Dynamics of topsoil carbon and nitrogen along a tropical forest–cropland chronosequence: Evidence from stable isotope analysis and spectroscopy

Awiti, Alex; Walsh, Markus; Kinyamario, JI

doi:10.1016/j.agee.2008.04.012

Cited by 56 publications

(29 citation statements)

References 41 publications

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“…Thus, cultivated soils almost always appear degraded in comparison. Most of the studies were located in the same region using Kenya's Kakamega and Nandi forests as the baseline and measured soil properties in continuous maize farms cleared between 50 and 100 years ago [94,98,102,103,106,108]. Similar to the longitudinal studies, chronosequences tended to show non-linear declines in topsoil properties with time since forest conversion to agriculture.…”

Section: Chronosequences (Space-for-time)mentioning

confidence: 76%

“…Similar to the longitudinal studies, chronosequences tended to show non-linear declines in topsoil properties with time since forest conversion to agriculture. Soil infiltrability [93], SOM [93,102,106], Soil P [103], pH [102,107], and total C and N [107,108] all showed marked declines in cultivated compared to forested baselines.…”

Section: Chronosequences (Space-for-time)mentioning

confidence: 99%

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The State of Soil Degradation in Sub-Saharan Africa: Baselines, Trajectories, and Solutions

et al. 2015

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Abstract:The primary cause of soil degradation in sub-Saharan Africa (SSA) is expansion and intensification of agriculture in efforts to feed its growing population. Effective solutions will support resilient systems, and must cut across agricultural, environmental, and socioeconomic objectives. While many studies compare and contrast the effects of different management practices on soil properties, soil degradation can only be evaluated within a specific temporal and spatial context using multiple indicators. The extent and rate of soil degradation in SSA is still under debate as there are no reliable data, just gross estimates. Nevertheless, certain soils are losing their ability to provide food and essential ecosystem services, and we know that soil fertility depletion is the primary cause. We synthesize data from studies that examined degradation in SSA at broad spatial and temporal scales and quantified multiple soil degradation indicators, and we found clear indications of degradation across multiple indicators. However, different indicators have different trajectories-pH and cation exchange capacity tend to decline linearly, and soil organic carbon and yields non-linearly. Future research should focus on how soil degradation in SSA leads to changes in ecosystem services, and how to manage these soils now and in the future. OPEN ACCESS

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Section: Chronosequences (Space-for-time)mentioning

confidence: 76%

Section: Chronosequences (Space-for-time)mentioning

confidence: 99%

The State of Soil Degradation in Sub-Saharan Africa: Baselines, Trajectories, and Solutions

et al. 2015

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“…time for space substitution) (Walker et al, 2010), are commonly used to describe and study changes in soils and soil degradation (Kimetu et al, 2008;Lemenih et al, 2005a, b;Awiti et al, 2008). Losses of 50 % to 80 % in soil C and N have been reported from sites that have been under agriculture for 20-50 yr (Solomon et al, 2007;Lemenih et al, 2005 a, b).…”

Section: G Nyberg Et Al: Soil Property Changes In a 120 Yr Forestmentioning

confidence: 99%

Soil property changes over a 120-yr chronosequence from forest to agriculture in western Kenya

Nyberg

Bargués‐Tobella²,

Kinyangi

et al. 2012

Hydrol. Earth Syst. Sci.

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Abstract. Much of the native forest in the highlands of western Kenya has been converted to agricultural land in order to feed the growing population, and more land is being cleared. In tropical Africa, this land use change results in progressive soil degradation, as the period of cultivation increases. Both rates and variation in infiltration, soil carbon concentration and other soil parameters are influenced by management within agricultural systems, but they have rarely been well documented in East Africa. We constructed a chronosequence for an area of western Kenya, using two native forest sites and six fields that had been converted to agriculture for up to 119 yr.We assessed changes in infiltrability (the steady-state infiltration rate), bulk density, proportion of macro-and microaggregates in soil, soil C and N concentrations, as well as the isotopic signature of soil C (δ 13 C), along the 119-yr chronosequence of conversion from natural forest to agriculture. Infiltration, soil C and N decreased within 40 yr after conversion, while bulk density increased. Median infiltration rates fell to about 15 % of the initial values in the forest, and C and N concentrations dropped to around 60 %, whilst the bulk density increased by 50 %. Despite high spatial variability, these parameters have correlated well with time since conversion and with each other.

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“…In addition, the larger plant litter input and root turnover in forests compared to cropped fields maintain greater soil organic carbon (SOC) concentrations, which in turn preserves soil structure and promotes higher infiltration capacities, lower Hortonian overland flow, and greater water storage capacity (Fritsch 1993). With continued cultivation over a period of years, particularly in low-input and subsistence systems, soils begin to lose SOC and become compacted, which has profound effects on soil hydrology (Giertz and Diekkruger 2003;Awiti et al 2008). Particularly in the tropics, SOC losses can be rapid (Solomon et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Stream Discharge in Tropical Headwater Catchments as a Result of Forest Clearing and Soil Degradation

et al. 2012

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Tropical Africa is affected by intense land-use change, particularly forest conversion to agricultural land. In this study, the stream discharge of four small headwater catchments located within an area of 6 km 2 in western Kenya was examined for 2 years (2007 and 2008). The four catchments cover a degradation gradient ranging from intact forest to agricultural land under maize cultivation for 5, 10, and 50 years. The runoff ratio (e.g., annual catchment discharge expressed as a percentage of rainfall) increased with increasing duration of cultivation from an average of 16.0% in the forest to 32.4% in the 50-yr-old agricultural catchment. Similarly, the average runoff ratio due to the stormflow component was 0.033 in the forest and increased gradually to 0.095 with increasing duration of cultivation. The conversion from forest to agricultural land in the first 5 years caused about half of the total observed increases in runoff ratio (46.3%) and discharge in relation to rainfall (50.6%). The other half of the changes in discharge occurred later during soil degradation after forest clearing. With increasing duration of cultivation, soil bulk density r b at a depth of 0-0.1 m increased by 46%, while soil organic carbon (SOC) concentrations and total porosity decreased by 75% and 20%, respectively. The changes in hydrological responses that occurred in the initial years after forest clearing may suggest a significant potential for improved land management in alleviating runoff and enhanced storm flow and moisture retention in agricultural watersheds.

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Dynamics of topsoil carbon and nitrogen along a tropical forest–cropland chronosequence: Evidence from stable isotope analysis and spectroscopy

Cited by 56 publications

References 41 publications

The State of Soil Degradation in Sub-Saharan Africa: Baselines, Trajectories, and Solutions

The State of Soil Degradation in Sub-Saharan Africa: Baselines, Trajectories, and Solutions

Soil property changes over a 120-yr chronosequence from forest to agriculture in western Kenya

Stream Discharge in Tropical Headwater Catchments as a Result of Forest Clearing and Soil Degradation

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