林龄对人工促进天然更新林林下层生源要素的影响

Forest Age Effects on Biogenic Elements of Understory Layer in Assisted Naturally Regenerated Forest

人工促进天然更新林是一种有机碳维持较高、养分归还较快的森林类型。本研究选择林龄为21、31和49年的人工促进天然更新林为对象,探讨林龄对人工促进天然更新林林下植被和凋落物层碳、氮、磷、钾等生源要素含量及各元素的化学计量关系的影响,并试图建立林下植被和枯落物层营养元素之间的联系。研究结果为:31年生人工促进天然更新林林下植被磷含量及枯落物氮、磷、钾含量显著高于21年生和49年生;31年生林下植被和枯落物碳磷比、枯落物氮磷比显著高于21年生和49年生;林下植被和枯落物的碳、氮、磷、钾含量之间存在显著的正相关关系。结果表明林下植被对土壤养分归还具有重要影响,因而强调要加强人工促进天然更新林林下植被的保护和管理,减少林下植被的卫生伐。

Assisted naturally regenerated forest is characterized by high carbon sequestration and fast nutrients cycling.But as a key component of carbon and nutrients storage pool,the carbon,nutrients concentration,their stoichiometry,and their responses to forest age in understory vegetation and litter layer in the forest remain largely unknown.This study tried to explore forest age effects on carbon,nitrogen,phosphorus,potassium,and their stoichiometry with a chronosequence of the forest with ages of 21-,31-,and 49-year-old.Besides,we attempted to examine the possible linkages between understory vegetation and litter layer in terms of carbon,nutrients content,and their stoichiometry.The results showed that,(1)phosphorus concentration in understory vegetation and nitrogen,phosphorus,and potassium concentration in litter were higher in 31-year-old assisted naturally regenerated forest than those in 21-,and 49-year-old;(2)C∶P in understory vegetation and litter and N∶P in litter were higher in 31-year-old assisted naturally regenerated forest than those in 21-,and 49-year-old;(3)the carbon,nitrogen,phosphorus,and potassium concentration in understory vegetation and litter were positively correlated.Understory vegetation played an important role in nutrient cycling back to soil,thus highlight the significance of understory vegetation protection and management via reducing sanitation slashing in the forest.