杨树人工林细根数量和形态特征的季节动态及代际差异

采集欧美杨107Ⅰ代和Ⅱ代人工林细根样品，分析杨树不同根序细根数量特征(根长度、表面积和生物量)和形态特征(比根长、根长密度、根组织密度)对季节波动的响应及其代际差异.结果表明： 杨树各根序细根数量特征(根长度、表面积和生物量)均呈明显的季节变化，且具有明显的根序差异性.低级根序细根数量特征季节差异显著，细根生物量在生长季显著增加而生长季后显著下降.高级根序细根比根长季节波动显著，而根长密度和根组织密度等形态特征波动较小.连作导致人工林杨树1～2级细根长度、生物量、比根长和根长密度在生长季显著增大.1级细根数量特征与土壤温湿度呈显著正相关，与土壤有机质和速效氮含量呈显著负相关；而2级细根数量特征仅与土壤养分显著相关.杨树人工林细根特征的季节动态及代际差异体现了杨树对细根的碳投入变化，因连作引发的土壤养分匮乏可能引发植株对根系的碳投入增加，这种碳分配格局与人工林地上部分生产力形成密切相关.

Seasonal dynamics of quantitative and morphological traits of poplar fine roots and their differences between successive rotation plantations.

Based on the fine root samples of the first and second generations of poplar (Populus ×euramericana ‘Neva’), this study examined the response of quantitative and morphological traits of fine roots of different orders and the difference between generations. The results showed that, the quantitative traits of fine roots, such as root length, root surface area and root biomass, presented obvious seasonal variation, and the fine root traits had obvious difference among root orders. The quantitative traits of lower order fine roots showed significant seasonal difference, and the fine root biomass increased in the growing season and then decreased significantly. The specific root length (SRL) of higher order roots also showed significant change with season, while the root length density (RLD) and root tissue density (RTD) changed a little. The successive rotation resulted in the significant increase of root length, root biomass, SRL and RLD of 1-2 orders in the growing season. The quantitative traits of first order root significantly positively correlated with soil temperature and moisture, and significantly negatively correlated with the soil organic matter and soil available nitrogen content. However, the quantitative traits of second order root only showed significant correlation with soil nutrient content. The seasonal dynamics of poplar fine roots and the difference between successive rotation plantations implied carbon investment change of poplar to roots. Soil nutrient deficiency induced more carbon investment into roots, and this carbon allocation pattern might affect the aboveground productivity of poplar plantation.