黄土丘陵区典型植被枯落物坡面分布及混入土壤对土壤性状的影响

黄土丘陵区植被的恢复可能影响枯落物分布特征,进而对土壤性状产生影响。论文选取刺槐（Robinia pseudoacacia）人工林、柠条（Caragana intermedia）人工林、铁杆蒿（Artemisia gmelini）群落和白羊草（Bothriochloa ischaemum）群落4种典型植被样地,研究其枯落物坡面（坡长40~80 m）分布特征及自然条件混入土壤中对土壤理化性状的影响。结果表明：1）4种典型植被样地地表枯落物蓄积量（143.89~833.04 g/m²）、盖度（0.36~0.63）和厚度（0.77~2.03 cm）均表现为刺槐人工林>柠条人工林>铁杆蒿群落>白羊草群落;土壤中枯落物混入量（178.80~657.21 g/m²）和混入深度（1.33~2.29 cm）均表现为刺槐人工林>铁杆蒿群落>柠条人工林>白羊草群落;土壤中枯落物混入量占枯落物总蓄积量的比例（45.91%~74.02%）表现为铁杆蒿群落>柠条人工林>白羊草群落>刺槐人工林。2）4种典型植被样地地表枯落物蓄积量和土壤中枯落物混入量均为坡下高于坡上,受径流冲刷和泥沙分离—输移—沉积过程的影响,枯落物地表蓄积量和土壤混入量在坡中波动较大;随枯落物地表盖度的增加,地表枯落物蓄积量呈指数函数增加（P<0.01）,且随地表枯落物蓄积量的增加,土壤中枯落物混入量呈对数函数增加（P<0.01）。3）土壤容重、粘结力和水稳性团聚体几何平均直径（WAS-GMD）随土壤中枯落物混入量的增大而线性降低（P<0.01）,土壤有机碳和全氮含量在铁杆蒿群落和白羊草群落中均随土壤中枯落物混入量的增大而线性增加（P<0.05）。该研究将为评价黄土高原退耕还林还（草）工程生态成效、修正土壤侵蚀预报模型提供重要依据。

Distribution of Plant Litter on the Slope and Its Effect of Litter Incorporated in the Soil on Soil Properties in Typical Vegetation Community in Loess Hilly Region

The plant litter incorporate in soil generally has great effect on soil properties. During the process of vegetation restoration in the hilly region of the Loess Plateau, the distribution of plant litter would be changed and hence affect the soil property. Four typical vegetation communities, Robinia pseudoacacia plantation, Caragana intermedia plantation, Artemisia gmelinii community and Bothriochloa ischaemum community were selected to study the distribution of litter on the slope (ranged from 40 to 80 m) and to discuss the effects of plant litter incorporated in soil on soil properties. The results showed that: 1) The volume (range from 143.89 to 833.04 g/m²), coverage (range from 36% to 63%) and thickness (range from 0.77 to 2.03 cm) of aboveground litter in Robinia pseudoacacia plantation were the highest, followed by those in Caragana intermedia plantation, Artemisia gmelinii community and Bothriochloa ischaemum community. For the biomass of incorporated litter (ranged from 178.80 to 657.21 g/m²) and the litter incorporation depth (ranged from 1.33 to 2.29 cm), the maximum values were found in Robinia pseudoacacia plantation, then followed by those in Artemisia gmelinii community, Caragana intermedia plantation and Bothriochloa ischaemum community. The amount of litter incorporated in soil accounts for the highest proportion of the total volume of litter (ranged from 45.91% to 74.02%). The vegetation communities with the ratio of the amount of litter incorporated in soil to total litter volume in descending order were Artemisia gmelinii plantation, Caragana intermedia plantation, Bothriochloa ischaemum community, and Robinia pseudoacacia community. 2) The aboveground litter volume and the amount of litter incorporated in soil on lower slopes were 1.05-2.48 times and 1.04-1.41 times higher than those on higher slope. While for the middle slope, the aboveground litter volume and the amount of litter incorporated in soil varied greatly and no significant relationship was found between middle slope and upper slope or lower slope due to the influence of runoff scouring and the process of sediment detachment, transport and deposition. The aboveground litter volume increased exponentially with the increase of litter coverage (P<0.01). The amount of litter incorporated in soil increased with the aboveground litter volume, and the relationship between them is a logarithm function (P<0.01). 3) With the increasing of litter incorporated in soil, soil properties of bulk density, cohesive force and WAS-GMD decreased linearly (P<0.01). The soil organic carbon and total nitrogen content increased linearly with the increase of litter incorporated in soil in grasslands (Artemisia gmelinii community and Bothriochloa ischaemum community), while no significant relationship was found between Robinia pseudoacacia plantation and Caragana intermedia plantation. This study would provide theoretical basis for assessing ecological effect of vegetation restoration and improving soil erosion model on the Loess Plateau.