ON SOME NEW TETRACORALS FROM THE CARBONIFEROUS OF CHINA

Although Lower Carboniferous tetracorals of China have long been extensively described, thoseof younger Carboniferous have not received the due attention that they seem to deserve. Thepresent paper intends to deal with some scattered collections from the Carboniferous of Northand South China, which have been put at the author's disposal in the course of many a year.     

Nitrogen deposition and forest nitrogen cycling along an urban–rural transect in southern China

There is increasing concern over the impact of atmospheric nitrogen (N) deposition on forest ecosystems in the tropical and subtropical areas. In this study, we quantified atmospheric N deposition and revealed current plant and soil N status in 14 forests along a 150 km urban to rural transect in southern China, with an emphasis on examining whether foliar δ¹⁵N can be used as an indicator of N saturation. Bulk deposition ranged from 16.2 to 38.2 kg N ha^?1 yr^?1, while the throughfall covered a larger range of 11.7–65.1 kg N ha^?1 yr^?1. Foliar N concentration, NO₃^? leaching to stream, and soil NO₃^? concentration were low and NO₃^? production was negligible in some rural forests, indicating that primary production in these forests may be limited by N supply. But all these N variables were enhanced in suburban and urban forests. Across the study transect, throughfall N input was correlated positively with soil nitrification and NO₃^? leaching to stream, and negatively with pH values in soil and stream water. Foliar δ¹⁵N was between ?6.6‰ and 0.7‰, and was negatively correlated with soil NO₃^? concentration and NO₃^? leaching to stream across the entire transect, demonstrating that an increased N supply does not necessarily increase forest δ¹⁵N values. We proposed several potential mechanism that could contribute to the δ¹⁵N pattern, including (1) increased plant uptake of ¹⁵N‐depleted soil NO₃^?, (2) foliage uptake of ¹⁵N‐depleted NH₄⁺, (3) increased utilization of soil inorganic N relative to dissolved organic N, and (4) increased fractionation during plant N uptake under higher soil N availability.     

苹果绵蚜生活史与防治研究

1.苹果绵蚜在青岛地区1年中最高繁殖代数为17代,平均8—9代。 2.绵蚜1年中繁殖率从6月中旬至7月中旬(22—25℃)为最高,当平均气温连续多日高达26℃以上时其繁殖率显著下降。生长季节一般低温对绵蚜总繁殖率影响不大。 3.夏季有翅蚜发生时期为5月下旬至6月下旬,为数较少,出现时期也很零散,可胎生无翅胎生绵蚜与雌雄性蚜。秋季有翅蚜自8月底开始发生,盛期在9月中旬至10月中旬,10月中旬以后即极少发生,其后代为雌雄性蚜。 4.有翅蚜无口吻,约于7—9日内脱皮4次即行交尾,雌蚜仅产卵1粒,未经交配者不产卵。性蚜自然死亡率很高(平均81.2％),在田间尚未发现有越冬卵。 5.棉蚜主要越冬场所均在其原寄生部位,如伤口、裂缝内与根部不定芽上。越冬虫态以Ⅰ、Ⅱ龄绵蚜为主。 6.绵蚜之迁移以Ⅰ龄若虫为主,5月下旬至7月中旬为主要迁移为害时期。 7.绵蚜可在苹果的萼洼内寄生为害。 8.除西洋苹果、山荆子、花红与海棠外,尚未发现绵蚜有其他寄主。 9.20倍松脂合剂加0.02％γ可湿性666或5％—6％蒽油乳剂,为防治越冬绵蚜的有效药剂。生长季节可用666乳剂或可湿性666防治。 10.666酸霉味对果实品质能引起不良影响,经初步试验其施用时期最晚不应迟于采收前1个半月至2个月。     

Optimal size of storage for recovery after unpredictable disturbances

Terrestrial plants often live in environments in which above-ground photosynthetic organs (production parts) are suddenly removed by unpredictable disturbances, such as fire, frost, desiccation, pathogen attack, breakage by wind and trampling, or herbivory by insects and mammals. We study the optimal growth schedule for a plant having a below-ground storage organ that is used for recovery (or regrowth) of photosynthetic organs after disturbances. We assume the following: (1) the daily production rate increases with the production part size, but saturates for large size due to shading and local resource depletion, (2) disturbances occur randomly and remove all the aerial parts, (3) plants are finally killed by fatal disturbances that also occur randomly and (4) the plant chooses the pattern of growth, reproduction, storage and recovery after disturbances by reallocation of stored material to maximize the total lifetime reproductive success. The model is analysed by stochastic dynamic programming. The results are as follows: (1) the ratio of storage size to production part size (S/F ratio) is large if the longevity is large and if the disturbance rate is large but a little smaller than the productivity coefficient, (2) the S/F ratio is larger for mature plants than for small immature plants, (3) after disturbances, the above-ground production part recovers relatively quickly, but reproductive activity is depressed until storage size recovers and (4) the variations over time and between habitats differing in disturbance frequency are larger for storage size and for reproductive activity than for production part size. These tendencies are more pronounced for a linear production function (with initial linear increase followed by a sudden stop), but less so for a hyperbolic production function (with a gradually decreasing slope). We also discuss the growth and regrowth behaviour of plants adapted to a disturbance frequency growing under one different disturbance frequency.