Primary production and resource use efficiency in relation to resource acquisition in deciduous and coniferous forest ecosystems

资源可利用性的变化会影响植物的养分利用效率。研究了林分特征、土壤养分有效性、气候条件和间伐对柏木林氮素利用策略的影响。研究区气候条件差异较大的是本州太平洋侧(高知县)、日本海侧(京都北部地区)和内陆地区(京都龟井市)，年平均气温为9.1~16.3℃，年平均降水量为1 500~3 300 mm。在高知县和龟山县的每一片森林中，我们设置了两个试验区：其中一个试验区进行了间伐，另一个试验区不砍伐树木作为对照。本研究发现，氮素营养状况的显著影响因素如下。在间伐试验中，间伐小区的氮素再吸收效率高于对照小区。凋落物中的氮素浓度在…时较低13年来，高知森林从3月到10月的太阳辐射较高。结果表明，氮素利用效率(NUE)随着光能利用率的增加而增加。相比之下，年降雨量较大的森林凋落物中的氮素浓度并不低，这表明氮素利用效率并不随水分利用率的增加而增加。气候条件较暖时，年落叶50%的时间较晚。落叶时间越晚，凋落物N浓度越低。结果表明，当气候条件适宜时，氮素利用效率增加。此外，台风大风对海拔较高的林分植物的影响较大。在这些林分中，年落叶50%的时间较早，且落叶的氮素浓度较高。结果表明，柏树NUE与落叶物候密切相关，落叶物候受温度和台风的影响。研究结果表明，气候条件以及资源的可获得性都会影响柏木的NUE。较少

Changes in resource availability can affect nutrient use efficiency of plants. We investigated the effects of stand characteristics, soil nutrient availability, climatic condition and thinning on nitrogen use strategy in hinoki cypress stands. The study areas were Pacific side of Honshu (Kochi prefecture), Japan Sea side (northern region of Kyoto prefecture) and inland region (Kamigamo, Kyoto city) where climate conditions differ substantially; the means of annual temperature and mean annual precipitation in the stands ranged from 9.1 to 16.3℃ and from 1500 to 3300 mm, respectively. In each forest in Kochi and Kamigamo, we located two study plots: in one plot thinning was conducted and in the other plot no trees were cut as the control. We found the significant effects on nitrogen status of hinoki as following. Nitrogen resorption efficiency was larger in the thinned plots than in the control plots in the thinning experiments. The nitrogen concentration in the leaf litter was lower whe … More n solar radiation from Mardi to October was higher in Kochi forest for 13 years. The results suggest that nitrogen use efficiency (NUE) increases with increasing light availability. By contrast, nitrogen concentration in leaf-litter was not lower in forests with higher annual precipitation, suggesting that NUE does not increase with higher water availability. The time of 50 % annual leaf-fall was later in the warmer climatic condition. Leaf-litter N concentration was lower when leaf-fall occurred later. The results suggest that NUE increases when the climatic conditions are favorable. In addition, the effects of strong wind in typhoons on plants are greater in the stands at higher elevation. In these stands, the time of 50 % annual leaf-fall was earlier and hinoki trees shed their leaves with higher nitrogen concentration. The results indicate that NUE of hinoki cypress is closely related with leaf-fall phenology that is affected by temperature and typhoon. The results of the study suggest that the climatic condition as well as resource availability affects NUE of hinoki cypress. Less