Reproductive potential of the alien species Asclepias Syriaca (Asclepiadaceae) in the rural landscape
Reproductive potential of the alien species Asclepias Syriaca (Asclepiadaceae) in the rural landscape
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乡村景观中外来物种萝藦科（萝藦科）的繁殖潜力
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
K. Penksza
中科院分区：
文献类型：
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作者：
P. Csontos;E. Bózsing;I. Cseresnyés;K. Penksza
紫云英(Asclepias syriaca L.)引种之初，在匈牙利被用作观赏植物。它在脱离耕作之后，在20世纪最后几十年得到了广泛的传播.如今，它覆盖了很大的面积，特别是在沙地土壤上，并有望在干旱、森林砍伐和退化地区进一步出现。选择了两块被遗弃的田地和一个被遗弃的葡萄园。抽样时，每个林分使用两个4m2大小的四倍体。林分的特征是：茎密度、生殖茎百分率、平均花序数、平均结果数、每茎每花序结果数、每茎结荚数、平均每果种子数。在同一样地中，对0~5 cm和5~10 cm两种深度的土壤种子库进行了研究。结果表明，荒地的林分密度、繁殖标本百分率和平均果龄均显著高于废弃葡萄园。荒地上层(2.7~18.6×103粒m-2)种子较多，下层较少，且只有一块田有种子。在废弃葡萄园的两层土壤中，常见的乳草种子几乎完全不见了。然而，从土壤中恢复的种子几乎没有萌发，这表明早年的种子已经失去了活力，即所研究的黑杨林没有形成持久的土壤种子库。然而，被忽视的田间种群的新鲜种子产量可达7-1万粒m-2，不仅在现场，而且在周围地区都可能造成非常强的繁殖负荷。
In the beginning of its intro- duction Common milkweed, Asclepias syriaca L. was used in Hungary as ornamental plant. After escaping from cultivation it has become wide spread during last decades of the 20 th century. Nowadays, it covers large areas especially on san- dy soils, and its further appearance is expected on dry, deforested and degraded areas. Two neglected fields and one abandoned vineyard were selected. For sampling two quad- rates of size 4 m 2 were used at each stand. The stands were characterized by the following vari- ables: density of stems, percentage of reproductive stems, average number of inflorescences, average number of fruits, fruits per all inflorescences on a stem, pods per fruited inflorescences on a stem, average number of seeds per fruit. In the same quadrates the soil seed bank was studied at two depths (0-5 cm and 5-10 cm). The results showed that the density of stand, percentage of reproductive specimens and aver- age number of fruits were significantly higher on the neglected fields than on the abandoned vineyard. In the neglected fields large number of seeds were detected in the upper soil-layer (2.7- 18.6 × 10 3 seeds m -2 ), but in the lower soil-layer much fewer seeds were found and only in one of the fields. Common milkweed seeds were almost completely missing from both soil layers of the abandoned vineyard. However, the seeds recov- ered from the soils practically did not germinat- ed, indicating that seeds of earlier years sets have lost viability, i.e. the studied stands of A. syriaca did not form a persistent soil seed bank. Never- theless, the fresh seed production of the neglected field populations, that can reach 7-10 thousands seeds m -2 , may cause a very strong propagulum load not only in the site but also on the surround- ing areas.