Purpose

Though land use change has been shown to have great influence on soil structure and C storage, little is still known how these effects change over the long term, especially in Africa. Thus, a study was conducted in central highlands of Kenya to evaluate changes in soil aggregates and aggregate-associated C content across four land use types.

Methods

The four land use types included (1) an undisturbed bush land, (2) over 50 years old grazed pasture, (3) over 80 years old coffee plantation, and (4) a maize field cultivated continuously for 3 years. It was hypothesized that soil aggregates and aggregate-associated C would decrease with increasing soil disturbance caused by tillage or exerted by livestock hooves, with the magnitude of these effects being reduced by abundance of earthworms and termites.

Results and discussions

Land use type significantly affected soil aggregates especially, large macroaggregates and microaggregates. The weight of large macroaggregates in bush land (14.4 g 100 g⁻¹ soil) was more than 20 times higher than in maize field (0.6 g 100 g⁻¹). On the contrary, the weight of microaggregates in maize field (41.2 g 100 g⁻¹) was more than double that recorded in bush land (18.8 g 100 g⁻¹). Aggregate-associated C showed magnitude of differences similar to those of soil aggregates. However, the abundance of earthworms and termites generally showed weak or no correlation with soil aggregate fractions and aggregate-associated C.

Conclusion

Our results shows that land use change can significantly influence soil aggregation and C content, which could have far-reaching implications for the long term C sequestration.

中文翻译：

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土地用途的变化，而不是土壤大型动物的变化，影响肯尼亚中部高地的土壤团聚体和与团聚体相关的碳含量

目的

尽管已显示土地利用变化对土壤结构和碳储量有很大的影响，但长期影响，尤其是在非洲，这些影响如何变化仍知之甚少。因此，在肯尼亚中部高地进行了一项研究，以评估四种土地利用类型中土壤团聚体和团聚体相关碳含量的变化。

方法

四种土地利用类型包括：（1）未受干扰的灌木丛土地；（2）拥有50年历史的牧场；（3）拥有80年历史的咖啡种植园；以及（4）连续种植3年的玉米田。假设随着耕作或牲畜蹄引起的土壤扰动的增加，土壤团聚体和与团聚体相关的碳会减少，而effects和白蚁的数量会降低这些效应的程度。

结果与讨论

土地利用类型显着影响土壤团聚体，特别是大型的大团聚体和微团聚体。灌木丛土地（14.4 g 100 g ^-1土壤）中的大型聚集体的重量比玉米田（0.6 g 100 g ^-1）高出20倍以上。相反，玉米田中的微团聚体的重量（41.2 g 100 g ^-1）是灌木林地（18.8 g 100 g ^-1）的两倍多。与团聚体相关的碳表现出的差异程度与土壤团聚体相似。然而，worm和白蚁的丰富度通常与土壤骨料含量和骨料相关碳含量无相关性。

结论

我们的结果表明，土地利用变化会显着影响土壤的团聚和碳含量，这对于长期的碳固存可能具有深远的影响。