模拟采食干扰下克隆整合对两种箭竹分株种群更新的影响

动物对植物的采食会刺激植物进行补偿性更新生长, 克隆整合效应能够通过分株之间的物质传输增强克隆植物的这种补偿生长。现今对克隆整合效应在箭竹(Fargesia)补偿更新中的作用仍未得到全面认识。2011年10月到2012年11月, 设立了糙花箭竹(Fargesia scabrida)和缺苞箭竹(F. denudata)各40个样方, 分别进行不剪除样方内分株和剪除样方内分株数量的25%、50%、75%四种模拟采食干扰处理, 并将样方四周的根状茎切断或保持连接。从2012年6月起观测并统计了箭竹分株种群的累积出笋率、总出笋率、补充率, 以及新生分株的株高、基径和单株生物量。结果表明: (1)在不剪除分株的样方, 切断根状茎连接显著增加了糙花箭竹的出笋率和补充率, 但降低了新生分株的株高和单株生物量, 也显著降低了缺苞箭竹的出笋率和补充率; (2)保持根状茎连接时, 25%的剪除强度仅仅降低了糙花箭竹新生分株的单株生物量; 同样在保持根状茎连接的条件下, 25%、50%的剪除强度使缺苞箭竹种群的补充率有所降低, 而切断根状茎后缺苞箭竹在25%的剪除强度下的分株补充率反而升高; (3) 75%的剪除强度并未影响两种箭竹新生分株数量更新, 但造成新生分株质量显著下降; 切断根状茎连接显著降低了糙花箭竹的新生分株的株高和基径, 对缺苞箭竹影响不显著。实验证明克隆整合影响了两种箭竹新生分株的萌发、存活和生长, 但不是两种箭竹进行补偿更新的主要机制, 仅在糙花箭竹分株种群受到重度采食干扰后的更新中才起到明显的促进作用; 两种箭竹均能在50%的剪除强度下通过补偿生长恢复种群的稳定, 75%的剪除强度则会造成箭竹新生分株质量的下降。

Effect of clonal integration on ramet population regeneration of two Fargesia (bamboo) species under simulated ingesting interference

Aims Herbaceous species can have compensatory growth after grazing. Clonal integration contributes greatly to the re-growth of clonal plants. To date, however, very few studies have addressed how clonal integration affects bamboos’ regeneration at a ramet level. Our objectives were to test the following hypotheses: (1) clonal integration benefits bamboo’s compensatory growth greatly after grazing and (2) differences in branching pattern of rhizomes lead to different contributions of clonal integration to the compensatory effects.
Methods In Tangjiahe National Nature Reserve, we subjected Fargesia scabrida and F. denudata ramets within 1.2 m × 1.2 m plots to four clipping treatments, i.e., no clipping and 25%, 50% and 75% shoot removal, and kept rhizomes at the plot edges either connected or disconnected.
Important findings In plots with no clipping, rhizome severing stimulated new shoot generation and population recruitment of F. scabrida, but reduced the height and biomass of new shoots. The shooting rate and recruitment of F. denudata were significantly decreased in plots where rhizomes remained connected. When rhizomes were kept connected, 25% clipping reduced the biomass of F. scabrida, and 25% and 50% clipping reduced recruitment of F. denudata. However, rhizome severing increased the recruitment of F. denudata. Under 75% clipping, the recruitments of both bamboos did not decrease significantly, but the quality of new shoots declined. Such negative effects were negated or greatly ameliorated in F. scabrida when rhizomes were connected. In general, clonal integration contributes greatly to the growth of new ramets, but contributes little to compensatory growth of both bamboos after grazing.