Chin J Plant Ecol ›› 2012, Vol. 36 ›› Issue (8): 831-840.DOI: 10.3724/SP.J.1258.2012.00831

• Research Articles • Previous Articles     Next Articles

Cotyledon loss and its effects on survival and growth of Quercus wutaishanica seedlings under different densities

YAN Xing-Fu*(), ZHOU Li-Biao, ZHANG Kao-Wen, ZHOU Yun-Feng   

  1. College of Biological Science and Engineering, Beifang University of Nationalities, Yinchuan 750021, China
  • Received:2012-01-04 Accepted:2012-05-07 Online:2012-01-04 Published:2012-08-21
  • Contact: YAN Xing-Fu

Abstract:

Aims Our objective are to explore cotyledon predation by rodents and its effects on survival and growth of Quercus wutaishanica seedlings under different densities, and to disclose the potential bottlenecks limiting seedling recruitment and natural regeneration of populations.
Methods We transplanted Q. wutaishanica seedlings at six densities of 3.24, 2.56, 1.96, 1.44, 1.00 and 0.64 individuals·m-2 in a Larix principis-rupprechtii plantation of China’s Dadaogou forest region, Liupan Mountains. We surveyed retention rate of seedling cotyledon (RRC), retention rates of taproot (RRT) and apical bud (RRA) after cotyledon predation by rodents and retention rates of cotyledon- and apical bud-predated (RRCP, RRAP) and cotyledon- and apical bud-remained seedlings (RRCR, RRAR). At the end of the experiments, we harvested all surviving seedlings and determined seedling height (SH), basal stem diameter (BSD), leaf number (LN), taproot length, leaf area per seedling (LAPS), total dry mass, root shoot ratio and specific leaf area.
Important findings Density effect of cotyledon predation on Q. wutaishanica seedlings was observed and the RRC decreased with increase of seedling density. Six and five weeks after transplanting, the RRCs of two higher densities (3.24 and 2.56 individual·m-2) stabilized at their minimums (8.64% and 7.81%), while those of two lower densities (1.44 and 0.64 individual·m-2) were still higher at the last cotyledon survey and were signifycantly higher than those of all other density treatments (p < 0.05). The RRA was the highest (25.23%) in 1.44 individual·m-2density and was higher (4.19%) than that in 3.24 individual·m-2 density (p < 0.05), and all other densities resulted in < 20% of RRA. Significant difference between RRCP and RRCR was detected only on certain survey dates of individual density. RRAP was slightly lower than RRAR, and individual density exhibited the inverse. The fluctuation of retention rate of different seedling types may have be resulted from new germinated sprouts after apical buds were gnawed. SH, BSD, LN and LAPS all increased slightly with density decrease. The maxima of all parameters except SH were detected under the density of 1.44 individual·m-2and, to some extent, were related to whether cotyledon was predated by rodents or not, indicating that more seedlings grown at higher density lost their cotyledons and thus exerted influence on seedling growth.

Key words: cotyledon predation, density effect, Liupan Mountains, Quercus wutaishanica, rodent, seedling survival and growth