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首页> 外文期刊>Plant and Soil >The effect of the presence of a forage legume on nitrogen and carbonlevels in soils under Brachiaria pastures in the Atlantic forest region ofthe South of Bahia, Brazil
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The effect of the presence of a forage legume on nitrogen and carbonlevels in soils under Brachiaria pastures in the Atlantic forest region ofthe South of Bahia, Brazil

机译：在巴西巴伊亚州以南的大西洋森林地区，腕果草下的牧草对土壤中氮和碳水平的影响

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The impact of forest clearance, and its replacement by Brachiaria pastures, on soil carbon reserves has been studied at many sites in the Brazilian Amazonia, but to date there appear to be no reports of similar studies undertaken in the Atlantic forest region of Brazil. In this study performed in the extreme south of Bahia, the changes in C and N content of the soil were evaluated from the time of establishment of grass-only B. humidicola and mixed B. humidicola/Desmodium ovalifolium pastures through 9 years of grazing in comparison with the C and N contents of the adjacent secondary forest. The decline in the content of soil C derived from the forest (C3) vegetation and the accumulation of that derived from the Brachiaria (C4) were followed by determining the C-13 natural abundance of the soil organic matter (SOM). The pastures were established in 1987, 10 years after deforestation, and it was estimated that until 1994 there was a loss in forest-derived C in the top 30 cm of soil of approximately 20% (9.1 Mg C ha(-1)). After the establishment of the pastures, C derived from Brachiaria accumulated steadily such that at the final sampling (1997) it was estimated 13.9 Mg ha(-1) was derived from this source under the grass-only pasture (0-30 cm). Samples taken from all pastures and the forest in 1997 to a depth of 100 cm showed that below 40 cm depth there was no significant contribution of the Brachiaria-derived C and that total C reserves under the grass/legume and the grass-only pastures were slightly higher than under the forest (not significant at P=0.05). The more detailed sampling under the pastures showed that to a depth of 30 cm there was significantly (P <0.05) more C under the mixed pasture than the grass-only pasture. It was estimated that from the time of establishment the apparent rate of C accumulation (0-100 cm depth) under the grass/legume pastures (1.17 Mg ha(-1) yr(-1)) was almost double that under the grass-only pastures (0.66 Mg ha(-1) yr(-1)). The data indicated that newly incorporated SOM derived from the Brachiaria had a considerably higher C:N ratio than that present under the forest.
机译：在巴西亚马孙地区的许多地方，都研究了森林砍伐及其被腕足草替代的土壤碳储量的影响，但迄今为止，似乎没有关于巴西大西洋森林地区进行过类似研究的报道。在巴伊亚州最南端进行的这项研究中，评估了土壤的碳和氮含量的变化，从建立纯草B.湿地牛草和混合的B.湿地牛草/椭圆形复叶草到建立9年的放牧期开始。与相邻次生林的碳和氮含量进行比较。通过测定森林有机物（SOM）的C-13天然丰度，来追踪森林（C3）植被衍生的土壤C含量的下降以及腕带（C4）衍生的土壤C的积累。牧场始建于1987年，即森林砍伐后的10年，据估计，直到1994年，表层30 cm土层中的森林衍生碳损失约20％（9.1 Mg C ha（-1））。牧场建立后，源自腕带的C不断积累，以至于在最终采样（1997年）中，仅草牧场（0-30 cm）下估计从该来源中提取了13.9 Mg ha（-1）。在1997年从所有牧场和森林中采集的100厘米深度的样本显示，在40厘米以下的深度中，腕带来源的C没有显着贡献，草/豆类和仅草场下的总C储量为略高于森林（在P = 0.05时不显着）。在牧场下进行的更详细的采样显示，在30 cm的深度下，混合牧场下的碳含量比仅草场下的要高得多（P <0.05）。据估计，从建立之时起，草/豆类草场（1.17 Mg ha（-1）yr（-1））下的C累积表观速率（0-100 cm深度）几乎是草下的C累积速率的两倍-仅草场（0.66 Mg ha（-1）yr（-1））。数据表明，从腕带中获得的新结合的SOM的C：N比明显高于森林中存在的C：N。

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