Biodiversity of Arbuscular Mycorrhizal (AM) fungi in mangroves of Goa in West India

Seventeen mangrove species of eight families at seven riverine and fringe habitats in Goa West India were surveyed for Arbuscular Mycorrhizal (AM) fungal diversity. Sixteen species were found to be mycorrhizal and one species showed no AM fungal colonization. AM root colonization was recorded at all seven sites and ranged from 6%-77%. Maximum root colonization was recorded in Excoecaria agallocha (77%) and minimum colonization in Avicennia marina (6%). Paris-type colonization was predominant at all sites. Auxiliary cells were recorded in roots of Acanthus ilicifolius, Ceriops tagal and Sonneretia alba. AM fungal root colonization and spore density varied by plant species and site. Site average spore density ranged from 1.84 spores·g-1 to 0.54 spores·g-1 of soil. In total, 28 AM fungal species of five genera, viz. Glomus, Acaulospora, Scutellospora, Gigaspora and Entrophospora, were recovered. Glomus was the dominant genus, three species of which were sporocarpic forms. Maximum site species richness (SR) ranged from 16 to 5. Species richness was maximum in A. ilicifolius where seven species of three genera were recovered. Based on relative abundance (RA) and isolation frequency (IF), two common species, viz. G. intraradices and A. laevis, were recovered from all seven sites.     

Arbuscular mycorrhizal association of indigenous agroforestry tree species and their infective potential with maize in the rift valley, Ethiopia

Tree species in agroforestry are important source of inoculum for companion agricultural crops. Agroforestry trees can serve as a source of Arbuscular mycorrhiza (AM) inoculants to intercropped annuals. We studied spore abundance, root colonization of Albizia gummifera (J.F. Gmel.) and Croton macrostachyus (Hochst Ex Del.) trees and their effect on colonization of maize. Soil and root samples were collected from field standing trees from under and outside the canopy of trees and maize crops in the main rainy season. The number of spore count was significantly higher under the canopy of A. gummifera (791/100 g of dry soil) and C. macrostachyus (877/100 g of dry soil) trees than outside the canopy (547 and 588/100 g of dry soil, respectively). The level of root colonization of C. macrostachyus (45 %) was higher than A. gummifera (41 %). Root colonization of maize crops grown under the canopy of A. gummifera and C. macrostachyus trees was significantly higher than outside the canopy (P < 0.001). Maize seedlings grown on non-sterilized soils collected under and outside the canopy of A. gummifera and C. macrostachyus trees recorded higher root colonization, plant height, shoot and root dry weight than grown on sterilized soils (P < 0.001). The percentage of AM colonized roots of Zea mays seedlings was significantly positively correlated with the number of spore counts for field soils. The rhizospheres of indigenous agroforestry perennial species are important source of inoculum for annuals. The integration of perennials and annuals in an agroforestry system enhances the maintenance of soil quality in the tropics.     

Arbuscular mycorrhizas and performance of Polylepis australis trees in relation to livestock density

Polylepis australis trees endemic to Argentina dominate the canopy of subtropical high altitude forests. Here, livestock rearing is the main economic activity and is suspect of the low performance of P. australis trees through direct and indirect effects which could include the reduction in arbuscular mycorrhizal fungi (AMF) and their benefit to trees. To elucidate the role of AMF, we compare plant performance indicators, arbuscular mycorrhizal (AM) colonization and AMF communities in 20 trees distributed in two areas of central Argentina which differed in livestock grazing intensity. The area with high livestock density presented more soil degradation and trees with a lower overall plant performance than the area with reduced livestock density. The AM colonization values of P. australis were considerably higher than reported for other tree species and the area with high livestock density had a lower proportion of arbuscules and higher proportion of hyphae, while vesicles and AM colonization – all structure considered together – did not differ between areas. Overall AMF spore number and of most species when considered separately was significantly higher in the area with high livestock density, suggesting a high tolerance and adaptation of AMF to livestock. We conclude that a reduction in livestock improves the performance of P. australis, that this improvement could be mediated by an increase in the proportion of arbuscules, but there does not appear to be any limitation in AM colonization or AMF spore number which could otherwise be limiting forest restoration.     

Tree species as hosts for arbuscular mycorrhizal and dark septate endophyte fungi

A survey of 35 tree species(belonging to 28 genera in 19 families) in Aliyar,South India was carried out to ascertain their arbuscular mycorrhizal(AM) and dark septate endophyte(DSE) fungal status.All the tree species examined had AM association.AM and DSE colonization is reported for the first time in 20 and 14 species respectively.Cooccurrence of AM and DSE was observed in 14(40%) tree species.The extent of DSE colonization was inversely related to the extent of AM fungal colonization.Six tree species had Arum-type,18 had intermediatetype and 11 had typical Paris-type AM morphology.AM fungal spore morphotypes belonging to 11 species in two genera were isolated from the rhizosphere soil.AM fungal spore numbers were not related to the extent of AM colonization and Glomus dominated spore diversity.AM association individually and along with DSE were found respectively in the 63% and 44% of the economically important tree species.The occurrence of AM and DSE fungal association in economically important indigenous tree species indicates the possibility of exploiting this association in future conservation programmes of these species.     

Impact of severe forest dieback caused by Phytophthoracinnamomi on macrofungal diversity in the northern jarrah forest of Western Australia

The relative diversity and abundance of different functional groups of macrofungi were investigated in the northern jarrah forest, a mediterranean climate sclerophyllous forest dominated by eucalyptus trees in Western Australia. We sampled paired sites that were either severely affected by dieback, a disease caused by Phytophthora cinnamomi which causes selective plant mortality, or unaffected by this type of forest decline. Macrofungi were sampled 3 times during the growing season along six 100 m × 2 m transects in these sites. Dieback-unaffected sites were found to have significantly different macrofungal floras than unaffected sites. Macrofungal abundance and diversity were approximately 1.5 times and 1.8 times greater respectively in dieback-unaffected sites than in severely affected sites. Dieback-affected sites had a similar diversity of saprotrophic and ectomycorrhizal fungi, whereas more fungal taxa on dieback-unaffected sites were mycorrhizal (>60%). Dung fungi were the most common saprophytes, especially in dieback-affected sites, but abundance data greatly overestimated the importance of these relatively small fungi. We concluded that vegetation changes linked to dieback had a negative effect on fungal community structure and biodiversity in the northern jarrah forest, in a similar manner to other forms of severe disturbance. Conversely, high tree mortality increased the abundance of wood decay fungi, at least in the short term. We expect that reductions in macrofungal species richness were indirectly linked to impacts on mycorrhizal host plants and saprotrophic substrates. Our data show that changes in vegetation composition had the greatest effect on ectomycorrhizal fungi, presumably due to their obligate symbiotic associations.     

Soil bacterial functional diversity is associated with the decline of Eucalyptus gomphocephala

This study investigates whether tree decline in Eucalyptus gomphocephala (tuart) is associated with the functional diversity of soil bacterial communities. We selected 12 sites with different stages of decline and assessed crown health [Crown density (CD), Foliage transparency (FT), Uncompacted live crown ratio (ULCR), Crown dieback ratio (CDR) and Epicormic index (EI)] and soil bacterial functional diversity based on Biolog EcoPlates™ incubation [Average well colour development (AWCD), Shannon diversity (H′), richness (S) and Shannon evenness (E)]. Crown health indices differed between sites with EI being the most robust indicator of decline in crown health followed by CDR and CD (P < 0.05). Soil bacterial indices collected at 0–10 and 20–30 cm soil depth between December (summer, dry season) and May (autumn, start of wet season) differed between sites (P < 0.05), and significant relationships between crown health indices, except ULCR, and all soil bacterial indices were observed. Principle component analysis (PCA) showed that a decrease in the utilization of carbohydrates, carboxylic acids, amino acids and amines by the soil bacterial communities correlated to sites with poor crown health, indicating some changes in physiological responses of bacterial groups with declining tree health. Using stepwise regression analyses, in the 0–10 cm soil layer in December, itaconic acid had a 46% contribution to the EI. Carboxylic acids, including itaconic acid, have a strong ability to solubilize soil minerals in calcareous soil, and these possibly increased the availability of soil mineral nutrients in the healthier sites compared to the declining sites, particularly in the dry season. In addition, lack of soil water in the declining sites limited soil bacterial diversity and was positively correlated with EI in the 0–10 cm soil layer in December. In conclusion, soil bacterial functional diversity has a strong relationship with tuart decline and the importance of soil microbes in tuart ecosystem health must be considered in the future.     

Arbuscular mycorrhizal fungi in the rhizosphere of Macaranga denticulata Muell. Arg., and their effect on the host plant

A fallow enriching tree, Macaranga denticulata Muell. Arg., has been shown to increase rice yield in a rotational shifting cultivation system in northern Thailand through increased accumulation of mineral nutrients. As arbuscular mycorrhizal (AM) fungi may play an important role in nutrient accumulation, AM fungi in the rhizosphere of M. denticulata and the effects of the indigenous soil inoculum on the host plant were investigated. The diversity and abundance of AM fungi were documented for the rhizosphere of M. denticulata in the field for two years. Based on morphology, 29 species of AM fungi were found in the rhizosphere of M. denticulata growing in farmers’ fields. Root colonization ranged from 63.5 to 81.5% in the first year and 68.7 to 79.9% in the second year of study. The highest spore density was observed at the end of the wet season. The effects of indigenous soil inoculum, and N and P fertilizers on the host plant were investigated in pots for four months. Inoculation with soil-containing AM fungi strongly increased plant growth and nutrient contents when P was limiting but N was applied. Application of N and P together strongly depressed root colonization and spore density of AM fungi, whereas applying them separately had much less effect. AM fungi may play an important role in nutrient accumulation in M. denticulata-rich fallow and thus in nutrient cycling that is beneficial to the maintenance of upland rice yield and sustainability of the rotational shifting cultivation system. This revised version was published online in June 2006 with corrections to the Cover Date.     

Diversity and abundance of arbuscular mycorrhizal fungi spores under different coffee production systems and in a tropical montane cloud forest patch in Veracruz, Mexico

We evaluate the arbuscular mycorrhizal fungi (AMF) community as measured by spores in different coffee production systems (at the depth of 0?C15?cm). In addition, we analyze the similarities between the AMF communities in coffee production systems and those that occur in a tropical montane cloud forest patch in order to evaluate the capacity of coffee production systems to preserve the native AMF community. We carried out four samplings in five coffee production systems representative of a vegetation structure gradient, and in a forest. From 120 soil samples, 33 morphospecies were detected. In all the sites, the dominant morphospecies were Glomus clarum and Glomus sp. 3. We found no significant difference in AMF spore richness between sites. Diversity was similar in most of the coffee production systems. Significant differences were only detected in spore abundance; during the dry season the forest, shaded traditional rustic system and shaded simple system presented the highest spore abundance. With the exception of one species exclusive to the forest, the coffee production systems all share the same AMF species as the forest. The coffee production systems with the greatest similarity to cloud forest were the shaded traditional rustic system and the shaded simple system. It is suggested that control of weeds and fertilization could be important factors influencing the composition and abundance of AMF spores in coffee production systems.     

香格里拉亚高山两种植被类型主要植物的丛枝菌根研究

以滇西北香格里拉亚高山地区生态严重退化的荒草坡植被类型和基本实现恢复的近原生林地植被类型中主要植物的丛枝菌根真菌(AMF)作为研究对象,对这些植物根系的AMF感染率及其根际土壤中的AMF孢子密度进行了调查研究。结果表明,荒草坡的10种植物和近原生林地的9种植物,均形成典型的丛枝菌根(AM)。荒草坡和近原生林植物根际土壤中的平均孢子密度分别为674±221(SE)个/100g土和290±72个/100g土。单因素方差分析表明,两植被类型的主要植物在根系AMF菌丝感染率以及根际土壤中AMF孢子密度方面的差异都极显著。同种植物在近原生林地具有较高的AMF感染率,而根际土壤中的孢子密度则是在荒草坡为高。相关性分析表明,所调查植物的根系AMF菌丝感染率与根际土壤中的AMF孢子密度间不存在相关性。     

New insights into the survival strategy of the invasive soilborne pathogen Phytophthora cinnamomi in different natural ecosystems in Western Australia

Despite its importance as one of the most notorious, globally distributed, multihost plant pathogens, knowledge on the survival strategy of Phytophthora cinnamomi in seasonally dry climates is limited. Soil and fine roots were collected from the rhizosphere of severely declining or recently dead specimens of 13 woody species at 11 dieback sites and two dieback spots and from healthy specimens of five woody species at four dieback‐free sites in native forests, woodlands and heathlands of the south‐west of Western Australia (WA). Phytophthora cinnamomi was recovered from 80.4, 78.1 and 100% of tested soil, fine root and soil–debris slurry samples at the 11 dieback sites, in some cases even after 18‐month storage under air‐dry conditions, but not from the small dieback spots and the healthy sites. Direct isolations from soil–debris slurry showed that P. cinnamomi colonies exclusively originated from fine roots and root fragments not from free propagules in the soil. Microscopic investigation of P. cinnamomi‐infected fine and small woody roots and root fragments demonstrated in 68.8, 81.3 and 93.8% of samples from nine woody species the presence of thick‐walled oospores, stromata‐like hyphal aggregations and intracellular hyphae encased by lignitubers, respectively, while thin‐walled putative chlamydospores were found in only 21.2% of samples from five woody species. These findings were confirmed by microscopic examination of fine roots from artificially inoculated young trees of 10 woody species. It is suggested that (i) the main function of chlamydospores is the survival in moderately dry conditions between consecutive rain events and (ii) selfed oospores, hyphal aggregations, and encased hyphae and vesicles in infected root tissue of both host and non‐host species are the major long‐term survival propagules of P. cinnamomi during the extremely dry summer conditions in WA.     

丛枝菌根真菌对在含砷土壤中的云南石梓(Gmelina arborea)生长的影响(英文)

孟加拉东南部土壤中的砷含量很高,不仅威胁人的健康,而且对土壤也有破坏作用。云南石梓(Gmelina arborea)在孟加拉是个快速生长的树种,也是含砷土壤中的潜力树种。研究评价了含砷试验土中丛枝菌根真菌对云南石梓(Gmelina arborea)生长的影响。播种前,四种不同浓度的砷(10mg·kg-1、25mg·kg-1、50mg·kg-1和100mg·kg-1)被加入到试验土中。记录生长参数,如,植物的根、苗鲜重、干重、冠幅径、根长和苗高、根瘤菌和孢子菌群落。菌根植株较非菌根植株生长好。与其它含砷量高的土壤中植株的生长情况相比,在含砷量为10-mg·kg-1的土壤中,菌根植株和菌根生长效果最佳,菌根植株生物量最高。随着砷浓度的增加,种苗生长,根瘤菌和孢子菌群落均明显降低p0.05)。与非菌根植株比较,菌根植株高生长增加了40%,生物量增加了2.4倍。研究表明,根瘤菌接种可以减少有害土壤中的云南石梓(Gmelina arborea)的初生长的影响。     

Floristic composition and soil characteristics of tropical freshwater forested wetlands of Veracruz on the coastal plain of the Gulf of Mexico

We studied the influence of geomorphological setting and soil properties on the vegetation structure, composition and diversity of five forested coastal wetlands in Veracruz on the Gulf of Mexico. These swamps are located on floodplains and in dune depressions. We recorded 109 woody and herbaceous species. The most frequent species were the trees Pachira aquatica, Annona glabra, Diospyros digyna and Ficus insipida subsp. insipida, the lianas Dalbergia brownei and Hippocratea celastroides and the hemi-epiphyte Syngonium podophyllum. The Shannon-H diversity index varied from 2.659 to 3.373, density from 1750 to 2289 stems ha⁻¹ and basal area from 32.7 to 76.42 m² ha⁻¹. The classification analysis defined two groups: one corresponded to forested wetlands along the floodplain (Apompal, Cienaga, Chica) and the other included Mancha and Salado, in dune depressions. PCA ordination of soil parameters during the rainy season explained 67.0% and during the dry season 69.1% of the total variance. In the rainy season Mancha and Salado samples remain close together because they have lower Mg, Na, K, % Total C and % Total N values. Apompal and Chica samples remain close to each other because of their high levels of % Total C, % Total N, Mg, Na and high soil water content. Cienaga samples are separated from the others because of high values of P, Ca and Eh as well as high water levels. In general, soil parameter ordination during the dry season showed that redox potential, P, water level and water content decreased in the forested wetlands and Na values increased in Chica. The soil textures identified were clay, sandy clay loam, sandy loam and clay loam; clay texture dominated alluvial processes in the floodplain (e.g., Cienaga). The forested wetlands in the floodplains had similar vegetation and the same happened in the dune depressions but soil characteristics were more variable in both cases. Plant diversity in floodplains tends to be relatively high, and the presence of adjacent tropical forests probably increases its richness, except in cases in which there are stressing factors, such as salinity. The forested wetlands studied showed dominant floristic elements, which extend north into Florida such as A. glabra and Ficus aurea. Other dominant elements such as P. aquatica are also found in Central and South America. The forested wetlands studied are subjected to continuous deforestation to transform the land into farming or ranching activities, this being a common practice throughout the distribution range of these forests.     

Root carbohydrates and aspen regeneration in relation to season of harvest and machine traffic

Season of harvest has often been suggested as a driver for the erratic success of aspen (Populus tremuloides) sucker regeneration, partially due to root carbohydrate reserves and soil conditions at the time of harvest. A field experiment in western Manitoba, Canada, assessed root suckering and root carbohydrates of aspen in response to season of harvest and machine traffic. Six sites (120 m × 120 m) were selected within two large mature aspen stands slated for summer harvest. Plots (50 m × 50 m) were hand-felled (without machine traffic) in mid-summer, late summer, winter, and one plot was left uncut as a control. Season of cut with no traffic had no effect on sucker density, height or leaf dry mass per sucker. During the dormant season, root starch reserves were highest in the winter cut plots, however, just prior to suckering, this difference in carbohydrate reserves among the three seasons of harvest disappeared and by the end of the first growing season root reserves in all three seasons of cut had recovered to near control levels. Adjacent plots that were conventionally harvested in the summer and impacted by logging traffic had similar sucker densities but had 19% less height growth of suckers and 29% less leaf dry mass per sucker compared to suckers in plots harvested at the same time without traffic. After one growing season, root carbohydrate levels were similar whether or not machine traffic was used; however, the reduction in leaf dry mass in plots with machine traffic could have negative implications for carbohydrate accumulation and growth. The study suggests that the phenological state of the mature aspen plays a very small role in aspen regeneration and that harvesting practices and site conditions are likely the main drivers of aspen regeneration success.     

Arbuscular mycorrhizae and ectomycorrhizae in native tree legumes in Uruguay

The level of colonization by ectomycorrhizae (ECM) and arbuscular endomycorrhizae (AM) of 23 species of native trees and shrub legumes was studied. Root samples were obtained from different regions of Uruguay. Colonization level was determined by observing AM fungal structures (hyphae, arbuscules, vesicules) in stained root segments. The number and morphological type of spores were determined in 100 g of rhizosphere soil. Ectomycorrhizal colonization was evaluated by direct and microscopic observation of root tips. All species had a high level of AM colonization. In Papilionoideae colonization varied between 62% and 78%, in the Mimosoideae between 18% and 69% and in the Caesalpinioideae the variation was larger (6–74%). These results show a significant presence of fungi that form arbuscular mycorrhizae in our soils. The number of spores forming AM in rhizosphere soil (280–l.620 spores/100 g of dry soil) was also highly relative to references for other leguminous trees. Spores were grouped in three principal morphological types Acaulospora, Glomus and Sclerocystis. Presence of ECM fungi was evident only when observed under the microscope. 26% of the plant species exhibited this type of mycorrhizae, reaching a maximal value of 36% in Mimosoideae. Only six plant species exhibited both types of mycorrhizae. Dual colonization could help in the colonization of poor soils and for their use in agroforestry systems.     

Effects of arbuscular mycorrhizal fungi on leaf solutes and root absorption areas of trifoliate orange seedlings under water stress conditions

The effects of the arbuscular mycorrhizal (AM) fungus Glomus mosseae on plant growth, leaf solutes and root absorption area of trifoliate orange (Poncirus trifoliata (L.) Raf.) seedlings were studied in potted culture under water stress conditions. Inoculation with G. mosseae increased plant height, stem diameter, leaf area, shoot dry weight, root dry weight and plant dry weight, when the soil water content was 20%, 16% and 12%. AM inoculation also promoted the active and total absorption area of root system and absorption of phosphorus from the rhizosphere, enhanced the content of soluble sugar in leaves and roots, and reduced proline content in leaves. AM seedings had higher plant water use efficiency and higher drought tolerance than non-AM seedlings. Effects of G. mosseae inoculation on trifoliate orange seedlings under 20% and 16% soil water content were more significant than under 12% soil water content. AM infection was severely restrained by 12% soil water content. Thus, effects of AM fungi on plants were probably positively related to the extent of root colonization by AM fungi. The mechanism of AM fungi in enhancing drought resistance of host plants ascribed to greater osmotic adjustment and greater absorption area of root system by AM colonization. __________ Translated from Journal of Plant Physiology and Molecular Biology, 2005, 30(5): 583–588 [译自: 植物生理与分子生物学报, 2005, 30(5): 583–588]     

Factors controlling deadwood availability and branch decay in two Prosopis woodlands in the Central Monte, Argentina

Deadwood is an important resource commonly used by inhabitants in arid lands. However, the low wood productivity and the presence of multi-stemmed trees restrict the use. Prosopis flexuosa woodlands are protected and inhabited by pastoralists who have land rights to use natural resources. As in other forests in the world, dead branches are the most commonly used. The factors causing the death of branches these trees are unknown. As P. flexuosa is a highly heliophilous species, branch mortality may depend on the growth habit and orientation of dry branches under the tree crown. With the participation of inhabitants, we assessed the present availability of deadwood in two Prosopis woodlands of different structure (semi-closed and open woodland), and evaluated the formation of deadwood in terms of shape and cardinal location of dry branches under the crown. We developed and compared regression models to estimate the amount of deadwood for erect, semi-erect and decumbent trees, and for the north and south areas under the crown (n = 120 trees). In addition, to determine the period of growth decline and the factors determining branch mortality, we compared annual radial increment between live and dead branches (n = 30 trees; 10 for each tree shape). The total amount of deadwood in adult Prosopis trees is higher in the semi-closed than in the open woodland (8.6 and 4.4 Tn ha⁻¹, respectively). Only tree size determined the amount of deadwood present in each Prosopis tree, since we found no evidence related to the shape of the tree or the position of dry branches in the canopy. Branch decay was a large process of 18-20 years, and branch death appears to be the result of the action of climatic factors (dry period). The results suggest that the use of deadwood by the desert inhabitants is a tool that can potentially be used; however, the use of this resource taking into account the generation rates of deadwood has not been developed in arid lands. These practices at appropriate sites can contribute to a sustainable management of these woodlands, including the removal of deadwood in a model of local management on a site where potential productivity is relatively low.     

Plant limiting nutrients in Andean-Patagonian woody species: Effects of interannual rainfall variation,soil fertility and mycorrhizal infection

Andean-Patagonian forests are especially interesting for the study of N and P limitation because they receive minimal atmospheric pollution, have little influence of vascular N-fixing species, and grow on volcanic soils that retain P. In a previous study of 10 woody species (four broad-leaved deciduous species, three broad-leaved evergreens and three conifers) conducted during an exceptionally dry year in NW Patagonia, and on the basis of nutrient resorption efficiency and proficiency, we suggested that N was the most limiting nutrient except for the broad-leaved evergreen Lomatia hirsuta. In the present work, we compared patterns of nutrient limitation during a dry and a wet year, quantified the percentage of mycorrhizal infection, and related mycorrhizal behavior and nutrient limitation to soil fertility. We used N and P concentrations in green leaves as indicators of nutrient requirements, and N and P concentrations in senescent leaves (resorption proficiency) and the N/P ratio in green leaves as indicators of nutrient limitation. We also determined leaf mass area (LMA) and lignin concentration as indicators of structural and chemical defences. From previous works, the following soil fertility indicators were included: pH, organic C, total N, exchangeable cations, Olsen-P, potential N mineralization (pNmin) and N retained in microbial biomass (N-MB). Nitrogen, P and lignin concentrations in green and senescent leaves did not differ significantly between the dry and the wet year either by species or by functional groups. Most species behaved as N-proficient and P-non-proficient; this together with values of foliar N/P ratios lower than 14–16 confirmed N limitation in these forests. The only species limited by P but not by N was L. hirsuta (1.0–1.1% N in senescent leaves, N/P ratio = 21–23), a non-mycorrhizal species with cluster roots. The lack of P limitation in the other species was probably related to the high percentages of infection with arbuscular mycorrhizae (80–90% in Maytenus boaria and the conifers Araucaria araucana, Austrocedrus chilensis and Fitzroya cupressoides), and ectomycorrhizae (73–79% in five Nothofagus species). Nitrogen and P requirements were positively correlated among themselves and negatively with lignin and LMA. Soil fertility was positively correlated with nutrient requirements and negatively with lignin and LMA. Conifers had lower N and P requirements, higher LMA, lower foliar N/P ratio and grew on soils of lower soil N dynamics (lower pNmin and N-MB) than ectomycorrhizae-associated species.     

Water use by Tabor and Kermes oaks growing in their respective habitats in the Lower Galilee region of Israel

We estimated water use by the two main oak species of the Lower Galilee region of Israel—Tabor (Quercus ithaburensis) and Kermes (Quercus calliprinos)—to develop management options for climate-change scenarios. The trees were studied in their typical phytosociological associations on different bedrock formations at two sites with the same climatic conditions. Using the heat-pulse method, sap flow velocity was measured in eight trunks (trees) of each species during a number of periods in 2001, 2002 and 2003. Hourly sap flux was integrated to daily transpiration per tree and up-scaled to transpiration at the forest canopy level. The annual courses of daytime transpiration rate were estimated using fitted functions, and annual totals were calculated. Sap flow velocity was higher in Tabor than in Kermes oak, and it was highest in the youngest xylem, declining with depth into the older xylem. Average daytime transpiration rate was 67.9 ± 4.9 l tree⁻¹ d⁻¹, or 0.95 ± 0.07 mm d⁻¹, for Tabor oak, and 22.0 ± 1.7 l tree⁻¹d⁻¹, or 0.73 ± 0.05 mm d⁻¹, for Kermes oak. Differences between the two oak species in their forest canopy transpiration rates occurred mainly between the end of April and the beginning of October. Annual daytime transpiration was estimated to be 244 mm year⁻¹ for Tabor oak and 213 mm year⁻¹ for Kermes oak. Adding nocturnal water fluxes, estimated to be 20% of the daytime transpiration, resulted in total annual transpiration of 293 and 256 mm year⁻¹ by Tabor and Kermes oaks, respectively. These amounts constituted 51% and 44%, respectively, of the 578 mm year⁻¹ average annual rainfall in the region. The two species differed in their root morphology. Tabor oak roots did not penetrate the bedrock but were concentrated along the soil–rock interface within soil pockets. In contrast, the root system of Kermes oak grew deeper via fissures and crevices in the bedrock system and achieved direct contact with the deeper bedrock layers. Despite differences between the two sites in soil–bedrock lithological properties, and differences in the woody structure, annual water use by the two forest types was fairly similar. Because stocking density of the Tabor oak forests is strongly related to bedrock characteristics, thinning as a management tool will not change partitioning of the rainfall between different soil pockets, and hence soil water availability to the trees. In contrast, thinning of Kermes oak forests is expected to raise water availability to the remaining trees.     

Vegetation cover density and disturbance affected arbuscular mycorrhiza fungi spore density and root colonization in a dry Afromontane forest,northern Ethiopia

Arbuscular mycorrhiza fungi(AMF) are vital in the regeneration of vegetation in disturbed ecosystems due to their numerous ecological advantages and therefore are good indicators of soil and ecosystem health at large. This study was aimed at determining how the seasonal, vegetation cover density, edaphic and anthropogenic factors affect AMF root colonization(RC) and spore density(SD)in Desa'a dry Afromontane forest. AMF RC and SD in the rhizosphere of five dominant woody species, Juniperus procera, Olea europaea, Maytenus arbutifolia, Carissa spinarum and Dodonaea angustifolia growing in Desa'a forest were studied during the rainy and the dry seasons in three permanent study vegetation cover density plots(dense, medium, and poor). Each plot(160 x40 m~2) has two management practices(fenced and unfenced plots) of area. A 100 g sample of rhizosphere soil from moisturefree composite soil was used to determine spore density.Spore density ranged from 50 to 4467 spores/100 g soil,and all species were colonized by AMF within a range of 4–95%. Glomus was the dominant genus in the rhizosphere of all species. Vegetation cover density strongly affected SD and RC. The SD was significantly higher(p 0.05) in the poor vegetation cover density than in the other two and lowest in the dense cover; root colonization showed the reverse trend. Management practices significantly(p 0.05) influenced AMF SD and RC, with the fenced plots being more favoured. Seasons significantly(p 0.05) affected RC and SD. More RC and SD were observed in the wet period than the dry period. Correlating AMF SD and RC with soil physical and chemical properties showed no significant difference(p 0.05) except for total nitrogen. Disturbance, vegetation cover density, season and total nitrogen are significant factors that control the dynamics and management interventions to maintain the forest health of dry Afromontane forests.     

Influence of coarse woody debris on herpetofaunal communities in upland pine stands of the southeastern Coastal Plain

Coarse woody debris (CWD) is thought to benefit herpetofauna in a variety of ways including serving as feeding sites, providing a moist environment, and providing protection from temperature extremes. We investigated the importance of CWD to amphibian and reptile communities in managed upland pine stands in the southeastern United States Coastal Plain during years 6 and 7 of a long-term study. Using a randomized complete block design, 1 of the following treatments was assigned to 9.3-ha plots: removal (n = 3; all downed CWD ≥10 cm in diameter and ≥60 cm long removed), downed addition (n = 3; five-fold increase in volume of down CWD), snag (n = 3; 10-fold increase in volume of standing dead CWD), and control (n = 3; unmanipulated). Herpetofauna were captured seasonally using drift-fence pitfall trapping arrays within treatment plots. We compared abundance, diversity, and richness of anurans, salamanders, lizards, and snakes using analysis of covariance with topographic variables (slope, elevation, aspect, and distance to nearest stream) included as covariates. We captured 355 amphibians and 668 reptiles seasonally from January 2007 to August 2008. Abundance, species richness, and species diversity were similar among treatments for anurans, salamanders, and lizards. Snake abundance, species richness, and diversity were higher in removal than downed addition plots. Anuran abundance increased as distance to nearest stream decreased. The majority of species captured during this study are adept at burrowing into the sandy soils of the region. Lack of reliance on CWD may be the result of herpetofaunal adaptation to the longleaf pine (Pinus palustris) ecosystem that historically dominated the upland areas of the study area.