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Modelling and Mapping Erosion in Smallholder Agro-Ecosystems, Tanzania
Land Degradation & Development ( IF 4.7 ) Pub Date : 2018-07-11 , DOI: 10.1002/ldr.3073
Juma Wickama 1 , Aad Kessler 2 , Geert Sterk 3
Affiliation  

The West Usambara Highlands in north-eastern Tanzania have many smallholder agro-ecosystems with unknown composition, management, and vulnerability to erosion. Their specific locations and spatial extent are difficult to trace by satellite images or remote sensing imagery alone. To address these limitations, we combined ground soil surveys, geographic information system, and erosion modelling to (a) locate and map smallholder agro-ecosystems, (b) determine their biophysical characteristics, and (c) model their soil losses. Land resource information was collected from 301 random 0.1-ha plots sampled from a total area of 200 km2. Annual soil losses were estimated using the universal soil loss equation. The study located six dominant agro-ecosystems with the following spatial extent: maize-bean (24.9%), maize-bean-agroforestry (31.2%), maize-bean-agroforestry-high value trees (18.9%), tree farms (7.0%), forests (15.6%), and grazing lands (2.3%). Agroforestry and other tree-based agro-ecosystems dominate the area due to historical land use change and later institutional interventions. This study finds combined use of soil surveys, geographic information system, and modelling to be reliable in locating, mapping, and assessing soil losses in smallholder agro-ecosystems. The agro-ecosystems differ significantly (p < 0.05) in slope, vegetation cover, soil conditions, and soil losses. Soil loss in the maize-bean agro-ecosystem (28.3 t ha−1 yr−1) was 18 times higher compared with natural forests (1.57 t ha−1 yr−1) due to lower soil cover and inefficient conservation and cultivation practices. Our results show that adoption of soil conservation measures and improved vegetation cover technologies across the agro-ecosystems reduces soil losses by 37% and increases organic carbon levels by 16%.

中文翻译:

坦桑尼亚小农农业生态系统中的侵蚀建模和绘图

坦桑尼亚东北部的西乌桑巴拉高地有许多小农农业生态系统,其组成、管理方式和易受侵蚀的脆弱性未知。它们的具体位置和空间范围很难单独通过卫星图像或遥感图像进行追踪。为了解决这些限制,我们结合了地面土壤调查、地理信息系统和侵蚀模型,以 (a) 定位和绘制小农农业生态系统的位置,(b) 确定它们的生物物理特征,以及 (c) 模拟它们的土壤流失。从总面积 200 平方公里的 301 个随机 0.1 公顷地块中收集土地资源信息。使用通用土壤流失方程估算年度土壤流失量。该研究定位了具有以下空间范围的六个主要农业生态系统:玉米-豆类(24.9%)、玉米-豆类-农林业(31.2%)、玉米-豆-农林业-高价值树木 (18.9%)、林场 (7.0%)、森林 (15.6%) 和牧场 (2.3%)。由于历史土地利用变化和后来的制度干预,农林业和其他基于树木的农业生态系统在该地区占主导地位。本研究发现,结合使用土壤调查、地理信息系统和建模,在定位、制图和评估小农农业生态系统中的土壤流失方面是可靠的。农业生态系统在坡度、植被覆盖、土壤条件和土壤流失方面存在显着差异(p < 0.05)。与天然林(1.57 t ha-1 yr-1)相比,玉米-豆类农业生态系统(28.3 t ha-1 yr-1)中的土壤流失量是天然林(1.57 t ha-1 yr-1)的 18 倍,原因是土壤覆盖率较低以及保护和耕作方法效率低下。
更新日期:2018-07-11
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