Gene expression induced by chronic ozone in the Mediterranean shrub Phillyrea latifolia: analysis by cDNA-AFLP

Seedlings of Phillyrea latifolia L., a Mediterranean shrub, were exposed for 90 days to 110 nl l(-1) ozone (O(3)). Comparison of the cDNA-amplified fragment length polymorphism (cDNA-AFLP) patterns for treated and control plants allowed the identification and cloning of 88 differential sequences induced by O(3). The differential expression of 67 cloned sequences was further confirmed by RT-PCR. The functions of 36 cloned sequences, corresponding to seven of the twelve gene functional classes of Arabidopsis, were presumed on the basis of their homology with characterized gene sequences. Ozone induction of genes homologous to 24 of the clones has been reported in other plant species, whereas the induction of the 12 remaining sequences has not been observed before. Ozone activation of these newly identified genes could be a result of the chronic exposure to low O(3) concentration, because in most previous studies, acute treatments, involving high O(3) dosages, were applied. Possible roles of the cloned sequences in the response of P. latifolia to O(3) and other causes of oxidative stress are discussed.     

Tap root formation and early root/shoot ratio of Pinus Contorts and Pinus sylvestris

Scots pine and different provenances of lodgepole pine were compared in regard to root characteristics and the distribution of biomass within individual trees. Tap root formation was more frequent and the root/shoot ratio was higher on Scots pine than on lodgepole pine but significant variation of these traits was found between provenances of planted lodgepole pine. A non‐destructive method for estimation of root biomass was developed.     

Effect of spacing and water availability on root:shoot ratio in Eucalyptus camaldulensis

Our limited understanding of the processes that control the allocation of biomass in trees is one of the factors that hinders our ability to develop mechanistic models of tree growth. Furthermore, accurate assessment of carbon sequestration by forests is hampered by lack of information regarding below-ground biomass. Below-ground to above-ground biomass ratios (BGB:AGB) are known to vary with a number of environmental factors, tending to increase in drier, harsher conditions. However, there are few, good datasets of BGB:AGB ratios of large trees, especially native Australian species. We aimed to investigate the response of BGB:AGB to water availability and tree spacing in 10-year-old Eucalyptus camaldulensis growing in a plantation in a low rainfall area.We carefully harvested 16 trees, ranging in diameter at breast height (DBH) from 7.6 to 25 cm, from a research trial near Deniliquin, NSW. Four replicates of each treatment from a factorial design with wide (3 m × 6 m) and narrow (3 m × 1.5 m) spaced trees and with natural rainfall (408 mm/year) (control) or irrigated plots (flooded six times per year) were selected. Above-ground tree parts were harvested separating stem, branch and foliage. Soil cores to 1 m depth were taken to sample small roots (<15 mm diameter) within each plot, then all roots >15 mm belonging to each tree were excavated using compressed air and an excavator. Roots were separated into six size classes within the range from <2 to >50 mm.Both water and spacing treatments influenced tree growth with trees being larger in irrigated, wide spaced plots. The BGB:AGB ratio was strongly influenced by irrigation (0.68 control, 0.34 irrigated) but not spacing. Allometric analysis of above- and below-ground biomass as a function of DBH showed that the relationship between DBH and above-ground biomass was conserved across treatments.By contrast, the relationship between DBH and below-ground biomass was influenced by water availability, commensurate with the large differences in BGB:AGB ratio. The BGB:AGB ratio increased with tree size largely due to an increase in small roots.The proportion of total root mass in the small roots (<15 mm) obtained through coring was 25–48% with 18–30% of total root biomass in the <5 mm diameter class.     

Response of five tree species to salinity and waterlogging: shoot and root biomass and relationships with leaf and root ion concentrations

Unproductive saline and waterlogged (WT) wastelands could be beneficially transformed into agroforestry systems using trees tolerant to these stresses. We studied the salinity and waterlogging tolerance of five Australian tree species (Acacia salicina, Casuarina glauca, Casuarina obesa, Eucalyptus camaldulensis and Eucalyptus occidentalis) during seedling stage and their relationships with root and leaf ion concentrations. 8-month old plants were exposed for 5 months to five irrigation water salinity treatments (EC values between 2 and 22 dS m^?1) and two waterlogging treatments (drained or WT). The salinity tolerance of the five species was high, although decreased in WT conditions. Irrespective of salinity, the two Casuarina species were more tolerant and the other three species were less tolerant to WT than drained conditions. In all species, salinity and waterlogging increased leaf Cl^? and Na⁺ and decreased leaf Ca²⁺, but not leaf K⁺. Root Cl^? and Na⁺ increased with salinity but not with waterlogging. Salinity tolerance was negatively correlated with Cl^? and Na⁺ leaf accumulation rates per unit increase in salinity. Waterlogging reduced the ability of the seedlings to exclude Cl^? and Na⁺ from the leaves. The two most salt tolerant Casuarina species under both drained and WT conditions showed the highest leaf Cl^? and Na⁺ exclusion and the highest root Cl^? and Na⁺ accumulation, suggesting that sequestration of these toxic ions in their roots was a significant salt-tolerant mechanism. Revegetation of saline and WT wastelands with these tolerant Casuarina species could be profitably used for biomass, biofuel and renewable energy production.     

Grazing affects shoot growth,nutrient and water status of Quercus ilex L. in Mediterranean open woodlands

Context

Mediterranean open woodlands (dehesa) have faced a dual process of intensification and abandonment of grazing which has resulted in alteration of the understory vegetation.

Aims

We analysed the effects of land use changes on the physiological status of holm oak in different open woodlands (dehesa) in southern Iberian Peninsula.

Methods

In an area of extensive grazing, we selected six paired plots (one grazed, one abandoned) and grouped them by habitat types according to understory composition (nearly all monospecific Cistus ladanifer L. shrub or mixed shrub). Six plots of moderate and heavy grazing intensity were chosen within a settled area of livestock use. Shoot growth, macronutrient concentrations and water content were assessed in samples of holm oak leaves.

Results

Abandonment of grazing affected some nutrient concentrations and water content of holm oak leaves, but the effects were different according to habitat type. C. ladanifer shrub reduced N and P concentrations and water content while mixed shrub increased P concentration and water content. High grazing intensity improved shoot growth and leaf N and Mg concentrations.

Conclusion

Extensive grazing could be a useful management tool to enhance growth, nutritional and water status of holm oak in a habitat with limited resources such as Mediterranean open woodlands (dehesa).     

Carbon accumulation in aboveground and belowground biomass and soil of different age native forest plantations in the humid tropical lowlands of Costa Rica

Generic or default values to account for biomass and carbon accumulation in tropical forest ecosystems are generally recognized as a major source of errors, making site and species specific data the best way to achieve precise and reliable estimates. The objective of our study was to determine carbon in various components (leaves, branches, stems, structural roots and soil) of single-species plantations of Vochysia guatemalensis and Hieronyma alchorneoides from 0 to 16 years of age. Carbon fraction in the biomass, mean (±standard deviation), for the different pools varied between 38.5 and 49.7% (±3 and 3.8). Accumulated carbon in the biomass increased with the plantation age, with mean annual increments of 7.1 and 5.3 Mg ha⁻¹ year⁻¹ for forest plantations of V. guatemalensis and H. alchorneoides, respectively. At all ages, 66.3% (±10.6) of total biomass was found within the aboveground tree components, while 18.6% (±20.9) was found in structural roots. The soil (0–30 cm) contained 62.2 (±13) and 71.5% (±17.1) of the total carbon (biomass plus soil) under V. guatemalensis and H. alchorneoides, respectively. Mean annual increment for carbon in the soil was 1.7 and 1.3 Mg ha⁻¹ year⁻¹ in V. guatemalensis and H. alchorneoides. Allometric equations were constructed to estimate total biomass and carbon in the biomass which had an R ²aj (adjusted R square) greater than 94.5%. Finally, we compare our results to those that could have resulted from the use of default values, showing how site and species specific data contribute to the overall goal of improving carbon estimates and providing a more reliable account of the mitigation potential of forestry activities on climate change.     

Woody biomass on farms and in the landscapes of Rwanda

Scattered trees and woodlots are a prominent feature of agricultural landscapes of Rwanda. However, little is known about their characteristics and their contribution to farmers’ wood needs. Here, we present the results of a survey of (a) the abundance, composition, and size of trees and woodlots in the low, medium and high altitude regions of Rwanda, (b) total woody biomass and biomass for fuelwood at farm and landscape levels, and (c) opportunities for their sustainable use. Scattered trees occurred in all landscapes at minimum densities ranging from 20 to 167 trees ha^?1. Of the 56 tree genera recorded, a handful of tree species dominated, with the ten most common species accounting for over 70 % of all trees recorded. Most of them provided fuelwood, fruit and timber to farm owners. Woodlots occurred on about 40 % of the survey farms and consisted for 90 % of eucalyptus coppice. Woody biomass dry weight of scattered trees on agricultural landscape was 0.7 t ha^?1 in low altitude region (LAR), 3 t ha^?1 in medium altitude region (MAR), and 1 t ha^?1 in high altitude region (HAR). Dry weight woody biomass in woodlots (<0.5 ha) was the highest in MAR (221 t ha^?1), followed by that in HAR (205 t ha^?1) and least in LAR (96 t ha^?1). About 80 % of total woody biomass in trees and woodlots on farmland was useable biomass for fuelwood, indicating that the production of fuelwood on agricultural land was important. Woody biomass on agricultural land was higher than that in forest plantations, and was potentially sufficient to reduce the gap between fuelwood supply and demand when the entire agricultural area was taken into account. In order to achieve this on agricultural land, while contributing to food security and environmental conservation as well, smallholder farmers must be provided with incentives to grow woodlots and to adopt agroforestry systems, thereby considering the trade-offs with agricultural production. Strategies to encourage smallholder farmers to increase the use of agroforestry have to account for the farmers’ ecological and socioeconomic conditions.     

Estimates of forest biomass in the Brazilian Amazon: New allometric equations and adjustments to biomass from wood-volume inventories

Uncertainties in biomass estimates in Amazonian forests result in a broad range of possible magnitude for the emissions of carbon from deforestation and other land-use changes. This paper presents biomass equations developed from trees directly weighed in open forest on fertile soils in the southern Amazon (SA) and allometric equations for bole-volume estimates of trees in both dense and open forests. The equations were used to improve the commonly used biomass models based on large-scale wood-volume inventories carried out in Amazonian forest. The biomass estimates from the SA allometric equation indicate that equations developed in forests on infertile soils in central Amazonia (CA) result in overestimates if applied to trees in the open forests of SA. All aboveground components of 267 trees in open forests of SA were cut and weighed, and the proportion of the biomass stored in the crowns of trees in open forest was found to be higher than in dense forest. In the case of inventoried wood volume, corrections were applied for indentations and hollow trunks and it was determined that no adjustment is needed for the form factor used in the RadamBrasil volume formula. New values are suggested for use in models to convert wood volume to biomass estimates. A biomass map for Brazilian Amazonia was produced from 2702 plots inventoried by the RadamBrasil Project incorporating all corrections for wood density and wood volume and in factors used to add the bole volume of small trees and the crown biomass. Considering all adjustments, the biomass map indicates total biomass of 123.1 Gt (1 Gt = 1 billion tons) dry weight (aboveground + belowground) for originally forested areas in 1976 in the Brazilian Legal Amazon as a whole (102.3 Gt for aboveground only) at the time of the RadamBrasil inventories, which were carried out before intensive deforestation had occurred in the region. Excluded from this estimate are 529,000 km² of forest lacking sufficient RadamBrasil inventory data. After forest losses of 676,000 km² by 2006 – not counting 175,000 km² of this deforested area lacking RadamBrasil data – the estimated dry biomass stock was reduced to 105.4 and 87.6 Gt (aboveground + belowground and only above-ground). Thus, in 2006 the carbon storage in forested areas in Brazilian Amazonia as a whole will be around 51.1 Gt (assuming 1 Mg dry biomass = 0.485 Mg C). Biomass estimates by forest type (aggregated into 12 vegetation classes) are provided for each state in the Brazilian Legal Amazon.     

Space-time dynamics of fine root biomass of six forests in the Maoershan forest region, northeast China

The Maoershan forestry centre is situated in the Zhangguangcai Mountain of the Changbai mountain range. The main forest types in the Maoershan region are plantation (Pinus sylvestris var. mongolica, Pinus koraiensis and Larix gmelinii) and natural secondary forests (Fraxinus mandshurica, Quercus mongolica and Populus davidiana). Fine roots have enormous surface areas, growing and turning over quickly, which plays an important role in terms of substance cycling and energy flow in the forest ecosystem. This study deals with the dynamics of live, dead, and total fine roots (≤ 5 mm) biomass in the 0–30 cm soil layer using the soil core method. Differences between the six stands in the Maoershan region showed the following results: 1) the fine root biomass in the various stands showed obvious differences. The total fine root biomass of six stands from high to low were F. mandshurica (1,030.0 g/m²) > Q. mongolica (973.4 g/m²) > Pinus koraiensis (780.9 g/m²) > L. gmelinii (718.2 g/m²) > Populus davidiana (709.1 g/m²) > Pinus sylvestris var. mongolica (470.4 g/m²); 2) except for L. gmelinii, the development of live fine root biomass agreed with the trend of total fine root biomass. The maximum biomass of live fine roots in Pinus koraiensis or L. gmelinii stand appeared in May, others in June; in the F. mandshurica stand, the minimum biomass of live fine roots occurred in September, others in July or August; 3) the proportions of dead fine root biomass varied in different stands; 4) the vertical distribution of fine roots was affected by temperature, water, and nutrients; the proportion of fine root biomass was concentrated in the 0–10 cm soil layer. The fine root biomass of six stands in the 0–10 cm soil layer was over 40% of the total fine root biomass; this proportion was 60.3% in F. mandshurica. Space-time dynamics of the various stands had different characteristics. When investigating the substance cycling and energy flows of all forest ecosystems, we should consider the characteristics of different stands in order to improve the precision of our estimates. __________ Translated from Scientia Silvae Sinicae, 2006, 42(6): 13–19 [译自: 林业科学]     

The response of the pseudoannual species Trientalis europaea L. to forest gap dynamics in a near-natural spruce forest

The objective of this study was to test relationships between gap size, gap age and performance of the pseudoannual forest herb layer species Trientalis europaea. We also tested for a potential covariation of performance variables with light as the putative driving factor of gap size and gap age effects. The study took place in the core zone of the Harz National Park in a near-natural spruce forest at Mt. Brocken, Germany. We established 70 randomly distributed plots of three different gap age classes (<15 years, >15 and <60 years, >60 years) and undisturbed forest stands. We recorded growth variables of Trientalis (e.g. height of ramets, number of flowers and fruits per ramet and number of daughter tubers per ramet) and measured PPFD (photosynthetic photon flux density). Gap sizes were assessed with GPS, ranged from 131 m² to 16400 m² and were independent from gap age. Population density of T. europaea was neither affected by gap size nor by gap age. However, gap age had an effect on the fitness of Trientalis ramets. In gaps, the species produced a higher number of flowers and fruits. In general, the average proportion of flowering and fruiting was very low, with 13% and 4%, respectively. In contrast, light intensity had a significant positive effect on ramet density, while the number of daughter tubers differed between 0.8 and 0.5 tubers per individual under lowest light and full light intensity, respectively. The general conclusion is that gap size had no effects on the performance of T. europaea, while gap age had both direct effects and indirect effects mediated by light.     

Effects of a deep container on morpho-functional characteristics and root colonization in Quercus suber L. seedlings for reforestation in Mediterranean climate

In the last decades, reforestation and afforestation programs are being carried out mainly with containerized seedlings. Container design determines the morphological and physiological characteristics of seedlings. However, container characteristics are often the same for plant species with very different growth strategies. The most commonly used nursery containers are relatively shallow and limit tap root growth; consequently, species relying on the early development of a long tap root to escape drought, such as those of the Quercus genus, might need to be cultivated in deep containers. The aim of this paper was to compare the morphological and physiological characteristics of Quercus suber L. seedlings cultivated in shallow containers (CCS-18, depth 18 cm) with seedlings cultivated in deep containers (CCL-30, depth 30 cm). Both container types used were made of high-density polyethylene, cylindrical in shape, open-bottomed, with a diameter of 5 cm, two kinds of vertical ribs on the inside wall showing a cultivation density of 318 seedlings/m². At the end of nursery culture, the seedlings cultivated in the CCL-30 deep container presented a longer tap root, higher shoot and root biomass and higher Dickson Quality Index (DQI). Moreover, the CCL-30 seedlings showed a higher root growth capacity (RGC), they reached deep substrate layers faster and they presented higher root hydraulic conductance. These morpho-functional advantages improved the CCL-30 seedling water status, which was expressed by higher stomatal conductance during an imposed drought period.     

Erratum to: Effects of forest taxation and amenity preferences on nonindustrial private forest owners

The effects of profit and land value tax on harvesting decisions of nonindustrial private forest owners are investigated. We use a model of a utility-maximizing forest owner with amenity preferences for timber, which extends the basic two-period harvesting model to include both thinning and clear-cutting harvests. It is demonstrated that with no amenity preference, the profit and land value taxes are neutral to clear-cutting and thinning decisions. Under small to medium amenity preferences, the profit tax decreases the optimal clear-cutting volumes. However, the effect on thinning may be positive or negative, depending on the amenity preference level. The total effect of the profit tax on the short-run timber supply is negative. The effects of the land value tax contrast with those of the profit tax. Also, a tax regime with a lowered profit tax rate combined with a land value tax is analysed. It is shown to be able to bring Pareto-improvement to a regime that uses a higher profit tax but no land value tax.     

Nutrient cycling and growth in forest ecosystems of south western Australia: Relevance to agricultural landscapes

Nutrient and hydrologic cycles in harvested native forests in southern Australia are largely balanced. For example, we have little or no evidence of any decline in nutrient capital or availability in harvested forests. Short-term and small-scale reductions in evapotranspiration due to loss of leaf area after harvesting are adequately balanced at the landscape scale by large areas of regenerating or older-age forest. In contrast, agricultural systems on similar soils are a) dependent on large inputs of fertilisers to maintain growth and b) frequently subject to increasing salinity and waterlogging or other forms of degradation. The large-scale replacement of long-lived communities of perennial and often deep- rooting native species with annual crops or other communities of shallow-rooting species might be better managed within the framework of knowledge developed from studies of native plant communities. However, application of such a mimic concept to systems of low natural productivity is limited when agricultural systems require continued high productivity. Nonetheless, the mimic concept may help in developing sustainable management of agriculture on marginal lands, and contribute to the nutritional resilience of agroecosystems. Relevant characteristics for mimic agroecosystems in south western Australia include: high species diversity, diversity of rooting attributes, utilisation of different forms of nutrients (especially of N and P) in space and time, and the promotion of practices which increase soil organic matter content. This revised version was published online in June 2006 with corrections to the Cover Date.     

Estimating forest biomass increment based on permanent sample plots in relation to woodfuel consumption: a case study in Kampong Thom Province,Cambodia

To assess the sustainability of forest use for woodfuel, above ground biomass increment must be examined against woodfuel consumption. However, reliable data on the biomass increment of tropical forests are very limited. In this study, we estimated above ground forest biomass increment in Kampong Thom Province, Cambodia, using two consecutive measurements of 32 permanent sample plots in 1998 and 2000, and forest inventory data of 540 plots collected in 1997. The permanent sampling plot data were used to determine the relationship between initial biomass and subsequent biomass increment over a 2-year period. This relationship was applied to the inventory data to obtain a robust estimate of biomass increment across the major forest types for the entire province. The weighted average annual above ground biomass increment for the whole province was 4.77Mg/ha, or 2.3% of biomass. Woodfuel consumption was estimated to be about 2% of biomass increment for the province, suggesting that deficiency of woodfuel may not occur in this province. However, localized variation needs to be taken into account and there is a need to examine the effects of stand age and factors such as soil type, microtopography, and species composition on biomass increment and to consider woodfuel collection rate in specific forest areas with respect to accessibility for firewood collection.     

Forest characteristics affecting the rate of shoot pruning by the pine shoot beetle (Tomicuspiniperda L.) in Pinus radiata D. Don and P. sylvestris L. plantations

Different variables, such as altitude and presence of defoliators,were studied in Bizkaia (northern Spain) in order to assessthe susceptibility of Pinus radiata (D. Don) and P. sylvestris(L.) stands to Tomicus piniperda (L.) (Coleoptera: Scolytidae).Altitudes higher than 400 m, presence of logs, degree of thinningand incidence of fires, all increased the susceptibility ofP. radiata monocultures to shoot attack by T. piniperda. P.sylvestris plantations were more affected at alti tudes lowerthan 400 m and by poor forest hygiene. The presence of the processionarymoth (Thaumetopoea pityocampa Den and Schiff.) had a significanteffect on the rate of shoot pruning on the trees; vigorous treesand those with bare leader were more affected by the bark beetleattack if T. pityocampa larvae were feeding on their needles,while trees with dominance taken by the side shoots were lessattacked when moth larvae were present.