土壤水分与养分对树木细根生物量及生产力的影响

Influence of water and soil nutrients on biomass and productivity of fine tree roots: a review

树木细根是吸收水分和养分的重要器官,它的生长、死亡、分解在森林生态系统养分循环中起着重要作用。根系对水分和养分的吸收密切复杂地联系在一起,土壤水分和养分有效性对细根生长与发育影响不同,但细根生长的季节动态与土壤水分的季节动态分布规律一致,增加土壤水分显著增加细根生物量;而增加土壤养分对细根生长变化的影响较复杂,多数研究结果认为随土壤养分的增加,细根生物量增加或减少,低级根的根长和直径普遍增大,比根长减小。水肥耦合处理下的细根生物量显著大于灌溉和施肥处理下的细根生物量,并具有明显的季节规律性;水肥耦合会使细根根长密度增大;细根寿命暂时性缩短或延长等。在分析了不同树种在不同立地条件下细根生长规律及变化原因后,依据研究现状提出将来水肥耦合处理条件下树木根细的研究方向。

Fine tree roots are important organs that absorb water and nutrients from the soil; their growth, death, and decomposition processes play a major role in forest ecosystem recycling. Root absorption of one factor （water or nutrients） can influence the other, and soil moisture and nutrient availability can affect fine root growth and development. Seasonal dynamics of fine root growth coincide with seasonal dynamics of soil moisture distribution. When soil moisture increases, fine root biomass also increases. Nevertheless, the effect of soil nutrients on fine root growth is complicated; for example, an increase in nutrients can produce： a） an increase or decrease in fine root biomass, b） generally an increase in root length and diameter of the lower root, and c） a decrease in specific root length. Repeated applications of water and fertilizer greatly improved fine root biomass with notable seasonal changes, such as an increase in length density of fine roots and fine root longevity more short or long temporarily. After considering growth laws and reasons for changes in fine roots for different species and different site conditions, we suggest that future research with fine roots should focus on the combined effects of water and nutrients.