbance and resulting conducive condition for the early establishment of pioneer species during succession. The occurrence of mixed species with indicator species for both savannah woodlands and Afromontane tree species indicates that Agoro-Agu is an enriched forest for enhanced conservation. Management options that limit continuous degradations such as the enforcement of environmental laws, tree enrichment planting, and ex-situ conservation should be undertaken to restore the status of trees in the degraded part of the reserve.    Key words: Afromontane, biodiversity, East Africa, forest conservation, national forestry authority and species richness.

The effect of management related factors on species richness of epiphytic bryophytes and lichens was studied in managed deciduous-coniferous mixed forests in Western-Hungary. At the stand level, the potential explanatory variables were tree species composition, stand structure, microclimate and light conditions, landscape and historical variables; while at tree level host tree species, tree size and light were studied. Species richness of the two epiphyte groups was positively correlated. Both for lichen and bryophyte plot level richness, the composition and diversity of tree species and the abundance of shrub layer were the most influential positive factors. Besides, for bryophytes the presence of large trees, while for lichens amount and heterogeneity of light were important. Tree level richness was mainly determined by host tree species for both groups. For bryophytes oaks, while for lichens oaks and hornbeam turned out the most favourable hosts. Tree size generally increased tree level species richness, except on pine for bryophytes and on hornbeam for lichens. The key variables for epiphytic diversity of the region were directly influenced by recent forest management; historical and landscape variables were not influential. Forest management oriented to the conservation of epiphytes should focus on: (i) the maintenance of tree species diversity in mixed stands; (ii) increment the proportion of deciduous trees (mainly oaks); (iii) conserving large trees within the stands; (iv) providing the presence of shrub and regeneration layer; (v) creating heterogeneous light conditions. For these purposes tree selection and selective cutting management seem more appropriate than shelterwood system.

Higher tree species richness generally increases the storage of soil organic carbon (SOC). However, less attention is paid to the influence of varied tree species composition on SOC storage. Recently, the perspectives for the stronger persistence of SOC caused by the higher molecular diversity of organic compounds were proposed. Therefore, the influences of tree species richness and composition on the molecular diversity of SOC need to be explored. In this study, an index of the evenness of diverse SOC chemical components was proposed to represent the potential resistance of SOC to decomposition under disturbances. Six natural forest types were selected encompassing a diversity gradient, ranging from cold temperate to tropical forests. We examined the correlations of tree species richness, composition, and functional diversity, with the evenness of SOC chemical components at a molecular level by 13 C nuclear magnetic resonance. Across the range, tree species richness correlated to the evenness of SOC chemical components through tree species composition. The negative correlation of evenness of SOC chemical components with tree species composition, and the positive correlation of evenness of SOC chemical components with tree functional diversity were found. These indicate the larger difference in tree species composition and the lower community functional diversity resulted in the higher heterogeneity of SOC chemical components among the communities. The positive correlation of the evenness of SOC chemical components with the important value of indicator tree species, further revealed the specific tree species contributing to the higher evenness of SOC chemical components in each forest type. Soil fungal and bacterial α-diversity had effect on the evenness of SOC chemical components. These findings suggest that the indicator tree species conservation might be preferrable to simply increasing tree species richness, for enhancing the potential resistance of SOC to decomposition.

The effect of stand structure and tree species composition on epiphytic bryophytes in mixed deciduous–coniferous forests of Western Hungary

ABSTRACTFuelwood is an essential forest product for small-holder farmers in the tropics, but fuelwood harvesting may cause forest degradation and impact ecosystem services. Understanding tree species composition, diversity and biomass changes in forests with active fuelwood collection is important for informing sustainable forest harvesting. In the miombo woodlands of southern Malawi, using forest plots, we investigated: 1) if forests with fuelwood harvesting (n = 50) have different tree, sapling and seedling stem density, species diversity, species composition, and aboveground biomass (AGB) than forests with minimal use (n = 36); and 2) if forest product harvesting pressure and access are predictors of tree stem density, diversity and AGB. We found a significant reduction in tree diversity and AGB but not stem density, and different species composition in areas with fuelwood harvesting compared to reference sites. For saplings, stem density was higher and species composition was different in fuelwood harvesting sites. Seedling Shannon index and Simpson’s diversity were lower in fuelwood harvesting sites. Harvesting pressure and access were predictors of AGB and tree stem density. The reduced AGB and tree species diversity may hinder collection of fuelwood and other forest products, and may reduce ecosystem functioning. Exploring the possibility of forest landscape restoration in the area could be beneficial.

A dinâmica da composição florística de uma área de floresta primária, atingida por fogo, em 1997, na Amazônia brasileira, foi analisada, comparando-se dados de inventários amostrais, realizados nos anos de 1983, 1987, 1989, 1995, 2008 e 2012, em 12 parcelas permanentes de 0,25 hectares, com dados anteriores (14 anos) e posteriores ao incêndio (15 anos). A área de estudo está localizada em uma floresta ombrófila densa, sem histórico de distúrbios antrópicos, na Floresta Nacional do Tapajós, oeste do estado do Pará. As questões deste estudo são as seguintes: (1) Qual o efeito de um primeiro incêndio na composição de espécies arbóreas de uma floresta primária na Amazônia? (2) Existe diferença, na diversidade de espécies arbóreas, antes e após o fogo? Para responder essas questões, (i) foram descritas, quantificadas e comparadas a composição de espécies arbóreas de antes e depois o fogo, (ii) foram quantificadas e comparadas a riqueza e a diversidade de espécies arbóreas de antes e após o fogo. Após 15 anos da ocorrência do incêndio, a floresta não registrou perdas em riqueza e diversidade de espécies arbóreas, indicando boa resiliência ao distúrbio. As alterações pós-fogo na composição florística de uma floresta primária são definidas, principalmente, pela entrada e saída de espécies localmente raras, e as espécies com maior densidade e área basal são responsáveis pela manutenção da estrutura da floresta, destacando-se dentre elas: Rinorea guianensis Aubl. e Protium apiculatum Swart.

Coffee production in Uganda is done on small-scale farms containing a very significant tree component. However, there is little information on how tree species abundance, richness and diversity change in coffee farms as distance from forest changes. The main objectives of this study, therefore, were to assess (a) abundance and (b) diversity of tree species in the coffee production systems in proximity to disturbed and undisturbed forest around Mabira forest, one of Uganda’s Robusta coffee-growing areas. Seventy-nine 0.1 ha plots were established in nine villages close to undisturbed and disturbed forest, and over 5 km from the forest. A total of 875 trees belonging to 63 species were recorded. There was significant similarity in species composition among the three study sites (analysis of similarity R = 0.09, p < 0.01; analysis of variance: F3,12 = 0.353, p = 0.79). Non-metric dimensional scaling supported these findings (stress value = 0.224 at k = 2) and showed that tree species composition in the three proximity categories was very similar. These results demonstrate that tree species composition and diversity is similar in coffee farms regardless of their distance from the nearest natural forest and forest exploitation history.

Biodiversity is declining throughout southern African miombo woodlands due to poor land use practices that are detrimental to soil, vegetation and habitat. We aimed at examining tree and shrub species diversity and distribution in Uapaca kirkiana-dominated woodlands under three land tenure types; forest reserves, customary and leasehold land. The study was conducted at different forest sites within similar agroecological zone in southern Malawi. Study sites were located at a range of altitudes between 900 and 1,200 m a.s.l. Three circular plots each with 32.60 m radius were established at each study site to sample tree and shrub species composition, structure and distribution under three land tenure types. We found that forest reserves had higher species diversity with an average of 16 tree families, 27 genera and 34 species as compared to only 10 tree families, 6 genera and 6 species on customary forest lands. Comparisons of diameter at breast height size class distributions showed that customary land had significantly low numbers of small (5.0–10.0 cm) and very large (≥30 cm) diameter classes suggesting lower levels of regeneration and high rate of anthropogenic activities. The high species diversity and richness in forest reserves and leasehold land indicate high potential for protected lands to restore tree species diversity. It is concluded that levels of human activities as influenced by land tenure type reduce tree species diversity, composition and distribution at the different sites, and this confirms the hypothesis that open access lands are not compatible with conservation of tree and shrub species diversity because of high anthropogenic activities.

Greatly simplified ecosystems are often neglected for biodiversity studies. However, these simplified systems dominate in many regions of the world, and a lack of understanding of what shapes species occurrence in these systems can have consequences for biodiversity and ecosystem services at a massive scale. In Fennoscandia, ~90% of the boreal forest (~21Mha) is structurally simplified with little knowledge of how forest structural elements shape the occurrence and diversity of for example epiphytic lichens in these managed forests. One form of structural simplification is the reduction of the number and frequency of different tree species. As many lichen species have host tree preferences, it is particularly likely that this simplification has a huge effect on the lichen community in managed forests. In a 40–70 years old boreal forest in Sweden, we therefore related the occurrence and richness of all observed epiphytic lichens to the host tree species and beta and gamma lichen diversity at the forest stand level to the stand’s tree species composition and stem diameter. Picea abies hosted the highest lichen richness followed by Pinus sylvestris, Quercus robur, Alnus glutinosa, Betula spp., and Populus tremula. However, P. tremula hosted twice as many uncommon species as any of the other tree species. Stand level beta and gamma diversity was twice as high on stands with four compared to one tree species, and was highest when either coniferous or deciduous trees made up 40–50% of the trees. The stem diameter was positively related to lichen richness at the tree and stand level, but negatively to beta diversity. For biodiversity, these findings imply that leaving a few trees of a different species during forest thinning is unlikely as effective as combining life-boat trees for endangered species with an even tree species mixture.

Greatly simplified ecosystems are often neglected for biodiversity studies. However, these simplified systems dominate in many regions of the world, and a lack of understanding of what shapes species occurrence in these systems can have consequences for biodiversity and ecosystem services at a massive scale. In Fennoscandia, ~90% of the boreal forest (~21Mha) is structurally simplified with little knowledge of how forest structural elements shape the occurrence and diversity of for example epiphytic lichens in these managed forests. One form of structural simplification is the reduction of the number and frequency of different tree species. As many lichen species have host tree preferences, it is particularly likely that this simplification has a huge effect on the lichen community in managed forests. In a 40-70 years old boreal forest in Sweden, we therefore related the occurrence and richness of all observed epiphytic lichens to the host tree species and beta and gamma lichen diversity at the forest stand level to the stand's tree species composition and stem diameter. Picea abies hosted the highest lichen richness followed by Pinus sylvestris, Quercus robur, Alnus glutinosa, Betula spp., and Populus tremula. However, P. tremula hosted twice as many uncommon species as any of the other tree species. Stand level beta and gamma diversity was twice as high on stands with four compared to one tree species, and was highest when either coniferous or deciduous trees made up 40-50% of the trees. The stem diameter was positively related to lichen richness at the tree and stand level, but negatively to beta diversity. For biodiversity, these findings imply that leaving a few trees of a different species during forest thinning is unlikely as effective as combining life-boat trees for endangered species with an even tree species mixture.

&lt;p&gt;Forest soil represents an important resource for mitigating the climate change. Besides, plant composition and diversity and their roles in ecosystem functioning are becoming a central issue in forest &lt;/p&gt;&lt;p&gt;soil organic carbon &lt;/p&gt;(SOC) research. The primary objective of this research is to investigate the effects of tree species diversity and composition on potential of C sequestration of forest soil in Three Gorges area and provide basic information to future research on climate change. Two dominant forest ecosystems were selected: mixed conifer-broadleaf forest (F&lt;sub&gt;m&lt;/sub&gt;) and evergreen broadleaf forest (F&lt;sub&gt;b&lt;/sub&gt;). Then study transects were established and investigated. Soil samples were collected and determined for bulk density, SOC concentration and stock, nitrogen (N) concentration and C:N ratio. The results showed that the statistical differences of SOC concentrations and stocks between F&lt;sub&gt;m&lt;/sub&gt; and F&lt;sub&gt;b&lt;/sub&gt; were caused by tree species composition rather than the tree species diversity. And the most significant differences were found in the first two soil horizons (0–15 cm and 15–30 cm). The average C:N values of four different horizons in F&lt;sub&gt;m&lt;/sub&gt; were decreased with increasing soil depth as well as F&lt;sub&gt;b&lt;/sub&gt;. Not only SOC concentrations but also stocks of the two studied forests were decreased with increasing soil depth. However, F&lt;sub&gt;m&lt;/sub&gt; showed a larger capacity to store SOC with an average stock of 183.50 t/ha than that of F&lt;sub&gt;b&lt;/sub&gt; (100.44 t/ha) in study area. Thus, forest which is composed of conifer and evergreen broadleaf tree species may be the best choice for local afforestation and reforestation aimed at alleviating climate change in Three Gorges region.&lt;p&gt;&lt;/p&gt;

Tree species effects on biogeochemical cycles are well studied, but the interactive effects of tree species in mixtures remain poorly understood. We studied how tree species identity and species diversity affect nutrient cycling in mature forests. In a Belgian platform of 53 forest plots varying in tree species diversity and composition, we sampled the return of carbon, nitrogen and base cations via leaf litterfall and their stocks in the forest floor and topsoil. Tree species identity effects were clear; diversity effects were weak or absent. The leaf litter input from shrub species depended on the composition of the tree canopy and had a higher quality than the litter of the trees. Monocultures of pedunculate oak had the highest input of litter from shrub species; in mixtures with beech, however, this input was disproportionally low. We found indirect effects of tree species diversity on nutrient cycling, via effects of the tree species composition on the abundance and composition of the shrub layer. This is particularly important in forests consisting of tree species with low leaf litter quality, because nutrient cycling may benefit from the presence of shrub species with higher leaf litter quality.

The present study has been undertaken along an altitudinal gradient (950-3500m a.s.l.) in Dudu Forest Range of Udhampur Forest Division, Jammu &amp; Kashmir, India to understand the composition, structure and diversity of tree species along an elevation gradient in the area. Ten forest types characterised by different dominant tree species with subtropical and temperate elements of vegetation have been recognised in the area.Overall average values of diversity indices such as Margalef’s Index (MI); Menhinik Index (MeI); Shannon-Weiner Index (H’) and Simpson Index (D) have been observed to be 1.70, 0.85, 1.66 and 0.61, respectively. The study suggested that distribution and species richness are largely regulated by physiographic and climatic factors along the gradient.