辽东山区长白落叶松(Larix olgensis)种子雨和种子库

On seed rain and soil seed bank of Larix olgensis in montane regions of eastern Liaoning Province,China

长白落叶松是东北地区主要的用材树种，其种子雨和种子库研究鲜见报道。在辽东山区用收集器收集的种子分析了长白落叶松种子雨组成、质量和扩散距离，每隔2个月调查1次种子库数量，并结合靛蓝染色法测定每次种子的活力来分析土壤种子库动态。结果表明，辽东山区的长白落叶松种子雨从8月中旬开始，9月末到10月初达到高峰期，11月初结束。在起始期，种子雨以干瘪的不完整种子为主，而从高峰期开始，种子雨以完整种子为主。整个长白落叶松种子雨中不完整种子约占种子雨总量的45％，这些不完整种子由被动物取食、空粒和病虫害危害种子组成。完整种子的平均生活力为56．4％，即有活力的种子仅占整个种子雨的30％。种子雨集中在母树周围，在林缘1次扩散距离一般不超过1．5倍树高。种子雨到达地面之后，主要分布在枯枝落叶层，土壤0—5em层有少量分布，土壤5em以下没有种子分布；土壤种子库的种子主要在翌年雪融化后开始萌发、被取食、搬运以及腐烂，其中腐烂种子数占45．4％，动物取食为30．0％。种子库的种子数量和活力在冬季没有明显变化，而在翌年，种子数量和活力明显减少，4、6月和8月份种子数量分别为（506．3±35．56）粒m^-2，（267．1±17．47）粒m^-2和（143．6±9．83）粒m^-2，对应的活力分别为47．8％±4．68％，19．4％±3．39％和0％，这表明长白落叶松种子不能在地面形成连续的种子库。

Larix olgensis is one of the important commercial timber tree species in northeastern China, but there was little information about its seed resources. This study evaluated the composition, quality and dispersal distance of seed rain, and the distribution, amount and viability of seeds in soil seed bank of Larix olgensis in montane regions of eastern Liaoning Province. The seed rain was collected using collecting net at 50 --80 cm above forest floor and on the surface soil. The viability of seeds from seed rain was measured using the method of indigotin dying when the seed rain ended. Seeds in the soil seed bank were collected three times from April to August, and the viability of seeds was also examined by using the method of indigotin dying. The results showed that seed rain of L. olgensis started from the middle of August, reached the peak during the late September and early October, and ended at the beginning of November. At the beginning of the seed rain phase, the seeds were mainly made up by vacant seeds, but from the peak of the seed rain phase, the seed rain was mainly made up by intact seeds. The quality （ the amount of intact seeds and seed viability） of the seeds from the seed rain was relatively poor, and the un-intact seeds, which approximately accounted for 45 % of all seeds, were made of vacant seeds and seeds predated by animals and harmed by disease and insect pest as well. Furthermore, the viability of intact seeds was only average at 56.4 %. In consequence, the proportion of the viable seeds in the seed rain accounted for only about 30%. Seeds distributed around the parent trees in the primary dispersal of seed rain, and the dispersal distances of seed rain did not exceed 1.5 times tree height. Almost all of the seeds in the seed rain distributed on the litter layer, and there were a few seeds （ 〈 5 % ） entering the 0 --5 cm soil layer, and there was no seeds beneath 5 cm soil layer. The amount and viability of seeds did not reduce significantly after winter. However, the amount and viability of seed significantly reduced from April to August of next year. In April, June and August, the amount of seeds was 506.3 ±35.56 seeds m^-2, 267.1 ±17.47 seeds m^-2 and 143.6 ± 9.83 seeds m^-2, respectively, and the viability of seed was 47.8% ± 4. 68 %, 19.4% ±3.39 % and 0 % respectively, The results suggested that all seeds in soil seed bank lost their viabilities in the August of next year, and soil seed bank of L. olgensis was not persistent. The reason of losing the amount and viability of seed in soil seed bank was confirmed that the seeds were mainly consumed by germinated （ 〈 24.6 % ）, predated （30. 0 % ） and decayed （45.4 % ）.