准噶尔盆地东南缘梭梭种子雨特征

为了研究梭梭种子散布规律,通过布设种子雨收集器结合室内实验分析,对准噶尔盆地东南缘梭梭种子雨特征进行了研究。研究显示:(1)梭梭种子雨的累积密度达到平均189粒/m2,其中有活力种子占约80%;(2)种子散布的高峰集中在11月初到11月15日时间段,其落种量占整个种子雨的65%。其后种子雨密度随时间逐渐减小;(3)整个种子雨过程,不同时期散落的种子雨质量存在差异,表现为不同时期散落种子的萌发率呈现出先增大后减小的趋势;(4)变异函数分析表明,梭梭种子雨在8.12 m的有效变程内,种子雨具有明显的空间格局,其由空间自相关和随机因素引起的空间异质性各占50.0%。准噶尔盆地东南缘梭梭种子雨密度大且质量较高,同时其时空分布异质性较高,这些特征均将影响梭梭种群的分布格局和种群更新。

Characteristics of seed rain of Haloxylon ammodendron in southeastern edge of Junggar Basin

The Junggar Basin, located in the northern part of Xinjiang Autonomous Region, China, lies at the northern edge of the arid region in northwestern China. The Gurbantünggüt Desert, in the middle of the basin, makes up the main part of the Junggar Basin. The most concentrated populations of Haloxylon ammodendron, an important species for stabilizing desert ecosystems, are in the Junggar Basin. This study looked at seed rain patterns of this species in the southeastern edge of the Junggar Basin. Precipitation rarely occurs in this area of high temperatures. This basin is mainly composed of fixed and semi-fixed sand dunes so the natural environment of this species is quite fragile. H. ammodendron is a special desert shrub which grows larger than other desert shrubs. It is the most important native species here and is very well adapted a variety of harsh desert environments. This key species is widely distributed in gaps between the fixed and semi-fixed sand dunes and also grows into the lower part of the fixed and semi-fixed sand dunes and even forms pure forest. The local desert vegetation dominated by H. ammodendron, called H. ammodendron forest, provides a green barrier which benefits local economic and social development, and has significant effects on maintaining and stabilizing the local desert ecosystem. The key to sustainably maintaining and developing local desert vegetation is achieving natural regeneration of H. ammodendron. The seed is both the starting and end point of the plant life cycle. The stage at which seed rain occurs, an important phase of the plant life cycle, is the key link to natural regeneration, directly impacting the spread of plant seeds and decisively influencing seed germination, seedling survival, plant growth and a series of ecological processes. The seed rain of H. ammodendron on the southeastern edge of the Junggar Basin was studied by laying seed rain traps and using laboratory experiments. The aim was to survey the temporal dynamics and spatial distribution of seed rain to determine the laws and factors impacting seed dispersal. This study focused on the quality and quantity of seeds during different phases of seed rain. The results show (1) the cumulative annual seed rain intensity reached 189 seeds/m², although in some small local environments it reached as high as 2413 seeds/m² with viable seed comprising 80% of the total seed rain. (2) The peak period of seed rain was early November, producing 65% of the total seed rain. Subsequently seed rain density decreased gradually with time. The seed rain density stabilized in early December and the process of seed rain essentially ended by mid-January. (3) Seed quality varied considerably during the process of seed rain and the germination rate of seeds dehiscing in different times tended to increase at first and then decreased later. The highest quality seeds fell in early December and had a germination rate as high as 82.57%. (4) Semivariogram analysis revealed significant spatial seed rain patterns within an effective range of 8.12 m; 50.0% of the spatial heterogeneity was caused by spatial autocorrelation and 50.0% was caused by random factors. In summary, H. ammodendron produces a high quality and high intensity seed rain at the southeastern edge of the Junggar Basin with a relatively high temporal and spatial heterogeneity. These characteristics would be expected to influence the distributional patterns and regeneration of H. ammodendron populations.