落叶松幼苗碳素和氮素的获取与分配对供氮水平的响应(英文)

CARBON AND NITROGEN ACQUISITION AND ALLOCATION IN LARCH SEEDLINGS IN RESPONSE TO DIFFERENT N SUPPLY RATES

落叶松(Larix gmelinii)是中国东北林区最重要的工业用材树种,而且在北温带森林中具有重要的生态学意义。落叶松的种植区域内气温低、冬季长,氮素矿化速度低,供氮不足常常成为落叶松生长的限制因素。为揭示落叶松生长与氮素营养的关系,采用沙培法设置了1、4、8和16 mmol·L-1 4个供氮水平,研究了不同供氮条件下落叶松一年生幼苗对碳和氮的获取与分配的规律。结果显示,落叶松幼苗的生物量、全株氮浓度、氮含量、比氮吸收速率均随供氮水平的增加而升高,叶重比(LWR)、茎重比(SWR)及叶氮比(LNR)、茎氮比(SNR)亦随供氮水平的增加而增加,而根重比(RWR)和根氮比(RNR)则随供氮水平的增加而降低。当供氮水平从1 mmol·L-1增加至8 mmol·L-1时,落叶松幼苗相对生长速率呈线性增加,而全株氮生产力几乎未受供氮水平的影响;当供氮水平从8 mmol·L-1增加至16 mmol·L-1时,全株相对生长速率不再增加,全株氮生产力则显著下降。与全株氮生产力的变化不同,落叶松幼苗的叶氮生产力与供氮水平呈负相关。

Larch (Larix gmelinii) is the most important industrial timber species in northeastern China, and is ecological significant in boreal forest ecosystems. However, the growth of larch is often limited by nitrogen (N) availability because of slow litter decomposition rates due to low temperatures and the long winter in these northern forests. To explore the relationship between growth and soil N availability in larch, we treated one-year old larch seedlings to four different N supply levels (1, 4, 8 and 16 mmol·L -1, respectively) and measured acquisition and allocation of carbon and N. The results showed that the biomass, whole plant N concentration, whole plant N content and special N absorption rate of larch seedlings were enhanced with N supply levels. With the increase in N supply, needle and stem weight ratios and needle and stem N weight ratios increased, whereas the root weight ratio and root N weight ratio decreased. As N supply levels increased from 1 mmol·L -1 to 8 mmol·L -1, whole plant relative growth rate (RGR) increased linearly, whereas whole plant N productivity (NP_P) remained constant. At the highest N treatment (16 mmol·L -1), whole plant RGR was the same as in the 8 mmol·L -1 N treatment, but NP_P decreased significantly compared with the 8 mmol·L -1 treatment. In contrast, needle N productivity of larch seedlings exhibited a negative relationship with N supply level.