横断山区干旱河谷川滇蔷薇生长与繁殖特征的地理空间差异

通过大面积的野外踏查、种群调查和室内实验,分析了横断山区干旱河谷乡土灌木川滇蔷薇在岷江流域、大渡河流域、雅砻江流域和金沙江流域的分布、生长繁殖特征及其在流域间的差异。结果表明,川滇蔷薇广泛分布于四大流域,海拔范围1700m至3700 m,所调查的18个种群生长状况良好,株高2 m以上,明显高于群落中的其他灌木。主成分分析表明,地理位置(流域、纬度、经度、海拔)和土壤(全碳、总有机碳、全氮、pH值)是影响川滇蔷薇生长繁殖的主要因子,其中地理位置的影响更大。生长特征包括株高、地径和冠幅在18个种群间差异显著,但在不同的流域间差异不显著。丛萌生数在种群间差异显著,其差异性较其他生长特征弱,但丛萌生数在不同流域间差异显著:岷江流域显著大于雅砻江流域,金沙江流域显著大于大渡河流域。与生长和无性繁殖相比,有性繁殖特征表现出更强的空间差异性,果实重量、瘦果重量以及种子活力在居群间差异极显著,果实重量和种子活力在不同流域间差异显著,但瘦果重量在流域间的差异不显著。综合分析表明,川滇蔷薇生长和繁殖特征在横断山区干旱河谷存在较强空间差异性,较强无性繁殖是种群持续存活的保证,而有性繁殖及其强烈的空间差异为种群适应多变环境以及地理空间扩展提供了遗传基础。

Geographic variation in growth and reproduction of Rosa soulieana in the dry valleys of the Hengduan Mountain region

Understanding the geographic variation of the growth and reproduction characteristics of native plants may help to develop effective strategies for vegetation restoration in degraded regions. Rosa soulieana, a native shrub widely distributing in the dry valleys of the Hengduan Mountain region, appears to have a great potential to rehabilitate the vegetation because of its ecological and economic advantages. To determine the distribution, growth and reproduction of this species, 18 plots were investigated along the dry valleys of four rivers (Minjiang, Daduhe, Yalongjiang and Jinshajiang) in June and October 2011. Eight location parameters of each plot were recorded including drainage, latitude, longitude, altitude, slope gradient, slope aspect, position, and height from river. Ten clumps were randomly selected for measuring the growth parameter, and five clumps for reproductive parameters in each plot. Soil parameters were measured using samples collected from the five clumps that had been used to record reproductive parameters. The results indicated that R. soulieana was widely distributed in each dry valley of Hengduan Mountain region at altitudes from 1,700 to 3,700 m above sea level. Mean plant height was (2.64 ± 0.17) m, which was higher than that of other species in the community in the dry valley region. PCA and correlation analyses showed that location (drainage, latitude, longitude, and altitude) and soil traits (total carbon, total organic carbon, total nitrogen, and pH) were the principal factors influencing growth and reproduction, and location had a stronger influence than that of soil traits. Growth traits (height, base diameter, and crown diameter) differed significantly among the 18 populations, but not among drainages. Vegetative reproduction was high with a mean of (2.5 ± 1.9) ramets per individual, with a maximum of 25 ramets on a single individual. Ramet number per individual differed less among the populations than growth traits, but it was significantly different among drainages. R. soulieana also exhibited strong sexual reproduction. Seed vitality of 83.3% of the populations was > 80%. The reproductive parameters exhibited stronger spatial variation than growth traits. Fruit mass, achene mass, and seed vitality were highly significantly different among the 18 populations, but only fruit mass and seed vitality were significantly different among the four drainages. Fruit mass was significantly greater in the Yalongjiang drainage than in the other three. Seed vitality was greater in Minjiang and Jinshajiang drainages than in the Yalongjiang and Daduhe drainages. Comprehensive analysis showed pronounced geographic variation in growth and reproduction in R. soulieana in the dry valleys of the Hengduan Mountain region. Strong vegetative reproduction ensures the persistence of the populations, and sexual reproduction provides genetic material for this species to adapt to the environment and expand their distribution in dry valleys.