中文摘要：

黄土丘陵沟壑区由于土壤侵蚀严重,天然植被恢复缓慢,植被稀疏,枯枝落叶层的生态效应就显得尤为重要。对该区坡沟不同立地条件下草本群落主要物种的枯落物蓄积量、持水与养分潜在归还能力进行了分析,探讨主要物种枯落物对土壤的改善作用。结果表明：1）坡沟不同立地条件下枯落物蓄积量差异显著（P〈0.05）,在73.74—175.26 g/m2之间变化,表现为阴沟坡〉峁顶〉阳沟坡〉阴梁峁坡〉阳梁峁坡;在坡面不同微地形下也差异显著（P〈0.05）,在阳坡表现为株丛〉浅沟〉鱼鳞坑〉裸地,在阴坡为浅沟〉鱼鳞坑〉株丛〉裸地,在峁顶为株丛〉裸地。2）主要物种枯落物最大持水量可达自身干重的1.22—4.34倍;不同物种枯落物间的持水能力差异极显著（P〈0.01）,表现为白羊草叶〉铁杆蒿叶〉白羊草茎〉达乌里胡枝子叶〉长芒草〉达乌里胡枝子枝〉铁杆蒿枝。3）枯落物C、N含量分别在7.35%—40.33%和0.61%—1.60%之间,不同物种间差异极显著（P〈0.01）,同一物种枯落物C、N含量在坡沟不同立地条件下差异不显著。4）影响枯落物分解的木质素含量（1.00%—8.20%）、纤维素含量（3.16%—14.06%）、木质素/N值（0.78—12.48）、C/N值（5.61—57.41）在不同物种间差异极显著（P〈0.01）;同一物种木质素含量、纤维素含量和木质素/N值在坡沟不同立地条件下差异显著（P〈0.05）,而C/N值不显著。5）铁杆蒿叶的枯落物养分潜在归还能力最大,达乌里胡枝子和白羊草的枯落物次之,长芒草的枯落物养分潜在归还能力最小。

英文摘要：

Because of the serious soil erosion, the soil moisture and nutrients deficiency, the slowly recovery and scarcity of natural vegetation in the hill-gully Loess Plateau, the ecological effects of litter layer are particularly important for litter layer effective reduction on surface runoff and mitigate soil erosion. Thus, in this study, the litter accumulation ofcommunities and main her holding capacity of litter of litter of main herb species main species litter on soil fertility improvement was discussed. It＇s important to understand the mechanism and efficacy of the resistance of plants to soil erosion. The main results were as follows： 1 ） the accumulation of community litter wasbetween 73.74-175.26 g,/m2, and was significantly different in slope-gully sites （P〈0. 05） , ordered as shady gully slope 〉 hilltop 〉 sunny gully slope 〉 shady hilly slope 〉 sunny hilly slope. While in micro-sites ordered as under vegetation 〉 ephemeral gully 〉 fish-scale pit 〉 bare land on the sunny slope, ephemeral gully 〉 fish-scale pit 〉 under vegetation 〉 bareland on the shady slope and under vegetation 〉 bare land on the hilltop. 2） The maximal water holding capacity of litter of main species was up to 1.22-4.34 times of its dry mass, and it was extremely significantly different among species （P〈 0. 01 ）, ordered as the defoliation of Bothriochloa ischaemun 〉 the defoliation of Artemisia gmelinii 〉 the deadwood ofBothriochloa ischaemun 〉 the defoliation of Lespedeza davurica 〉 the litter of Stipa bungeanaon 〉 the deadwood of Lespedeza davurica 〉 the deadwood of Artemisia gmelinii. 3 ） The organic carbon content （7.35%--40.33%） and total nitrogen content （0.61%--1.60%） of species were extremely significant different among species （P〈0. 01）, but they were notsignificantly different in slope-gully sites. 4 ） Indicators that influenced litter decomposition （such as lignin content, cellulose content, lignin/N ratio, C/N ratio） were extremely significant differ