Effects of mixed substrates of different agricultural and forestry residues on the cutting seedlings of Thuja sutchuenensis.

To screen environment-friendly seedling cultivation substrates which could replace peat and with less cost, we compared the effects of different agricultural and forestry residue mixed substrates on cutting propagation of Thuja sutchuenensis, in an experiment following randomized block design. There were five types of mixed substrates, including peat + vermiculite + perlite (T1), edible mushroom residue (EMR) + vermiculite + perlite (T2), carbo-nized rice husk (CRH) + vermiculite + perlite (T3), EMR + slag + sawdust (T4) and CRH + EMR + slag (T5). The results showed that the bulk density of T3 was the lowest, followed by T2, which significantly differed from other mixed substrates. The non-capillary porosity of T2 was significantly greater than that of T1, while the capillary porosity and the total porosity of T2 was lower than T1 and T3, respectively. T2 had the highest contents of total nitrogen, total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus, substrate moisture and the highest pH, which differed significantly from other mixed substrates in most chemical indicators. The membership function values of rooting rate and growth indicators of cuttings with different mixed substrates were in order of T2 > T3 > T1> T5 > T4. Most indicators with larger grey relation values were physical indicators. The top five indicators were capillary water capacity, total potassium, field water capacity, maximum water capacity, and total porosity, with both capillary water capacity and total potassium content ranking first. In general, the physicochemical properties, rooting rate, and growth characteristics of cuttings under T2 were better than those of other mixed substrates. The capillary water capacity and total potassium were the main factors affecting rooting and growth of cuttings. At the early stage of cutting, the physical properties of mixed substrate had greater effect on rooting rate and growth of cuttings than the chemical properties. Overall, our results suggested that T2 should be preferred in the cutting propagation of T. sutchuenensis.

[Light response characteristics of photosynthesis and model comparison of Distylium chinense in different flooding durations].

The light responses of photosynthesis of two-year-old Distytum chinense seedlings subjected to a simulated reservoir flooding environment in autumn and winter seasons were measured by using a Li-6400 XT portable photosynthesis system, and the light response curves were fitted and analyzed by three models of the rectangular hyperbola, non-rectangular hyperbola and modified rectangular hyperbola to investigate the applicability of different light response models for the D. chinense in different flooding durations and the adaption regulation of light response parameters to flooding stress. The results showed that the fitting effect of the non-rectangular hyperbola model for light response process of D. chinense under normal growth condition and under short-term flooding (15 days of flooding) was better than that of the other two models, while the fitting effect of the modified rectangular hyperbola model for light response process of D. chinense under longer-term flooding (30, 45 and 60 days of flooding) was better than that of the other two models. The modified rectangular hyperbola model gave the best fitted results of light compensation point (LCP) , maximum net photosynthetic rate (P(n max)) and light saturation point (LSP), and the non-rectangular hyperbola model gave the best fitted result of dark respiration rate (R(d)). The apparent quantum yield (Φ), P(n max) and LSP of D. chinense gradually decreased, and the LCP and R(d) of D. chinense gradually increased in early flooding (30 days), but D. chinense gradually produced adaptability for flooding as the flooding duration continued to increase, and various physiological indexes were gradually stabilized. Thus, this species has adaptability to some degree to the flooding environment.

[Life form spectra, leaf character, and hierarchical-synusia structure of vascular plants in Thuja sutchuehensis community].

Based on the investigation of the plants in Thuja sutchuenensis community, the life form spectra, leaf character, and hierarchical-synusia structure in the community were analyzed. The life form spectra of the plants in the community were 73.2% of phanemphyte, 18% of hemicryptophyte, 6% of geophyte, 2% of chamaephyte, and 0.8% of annual plants. The leaf quality was mainly of papery and conaceous, which occupied 48. 8% and 36. 4% , respectively. The dominant leaf size was microphy (60.8%), dominant leaf margin was un-entire (56.8%), and dominant leaf form was simple (86%). The T. sutchuenensis community had three sub-layers, i.e., tree layer, shrub layer, and herb layer, with lesser interlayer plants. Each layer was respectively composed by phanemphyte evergreen coniferophyte, broadleaf and deciduous broad-leaf plants, nanophanerophyte evergreen and deciduous broad-leaf plants, as well as hemicryptophyte, geophyte, and annual plants.

[Characteristics of soil seed banks in backwater area of Three Gorges Reservoir water-level-fluctuating zone at initial stage of river-flooding].

A germination test was made to study the characteristics of soil seed banks in the backwater area (including the flooded, non-flooded, and control areas of secondary bush and abandoned farmland) of Three Gorges Reservoir water-level-fluctuating zone. There existed significant differences in the soil seed banks between secondary bush and abandoned farmland, with an average seed density being 6991 +/- 954 seed per m2 and 26193 +/- 6928 seed per m2, respectively. Flooded area had the lowest seed density, while non-flooded area had the highest one. The seed density decreased with soil depth. A total of 118 species belonging to 45 families and 97 genera were detected in the soil seed banks of secondary bush and abandoned farmland, most of which were annual and perennial herbage species, belonging to Asteraceae, Poaceae, Scrophulariaceae, and Cruciferae. Among the 118 species, there were 34 species (occupying 28.8%) whose individuals accounted for less than 0.01% of the total. In the soil seed banks of secondary bush and abandoned farmland, the species number was similar, species diversity index and evenness index were relatively high, but the dominant species differed greatly, and the ecological dominance was relatively low. The species diversity in non-flooded area and the ecological dominance in flooded area were the highest, and the similarity index between the flooded and non-flooded areas was the highest.