Establishment and early growth of introduced indigenous tree species in typical plantations and shrubland in South China

Unsuccessful colonization by indigenous tree species into established plantations has retarded the succession of artificial plantations to more natural, secondary forests in South China. To understand how to improve colonization by seedlings of indigenous species, we determined how performance of indigenous seedlings is affected by seedling species (the shade-intolerant Castanopsis chinensis, the moderately shade-intolerant Michelia chapensis, and the shade-tolerant Psychotria rubra), the site into which the seedlings were transplanted (a mixed-legume plantation, a eucalyptus plantation, a mixed-native plantation, a mixed-conifer plantation, and a shrubland), and site preparation (removal or retention of understory vegetation and litter). Seedling survival and growth were generally increased by removal of understory vegetation and litter. C. chinensis and M. chapensis grew better in the mixed-legume and mixed-conifer plantations, while P. rubra grew better in mixed-native and mixed-conifer plantations. Responses of the transplanted seedlings to environmental factors were species specific. The effects of light on seedling survival and growth were correlated with the shade tolerance of the species. Soil moisture was important; it was positively correlated with survival but negatively correlated with growth of C. chinensis seedlings. Growth of C. chinensis and M. chapensis was positively correlated with soil potassium, while growth of P. rubra was positively correlated with soil organic matter but negatively correlated with soil hydrolyzed nitrogen. These findings suggest that we should select suitable native species under the different plantations before improvement of plantations. Light and soil moisture are most important environmental factors for the selection of species specific. Site preparation and fertilizer are needed during the improvement of those plantations.     

Factors influencing tree species diversity and Betula alleghaniensis establishment in silvicultural openings

We examined the short-term effects of group-selection harvestingwith seed tree retention on the diversity, abundance and establishmentof tree seedlings in a northern hardwood forest in the UpperPeninsula of Michigan (49 openings, 20 closed canopy referencesites). Three opening sizes were examined – opening radius0.5 x canopy height (267 ± 62 m², n = 16), 0.75 x canopyheight (642 ± 85 m², n = 17) and 1.0 x canopy height(1192 ± 155 m², n = 16) (canopy height = 22 m). A singleyellow birch (Betula alleghaniensis Britt.) seed tree was retainedin the centre of each opening. Tree seedling density was significantlyhigher in the largest group-selection opening than at the closedcanopy reference sites (P < 0.05), the main factor for thiswas the increased proportion of yellow birch, red maple (Acerrubrum L.) and other minor species. Nevertheless, yellow birchwas still a minor component of the developing gap cohort, comprising5.9 per cent of the seedlings and 1.1 per cent of the saplings.Within openings, microsite variables, such as per cent coversof bare soil and coarse woody debris, were the best predictorsof yellow birch occurrence and density. Our results suggestthat microsite limitations and competing vegetation may greatlyreduce the efficacy of openings for ensuring the maintenanceof mid-tolerants.     

High seedling recruitment of indigenous tree species in forest plantations in Kakamega Forest,western Kenya

Tree plantations are often used to compensate for the destruction and conversion of natural forests in the tropics. An important question is whether these plantations allow for the regeneration of indigenous tree species and are expected to transform into more natural forests in the future. To evaluate the potential of differently managed forest types for seedling recruitment of indigenous tree species we studied structural characteristics as well as tree and seedling communities in stands of natural forest, different types of tree plantations and secondary forest in Kakamega Forest, western Kenya. Forest types differed considerably in structural characteristics and tree composition with stands of natural forest significantly differing from all other forest types in vertical foliage height diversity and number of late-successional tree species. By contrast, total seedling species richness and number did not differ among the forest types. Yet, number of seedlings of late-successional species decreased from natural forest and plantations of a mixture of indigenous tree species towards monocultures and secondary forests while number of seedlings of early-successional species increased in the same order. A joint Principal Component Analysis (PCA) corroborated higher similarity among seedling communities than among tree communities. Our results indicate a convergence of recruiting seedling communities in different forest management types suggesting that tree plantations might buffer forest loss to a certain extent and may have the potential to develop into more natural forest over time.     

Factors influencing germination and establishment of Eucalyptus pauciflora near the alpine tree line

Factors affecting seed germination, seedling establishment and growth to reproductive maturity in Eucalyptus pauciflora Sieb. ex Spreng. at the tree line in southeastern Australia were investigated. Timing of germination was determined principally by temperature but could be strongly modified by soil water. Mortality of germinants was heaviest during the first growing season (dependent on soil water) and the first winter (dependent on the depth and duration of snow cover). Neither plant nor soil treatments with insecticide or fungicide had an overriding or consistent effect on germination or seedling establishment. The probability of reaching the sapling stage was greater for planted seedlings than for plants germinated on site, indicating the dependence of survival on accumulated reserves. There was no clear indication of a general decrease in survival with increasing altitude, because of an interplay between elevation and site factors including competing vegetation, snow depth and period of snow cover. Five-year-old saplings planted up to 200 m above the tree line produced reproductive structures and viable seed between the ages of 13 and 18 years. The relevance of the results to an understanding of the location of the present tree line is discussed.     

Seed supply and the regeneration potential for plantations and shrubland in southern China

Assessing the characteristics of seed supply will be vital to better understand the dynamics of forest regeneration. In this study, we surveyed the aboveground vegetation, the seed rain, the seed bank, and natural seedling emergence in four typical 24-year-old plantations (eucalyptus, mixed-native, mixed-legume, and mixed-conifer) and a naturally successioned shrubland in southern China. The dominant species in the understory were similar among the five plant communities. The seed rain and the seed bank were dominated by shrubs and herbs but indigenous tree species were rare. Species that were common to all five-plant communities represented a great proportion of the seeds in the seed rain and seed bank. The seed rain consisted mostly of seeds derived from the local plant community. Seed abundance was greater in the seed bank than in the seed rain, and species richness was greater in the seed bank and in the corresponding plant community than in the seed rain. Species composition similarity between the seed rain, the seed bank, and the aboveground vegetation was low, because the seed rain contained much fewer species, and the seed bank and aboveground vegetation contained many different species, respectively. These findings indicate that both the seed rain and the seed bank play important roles in providing seeds for plant recruitment in the understory, but the seed bank contributes more than the current seed rain to the diversity of recruited plants. The current plant community has little impact on the qualitative composition of the seed rain and seed bank. Based on these data, it appears that succession to the desired zonal, mature forest community is unlikely to result from seeds in the seed rain or seed bank. Lack of seed availability of desired zonal mature forest species is the main bottleneck currently limiting succession in the plantations. Reintroduction of late-successional species could facilitate the desired succession.     

Sowing time and direct seeding success of native tree species for restoring tropical forest ecosystems in northern Thailand

New Forests - Direct seeding (sowing seeds directly into ground) is potentially a cost-effective method of forest restoration that could replace or complement conventional tree planting, under...     

Restoring rainforest species by direct seeding: Tree seedling establishment and growth performance on degraded land in the wet tropics of Australia

The establishment and growth performance of directly seeded rainforest tree species on degraded sites was investigated in the wet tropical region of north east Queensland, Australia. Trials were established at three degraded sites previously covered by rainforest, using two different sowing times (the beginning and end of the wet season), and a range of species having different seed sizes and successional status. The results two years after sowing showed that the effects of sowing time on tree seedling establishment were small despite pronounced differences in cumulative rainfall received by the seedlings. Results suggested that at some sites more serious weed competition might be avoided by sowing later in the season. Although some small seeded early successional species could grow quickly, the establishment of these was found to be significantly negatively affected by the growth of weeds, and in most cases, large seeded species showed more consistent establishment. On the other hand the growth rates of larger seeded species were often rather slow, limiting their contribution to early site capture. Results indicate that direct seeding can be a viable establishment method, but the identity of species to be used, the circumstances under which they should be directly sown and the most appropriate timing of sowing will vary with situations. Species characteristics, including seed size, growth rate potential and light requirement will be important to consider in relation to the probable conditions that will develop for seedlings following germination (particularly in relation to plant competition) with or without post-sowing site management, such as removal of weeds.     

Evaluation of leaf display of evergreen broadleaved tree species and deciduous tree species in warm temperate conifer plantations

We investigated the sapling leaf display in the shade among trees of various leaf lifespans co-occurring under the canopy of a warm-temperate conifer plantation. We measured leaf-area ratio (aLAR) and morphological traits of saplings of evergreen broadleaved tree species and a deciduous tree species. Although we found large interspecific and intraspecific differences in aLAR even among saplings of similar size in the homogeneous light environment, we did not find a consistent trend in aLAR with leaf lifespan among the species. While deciduous trees annually produced a large leaf area, some evergreen broadleaved trees retained their leaves across years and had aLAR values as high as those of deciduous trees. Among leaf-level, shoot-level, and individual-level morphological traits, aLAR was positively correlated with current-year shoots mass per aboveground biomass in deciduous trees, and with the area of old leaves per aboveground mass in evergreen broadleaved trees. Thus, tree-to-tree variation in the degrees of annual shoot production and the accumulation of old leaves were responsible for the interspecific and intraspecific variations in aLAR.     

Biomass and nutrient accumulation in pure and mixed plantations of indigenous tree species grown on poor soils in the humid tropics of Costa Rica

Aboveground biomass and nutrients and soil chemical characteristics were examined in young plantations of four indigenous tree species: Hieronyma alchorneoides, Vochysia ferruginea, Pithecellobium elegans, and Genipa americana, growing in mixed and pure stands at La Selva Biological Station, Costa Rica. Total tree biomass production rates ranged from about 5.2 Mg ha⁻¹ year⁻¹ for G. americana to 10.3 Mg ha⁻¹ year⁻¹ for H. alchorneoides pure stands, and for the species mixture it was about 8.9 Mg ha⁻¹ year⁻¹. Branches and foliage formed 25–35% of total tree biomass but they represented about 50% of total tree nutrients. H. alchorneoides, the four species mixture, and P. elegans had the greatest accumulations of total aboveground nutrients per hectare. The importance of the plantation floor as a nutrient compartment varied temporally. When forest floor litter biomass was at its peak, plantation floor litter N, Ca, and Mg were roughly equal to, or greater than stem nutrients for all species except for P. elegans. For P. elegans, the plantation floor consistently represented a very low proportion of total aboveground nutrients. G. americana and V. ferruginea trees showed 55–60% less biomass accumulation in mixed than in pure stands while H. alchorneoides and P. elegans trees grew 40–50% more rapidly in mixture. P. elegans foliage had 60% lower Ca but higher P concentrations in mixed than in pure stands, and G. americana had higher foliar Mg in mixed than in pure stands. V. ferruginea stands had the highest concentrations of soil Ca, Mg, and organic matter, particularly in the top layers. Relative to pure plantations, soil nutrient concentrations in mixed plantations were intermediate for N, P, and K, but lower for Ca and Mg. The results of this study can be used in the selection of tree species and harvest designs to favor productivity and nutrient conservation.     

Shade tolerance and suitability of tree species for planting in rubber plantations

The rapid increase in rubber monoculture in Xishuangbanna has resulted in extensive damage to its local ecosystem. To decrease the negative effects, the concept of the ecological-economic rubber plantation (EERP) system was proposed. The EERP entails intercropping rubber plants with other economically significant plants, which would not only decrease the ecological impact of the rubber plantation, but also maintain and potentially increase its profitability compared with rubber monocultures. In order to select the appropriate species and intercropping pattern in the EERP system, we compared the photosynthetic parameters of five economically important trees (Swietenia mahagoni, Coffea arabica, Mesua ferrea, Myristica yunnanensis and Paramichelia baillonii) under four irradiance levels. The optimal irradiance intensity of C. arabica and M. yunnanensis was approximately 40%, and these species can be planted in the understory of an 8- to 15-year-old rubber forest. Adult S. mahagoni, M. ferrea and P. baillonii grow taller than the rubber trees, and their seedlings also show superior performance in 100% irradiance than in other irradiances. Thus, in an EERP, these valuable trees could be planted adjacent to rubber plantations but on sites that are economically and environmentally marginal for rubber production.     

Fire sensitivity of broadleaf tree species in plantations of Kurdistan,Iran

To better manage wildfires and plantations in Kurdistan, native tree species commonly used in planting and reviving forests such as Quercus brantii Lindl., Q. infectoria Olivier, Q. libani Olivier, Pistachio atlantica Desf., Fraxinus rotundifolia Vahl, and Robinia pseudoacacia L. were evaluated and compared in terms of fire sensitivity and fire resistance. To determine fire sensitivity, indices such as the fl ammability index, ignition time, fl ame durability, moisture content, carbonized surface, mass reduction, bulk density, as well as dry weight of wood, bark, and leaves were used. The data were subjected to ANOVA. The means obtained, after examining homogeneity or heterogeneity of the variances, were compared using parametric and nonparametric comparison tests. There was a significant difference at the level of 5%. Based on the analysis of these indices, the species could be divided into three groups: species sensitive to fire such as Robinia pseudoacacia, species moderately sensitive to fire such as F. rotundifolia, and species relatively resistant to fire, including Q. brantii, Q. libani, Q. infectoria, and P. atlantica.     

Environmental correlates of distribution of the 25 broad-leaved tree species indigenous to Guangdong Province,China

Twenty-five tree species indigenous to Guangdong Province were chosen in this study to portray their distribution patterns in relation to environmental factors. Both data of species distribution and environmental factors were tabulated based on a digitized map of Guangdong Province gridded at 0.5° latitude × 0.5° longitude. Grid-based diversity was mapped using DMAP, a distribution mapping program, and horizontal patterns were assessed using Kruskal-Wallis tests. The diversity center of the indige- nous tree species under study is located north of 23° N. These tree species exhibit significant latitudinal variation (P = 0.007 4), but no significant longitudinal difference (P = 0.052 2). Non-metric Multidimensional Scaling (NMS) identified five different ecological species groups, while Canonical Correspondence Analysis (CCA) showed the distribution of tree species along each of the five envi- ronmental gradients. An understanding of the environmental correlates of distribution patterns has great implication for the introduc- tion of the indigenous tree species for afforestation.     

Improvement of direct tree seeding with cover crops in afforestation: Microclimate and resource availability induced by vegetation composition

The low cost of direct tree seeding makes it increasingly useful for afforestation. However, the success of the technique is often unpredictable due to a series of different adverse biotic and abiotic factors. A plant cover with low competitive ability towards resources could offer a natural alternative to the herbicides currently used to control weeds. The effects of cover plants on availability of resources and microclimate were studied in a field experiment in the central France during three years. An experiment design crossing three mixtures of tree seeds with four vegetation compositions (a bare soil, flora of the meadow, and two mixtures of cover plants) was established and repeated randomly in three blocks in a meadow. Vegetation composition, tree seedling emergence, light availability, soil water content, and temperatures under each treatment were measured. The vegetation composition of the meadow stayed stable, with grass species dominating. The cover plants sown disappeared rapidly after one or two years. Outcome of direct seeding of trees depended on the vegetation treatment. Bare soil gave the highest emergence rate while meadow vegetation gave the lowest, with the mixture of cover plants being intermediate. Light availability and soil water content were very low under the meadow vegetation but were very high on the bare soil, again with cover plant mixtures being intermediate. This study confirms that a bare soil obtained by herbicide is a secure way to ensure tree seedling establishment in afforestation by direct seeding. However, with the onus currently on reducing herbicide use, the results suggest that sowing a mixture of cover plants could be an acceptable alternative to herbicides. The cover plants could offer protection against frost, scorching temperatures, or the water run-off encountered on bare soil. However, there are also a number of unresolved issues that need be addressed before the cover plants technique can be recommended.     

湖南省珍贵乡土用材树种研究现状与发展对策

阐述了国内外珍贵乡土用材树种的研究现状,分析了湖南省珍贵乡土用材树种研究与发展利用中存在的问题,提出了今后一个时期内湖南省珍贵乡土用材树种研究与发展的建议及对策。     

Factors influencing in vivo and in vitro micrografting of sandalwood (Santalum album L.): an endangered tree species

In vivo micrografting of Santalum album was achieved (50%) by grafting 4- to 5-cm-long scions, collected from a candidate plus tree (CPT) of 50–60 years of age, onto 90-day-old nursery-grown rootstock. Scion size, rootstock age, and scion collection season were found to influence graft success. Grafted plants were incubated under greenhouse conditions for 6–8 weeks during the graft union process. In vitro micrografts were achieved by placing 1- to 2-cm-long scions derived from nodal shoot segments (collected from CPT) onto the hypocotyl of 45-day-old in vitro rootstocks. Use of in vitro grown shoots as a source of scion gave better graft success (60%) than scions collected directly from field-grown trees. In vitro grafting was also influenced by scion size and rootstock age. Under favorable conditions, scions and hypocotyls unite to form complete plants that produced two to four leaves after 6–8 weeks. This is the first report on in vivo and in vitro micrografting of S. album having potential for production of disease-free clonal plants for conservation and improvement targets.     

Evaluation of fuelwood quality of indigenous and exotic tree species of India's semiarid region

The fuelwood potential of indigenous (Acacia nilotica, Azadirachta indica, Casuarina equisetifolia, Dalbergia sissoo, Prosopis cineraria andZizyphus mauritiana) and exotics (Acacia auriculiformis, A. tortilis, Eucalyptus camaldulensis andE. tereticornis) trees were studied. Calorific value variations for components, such as, stump, main stem, treetop, branches, foliage and bark, were determined. Tree components differed highly significantly (P<0.01) among groups (indigenous and exotics) and within species. The calorific means ranged from 18.7 to 20.8 MJ/kg for indigenous tree species and 17.3 to 19.3 MJ/kg for exotics. Besides calorific values, other fuelwood characteristics, such as, density, ash, biomass/ash ratio, moisture and nitrogen content were also studied. It was observed that indigenous tree species are better suited as fuelwood species as they contain high density wood, low ash content and low N percentage. The fuelwood value index (FVI) was found to be high of indigenous tree species and was maximum forCasuarina equisetifolia (2815). The most promising tree species were in the order ofC. equisetifolia, A. nilotica andZ. mauritiana.