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SOIL & WATER MANAGEMENT & CONSERVATION

Soil Aggregate- and Particle-Associated Organic Carbon under Different Land Uses in Nepal

^a Dep. of Plant and Environmental Sciences, Norwegian Univ. of Life Sciences, PO Box 5003, 1432 Ås, Norway
^b Dep. of International Environment and Development Studies, NORAGRIC, Norwegian Univ. of Life Sciences, PO Box 5003, 1432 Ås, Norway
^c Carbon Management and Sequestration Ctr, Ohio State Univ., Columbus, OH 43210
^d Dep. of Biological and Environmental Sciences, School of Science, Kathmandu Univ., Dhulikhel, Nepal

^* Corresponding author (bharat.shrestha{at}umb.no).

Soil aggregation is an important process of C sequestration and hence a useful strategy to mitigate the increase in concentration of atmospheric CO₂. We studied water stability of soil aggregates (WSA) and soil organic carbon (SOC) associated with aggregates and primary particles in surface (0–10 cm) and subsurface (10–20 cm) layers of cultivated (khet, irrigated lowland, and bari, rainfed upland) and forest lands (dense Shorea forest, degraded forest and shrub land, pine–Shorea forest, Shorea–pine–Schima forest, and Schima–Castanopsis forest) in a mountain watershed of Nepal. Macroaggregates (>2 mm) were abundant in forest soils (41–70%) while microaggregates (<0.5 mm) were abundant (56–63%) in cultivated lands. Pine mixed forest contained more macroaggregates in both layers. Mean WSA in the surface soil was highest in Shorea–pine–Schima forest (96%) and lowest in khet (74%). Macroaggregates in the surface layers contained 14.9 to 24.8 and 5.5 to 20.7 g kg^–1 SOC in cultivated and forest soils, respectively, while microaggregates contained 12.5 to 30.8 and 11.9 to 25.4 g kg^–1 SOC, respectively. The forest soils contained more sand (639–834 g kg^–1) and fewer clay particles (49–95 g kg^–1) than the cultivated soils. Soils under natural forest, however, were characterized by higher SOC associated with all primary particles. Cultivated soils contained higher amounts of clay but less clay-associated SOC than forest soils. The relation between clay content and clay-associated SOC was explained by a quadratic function (R² = 0.45, P = 0.002).

Abbreviations: BD, bulk density • CEC, cation exchange capacity • DF, degraded forest and shrub land • DS, dense Shorea forest • PS, pine–Shorea forest • SC, Schima–Castanopsis forest • SNK, Student–Newman–Kuels test • SOC, soil organic carbon • SOM, soil organic matter • SPS, Shorea–pine–Schima forest • WSA, water stability of soil aggregates

This article has been cited by other articles:

				B. M. Shrestha, G. Certini, C. Forte, and B. R. Singh Soil Organic Matter Quality under Different Land Uses in a Mountain Watershed of Nepal Soil Sci. Soc. Am. J., September 30, 2008; 72(6): 1563 - 1569. [Abstract] [Full Text] [PDF]