Aims We studied root morphology across the first five branch orders of 20 hardwood tree species from secondary forest in northeastern China. Our objectives were to determine how root morphology changes across root branch orders and how such variations of root morphology differ between ectomycorrhizae (EM)-dominated and arbuscular mycorrhizae (AM)-dominated fine roots.

Methods The fine roots were sampled in secondary forest in August 2006. We chose a random location in a plot under a randomly chosen individual tree and used a shovel to remove six soil blocks, 20 cm×20 cm×10 cm depth, from which the intact root segments were collected and placed in a Whirl-pac bag on ice in a cooler and then transported to the lab and frozen for dissection at a later date. In the laboratory, we dissected each individual root by branching order beginning with the distal end of a root system. After the dissection, we verified the type of mycorrhizal infection by staining and direct microscopic observation and determined diameter, length, and specific root length (SRL) of a given order.

Important findings Root diameter and length increased, and SRL decreased from the first to fifth order roots, except in Ulmus pumila, Acer ginnala, Alnus sibirica, A. mandshurica and U. laciniata, in which first order roots had larger (or equal) diameter and lower SRL compared to second order roots. The first three order roots accounted for 80% of the total length, suggesting that lower order roots would have similar physiological functions despite their differences in morphology. Eleven species were EM, and nine were AM. Average diameter, length and SRL of each root order were larger for AM than EM species.

Aims Fine root decomposition is a major pathway of carbon and nutrient cycling in terrestrial ecosystems. Litterbag studies change the environmental conditions of root decay, so we employed a minirhizotron technique. Our objectives were to: 1) compare fine-root decomposition time and rate between ash (Fraxinus mandshurica) and larch (Larix gmelinii) in the same site, 2) analyze the effect of root diameter and root order on fine root decomposition and 3) investigate patterns of fine root decomposition in different soil depths.

Methods In October 2003, we established three 20 m × 30 m plots in each plantation, and randomly installed six minirhizotron tubes. From April 2004 to October 2006, video images were collected at approximately two-week intervals during the growing season. The interval from date of root death to disappearance was defined as decomposition time. Video images were digitized via RooTracker software (NC, USA). Kaplan-Meier method in survival analysis was used to generate cumulative remaining rate and median root decomposition time (MRDT), and factors of tree species, diameter, root order and soil depth were compared by logrank test.

Important findings Cumulative remaining rate of fine-roots in both species decreased gradually with time, with the decrease significantly faster for larch than ash (p<0.001).MRDT of larch was (82±7) d compared with (317±28) d for ash. TheMRDT of both species differed in three diameter classes (≤0.3, 0.3-0.6 and >0.6 mm). The finest roots (≤0.3 mm) of both ash and larch decayed slower than the other two diameter classes; however, only theMRDT of ash decreased systematically with increasing root diameter. With increasing root order, the cumulative remaining rate of both species increased significantly (p<0.05), resulting in a delay time of 82 d and 58 d ofMRDT for higher order compared with first order in larch and ash roots, respectively. The fine-root cumulative remaining rate of both species showed similar pattern among soil depths, which at 0-15 cm depth was significantly less than 15-30 and 30-45 cm (p<0.01). This study suggested that fine-root decomposition is a species-specific process, mutually controlled by internal factors (e.g., diameter) and external factors (i.e., soil depth). Decay of fine roots is faster than previous reported.

Aims Fine roots are the primary organs for nutrient and water uptake in trees. The growth and turnover of fine roots significantly influence productivity and matter cycles in forest ecosystems. Our objective was to elucidate the basic structure, function and allocation of fine roots in Phellodendron amurense.

Methods We made paraffin slices stained by safranin and fast green to observe anatomical structures (such as diameter, cortex, number of passage cells, development of vascular bundle, mycorrhizae of roots, etc.) of the first five orders of roots of P. amurense. Bright-light and fluorescence microscopes were used to observe and take photos.

Important findings Root diameter (R), vascular bundle diameter (V) and V/R increased as root order increased. The thickness and layers of cortex were similar in the first three orders. Few cortical cells were in fourth-order roots and almost none in fifth-order roots. There were higher mycorrhizae infections in the first three order roots than the last two orders, and the later had almost no fungi. Primary growth occurred in all first- and second-order roots, and secondary growth occurred in all fourth and fifth order roots. Some third-order roots had only primary growth, but some had secondary growth with inconsecutive phellogen. All results suggested that the ability of roots to absorb nutrients and water decreased but transport ability and longevity increased as root orders increased. According to the relationships among anatomical characteristics, diameters and root orders, the fine roots of P. amurense should be involved in the first three orders at most; these have passage cells but lack successive phellogen and have diameters less than 0.8 mm.

Aims Fine roots play an important role in plant functioning and ecosystem carbon and nutrient cycling. We studied root diameter across the first five branch orders of 45 tree species from three forest ecosystems in China, in order to: 1) examine fine root diameter distributions of various tree species in temperate, subtropical and tropical forests in China; 2) identify factors influencing the variations in root diameter; and 3) analyze the relationship between branch order and diameter.

Methods Fine roots of 45 tree species were sampled by branch order in temperate, subtropical and tropical forests in summers of 2006 and 2007. Study sites included Beijing Baihua, Shanxi Guandi, Shanxi Zhongtiao and Guangdong Dinghu Mountains and Yunnan Xishuangbanna. We excavated soil blocks of 20 cm×20 cm×10 cm to sample intact fine root branches containing at least the first five branch orders, dissected these intact root branches by order and measured the diameters of individual roots of each order.

Important findings Root diameter increases from first to fifth order, although the diameter of the same order varied markedly among species. On average, the diameter of tree species in the three forests is temperate < subtropical < tropical. Variations in diameter among species were different for the three forests: temperate < subtropical ≤ tropical. Branch order can explain 52% of diameter variations, species 33%, ecosystem 7% and life form 2%.

Aims Taxodium ascendens is a flood-tolerant tree species. It is important to understand the mechanisms of flood-tolerance by means of study on the root changes of T. ascendens in flooded conditions.

Methods Based on the investigation of the roots of T. ascendens plantations in 17 year-old in Lixiahe wetland, Jiangsu Province, China, the ecological adaptations of the roots were analyzed in the different water table sites divided into three groups: high water table site (HWS, the site was flooded from June to October every year, and the depth of the mean water table in each year was -5 cm), middle water table site (MWS, the site was flooded from August to September every year, and the depth of the mean water table in each year was -18 cm), and low water table site (LWS, the site was not flooded all the time, and the mean water table in each year was -41 cm).

Important findings In HWS, T. ascendens formed aerating roots which were very long and thin, and attached on the tree stem or in the outer epidermis or in the crack of tree bark; In the MWS, T. ascendens formed knee roots which were (7.9±2.2) cm in diameter, (7.7±2.7) cm in height; AlthoughT. ascendens also formed the knee roots in LWS, they were smaller than in MWS. The belowground biomass and the aboveground biomass of the trees were in the order of HWS<MWS<LWS. However, the ratios of the belowground biomass and the aboveground biomass were in the order of LWS<MWS<HWS. It was suggested that althoughT. ascendens was a flood-tolerant tree species, the biomass growth decreased in flooding conditions, especially the aboveground biomass growth obviously decreased in flooding conditions. The ratios of the diameter at ground and at breast height in HWS, MWS and LWS was 2.66±0.11, 2.08±0.10 and 1.75±0.08, respectively. The volume weight of underground roots decreased if the trees were waterlogged for long time. But the volume weight of the aerating roots and the knee roots were greater than that of the underground roots. The concentrations of iron and manganese in fine roots in HWS and MWS were significantly higher than in LWS. However, the concentrations of iron and manganese in leaves were no difference between HWS, MES and LWS. The mean respiration rate of the each knee root was 2.1~2.5 mgCO₂·h^-1 in August and September, 0.7~0.9 mgCO₂·h^-1in June and November, and 0.4 mgCO₂·h^-1in March, respectively. The moles of oxygen absorption was 4.6 times more than that of carbon dioxide flux by knee roots. It appeared that the oxygen absorbed by knee roots was not only supplied to knee roots respiration, but also supplied to underground roots respiration. It was suggested that T. ascendens with high flood-tolerance was due to forming the aerating roots and knee roots, promoting the diameter growth of stem, and decreasing the volume weight of roots in the flooding sites for improving the ventilation condition of roots.

Aims Root architectural properties can be divided into geometric properties and topological properties. Topological properties are believed to influence the efficiency and costs of resource exploitation in terms of carbon required for root segment construction.

Methods We excavated by shovel the coarse root systems of three natural species of the Taklimakan Desert area (Tamarix taklamakanensis, Calligonum roborovskii and Apocynum venetum) and analyzed aspects of root architecture, including topology, link length, diameter and scaling relations.

Important findings Root distribution was dominated by horizontal roots. Root branching pattern differed by species, withtopology the shrub T. taklamakanensistending to be dichotomous (q_a=0.15, q_b=0.09, TI=0.658) and C. roborovskii(q_a=0.52, q_b=0.38, TI=0.86) and nd the forbsthe root systems topology. The result indicated that A. venetum (q_a=0.43, q_b=0.35, TI=0.83) being herringbone-like. The lengths of links were very long for all species, with the shortest being 1.12 m. The different architectural strategies could be explained in terms of cost-benefits relations and efficiency in soil resource exploration and exploitation. We concluded that the differences and similarities of root architecture reflected strategy in exploitation and exploration. We also tested the “pipe-stem” theory, essentially dating back to Leonardo da Vinci, that underlies many models and found that our measurement data conformed with it. The ratio of the sum of root cross-sectional areas after and before bifurcation was constant with change of root diameters, so we proposed that the scaling coefficient1268/img_1.wmf10.010.0is the universal feature of root architecture.

Aims Root systems are important in carbon and nutrient cycling in forest ecosystem. There is much research on vertical distribution and seasonal dynamics of fine root biomass; however, horizontal distribution and seasonal dynamics at different horizontal distances remain poorly understood. Our objectives are to determine how fine root biomass and seasonal dynamics of fine root biomass change with horizontal distance.

Methods The study was conducted in a 28-year-old Larix principis-Rupprechtii plantation in Guandi Mountain (110°30′ E, 37°28′ N) in Shanxi Province, China. Soil cores (30.0 cm depth, 7.0 cm diameter) were taken in May, July, September and October,2004, at different horizontal distances (100, 50 and 20 cm) from the stem. Soil cores were separated into 3 sections, 0-10, 11-20 and 21-30 cm. Fine roots (≤2 mm) were separated into live and dead, and live fine roots were classified into two categories, ≤1 and 1-2 mm. Roots were dried at 80^oC to constant mass for weighing.

Important findings The biomass of fine roots was 244.20, 209.45 and 221.03 g·m^-2at 100, 50 and 20 cm, respectively, and differences were not statistically significant (p>0.05). Total fine root biomass changed from 169.67 to 263.09 g·m^-2. Differences were larger at 0-10 cm depth than at 11-20 and 21-30 cm. Seasonal dynamics of fine root biomass changed significantly in the 0-10 cm layer (p<0.05), and it changed more at the 100 and 20 cm distances rather than at 50 cm. Horizontal differences in fine roots likely resulted from tree crowns causing heterogeneous illumination, soil water, temperature and nutrients. The study indicates that combined and integrated horizontal distribution factors should be considered in research on spatial distribution and seasonal dynamics of fine roots.

Aims Total belowground carbon allocation represents an important carbon flux in forest ecosystems and is closely related to carbon sequestration. Knowledge of how it changes with stand age in forest plantations is essential for carbon accounting and carbon management. Our primary objective is to elucidate changes in total belowground carbon allocation in a Chinese fir (Cunninghamia lanceolata) chronosequence.

Methods We selected an age sequence of 7 (young), 16 (middle-age), 21 (pre-mature), 41 (mature) and 88 year (old-growth) Chinese fir plantations with similar site conditions in Nanping, Fujian. Fine root production was determined by sequential soil coring, root respiration by trenching, current annual increment of tree biomass by allometric equations and annual litterfall by litter traps.

Important findings Annual fine root production (P_fr) was relatively high and statistically similar prior to the middle-age stage, but decreased in the following stages. The ratio of P_fr/litterfall decreased with stand age. Root respiration, which was linearly correlated to living fine root biomass, was lower in old-growth forest than in other forests. Total belowground carbon allocation (TBCA) was higher in middle-age and pre-mature forests than in young and mature forests and was lowest in old-growth forest. The ratio of aboveground net primary production to TBCA was higher in middle-age, pre-mature and mature forests than in young and old-growth forests. Root carbon use efficiency decreased with stand age.

Aims A living fossil is the nearest extant equivalent of an extinct species. Our objective is to utilize the biomass and productivity of living-fossil ecosystems to estimate the evolutionary trend in carbon sequestration capacity of terrestrial ecosystems.

Methods We investigated biomass and productivity of a living-fossil tree fern (Alsophila spinulosa) ecosystem in Sichuan Province of China using standard tree sampling methods.

Important findings The biomass and productivity of this living-fossil ecosystem ((36.151 ± 8.159) Mg C·hm ^-2 and (2.535 ± 0.174) Mg C·hm ^-2·a^-1, respectively) were smaller than that in current gymnosperm- or angiosperm-dominated ecosystems. This provides insight into the evolutionary trend in paleo-ecosystem carbon sequestration capacity and, hence, into understanding global carbon balance.

Aims In light of increasing interest in understanding carbon fluxes of terrestrial ecosystems under changing climate and escalating human influences, our study examined the dependence of carbon fluxes on abiotic and biotic factors and explored the effects of conversion of grassland to cropland on ecosystem C fluxes.

Methods Our study was carried out in Duolun (42^o02′ N, 116^o17′ E; 1 350 m asl), a semiarid agriculture-pasture transition region in southeastern Inner Mongolia, China. We used the chamber method during the growing season.

Important findings There was no difference in net ecosystem exchange of carbon dioxide (NEE) between wheat field and steppe at the beginning of the growing season. NEE of wheat field became higher than that of steppe in late June. No differences were found between the two ecosystems from mid-July to August 1st. NEE of wheat field became significantly lower than that of steppe starting in mid-August. During the growing season, the maximum of NEE in steppe was -11.26 µmol CO ₂·m^-2·s^-1, while that in wheat field was -12.29 µmol CO ₂·m^-2·s^-1. Mean NEE in steppe (-5.33 µmol CO ₂·m^-2·s^-1) was a little lower than that in wheat field (-7.66 µmol CO ₂·m^-2·s^-1). Leaf area index (LAI) was the main factor controlling NEE of the two ecosystems. Poor soil nutrient levels also might limit NEE in these ecosystems. Because of characteristics of wheat, the sensitivity of NEE response to LAIwas lower in wheat field than steppe in the middle and late growing season. Lower soil volume water content (10 cm depth) in wheat field limited total ecosystem respiration (TER) and decreased the sensitivity of TER to temperature.

Aims Recent studies, including field measurements, satellite-derived vegetation indices and simulations from a dynamic vegetation model, have demonstrated that global warming is influencing plant growth and phenology. Changes in plant phenology have considerable consequences for ecosystem function, but information on responses of plant phenology to climate change is lacking, especially in a community setting. Therefore, to accurately predict the future responses of plants to climate variation, a through understanding of plant phenological cycles and their relationships to light, temperature and precipitation is required.

Methods We compiled a phenological calendar with 31 phenophases of budding, inflorescence, tasselling, flowering, fruiting and senescence for Leymus chinensis, Stipa krylovii, Cleistogenes squarrosa, Allium anisopodium, Artemisia frigida, Heteropappus altaicus and Artemisia scoparia for semi-aridStipa krylovii steppe in Inner Mongolia from 1985 to 2002. Relationships among phenophases, variability, and climatic driving were examined using correlation analysis.

Important findings The climate of Stipa krylovii steppe exhibited a trend for warming and drying, with significantly increased air temperature in spring and summer and markedly decreased precipitation in autumn. Linear regression analysis indicated that spring phenophases occurred later and summer and autumn phenophases moved earlier. Phenophases in July and August with higher temperature were the most sensitive to climate change. Plant phenology was primarily controlled by light and air temperature. Phenophases of budding were highly correlated with canopy light interception in February and March and with air temperature of the coldest month, January. Other phenophases, from inflorescence, tasselling, flowering, fruiting to senescence, were negatively correlated with canopy light interception in July and August, and precipitation in June and July was negatively related to inflorescence, tasselling and flowering. The timing of senescence was postponed by precipitation in August and September, which promoted lengthening of the growing season.

Aims My objective was to determine the impact of a strong typhoon on the tropical montane rain forest community in Hainan Island.

Methods A 2 600 m²permanent plot in Jianfengling, Hainan Island was surveyed in June 2005 before Typhoon Damrey and in October 2005 after the typhoon. All individuals with diameter at breast height >1.0 cm were recorded and classified into four injury types. I analyzed changes in species composition, basal area, number of individuals, influence of wind-blown trees, biological diversity, biomass change and carbon return.

Important findings Many wind-blown trees, broken branches and fallen leaves appeared after Typhoon Damrey and this decreased crown density, increased penetrating light and produced many canopy gaps. Community composition and structure changed significantly, with 514 individuals (26.1%) damaged totally. Wind-blown individuals accounted for a large proportion, with 206 individuals (10.5%). ANOVA analysis showed that wind-blown and the normal trees did not differ in basal area, tree height and wood density. However, damage in the tree, sapling and understory layers was significantly different. Damages included direct and indirect damage. Direct damage mainly influenced the tree layer, where large-diameter individuals were damaged severely. The relative Importance Values of some species decreased; some became associate species and some sub-dominant species became co-dominant with formerly dominant species. Indirect damage mainly influenced the sapling and understory layers with wind-blown trees, broken branches and fallen leaves affecting other individuals. Individuals died in small areas, and some species disappeared from these layers. Individuals of some dominant species decreased, but accounted for only a small part of their populations. Shannon-Wiener and Simpson diversity indices decreased slightly in the tree layer, in contrast to the sapling and understory layer. However, a few species disappeared and the number of individuals of some species decreased in all layers. At least 10.42% of the forest biomass was lost after Typhoon Damrey, which greatly influenced the carbon cycle of the forest ecosystem.

Aims Our objective was to understand the population structure, spatial pattern and recruitment mechanism of Betula albo-sinensisforest at Taibai Mountain, northwestern China.

Methods Using data collected from 0.75 hm² plots, we determined the life table, age structure and survivorship curve of the B. albo-sinensis population. Univariate and bivariate Ripley’sK functions were employed to determine spatial distribution of standing trees and snags in different age classes and correlate standing trees and snags.

Important findings The B. albo-sinensis population had high mortality of seedlings and saplings, stable growth of adult trees and then gradually increased mortality. The survivorship curve of B. albo-sinensis population matched Deevey Type I. Snags mostly developed by uprooting and snapping, producing disturbed microsites that recruitment probably relied on. Standing trees and snags were clustered by each age class but randomly distributed when all classes were combined. Standing trees above a given size formed snags in pulses at a scale that was also the optimum canopy gap size for establishing. Population dynamics are related to spatial pattern and provide a measure of ecological significance between population structure and spatial patterns. As a sun-loving species,B. albo-sinensis requires disturbed microsites (e.g., sites of uprooting and snapping) and canopy openings for regeneration in the forest. Patterns in the distribution of standing trees appear to persist and were consistent with highly aggregated patterns of snags caused by natural disturbances across the stand. Findings suggest that cohorts of the B. albo-sinensis population at Taibai Mountain are spatially clumped and the aggregation of different cohorts represents pulsed recruitment that might be capable of maintaining population stability.

Aims Soil water is one of the most important factors driving succession in the Artemisia ordosica community in the Ordos Plateau, an arid and semi-arid region of northwestern China. Precipitation is the main source of soil water on the sandland. During each rainfall, part of the rain water is intercepted by plants and the surface layer of soil. This usually quickly evaporates and seems to be biologically ineffective for plant life. Therefore, soil water recruitment is affected by both annual precipitation and characteristics of each rainfall event, such as amount and process. Our objective was to describe the dynamics of soil water content and water recruitment during the growing season.

Methods We used eddy covariance technology to study the process of hydrological balance at the ecosystem scale and considered rainfall and evaportranspiration characteristics.

Important findings In 2006, annual precipitation was about 229.4 mm and rainfall was the main form, mostly occurring from May to October. Rain events differed in rain amount, length of time and intensity. Ecosystem evaportranspiration and rainfall availability were clearly affected by these rain characteristics and other biotic and abiotic factors. Rain events <5.0 mm increased relative humidity and decreased temperature. Rain events >5.0 mm increased soil water in the root layer and were important to community development and stability.

Aims Our objective is to compare a new photosynthetic light-response model with the non-rectangular hyperbola, rectangular hyperbola, and Prado-Moraes model in fitting data and obtaining the maximum net photosynthetic rate and the light saturation point.

Methods We measured the light-response of photosynthetic rate of winter wheat (Triticum aestivum) under the same chamber CO₂ concentration and different air temperatures in North China Plain using a gas analyzer Li-6400. The measured data were simulated by the new photosynthetic light-response model and the non-rectangular hyperbola, rectangular hyperbola and Prado-Moraes models, respectively.

Important findings The new photosynthetic light-response model shows advantage over the non-rectangular hyperbola, rectangular hyperbola, and Prado-Moraes models in fitting data on the maximum net photosynthetic rate and the light saturation point. The main photosynthetic parameters calculated by the new one were very close to the measured data (R²=0.999 4 and R²=0.998 7). Results showed that the apparent quantum was not an ideal indicator to assess the light use efficiency of plants. We suggest the apparent quantum yield be replaced by the quantum yield at the light compensation point due to the unity of the quantum yield for any C₃plantspecies under certain environmental conditions.

Aims Juglans regia and J. sigillata are important economic nut trees and are widespread in Sichuan Province. Accurate evaluation of genetic diversity and relationships between species is essential for effective preservation of germplasm resources and breeding. Traditional methods for assessment of genetic diversity in walnut, based on morphological, physiological and biochemical studies such as isozyme analysis or RAPD makers, are sensitive to environment so results are not reliable. AFLP has been applied extensively and effectively in population molecular ecology research and population genetic studies. Our aims were to identify genetic structure among populations and to examine genetic relationships between the two species.

Methods We compared three wild J. regiapopulations occurring at Qingba Mountain, Daduhe Valley, and southern Ganzhi District in Sichuan Province, and one wild J. sigillatapopulation at Panzhihua District in southeastern Sichuan Province. We selected 46 samples to analyze by AFLP molecular maker technology using 4 pairs of primer combinations screened.

Important findings We obtained 244 bands including 146 polymorphic bands. The percentage of polymorphic bands (P) was 59.84%. For the J. sigillatapopulation, percentage of polymorphic bands (P) was 52.05%, effective number of alleles per locus (A_e) was 1.339 9, and Nei’s gene diversity index (H) was 0.196 1, Shannon’s information index (I) was 0.289 8. For J. regiapopulations at species level, estimates were P=55.33%, A_e=1.322 9, H=0.190 8, andI=0.286 3. Although these findings showed that genetic diversity of J. sigillatawas slightly higher than the other species, genetic diversity level was generally equivalent. Shannon information index, Nei’s genetic diversity coefficient and analysis of molecular variance showed that 85.64%, 87.4%, 88.93% genetic diversities, respectively, distributed within populations at the species level. Most variation (80.65%) consistently originated from the interior of groups. The population ofJ. sigillatapossessed the greatest amount of unique bands, accounting for 4.5% of the total amplified bands, which indicated genetic variation between two species. The genetic differentiation coefficient (G_st=0.093 5) between two species is very low. Juglans regiashowed high genetic affinity to J. sigillata.Nei’s Genetic distances between populations varied from 0.038 2 to 0.069 2 and genetic similarities ranged from 0.933 2 to 0.962 5, which indicated there were high similarities among populations. UPGMA analysis revealed that threeJ. regiapopulations clustered first, and genetic distance was closest between the Daduhe Valley and southern Ganzhi District populations.

Aims Artemisia ordosica is a forage grass used for soil stabilization in arid regions, including our study area on the South Edge of Maowusu Sandy in Yulin, Shaanxi, China. Our objective was to determine the natural ecological distribution of AM fungi in relationship to soil factors in the rhizosphere of A. ordosica in order to provide information for the recovery of desert vegetation.

Methods We collected soil samples from the rhizosphere of Artemisia ordosica in four replicates, divided them into depths of 0-10, 10-20, 20-30, 30-40 and 40-50 cm, and measured colonization and ecological distribution of AM fungi. We analyzed AM fungi of A. ordosica rhizosphere soil using one-way ANVOA and correlated to soil factors.

Important findings Spore density and arbuscular colonization of AM fungi decreased with sampling time. Vesicular colonization decreased initially and later increased to its highest value in October. Hyphal colonization increased initially and later decreased; its highest value was in August. The highest colonization and spore density of AM fungi was at 0-10 cm and 20-30 cm depths in May. Soil factors were significantly correlated with the spatial and temporal distribution of AM fungi. Soil available N, available P and organic matter were significantly positively correlated with spore density, and soil available K was significantly correlated with hyphal colonization and total colonization.

Aims Ectomycorrhizal fungi promote growth of Mongol Scotch pine (Pinus sylvestrisvar. mongolica) seedlings. Our objective was to determine the effects of different inoculation methods, different combinations of fungal strains and different single strains on growth of Mongol Scotch pine seedlings.

Methods We screened combinations of different ectomycorrhizal fungus strains by dual culture method. Two-year-old seedlings were inoculated with different single strains of ectomycorrhizal fungi by soaking roots in the liquid culture of the ectomycorrhizal fungus. Three-year-old seedlings were inoculated with different single strains using lister method in the field. Seedlings inoculated by PD liquid culture medium served as a control. Three-year-old seedlings were inoculated by different combinations of ectomycorrhizal fungus strains using lister method in the field, and those inoculated by different single strains served as a control.

Important findings All single strain and their combinations promoted the growth of Mongol Scotch pine seedlings. Strains GT005 and 035 had the largest growth-promoting effects in all combinations and single strain. Compared with the control, average heights of 2-year-old seedlings inoculated by strains GT005 and 035 increased 54% and 42%, respectively, and average collar diameters increased 15% and 56%, respectively. Average heights of 3-year-old seedlings inoculated by strains GT005 and 035 increased 10% and 7%, respectively, and average collar diameters increased 10% and 9%, respectively. The growth-promoting effect of the inoculating method of root soaking is greater than that of the lister inoculating method. When mixed with another strain, the effect of the high-effect strain on growth of seedlings was reduced. The activity of hydrogen peroxidase and root activity are not correlated with seedling biomass.

Aims With the drastic increase in number of power plants adjacent to estuaries and bays, damage to plankton caused by thermal shock and chlorination in cooling systems has become a serious ecological problem in coastal areas. Presently, there are no criteria for temperature increment (ΔT) and chlorine dosage (CD) for coastal cooling systems in China. Our objectives are to 1) determine under which Δ T and CD that the phytoplankton biomass has potential to recover after passage through a cooling system and 2) supply a scientific basis for environmental risk assessment and standard formulation of Δ T andCD in cooling water.

Methods In four seasons from August 2006 to May 2007, we collected phytoplankton from the Yueqing Bay. In the laboratory, we stressed the phytoplankton at different Δ T (0, 4, 8, 12 ℃) and CD (0, 1.0, 1.8, 3.2, 5.6 mg·L^-1). We then recorded the phytoplankton cell density (PCD) every 24 h in a stable culture for 15 d.

Important findings Both thermal shock and season significantly affected PCD recovery (p<0.001). The recovery period was longer with rising acclimation temperature (AT) and Δ T. When AT was low in spring, autumn and winter, PCD could recover to the control level in 1-6 d at the Δ T of 4-12 ℃. However, thermal shock would affect PCD more severely when AT was high in summer, as 4-9 d was needed for recovery at the Δ T of 4-8 ℃ and the resilience was lost at the Δ T of 12 ℃. Chlorination also significantly affected the PCD recovery (p<0.001) and had a greater impact than thermal shock. ThePCD recovery period was longer with increasing CD. Though PCD could generally restore during 15 d at the CD of 1.0-1.8 mg·L^-1, it could not at the CDof 5.6 mg·L^-1 in all seasons. Also, there was a synergistic effect between Δ T and CD that the effect of chlorine on PCD recovery was enhanced under temperature increase in the four seasons. Based on these data, current Δ T (6-12 ℃), CD (1-2 mg·L^-1) and residual chlorine discharge level (0.15-0.25 mg·L^-1) in coastal power plants do not severely affect subtropical phytoplankton biomass.

Aims Improvement of end-use quality in wheat (Triticum aestivum) depends on thorough understanding of grain quality and effects of environment (E), genotype (G) and their interaction (G×E). Our objectives were to assess the relative effect of G, E and G×E on main quality traits of wheat grains.

Methods Two experiments were carried out in 2000-2002. In the first experiment, six wheat cultivars representing a wide range of gluten strength (strong-, medium-, and weak-gluten wheat) were planted at five sites with different latitudes (Tangyin 36° N, Wuzhi 35° N, Xuchang 34° N, Zhunadian 33° N, Xinyang 32° N) in Henan Province. In the second experiment, nine wheat cultivars released from nine different provinces were planted in eight provincial locations (Hubei 30º37＇N, Sichuan 30º39＇N, Jiangsu 32º23＇N, Shaanxi 34º18＇N, Henan 34º48＇N, Shandong 36º29＇N, Shanxi 37º26＇N, and Hebei 38º02＇N), representing a wider range of environments.

Important findings Significant genotypic differences in all the quality traits were observed in both experiments, indicating that cultivar selection was most important for desirable end-use quality. Significant environmental variations were observed in all the quality traits in experiment 2, but only in content of protein and gluten, sedimentation value and water absorption in experiment 1, which indicated that location was the second important factor determining wheat quality. From the magnitude of F values we concluded that, for quality traits such as grain hardness, sedimentation value, water absorption, stable period, maximum resistance and extension, genotypic effects were greater than environment effects, while environmental influence on protein content was much greater than that of genotypes in both experiments. But for other quality traits such as flour yield, forming time, mixing tolerance and softness, they were inconsistent in the two experiments. In the first experiment, no genotype-by-environment variations were observed. In the second experiment, though significant influences of genotype-by-environment were observed for grain hardness, ash, water absorption, forming time, stable period and maximum resistance, they were smaller than the main effect of either G or E. Significant differences existed in most quality traits between the two years, mainly caused by weather factors such as precipitation, hours of sunshine and average day temperature in May. Close correlation existed between weather factors and quality traits, indicating that excessive precipitation, fewer hours of sunshine and lower day temperature in May would negative affect grain quality for strong-gluten wheat cultivars.

Aims Nitrogen is very important for improving the yield and quality of peanut. Nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) are the main enzymes of nitrogen metabolism that would be affected by nitrogen level. Our objective was to study the effects of nitrogen level on soluble protein content, free amino acid content and correlating enzyme activities of nitrogen metabolism in peanut.

Methods We carried out a field experiment of two cultivars under four nitrogen levels (0, 45, 90 and 180 N kg·hm^-2) and investigated the soluble protein content and free amino acid content in leaf, stem, root and pod of peanut, as well as the activities of the nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in these organs.

Important findings With the nitrogen application, the soluble protein content and free amino acid content were increased, and the activities of the nitrate reductase (NR), glutamine synthetase (GS) and glutamate dehydrogenase (GDH) also increased. When excessive nitrogen was used, the NR activity and kernel protein content were increased, while the activities of GS and GDH were decreased. Soluble protein content, free amino acid content, NR, GS and GDH along with the growth periods were not affected by nitrogen level, but with suitable nitrogen the activities of NR and GS in different organs could be increased. Also, nitrogen level affected GDH activities in leaf and kernel, with lower effect on the GDH activities in stalk and root. In conclusion, nitrogen level could affect the correlating enzyme activities of nitrogen metabolism in peanut, which resulted in changes of soluble protein content and free amino acid content in organs. The best nitrogen level for peanut was 90 N kg·hm^-2.

Giant panda (Ailuropoda melanoleuca) is a flag species for biodiversity conservation. Protecting giant panda and its habitats helps guarantee biodiversity conservation and integrity of ecosystem function. The Wenchuan earthquake occurred in Minshan and Qionglai Mountains, where the most important habitats for giant pandas occur. The earthquake damaged 27 nature reserves for giant pandas and 8.3% of the giant panda habitat. The earthquake and earthquake-induced events such as landslides have important ecological consequences. First, the earthquake damaged bamboo, the main food for giant pandas. At the same time, the earthquake may induce bamboo flowering, which will threaten the food supply of giant pandas. Second, the earthquake and earthquake-induced soil movements and rockslides caused small-scale damage such as treefalls, which will influence forest dynamics through long-term effects on tree mortality, growth and competition. Third, the earthquake will fragment habitats, causing isolation among giant panda populations. Therefore, we propose reassessment of the quality of giant panda habitats at landscape or regional scales and adjustment of the system of nature reserves. In addition, it is necessary to survey and monitor bamboo resources, including their distribution and dynamics, and to regenerate or rejuvenate bamboo. We also propose restoring degraded habitats with natural vegetation and plantings.