| Schrenk spruce (Picea schrenkiana Fisch. et Mey.), the most important zonal vegetation of Tianshan Mountains in China, P. schrenkiana plays an important role in water conservation. However, natural regeneration has been problematic, which has been widely documented. It has been hypothesized that secondary metabolites released by litter and root secretion accumulates in the rhizosphere due to fire suppression, and these accumulated chemicals are autotoxic to the regeneration of P. schrenkiana. Previous results showed that the original water extract of P. schrenkiana needles and the diethyl ether, ethyl acetate, n-butanol soluble fractions of the original water extract and3,4-dihydroxyacetophenone (DHAP, which was separated in the diethyl ether fraction of a water extract of P. schrenkiana) all exhibited strong autotoxic effects on seed germination and seedling growth. The climate change in Northwest China shows a strong signals of climatic shift to a warm, humid pattern have been appearing in the Tianshan Mountain and neighboring regions since1987. Therefore, the effects of climate change on vegetation in this region have been the focus of concern.In this study, five areas which located at Zhaosu forest center, Gongliu forest center, Agricultrual university forest education center, National forest station and Hami forest center at tianshan mountains areas, twenty-three vertical transects, sixty-nine sampling points were determined according to the GPS. Real-time monitoring of soil temperature (Data from each sensor was recorded and transmitted via radio telemetry to a single base station with online data access and archive) was carried out during P. schrenkiana natural regeneration season, from April to July2001～2012. The temperature change (increase and decrease) were simulated by computer and analysed the change of autotoxic effect of the extract of P. schrenkiana needles, the diethyl ether, ethyl acetate, n～butanol soluble fractions and DHAP. The results were as following:1、In germination period (May15-June15), the core area of P. schrenkiana distribution (altitude2100-2300m), daily variation of soil temperature changes from9.4to15.2℃, night from3.6to5.5℃. Daily average temperature increases0.4-0.8℃and night0.2-0.4℃from2003to2012at the same time. Seedling growth period (June16-July15), daily variation of soil temperature changes from12.5to17.6℃, night from5.2 to7.9℃. Daily average temperature increases0.5～0.8℃and night0.3～0.6℃from2003to2012. Based on the above analysis, it determines daily temperature:12℃and night4℃as seed germination temperature and daily temperature:14℃and night6℃as seeding growth temperature.2、Seed germination rate, plumules and radicle length and fresh weight of seedling of P. schrenkiana increased significantly, Seed germination percentage did no significant change while the temperture rose; Seed germination rate, plumules and radicle length and fresh weight of seedling decreased significantly as temerature fell. The temperature change had significant effects on the P. schrenkiana at regeneration period. Water extract of litter (3.2mg/ml) had significant inhibition on seed germination and seedling growth of P. schrenkiana, the autotoxic effects will be enhanced as temperature rose or fell.3、Autotoxicity activity of low polar fractions (ether extraction phase) was significantly higher than that of the medium (ethyl acetate phase) and high (n～butanol phase). The inhibition activity of low polar fractions (each concentration) will be increased as temperature rose. Low concentration (1.0mg/ml) of medium and high polar fractions had promoted seed germination and seedling growth, and the promotion effect enhanced with the temperature increasing; Medium concentration (2.5～5.0mg/ml) inhibited seed germination and seedling growth, and the effects of elevated temperature on inhibitory effect was diverse; High concentration (10.0mg/ml) had significant inhibition to seed germination and seedling growth, and the inhibition effect could be enhanced as temperature rising.4、Very low concentration of DHAP solution (0.1mM) had a promotion effect on seed germination and seedling growth of P. schrenkiana, the effect of low concentration (0.5mM) on seed germination and seedling growth was between promotion and inhibition, then with the increase of concentration, the inhibition activity enhanced, this phonomense was in accordance with the law of autotoxin functioning "low promotion～high inhibition". The concentration of effect on transfer point of DHAP of P. schrenkiana was about0.5mM. Below the concentration of effect transformation point, the promotion effect of the temperature increase and autotoxicity showed additive effect which accelerating the procession of seed developmental. Inhibition effect of temperature decrease could be weakened by autotoxicity. Above the concentration of effect transformation point, the sensitivity of seed to DHAP was increased and showed that inhibition effects were enhanced as temperature rise. |
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