Biological survey of a low-productivity pasture in Rondonia state, Brazil
Biological survey of a low-productivity pasture in Rondonia state, Brazil
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DOI：
10.5367/000000006778536738
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发表时间：
2006-09-01
影响因子：
3
通讯作者：
Melo, Lineu
中科院分区：
文献类型：
--
作者：
Feigl, Brigitte;Cerri, Carlos;Melo, Lineu
在巴西亚马逊地区，在建立这些牧场几年后，种植臂形草和其他非洲草的牧场面积显示出饲料和动物生产力的持续下降。如果不采取补救措施，植被就会减少，杂草会侵入这些地区，土壤会变得紧实。然而，这一过程尚未得到很好的理解。在一个20岁的牧场位于一个有代表性的牛牧场在朗多尼亚州进行了一系列的评估，估计植物组成，常设植物量（包括落叶），大型动物物种丰富度和微生物生物量的特点牧场网站即将退化的土壤生物条件和恢复措施之前，通过。其目的是确定已经完成的退化类型和程度，以记录可与恢复做法取得的结果进行比较的基线。土壤C、N和有效P储量分别为20.4 Mg C ha（-1）、1.5 Mg N ha（-1）和8.3 kg P ha（-1），高于天然林，接近生产性牧场。物理和化学分析未显示有效降解。以树木和灌木为主的木本物种，如Tabebuia spp.，钩状艾瑞斯马和圭亚那槲寄生占总面积的15-18%。巴巴库棕榈（Orbignya phalerata Mart）占12%，草本杂草占4- 11%，而其余（平均63.5%）含有Brachiaria brizantha和Pannicum maximum的混合物。高生物量的增加和物种的多样性表明，土壤仍然能够支持一个生产性的饲料草覆盖。地上生物量，包括凋落物层，总计131毫克DM公顷（-1），或原始森林的42%。在实验区的高常设生物量可以归因于不充分和/或不适当的杂草控制，因为早期阶段的牧场安装。研究地点的改造将意味着大约130 Mg C ha（-1）（C/N = 49; C/P = 744）的潜在地上输入，此外还有6.4 Mg C ha（-1）来自根系生物量分解。最常见的无脊椎动物是白蚁（368 ind m（-2）），仅限于0-10厘米层，而蚯蚓（204 ind m（-2））、蚂蚁（152 ind m（-2））和鞘翅目（146 ind m（-2））的深度为30厘米。所谓的生态系统工程师的存在表明，这个人口，可能包括anecics和食根物种，是与高根和凋落物密度。代表的平均数是更可比的网站经历再生的次生植被比退化的牧场。微生物学证据表明，研究的牧场构成了一个非胁迫系统，在土壤中积累有机质。
Some years after their establishment, areas of pasture planted to Brachiaria and other African grasses in the Brazilian Amazon region show a continuous decline in forage and animal productivity. If no remedial measures are taken, plant cover decreases, the areas become invaded by weeds and the soil becomes compacted. However, this process is not yet well understood. A series of evaluations was implemented in a 20-year-old pasture located on a representative cattle ranch in Rondonia state to estimate the botanical composition, standing phytomass (including leaf litter), macrofauna species richness and microbial biomass to characterize the soil biological conditions of a pasture site about to degrade and before rehabilitation practices were adopted. The aim was to characterize the type and degree of degradation already completed to record the baseline against which the results obtained by restoration practices could be compared. Soil C, N and available P stocks were 20.4 Mg C ha(-1), 1.5 Mg N ha(-1) and 8.3 kg P ha(-1) respectively, higher than under natural forest and close to those found in productive pasture sites. Physical and chemical analyses did not indicate effective degradation. Woody species dominated by trees and shrubs such as Tabebuia spp., Erisma uncinatum and Vismia guianensis occupied 15-18% of the total area. Babacu palm (Orbignya phalerata Mart) covered 12%, herbaceous weeds 4-11%, while the rest (mean 63.5%) contained a mixture of Brachiaria brizantha and Pannicum maximum. The high biomass accrual and the diversity of species suggest that the soil is still able to support a productive forage grass cover. Biomass above ground, including litter layer, totalled 131 Mg DM ha(-1), or 42% of original forest. High standing biomass in the experimental area can be attributed to insufficient and/or inapropriate weed control since the early stage of pasture installation. Reformation of the study site would implicate a potential above-ground input of about 130 Mg C ha(-1) (C/N = 49; C/P = 744), besides another 6.4 Mg C ha(-1) derived from root biomass decomposition. The most frequently found invertebrates were the termites (368 ind m(-2)), restricted to the 0-10 cm layer, while earthworms (204 ind m(-2)), ants (152 ind m(-2)) and Coleoptera (146 ind m(-2)) were found to a depth of 30 cm. The presence of so-called ecosystem engineers indicates that this population, probably comprising anecics and rhizophagous species, is related to the high root and litter density. The average number of representatives is more comparable with sites undergoing regrowth of secondary vegetation than with degraded pastures. Microbiological evidence indicates that the pasture studied constitutes an unstressed system about to accumulate organic matter in the soil.