关键词: 长白落叶松(Larix olgensis), 树干液流密度, 时滞效应, 树木特征, 坡位

Abstract: To clarify the role of tree characteristics and slope positions in the time lag between tree stem sap flux density (J_s) and solar radiation (R_s). Plants of different diameter classes in a Larix olgensis near-mature forest (31 years old) in the hilly area of the Sanjiang Plain were used. The relationships between the time lag J_s-R_s and tree characteristics, adjacent tree characteristics and slope positions were evaluated. Though both J_s and R_s exhibited diurnal variation, they were not synchronized, thus leading to a time lag between J_s and R_s. During the growing season, the change in J_s lagged behind the change in R_s by 21.1 ± 6.9 min. Compared with tree height and crown width, the time lag J_s-R_s was more dependent on diameter at breast height (DBH). The time lag between J_s and R_s showed a linear increase with DBH. Compared with the characteristics of neighboring trees, the time lags J_s-R_s were more dependent on their own tree characteristics. A significant relationship was not observed between the time lag J_s-R_s and soil volumetric water content. The effects of tree characteristics, adjacent tree characteristics and slope positions on the formation of the time lag J_s-R_s were compared. The time lag of J_s on R_s was mainly controlled by the tree characteristics (DBH). DBH is an important factor that affects the time lag between J_s and R_s under sunny conditions during the growing season of L. olgensis.

Key words: Larix olgensis, stem sap flux density, time lag effect, tree characteristics, slope position