Browsing by Subject "PLANTATIONS"

Sort by: Order: Results:

Now showing items 1-9 of 9
  • Xia, Zhichao; Yu, Lei; He, Yue; Korpelainen, Helena; Li, Chunyang (2019)
    Tree performance in mixed-species forest plantations is ultimately the net result of positive and negative interactions among species. Despite increasing knowledge of interspecific interactions, relatively little is known about the chemical mechanisms mediating such interactions. We constructed mixed planting systems with two species including Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) and broadleaf species Cinnamomum camphora L. Presl, Elaeocarpus decipiens Hemsl, Liquidambar formosana Hance, or Michelia macclurei Dandy. Based on a series of manipulative experiments, we investigated the performance of Chinese fir and analyzed root placement patterns and the composition of main soil microbial groups. The broadleaf trees influenced the growth of Chinese fir roots more than the growth of shoots. Furthermore, C. camphora roots released allelochemicals into the soil environment, resulting in growth inhibition of Chinese fir and changes in main soil microbial groups. However, when grown with E. decipiens and M. macclurei, the growth of Chinese fir was consistently promoted. It responded by enhancing its root growth and altering root behavior, resulting in a shift from growth inhibition to chemical facilitation. These positive inter-specific interactions also stimulated changes in the composition of soil microbes. Complementary experiments indicated that non-toxic signaling molecules in the root exudates of E. decipiens and M. macclurei may be responsible for mediating positive root-root interactions and regulating the composition of main soil microbial groups. Thus, our study demonstrated that broadleaf species chemically mediate the growth of Chinese fir through root exudates. Such a novel mechanism offers many implications and applications for reforestation programs undertaken to rehabilitate forest plantations that suffer from declining productivity related to densely planted monocultures.
  • Danquah, Jones Abrefa; Appiah, Mark; Ari, Pappinen (2011)
  • Guo, Qingxue; Song, Haifeng; Kang, Jieyu; Korpelainen, Helena; Li, Chunyang (2018)
    Knowledge of how competition and facilitation affect photosynthetic traits and nitrogen metabolism contributes to understanding of plant-plant interaction mechanisms. We transplanted two larch species, Larix kaempferi and L. olgensis, to establish intra- and interspecific interaction experiments under different types of soil. Experiment 1: Two different soil types were selected, one from a c. twenty years old L. kaempferi plantation (named larch soil) and another from a secondary natural forest (named mixed forest soil). The experiment included three types of plant interactions (L kaempferi + L. kaempferi, L. olgensis + L. olgensis, and L. kaempferi + L. olgensis) and two soil types. Experiment 2: N fertilization was applied to larch soil. The experiment included the same three types of plant interactions as in Experiment 1 and two N treatments. The growth of L kaempferi was negatively affected by larch soil and accelerated by N fertilization, particularly under interspecific interaction. The effects of soil type combined with plant-plant interactions or N fertilization influenced the chlorophyll pigment content, net photosynthetic rate (Pn), photosynthetic N use efficiency (PNUE) and total non-structural carbohydrates of leaves (TNC). CM a/Chl b (ratio of chlorophyll a to chlorophyll b) was higher when the growth of L. kaempferi was facilitated by the presence of L olgensis in mixed forest soil. However, the ratio significantly declined when L. kaempferi confronted strong competition from L. olgensis in larch soil without N fertilization. Under N fertilization in larch soil, Chl a/Chl b of L. olgensis significantly increased by the presence of L. kaempferi. Plant-plant interactions and soil types affected the number of chloroplasts, especially in L. kaempferi, which had a greater number of chloroplasts under interspecific interactions than in monoculture when growing in mixed forest soil. L. olgensis enhanced its ability to absorb N-NO3- under interspecific interactions in larch N- soil, while L. kaempferi enhanced its ability to absorb N-NH4+ under interspecific competition in mixed forest soil. Competition or facilitation modified the photosynthetic traits and nitrogen metabolism depending on the type of soil. Differences in these physiological processes contribute to divergent performance among individuals growing under interspecific or intraspecific competition, or in isolation.
  • Assmuth, Aino; Ramo, Janne; Tahvonen, Olli (2018)
    We study the economics of carbon storage using a model that includes forest size structure and determines the choice between rotation forestry and continuous cover forestry. Optimal harvests may rely solely on thinning, implying infinite rotation and continuous cover forestry, or both thinning and clearcuts, implying finite rotation periods. Given several carbon prices and interest rates, we optimize the timing and intensity of thinnings along with the choice of management regime. In addition to the carbon storage in living trees, we include the carbon dynamics of dead trees and timber products. Forest growth is specified by an empirically validated transition matrix model for Norway spruce (Picea abies (L.) Karst.). The optimization problem is solved in its general dynamic form by applying bilevel optimization with gradient-based interior point methods and a genetic algorithm. Carbon pricing postpones thinnings, increases stand density by directing harvests to larger trees, and typically yields a regime shift from rotation forestry to continuous cover forestry. In continuous cover solutions, the steady-state harvesting interval and the diameter distribution of standing and harvested trees are sensitive to carbon price, implying that carbon pricing increases the sawlog ratio of timber yields. Additionally, we obtain relatively inexpensive stand-level marginal costs of carbon storage.
  • Kansanen, Kasper; Vauhkonen, Jari; Lahivaara, Timo; Seppanen, Aku; Maltamo, Matti; Mehtatalo, Lauri (2019)
    Errors in individual tree detection and delineation affect diameter distribution predictions based on crown attributes extracted from the detected trees. We develop a methodology for circumventing these problems. The method is based on matching cumulative distribution functions of field measured tree diameter distributions and crown radii distributions extracted from airborne laser scanning data through individual tree detection presented by Vauhkonen and Mehtatalo (2015). In this study, empirical distribution functions and a monotonic, nonlinear model curve are introduced. Tree crown radius distribution produced by individual tree detection is corrected by a method taking into account that all trees cannot be detected. The evaluation is based on the ability of the developed model sequence to predict quadratic mean diameter and total basal area. The studied data consists of 36 field plots in a typical boreal managed forest area in eastern Finland. The suggested enhancements to the model sequence produce improved results in most of the test cases. Most notably, in leaveone-out cross-validation experiments the modified models improve RMSE of basal area 13% in the full data and RMSE of quadratic mean diameter and basal area 69% and 11%, respectively, in pure pine plots. Better modeling of the crown radius distribution and improved matching between crown radii and stem diameters add the operational premises of the full distribution matching.
  • Koskikala, Joni; Kukkonen, Markus; Käyhkö, Niina (2020)
    Global terrestrial biodiversity hotspots (GBH) represent areas featuring exceptional concentrations of endemism and habitat loss in the world. Unfortunately, geospatial data of natural habitats of the GBHs are often outdated, imprecise, and coarse, and need updating for improved management and protection actions. Recent developments in satellite image availability, combined with enhanced machine learning algorithms and computing capacity, enable cost-efficient updating of geospatial information of these already severely fragmented habitats. This study aimed to develop a more accurate method for mapping closed canopy evergreen natural forest (CCEF) of the Eastern Arc Mountains (EAM) ecoregion in Tanzania and Kenya, and to update the knowledge on its spatial extent, level of fragmentation, and conservation status. We tested 1023 model possibilities stemming from a combination of Sentinel-1 (S1) and Sentinel-2 (S2) satellite imagery, spatial texture of S1 and S2, seasonality derived from Landsat-8 time series, and topographic information, using random forest modelling approach. We compared the best CCEF model with existing spatial forest products from the EAM through independent accuracy assessment. Finally, the CCEF model was used to estimate the fragmentation and conservation coverage of the EAM. The CCEF model has moderate accuracy measured in True Skill Statistic (0.57), and it clearly outperforms other similar products from the region. Based on this model, there are about 296,000 ha of Eastern Arc Forests (EAF) left. Furthermore, acknowledging small forest fragments (1-10 ha) implies that the EAFs are more fragmented than previously considered. Currently, the official protection of EAFs is disproportionally targeting well-studied mountain blocks, while less known areas and small fragments are underrepresented in the protected area network. Thus, the generated CCEF model should be used to design updates and more informed and detailed conservation allocation plans to balance this situation. The results highlight that spatial texture of S2, seasonality, and topography are the most important variables describing the EAFs, while spatial texture of S1 increases the model performance slightly. All in all, our work demonstrates that recent developments in Earth observation allows significant enhancements in mapping, which should be utilized in areas with outstanding biodiversity values for better forest and conservation planning.
  • Arvola, Anne; Malkamäki, Arttu; Penttilä, Juho; Toppinen, Anne (2019)
    In the rapidly growing Tanzanian economy, increasing demand for timber and limited wood supply from industrial plantations and natural forests have opened a new livelihood opportunity for smallholder farmers in the Southern Highlands of Tanzania, which is undergoing a tree-growing boom. In the absence of support services, research and statistics, the magnitude of the phenomena has remained unclear, along with the farmers’ capability to meet market demands, access the markets, and negotiate prices. Primary qualitative data were collected to clarify the role of smallholder tree growers in the forest transition process and wood value chain using 60 semi-structured tree farmer interviews in four villages, and through interviews of timber buyers and processors. The findings indicate that the strong market demand has created dual markets, where higher quality industrial plantations mainly supply larger industries, whereas micro and small enterprises source wood from lower quality smallholder plantations. While the markets’ quality criteria are expected to tighten, capacity building is needed to improve smallholder wood quality to ensure the long-run tree-growing livelihood and competitiveness of small-scale producers in the markets.
  • Hohenthal, Johanna Maaria; Räsänen, Marinka; Minoia, Paola (2018)
    Environmental resource management policies worldwide have long insisted on the need to involve local communities and their diverse ecological knowledges in management planning and decision-making. In SubSaharan post-colonial countries, however, formal resource management is still largely dominated by bureaucratic governance regimes that date back to colonial power structures and that rely mainly on professional or formal knowledge. In this study, we use a political ecology approach to analyze disputes over eucalyptus plantations in the Taita Hills, Kenya. The approach recognizes the plurality of socially constructed and powerladen perceptions of environmental resources. We found that local people regard eucalyptus plantations not only as a threat to local water resources but they also highlight historical injustices and the loss of control over, and cultural relationships to their land. Bureaucratic resource management institutions, however, support the planting of eucalyptus to meet national demands for commercial forestry. Management officials also plead a lack of "valid" evidence for the negative impacts of eucalyptus on local water resources, diverting attention away from the formal environmental governance system which has unequal sharing of benefits, unclear policies, and internal incoherence. Recognition of historically rooted asymmetries of knowledge and power provides a step towards social transformation, ending a long-standing reproduction of subalternity, and promoting environmental justice and pluralism in decision-making. Keywords: bureaucratic knowledge; environmental justice; eucalyptus; Kenya; knowledge asymmetries; local ecological knowledge; political ecology; resource management
  • Korhonen, Jaana; Nepal, Prakash; Prestemon, Jeffrey P.; Cubbage, Frederick W. (2021)
    There is rising global interest in growing more trees in order to meet growing population, climate change, and wood energy needs. Using recently published data on planted forests by country, we estimated relationships between per capita income and planted forest area that are useful for understanding prospective planted forest area futures through 2100 under various United Nations Intergovernmental Panel on Climate Change-inspired Shared Socio-economic Pathways (SSPs). Under all SSPs, projections indicate increasing global planted forest area trends for the next three to four decades and declining trends thereafter, commensurate with the quadratic functions employed. Our projections indicate somewhat less total future planted forest area than prior linear forecasts. Compared to 293 million ha (Mha) of planted forests globally in 2015, SSP5 (a vision of a wealthier world) projects the largest increase (to 334 Mha, a 14% gain) by 2055, followed by SSP2 (a continuation of historical socio-economic trends, to 327 Mha, or an 11% gain), and SSP3 (a vision of a poorer world, to 319 Mha, a 9% gain). The projected trends for major world regions differ from global trends, consistent with differing socio-economic development trajectories in those regions. Our projections based on empirical FAO data for the past 25 years, as well as those by other researchers, suggest that achieving the much more ambitious global planted forest targets proposed recently will require exceptional forest land and investment supply shifts.