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Biogeochemical consequences of the transformation of native Cerrado into Pinus caribaea plantations in Brazil

机译:巴西原生Cerrado向Pinus caribaea人工林转化的生物地球化学后果

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Under the same climatic and edaphic conditions, native savanna vegetation in Brazil, the Cerrado, shows a lower stature and canopy cover than planted Pinus caribaea Morelet forests. To assess the differences in biogeochemical element cycling we compared the nutrient economy of Cerrado and Pinus on three replicate plots of each forest type. The mean nutrient storage in the soil organic layer under Pinus (N: 2630; P: 141; K: 103; Ca: 131; Mg: 20 kg ha−1) was substantially higher than under Cerrado (N: 23; P: 1.2; K: 0.83; Ca: 5.8; Mg: 1.0 kg ha−1) probably because the Pinus roots explored a larger soil volume. The Pinus trees had a higher nutrient-use efficiency as indicated by higher mean litter mass per unit nutrient in litter (N: 108; P: 2290; K: 729; Ca: 1360; Mg: 5420; S: 1190; Fe: 2960; Mn: 9990, Zn: 145000) than the Cerrado trees (N: 94; P: 1810; K: 619; Ca: 302; Mg: 938, S: 746; Fe: 1800; Mn: 7880; Zn: 63700). Mean annual small litterfall collected in 0.25-m2 samplers between May 1997 and April 1999 was 2.1 Mg ha−1 in Cerrado and 7.8 in Pinus. The litterfall rates of the 1–3 week collection intervals correlated negatively with the soil matric potential indicating that litterfall was partly related to water stress. The fluxes of N (73 kg ha−1 year−1), P (3.7), K (11), S (7.0), and Mn (0.83) to the soil with litterfall under Pinus were greater than the litterfall+turnover of the grass/herbs layer under Cerrado (N: 39, P: 2.8, K: 8.6, S: 5.4, Mn: 0.79 kg ha−1 year−1), those of Zn (0.06–0.07) were similar, and those of Ca (Pinus: 5.9/Cerrado: 10), Mg (1.5/4.4), and Fe (2.9/4.0) were smaller. Mean residence times of the organic matter and of all elements were longer in the soil organic layer under Pinus (3.7–26 years in the Oi horizon, 8.1–907 years in the whole organic layer) than under Cerrado (0.22–3.6 years in the Oi horizon, the only organic horizon under Cerrado). Our results demonstrate that the main differences in biogeochemical element cycling between the Pinus forest and the Cerrado consisted of a larger nutrient storage in the organic layer, a higher nutrient-use efficiency, and slower nutrient release rates from the organic layer in the Pinus forest than in the Cerrado. Nutrient cycling as assessed by the nutrient fluxes with litterfall was only partly faster in the Pinus forest than in the Cerrado.
机译:在相同的气候和海底条件下,巴西本地的热带稀树草原塞拉多(Cerrado)的身高和冠层覆盖率低于人工种植的加勒比松Morelet森林。为了评估生物地球化学元素循环的差异,我们在每种森林类型的三个重复样地上比较了Cerrado和Pinus的养分经济。松树下土壤有机层的平均养分储量(N:2630; P:141; K:103; Ca:131; Mg:20 kg ha-1 )大大高于塞拉多(N:23) ; P:1.2; K:0.83; Ca:5.8; Mg:1.0 kg ha-1 ),可能是因为松树的根系探索了更大的土壤体积。凋落物树具有更高的养分利用效率,表现为凋落物中每单位养分的平均凋落物质量更高(N:108; P:2290; K:729; Ca:1360; Mg:5420; S:1190; Fe:2960 ; Mn:9990,Zn:145000)比Cerrado树(N:94; P:1810; K:619; Ca:302; Mg:938,S:746; Fe:1800; Mn:7880; Zn:63700) 。在1997年5月至1999年4月期间,在0.25-m2 采样器中收集的年平均小凋落物在Cerrado为2.1 Mg ha-1 ,在Pinus为7.8。 1-3周收集间隔的凋落物速率与土壤基质潜力呈负相关,表明凋落物与水分胁迫部分相关。松树下凋落物对土壤的氮通量(73 kg ha-1 year-1 ),磷(3.7),钾(11),硫(7.0)和锰(0.83)大于塞拉多(Cerrado)下草/草层的凋落物+周转量(N:39,P:2.8,K:8.6,S:5.4,Mn:0.79 kg ha-1 year-1 ),锌的含量(0.06-0.07)相似,而钙的含量(Pinus:5.9 /塞拉多:10),Mg(1.5 / 4.4)和Fe(2.9 / 4.0)较小。有机物和所有元素的平均停留时间在松树下的土壤有机层中(在Oi地平线上为3.7-26年,在整个有机层中为8.1-907年)比塞拉多下的(0.22-3.6年)长。 Oi地平线,塞拉多之下唯一的有机地平线)。我们的结果表明,松树森林和塞拉多森林之间的生物地球化学元素循环的主要差异在于,松树森林中有机层的养分存储量更大,养分利用效率更高,而养分从有机层的释放速度较慢在塞拉多。用凋落物的养分通量估算的养分循环在松林中仅比塞拉多快。

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