Xanthoceras Sorbifolia Population Propagation Ecology And Type Partitioning In Hill Loess Plateau In North Shaanxi

In this paper, the Xanthoceras sorbifolia natural populations were taken as the researchobject, and propagation mode, propagation characteristic, propagation strategy, age structure,spatial distribution pattern of them were studied in different habitat in hill loess plateau innorth shaanxi by research of typical plot and controlled experiment, in order to analyze thesexual, asexual propagation capacity and propagation strategy, partition natural type andselect the fine tree, as well as analyze seed size and plant drought resistance, thus, providingbasis for natural protect and resources cultivation. The main results were as follows:（1）Through study the sexual propagation ecology of Xanthoceras sorbifolia indifferent habitat, it was showed that the sexual propagation process was completed indifferent slope. Sunny slope had biggest flowering and fruiting capacity compared withsemi-sunny slope and semi-shady slope. The fruits were mainly distributed in the upper andmiddle canopy. The probability of seed conversion to one-year-old seedling was low, thenumber of seedlings were fewer in three slopes. With the grow-up of seedling age, seedlingnumber reduced gradually. The number of seedling may not realize completely sustainedregeneration of the population. Sunny slope provided favorable condition for seedlingestablishment. Seedling of sunny slope height, base diameter growth and biomassaccumulation were superior to semi-sunny slope and semi-shady slope. Light was positivecorrelation to seed number per Xanthoceras sorbifolia individual and seedling biomassaccumulation. Soil water was negative correlation to seedling number.（2） Through study the asexual propagation of Xanthoceras sorbifolia population, it wasshowed that in this region exists as three modes: sprouts from main root, sprouts from rootand sprouts from stump. Sprouts from main root have bigger contribution for populationregeneration. The asexual remets growth showed that sunny slope＞semi-sunny slope＞semi-shady slope. The asexual remets growth showed that stump sprouts＞main root sprouts＞root sprout in three slopes. The asexual propagation ability was the biggest in semi-sunny slope, and the smallest in semi-shady slope. With increase of stump height, sprout numberand growth increased. When the stump height reached10.1-15cm, sprout number was thebiggest. The stump diameter was positive correlation to sprouts number and growth. Cuttingroot diameter had the positive correlation with sprouts number, base diameter and crown.Sprouts height increased with the diameter increasing, when cutting root diameter exceed thevalue, sprouts height decreased gradually. When sprouts number of per stump or root exceedthe value, it was disadvantageous to sprouts growth.（3）Xanthoceras sorbifolia population had the sexual and asexual propagation in3slopes,but it exists a balance between two propagation modes. The ratio of seedling and asexualremets was more than1in sunny slope and semi-shady slope. It showed that Xanthocerassorbifolia population main propagation mode was sexual propagation in two habitats. Insemi-sunny slope, the ratio of seedling and asexual remets was less than1. It showed thatXanthoceras sorbifolia population main propagation mode was asexual propagation in thishabitat. Sexual propagation bottleneck stage appeared from seed to seedling. However,asexual propagation bottleneck stage appeared from seedling to remets. In the same habitat,seedling growth showed that asexual remets＞seedling. The same origin seedling growthshowed that sunny slope＞semi-sunny slope＞semi-shady slope. The way of Xanthocerassorbifolia invasion by seed was to settle in new habitat, and then occupied the space rapidlyby asexual propagation.（4）According to the research of the age structure and the spatial distribution ofXanthoceras sorbifolia population, the result showed that the age structure of Xanthocerassorbifolia population was progressive, the number of young growth individuals was morethan these of half-mature and mature individuals. The life tables present that the mortalityrates were highest at age class Ⅱ, decreased with age increasing, and gone up again at ageclass Ⅴ and Ⅵ owing to plant decrepitude. The survival curve belongs to the type of DeeveyⅢ, and the spatial distribution of population was aggregative pattern generally, theaggregative intensity was decreased and tended to a random distribution along with ageincreasing，was greater in semi-sunny slope.（5）According to growth and fruiting characteristic, the natural type of Xanthocerassorbifolia population may be divided into low yield tree patterns, low yield shrub patterns,high yield tree patterns, low yield shrub patterns in the hill loess plateau in north Shannxi.The ratio of low yield tree and shrub pattern was more in this region. According to thestandard of plus tree selection,30plus trees were selected in this region by factor analysis.Fu-county was16,9in Renjiatai,7in Jiaodao slope, respectively. Yan’an city was14,6inRetai village,8in Gonglu mountain, respectively. （6）The effects of seed size and Xanthoceras sorbifolia drought tolerance were studied.The results showed that germination percentage decreased gradually in all seeds withdecreasing water potential. The reduction was more significant under-0.6MPa treatment thanunder the-0.2MPa treatment in all seeds. The germination percentage of the big seeds was thehighest in all treatments and had the earliest initiated germination compared with those of themedium and small seeds. Lipid peroxidation (malondialdehyde), osmotic substances (freeproline), and antioxidative enzymes (peroxidase, superoxide dismutase, and catalase)increased in all seeds with increasing water stress. The values of all parameters indicated thatwater was a critical factor in Xanthoceras sorbifolia seed germination, and the big seedsdisplayed increased tolerance to water stress as measured by germination percentage,osmoregulatory substance, and antioxidant enzymatic activities.