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Impacts of landform, land use and soil type on soil chemical properties and enzymatic activities in a Loessial Gully watershed.

Introduction

The Chinese Loess Plateau (32-41[degrees]N, 107-114[degrees]E), with an altitude of 600-2000 m, is in north-western China and covers an area of 640 000 [km.sup.2]. The area is characterised by a continental monsoon climate with ranges of annual average precipitation of 200-650 mm and annual average temperature of 1-14[degrees]C (Tang 2004). The Loess Plateau is a major region in China for the production of winter wheat and summer maize and is in an ecologically degraded zone. The region is characterised by complex landforms, diverse land uses and distinct soil types. The landforms across the plateau include plateau land, terraced land, sloping land and gully bottoms; the land uses include woodland, grassland, orchard and farmland. The distribution of soil properties has been affected by the landforms, land uses, soil types and their interactions on the Loess Plateau (Fu et al. 2002).

Soil quality is defined as the capacity of soil to function within natural or managed ecosystem boundaries, to sustain plant and animal productivity, to maintain or enhance water and air quality, and to support human health and habitation (Karlen et al. 1997). Soil properties play key roles in determining soil processes, which control the transformation of nutrients and their availability to plants and microorganisms and thus affect soil quality and productivity. Understanding the relationships of soil properties with landscape elements (i.e. landforms, land uses, soil types) is essential for assessing soil quality and productivity (Nortcliff 2002; Sanchez et al. 2003; Stocking 2003). Many studies have assessed the relationships between soil properties and landform, land use and soil type, both on the Loess Plateau (Wang et al. 2003; Qiu and Zhang 2006; Qiu et al. 2010; Wei and Shao 2007a, 20076; Wei et al. 2009a, 20096) and in other parts of the world (Florinsky et al. 2004; Templer et al. 2005; Acosta-Martinez et al. 2007; Allison et al. 2007; Dornbush 2007). For example, the values or contents of most soil properties have been found to be higher in forest than in grassland and farmland on the Loess Plateau (Wang et al. 2003; Qiu and Zhang 2006). Wei and Shao (2007a, 20076) reported that soil organic matter (SOC) and total nitrogen (TN) contents and enzymatic activities were higher in plateau land and terraced land of the Loess Plateau than in sloping land and gully bottoms; soil properties varied with the slope position on sloping land. Wei et al. (2009h), however, found that SOC and TN contents, cation exchange capacity (CEC), and alkaline phosphatase and invertase activities in black locust (Robinia pseudoacacia) forest were higher in the soils of gully bottoms than in those from sloping land. All of these findings indicate that the relationships between landscape elements and soil properties are variable, and that landform, land use and soil type have interactive effects on soil properties, which are not well understood. The different types of landforms, land uses and soil types on the Loess Plateau frequently overlap (e.g. farmland is often on plateau land, and grassland is often on sloping land) (Fu et al. 2002); we therefore hypothesise that the effects of various landscape elements on soil properties are interactive.

Among the soil properties, soil pH and CEC, which control the transformation of nutrients and their availability to plants and microorganisms, are the most important and are often used as indexes of soil quality (Li 2001). The SOC and TN contents are important properties determining soil fertility and quality and are viewed as the basis of soil productivity (Reeves 1997; Stocking 2003). Soil enzymes (intra- and extra-cellular) are the mediators and catalysts of biochemical processes essential to soil functions, including nutrient cycling and the decomposition of organic matter. Their activities are strongly dependent on the soil environments and biological conditions (Nannipieri et al. 2002; Acosta-Martinez et al. 2007). The assessment of soil enzymatic activities is simple, requiring labour costs lower than other biochemical analyses (Ndiaye et al. 2000), and the results correlate well with other biological properties (Vepsalainen et al. 2001; Nourbakhsh 2007). Soil enzymes are sensitive to changes in environmental factors (Tscherko et al. 2003; Boerner et al. 2005; Monkiedje et al. 2006), so measuring their activities can help to determine the response of soil quality to land management practices (Dick 1994; Badiane et al. 2001). Invertase, alkaline phosphatase and catalase are commonly measured in arid and semi-arid soils due to their close relationships with soil quality and their sensitivity to changes in landforms, land uses or soil types (Qiu and Zhang 2006; Qiu et al. 2010; Wei and Shao 2007a; Wei et al. 20096). Alkaline phosphatase catalyses the hydrolysis of both organic phosphorus (P) esters and anhydrides of phosphoric acid into inorganic P, and this controls the cycling and availability of soil P in highland soils (Acosta-Martinez and Tabatabai 2000; Acosta-Martinez et al. 2003). Soil invertase catalyses the hydrolysis of sucrose to glucose and fructose and is linked to soil microbial biomass and fertility (Frankenberger and Johanson 1983). Catalase catalyses the conversion of hydrogen peroxide to oxygen and water; it is considered an indicator of aerobic microbial activity and has been correlated with the number of aerobic microorganisms and with fertility (Trasar-Cepeda et al. 1999; Garcia-Gil et al. 2000).

To test our hypothesis, we investigated the major chemical properties and enzymatic activities of soils in a typical gully watershed of the Loess Plateau to understand the main and interactive effects of landforms, land uses and soil types on soil properties in such a complex landscape. Samples of the various soil types of each type of land use and landform were collected from the top 20 cm. The chemical properties and enzymatic activities of the soils were measured. The main and interactive effects of landform, land use and soil type on soil properties were assessed. The results should provide valuable information for the management of the land in the gully region of the Loess Plateau and similar regions worldwide.

Materials and methods

Study area

The experiment was conducted in the Wangdonggou watershed site (35[degrees]12'-35[degrees]16'N, 107[degrees]40'-107[degrees]42'E) in Changwu County, Shaanxi Province, China. The site is a long-term field research station as part of the Chinese Ecosystem Research Network (CERN). It lies in the gully region of the Loess Plateau, a region topographically characterised by plateaus and gullies, with an altitude of 800-1200 m and covering an area of 850 ha. The area is characterised by a warm-temperate, sub-humid continental climate. Climatic records show an average annual temperature of 9.1[degrees]C. The frost-free period averages 171 days per year. The average annual precipitation is 584 mm, with rainfall mainly concentrated in June-September but varying greatly from year to year.

The landforms of the study area include plateau land (35%), sloping land (34%), gully bottoms (9%) and constructed terraced land (22%). The land-use pattern comprises agricultural land (46%), apple orchards (15%), woodland (32%) and grassland (7%). Winter wheat and maize are the main crops in the agricultural land. The woodlands predominantly comprise black locust. The grassland consists of both natural and planted grasses. The soils are black loessial (42.4%), cultivated loessial (37.5%) and red clay soils (20.1%), which belong to Chernozems, Cambisols and Regosols, respectively, according to International Soil Taxonomy (FAO 1998). Details of the three soils have been described by Hao and Liang (1998).

Soil sampling and chemical analyses

The sampling scheme was designed by CERN for this watershed in 1994 and 2002. In total, 202 samples were collected from the top 20 cm of the three soil types (Chernozems, Cambisols and Regosols) of each type of land use (agricultural land, orchards, woodland and grassland) and each landform (plateau, sloping and terraced lands and gully bottoms) (Table 1). The locations of the sampling sites were identified in the field using a global positioning system (Trimble Pro XR; Trimble Inc., Sunnyvale, CA, USA). Each of the 202 samples was composed of five local subsamples, which were collected by a tube auger 5 cm in diameter. Large pieces of undecomposed organic material were removed by hand, and the moist field soils were then brought to the laboratory, air-dried and ground to pass through 1.00- and 0.25-mm nylon screens before laboratory analysis.

Soil pH, CEC, SOC and TN were measured using the methods of Page et al. (1982). Soil pH was determined using an electrode pH meter in a 1:2 soil: water suspension. The CEC was determined by replacement of exchangeable cations by ammonium acetate. The SOC content was determined by the Walkley Black method, and TN content was determined by the Kjeldahl method.

Invertase activity was measured using the procedure described by Zhou and Zhang (1980). Five mL of 0.067 mol [L.sup.-1] phosphoric acid buffer at pH 5.5 and 15 mL of substrate (0.234 mol [L.sup.-1] sucrose) were added to 5 g of soil and incubated at 37[degrees]C for 2h. Three mL of 0.027 mol [L.sup.-1] 3,5-dinitrosalicylic acid was then added into 1 mL of soil filtrate, and the mixture was heated for 5 min in a water bath at 100[degrees]C. The amount of 3-amino-5-nitrosalicylic acid formed was determined with a spectrophotometer at 508 nm, and the activity was expressed as [micro]katal [kg.sup.-1] soil.

Alkaline phosphatase activity was measured using the procedure described by Zhou and Zhang (1980) using 0.02 mol [L.sup.-1] disodium phenyl phosphate as substrate. After treatment with 0.25 mL of toluene, 20 mL of a mixture of disodium phenyl phosphate and 0.2 mol [L.sup.-1] borate buffer at pH 9.4 was added to 5 g of soil and incubated at 37[degrees]C for 2 h. The soil filtrate was then mixed with 0.25 mL of ammonia water buffer at pH 9.8, 0.5 mL of 0.086 mol [L.sup.-1] 4-aminoantipyrine and 0.5 mL of 0.24 mol [L.sup.-1] potassium ferricyanide. The amount of phenol formed was determined with a spectrophotometer at 510nm, and the activity was expressed as [micro]katal [kg.sup.-1] soil.

Catalase activity was measured using the potassium permanganate titration method (Johnson and Temple 1964). A mixture of 40 mL of distilled water and 5 mL of 0.3% [H.sub.2][O.sub.2] was shaken for 20 min, and 5 mL of 3 mol [L.sup.-1] [H.sub.2]S[O.sub.4] was then added to the soil filtrate. Finally, the filtrate was titrated with 0.1 mol [L.sup.-1] potassium permanganate. The activity was expressed as mkatal [kg.sup.-1] soil.

Statistical analyses

General linear models for unbalanced analyses of variance, which are designed for unbalanced datasets, were conducted to test the main and interactive effects of landform, land use and soil type on soil properties. Some combinations had small samples, so we did not test the interactive effects of landform x land use x soil type. To test the effects of landform on soil properties, we assessed the effects within and across land uses and soil types. Woodland and agricultural land were not distributed in all four landforms, so we only tested the effects of landform in orchard and grassland. We also tested the effects of land-use type within and across landforms to determine the effects of land use under specific landform conditions. Correlation analysis was used to evaluate the relationships among the chemical properties and enzymatic activities of the soils. Statistical analyses were conducted using SAS software (SAS Institute 1999).

Results

General patterns of chemical properties and enzymatic activities of the soils

Invertase activity and pH had the largest and smallest variations, respectively, in the Wangdonggou watershed; their corresponding coefficients of variation (CVs) were 58.3% and 1.58%, respectively (Table 2). The spatial variations of the four chemical properties followed the order SOC content >TN content>CEC> pH. The range of CEC was 11.9-28.7 cmol (+) [kg.sup.-1] with a CV of 17.5%. The contents of SOC and TN had large CVs of ~30%. The activities of phosphatase and invertase were variable, whereas the activity of catalase changed only slightly across the watershed (Table 2).

Effects of landform and soil type on the chemical properties and enzymatic activities of the soils

Landform and soil type generally affected the chemical properties and enzymatic activities significantly (Table 3). Averaged across land-use and soil types, the soil pH, CEC and SOC content were all higher for plateau land and sloping land than for gully bottoms or terraced land. The TN concentrations were significantly higher for plateau land but were similar among most landforms. Alkaline phosphatase activity was highest in plateau land and lowest in terraced land; invertase activity was higher in plateau land and gully bottoms but lower in sloping and terraces lands; and catalase activity tended to be highest in plateau land and lowest in terraced land (difference not significant) (Table 4).

When tested within land-use types, the contents of TN and SOC and the activities of alkaline phosphatase and invertase in grassland were significantly higher in plateau land than in the other landforms. The TN and SOC contents and invertase activity in orchard soils were significantly higher in plateau land than in the other landforms. Other soil properties in grassland and orchards were not significantly affected by landform (Fig. 1). When tested within soil types, most soil properties were significantly higher in plateau land than in the other landforms in Chernozems and Regosols soils and were significantly higher in plateau and sloping lands in Cambisols (Table 4).

Averaged across the land-use types and landforms, Chernozems had significantly lower pH values and CECs, but higher SOC and TN contents than Regosols. Chernozems had higher activities of alkaline phosphatase and invertase but a lower activity of catalase than Regosols, although the activity of alkaline phosphatase did not significantly vary with soil type. The values of the properties and enzymatic activities in Cambisols were generally intermediate compared with other soil types (Table 4). When tested within land-use types, soil properties were not affected by soil types for agricultural land, orchards and grassland. For the woodland, the pH was significantly lower in Chernozems, whereas the contents of TN and SOC were significantly higher in Chernozems.

We observed a significant interactive effect between landform and soil type (Table 4). For different combinations of landform and soil type, the combinations including plateau land, Chernozems or Regosols had significantly higher values of most soil properties or enzymatic activities, suggesting that landform and soil type play important roles in determining the spatial patterns of soil properties and enzymatic activities across the watershed.

Effects of land use on the chemical properties and enzymatic activities of the soils

Changes in land use not only alter land-cover conditions, they are also associated with different practices of soil management, leading to changes in chemical properties and enzymatic activities. Chemical properties and enzymatic activities varied significantly with land-use patterns in the Wangdonggou watershed when tested across landform and soil type (Fig. 2). Across the entire dataset, the lowest pH values were observed in woodland soils: 0.11, 0.14 and 0.10 units lower than in grassland, agricultural and orchard soils, respectively. The SOC and TN contents followed a similar trend with respect to land-use type; contents were higher in woodland and grassland soils and were lower in the agricultural and orchard soils. The CEC followed the order of grassland > woodland and agricultural land > orchards. Highest activities of alkaline phosphatase and catalase were generally in grassland, and lowest activities were in orchard soils. The highest invertase activity was in woodland and agricultural soils, and the lowest in orchard soils. Our examinations within landform types showed that soil properties and enzymatic activities were not affected by land-use type in plateau land but were affected by land use in the other landforms (Fig. 1). Interactive effects between land use and soil type, and between land use and landform, on soil properties were not significant.

Discussion

Effects of landform and soil type

Landform is the major factor controlling the redistribution of surface runoff and thereby water movement and mass transport in soils. Changes of these processes can influence chemical properties and enzymatic activities (Florinsky et al. 2004; Khan et al. 2005; Martin and Timmer 2006). The differences in SOC and TN contents over the four landforms were likely due to two factors. First, the four landforms had different soil management practices. The land-use types in the plateau land were orchards, agricultural land and planted grassland, which had similar management practices. Large amounts of organic material from a village on the plateau and nitrogen fertiliser have been applied to the surrounding cultivated fields in the plateau (Hao and Liang 1998). As a result, the contents of SOC and TN were significantly higher here than with the other landforms. The sloping land, terraced land and gully bottoms are far from the village, and manure and chemical fertilisers have rarely been applied to those soils. Second, landform changes the distributions of light, heat and rainwater by altering the distribution of surface runoff and, thus, indirectly influences the chemical and biological conditions of the soil. Relative to plateau land, the sloping land and gully bottoms receive more light and heat but less rainwater in the study area (Hao and Liang 1998). Such imbalances of energy and water distributions could be favourable to the mineralisation of organic carbon and nitrogen on the slopes and gullies, while the moderate soil-water conditions on the plateau land could enhance microbial activities, which favour the formation of humus (Gaiser et al. 1994). The combined effects of the application of organic material and better water conservation may have produced higher levels of SOC and TN for plateau land than for sloping land and gully bottoms. Soil CEC is determined by types of soil minerals and organic matter present (Li 2001; Liang et al. 2006), so CEC was consistent with the trends of SOC content across the four landforms (Table 4).

[FIGURE 1 OMITTED]

Our results show that soil enzymatic activities were significantly correlated with landform (Table 4). This finding was expected, because soil moisture, temperature, pH, and SOC and TN contents affect soil enzymatic activities (Acosta-Martinez et al. 2007). Alkaline phosphatase activity is generally pH-dependent (Acosta-Martinez and Tabatabai 2000; Acosta-Martinez et al. 2003), but in our study, soil pH did not vary sufficiently to explain the variation in alkaline phosphatase activity, even though the two variables were significantly correlated (Table 5) and the landforms had significantly different pH values (Table 4). We therefore ascribe the differences in enzymatic activities with landforms to differences in SOC and TN contents, consistent with previous findings that the activities of alkaline phosphatase and invertase are closely associated with SOC and TN contents (Gianfreda et al. 2005; Xu et al. 2006; Aira et al. 2007). This conclusion was also supported by our observation that the two enzymatic activities followed an order similar to SOC and TN contents across the four landforms. In contrast to these two enzymes, catalase activity was not significantly affected by landform type, indicating that it responded slowly to the changes in soil moisture, temperature, pH and SOC and TN contents due to differences in landform.

The difference in soil properties with soil types was mainly influenced by soil development and parental materials. The accumulation and eluviation of humus occurring in the Chernozems led to higher SOC and TN contents and lower pH values relative to Cambisols and Regosols (Hao and Liang 1998). The CEC increased with the content of clay particles in different soils, which supply abundant exchange sites for cation adsorption. The content of clay particles <0.01 mm in size followed the order of Regosols (28.0 [+ or -] 1.9%) > Chernozems (25.6 [+ or -] 0.8%) > Cambisols (22.5 [+ or -] 1.2%), and thus CEC followed a similar order. In our experiment, the variance of enzymatic activities was mainly affected by soil properties, which were largely determined by soil type. We therefore ascribe the differences in enzymatic activities with soil type to differences in SOC and TN contents.

[FIGURE 2 OMITTED]

We observed significant interactive effects between landform and soil type on soil properties and alkaline phosphatase and invertase activities (Table 3), possibly because landform plays a decisive role in soil development (Swanson et al. 1988). The Chernozems in the Wangdonggou watershed are mainly in the plateau land, whereas the other two soils are mainly in sloping land, terraced land and gully bottoms. Higher SOC and TN contents and alkaline phosphatase and invertase activities were observed in plateau land among the landforms and Chernozems among the soil types, with lower contents in other landforms and soil types (Table 4). Soil pH was higher in plateau and sloping lands among the landforms, and higher in Cambisols and Regosols among the soil types. The CEC in soils is related to soil pH, organic matter content and clay mineralogy (Gillman 1981; Mahboubi et al. 1993; Liang et al. 2006). The significant relationships of CEC with pH and SOC content (Table 5) made CEC significantly prone to the interaction between landform and soil type. The significant interaction between landform and soil type was thus ascribed to the close relationship between these two landscape elements.

Effects of land use

The pattern of variation of soil pH with land-use types is in agreement with another study, where forest growth was found to decrease soil pH significantly (Falkengren-Grerup et al. 2006). The low pH of woodland soils was ascribed to the large input of organic matter to soils from the release of organic acids during the decomposition of organic material (Falkengren-Grerup et al. 2006). The differences in SOC and TN contents between agricultural and orchard lands were caused by the amount of fertilisers applied. The amount of manure and nitrogen fertiliser applied to agricultural land in the Wangdonggou watershed was 7.2 and 2.5 times that applied to orchards, respectively (Hao et al. 1991). In recently established woodland and grassland that did not receive chemical fertilisers and manure, SOC and TN contents initially increased because of the accumulation and incorporation of litterfall into the soils, and the contents were then maintained at higher levels than in the agricultural land and orchards (Billings 2006; McLauchlan et al. 2006).

The observed relationships between enzymatic activities and land-use types were generally in agreement with previous research that reported lower enzymatic activities in cultivated than in the same, uncultivated soils (Acosta-Martinez et al. 2003, 2004). The higher enzymatic activities in grassland and forest were accounted for by their higher microbial biomass (Acosta-Martinez et al. 2004) and greater microbial diversity compared with farmland (McKinley et al. 2005), which are dependent on the practices of land management and the input of biomass to the soils. The numbers and diversity of soil microorganisms in surface soils have been reported to follow the order agricultural land < forest< grassland (Sicardi et al. 2004). Enzymatic activities may thus act as indicators of ongoing, dominant soil bio-transforming processes.

Land-use types had no significant interactive effects with landform or soil types (Table 3), indicating that the effects of land use were similar or there was no effect on soil properties at specific landforms or soil types, perhaps because the landform and/or soil type played a decisive role in the distribution of soil properties in the small watershed of the Loess Plateau. In the plateau land, soil properties were mainly affected by the practices of fertilisation and tillage for all land uses (Mijangos et al. 2006; Wei et al. 2006). In the terraced land, soil properties were mainly determined by the construction of terraced land and soil type (Wei et al. 2006). The soils in different land-use types in cither plateau or terraced land received similar soil management practices. The input of organic materials from aboveground biomass to the soils, however, was higher in the grassland and woodland for the terraced land. In sloping land, the soil properties were mainly affected by soil erosion (Wei and Shao 20076). The grassland and woodland on sloping land have the potential to decrease soil erosion and improve soil properties. The values of soil properties were not affected by land-use type in the plateau land but were higher in the woodland and grassland than in other land uses in the sloping and terraced lands. In the gully bottoms, the input of organic materials from litterfall resulted in the higher TN and SOC contents in the woodland soils.

Implications for land management

The landscape elements significantly affected the soil properties in the gully watershed of the Loess Plateau, and landform and soil type had significant interactive effects on most of the properties, supporting our hypothesis that the effects of various landscape elements on soil properties are interactive. Our results also demonstrated that the soils in the plateau land had higher soil fertility and quality because of their proximity to dwellings and the benefit of applied organic manure and chemical fertilisers among the four landforms, whereas woodland and grassland had great potential for improved soil quality due to the lower lesser of human activities, greater ability to prevent soil erosion and high returns of aboveground biomass to the soils in the sloping and terraced lands and gully bottoms. We therefore suggest that crops and orchards should be located on plateaus to make full use of their better land resources and to obtain the best economic returns, and grasses should be planted on terraced land and woodland on slopes and in gully bottoms to improve soil quality and to prevent soil erosion and soil loss, which are major environmental problems in the area.

In this paper, we studied the effects of landform, land use and soil type on major soil chemical properties and activities of alkaline phosphatase, invertase and catalase. Other parameters involved in nitrogen and phosphorus cycling, the carbonates, and the activities of other enzymes such as urease, dehydrogenase, fluorescein diacetate hydrolases and [beta]-glucosidase should be measured as useful indicators to establish the comprehensive relationships between biogeochemical processes of soils and landscape elements.

http://dx.doi.org/10.1071/SR13202

Received 12 July 2013, accepted 28 February 2014, published online 3 June 2014

Acknowledgements

This study was supported by the Program for New Century Excellent Talents in University (NCET-13-0487) and the National Science and Technology Supporting Major Project (2011BAD31B0).

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Yajun Hao (A), Qingrui Chang (A,D), Linhai Li (B), and Xiaorong Wei (A,C,D)

(A) College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China.

(B) Beijing Museum of Natural History, Beijing 100050, China.

(C) State Key Laboratory of Soil Erosion and Dryland Farming in the Loess Plateau, Northwest A&F University, Yangling, 712100 China.

(D) Corresponding authors. Emails: changqr@nwsuaf.edu.cn; xrwei78@163.com; weixr@nwsuaf.edu.cn
Table 1. Combination of landform, land use and soil type and the
sample numbers for each combination in Wangdonggou watershed

Landform          Land use            Soil type    No. of samples

Gully bottoms     Woodland            Cambisols    2
Gully bottoms     Woodland            Chernozems   26
Gully bottoms     Woodland            Regosols     3
Gully bottoms     Grassland           Cambisols    1
Gully bottoms     Grassland           Regosols     2
Gully bottoms     Orchards            Cambisols    10
Gully bottoms     Orchards            Chernozems   13
Plateau land      Agricultural land   Cambisols    8
Plateau land      Agricultural land   Regosols     3
Plateau land      Grassland           Cambisols    15
Plateau land      Grassland           Chernozems   1
Plateau land      Grassland           Regosols     18
Plateau land      Orchards            Cambisols    5
Plateau land      Orchards            Chernozems   3
Plateau land      Orchards            Regosols     2
Sloping land      Woodland            Cambisols    3
Sloping land      Woodland            Chernozems   2
Sloping land      Woodland            Regosols     2
Sloping land      Grassland           Cambisols    22
Sloping land      Grassland           Regosols     9
Sloping land      Orchards            Cambisols    6
Sloping land      Orchards            Chernozems   1
Sloping land      Orchards            Regosols     1
Terraced land     Agricultural land   Chernozems   1
Terraced land     Woodland            Cambisols    4
Terraced land     Woodland            Chernozems   15
Terraced land     Woodland            Regosols     1
Terraced land     Grassland           Cambisols    20
Terraced land     Orchards            Chernozems   2
Terraced land     Orchards            Regosols     1

Total                                              202

Table 2. General patterns of soil chemical properties and enzymatic
activities in the Wangdonggou watershed

CEC, Cation exchange capacity; TN, total nitrogen; SOC, soil organic
carbon; s.d., standard deviation; CV, coefficient of variation

            pH            CEC                   TN           SOC
                  (cmol(+) [kg.sup.-1])   (g [kg.sup.-1])

Mean       8.19           17.94                0.80          7.00
s.d.       0.13            3.14                0.23          2.21
CV (%)     1.58           17.48               28.22         31.57
Minimum    7.71           11.93                0.31          2.36
Maximum    8.57           28.67                1.66         16.18

           Phosphatase    Invertase   Catalase
              (mkatal [kg.sup.-1])

Mean          0.498         2.610      3.856
s.d.          0.227         1.522      0.118
CV (%)       45.65         58.32       3.06
Minimum       0.027         0.002      3.147
Maximum       1.403         7.853      4.158

Table 3. Analysis of variance of soil properties as affected by
landscape elements

CEC, Cation exchange capacity; TN, total nitrogen; SOC, soil
organic carbon. * P < 0.05; ** P < 0.01; n.s., not significant
at P = 0.05

                        PH      CEC       TN        SOC

Landform                **      **        **        **
Land use                **      **        **        **
Soil type               **      **        **        **
Landform x land use    n.s.    n.s.      n.s.      n.s.
Landform x soil type    *        *        **        **
Land use x soil type   n.s.    n.s.      n.s.      n.s.

                       Phosphatase   Invertase   Catalase

Landform                   **           **          **
Land use                   **           **          **
Soil type                 n.s.          **          **
Landform x land use       n.s.         n.s.        n.s.
Landform x soil type       **           **         n.s.
Land use x soil type      n.s.         n.s.        n.s.

Table 4. Effects of landform and soil type on soil properties and
enzymatic activities in the Wangdonggou watershed
CEC, Cation exchange capacity; TN, total nitrogen; SOC, soil
organic carbon. Within columns, values followed by the same letter
are not significantly different (P>0.05) between landforms,
soil types, or their combinations

                                                        CEC
                                                      (cmol(+)
                                                    [kg.sup.-1])
                                         PH

                                  Mean      s.d.   Mean      s.d.

Landform     Plateau land (PL)    8.24a     0.11   18.9a     3.27
             Sloping land (SL)    8.24a     0.11   19.1a     3.40
             Gully bottoms (GB)   8.14b     0.09   17.4b     2.54
             Terraced land (TL)   8.13b     0.16   16.3b     2.46
Soil type    Chernozems (CH)      8.13b     0.12   17.7b     2.06
             Cambisols (CM)       8.23a     0.13   17.3b     3.41
             Regosols (RG)        8.19a     0.10   19.7a     3.43
Landform x   PL x CH              8.27a     0.07   18.0ab    1.04
soil type    PL x CM              8.29a     0.12   17.7ab    1.69
             PL x RG              8.16ab    0.08   20.5a     1.52
             SL x CH              8.32a     0.06   16.2b     1.49
             SL x CM              8.23ab    0.11   19.3a     1.77
             SL x RG              8.26a     0.09   19.1a     1.54
             GB x CH              8.12b     0.09   17.6ab    1.02
             GB xCM               8.18ab    0.10   15.7b     1.03
             GB x RG              8.18ab    0.09   19.9a     2.24
             TL x CH              8.05b     0.13   18.0ab    1.01
             TL x CM              8.2 lab   0.16   15.2b     1.00
             TL x RG              8.02b     0.19   13.6c     0.48

                                         TN                SOC
                                            (g[kg.sup.-1])

                                  Mean      s.d.   Mean       s.d.

Landform     Plateau land (PL)    0.91a     0.28   8.17a      2.80
             Sloping land (SL)    0.77b     0.24   7.17b      2.39
             Gully bottoms (GB)   0.78b     0.18   6.60bc     1.44
             Terraced land (TL)   0.73b     0.15   5.90c      1.06
Soil type    Chernozems (CH)      0.86a     0.35   7.87a      2.26
             Cambisols (CM)       0.76b     0.19   6.75b      1.98
             Regosols (RG)        0.72b     0.16   6.80b      1.43
Landform x   PL x CH              0.87b     0.06   7.32b      0.81
soil type    PL x CM              0.79b     0.10   7.08b      1.74
             PL x RG              1.05a     0.17   9.65a      2.92
             SL x CH              0.55c     0.03   4.90c      0.80
             SL x CM              0.82b     0.12   7.70b      1.97
             SL x RG              0.70bc    0.11   6.42b      2.12
             GB x CH              0.83b     0.08   6.91b      1.17
             GB xCM               0.73bc    0.06   6.36b      0.94
             GB x RG              0.54c     0.10   4.79c      1.38
             TL x CH              0.83b     0.07   6.59b      0.78
             TL x CM              0.67bc    0.06   5.42bc     0.78
             TL x RG              0.70bc    0.09   5.37bc     0.59

                                                     Invertase
                                                    ([micro]katal
                                   Phosphatase      [kg.sup.-1])

                                  Mean      s.d.   Mean      s.d.

Landform     Plateau land (PL)    0.30a     0.27   2.91a     1.47
             Sloping land (SL)    0.25b     0.25   2.29b     1.61
             Gully bottoms (GB)   0.25b     0.17   3.07a     1.62
             Terraced land (TL)   0.19c     0.16   1.99b     1.02
Soil type    Chernozems (CH)      0.26a     0.33   3.39a     1.48
             Cambisols (CM)       0.25a     0.21   2.28b     1.34
             Regosols (RG)        0.24a     0.17   2.01b     1.46
Landform x   PL x CH              0.22b     0.08   4.17a     0.66
soil type    PL x CM              0.28ab    0.12   2.53b     0.68
             PL x RG              0.34a     0.16   2.71b     0.69
             SL x CH              0.12c     0.02   1.20cd    0.22
             SL x CM              0.29a     0.11   2.70b     0.84
             SL x RG              0.19b     0.13   1 56c     0.62
             GB x CH              0.26ab    0.07   3.64a     0.75
             GB xCM               0.25ab    0.07   2.41b     0.37
             GB x RG              0.13c     0.12   0.38d     0.18
             TL x CH              0.22b     0.09   2.79b     0.54
             TL x CM              0.17bc    0.06   1.44c     0.24
             TL x RG              0.12c     0.02   1.31c     0.09

                                     Catalase

                                  Mean      s.d.

Landform     Plateau land (PL)    3.91a     0.11
             Sloping land (SL)    3.87a     0.10
             Gully bottoms (GB)   3.86a     0.07
             Terraced land (TL)   3.78a     0.15
Soil type    Chernozems (CH)      3.85b     0.10
             Cambisols (CM)       3.83b     0.13
             Regosols (RG)        3.93a     0.08
Landform x   PL x CH              3.89a     0.09
soil type    PL x CM              3.88a     0.05
             PL x RG              3.94a     0.03
             SL x CH              3.84a     0.02
             SL x CM              3.84a     0.05
             SL x RG              3.94a     0.03
             GB x CH              3.86a     0.03
             GB xCM               3.83a     0.02
             GB x RG              3.91a     0.05
             TL x CH              3.81a     0.05
             TL x CM              3.74a     0.09
             TL x RG              3.76a     0.06

Table 5. Correlation coefficients among soil chemical and enzymatic
properties

CEC, Cation exchange capacity; TN, total nitrogen; SOC, soil organic
carbon; n = 202; significant values of r, [r.sub.0.05] = 0.138,
[r.sub.0.01] = 0.181

                 PH      CEC     TN      SOC

CEC            -0.193
TN             -0.379   0.490
SOC            -0.278   0.535   0.966
Phosphatase    -0.210   0.400   0.779   0.796
Invertase      -0.295   0.300   0.755   0.694
Catalase       0.148    0.211   0.144   0.204

               Phosphatase   Invertase

CEC
TN
SOC
Phosphatase
Invertase         0.676
Catalase          0.207         0.158
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Author:Hao, Yajun; Chang, Qingrui; Li, Linhai; Wei, Xiaorong
Publication:Soil Research
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Date:Aug 1, 2014
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