Leaf Life History Of Eight Tree Species From Evergreen Broad-Leaved Forests In Tiantong,Zhejiang

The study of leaves plays an important role in phytoecology as leaves are the most basic organ of energy acquiring and the place of respiration and transpiration. However, a series of factors (such as different species or habitat heterogeneity) affect the tradeoff between leaves’ morphological structure and function, thus shaping the basic behavior and function of plants. As a result, this leads to different leaf life history strategies among different plant species. Therefore, leaf life history research can reflect the life history strategy of each species to a great extent.Evergreen broad-leaved forests are widely distributed in the subtropical region of China. However, there have been just few reports concerning leaf life history in this region now. In addition, it is more objective and effective to measure leaf traits by long-term continuous observation than by sampling only once. However, as long-term continuous observation is more time-consuming, it is seldom applied in current domestic research. So we selected8representative tree species from evergreen broad-leaved forests, which were located in Tiantong National Forest Park, Zhejiang Province. Based on long-term continuous field observation of the process of leaf growth from2011to2013, leaf demography, leaf dry mass per unit area (LMA) and photosynthetic capacity were measured. Then we analysed the interspecific variation and influence factors aiming to understand leaf life history of8tree species and accumulate basic research data in this respect for future research. The main results were as follows:(1) Based on field observation of leaf phenology in2011, the beginning of leaf emergence was in April or May. The earliest tree species was Schima superb whose leaf emerged in early April (Julian day=95d), while the latest tree species were Castanopsis carlesii and Castanopsis fargesii, their leaves emerged in mid-May (Julian day=135d). According to the duration time of leaf emergence,8species could be divided into flushing emergence (6species) and succeeding emergence (2species). All of5Fagaceae species in this research were flushing emergence, however there was difference in terms of the beginning of leaf emergence.(2) In our research, the leaf fall pattern of8tree species could be divided into unimodal and multimodal types.4species (C. carlesii, C. fargesii, S. superb and Myrica rubra) were unimodal type, however their peaks of leaf fall were in different period. The other4species(Cyclobalanopsis glauca, Cyclobalanopsis sessilifolia, Lithocarpus glaber and Daphniphyllum oldhamii) were multimodal type, and their peaks of leaf fall were also in different seasons.(3) The mean leaf longevity of8tree species in the evergreen broad-leaved forest was between1to2year from399.48d (C. fargesii) to727.98d (M. rubra). Their leaf lives in order were as follows:C. fargesii<C. glauca<C. carlesii<C. sessilifolia<S. superba<D. oldhamii<L. glaber<M. rubra。(4) There were differences among LMA dynamic of8tree species in the evergreen broad-leaved forest. First, from leaf emergence to LMA varied steadily,4species (D. oldhamii, C. glauca, C. carlesii and C. fargesii) showed a decline initially, and a rising after that.2species (C. sessilifolia and C. fargesii) showed an obviously rising tendency. The other2species (M rubra and L. glaber) did not changed obviously at first, but subsequently had a rising tendency. Second, the time of8tree species’LMA coming to steady-state were different. C. fargesii and L. glaber were in449d (March in2012). C. glauca, C. carlesii, M. rubra and C. sessilifolia were in415d (February in2012). D. oldhamii and S. superba were in317d (November in2011). C. glauca was in221d (August in2011). Third, in the steady-state, the trends of8tree species’LMA were also different. In a word,7species (except D. oldhamii) showed a phenomenon that the older leaf age, the larger LMA value. On the contrary, the LMA of D. oldhamii was higher in345d to478d (December in2011to April in2012), and then kept at a low level. In addition, during the period of720d to805d (December in2012to March in2012), D. oldhamii’LMA value had a slight increasing. In the end, during the period ranging from415d to449d (February to march in2012), all of these8tree species’LMA values showed a declining trend, which may be related with low temperature (heavy snow).(5) There was interspecific variation in photo synthetic capacity for the8tree species in the evergreen broad-leaved forest. First, after leaf emergence, the time of acquiring the maximum photo synthetic capacity of8species were different.6species (D. oldhamii, M. rubra, S. superb, C. glauca, C. sessilifolia and L. glaber) acquired their maximum photo synthetic capacity in July,2011. However, C. carlesii and C. fargesii spent a long time to acquire their maximum photo synthetic capacity (C. carlesii acquired Amax in November,2011, C. fargesii acquired Amax in December,2011). Second,7species’(except C. glauca) photo synthetic capacity obviously declined from347d to415d (December in2011to February in2012). And5species’(C. fargesii, D. oldhamii, M. rubra, S. superb and L. glaber) photosynthetic capacity also declined in723d (December in2012). These suggested the effects of low-temperature on photosynthetic capacity. In general, in three years, photosynthetic capacity in the next year was lower than the former year, which showed that leaf longevity had an important effect on photosynthetic capacity.(6) At last, we analysed the relationship among leaf longevity, LMA and photosynthetic capacity. Unfortunately, we didn’t found any obviousrelationships among the three traits.