Expansion strategies of Caragana stenophylla in the arid desert region
The drought resistant shrub, Caragana stenophylla, is distributed mainly in the arid and semi-arid areas of the Inner Mongolia Plateau, China.C.stenophylla is an important fodder plant, and is known as “lifesaving plants" for the livestock in arid and semi-arid areas.In addition, it plays an important role in sand dune fixation and water conservation.We found that C.stenophylla individuals had only a few branches in the eastern grassland region of the Inner Mongolia Plateau, but in the western desert region, it formed the large shrubs with diameter of 1.5 - 2.0 m, accompanied by a sand dune with high of 50- 70cm, and showed strong sand-fixing ability.We hypothesized that such structural difference was due to the expansion strategies of C.stenophylla in desert region.In order to understand the expansion strategies and reproductive characteristics of C.stenophylla in the arid desert region, we studied the shrub structure, ramet characteristics, breeding tendency and branching characters of C.stenophylla clusters.The results showed that, in the arid desert region, C.stenophylla reproduced mainly by asexual reproduction.It reproduced ramets mainly by root germination and it had a clonal architecture of “phalanx".The ramets of C.stenophylla can separate from their parents and grow independently when spacer connecting ramets died and decomposed, which reduced the death risk of ramets being implicated each other.The C.stenophylla can also reproduced by branches which were buried by sand forming adventitious roots and shoots.When seed germination and seedling establishment is restricted by drought and animal predation, asexual reproduction can compensate for the shortage of seedlings, thereby maintain population stability.Thus, asexual propagation might be an important regeneration strategy for C.stenophylla in harsh environments.The stepwise bifurcation ratio of C.stenophylla was SBR3∶4＜SBR2∶3 ＜SBR1∶2, which indicated that the branches number increased year after year leading to a bigger and bigger cluster crown.Some C.stenophylla clusters were composite shrub, the formation of such C.stenophylla clusters might be because the parent shrub has constructed a suitable microenvironment for seed germination, and the new individuals could survived more easily under the protection.The parent shrub and surviving newborn individuals together formed large and composite shrub cluster.Thus, C.stenophylla shrubs expanded mainly by four ways: (1) root germination, (2) adventitious root reproduction of branches, (3) continuous branching of the aboveground part, and (4)composite shrubs of old and new individuals.Shrub expansion in size provided the necessary conditions for constructing a suitable microenvironment and searching for available nutrient and water resources, therefore enhancing the anti-stress ability.At the same time, large shrub clusters also enable C.stenophylla to have better ability in wind breaking and sand dune fixation, thus C.stenophylla plays a very important ecological role in the arid desert ecosystem.C.stenophylla had a well-developed root system, which enabled it to absorb more soil moisture and made it less susceptible to drought stress, and also contributed to its effective use of mineral nutrients from deep soil as well as decomposed litter.In summary, C.stenophylla is well adapted to the arid and barren environment by clonal propagation, shrub enlargement and well-developed root systems, which make it one of the dominant species in the desert region.
Caragana stenophyllaasexual reproductionshrub expansionarid desert region
国家科技期刊平台
NSTL
万方数据
维普
