关键词: 文冠果, 坡向, 幼苗, 生长, 生物量, 环境因素

Abstract:

【Objective】Xanthoceras sorbifolia is naturally distributed in the northwest of China, strongly tolerant to cold, drought and poor site conditions. It is an important species for oil production and erosion control in north China. Moreover, it is an ideal tree species for land conversion of cropland to forest and for management of barren hills in the northern Loess Plateau of China.【Method】In order to understand the characteristics of seed germination, seedling development and their influencing factors, 24 sampling plots were established in 3 habitats (sunny slope, semi-sunny slope and semi-shady slope) of X. sorbifolia forests on the Loess Plateau where is the central distribution of the species. 【Result】One-year-old seedlings were found at all habitats, but the average number varied among habitats. A larger number of 632 individual·hm^-2 at the sunny slope, 48 individual·hm^-2 at the semi-shady slope. The conversion rates of seeds to seedlings were low at all 3 habitats, and manifested as semi-shady slope (0.57%) > semi-sunny slope (0.43%) > sunny slope (0.25%). The total number of seedlings was small at all 3 habitats, and gradually decreasing with the age of seedlings. For different ages from 1-5 years, the number of seedlings showed the following order: sunny slope > semi-sunny slope > semi-shady slope. Due to the differences of sunlight intensity and moisture content among the 3 habitats, X. sorbifolia seedlings has evolved different adaptive strategies, the height, basal diameter, and crown width of 1-5 year seedlings showed the order of sunny slope > semi-sunny slope > semi-shady slope. The sunny slope was more beneficial to the growth of X. sorbifolia seedlings. The underground biomass of 1-5 year seedlings were greater than above-ground biomass at all 3 habitats, and above-ground biomass and underground biomass showed the order of sunny slope > semi-sunny slope > semi-shady slope. Due to environmental heterogeneity, the age of maximum biomass ratio of underground to aboveground (R:S) differed among the 3 habitats, at sunny and semi-shady slopes the R:S value peaked at the age of 2 years, whereas t the semi-sunny slope, the value peaked at the age of 4 years. The stem dry mass, leaf dry mass, and root dry mass of 1-5 years seedlings were greater at the sunny slope than the semi-sunny and semi-shady slopes, and the difference tendency to increase with age. With the increase of age, the biomass ratios of stem, leaf and root at sunny slope respectively to those at semi-sunny and semi-shady slopes will be increasingly different. Environment factors had significant influence on the number, height, and biomass of seedlings. The number of seedlings was significantly positively correlated with light intensity, and significantly negatively correlated with the total plant coverage. The height of seedlings was significantly negatively correlated with soil moisture. The biomass of seedlings was significantly positively correlated with light intensity.【Conclusion】 At the sunny slope, seed germination rate was lower. However, it was beneficial for establishment of the seedlings compared to the semi-sunny and semi-shady slopes. The growth performance of seedlings was superior at the sunny slope to at the semi-sunny and semi-shady slopes, indicating that at this habitat the seedlings could make full use of growing conditions to shorten the time for entering the main forest storey. Therefore, the sunny slope should be selected for growing plantations of Xanthoceras sorbifolia.

Key words: Xanthoceras sorbifolia, slope aspect, seedling, growth, biomass, environmental factor