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| Effects of Types of Farmland Returning to Forest on the Dynamics of Soil Aggregate and Organic Carbon in Upper Reaches of Minjiang River |
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| DOI：10.16768/j.issn.1004-874X.2023.04.010 |
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| Abstract: |
| 【Objective】On the occasion of the implementation of the policy of returning farmland to forest for 20 years, the dynamic changes of soil aggregates and soil organic carbon (SOC) after returning farmland to forest in upper reaches of the Minjiang River were quantitatively studied, which provided scientific data support for ecological governance and ecological agriculture development in arid valleys.【Method】Taking the native forest as the control and the ecological forests (eco-forests) and orchards (cherry, crisp plum, apple) as research objects, the particle size composition, stability and SOC distribution of soil water-stable aggregates of various land types were analyzed, and the mixed effect was applied to determine the contribution of forest land type, soil depth, altitude gradient, gravel content (GC) and other factors to soil aggregate stability and organic carbon dynamics.【Result】The content of macro-aggregates (> 0.25 mm) in orchards was significantly lower than that in eco-forests, and that in both was significantly lower than that in native forests. The contents of soil agglomerates of various sizes in the native and eco-forests showed as: 5-10 mm > 2-5 mm > 0.25-2 mm > 0.053-0.25 mm > 0-0.053 mm, those in the orchards ranked as: 0.25-2 mm > 2-5 mm > 5-10 mm > 0.053-0.25 mm > 0-0.053 mm. In the 5-15 cm soil layer, the contents of
5-10 mm and 2-5 mm agglomerates in cherry orchards were significantly greater than those in crisp plum orchards and apple orchards. Soil aggregate stability indexes(MWD and GMD) showed as: native forests > eco-forests > cherry orchards > crisp plum orchards and apple orchards, and there were no significant differences between crisp plum orchards and apple orchards. The SOC content(SOCC) in the 0-5 cm soil layer showed as native forests > eco-forests > cherry orchards > crisp plum orchards and apple orchards, and the difference showed a decreasing trend with the increase of soil depth. SOC(SOCS) stocks at a depth of 0-30 cm were highest in eco-forests (63.1 t/hm2), followed by cherry orchards (56.1 t/hm2), apple orchards (52.5 t/hm2), and crisp plum orchards (51.3 t/hm2), while the SOCS in native forests were the lowest (47.3 t/hm2). At a dep th of 30-60 cm, cherry orchards had the highest SOCS (40.3 t/hm2), followed by crisp plum orchards (32.9 t/hm2), and apple orchards (2 9.3 t/hm2), and eco-forests had the l owest SOCS (24.7 t/hm2). SOC distribution was characterized as ‘high content and low stock’ in native forests, ‘high content and high stock’ in eco-forests, and ‘low content and high stock’ in orchards. The dominant factor of soil aggregates stability and organic carbon content was forest type, and the dominant factor of SOCS was soil depth.【Conclusion】The mountain agriculture of ‘eco-forests on the higher valley and orchards on the lower valley, fruit trees and cattle on the gentle slopes and terraced fields’ is an ideal model for the agriculture development in arid valleys, and the improvement of SOC accumulation in the topsoil should be the priority for the management of orchards in the future. |
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