by André Boily | 30 January 2019
Acid Rain – Deposition to recovery. Brimblecombe, P., H. Hara, D. Houle et M. Novak (eds.). Springer, Dordrecht, The Netherlands. 419 p.
Acid rain is still with us. Although it is a problem that people have worked diligently to solve, there are still many problem areas throughout the world. In reality the focus of acid rain research has shifted, and this book adds new vision to the topic. It contains papers, selected from Acid Rain 2005, the 7th International Conference on Acid Deposition, that take a broad perspective of the issues, emphasizing a number of themes:
- the emission, concentration and deposition of pollutants;
- nitrogen and trace elements in ecosystems and their effects on forests, water and soil
- studies of material damage and recovery
- critical loads
The book is aimed at scientists and researchers who are working in the area of acid rain and its effects, and on nutrient cycling. This latest research will be of value to those concerned with the mitigation of acid rain effects.
by Claire Morin | 30 January 2019
Published in Forest Ecology and Management 291: 20-29
Improving predictions of the location of suitable environmental conditions for species using species distribution models (SDM) is at the core of biodiversity/climate change research, but modelling species abundance, rather than distribution, is proving particularly challenging. Using data from more than 200,000 forest plots in eastern North America and Random Forest, we evaluated the performance of species abundance models (SAM) in predicting the relative abundance (measured as importance value) of each of 105 tree species in relation to climate, edaphic, and topographic variables. We calculated the coefficient of determination (R2SAM) between observed and predicted abundances as a measure of model performance for each species. We also performed multiple linear regressions to explain variation of R2SAM among species using five biogeographical or spatial attributes of species as explanatory variables. Predictive performances of SAM (R2SAM) were generally low, ranging from 0.016 to 0.815 (mean = 0.258). Black spruce (Picea mariana) had the best predictive model and Florida maple (Acer barbatum) and American chestnut (Castanea dentata) the worst. Thirty-seven of the 41 best performing species (R2SAM ³ 0.3) had climate ranked as the best and/or second best predictor. Species with the best performance tended to be those that could reach dominance, showed aggregated distribution of abundance, and/or had high latitudinal limits in the study area. Climate change is likely to affect patterns of dominance in communities by altering patterns of co-occurrences, but for many species that constitute the bulk of tree diversity, predictions based solely on the current distribution of relative abundances may not be reliable enough to inform conservation or management decisions. Predicting tree abundance in a warming climate using SAM remains a challenge, but it is only by reporting performances across a range of climate and statistical models, regions and species, as well as by highlighting model limitations and strengths, that we will improve the reliability of predictions and in turn better inform forest conservation and management.
by Svetlana Savin | 30 January 2019
Published in Forest Ecology and Management 87(1996): 75-88
The biomass, litterfall, and soil organic matter dynamics during a complete bamboo talun-kebun rotation cycle were studied in West Java, Indonesia. This cycle consisted of 1 year of mixed species vegetable cropping (kebun) after the removal of bamboo, followed by 1 year of cassava, and 4 years of bamboo fallow (talun): a total cycle length of 6 years. In general, fruit and pod biomass constituted the highest percentage (38-68%) of the total crop biomass of 8.4 Mg ha-1 accumulated during the first year cropping. Cassava yielded a total of 4.6 Mg ha-1 of roots and tubers during the second year cropping from a total biomass accumulation of 6.7 Mg ha-1. An experimental second year of cassava cropping without any fertilization caused a decline in the yield of roots and tubers to 60% less than the comparable value for the first year of cassava. Weeds, which reached a maximum biomass value of 1.8 Mg ha-1 at the end of the first year cropping, were all but eliminated from the later stages of the bamboo talun. The total biomass of bamboo increased with increasing age and reached 76.6 Mg ha-1 after 6 years. The distribution of total bamboo biomass between above- and below-ground components also varied with age. At 16 months after bamboo harvest, above-ground biomass accounted for 6% of the bamboo total mass. By the end of the 4-year bamboo fallow, 6 years after the bamboo harvest, 59% of the bamboo biomass was above-ground. In the final year of the bamboo talun stage, total above-ground litterfall was estimated at 4.7 Mg ha-1, while the forest floor mass was 13.5 Mg ha-1. There was an increase of approximately 7 mg ha-1 of soil organic matter in the surface 25 cm of soil during the 4-year fallow. The historical, sustained success of the system with minimal external inputs of fertilizer appears to be closely related to the growth habit and biogeochemical characteristics of the bamboo, i.e. its rapid biomass accumulation, the accumulation of its litter, and the extremely high biomass of fine roots. This study provides scientific support for the traditional saying of the local farmers: “without bamboo, the land dies”.
by Svetlana Savin | 30 January 2019
Published in Canadian Journal of Forest Research 25: 1738-1745
Two experiments were designed to test the relationship between water content and frost tolerance in stems of hardwood seedlings during the frost hardening process. In the first experiment, 3-month-old container-grown yellow birch (Betula alleghaniensis Britton) seedlings were submitted to a decreasing temperature regime in a 8-h (short day, SD) or 16-h (long day, LD) photoperiod in growth chambers. In the second experiment, 3-month-old container-grown red oak (Quercus rubra L.), bur oak (Quercus macrocarpa Michx.), and yellow birch seedlings were naturally cold hardened in a production polyhouse. To estimate frost tolerance, freezing tests were performed on whole seedlings (experiment 1) or on the upper 5 cm of the stem apex (experiment 2), and stem damage was visually estimated. Water content of the apex (5 cm) was expressed as the ratio of dry mass over fresh mass (DM/FM) for both experiments. Frost tolerance and DM/FM increased during the course of both experiments. In the growth-chamber experiment, SD seedlings hardened deeper than LD ones (-19.2°C for SD versus -15.7°C for LD), and DM/FM was higher for SD after 60 days of photoperiod treatment. In the polyhouse experiment, bur oak, yellow birch, and red oak reached a frost tolerance of -26.7, -25.1, and -20.4°C, respectively, on November 2. The three species had DM/FM ratios of about 50% on November 2. For both experiments. DM/FM values higher than 45% corresponded to seedlings with a frost tolerance of -10°C or lower.
by Svetlana Savin | 30 January 2019
Published in Forest Ecology and Management 55: 259-278
Forest floor and mineral soil samples were collected from the interdune depressions of 6-, 8-, 17-, and 34-year old Casuarina equisetifolia Forst. & Forst. plantations growing on the coastal sand dunes of Senegal. The accumulation of organic matter as well as all mineral elements in the forest floor except sodium followed a linear pattern. The thickness of the litter layer increased from 4.2 to 8.0 cm. Forest floor biomass increased up to 120.3 Mg ha-1, an average increase of 3.3 Mg ha-1 year-1. Nitrogen in the forest floor accumulated up to 1567 kg ha-1; an average increase of 45 kg ha-1 year-1. Calcium, aluminium, magnesium, iron, potassium and phosphorus in the forest floor accumulated at 6.8, 3.7, 1.8, 1.3, 0.49 and 0.25 kg ha-1 year-1, respectively.
In the mineral soil, total phosphorus and exchangeable calcium decreased with plantation age. Nitrogen in the mineral soil increased by 30 kg ha-1 year-1 while organic matter in the mineral soil increased by 61.5 kg ha-1 year-1. The pH of the mineral soil decreased from 7.3 to 6.5.
As a result of a particular combination of species characteristics and ecological conditions, C. equisetifolia plantations on these coastal sand dunes appear to accumulate forest floor organic matter at rates comparable to those found in boreal and subalpine forests. A nitrogen to phosphorus ratio in the litter layer of 164:1 indicates that decomposition processes are strongly limited by phosphorus. This suggests that introducing strains of nitrogen-fixing bacteria capable of fixing even greater amounts of nitrogen would do little to improve soil fertility. Since there was no sign that accumulation of either organic matter or mineral nutrients had reached steady-state, a minimum of a 34 year rotation would seem justified if soil improvement is the primary management objective. Since the overwhelming majority of the organic matter and nutrient capital is located in the forest floor and upper 2 cm of mineral soil, proper management of this fragile layer following harvest will be extremely important if the benefits realized in the first rotation are to be capitalized on during subsequent rotations.
