Plant Soil (2010) 332:207–217 DOI 10.1007/s11104-010-0286-5
REGULAR ARTICLE
Effects of black locust (Robinia pseudoacacia) on soil properties in the loessial gully region of the Loess Plateau, China Liping Qiu & Xingchang Zhang & Jimin Cheng & Xianqiang Yin
Received: 2 June 2009 / Accepted: 8 January 2010 / Published online: 27 January 2010 # Springer Science+Business Media B.V. 2010
Abstract Black locust (Robinia pseudoacacia) has been widely planted in the Loess Plateau for soil and water conservation. The effects of black locust on soil properties has significant role in land use and ecosystem management. However, this beneficial effect has been little studied in the Loess Plateau. The soil properties below black locust and native grass growing in Nanxiaohe and Wangdonggou watersheds, located in the loessial gully region of the Loess Plateau, were studied for changes in soil properties after establishment of black locust. The black locust significantly increased soil cation exchange capacity, organic carbon, total nitrogen, nitrate, and carbon:nitrogen and carbon:phosphorus (P) ratios, as well as some enzymes like alkaline phosphatase and invertase in 0–20 cm or 0–80 cm depths of soil compared to the native grassland in Nanxiaohe and Wangdonggou watersheds. However, the effects on ammonium, total P, and extractable P and potassium were not consistent in both watersheds. There were more obvious differences in soil properResponsible Editor: Tim Simon George. L. Qiu : X. Zhang : J. Cheng : X. Yin State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A & F University, Yangling, Shaanxi 712100, China L. Qiu (*) : X. Zhang : J. Cheng Institute of Soil and Water Conservation, CAS&MWR, Yangling, Shaanxi 712100, China e-mail:
[email protected]
ties between black locust land and grassland for Nanxiaohe watershed than for Wangdonggou watershed, suggesting that the effects of black locust on most soil properties increase with black locust age. The results indicate that black locust has potential to improve soil properties in the loessial gully region of the Loess Plateau and the improvements were greater in long-term than middle-term black locust stands. Keywords Afforestation . Black locust . Native grass . Soil properties . The Loess Plateau
Introduction Afforestation is a useful way to prevent soil degradation and loss by erosion (Requena et al. 2001; Clemente et al. 2004). This process is often characterized by the land-use shift from native grassland to plantations of fast-growing exotic species of trees (Farley and Kelly 2004). The influences of this shift in land use on soil properties (e.g. physicochemical, nutritional and biological), water resources and on the regional and global carbon (C) cycles are important issues attracting attention from researchers in various fields (Garcia-Quijano et al. 2005; Jackson et al. 2005; Laclau et al. 2005; Nouvellon et al. 2008). Afforestation in grassland is usually accompanied by increased soil organic C and nutrients, and improves soil structure due to the accumulation of residues in soils under the plant canopy (Menyailo et
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al. 2002; Hazlett et al. 2007). Residue decomposition contributes greatly to increase of C and nutrient (N, P) pools through incorporation of C and associated nutrients into underlying soils (Mendham et al. 2002; Piirainen et al. 2002; Chen and Xu 2005). Cao et al. (2007) observed a dramatic increase in total and available N and organic C by afforestation in the Loess Plateau. An and Huang (2006) found enhanced accumulation of organic C and total N in soils by 8and 18-year-old Caragana korshinski plantations in the semi-arid area of the Loess Plateau. Similarly, afforestation can increase the bioavailability of soil organic P and accelerate its mineralization rate using Mongolian pine (Zhao et al. 2007), Norway spruce (Firsching and Claassen 1996), Chinese fir (Chen 2003) and radiata pine (Chen et al. 2002). Chen et al. (2008a) ascribed this to a combination of factors including the greater P demand and uptake by trees, the improved solubility of organic P by root and microbial exudates, greater tree-root phosphatase activity associated with ectomycorrhizae and favorable soil moisture and temperature conditions. However, description of afforestation effects on soil properties should consider the influences of site conditions. Campbell et al. (1994) and Kamara and Haque (1992) found that C and nutrients differed between soils under African savanna and adjacent open areas, to a greater extent in sandy soils as compared to fine-textured soils. Rhoades et al. (2001) discovered that the effects of N-fixing alder on soil N conditions varied significantly with sites in northwestern Alaska in terms of increased total and available N in floodplains but had little influence in upland sites. Also, the influence of American chestnut on soil C, N and chemical properties differed markedly with sites (Rhoades 2007). These studies suggest that site conditions may regulate the effects of afforestation on soil biogeochemical processes. Black locust (Robinia pseudoacacia) is a promising tree for reforestation due to its fast growth and ability to fix atmospheric N and has been planted in the Loess Plateau on an area >70,000 ha since the 1950s (Guo et al. 2005). Black locust can greatly improve soil properties in terms of enhanced N content and availability (Olesniewicz and Thomas 1999; Rice et al. 2004; Tateno et al. 2007), soil available P pools (Gillespie and Pope 1990), soil structure and quality, root biomass, and soil organic C sequestration (Ussiri et al. 2006), and thus also
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improve soil biological properties (Xue et al. 2007). However, studies on the effects of black locust afforestation on soil properties in the Loess Plateau grasslands have mainly focused on soil water conditions (He et al. 2003; Wang et al. 2004, 2008; Chen et al. 2008b). Few studies have addressed the impact of black locust afforestation on soil chemical properties and fertility in the area, particularly for different sites and soil depths. This has become a concern since changes in soil properties determine the sustainable use of land resources and also the rehabilitation of degraded environments in the Loess Plateau. We hypothesized that soils differ significantly between adjacent microsites occupied by black locust and by native grass, and the effects of vegetation on soil varies with watersheds. To test our hypothesis, we investigated the soil properties between native grassland and black locust forest at two small watersheds in the loessial gully region of the Loess Plateau.
Materials and methods Site description The study was conducted in Nanxiaohe watershed (NW) and Wangdonggou watershed (WW), which are located in the loessial gully region of the Loess Plateau. This region lies in the southern part of the Loess Plateau and is characterized by a warmtemperate sub-humid continental climate. Black locust was planted in the native grassland in 1955 and 1985 for the NW and WW, respectively. Before establishment of black locust, the native grassland was not disturbed by grazing and human activity. After planting of black locust, the native grassland and forest land were fenced to avoid human disturbance. The characteristics of both watersheds are presented in Table 1. Field investigation, soil sampling and analysis Sampling was designed to compare the effects of black locust on soil properties in NW and WW. In May 2005, 36 sampling plots (20 m×20 m; 9 plots × 2 vegetation stands × 2 watersheds) were selected in the native grassland and black locust stand in the two watersheds, respectively. For the black locust stands,
Plant Soil (2010) 332:207–217 Table 1 Soil and climate condition in Nanxiaohe and Wangdonggou watersheds
209 Watersheds
Nanxiaohe
Wangdonggou
Location
35°42′N, 107°37′E
35°14′N, 107°41′E
Watershed area
36.3 km2
8.5 km2
Native grass area
2
1.6 km2
2
3.2 km2
4.2 km
Black locust area
9.3 km
Black locust age
51 years
21 years
Soil texture
Fine silt
Fine silt
