RESUMO
We investigated the morphological characteristics of C. korshinskii seeds with three different sizes under plantations with different stand ages (6, 12, 18, 40 and 50 years old) in the typical sandy-hilly region of northwest Shanxi Province, to explore the restoration potential of artificial vegetation from the perspective of reproduction strategies. The results showed that seed production of C. korshinskii plantation increased with stand age, reaching the maximum (584 grain·plant-1) in 50-year-old stand. Seed length, seed width, and seed shape index decreased with stand age, reaching the minimum (5.09 mm, 2.76 mm and 0.05) in 50-year-old stand. Seed germination percentage showed an upward-downward-upward fluctuating trend, reaching the maximum (97.2%) at 12-year-old stand. Seed production was significantly negatively correlated with seed weight. Seed germination percentage was closely related to seed weight. Seeds with low weight had a low germination percentage and were easier to form a persistent seed bank. In addition, seed production was significantly positively correlated with the height of mother plant, aboveground biomass and belowground biomass, while the shape index of C. korshinskii seeds was significantly negatively correlated with number of new branches. It indicated that with the increases of stand age, the reproduction strategy of C. korshinskii changed from the K strategy with larger seeds in the early stage (6-12 year-old) to the r strategy of small seeds in the later stage (18-50 year-old). Specifically, C. korshinskii kept both the high number and high persistence of seeds by producing a larger number of small and round seeds.
Assuntos
Caragana , Germinação , Sementes , Biomassa , Banco de SementesRESUMO
The sandy-hilly region of northwest Shanxi is a typical fragile agro-pastoral ecotone in north China. With the artificial Caragana korshinskii at 0 (the uncultivated land), 6, 12, 18, 40 and 50 years-old in the typical sandy-hilly region of northwest Shanxi as the subjects, we investigated soil moisture, aboveground and belowground biomass, individual morphological characteristics, growth, reproduction, and photosynthetic physiological characteristics of different-aged C. korshinskii, with the aim to evaluate the long-term growth and reproductive dynamic characteristics of artificial C. korshinskii. The results showed that soil moisture was significantly affected by stand ages. Soil moisture was low under the 6-year-old C. korshinskii plantation. During 6-18 years-old, soil moisture increased due to the increased crown width and reduced the near-surface wind speed, solar radiation, and soil water evaporation. During 18-50 years-old, soil moisture decreased sharply due to higher biomass and plant transpiration of C. korshinskii, and soil moisture was reduced to the lowest level of 11.1%. C. korshinskii mainly developed underground root system during 6-18 years-old, and changed to the aboveground biomass accumulation in 18-40 years-old. At the 40-year-old stand, biomass reached to the highest level with the greatest crown width and plant height. During 40-50 years-old, crown width and plant height decreased significantly, while the growth began to degrade. Photosynthetic capacity (chlorophyll a, b, carotenoid and total chlorophyll content) gra-dually decreased with the increases of planting ages, especially after 18 years-old. The quantity and quality of C. korshinskii seeds increased from 6 to 40 years-old, reached the maximum at 40 years-old stand, and began to decrease after 50 years-old. In the later growth period (30-40 years-old), more seeds with small individual weight were produced compared with early period (6-12 years-old). The germination test showed that small seeds had higher germination rate than the large ones under the same stand age, suggesting a shift of reproduction strategy. After 50 years-old, both of the growth and reproduction of C. korshinskii degenerated, and the plantation began to degrade.
Assuntos
Caragana , China , Clorofila A , Reprodução , Solo , Água/análiseRESUMO
We assessed the effects of different concentrations of salts (0, 40, 80, 120, 160 and 200 mmol·L-1) on the seed germination and re-germination of six typical annuals (Gramineae: Setaria viridis, Chloris virgata and Eragrostis minor; Chenopodiaceae: Bassia dasyphylla, Salsola ruthenica and Corispermum mongolicum) in autumn of current year and next spring, with NaCl and NaHCO3 as neutral sodium salt and alkaline sodium salt. The results showed that NaCl and NaHCO3 significantly affected seed germination of the six species. The inhibition effect of NaHCO3 on seed germination was stronger than NaCl. When the concentration of NaHCO3 reached to 160 mmol·L-1, germination rates of the six species were low. However, when the concentration of NaCl reached to 200 mmol·L-1, the germination rates of the six species were still high. The germination (2.8%-20.0%) and re-germination rates (3.3%-20.0%) in current autumn were much lower than those in next spring, with values of 21.7%-81.6% and 5.0%-41.1%, respectively. In autumn, most of the current year's seeds kept dormancy, but the dormancy weakened in next spring. The salt tolerance of seeds of the six annual species was in the order of C. virgata > S. viridis > S. ruthenica > B. dasyphylla > C. mongolicum > E. minor.
Assuntos
Germinação , Sementes , China , Estresse Salino , SódioRESUMO
Under 5 m(COD)/m(N)/m(P) ratios, the shape, settle ability and organic removal performance of aerobic granules were investigated in 5 identical SBRs. The performance of aerobic granules bulking and its recovery methods were also analysed based on SVI30 value. The results indicated that when m(COD)/m(N)/m(P) was 100/5.8/1.2, the granules had integral and dense structures with the SVI30 of 15 - 30 mL x g(-1) and COD removal of above 90%. The system operated stably without any bulking. When m (COD)/m(N)/m(P) was 100/3/0.6 and 100/1.9/0.4, although the granules disintegration was observed, SVI30 was lower than 35 mLx g(-1) and the granules had no bulking, and high COD removal was keeping at above 85%. When m(COD)/m (N)/m(P) was 100/ 0.5/0.1 and 100/0/0, the SVI30 in both systems reached 150 mL x g(-1), and the granules was hard to settle due to sludge bulking in both systems. There is a significant difference of COD removal rate in two systems. The former COD removal rate stayed at 65% -80% in late experiment, while the latter COD removal was quite low during the early operation and finally reduced to about 10% until the system broke down. Aerobic granule bulking due to the lack of N and P could be recovered by adding sufficient nutrient to the systems. After 48 cycles' operation, granules settle ability and organic removal were fully recovered, however there was no obvious recovery on granules morphology except for the color.
