Abstract:Here we report on ecology and biodiversity of fungi in a unique mycological sanctuary in Britain, where data on species composition have been collected since 1994. To complement the biodiversity data by the information on the fungal ecological interactions and their role in the overall ecosystem functioning, soil properties and the composition of forest litter and field layer, bacterial population numbers and fungal biomass (in terms of ergosterol) were measured in 8 plots covered with different vegetations (beech, birch, birch-oak-beech, grass) over a May–Aug. period, and the results were analysed by correlation analysis and stepwise regression modelling together with data on protozoa and nematodes available from parallel research. The results highlighted the complexity of factors influencing temporal dynamics and spatial variability of fungal biomass in soil and forest litter. Most of the registered interactions appeared to be transient, and this should be taken into account while interpreting environmental observations. Interpretation of the specific relationships is given and implications for further research and overall ecosystem functioning are discussed.

Abstract:Hydraulic architecture and its relationship with environmental factors were studied in three Caragana species, namely, Caragana microphylla Lam., C. davazamcii Sancz and C. korshinskii Kom, which were found in different habitats of the Inner Mongolian Plateau, China. The improved flushing method was used in situ on one-year-old twigs for comparing the hydraulic efficiency and the regulating abilities of these three species as well as their mechanisms of regulating water transport to cope with variable environments. The relationship between hydraulic architecture and air temperature followed a linear function with negative slope, whereas the relationships between these parameters with atmospheric humidity were positive. Comparing the hydraulic efficiency among the three seasons, a descending order was given as summer>spring>autumn. In the same season, the hydraulic efficiency of C. korshinskii was higher than that of C. davazamcii, which was in turn higher than that of C. microphylla. It can be concluded from the range of Ks and the slope of two linear functions that there were significant differences in the sensitivity of specific conductivity to environmental factors, both among species and among seasons, with a descending order as summer>spring>autumn. In the same season, C. korshinskii was the most sensitive to the changes of environment, and the sensitivity of C. davazamcii was higher than that of C. microphylla. The results also supported the view that the reduction of hydraulic efficiency because of the embolism in xylem could benefit the plants subjected to water deficit by means of limiting water loss.

Abstract:Accurate estimation of below-canopy CO₂ flux (Fcb) in typical forest ecosystems is of great importance to validate terrestrial carbon balance models. Continuous eddy covariance measurements of Fcb were conducted in a coniferous and broad-leaved mixed forest located in Dinghushan Nature Reserve of South China. Using year-round data, Fcb dynamics and its environmental response were analyzed, and the results mainly showed that: (1) Fcb decreased during daytime which indicated that the understory of the forest continued photosynthesis throughout the year; however, understory and soil acted as CO₂ source as a whole. (2) Using soil temperature (Ts) as a dependent variable, all of Van’t Hoff equation, Arrhenius equation and Lloyd-Taylor equation can explain a considerable variation of Fcb. Among those three equations Lloyd-Taylor equation is the best to reflect the relationship between soil respiration and temperature for its ability in revealing the variation of Q₁₀ with temperature. (3) Fcb derived from Lloyd-Taylor equation is utterly determined by Ts, while Fcb derived from the multiplicative model is driven by Ts and soil moisture (Ms). The multiplicative model can reflect the synthetic effect of Ts and Ms; therefore it explains more Fcb variations than Lloyd-Taylor equation does. (4)Fcb derived from the multiplicative model was higher than that from Lloyd-Taylor equation when Ms was relatively high; on the contrary, Fcb derived from the multiplicative model was lower than that from Lloyd-Taylor equation when Ms was low, indicating that Ms might be a main factor affecting Fcb when the ecosystem is stressed by low-moisture. (5) Annual Fcb of the forest in 2003 was estimated as (787.4±296.8) gCm^-2a^-1, which was 17% lower than soil respiration measured by statistic chamber method. CO₂ flux measured by eddy covariance is often underestimated, and further study therefore calls for emphasis on methods quantifying Fcb components of respiration of soil, as well as respiration and photosynthesis of understory vegetations.

Abstract:The foraging behavior consisted of three steps: searching, recruitment and transportation. Searching time was different for different foods; searching time for honey was longer than that for any other food tested. It was also affected by habitats with the searching time of fire ants in a litchi orchard being significantly longer than that for other habitats (p<0.01). However, the weight of the food had no obvious effect on the searching time. The recruitment of fire ant workers during foraging was regular, and there was a strong relationship between the number of recruited workers and the transportation time. When the food was too heavy to transport immediately into the nest, the number of recruited workers was maximum at 30 min after the food was initially found. For smaller sized food sources maximum recruitment of workers was possible at a shorter time and the food was more rapidly transported back to the nest. For different foods, the dynamics of recruitment were similar although the number of recruits was different. The weight of the food and the habitats also deeply affected the time spent on transportation.

Abstract:The spawning runs of Chinese Sturgeon (CS; Acipenser sinensis) were observed 37 times below Gezhouba Dam of Yangtze River between 1983 and 2004. Five hydrological factors (water temperature, water level, flow discharge, silt content and current velocity) were monitored on a daily basis at the spawning ground between October and November for 22 consecutive years (1983–2004). The effect of current velocity on the spawning ground at the bottom layer of the river, where CS was spawning for four years, was measured (1996–1999). The authors of this study analyzed the relationship between the five hydrological factors and the respective spawning runs. Twenty-two years of continuous observations indicated that the daily mean values of all the five hydrological factors fluctuated within a certain range when CS was spawning. It was concluded that the optimal values for the hydrological factors during the spawning runs are 18.0–20.0C for temperature, 14100 m³/s for discharge volume, 42.0–45.0 m for water level above the sea level, and 0.2–0.3 kg/m³ for silt content in the water, wherein the current velocity above the bottom layer to stimulate the fish to spawn should be between 1.0–1.7 m/s. The optimal water temperature might provide an essential precondition for other factors to trigger spawning. As water temperature reaches the optimal values and most of the other parameters are at the brink of deviation from their optimal range of values (water level, current velocity and silt content in the water), CS would begin to spawn. By 2009, when the Yangtze Three Gorges Project, which is located 45 km upstream of the Gezhouba Dam, is completed and begins to operate normally, changes in the downstream water temperature are expected to occur, which may have a negative effect on the development of gonad and the stimulation of spawning of CS; however, the anticipated decrease of the silt content in the water may be considered favorable for the performance of the spawning site.

Abstract:The formation of 161 km-long arid valley (170 km²) of Mingjiang River is attributed to the effect of foehn. The arid valley presents harsh conditions for the growth of vegetation, which include higher annual evaporation and transpiration rate (1400–2000 mm), lower annual precipitation rate (400–700 mm), steep slope, and infertile soils. Although the vegetation is dominated by xerophilous bushes and grasses, it plays a significant role in soil and water conservation in watershed and provides important references in the arid valley as it is very difficult to grow trees. Drought-resistant physiological characteristics of four native species, i.e., Sophora davidiana, Bauhinia faberi var. microphylla, Convolvulus tragacanthoides, and Artemisia gmelinii, have been measured. It was found that the content of chlorophyll, free proline and soluble sugars showed an increase, whereas evaporation ratio, WSD, RWC and cytolemma osmosis showed a decrease under drought stress. Integrated assessment of the four species indicated that the integrated drought resistance index was the highest in July (0.507), followed by September, August and June, whereas it was the lowest in May (0.442). The result provided a basis for vegetation restoration, especially it improved survival of planted species in May and June when plant species exhibit the weakest drought resistance.

Abstract:Fire in the Great Hing′an Mountains in 1987 affected an area of more than 1.3310⁶ hm², creating a mosaic of burn severities across the landscape, which strongly affected the postfire vegetation succession. In addition, undulate landform and anthropogenic disturbance inevitably influenced the postfire vegetation succession. In this paper, a typical area was selected for a case study, including two forest farms, covering more than 1.210⁵ hm². In order to reveal how the forest changed in 2000 (13 years after the fire) by comparing with 1987 (prefire) and to find out the relationship between the forest succession and the affecting factors, forest crown density was selected as the criterion, and forest type, fire severity, silviculture practice, elevation and topography gradients were designed as the affecting variables. With the support of GIS software, each variable was classified and entered into the multivariate regression model. The result showed that the forest crown density changed notably in 2000 compared with that of the prefire, and all the variables significantly affected the forest crown density. The most important affecting variable was elevation, which was positively correlated with the forest crown density. The next was fire severity, which was negatively related with the forest succession. The effects of topographic factors and silviculture practices on forest crown density were relatively small.