Competition is an important factor in biology and plant鄄plant interactions has inspired an increasing concern in recent years. In plant communities, competition is defined as the interaction between individuals, brought about by limited resources. Aboveground competition is usually size鄄asymmetric: the bigger individuals have a disproportionate advantage in competing for light than the smaller ones. This study deals with biomass allocation patterns and aboveground competition influences on biomass partitioning and allometric equations of understory Korean pine (Pinus koraiensis). The results will contribute to understanding the mechanisms of aboveground competition and provide a theoretical guide for effective utilization and protection of Korean pine. The results show that: (1) When dividing live crown into three equal layers (top, middle and bottom) , live branch biomass increased from the top to the bottom layer, while needle biomass was highest in the middle and bottom layers of the crown. However, there was no significant difference between the needle biomass located at the middle and bottom layers (P > 0. 05). The relative proportion of coarse root (> 5 mm) biomass increased while that of small fine root (<2 mm) and coarse fine root (2-5 mm) biomass both decreased with increasing

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Changes of carbon input influence soil respiration in a Pinus tabulaeformis plantation.

In the context of global climate change, the research on soil respiration of the forest ecosystem has attracted more and more attention. However, there is not enough further discussion on forestry soil respiration which is affected by the heavy rainfall in domestic research reports. It is limited by the measurement technology at present. This study selected Pinus tabulaeformis plantation as the object in the Taiyue Mountain area, using the Li鄄8150 automated soil CO 2 flux system to monitor the soil CO 2 flux. The soil respiration rate was monitored continuously for about 14 days ( before, during and after) each of the three rainfalls respectively in situ, and the environmental factors were also measured simultaneously. The changes of soil respiration rate before, during and after each rainfall were analyzed then. The results showed that, (1) In May, the rainfall during the dry season improved the soil humidity and promoted the soil respiration. The soil respiration rate increased almost two times relative to the values before and after the rain;In July, the rainfall during the wet season beginning promoted the soil respiration first and inhibited it after. There was an inflection point in the quadratic curve between the soil volume water content and the soil respiration rate, but as a whole, that rainfall promoted the soil respiration;In August, the rainfall during the wet season inhibited the soil respiration. There was a mirrorimage relationship http: / / www. ecologica. cn between the soil respiration rate curve and the soil volume water content curve. During and after the rain, the soil respiration rate decreased about 45% and 28% respectively. (2) The soil temperature dropped to some extent after each rainfall. The lower temperature could both promote and inhibit the recovery process of soil respiration rate after rainfall.(3) The key factors that influenced the soil respiration were different during the different periods of rainfall in the semihumid P. tabulaeformis plantation. If the soil volume water content was changing constantly before the rainfall, the soil humidity would be the most influential factor; if it was in a stable state, the soil temperature would be. The soil humidity and temperature influenced the soil respiration together during the process of all the three rainfalls, and the soil humidity was always the most influential factor after all the three rainfalls.

kg N hm -2 a -1 ) ,低氮( LN,50 kg N hm -2 a -1 ) ,中氮( MN,100 kg N hm -2 a -1 ) 和高氮( HN,150 kg N hm -2 a -1 ) ,研究草本群落 的生物多样性、生物量以及草本元素含量对模拟 N 沉降的响应。 研究结果表明:模拟 N 沉降未能显著影响人工林草本群落的 生物多样性( P>0.05) ,而中氮、高氮显著降低了天然林草本群落的生物多样性( P<0.05) ;从 Jaccard 指数和 Sorensen 指数分析 得出人工林不同氮水平之间草本群落差异性较小,而天然林不同氮水平之间草本群落差异性较大。 模拟 N 沉降没有显著改变 人工林草本群落生物量 ( P>0.05) ,而高氮明显促进天然林草本群落生物量的增加( P<0.05) 。 与对照相比,模拟 N 沉降提高了 人工林和天然林羊胡子苔草叶根中的全 N 含量( P<0.05) ,而降低了全 Mg 的含量( P<0.05) ,并且根部元素含量变化与土壤养 分含量变化较为一致。 施氮提高了 N / K、N / Ca、N / Mg( P<0.