Leaf litter decomposition and nutrient dynamics in a subtropical forest after typhoon disturbance

Decomposition of typhoon-generated and normal leaf litter and their release patterns for eight nutrient elements were investigated over 3 yr using the litterbag technique in a subtropical evergreen broad-leaved forest on Okinawa Island, Japan. Two common tree species, Castanopsis sieboldii and Schima wallichii, representative of the vegetation and differing in their foliar traits, were selected. The elements analyzed were N, P, K, Ca, Mg, Na, Al, Fe and Mn. Dry mass loss at the end of study varied in the order: typhoon green leaves > typhoon yellow leaves > normal leaves falling for both species. For the same litter type, Schima decomposed faster than Castanopsis. Dry mass remaining after 2 yr of decomposition was positively correlated with initial C:N and C:P ratios. There was a wide range in patterns of nutrient concentration, from a net accumulation to a rapid loss in decomposition. Leaf litter generated by typhoons decomposed more rapidly than did the normal litter, with rapid losses for N and P. Analysis of initial quality for the different litter types showed that the C:P ratios were extremely high (range 896 – 2467) but the P:N ratios were < 0.05 (range 0.02 – 0.04), indicating a likely P-limitation for this forest. On average 32% less N and 60% less P was retranslocated from the typhoon-generated green leaves than from the normal litter for the two species, Castanopsis and Schima. An estimated 2.13 g m^–2 yr^–1 more N and 0.07 g m^–2 yr^–1 more P was transferred to the soil as result of typhoon disturbances, which were as high as 52% of N and 74% of P inputted from leaf litter annually in a normal year. Typhoon-driven maintenance of rapid P cycling appears to be an important mechanism by which growth of this Okinawan subtropical forest is maintained.     

瓦屋山常绿阔叶次生林建群种扁刺栲的细根分布及其碳氮特征

四川瓦屋山国家森林公园是我国西部的中亚热带湿性常绿阔叶林的典型代表,具有四川现存的较为完好的扁刺栲(Castanopsis platyacantha)-华木荷(Schima sinensis)群系,该研究利用土钻法探讨了该群系内主要建群种扁刺栲标准木的细根分布及其碳氮特征。结果表明:(1)扁刺栲细根总生物量为173.62 g·m~(-2),其中活根生物量为135.29 g·m~(-2)。(2)随着土层深度的增加,扁刺栲细根生物量、根长密度、根系表面积和比根长呈下降趋势,0~30 cm土层所占比例分别为67.23%、69.53%、69.48%和57.20%;根长密度、根系表面积和比根长均随细根直径的增加而显著下降,直径小于1 mm的根系所占比例分别为58.84%、52.59%和51.36%。(3)扁刺栲细根生物量、根长和表面积消弱系数β均随根系直径的增加而增加。(4)根系C含量在第Ⅰ土层中随细根直径的增加而显著增加,在其他土层则无显著差异;直径小于2 mm的根系C含量在第Ⅰ土层中显著低于其他土层,大于2 mm的根系C含量在各土层间的差异不大。(5)根系N含量随根系直径和土层深度的增加而减少,C/N值则与之相反。该研究结果在一定程度上反映了该次生林地下细根的垂直分布及养分特征,为揭示该生态系统地下生态过程及今后在该生态系统研究环境变化对地下生态过程的影响提供了基础数据。     

Study on Energy of Castanopsis eyrei Community in Wuyi Mountains

Based on the measurement of biomass and productivity, the caloric value of plant samples, the standing crop of energy, net energy production and energy conversing efficiency of Castanopsis eyrei community were determined. There were some differences in caloric values among the fractions of C. eyrei community being highest in that of bark and lowest in that of the microroots. The standing crop of energy in C. eyrei community was 780584.1 kJ ·m-2, in which the standing crop of energy accumulated in the aboveground biomass was 678913.8 kJ · m-2, accounting 86. 98% of the total; that of underground was 101670.3 kJ · m-2, i. e. 13.02%. Net energy production was 26856.2 kJ · m-2 · a-1 for this community in 1992. To the photosynthetic active radiation on the stand, the energy conversing efficiency was 1. 296%.     

福建三明瓦坑的赤枝栲林

本文讨论的赤枝栲1)(Castanopsis kawakamii)林,地处福建省三明市郊瓦坑地区,属我国中亚热带东南缘。据调查31块样地共3100m2群落种类组成中,含维管束植物52科、90属、139种;其中单种属占总数的75.6%。植物区系为热带、泛热带分布的成分、共占科与属总数的61.5%与67.8%。高位芽生活型植物占总数的87.9%。基于对群落外貌的植物生活型与叶特征等分析表明,该群落是从南亚热带雨林到中亚热带常绿阔叶林的过渡类型。对该森林乔木种的年龄结构分析,乔、灌木种多样性指数与均匀度的计算等,显示出赤枝栲林是相对稳定性较大的群落。     

中亚热带杉木人工林和米槠次生林凋落物添加与去除对土壤呼吸的影响

在未来大气CO₂浓度升高的背景下, 植被净初级生产力的增加将促使森林土壤碳输入增多。凋落物是土壤碳库的重要来源, 对土壤呼吸会产生重要影响。为了模拟植物净初级生产力提高、凋落物产量增加情景下凋落物对土壤呼吸和土壤碳库的影响, 2013年1月到2014年12月, 在福建省三明市陈大镇国有林场, 在杉木(Cunninghamia lanceolata)人工林和米槠(Castanopsis carlesii)次生林, 通过设置去除凋落物、添加凋落物和对照(保留凋落物, 不做任何处理)处理, 研究了土壤呼吸和土壤碳库的动态变化。研究发现: 土壤含水量在10%-25%范围内, 土壤呼吸温度敏感性指数(Q₁₀)随着土壤含水量的增加呈递增趋势, 当含水量<10%时, 由于干旱胁迫打破了土壤呼吸与温度之间的耦合, 改变了Q₁₀值, 使得Q₁₀值小于1。土壤呼吸与凋落物输入量呈显著的线性正相关关系, 杉木人工林对照和添加凋落物处理及米槠次生林对照处理, 土壤呼吸与2个月前的凋落物输入量相关性最好。而米槠次生林添加凋落物处理, 土壤呼吸与当月的凋落物输入量相关性最好, 不同林分凋落物呼吸对土壤呼吸的贡献率不同, 米槠次生林凋落物层呼吸年通量明显大于杉木人工林, 分别占各林分土壤总呼吸的34.4%和15.1%, 添加凋落物后, 杉木人工林和米槠次生林的土壤呼吸速率增加, 但添加凋落物处理的土壤呼吸年通量与对照的差值小于年凋落物输入量。因此, 在未来全球CO₂升高背景下, 植被碳储量的增加、凋落物增加并没有引起土壤呼吸成倍增加, 更有利于中亚热带地区土壤碳吸存。     

Glacial bottleneck and postglacial recolonization of a seed parasitic weevil, Curculio hilgendorfi, inferred from mitochondrial DNA variation

Climatic changes during glacial periods have had a major influence on the recent evolutionary history of living organisms, even in the warm temperate zone. We investigated phylogeographical patterns of a weevil Curculio hilgendorfi (Curculionidae), a host-specific seed predator of Castanopsis (Fagaceae) growing in the broadleaved evergreen forests in Japan. We examined 2709 bp of mitochondrial DNA for 204 individuals collected from 62 populations of the weevil. Four major haplogroups were detected, in southwestern and northeastern parts of the main islands and in central and southern parts of the Ryukyu Islands. The demographic population expansion was detected for the two groups in the main islands but not for the Ryukyu groups. The beginning time of the expansion was dated to 39 000–59 000 years ago, which is consistent with the end of the last glacial period. Our data also demonstrated that the southwestern population of the main islands has experienced a more severe bottleneck and more rapid population growth after glacial ages than the northeastern population. At least three refugial areas in the main islands were likely to have existed during the last glacial periods, one of which had not previously been recognized by analyses of intraspecific chloroplast DNA variation of several plant species growing in the broadleaved evergreen forests. Our results represent the first phylogeographical and population demographic analysis of an insect species associated with the broadleaved evergreen forests in Japan, and reveal more detailed postglacial history of the forests.     

格氏栲种群数量动态的谱分析研究

运用谱分析数学方法,研究分析格氏栲林格氏栲种群动态规律．结果表明：格氏栲种群数量动态的周期波动性是明显的,与格氏栲天然更新过程有关;不同生境、人为干扰均对辂氏栲种群数量动态的波动产生影响;格氏栲生长量的周期波动与其种群数量动态的周期波动特征基本一致,表明格氏栲种群数量动态呈周期波浪式发展,即表征格氏栲林优势种群的稳定性。     

水杨酸作用下东北红豆杉细胞的二维凝胶电泳分析

东北红豆杉悬浮培养体系中加入适量浓度的水杨酸,染色结果表明,水杨酸可以增加细胞膜通透性,并可诱导部分细胞发生核凝集或核碎裂。提取细胞染色体DNA进行琼脂糖凝胶电泳,发现染色体DNA发生了部分降解。应用蛋白质双向凝胶电泳技术,研究了水杨酸处理后东北红豆杉细胞发生应激反应过程中蛋白质的表达情况,分析了处理细胞与正常细胞的蛋白质组差异,发现在水杨酸处理48h后的样品中有7个蛋白质差异点,而且有6个蛋白点仅在对照中检测到。结果表明,外加水杨酸改变了东北红豆杉细胞的基因表达,抑制部分蛋白合成的同时也合成了部分新蛋白质,这些蛋白可能与水杨酸的作用有关。