Abstract:

Aims The subject of plant functional traits, which reflect plant growth and survival strategies, is an important trending topic in plant ecology. In this study, we selected three native warm temperate shrub species in China: Vitex negundo var. heterophylla, Ziziphus jujuba var. spinosa, Grewia biloba var. parviflora and two alien species: Amorpha fruticosa and Rhus typhina, to compare their growth and survival strategies.
Methods The differences in growth strategies were analyzed by measuring plant functional traits. This experiment was carried out at Fanggan ecological experimental station of Shandong University in Jinan. The seeds of five shrubs were germinated and 20 seedlings of each species were planted in pots containing a mixture of sand and humus (2:1, by volume). The leaf structural traits, leaf nitrogen, phosphorus and potassium, chlorophyll content, leaf gas exchange parameters, chlorophyll fluorescence, biomass, and seedling growth parameters were measured.
Important findings Physiological and ecological characteristics of five shrub seedlings were different under the same condition. 1) The alien species, i.e. R. typhina and A. fruticosa, showed high photosynthetic rates and had a strong ability to adjust to the instantaneous change of light intensity, which may be beneficial for plants to make full use of sunflecks under the canopy. The high supporting structure ratio of A. fruticosa is also more conducive to leaf movements, thus adjusting to the changeable light environment. The supporting structure ratio of A. fruticosa was as high as 0.434, which is conducive to its leaf movement and adjustment to the changeable light environment. The high photosynthetic capacity of R. typhina and A. fruticosa was the vital reason for the establishment of the two alien species. 2) The local species V. negundo var. heterophylla and Z. jujuba var. spinosa demonstrated relatively conservative utilization of resources, and in both of them low gas exchange values were measured. However, V. negundo var. heterophylla could make full use of the midday light. 3) G. biloba var. parviflora showed strong gas exchange capacity, and the actual quantum yield of diurnal variation of fluorescence was slow to recover in the afternoon as demonstrated by the chlorophyll fluorescence analysis. In addition, Grewia biloba var. parviflora had the lowest specific leaf mass (44.539 g·m^-2) and chlorophyll a/b (2.215), which confirmed that it is a shade-tolerant plant. Traits such as good seed dispersal ability, leaf heat dissipation ability, conservative light energy utilization strategy, and strong ability to recover after disturbance, help V. negundo var. heterophylla become the dominant species in the warm temperate zone of China. In summary, our study is helpful to understand the growth strategy and niche differentiation mechanisms in several common shrubs of warm temperate zone of China and provides theoretical basis for vegetation restoration, vegetation reconstruction and sustainable development of regional ecological environment.

Key words: growth strategy, leaf trait, physiological ecology, plant functional trait, shrub