Seed Rain, Seed Banks And Seedling Banks Of Castanopsis Fargesii & Schima Superba In Damaged Evergreen Broad-leaved Forest, Tian Tong

Evergreen Broad-leaved Forest is widely distributed in the subtropical east of China as the typically zonal vegetation type dominated by Castanopsis fargesii Franch and Schima superba Garden, two evergreen and long-lived species which have extremely important function to maintain ecosystem's stability and community's structure. Many researches had been carried on population and community of these two dominated species at present, but what reproductive strategies of C. fargesii and S. superba should take to adapt the disturbing condition? How about their recovery abilities to the damaged population and community structure? What were the limiting factors restricted population regeneration from the seed dispersal stage to seedlings phase? All these importantly ecological questions are still poorly understood even to now, so it must be taken into much account on these aspects. We chose three communities which endured different damaged level in this dissertation, Based on field observation and experiment from March 2003 to December 2004, the several life history stages of the two dominated species from seed dispersal to seeds germination were involved, and all data obtained about seed rain, seed bank and seedling bank were analyzed with software Stat and Origin by computer. The main results are provided as follows:1. The characteristics of seed dispersal about C. fargesii and 5. superbaBased on seeds collected in seed traps and 0.25m² plots set on ground after seed falling, using regressive analysis, statistically test and model simulation, we mainly and systematically focused on the characteristics of the two dominant species. The results indicated that:The duration time of seed rain observed from the five C. fargesii samples was about 45 days, from 3rd, November to 16th, December, with a distinguishable dropping peak between 18th and 27th November, but seed rain of 5. superba dropped from the middle of September to the middle of October. The average seed rain density estimated from the traps deployed under the crown of C. fargesii was 81.3 seeds m^-2, and the viable acorns was 22.3 seeds m^-2 but only 11.2 seeds m^-2 for S. superba. There had no difference on dropping density in four directions of two species, One-way ANOVA showed F= 0.611, P >0.05 for C. fargesii and F = 0.348, P >0.05 for 5. superba individually.Of the total seeds collected by traps, the viable accounted for 27.3%, the immature 25.7%, the eaten by rodents 5.0%, infected by larvae 42.0%, furthermore acorns dropped on ground still would be predated by rodents after seed rain finished, but the proportion of seeds of S. superba only 3.8% was predated by larvae. Comparative results showed predation was the main limiting factor affected C. fargesii's acorns living fate, and restricted population regeneration, but to S. superba seeds rotted was the main limited factor. Acorns on ground mainly distributed under within 8 m from trunk and the spatial pattern fitted the quadratic distribution, on the other hand the negative exponential model didn't fit seed dispersal of S. superba well, the maximal coefficient R²=0.68, the minimum R²=0.12, and maybe the negative exponential didn't fit seed dispersal in the interior of forest.2. The characteristics of Seed bankThe quantity of seeds in soil seed bank distribution and its dynamics of the two species were analyzed and discussed based on the three stages investigation on soil seed bank in damaged communities, and the detailed investigating time was seed rain completely finished, the beginning of March and the end of May.The initial amounts of C. fargesii seeds in soil seed bank in lm²xl0cm plot of three damaged communities were 11.2, 0.8 and 0.5 independently, and seeds of S. superba were 11.2, 32.5 and 22.7 form plot 1 to plot 3. For the two species the number of viable seeds in seed bank were reducing constantly as time passed on but the detailed period were different, and S. superba took place in the beginning of March because large amounts of seed geminated but C. fargesi suffering the losing during Janu...