[Effects of seed size and drought stress on the growth and physiological characteristics of Quercus wutaishanica seedlings]. / ç§å­å¤§å°å’Œå¹²æ—±èƒè¿«å¯¹è¾½ä¸œæ Žå¹¼è‹—ç”Ÿé•¿å’Œç”Ÿç†ç‰¹æ€§çš„å½±å“.

The effects of seed size and drought stress on the growth and physiological characteristics of Quercus wutaishanica seedlings were investigated under shading conditions of a pot experiment in greenhouse. There were four treatments, including 80% field water content (FWC), 60% FWC, 40% FWC, and 20% FWC [CK, light drought stress (LDS), medium drought stress (MDS), and high drought stress (HDS), respectively]. The results showed that leaf area per plant, total dry mass, and root-shoot ratio of Q. wutaishanica seedlings regenerated from large seeds (3.05±0.38 g) were significantly higher than those from small seeds (1.46±0.27 g) in all four treatments. Shoot height, basal stem diameter, leaf number, specific leaf area, relative growth rate, and net assimilation rate of the seedlings from large seeds were higher than those of seedlings from small seeds under the treatments of LDS, MDS and HDS. Activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) in large-seeded seedlings were higher than those of small-seeded seedlings under all treatments, while the contents of MDA, soluble protein, free proline, and total chlorophyll of large-seeded seedlings were higher than those of small-seeded seedlings only under some drought stress treatments. All growth parameters except the root-shoot ratio decreased with the increases of drought stress. The HDS treatment resulted in 19.4% and 20.0% decline in total dry mass of large- and small-seeded seedlings respectively, compared with those of CK. With increasing drought stress, the activities of POD, CAT, and SOD decreased after an initial increase. POD activity of large- and small-seeded seedling under MDS treatment was 126.7% and 142.1% higher than CK, while CAT was 170.0% and 151.9% higher than CK, respectively. However, the MDA content of seedlings from large and small seeds under HDS treatment was 86.5% and 68.9% higher than that of CK, respectively. The contents of soluble protein, free proline, and total chlorophyll rose at first and then fell with increasing drought stress, and soluble protein content in large- and small-seeded seedlings experienced MDS enhanced 320.7% and 352.7%, respectively. Those results indicated that large-seeded seedlings of Q. wutaishanica had stronger drought tolerance than small-seeded seedlings due to their growth and physiology advantages. Large-seeded seedlings with stronger resistance to drought stress should be applied to artificial regeneration of the degraded secondary Q. wutaishanica plantations.

Effects of seed traits and seed production on the seed predation and dispersal behavior of rodents.

To deeply understand the foraging behavioral strategies of the rodents in response to seeds of different sizes and tannin contents under different seed densities and its relationship with plant regeneration, field experiments were conducted to explore the effects of artificial seeds of different sizes (large and small) and tannin (T) contents (0%T, 2%T, 8%T, and 15%T) on seed predation and dispersal behavior of rodents during simulated non-mast and mast seeding year in Larix principis-rupprechtii plantation of Liupan Mountains in Ningxia. The results showed that seeds were consumed rapidly by rodents in non-mast seeding year but relatively slow in mast seeding year. No significant difference of in situ predation rate (ISPR) was observed between non-mast and mast seeding year. The predation rates of seeds after dispersal (PRAD) by rodents in non-mast year were significantly higher than those in mast year, while the hoarding rate of seed after dispersal (HRAD) of the former was significantly lower than the latter. Both seed predation distance after dispersal (PDAD) and hoarding distance after dispersal (HDAD) by rodents in non-mast year were substantially higher than those in mast year. In non-mast year, both PDAD and HDAD of large seeds were longer than those of small seeds. Significant difference of the former was observed between large and small seeds for all tannin content seeds, but significant difference of the latter between large and small seeds was detected only for seeds of 2% and 15% tannin. In mast year, significant difference of PDADs and HDADs between large and small seeds was found in all other seeds of tannin contents except for 0% Tannin seeds. The ISPR maximized in medium tannin seeds and minimized in high tannin seeds. Maximums of PRAD were observed in high tannin seeds in non-mast year and 0% tannin seeds in mast year respectively. High tannin seeds had the highest HRAD while medium tannin seeds had the lowest HRAD in both mast and non-mast year. Our results suggested that mast seeding year could delay the seed consumption rate of rodents and increase the HRAD, but reduce the dispersal distance. Hoarding preference of the rodents on large seeds was demonstrated in both mast and non-mast years and the dispersal distance of large seeds was longer than those of small ones. It is probably that rodents prefer to predate in situ seeds of medium tannin and disperse high tannin seeds during both mast and non-mast years.

[Predation and removal of rodents on the seeds with different size and pericarp traits].

A field survey was conducted in the Quercus wutaishanica shrubs in Liupan Mountains of Ningxia, Northwest China to study the predation and removal of rodents on the seeds of Q. wutaishanica, Prunus salicina and Pinus armandii, aimed to explore the effects of seed size and pericarp traits on the predation and removal behaviors of rodents. The in situ seed predation rates of smaller Q. wutaishanica seeds and P. armandii seeds were significantly higher than those of larger Q. wutaishanica seeds and P. salicina seeds. The P. salicina seeds with hard and thick pericarp (endocarp) had the highest predation rate and hoarding rate after the removal by rodents. The movement distance of larger Q. wutaishanica seeds during predation events was the longest (3.10 m), and the seed hoarding distance of this species (6.48 m) was significantly longer than that of the three other types of seeds. Over 80% of sites were used as the predation sites by rodents for the seeds, except that the P. salicina seeds contained only a single seed and the cache sites contained a single seed accounted for over 90% for all types of seeds. Few predation and cache sites containing over two seeds were detected. Higher proportion of P. armandii seeds were predated in microhabitats except at the base of shrubs and in the holes after removal by rodent, while the seeds of other three types were predated mainly at the base of shrubs and in the holes after removal by rodents. The seed hoarding patterns after removal by rodents were primarily determined by pericarp traits, and higher proportion of soil burial that the rodents hoarded seeds with hard pericarp (endocarp) was detected.

[Effects of light intensity on Quercus liaotungensis seed germination and seedling growth].

This paper studied the effects of different shading (55.4%, 18.9%, 5.5%, 2.2%, 0.5% , and 0.3% natural sunlight) on the seed germination and seedling growth of Quercus liaotungensis. The seed germination rate and germination index were the highest (72.5% and 0.22, respectively) at 55.4% natural sunlight, declined with decreasing light intensity, and were the lowest (42.5% and 0.11, respectively) at 0.3% natural sunlight. Strong light had definite delaying effect on the germination. The index of germination vigor increased with decreasing light intensity, being the maximum at 0.5% natural sunlight. The delay of seed germination under strong light could be the selective tradeoff on varied seed fates. Strong light benefited the basal stem diameter and root system growth and dry mass accumulation of Q. liaotunensis seedling, but resulted in the minimum seedlings height (6.06 cm). Greater morphological plasticity was observed for the seedlings under different shading, which lent support to the higher adaptability of the seedlings to light environment. For example, the specific leaf area, specific shoot length, specific root length, and chlorophyll b and total chlorophyll contents were the maximum at 0.5% natural sunlight, being 142.57 cm2 x g(-1), 156.86 cm x g(-1), 271.87 cm x g(-1), 0.07 g x cm(-2), and 0.24 g x cm(-2), respectively, and the minimum at 55.4% natural sunlight, being 44.89 cm2 x g(-1), 52.84 cm x g(-1), 101.98 cm x g(-1), 0.04 g x cm(-2), and 0.15 g x cm(-2), respectively. The variation of the root/shoot ratio of Q. liaotungensis seedlings under different shading could be the effects of the combination of light intensity and water availability.