晋北半干旱草地不同分解程度凋落物混合对分解特征的影响

Effects of mixed litter with different degrees of decomposition on the decomposition characteristics of semi-arid grassland in northern Shanxi

半干旱草地凋落物层广泛存在着不同分解程度的植物残体,为探究其混合分解对草地养分循环的影响,本研究采用野外凋落物分解袋法,对晋北半干旱草地3种乡土植物本氏针茅、艾蒿和铁杆蒿不同分解程度凋落物进行单独[新鲜凋落物(L_(Fresh))、半分解凋落物(L_(Aged))]或混合分解[新鲜凋落物与半分解凋落物1:1混合凋落物(LMix)],研究不同分解程度凋落物混合对分解特征的影响。结果表明:不同分解程度凋落物混合物的干重剩余率随分解时间增加而降低。在分解335 d后,其交互作用强度最大,具体表现为:针茅混合凋落物和铁杆蒿混合凋落物的干重剩余率实测值分别比期望值低5.12%、4.68%,表现为协同效应,而艾蒿混合凋落物表现为加和效应。此外,针茅不同分解程度凋落物混合分解可以促进N释放,抑制纤维素分解;铁杆蒿不同分解程度凋落物混合分解可以促进C释放和木质素分解。研究表明,不同分解程度凋落物混合可以改变分解速率,促进养分释放,从而对草地生态系统的养分循环产生影响。

Plant residues that are decomposed to varying degrees are widely distributed in the litter layer of semi-arid grassland.In this study,a field litter bag experiment was conducted to determine the effect of the degree of decomposition of litter at burial on the overall decomposition process.Decomposition trajectories of fresh and aged litter samples and samples made up of a mixture of fresh and aged litter from three native plant species(Stipa bungeana,Artemisia argyi,and Artemisia gmelinii)that grow in semi-arid grassland of northern Shanxi were measured.The treatments were fresh litter(L_(Fresh)),aged litter(L_(Aged)),and an equal-ratio mixture of fresh and aged litter(LMix).It was found that the mass remaining percentage of mixed litter with different degrees of decomposition decreased with the increase of decomposition time.It exhibited highest interaction when the plant litter decomposed after 335 days.The observed values of the mass remaining percentage in the S.bungeana LMix treatment and the A.gmelinii LMix treatment were 5.12%and 4.68%lower than the expected values,respectively,showing a synergistic effect,while the A.argyi LMix treatment showed an additive effect.In addition,the S.bungeana LMix treatment promoted nitrogen release and inhibited cellulose decomposition.The A.gmelinii LMix treatment promoted carbon release and lignin decomposition.In conclusion,a mixed litter comprising both fresh and aged material with different degrees of decomposition changed the decomposition rate and promoted nutrient release,thus affecting nutrient cycling in the studied grassland ecosystem.