'n Ondersoek van die Houtopbrengs,Digtheid en Krimping van Tienjaaroud Eucalyptus grandis-bome

Nine composite trials of Eucalyptus camaldulensis and E. terecticornis were planted in South Afrca and SWA/Namibia during 1973 and 1974. In the semi-arid areas of the two trials in SWA, E. camaldulensis was superior in survival and growth to E. terecticornis. The use of irrigation or access to abundant subsurface water is essential for the development of either species in semi-arid or arid areas (Darrow, 1983).     

Residual effects of fallows on selected soil hydraulic properties in a kaolinitic soil subjected to conventional tillage (CT) and no tillage (NT)

Improved fallows have been used to reduce time required for soil fertility regeneration after cropping in low input agricultural systems. In semi-arid areas of Southern Africa, Acacia angustissima and Sesbania sesban are among some of the more widely used improved fallow species. However the residual effects of improved fallows on soil hydraulic properties during the cropping phase is not known. The aim of this study was to quantify the residual effects of fallows and tillage imposed at fallow termination on soil hydraulic properties (infiltration rates, hydraulic conductivity and soil porosity) during the cropping phase. Treatments evaluated were planted fallows of Acacia angustissima, Sesbania sesban and natural fallow (NF) and continuous maize as a control. Steady state infiltration rates were measured using a double ring infiltrometer and porosity was calculated as the difference between saturated infiltration rates and tension infiltration measurements on an initially saturated soil. Unsaturated hydraulic conductivity (K_o) and mean pore sizes of water conducting pores were measured using tension infiltrometer at tensions of 5 and 10 cm of water on an initially dry soil. While there was no significant difference in steady state infiltration rates from double ring infiltrometer measurements among the fallow treatments, these were significantly higher than the control. The steady state infiltration rates were 36, 67, 59 and 68 mm h^-1 for continuous maize, A. angustissima, S. sesban and NF respectively. Tillage had no significant effect on steady state infiltration rate. Pore density at 5 cm tension was significantly higher in the three fallows than in maize and varied from 285–443 m⁻² in fallows, while in continuous maize the pore density was less than 256 m⁻². At 10 cm tension pore density remained significantly higher in fallows and ranged from 4,521–8,911 m⁻² compared to 2,689–3,938 m⁻² in continuous maize. Unsaturated hydraulic conductivities at 5 cm tension were significantly higher in fallows than in continuous maize and were 0.9, 0.7, 0.8 cm and 0.5 cm h⁻¹ for A. angustissima, S. sesban, NF and continuous maize, respectively. However there were no significant treatment differences at 10 cm tension. Fallows improved infiltration rates, hydraulic conductivity and soil porosity relative to continuous maize cropping. Through fallowing farmers can improve the soils hydraulic properties and porosity, this is important as it affects soil water recharge, and availability for plant growth     

Water harvesting in a ‘runoff-catchment’ agroforestry system in the dry lands of Ethiopia

A major production constraint in arid and semiarid areas of Ethiopia is a lack of water for crop growth. Run off water can be harvested by channeling it into micro- catchments (MC) where it slowly infiltrates into the soil. The increased moisture provides more plant growth in these dry lands. An experiment using MC was conducted in eastern Ethiopia to study the growth of four multipurpose tree species intercropped with grass. Trees and grass were grown in 25 m² and 100 m² MC. Plant height, root collar diameter, and mortality rate of trees were determined 12 months after planting. Dry matter yield of grasses and trees were measured and nutrient analysis of plant tissues was determined. In a separate experiment the biomass of trees was determined after 2.5 years of continuous growth without grass competition. Soil moisture, organic matter, texture and bulk density of the soils were also determined. Mean tree height was 10% greater in the 100 m² than in the 25 m² MC. Root collar diameter and survival rate showed similar increase with 13% and 7.8% respectively. Acacia saligna and Leucaena leucocephala showed better growth in both plot sizes than the indigenous Acacia seyal and Acacia tortilis. The dry matter yield of grass (Panicum maximum) was over 12 tons/ha and 8 tons/ha in the 100 m2 and 25 m2 plots respectively. Soil moisture content was greater in MC than in control plots with no water harvesting structures with 31% and 24% during the wet and dry seasons respectively. The use of water harvesting can improve fodder production and carrying capacity of the dry lands of Ethiopia.     

Performance of eight tree species in the highland Vertisols of central Ethiopia: growth, foliage nutrient concentration and effect on soil chemical properties

The coverage of trees in the highland Vertisol areas of Ethiopia is very scarce. A tree screening trial was conducted from 1997 to 2002 in Ginchi (central Ethiopia) to select fast growing and high biomass producing tree species; evaluate foliage macronutrient concentration of different tree species; and assess effects of trees on soil chemical properties beneath their canopies. Acacia decurrens Willd, A. mearnsii De Wild and Eucalyptus globulus Labill attained the highest height growth at 64 months as compared to other indigenous and exotic species. E. globulus provided better height increment from 24 to 36 and 36 to 64 months than other tree and shrub species. Acacia mearnssi and A. saligna Labill Wendl produced high biomass at 40 and 64 months. Differences between the highest and lowest dry biomass at 12, 40 and 64 months were 1.13, 29.19 and 38.89 kg tree⁻¹, respectively. None of the tree species resulted in a foliage to stem biomass ratio of >0.98 at 40 and 64 months. Sesbania sesban (L.) Merr had high N and P concentrations in its foliages and stems at 12 and 40 months. Total N under Acacia abyssinica Hochst. Ex Benth, A.␣saligna and S. sesban was slightly greater at 40 months than 12 months.     

Informal surveys to assess social forestry at Dibandiba and Aleta Wendo,Ethiopia

Two surveys were carried out at Dibandiba, a semi-arid site in central Ethiopia, and Aleta Wendo, a sub-humid site in southern Ethiopia, to assess farmers' attitudes toward and perceptions of tree planting, levels of social forestry and uses of tree products. At Dibandiba, farmers planted mostlyEucalyptus camaldulensis trees, exclusively on homesteads andAcacia albida was left on farmland. Trees were planted mainly for construction (32%), fuelwood (29%), shade (11%) and cash (11%). Major (85%) uses were fencing, fuelwood, construction and plough handles. Dung was the major source of fuel (56%). At Aleta Wendo, planting consisted ofEucalyptus globulus mostly on private woodlots and homesteads, ofMilletia ferruginea andCordia abyssinica on farms, and ofEuphorbia abyssinica on fences and boundaries. Avocado and pears were also planted. The uses were the same as at Dibandiba. Major constraints were lack of seedlings and shortage of land at both sites, plus shortage of water at Dibandiba. Also, a review of information obtained from previous surveys on household composition and income, farm holding, cropping pattern, livestock composition and the use of labour was made.     

Comparative growth performance of some multipurpose trees and shrubs grown at Machakos,Kenya

Growth rates of 29 multipurpose trees grown in an agroforestry arboretum for six years at a sub-humid to semi-arid climatic zone are presented. Exotic species such as Grevillea robusta, Sesbania grandiflora, Leucaena leucocephala, Cassia siamea and Sesbania sesban, some of which were outside their traditional climatic zones, had higher diameters, heights and bole volumes/tree (upto 130% more in certain cases) than of the indigenous species. However, poor performance of several species (both exotic and indigenous) would limit their agroforestry potentials at the evaluation site or other similar areas.     

Agroforestry and forestry on the Cape Verde Islands

The geography, socio-economy, climate and agriculture of the Cape Verde Islands are introduced. Forestry and agroforestry provenance trials are described for coastal and inland areas in the semi-arid climate of Cape Verde. Sesbania sesban var. nubica showed promise as a drought tolerant, fast growing agroforestry species and Acacia bivenosa is recommended for soil stabilisation of exposed coastal areas. At a saline coastal site Atriplex lentiformis and A.halimus were the fastest growing of seven Atriplex species.     

Identification of the Armillaria root rot pathogen in Ethiopian plantations

Armillaria root rot is a well‐known disease on a wide range of plants, world‐wide. In Ethiopia, the disease has previously been reported on Pinus spp., Coffea arabica and on various native hardwoods. The causal agent of the disease has been attributed to Armillaria mellea, a species now known to represent a complex of many different taxa. The aim of this study was to determine the extent of Armillaria root rot and the identity of the Armillaria sp. in Ethiopian plantations. As part of a plantation disease survey in 2000 and 2001, samples were collected in plantations at and around Munessa Shashemene, Wondo Genet, Jima, Mizan and Bedele, in south and south‐western Ethiopia. Basidiocarps were collected and their morphology studied. Morphological identification was confirmed by sequencing the intergenic spacer (IGS‐1) region of the ribosomal rRNA operon and comparing data with published sequences of Armillaria spp. Armillaria isolates were collected from Acacia abyssinica, Pinus patula, Cedrela odorata and Cordia alliodora trees. Sporocarps were found on stumps of native Juniperus excelsa. Basidiocarp morphology and sequence data suggested that the fungus in Ethiopia is similar to that causing disease of Pinus spp. in South Africa and previously identified as A. fuscipes. This identification was confirmed for all isolates, based on sequence data. Armillaria fuscipes is known to be common in southern Africa. Its widespread occurrence in Ethiopia suggests that it is also the major cause of Armillaria root rot in that country.     

Survival and long-term growth of eucalypts on semi-arid sites in a Mediterranean climate,South Africa§

Four experiments were established on the semi-arid west coast plain of South Africa during the 1990s. The trails tested the survival and growth of several eucalypt species and hybrids, some of which were established in a climate that is drier than their natural distribution range. The aridity indices (AI; defined as mean annual precipitation [MAP]/mean annual potential evapotranspiration) ranged from 0.21 to 0.36 and MAP from 228 to 423 mm. The driest trial site (AI = 0.21 and MAP = 228) had high levels of mortality. However, a number of species (in particular, Eucalyptus gomphocephala, E. camaldulensis and E. tereticornis, as well as individual hybrids of the latter two species with E. grandis) survived and grew well at the remaining sites. Eucalyptus cladocalyx survived well and attained competitive growth rates only on the wettest site in the group (AI = 0.36). The dominant height of the top-performing genotypes at age 5 ranged between 9 and 10 m on the two wetter sites. This corresponded to mean annual increment values in excess of 10 m³ ha^?1 a^?1, which is comparable to volume obtained at more favourable aridity indices in the summer rainfall zone of South Africa and exceeds the growth rates obtained in several other arid zone studies globally. The E. grandis × E. camaldulensis hybrid ranked among the top performers in two trials, but its susceptibility to recently introduced pests and relatively poor wood quality makes it a less attractive choice for planting. The high density and durability of timber, acceptable growth rate (given the low rainfall conditions), and low pest and disease incidence make E. gomphocephala and E. cladocalyx the species of choice for planting in the drier and relatively wetter sections of the semi-arid zone, respectively.     

Chemical composition,in vitro dry matter digestibility and in sacco degradability of selected browse species used as animal feeds under semi-arid conditions in Northern Ethiopia

The study was conducted in Abergelle district of Tigray, northern Ethiopia with the objectives of evaluating the chemical composition, in vitro dry matter digestibility (IVDMD) and in sacco degradability characteristics of foliages of major browse species. Samples of foliages from 12 and 10 browse species were collected during the wet and dry seasons, respectively. The samples of the browse species were collected based on their abundance in the district, preference by livestock to browse them, accessibility to browsing and their additional uses other than livestock feed. The neutral detergent fiber (NDF) was higher in the browse species during the wet compared to the dry season except for Sterculia africana and Ziziphus spina-christi. Similar trends were observed for acid detergent fiber (ADF) content except for Acacia asak. The condensed tannins content and the IVDMD of the browse species had inverse relationships in both seasons. The in sacco dry matter (DM) and nitrogen degradability parameters of the browse species were seasonally variable. Based on in sacco potential DM and nitrogen degradation of the browse species in both seasons, Acacia oerfota, Acacia tortilis, Balanites aegyptiaca, Boswellia papyrifera, Sterculia africana, Terminalia brownii and Ziziphus spina-christi were ranked to be superior in their nutritive value, and thus can have better use as animal feeds. Consequently, these browse species could be considered in agro-forestry systems for better integration of livestock production with available feed resources in semi-arid areas.     

Growth and Survival of Drip-Irrigated Hybrid Poplar in the Semi-Arid Four Corners Region

Abstract

Rapid growth rates and versatility have made hybrid poplar (Populus L.) a common choice to fulfill timber and pulp needs in temperate regions with adequate precipitation. Hybrid poplar production in drier regions has recently received interest as an irrigated source of cut logs and shredded fiber. Ten hybrid poplar clones were selected from nurseries in Washington and Oregon to determine their growth potential and water-use requirements on a calcareous soil at the NMSU Agricultural Science Center in Farmington, NM. Planted in May 2002, the clones were evaluated for survival growth characteristics over two seasons. Clones 50-194 and 184-411 had poor survival and were not continued during the 2003 season. Clone OP-367 had low chlorosis ratings, the greatest height (4.16 m), basal diameter (9.16 cm), diameter at breast height (4.65 cm) and wood volume (2.87 m³ ha^-1) during both seasons. A range of responses to environmental conditions of the Four Corners region was exhibited. Mid-season leaf greenness, as determined with a SPAD-502 chlorophyll meter, was a good predictor of growth characteristics. OP-367 appeared to be a potential candidate for inclusion in drip-irrigated wood production strategies for this and other arid/semi-arid regions of the world.     

Hybrid poplar (<Emphasis Type="Italic">Populus</Emphasis> ssp.) selections for arid and semi-arid intermountain regions of the western United States

The rapid growth rates of hybrid poplar (Populus spp.) enable rotations of 3–6 years for biofuels or 10–15 years to obtain merchantable timber, but many clones are susceptible to nutrient deficiencies when grown in alkaline soils. A 1995 Oregon study demonstrated that clone OP-367 (P. deltoides × P. nigra) was the only clone tested that performed well on alkaline soils. Tests in Colorado and New Mexico confirmed the adaptation of this clone. A multi-clonal trial was established in 2003 at Farmington, New Mexico and Ontario, Oregon in order to screen a larger number of clones for adaptability to alkaline soils. Trees were planted at 1.5 × 1.5 m spacing and irrigated by surface drip irrigation. Diameter at breast height (DBH) and tree height were recorded annually (2003–2006); wood volumes (WVol) and total aboveground biomass (TAB) were calculated from these measurements. Of the 25 clones tested, 19 were common to both sites. Mean height was greater at the Ontario site through the first 3 years (2003–2005). By the end of four seasons, the tallest Farmington entry was OP-367 at 9.4 m with 177 Mg ha⁻¹ TAB while the tallest Ontario entry was Malheur-3 at 8.9 m with 195 Mg ha⁻¹ TAB and several other clones had statistically similar production. Given the growth and productivity range at these two sites, it is difficult to make generalizations across wide areas, but it appears feasible to identify clones suited to alkaline soils in arid and semi-arid regions.     

To prune or not to prune Faidherbia albida: competing needs for water,wheat and tree products in semi-arid Ethiopia

Faidherbia albida is one of the scattered trees commonly intercropped with most cereals in Ethiopia due to its positive impacts. The tree is pruned for various purposes including for fencing and fuelwood. In this study, the impact of pruning on water relations of F. albida and on understorey wheat productivity was investigated. The on-farm study was conducted in Ejerssa Joro, semi-arid Ethiopia. Six mature trees were selected; three were fully pruned and three were left unpruned. Sap flow and leaf water potential were measured on these trees. Crop gas exchange, aboveground biomass and grain yield were measured under and outside tree canopies. The highest and the lowest sap volumes, recorded from unpruned F. albida, during the dry period, were 153 L day^?1 and 20 L day^?1, respectively. The highest and the lowest sap volumes were 13.4 L day^?1 and 0.04 L day^?1 recorded during the wet period. Wheat CO₂ assimilation was highest (7.8 µmolm^?2 s^?1) at 1 m distance and declined away from the tree trunk under unpruned trees. Aboveground biomass and grain yield under unpruned treatments were significantly (P?<?0.05) higher than outside of canopy of same tree and outside canopies of pruned trees. Pruning reduced aboveground biomass and grain yield by 30% and 27%, respectively; despite the higher water uptake by unpruned trees. We recommend that intensive pruning of F. albida be discouraged and propose further studies on optimal pruning for increased food production and provision of tree products to meet farmers’ needs.

     

Effects of scattered Acacia tortilis (Forssk) hayne on soil properties in different land uses in Central Rift Valley of Ethiopia

Among several agroforestry practices in the Central Rift Valley (CRV) of Ethiopia, Acacia tortilis-dominated Parkland agroforestry systems are common. Utilizable information regarding the effects of the tree species on soil conditions in Ethiopia is very scarce to be of use for improved agricultural productivity. This study was conducted in three land use types in CRV areas in Oromia National Regional State in Ethiopia. The aim of the study was to determine the effects of A. tortilis on soil fertility variations along a gradient from the tree base to open area in different land use types. Soil samples from surface layers (0–15 cm) were taken at four concentric transects distances from tree base (0.5, 2 and 4 m), compared with soil samples from the adjacent open areas (15 m distance from the tree canopy cover), and then analyzed following the standard procedures. The results of the study indicated that except for Na the amount of soil nutrients under A. tortilis were significantly varied (P < 0.05) in the land use types. Generally, comparisons between under the canopy and outside the canopy of the tree species indicated a highly significant difference on major soil fertility parameters. The effect of the tree species on soil fertility parameters was significantly higher with the distance from the tree base to outside of the canopy. But soil texture was not affected, indicating that it is more related to parent material and land use practices than the tree influence. The study revealed that the indigenous Parkland agroforestry practices of A. tortilis tree improve soil fertility. Hence, the soil patches observed under A. tortilis trees can be important local nutrient reserves, leading to soil heterogeneity in an otherwise uniform agricultural landscape. This may be important for the agricultural landscape health and on farm biodiversity conservation in agricultural landscapes of similar agroecological conditions.     

降雨对干旱半干旱地区土壤微生物影响研究进展

未来气候变化预示着降雨时间和数量的变化。降雨是干旱半干旱地区最重要的水分来源,降雨格局的变化将直接影响该区域生态系统的稳定性,而土壤微生物作为敏感指标多用来监测生态系统的稳定性。文中综述了降雨对干旱半干旱地区土壤微生物生物量、多样性的直接影响,以及其通过改变土壤水分、土壤空气和植被生长等对土壤微生物产生的间接影响,其中还可能伴随着其他因素的干扰,如土地利用方式、温度、海拔等。通过了解降雨格局变化对干旱半干旱地区土壤微生物的影响,可以更好地预测未来气候变化对该地区生态稳定性的影响。指出了降雨对干旱半干旱地区土壤微生物影响研究中存在的问题,并对未来研究进行了展望。     

Characterization of Corynelia uberata Fr., a putative fungal pathogen of Podocarpus falcatus in Ethiopian forests

Corynelia spp. are ascomycetes belonging to the order Coryneliales and are thought to be obligate parasites of trees in the Podocarpaceae. The aims of this study were to determine the disease intensity of Corynelia infection on Podocarpus falcatus in Ethiopian forests and verify the identity of Corynelia spp. from Ethiopia and other countries using morphological and molecular methods. Disease surveys were conducted in P. falcatus forest areas at Adaba‐Dodola, Bushoftu, Menagesha, Shashamane and Wondo Genet in Ethiopia between 2009 and 2011, and samples were collected for morphological and molecular studies. Additional dried specimens morphologically collected as C. uberata, C. portoricensis and C. tropica from Podocarpus species in Kenya, South Africa, Puerto Rico and New Zealand were also characterized. Morphologically, the South African specimen (F‐006479) of C. uberata had significantly larger ascospores when compared with the other specimens. There was a high sequence similarity (99–100%) in the internal transcribed spacer and 5.8S (ITS‐5.8S) region among the studied C. uberata sequences. Cloning and amplification of the insert spanning partial small ribosomal unit (SSU) and ITS‐5.8S regions of ribosomal DNA validated the unidentified ITS‐5.8S region as the sequence of C. uberata by inferring the reference sequence of SSU rDNA of C. uberata in GenBank. Both neighbour‐joining and/or maximum parsimony methods placed ITS‐5.8S and SSU rDNA sequences of Corynelia spp. at the basal position of the clade Eurotiomycetidae. C. uberata was found to be a potential pathogen on leaves, fruits and young stems of P. falcatus in Ethiopia.     

Effects of aspect and slope position on growth and nutritional status of planted Aleppo pine (<Emphasis Type="Italic">Pinus halepensis</Emphasis> Mill.) in a degraded land semi-arid areas of Jordan

Plantation of open grazing lands with Pinus halepensis are the most widely used practices in afforestation and reforestation in Jordan and other semi-arid areas around the Mediterranean Basin. The effect of aspect North (N), South (S), East (E) and West (W) and slope position (upper, middle, lower and valley bottom) on growth of planted Aleppo pine, nutritional status, plantation on restoring, needle, forest floor, nutrients concentration and soil properties were studied in Jubilee forest in Rakeen area, south of Jordan. Tree height was significantly higher in W than N, S and E aspects which mainly due to better moisture and nutritional conditions. All growth parameters were obtained on valley bottom were significantly higher than all aspect slope position combinations due to accumulation of run off and depositions from upper towards middle, and finally in lower slopes. In general, pH and EC were significantly reduced and soil organic matter was significantly improved by Allepo pine plantations compared to unplanted areas. West and N aspects as well as valley bottoms showed better soil physical and chemical properties.     

Mycosphaerella species associated with leaf disease of Eucalyptus globulus in Ethiopia

Eucalyptus spp. are among the most widely planted exotic trees in Ethiopia. Several damaging leaf pathogens are known from Eucalyptus spp. worldwide. Of these, Mycosphaerella spp. are among the most important, causing the disease known as Mycosphaerella leaf disease (MLD). Characteristic symptoms of MLD include leaf spot, premature defoliation, shoot and twig dieback. Recent disease surveys conducted in Ethiopian Eucalyptus plantations have revealed disease symptoms similar to those caused by Mycosphaerella spp. These symptoms were restricted to E. globulus trees growing in several localities in south, south western and western Ethiopia. The aim of this study was to identify the fungi associated with this disease. This was achieved by examining ascospore germination patterns, anamorph associations and sequence data from the Internal Transcribed Spacer (ITS) region of the rRNA operon, for representative isolates. Several different ascospore germination patterns were observed, suggesting that more than one species of Mycosphaerella is responsible for MLD on E. globulus in Ethiopia. Analysis of sequence data showed that three Mycosphaerella spp., M. marksii, M. nubilosa and M. parva were present. This is the first report of these three species from Ethiopia and represents a valuable basis on which to build further studies in the region.     

Growth rate of mosses and their environmental determinants in subalpine coniferous forests and clear-cuts at the eastern edge of the Qinghai-Tibetan Plateau, China

Mosses cover most of the forest floor of subalpine forests at the eastern edge of the Qinghai-Tibetan Plateau, the origin of many important rivers in China. They play a crucial role in preventing soil erosion and conserving large amounts of water thereby regulating the water budget of local ecosystems. This area has a harsh climate due to low temperatures and low air pressure at high elevations. But the temperature varies considerably during the growing season, which does not favor the regeneration of spruce seedlings on clear-cuts after logging. Leaves of mosses have a single layer of cells and are thus sensitive to environmental changes. This attribute may be useful for monitoring environmental conditions and guide artificial regeneration. The growth of mosses has never been studied in this area and the variables indicating their growth in the subalpine forest ecosystems still needs investigation. Growth rates of mosses have been rarely studied worldwide because the methods are time consuming and often inaccurate. A more simple and accurate method for measuring moss growth would help and encourage relevant research. We have found a method that will promote the efficiency in field measurements. Because of the special growth properties of mosses, the apical cell of branches initiates growth and the preceding leaves will stay where they were as the tips grow. Once mosses are marked with red oil at the tip of branches surrounded by young leaves, that portion of the branch above the marked leaves represents growth after labeling. Two plots, one in an old-growth spruce forest and another in a nearby clear-cut, were selected to label mosses in a subalpine area of western Sichuan Province during the growing season in 2001. The labeling was done on May 7 and measurements were made on August 7. Microclimate measurements on both sites were simultaneously carried out. Of the six mosses, five species were present in both the forest and on the clear-cut. One species, Entodon conncinus, was found only on the clear-cut. The growth rates of mosses varied among species and habitats. Hylocomium splendens grew the fastest while Dicranum assamicum had the slowest growth rate. Habitat conditions have a distinct effect on the growth of Hylocomium splendens, Dicranum assamicum and Thuidium lepidoziaceum and their growth rates were higher in forests than on clear-cuts. The growth rates of these mosses increased as their habitat approached the forest. Actinothuidium hookeri and Rhytidiadelphus triquetrus have moderate growth rates and is almost entirely independent of the type of habitat. The mosses can therefore be classified into habitat-sensitive and habitat-insensitive types. Analysis of microclimate characteristics shows that from May to July, the solar radiation level is lower and the environment is drier in the forest than those on the clear-cut. But a vapor pressure deficit (VPD) regime shows that the VPD in the morning is almost always lower in the forest than that on the clear-cut. With lower radiation and VPD, forests are more favorable to moss growth. For habitat-insensitive species, favorable micro-topographic factors might have offset the effect of habitat type. VPD is strongly correlated with the growth of mosses. Eco-physiological characteristics, such as poikilohydry, play an important role in the survival and growth of mosses under harsh climatic conditions. Temperature and humidity are two factors critical for seedling establishment in artificial regeneration processes in the subalpine areas of western Sichuan. Since the growth of mosses is a function of the two factors, moss growth rates can be used to indicate the more favorable habitats. Therefore, the status of moss growth can be used to indicate habitats potentially favorable to the growth of tree seedlings. __________ Translated from Journal of Plant Ecology, 2007, 31(3): 464–469 [译自: 植物生态学报]     

Effects of crown release on basal area growth rates of some broad-leaved tree species with different shade-tolerance

We compare three or four years effects of crown release on stem growth rates among four deciduous broad-leaved tree species,Fagus crenata, Quercus crispula, Magnolia obovata andAcer mono, in an even-aged coppice forest, central Japan. The crown release significantly improved relative growth rates for basal-area (RGR_BA) of the four species. However the effects of neighboring gap area (GAPA) on the RGR_BA differed among the species. The effects were significant forQ. crispula andM. obovata, indicating that growth rates of these two species increase with intensity of the crown release. In contrast, the RGR_BA ofF. crenata andA. mono were not correlated with the GAPA, suggesting that their growth rates are unrelated to the intensity. We considered that such differences among species were closely related to their photosynthetic characteristics of light use; less-tolerant species (Q. crispula andM. obovata) exhibit greater growth rates relative to the intensity of crown release than tolerant species (F. crenata andA. mono). Based on these results, we proposed implications for thinning practices in mixed forests of species with different shade-tolerance.