【作者】 周朝彬；

【导师】 胡庭兴；

【作者基本信息】 四川农业大学 ， 森林培育学， 2006， 硕士

【摘要】 在林草复合系统中，土壤养分含量的多少直接影响植物生长发育，同时，植物生长吸收、植物地下根系的分布、植物凋落物的数量和质量反过来也影响土壤养分含量。试验分别设置三个模式，即巨桉+鸭茅、巨桉+高羊茅、巨桉+牛鞭草(以下分别简称为模式Ⅰ、模式Ⅱ、模式Ⅲ)，五个密度，即2222株／hm~2、1667株／hm~2、1333株／hm~2、1111株／hm~2、833株／hm~2(以下分别以Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ表示)，测定了不同林分密度下的巨桉林草复合模式种植初期养分含量及其物理性质树冠内外差异及随生长季节变化的规律。主要研究结果如下： 三个模式土壤全氮含量在整个5月至11月期间呈现出下降趋势。这可能因为各个模式中的鸭茅、高羊茅和牛鞭草均为禾本科牧草，而禾本科牧草在生长发育期间需氮量较大；其次，试验区处于华西雨屏区，年降雨量丰富，因此，淋洗损失要占氮的损失的一部分；另外，各个模式每次牧草刈割后，要带走部分氮。由于生物体在8月至11月产生的枯枝落叶和死亡根系进入土壤中的有机氮，使得土壤全氮以有机态储存起来，推测是模式Ⅰ、Ⅲ在8月至11月全氮含量回升的主要原因。 三个模式在5月至8月期间，水解氮含量均不同程度增加。因为在6、7月，温湿度较高，有机氮易矿化成分高。三个模式水解氮含量在8月至11月均为下降，可能是在这个期间，土壤温湿度不及夏季，有机氮矿化成分降低；而此时仍然保持一定长势的牧草和巨桉也需要吸收氮素。三个模式水解氮在5月至11月整个期间均呈下降趋势。 各个模式中土壤全磷含量在5月至8月期间均呈不同程度上升趋势。在8月至11月，土壤全磷含量均为下降趋势，整个期间均呈下降趋势。可能因为在这个期间，系统中巨桉和牧草仍保持生长，土壤中的全磷转化为有效磷供植物体吸收，导致了全磷的消耗。 有效磷含量在5月至11月各个模式均呈下降趋势，虽然此时较高的温湿度有利于有机磷矿化作用，但此时植物处于生长期，推测生物固定速率大于矿化速率，所以此时有效磷呈下降趋势。前面在各个模式中，土壤全磷含量整体呈下降趋势，也会影响全磷向有效磷的转化量。更多还原

【Abstract】 In the forest-grass compound planting patterns, the content of soil nutrients affects the plants’s growth. On the other hand, the absorb ability of plant, distributing of roots system, quantity and quality of litters influence the content of soil nutrients. Three patterns, the E.grandis+Dactylis glomerata L; E.grandis +Festuca arundinacea L; E.grandis +Hemarthria compressa(L..f)R.BY(the shorted form of each was pattern I , pattern II and pattern III) were set in this experiment. Each pattern has five density, namely 2222,1677,1333,1111 and 833 tree/hm~2(the shorted form of each was I , II ,HI,IV,V). The content of soil nutrients and physical properties under and out of crown of tree were measured. For the analysis of the seasonal changing role of soil nutrients and physical properties are as following:The total nitrogen content of pattern I was declined at whole stages (May to November) . The reason may be as follows: 1.Dactylis glomerata L,Festuca arundinacea L and compressa(L.f)R.BY were gramineous herbs and need large amounts of nitrogen in growing periods. 2. The experimental plot was located at the high precipitation of western China and has enough precipitation, so the increasing the nitrogen leaching loss.3. The litters and dead roots system were yielded in soil increasing the organic nitrogen between August and November. Then the total nitrogen was deposited by organic form, which may lead to the total nitrogen of model I and III increasing mainly between August and November.The content of hydrolysable nitrogen ascended between May and August, for the organic nitrogen was easily mineralized in June and July, and decreased at August to November in each patterns, may be the mineralization between August and November was lower than before, and the growths of herbs and E.grandis still need the nitrogen. In general, the hydrolysable nitrogen of all models was declined at whole stages.The content of total phosphorus ascended between May and August and decreased at August to November in each patterns, and were declined at whole stages. For the growth of E.grandis and herbs need the total phosphorus translating into available phosphorus, and was likely to lead to the total phosphorus decreased.更多还原