Long-Term Heavy Metal Retention by Mangroves and Effect on Its Growth: A Field Inventory and Scenario Simulation

The ability of mangroves in taking up and storing heavy metal (HM) helps in reducing HM pollution. However, HMs likewise adversely affect the growth of mangroves. We assess the effects of the long-term soil HMs enrichment on the growth of Rhizophora apiculata forest in the Can Gio Mangrove Forest (Southern Vietnam) in different environmental conditions of soil salinity, ground elevation, and tree density based on a novel set of measured data. These data were analyzed and were used to calibrate and validate for a tree growth model with influencing factors salinity, elevation, tree density, and heavy metals content. Three scenario simulations were performed to predict the mangrove dynamics under different levels of heavy metal pollution in combined environmental conditions of salinity and elevation. Simulation results show the decline of total forest biomass from 1,750,000 tons (baseline scenario with no HM pollution) down to 850,000 tons and 350,000 tons for the current HM pollution and double HM pollution scenarios, respectively. Both data analysis and simulations have shown that although mangroves can assist in reducing HM pollution, the quality and health of this ecosystem will be severely affected if the environment is excessively polluted. In addition, a data-and-model driven management tool is devised for the sustainable management of the mangrove environmental resources.

Impact of spacing and pruning on quantity, quality and economics of Douglas-fir sawn timber: scenario and sensitivity analysis

Controlling the long-term effect of management on the quantity and properties of individual boards is a fundamental challenge for silviculture. Within this basic study on Douglas-fir, we have investigated the sensitivity of the net present value (NPV) to three most common planting densities and a prominent pruning strategy. We therefore have applied an individual tree growth model, which represents intrinsic stem structure as a result of crown competition. The model extrapolated board strength development to the rotational age of 70 years, starting from real and comprehensive data recorded from experimental Douglas-fir plots at the age of 20 years. Total volume production increased from about 1600 m3 ha−1 for 1000 and 2000 trees ha−1 to 1800 m3 ha−1 for 4000 trees ha−1. The economic superiority of the lowest density stands increased considering the NPV at inflation-adjusted interest rates of 0%, 2% and 4%: Given an interest rate of 2% and no pruning, the NPV at 2000 was at about 50% of the one at 1000 trees ha−1. The NPV at 4000 trees ha−1 was even negative. Generally, artificial pruning was not effective. The revealed financial trade-off between growth and timber quality in young stands underlines the importance of silvicultural guidelines, which quantify the effect of management on yield per strength class and financial outcome.

A module to simulate the impact of western gall rust (Cronartium harknessii) on merchantable volume and lumber yields for lodgepole pine (Pinus contorta var. latifolia) stands in British Columbia

Western gall rust (Cronartium harknessii (J.P. Moore) E. Meinecke) is a pathogen that affects lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson) and has the potential to reduce lumber product yields derived from stands managed for the commercial production of timber. A dataset containing repeated measurements from 7775 trees located within the province of British Columbia, Canada, was used to develop equations that predict annual rates of stem infection, post-infection mortality, and the location of large stem galls. Results showed that annual rates of infection peaked between 3 and 5 years following stand establishment. Few new infections were predicted to occur beyond the stand age of 15 years. For an individual tree, the probability of first infection increased as its height increased relative to stand top height. The rate of mortality increased with the number of stem infections and was highest among trees infected within the first 3 years following planting. Mortality rates decreased thereafter, with many trees likely to survive to rotation. The equations predicting rust incidence and mortality were added to the Tree and Stand Simulator (TASS), an individual-tree growth model used within the province. A final equation predicting the location of large galls was added and allows TASS to account for losses due to the removal of stem defects during lumber manufacturing.

Handling Data Gaps in Reported Field Measurements of Short Rotation Forestry

Filling missing data in forest research is paramount for the analysis of primary data, forest statistics, land use strategies, as well as for the calibration/validation of forest growth models. Consequently, our main objective was to investigate several methods of filling missing data under a reduced sample size. From a complete dataset containing yearly first-rotation tree growth measurements over a period of eight years, we gradually retrieved two and then four years of measurements, hence operating on 72% and 43% of the original data. Secondly, 15 statistical models, five forest growth functions, and one biophysical, process-oriented, tree growth model were employed for filling these data gap representations accounting for 72% and 43% of the available data. Several models belonging to (i) regression analysis, (ii) statistical imputation, (iii) forest growth functions, and (iv) tree growth models were applied in order to retrieve information about the trees from existing yearly measurements. Subsequently, the findings of this study could lead to finding a handy tool for both researchers and practitioners dealing with incomplete datasets. Moreover, we underline the paramount demand for far-sighted, long-term research projects for the expansion and maintenance of a short rotation forestry (SRF) repository.