Bayesian inference of biomass growth characteristics for sugi (C. japonica) and hinoki (C. obtusa) forests in self-thinned and managed stands

Background Forests are an important sink for atmospheric carbon and could release that carbon upon deforestation and degradation. Knowing stand biomass dynamic of evergreen forests has become necessary to improve current biomass production models. The different growth processes of managed forests compared to self-managed forests imply an adaptation of biomass prediction models. Methods In this paper we model through three models the biomass growth of two tree species (Japanese cedar, Japanese cypress) at stand level whether they are managed or not (self-thinning). One of them is named self-thinned model which uses a specific self-thinning parameter α and adapted to self-managed forests and an other model is named thinned model adapted to managed forests. The latter is compared to a Mitscherlich model. The self-thinned model takes into account the light competition between trees relying on easily observable parameters (e.g. stand density). A Bayesian inference was carried out to determine parameters values according to a large database collected. Results In managed forest, Bayesian inference results showed obviously a lack of identifiability of Mitscherlich model parameters and a strong evidence for the thinned model in comparison to Mitscherlich model. In self-thinning forest, the results of Bayesian inference are in accordance with the self-thinning 3/2 rule (α=1.4). Structural dependence between stand density and stand yield in self-thinned model allows to qualifying the expression of biological time as a function of physical time and better qualify growth and mortality rate. Relative mortality rate is 2.5 times more important than relative growth rate after about 40 years old. Stand density and stand yield can be expressed as function of biological time, showing that yield is independent of initial density. Conclusions This paper addressed stand biomass dynamic models of evergreen forests in order to improve biomass growth dynamic assessment at regional scale relying on easily observable parameters. These models can be used to dynamically estimate forest biomass and more generally estimate the carbon balance and could contribute to a better understanding of climate change factors.

Trade-Offs among Release Treatments in Jack Pine Plantations: Twenty-Five Year Responses

We assessed 27 indicators of plant diversity, stand yield and individual crop tree responses 25 years post-treatment to determine long-term trade-offs among conifer release treatments in boreal and sub-boreal forests. This research addresses the lack of longer-term data needed by forest managers to implement more integrated vegetation management programs, supporting more informed decisions about release treatment choice. Four treatments (untreated control, motor-manual brushsaw, single aerial spray, and complete competition removal) were established at two jack pine (Pinus banksiana Lamb.) sites in Ontario, Canada. Our results suggest that plant diversity and productivity in boreal jack pine forests are significantly influenced by vegetation management treatments. Overall, release treatments did not cause a loss of diversity but benefitted stand-scale yield and individual crop tree growth, with maximum benefits occurring in more intensive release treatments. However, none of the treatments maximized all 27 indicators studied; thus, forest managers are faced with trade-offs when choosing treatments. Research on longer term effects, ideally through at least one rotation, is essential to fully understand outcomes of different vegetation management on forest diversity, stand yield, and individual crop tree responses.

Management of Maritime Pine: Energetic Potential with Alternative Silvicultural Guidelines

The interest in the use of energy of the forests has been increasing in recent decades. Biomass has the potential to provide a cost-effective and sustainable supply of renewable energy. Moreover, it could be valuable for reducing the severity of forest fires and create employment in extremely needy regions. This chapter brings to discuss the effect of forest management on the potential of energy provided by the woodlands. The authors selected as a case study the management of maritime pine (Pinus pinaster Ait.), an important softwood species in the southwest of Europe and, in particular, in Portugal where it represents around 22% of the forest area. A summary of traditional and new silvicultural guidelines for the species, used or proposed to be followed at the national level, is presented. The study follows with the evaluation of stand yield and the potential of energy associated with four alternative silvicultural guidelines. Two scenarios follow traditional standards (an initial density of 1100–1200 trees/ha), while the other two consider managing a high density stand (an initial density of 40,000 trees/ha). Simulations were performed with the ModisPinaster model. The results show that the new designs provide a considerable yield in terms of biomass and energy.

Success Factors for Experimental Partial Harvesting in Unmanaged Boreal Forest: 10-Year Stand Yield Results

Over the past two decades, partial harvesting has been increasingly used in boreal forests as an alternative to clearcutting to promote irregular stand structures and maintain a balance between biodiversity preservation and continued timber production. However, relatively little is still known about the silvicultural potential of partial harvesting in Canada’s boreal forest, especially in areas prone to organic matter accumulation (paludification), and most prior research has focused on biodiversity responses. In this study, we assess the effects of partial harvesting on stand development (recruitment, growth, and mortality) ten years after harvesting in previously unmanaged black spruce stands and quantify its effectiveness in reducing the impacts on ecosystem structures. Our analyses revealed that pre-harvest stand structure and site characteristics, especially initial basal area, sapling density, tree diameter, and organic layer thickness (OLT) were major factors involved in stand development ten years following these partial harvesting treatments. Depending on pre-harvest structure and site characteristics, partial harvesting can result in either an increase in post-harvest tree recruitment and growth or a loss of stand volume because of standing tree mortality. To increase the chances of partial harvesting success in ensuring an increase in decennial stand yield after harvest in black spruce forest stands, sites prone to paludification (i.e., where OLT >17 cm) should be left unharvested. This study illustrates the importance of taking into account pre-existing structure and site characteristics in the selection of management strategies to maximize the potential of partial harvesting to achieve sustainable forest management in black spruce stands.

CONTROLE DE PLANTAS DANINHAS EM FUNÇÃO DE DIFERENTES ESPAÇAMENTOS NO MILHO SILAGEM

RESUMO – O objetivo deste trabalho foi avaliar o controle de plantas daninhas no cultivo do milho silagem em diferentes espaçamentos entre linhas. Ele foi desenvolvido em Muzambinho-MG (Brasil), no ano agrícola de 2010/2011. Empregou-se o delineamento experimental em blocos casualizados e esquema fatorial 3x4, sendo utilizados três espaçamentos entre linhas (0,50 m; 0,75 m; 1,00 m) e quatro métodos de controle das plantas daninhas (testemunha “capina”; herbicida aplicado em pré-emergência das plantas daninhas; herbicida aplicado em pós-emergência das plantas daninhas; e herbicidas aplicados em pré-emergência e pós-emergência das plantas daninhas), com três repetições, totalizando 36 parcelas experimentais. Nas avaliações, além dos parâmetros fitotécnicos, como altura de plantas e espiga, diâmetros de colmo, produtividade, estande final, também foram avaliados paramentos físicos, químicos e biológicos da silagem, como a umidade a 65 °C e 105 °C, fibra bruta, proteína bruta, matéria mineral, extrato etéreo e fibra em detergente ácido e neutro. Houve interação significativa entre os manejos de plantas daninhas e os espaçamentos entre linhas, para as variáveis: estande final, produtividade, umidade a 65 °C, fibra bruta, e fibra em detergente ácido. A mudança no espaçamento entre linhas e na densidade de plantio afeta diretamente o manejo de plantas daninhas no cultivo de milho para silagem.Palavras-chave: herbicidas, controle químico, Zea mays, biplot. WEED CONTROL IN MAIZE SILAGE IN DIFFERENT SPACINGS ABSTRACT - This study aimed to evaluate the corn silage weed control in different row spacings. The work was developed in Muzambinho, State of Minas Gerais (Brazil), in the agricultural year 2010/2011. The experimental design was carried out with randomized block (RBD) in 3x4 factorial scheme with three row spacings (0.50 m, 0.75 m and 1.00 m) and four methods of weed control (witness “hoeing”; herbicide pre-emergent; herbicide-post emergent; and herbicide pre-emergent and post-emergent), and three replications. Plant height and ear insertion, stem diameter, yield and final stand, silage physical, chemical and biological parameters, such as humidity at 65 °C and 105 °C, raw fiber, raw protein, ash, ether extract and fiber in acid and neutral detergent, were evaluated. The interaction between weed management systems and spacings was significant for stand, yield, humidity at 65 °C, raw fiber, ether extract and acid detergent fiber. The change in line spacing and planting density directly affects weed management in silage corn cultivation. Keywords: herbicide, chemical control, Zea mays, biplot.

Long-term precommercial thinning effects on Larix occidentalis (western larch) tree and stand characteristics

Precommercial thinning (PCT) is used to increase tree size and shorten harvest rotation time. Short-term results from PCT studies often show a trade-off between individual-tree growth and net stand yield, while longer-term effects of PCT on tree growth and stand yield are less well documented. We used a 54-year-old PCT study to test long-term effects of forest density and thinning schedules on stand yield and tree-level characteristics in even-aged western larch (Larix occidentalis Nutt.) stands. The study has three target densities (494, 890, and 1680 trees·ha−1) crossed with three thinning schedules (target density achieved through one, two, or four entries). Analysis of variance (ANOVA) and linear contrasts were used to test the effects of density and number of entries on tree- and stand-level attributes. Thinning before stand age 10 years leads to long-term constant yield (219.0–269.5 m3·ha−1; P > 0.05) across the tested densities. We also found constant volume growth across stand densities during the most recent measurement interval (5.42–6.41 m3·ha−1·year−1; P > 0.05). Number of entries did not affect any tree- or stand-level attribute. The primary effect of early PCT is to control whether wood volume and growth are concentrated on few large, stable trees or spread over many small, unstable trees.