Do indicators of nitrogen retention and leaching differ between coniferous and broadleaved forests in Denmark?

The area of broadleaved forests is projected to increase in Denmark as well as in the rest of Europe. However, studies of the N leaching response to elevated N deposition have focused on coniferous stands and considerable uncertainty still remains on whether broadleaved and coniferous forests respond differently to elevated N. We studied N input–output relations for eight stands intensively monitored during 2002–2005 and literature data for 37 additional stands which together formed a comprehensive dataset on Danish forests including 26 broadleaved stands and 19 coniferous stands. Nitrate leaching was significantly higher in first generation stands on former arable land with mineral soil C/N ratios 10–15, but both low and high rates were observed independent of the N input. A net N loss was observed in some of these stands even though they are in the aggrading phase and accumulate N in the biomass. Broadleaved stands had significantly lower throughfall N deposition than coniferous stands and this seems to be the main process where forest type exerts an influence on the N cycle. Lower soil C/N ratios offset the effect of throughfall N deposition and thus N leaching did not differ between the two forest types. The best regression models for prediction of nitrate leaching included throughfall N deposition and C/N ratio, but only a minor part of the variability was explained. The C/N ratio of the upper mineral soil was more generally applicable than that of the organic layer. The N retention of the soil was reasonably well predicted above a C/N ratio of 25, but below this threshold the importance is not known. We suggest focusing future efforts on quantifying the relative retention functions (sink strength) of the vegetation and the soil organic matter to improve the predictions of N retention and N leaching.     

Steroid 5α-reductase inhibitory activity of condensed tannins from woody plants

In humans, steroid 5α-reductase is involved in the development of benign prostatic hyperplasia (BPH). We tested the steroid 5α-reductase inhibitory activity of the 70% acetone extract of woody plants. The tannin polymer prepared from the 70% acetone extract showed the highest steroid 5α-reductase inhibitory activity. Furthermore, the steroid 5α-reductase inhibitory activity of tannins was not affected by the addition of superoxide dismutase or catalase. It was concluded that the steroid 5α-reductase inhibitory activity of condensed tannin was caused by binding to the steroid 5α-reductase, rather than from the peroxide/superoxide produced by tannins. The tannins, prepared from tree barks, with potential for steroid 5α-reductase inhibitory activity might be advantageous in therapy for steroid 5α-reductase diseases such as BPH or prostate cancer. Part of this report was presented at the 54th Annual Meeting of the Japan Wood Research Society, Sapporo, August 2004     

Chemical composition and free radicals restraining activity of extracts from three Manglietia species leaves

The extracts from leaves of Manglietia insignis （Wall） Blume, Manglietia chingii Dandy and Manglietia yuyuanensis Law were prepared by organic solvent extraction and their components were analyzed by GC/MS and quantified. Meanwhile, the free radicals restraining activities were detected. The 21 compounds in M. insignis, 36 compounds in M. chigii and 20 compounds in M. yuyuanensis were identified. There were 11 common components in the extracts from three Manglietia species, and 12 components in two Manglietia species. The results of relative contents of every component in three extracts showed that the main constituents of M. insignis were terpenoids and alkene, amounting to 38.93%, followed by alkane （28.18%）, the nitrogen containing compounds （15.73%） and aromatic compounds （7.23 %）. The main constituents of leaf extract from M. chingii were the terpenoids and alkene, carboxylic acid, alkane and aromatic compounds, amounting to 30.22%, 14.17%, 13.87% and 13.29%, respectively, The main constituents of M. yuyuanensis were alcohol compounds, the terpenoids and alkene, and aromatic compounds, amounting to 28.00%, 25.38% and 18.00% respectively. The results showed that the three extracts had strong function of restraining oxygen free radicals. The ultra oxygen anions activity was restrained at the highest level, when the three extracts were diluted by hundred-fold, whereas the restraining capacity of hydroxyl free radicals reached maximum, when the three extracts were diluted by twenty-fold. The above results provide scientific evidences for further approaching the ecological healthy function of three MangUetia species     

Differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia × fraseri and Osmanthus fragrans

Leaf functional traits are adaptations that enable plants to live under different environmental conditions. This study aims to evaluate the differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia 9 fraseri and Osmanthus fragrans. Specific areas of red leaves are higher than that of green leaves in both species. Thus, the material investment per unit area and per lamina of red leaves is significantly lower than that of green leaves, implying an utmost effort of red leaves to increase light capture and use efficiency because of their low leafchlorophyll concentration. The higher petiole length of green leaves compared with that of red leaves indicates that adult green leaves may have large fractional biomass allocation to support the lamina structures in capturing light with maximum efficiency and obtaining a high growth rate. The high range of the phenotypic plasticity of leaf size, leaf thickness,single-leaf wet and dry weights, and leaf moisture of green leaves may be beneficial in achieving efficient control of water loss and nutrient deprivation. The high range of phenotypic plasticity of leaf chlorophyll concentration of red leaves may be advantageous in increasing resource(especially light) capture and use efficiency because this leaf type is juvenile in the growth stage and has low leaf-chlorophyll concentration.     

Do multipurpose companion trees affect high value timber trees in a silvopastoral plantation system?

Establishment of native timber trees on deforested land may contribute to the livelihood of farmers, to improved ecosystem services and to increased greenhouse gas uptake. Here, we present a new silvopastoral planting design to assess species performance and interspecific competition or facilitation effects among native timber and multipurpose trees in Central America. Two timber species, Tabebuia rosea and Cedrela odorata, were established in three low-density planting regimes allowing combined tree and future livestock production: (1) solitary planting, (2) companion planting with Guazuma ulmifolia, and (3) companion planting with the nitrogen-fixing Gliricidia sepium. We quantified survival, growth and reforestation potential of the two timber species subjected to the different planting regimes for the first 2 years after establishment. Nitrogen concentration as well as stable nitrogen and carbon isotope composition (δ¹⁵N, δ¹³C) of leaves of the timber saplings were determined. T. rosea showed higher survival and better growth than C. odorata under varying environmental conditions (soil, concomitant vegetation). Performance of the timber saplings was unaffected by either companion species. Planting regimes had no effect on foliar nitrogen concentration and δ¹⁵N of the two timber species, although δ¹⁵N values indicated nitrogen fixation activity in G. sepium trees. Planting regimes affected foliar δ¹³C values in T. rosea. δ¹³C values were significantly higher in solitarily growing individuals, suggesting lower exposition to water stress conditions in saplings surrounded by companion species. As we found positively correlated growth traits among timber and multipurpose trees, a combined planting may benefit farmers by providing additional goods and services.     

Does litterfall from native trees support rainfed agriculture? Analysis of Ficus trees in agroforestry systems of southern dry agroclimatic zone of Karnataka, southern India

Trees of the genus Ficus, integral components of indigenous rainfed agro-ecosystems of the southern dry agro-climatic zone of Karnataka, southern India, have traditionally been associated with the ecological service of soil quality enhancement in addition to various direct use benefits. We assessed the soil enrichment service of Ficus benghalensis L. a common Ficus species in these agroforestry systems, by quantifying nutrient return via litter fall. Litterfall estimation and chemical analysis of litter showed that F. benghalensis trees produce 3,512 kg ha-1 of litter annually which, on decomposition, can satisfy up to 76.70 % of N, 20.24% of P and 67.76% of K requirements of dryland crops annually per hectare. This can lead to an avoided cost of compost of US $ 36.46 ha-1·a-1 in dryland farming systems. The slow rate of decay of Ficus litter, as revealed in litter decomposition studies indicates its potential as ideal mulch for dryland soils. We discuss the complementarity between Ficus litterfall and cropping patterns in Mandya, and its implications for rainfed agricultural systems.     

Can picnic influence floral diversity and vitality of trees in Bhawal National Park of Bangladesh?

We examined the impact of picnic activities on forest diversity, structure, regeneration and vitality of tree species in the Bhawal National Park of Bangladesh. The study area was classified as a non-used, occasionally used and frequently used area on the basis of the intensity of the picnic activities. A total of 43 plant species were enumerated in the whole study area. The highest plant species richness (41 species) was observed in the non-used area whereas the lowest species richness (11 species) in the frequently used area. The diversity index decreased with the increase of picnic intensity whereas the concentration of dominance increased. Density of all plant groups except mature trees, and the basal area of the mature trees showed a declining trend from the non-used to frequently used area. The frequently used area exhibited very poor regeneration. Tree vitality decreased with the increase of picnic intensity. The relevance of our study as a basis for further research to determine the impact of tourism on biodiversity in Bangladesh is discussed.     

Fruits from shade trees in coffee: how important are they?

Agroforestry systems often receive attention and support in the literature for what is perceived as the benefits from multiple products associated with the trees that create the “forest” component of the setting. A comparison of small coffee growers’ use of fruits derived from the coffee agroforestry holding in Guatemala and Peru reveals that significant differences exist between these groups—not merely in the importance of the fruits themselves, but in the ways they are used. The overall importance of fruits from the coffee system accounts for a relatively small portion of the total value coming from the coffee area (about 10%), but the consumption and sales of the various products do generate needed income or sustenance for most farmers. The fate of fruits shows significant differences between the two countries. Whether at the farm level or on a per hectare basis, Guatemalan coffee farmers are more linked into a market economy and sell significantly more fruits than Peruvian farmers. The opposite is the case when on-farm consumption (use value) of the fruits is compared. While the potential value of these products may be quite large (from 95 to95 to 270/ha), we find that little gets consumed or sold, resulting in tremendous loss of potential benefits that could flow from these sources. Both groups lose more fruits than are sold or used, with Guatemalans foregoing more than three times the dollar value per hectare than Peruvians (151/ha vs.151/ha vs. 44/ha). Data about the economic context within which these growers and the fruits from coffee are found reveal possible reasons as to why we see the differences in use and exchange values realized in the two countries.     

Variability in permeability and integrity of cell membrane and depletion of food reserves in neem （Azadirachta indica） seeds from trees of different age classes

We quantified cell membrane permeability(electrical conductivityEC,water soluble sugar-WSS,and amino acids-AA)and integrity(phospholipids,α-tocopherol and lipid peroxidation)along with food reserve deterioration(total proteins,total sugar,and total starch)of neem seeds collected from various mother tree age classes and stored for 65days in airtight plastic containers at ambient room temperature(35±5°C).Results show that the activities were higher in fresh seeds(EC267.56-2950.01μS/g,WSS 19.96-19.48 mg/g and AA 5.40-5.35 mg/g)and declined with increasing duration of storage period(EC153.37-195.17μS/g,WSS 3.13-4.17 mg/g and AA 4.29-4.49 mg/g after35 days and EC 144.02-161.56μS/g,WSS 2.06-2.40 mg/g and AA3.98-4.27 mg/g after 65 days of storage).Phospholipids andα-tocopherol were higher in fresh seed(0.073-0.093 OD at 710 nm and0.080-0.105 OD,respectively)and declined as storage duration increased(0.033-0.042 OD at 710 nm and 00.0010-0.0020 OD,respectively).Dead seeds showed reduced amounts of phospholipids and minimum activity ofα-tocopherol(antioxidants).The level of MDA was lower in fresh seeds(0.0066-0.0087 OD at 600-535 nm)and increased as storage duration increased(0.0248-0.0268 OD after 65 days of storage).The higher amount of MDA indicated that seeds died due to rancidity of the oil inside the seed.Neem seed cake was assessed for deterioration of food reserves(total proteins,total sugar,and total starch),concentrations of which were higher in fresh seed and declined as storage duration increased.Germination was higher in fresh seeds and after 65days,no germination was received perhaps due to deterioration of biochemicals in seeds.Patterns of seed deterioration were similar across all seed lots.     

Can distribution of trees explain variation in nitrous oxide fluxes?

Abstract

The impact of distance to tree stems on nitrous oxide (N₂O) fluxes was examined to determine whether it is possible to improve the accuracy of flux estimates from boreal forest soils. Dark static chambers were placed along transects between pairs of trees within a Norway spruce stand and fluxes of N₂O and carbon dioxide (CO₂) were measured during the period 1999–2003. The groundwater table was measured on every sampling occasion along the transects. In addition, radiation transmission, potential diffusion rate and biomass of forest floor vegetation were measured once at each chamber site along one of the transects and soil samples were collected at three depths, from which pH, denitrification enzyme activity, soil moisture, organic matter, and carbon and nitrogen content were determined. There was a high level of variation in the N₂O fluxes, both spatially and temporally. However, the spatial variation in the N₂O fluxes within the transect could not be explained by differences in any of the measured variables. Sometimes, mainly when no major peaks occurred, N₂O fluxes were significantly correlated with CO₂ release. It is concluded that distance to stems cannot be used to improve the design of sampling schemes or for extrapolating flux levels to larger scales.     

Cone structure and seed development in grafted witches’ broom and normal crown clones from the same trees of Pinus sibirica

New Forests - Mutational witches’ broom represents a fragment of the tree crown with slower shoot growth, abnormally dense branching, decreased apical dominance and often with abundant...     

Excerpts from: Physiological and Medical Aspects of the Himalayan Scientific and Mountaineering Expedition, 1960–61

Please refer to Br Med J, September 8, 1962, pp 621–627 for a copy of this article.     

Do logging,followed by burning,and wildfire differ in their decadal scale effects on tall open-forest bryophytes and vascular plants?

There has been only one time-controlled study, in Canada, comparing the occurrence of bryophyte species in forests regenerating after wildfire with that in those regenerating after logging and regeneration burning. Previous work on vascular plants in Tasmanian tall open-forest dominated by Eucalyptus showed that filmy ferns were less common in areas that had been logged and regeneration burned than in areas burned by wildfire two decades after the events, which suggested that hygrophilous species, such as bryophytes, might be vulnerable to this silvicultural system. Bryophytes, vascular plants structural and environmental data were collected from 50 sites, which had been burned in wildfires or clearfelled and burned by prescribed fires 31–39 years previously. Eighteen percent of the vascular plant species for which it was possible to develop a multiple regression model had logging/wildfire as a component, whereas the equivalent figure for bryophytes was 17%. The negative effects of logging were concentrated on the more hygrophilous species, and the positive effects were concentrated on the basal area of tree species and some of the mosses dependent on them. We conclude that wildfire and logging followed by regeneration burning result in vegetation differences that last more than three decades after disturbance, that these differences are no more pronounced for bryophytes than for vascular plants, and that hygrophilous taxa are favoured more by wildfire than logging.     

Do partial cross sections from live trees for fire history analysis result in higher mortality 2 years after sampling?

Although partial cross sections from live trees have been utilized in the development of fire history studies, few efforts have been made to examine the effects of this method on the individual trees that were sampled. We examined 115 red pine (Pinus resinosa Ait.), eastern white pine (Pinus strobus L.), and jack pine (Pinus banksiana Lamb.) trees from which partial cross sections had been removed 2 years earlier, and 209 similarly sized neighboring red pine and eastern white pine trees. Two years following the removal of partial cross sections, 22 sampled trees (19%) had died. When compared with neighboring trees, removing a partial cross section did not appear to increase the mortality rate for a given tree (t-test; P = 0.150). However, when we compared the characteristics of the trees with partial cross sections removed, we did observe some trends; i.e., those trees that died were primarily killed by wind-induced breakage at the level of the partial cross section. Almost all stems where partial cross sections were collected from a catface edge or had >30% of the total area removed were more susceptible to stem breakage and experienced an increased likelihood of mortality. While these results suggest that the collection of partial cross sections from live trees may be an effective method for fire-history sampling, the negative impacts of the sampling on individual trees may be reduced by ensuring that samples are collected from the center, rather than the catface edge, and <25% of the total stem area is removed.     

Stress-wave velocity of trees and dynamic Young’s modulus of logs of 4-year-old Eucalyptus camaldulensis trees selected for pulpwood production in Thailand

Eucalyptus camaldulensis Dehnh. is extensively planted in Thailand to produce wood chips used as raw material for pulp and paper. To promote the utilization of the wood from plantation-grown E. camaldulensis for solid lumber, stress-wave velocity of trees and dynamic Young’s modulus of logs were investigated for 4-year-old trees of eight half-sib families selected for pulpwood production on the basis of the growth characteristics in the previous tree breeding program. For the eight families, the mean stem diameter at 1.3 m above ground level and mean tree height were 7.6 cm and 11.9 m, respectively. The mean stress-wave velocity of eight families was 3.45 km/s. Dynamic Young’s modulus of logs ranged from 7.88 to 17.64 GPa, and the mean value for the eight families was 11.72 GPa. Stress-wave velocity of trees was significantly correlated with dynamic Young’s modulus of logs, suggesting that dynamic Young’s modulus of wood can be evaluated nondestructively by stress-wave velocity of trees. Significant differences in stress-wave velocity and dynamic Young’s modulus of logs were obtained among families. Thus, to promote the utilization of E. camaldulensis wood for solid lumber production, selection of trees with high Young’s modulus should be applied to trees already selected for the growth characteristics in the previous tree breeding program.     

Are composts from shredded leafy branches of fast-growing forest species suitable as nursery growing media in arid regions?

The morpho-physiological quality of seedlings is negatively affected by the wide scale use of forest soils as substrates in developing countries. With the objective of finding long-term sustainable supply of growing media, compost was produced from shredded branches of three fast growing species (Acacia cyanophylla (AA), Acacia cyclops (AS) and Eucalyptus gomphocephala (EG). The composting process covered three different periods over the course of a year. Pile temperatures were monitored daily and the composts were routinely sampled and analyzed for 19 chemical variables. Although composting is feasible year-round in arid climates, compost produced in the humid cool conditions of autumn, winter and early spring reaches the maturation phase more quickly than compost produced under hot, dry summer conditions. It also requires less turning and water. The evolution of the composting process and quality of the final product can be assessed using three chemical variables (C/N, pH, EC). Seed germination rates in the three types of compost were similar to that in a peat:vermiculite substrate and vigorous high quality seedlings were produced in the two acacia composts. However, compost-grown seedlings had significantly smaller shoots and root systems than those produced in peat substrate. Principal components analyses showed that the quality of a compost-based substrate is reproducible and that its final chemical composition can be predicted from its raw organic materials. The EG composts had higher pH than the acacia composts, whereas the AA and EG composts were higher in mineral salts than the AS.     

Why and where do adult trees die in a young secondary temperate forest? The role of neighbourhood

? The density and identity of tree neighbourhood is a key factor to explain tree mortality in forests, especially during the stem exclusion phase.

? To understand this process, we built a logistic model for mortality in a spatially explicit context, including tree and neighbourhood predictors. Additionally, we used this model to build mortality risk frequency distributions. Finally, we tested this model against a random mortality model to predict the spatial pattern of the forest.

? Annual mortality rate was high for pedunculate oak (Quercus robur, 6.99%), moderate for birch (Betula celtiberica, 2.19%) and Pyrenean oak (Q. pyrenaica, 1.58%) and low for beech (Fagus sylvatica, 0.26%). Mortality risk models for pedunculate oak and birch included stem diameter, tree height, canopy position and neighbourhood. Mortality was affected by the specific nature of the neighbourhood showing a clear competitive hierarchy: beech > pedunculate oak > birch. Models based on random mortality and logistic regression model were able to predict the spatial pattern of survivors although logistic regression predictions were more accurate.

? Our study highlights how simple models such as the random mortality one may obscure much more complex spatial interactions.

     

Can differences in root responses to soil drying and compaction explain differences in performance of trees growing on landfill sites?

Two tropical woody species, Acacia confusa Merrill and Litsea glutinosa (Lour.) C.B. Robinson, were grown under controlled conditions in PVC pipes filled with John Innes No. 2 soil. To investigate root distribution, physiological characteristics and hydraulic conductivity, four soil treatments were imposed-well-watered and noncompacted (control), well-watered and compacted; unwatered and noncompacted, and unwatered and compacted. In L. glutinosa, rooting depth and root elongation were severely restricted when soil bulk density increased from around 1.12 to 1.62 g cm(-3), whereas soil compaction had little effect on these parameters in A. confusa. As soil drying progressed, root water potential and osmotic potential declined more slowly in L. glutinosa than in A. confusa. Both the soil drying and compaction treatments significantly stimulated the accumulation of root abscisic acid (ABA) in both species. Soil drying damaged the root cell membrane of A. confusa, but had little influence on the root cell membrane of L. glutinosa. Soil drying had a greater effect on root hydraulic conductivity (L(p)) in L. glutinosa than in A. confusa, whereas the effect of soil compaction on L(p) was less in L. glutinosa than in A. confusa. Soil drying enhanced the effects of soil compaction on root L(p). We conclude that soil drying and compaction have large species-specific effects on the distribution, growth and physiology of roots. The relationships of these root properties to the species' ability to tolerate unfavorable soil conditions were examined.