SOIL LOSS FROM EROSION IN THE NEXT 50 YEARS IN KARST REGIONS OF MAYABEQUE PROVINCE, CUBA

SOIL LOSS FROM EROSION IN THE NEXT 50 YEARS IN KARST REGIONS OF

MAYABEQUE PROVINCE, CUBA

J. M. FEBLES-GONZÁLEZ1, M. B. VEGA-CARREÑO2, N. M. B. AMARAL-SOBRINHO3, A. TOLÓN-BECERRA4* AND X. B. LASTRA-BRAVO4

1

University of Havana, Zapata y G, Vedado, Plaza de la Revolución, Havana, CP 10 400, Cuba 2_{Jose Antonio Echeverria Higher Technical University (CUJAE), Ave. 114 No. 11901, Marianao, Havana, Cuba}

3

Universidade Federal Rural do Rio de Janeiro, Br 465 km 7, Seropédica RJ, Brazil 4_{University of Almeria, Ctra. Sacramento s/n. 04120 La Cañada de San Urbano, Almeria, Spain}

Received: 20 February 2012; Revised: 4 May 2012; Accepted: 20 July 2012

ABSTRACT

To date, neither the method nor diagnostic indices employed in Cuba to evaluate erosion of Red Ferralitic or Ferrasol Rhodic soil in karstic regions has taken into consideration morphogenesis in such geo-ecosystems or their relationship with erosion, which has led to sequential degradation of the most productive soils in Cuba. We explore the case for considering A + B horizon depth as one of the basic indices for evaluating the severity of erosion. There is no methodology available for estimating the volume of soil lost through karstic absorption forms (dolines). This article forecasts loss of soil cover using a model which estimates losses of 268
52 to 450
52 mm y1for future scenarios (periods of 25 and 50 years). A mean loss rate of 1
07 mm y1was found in areas cultivated as pastureland during the period from 1986 to 2009, which exceeds the tolerance thresholds proposed by the Universal Soil Loss Equation and the soil formation rates estimated for limestone in Cuba and it is likely there is with a marked tendency for this to increase. These results should be interpreted as afirst estimate for setting loss tolerances as there is no similar experience with own data for a more precise definition of the erosion of soil in karstic regions. Copyright © 2012 John Wiley & Sons, Ltd.

keywords: tolerance; erosion; Cuba; sustainability; dolines; thresholds

INTRODUCTION

In the Cuban Soil Conservation and Improvement Program (Instituto de Suelos, 2001), it was shown that of the 6
6 million hectares that make up the agricultural area of the country, 3
6 are cultivated, and of these, 70 per cent are affected by degrada-tion processes. One of the limiting factors of greatest relevance is erosion, a menace that affects 2
9 million hectares.

However, to date, the specialized literature has not reported erosion loss tolerance rates for Red Ferralitic soil (Ferrasol Rhodic in the World Reference Base, 2006), which makes up 23
56 per cent of the Cuban agricultural land base, and occupies from 80 to 85 per cent of the 5731-km2karst in the provinces of Mayabeque and Artemisa. This coincides with the zones of highest agricultural production, population density and the most important catchments in the territory (Febles et al., in press). In view of the aforementioned data, this study took as its reference the results of research done by Febles et al., in press, in the Pedroso-Mampostón sub-basin in the centre of Mayabeque Province, tofind the tolerance rates for Red Ferralitic soil loss through karst absorption forms

(dolines) under the conditions of use and management to which this region has been subjected for the last 25 years. Main Indicators Applied in Cuba for Evaluating Soil Loss from Erosion in Recent Decades

The use of different nomenclatures and measurement tech-niques has caused problems for comparison, and dissimilar estimates of loss from the state of erosion in the country are frequent (Vega and Febles, 2005). During the 1970s, the geographic comparison method using the map of the Instituto de Suelos (1973) as the basis became a relative priority. Profiles considered typical of each grouping were taken as standards for establishing the extent of erosion. Many researchers applied this method, where the difference in its application was given by the indices used for comparing what were called‘standard profiles’.

Thus, DGSF (1981), MINAGRI (1982), Riverol (1985) and Soca (1987) took as their basic index the relative depth of genetic horizons A and B. Hernández et al. (1980) and Ascanio et al. (1983) studied erosion in Cuban Pardo con carbonato (Inceptisol) soils, selecting the strength of the A and B horizons, organic matter content and runoff from the horizons in‘standard profiles’ as indices. Pérez (1989) also used this approach, but in the context of a toposequence.

*Correspondence to: A. Tolón-Becerra, University of Almeria, Ctra. Sacramento s/n. 04120 La Cañada de San Urbano, Almeria, Spain. E-mail: atolon@ual.es

Land Degrad. Develop. (2012)

Shepashenko et al. (1982, 1984), Riverol (1989) and Riverol and Shepashenko (1989) used depth, mechanical composition, structure, humus content and adsorbent complex composi-tion as indicators for quantitative evaluacomposi-tion to determine the resistance of major Cuban soils to erosion, scoring each type on a scale of 0 to 100 points.

It should be mentioned that the methods and indicators selected by the Instituto de Suelos (MINAGRI, 1982) to deter-mine erodibility did not evaluate the geological formation environment integrally. They overdimensioned depth as the basic diagnostic index (Febles, 2007) and established erosion categories on the basis of a very superficial adaptation of the Soil Survey Staff (1951) Classification to Cuban edaphocli-matic conditions.

These were shown by Riverol (1989) and Riverol and Shepashenko (1989) on maps of current and potential ero-sion in which deep soils, such as the Red Ferralitic, are classi-fied as not eroded (100 points), whereas little evolved or skeletal soils are classified as eroded. Furthermore, in recent years, a thematic cartography of factors for evaluating soil erosion has begun to be applied, taking advantage of the features of the Geographic Information System (GIS), for example, the study by Díaz-Comesañas et al. (2001), Cabrera (2002), Garea (2003), Ponce De León (2004), Díaz-Comesañas et al. (2005), Vega (2006) and Febles (2007).

The use of radioactive isotopes, specifically 137Cs, has been another of the methodologies employed to estimate the erosion rates in agricultural soils in various regions of the country. Gil et al. (2004) used it in the west, Brígido et al. (2006) in Camagüey Province, and Gil et al. (2006) in the centre of Cuba.

The first one to use erosion models was developed by Planas (1986), who made a Universal Soil Loss Equation (USLE) applicability analysis for Cuba. Later, Vallejo and Martínez (2000) and Reyes (2004) took up the USLE model again, implementing it in GIS applications. Ruiz et al. (2006) used the Revised USLE to quantify soil loss in the Cuyaguateje Basin in Pinar del Río Province. Vega (2006),

Febles (2007) and Febles et al. (in press) applied the Morgan–Morgan–Finney (MMF; Morgan et al., 1984; Morgan, 2001) to evaluate soil loss from erosion in dolines. Nevertheless, it is obvious that in Cuba, the use of thematic cartography of factors and the use of erosion models with a physical basis supported by GIS technology to evaluate soil erosion are still not very generalized in spite of the acknowl-edged advantages of these methods (Vega and Febles, 2005). Reflecting on this diversity of approaches for evaluating soil erosion, Febles et al. (2008) have proposed an integrated system of qualitative and quantitative methods for evaluating the process in Cuba. This makes it possible to determine the main agents intervening as causes, the components of the geographic surroundings that participate as factors and cause the emergence and special differentiation of the process, and forms of erosion present in the country. They further underline that in karsts areas, it is not possible to apply the same methods, means and scales of representation used for other geo-ecosystems.

Soil Formation and Loss Rates

It is complicated to define the difference between the soil formation and loss rates. According to Buol et al. (1980), world soil formation rates vary from 0
01 to 7
7 mm y1 (Table I). However, the highest are exceptional, and the mean is somewhere around 0
1 mm y1(Zachar, 1982).

From a conservationist perspective, the purpose must consist of maintaining the productive potential of the soils indefinitely and thereby ensure the sustainability of the agricultural ecosys-tems for an indefinite time (Browning et al., 1947; Wischmeier and Smith, 1978; FAO, 1983).

According to Wischmeier and Smith (1978), tolerable erosion rates for soils in tropical regions are from 4
5 to 11
5 t ha1y1. This loss would still allow crops to be highly productive, so they would be economically and indefinitely sustainable. The most important factors determining the limit of 4
5–11
5 t ha1y1as the soil erosion tolerance are depth, physical properties and other characteristics that affect root Table I. Soil formation rates

Characteristic Formation rate (mm y1) References

Under ideal soil management conditions 0
8 Hudson (1995)

World soil formation rates 0
01–7
7 Buol et al. (1980)

Under natural conditions (from 300 to 1000 years) 25
40 Pimentel et al. (1995) Under normal agricultural practices (in 100 years) 0
25 Pimentel et al. (1995) For agronomically productive soil, assuming a soil density

of 1 Mg2m3and based on predicted weathering of rocks

0
1 Morgan et al. (1984)

Age of limestone eluvial deposits in the Llanura Sur in Mayabeque and Artemisa provinces Derived from rock with 10% impurities, 1 million

years is required for a depth of 15 m

0
05 Iturralde-Vinent (1972); Camacho (1980); Ortega-Sastriques (1984)

Derived from limestone with 1% impurities, 2 million years is required for a depth of 2 m

development, gullying, problems of sedimentation in thefield, loss of seeds, and reduction of organic matter and nutrients. Table I compares general soil formation values to karstic soils. The soil loss tolerances in Table II are used due to lack of concrete experience and available data, but as none of them were found in karstic regions, they are for reference only.

METHODS Study Area

The localities of‘Rosafé Signet’ (Ia) and Boshmenier–Zenea (Ib), located in the sub-basin of the Mampostón River between 22530–23170 latitude North and 8210–82270 longitude West, in the present Mayabeque Province (Table III) were selected as representative of the west of the country, where karstic morphogenesis is well developed widespread and often under agriculture.

This territory is classified as one of the most humid in the Cuban plains. It receives around 76–80 per cent of the rainfall in the present Mayabeque and Artemisa Provinces (Herrera, 1996). The rainfall concentration index varies from 13 to 14 per cent (Vega and Febles, 2006), and the annual rainfall depth is from 1400 to 1600 mm (Izquierdo et al., 1990; CENHICA, 1997). Other characteristics are summarized in Table III.

These areas have undergone water and karstic erosion for the last 25 years, causing the emergence of deep, wide dolines and imposing such a state of dismemberment on the landscape

that the depressions, and the adjacent surfaces that function under their influx such as microcatchments, have become unproductive (Febles et al., 1986; Febles, 1988; Gounou, 1997; Febles et al., 2001; Vega, 2006; Febles, 2007; Febles et al., in press).

Soil Sampling

Seventeen main profiles were characterized by taking soil sam-ples every 10 cm on the top, in the middle and bottom of the curve of the microrelief to examine by comparative descriptive analysis at depths of 0–10 and 0–20 cm and erosion diagnostic horizons A + B0–50 cm, as well as the dynamics, manifestation and intensity of the erosion (Figure 1). The physical and physicochemical properties of the soil samples necessary for application of the model by Morgan et al. (1984) and Morgan (2001) in Febles et al (in press) may be found in Febles et al. (2009).

The reference was profile C1(no apparent erosion), as described by Febles et al. (1986), located in an area in biostasy at a start-ing depth of horizon A0–490 mm, to evaluate the magnitude of the loss of Red Ferralitic soil (Paneque et al., 1991) or Ferrasol Rhodic soil in the World Reference Base (2006).

Data Processing

Soil loss by weight (t ha1y1) for 1986, 1997 and 2009 was converted into linear units (mm y1) by averaging the soil mass density (1
36 Mg m3) as a constant (Marshall et al., 1996). Table II. Soil loss from erosion tolerance

Characteristics Tolerance (t ha1y1) References

In soils with medium to moderately coarse texture and good cultivation practices

11
2 Bennett (1926)

In deep soils, with medium texture, moderate permeability and favourable subsoil

12
5 USLE, Soil Survey Staff (1984) Depending on the depth, physical properties and other

characteristics that affect root development

4
5–11
5 Wischmeier and Smith (1978)

For deep sandy-soils 4–6 Hudson (1995)

For deep, fertile loamy soils 13–15

For soils inflat ground in Western Nigeria 0. 05–2 Skidmore (1982); Lal (1998)

In shallow sandy-soil 4–6 ICONA (1988); Mc Cormack et al. (1982)

In sandy and clayey soil 6–8

For deep fertile clayey soils >12
5

Table III. Characteristics of study areas in Mayabeque Province

Ia Ib

Natural and anthropic conditions Pastures cultivated for forage Pastureland surface

Land area: 240 ha Land area: 320 ha

Morphometric data Altimetry: 111
10–124
00 m Altimetry: 128
10–139
50 m

Incline: 5–8% Incline: 8–10%

Prognosis of the karst morphogenesis Rapidly developing absorption dolines. Paroxysmal phase

Incipient phase in advanced stage of development

Types of dolines present Karst-suffosion, dissolution, collapse from suffosion and corrosion

This mass density was then converted to 1360 Mg m3, which adjusts better to the calculation of soil loss in millimetres (Geler, 2000) as presented in Table IV. The interpretation of the loss tolerance limits considered was as proposed by the adapted USLE model (Mc Cormack et al., 1982; Soil Survey Staff, 1984).

The forecast for loss of soil cover in linear units (mm y1) for future scenarios (25 and 50 years) was done byfitting the mean loss for 1986, 1997 and 2009 to a line using Equations 1–3, The means could be used because of the uniformity of the natural conditions in the study region, specifically, development of the karst. This ensures greater statistical stability of data,

Y¼ b0þ b1X (1) b1¼ X XY ð Þ  XX   X Y   h i =n X X2   XX 2   =n (2) b0 ¼ Ym b1Xm (3)

Where: Y is the soil loss in mm y1, X is the time in years, Xmis the mean years, Ymis the mean loss in mm y1, b1is the slope of the regression line, and b0is the y intercept.

RESULTS AND DISCUSSION

Tolerance Rates for Soil Loss from Erosion at‘Rosafé Signet’ and‘Aljibe’ in the Mampostón sub-basin

Application of the MMF model (Morgan et al., 1984; Morgan, 2001) at‘Rosafé Signet’ and ‘Boshmenier–Zenea’, for 1986, 1997 and 2009 (Table V) made it possible to confirm the development of erosion inherent to the Red Ferralitic soils called subsurface erosion.

Soil losses from karstic depressions (Table V) were found from those calculated by Vega (2006), Febles (2007) and Febles et al. (in press) by applying the MMF empirical– conceptual erosion model (Morgan et al., 1984; Morgan, 2001) in these localities considering their climatic variability and physical, physicochemical and chemical properties.

This erosion (Figure 2), which is the result of intense removal toward the karstic cavities, is strong because of the convexity of slopes with gradients facilitating runoff, such as runoff collector pits (Troeh et al. 1980; Morgan, 2001). This is among the most relevant of the geomorphic factors in fluenc-ing soil loss in the many forms of karstic absorption, mainly dolines, dynamics that corroborate the observations of Angel et al. (2004) in similar regions.

It should be mentioned that these results, found for karstic conditions in Cuba, are new and cannot be correlated directly to losses estimated in other regions of the country under differ-ent edaphoclimatic conditions.

Figure 1. Map showing the location of the main profiles at ‘Rosafé Signet’ and ‘Boshmenier–Zenea’ in Mayabeque Province, Cuba. This figure is available in colour online at wileyonlinelibrary.com/journal/ldr.

Table IV. Erosion risk in tons per hectare per year and its equivalent in millimetres per year (Geler, 2000)

Erosion risk Loss (t ha1y1) Loss (mm y1)

Very low 0–2 0–0
15

Low 2–5 0
15–0
38

Tolerable 5–10 0
38–0
77

High 10–20 0
77–1
54

For the soil loss tolerance limits not to lead to gradual deg-radation of the environment, an amount of 12
5 t ha1y1 is considered the maximum annual erosion tolerance (Mc Cormack et al., 1982; Soil Survey Staff, 1984). However, this magnitude of loss was exceeded by 50 per cent of the absorp-tion forms during the period from 1986 to 2009 (Table VI). It is interesting to note that Dolines 15 and 16, which‘recently appeared’, exceed this threshold, indicating the paroxysmal stage of the karstic process, erosion. These soil profiles have lost all or part of the surface soil horizons (the solum, horizons A and B) from erosion and a drastic reduction in their fertility,

which corroborates quantitatively the suggestions of Gallardo-Díaz et al. (1990), Romero-Gallardo-Díaz et al. (1998), Cerdá (2001) and López-Vicente and Navas (2010), in similar regions in Spain.

However, the Ferralitic soil cover can sometimes model these depressions by accumulation, masking the related action mechanism and causing to a large extent underestimation of this complex process to conclusions similar to those arrived at by Gutierrez and Rivero (1975), Busto et al. (1976), Spiridonov et al. (1976), Durán and Salinas (1986) and De Vente and Poesen (2005).

In the last 20 years, such dynamics began to undergo variations as a result of climate change (Planos, 1999), the most symptomatic expression of which is associated with the frequent hurricanes going through Mayabeque and Artemisa provinces. Among these changes are the appearance of different-sizedponors in the bottom of practically all the dolines and emergence of another two forms of absorption (Dolines 15 and 16), which were not reported in previous studies (Febles, 1988; Gonou, 1997; Vega, 2007; Febles, 2007).

In this sense, in 2003, the‘Rosafé Signet’ Center authori-ties, in an attempt to recover the soil base for pastures, dumped twenty 5- to 7-t truckloads into Doline 3, representing a volume of over 100 t (E. Lamoroux, pers. comm.).

When the study was being performed, it was observed that the doline had not been filled and that the process of solution through the ponor continues. Therefore, this practice was environmentally ineffective, as it obstructed runoff drainage channels (ponors) and was also ineffective economically.

The 25- and 50-Year Predictions of Soil Loss from Erosion As soil erosion in karsts is sometimes not obvious, determi-nation of the loss rate (t ha1y1) in mm y1 for the next 50 years was considered important to be able to see not only Table V. Soil loss in dolines applying the MMF model (Morgan

et al., 1984; Morgan, 2001) at‘Rosafé Signet’ and ‘Aljibe’ in the Mampostón sub-basin

Doline no.

Scenario 1986–2009, C1(no apparent erosion),

horizon A_{0–490 mm} Soil loss (t ha1year1)

1986 1997 2009 Mean CV (%) 1 15
957 17
820 17
649 17
227 5
97 2 17
631 16
917 20
208 18
460 9
37 3 21
357 22
128 23
613 22
554 5
08 4 14
847 14
244 14
262 14
442 2
37 5 10
011 8
355 11
910 10
345 17
19 6 9
390 9
729 10
425 9
876 5
34 7 10
686 17
142 12
042 13
894 24
50 8 12
024 10
029 12
381 11
566 10
95 9 9
012 10
143 10
668 10
142 8
34 10 10
725 11
514 12
306 11
580 6
82 11 16
068 20
226 19
419 18
885 11
67 12 13
038 13
077 14
319 13
548 5
38 13 16
653 18
120 18
816 17
970 6
14 14 10
275 11
628 13
038 11
814 11
69 15 – – 14
073 – – 16 – – 36
897 – – Mean 12
329 13
292 13
707 – –

Figure 2. (a) Fragmented limestone outcrops are evidence of karst erosion. (b) Doline exposed to stronger erosion after burning vegetation. Thisfigure is available in colour online at wileyonlinelibrary.com/journal/ldr.

current transcendence but also the perspective of this type of erosion as a strategy for adaptation to climate change.

Using the erosion risk categories proposed by Geler (2000), we show in Table VI the classification of estimated soil loss. It warns that 64–81 per cent of the dolines examined during the study period are classified as High Erosion Risk, showing sustained advance of hydric and karstic erosion acting together and synchronically, which has affected the produc-tion capacity of the soil base devoted to growing pasture grass. The mean losses in dolines for each year helped to find the regression equation (Equation 4) by which the soil losses for future scenarios were found (Table VII).

Y ¼ 14 539 þ 7:28 X R2 : 0:97 (4)

For the 2034 scenario, a mean decrease of 268
5 mm y1 is estimated for the sum of all the karst depressions studied, with the particularity that this removal of soil is by area and selective. That is, it happens at the expense of gradual wear-ing of horizon A, which by then would have lost 45
20 per cent of its original depth and would go on to be classified as C1(Moderate erosion).

During the next 25 years (2059 scenario), the loss rate will increase just under 50 per cent, and horizon A would only be 39
48-mm thick. The region will have gone into a stage of

high karstic morphogenesis, with no possibility of neigh-bouring self-morphing surfaces contributing clay sediments to the karstic depressions and ‘masking’ this complicated process as in the past.

It should be mentioned that this prediction did not take into account the inevitable process of morphometric enlargement of the karstic absorption forms, or‘dolenization’ (with marked tendency to endorheism), management practices, and changes in use of the soil cover, extreme weather events associated with climate change and so on, so soil loss magnitudes could be much more drastic and irreversible. The karstic process could therefore be reaching its paroxysmal stage and the useful land base of the agroecosystem substantially reduced, which coincides with the results found by Jaimez (2006), Wang et al. (2004) and López-Vicente et al. (2009) in similar regions.

However, several authors have seriously objected to soil loss tolerance evaluation methods based on soil formation by chemical weathering processes rate equivalents due to the lack of concrete data on their rates in these edaphization processes (e.g. in Kirkby and Morgan, 1984).

CONCLUSIONS

The mean Red Ferralitic soil loss rate modelled as pasture-land during the 1986–2009 period was 1
07 mm y1, which exceeds the thresholds for tolerance proposed by the USLE and the soil formation rates derived from limestone in Cuba. If the current trend continues, removal of 450
52 mm from horizon A is predicted for the next 50 years.

The historical-evolutionary analysis revealed that the depth of the A + B horizons must not be considered as a completely Table VI. Soil loss and associated risk according to Geler (2000)

Doline no.

Soil loss (mm y1) Erosion risk Soil loss (mm y1) Erosion risk Soil loss (mm y1) Erosion risk

1986 1997 2009

1 1
17 High 1
31 High 1
29 High

2 1
35 High 1
24 High 1
48 High

3 1
57 Very high 1
62 Very high 1
73 Very high

4 1
09 High 1
04 High 1
04 High

5 0
73 Tolerable 0
61 Tolerable 0
87 High

6 0
69 Tolerable 0
71 Tolerable 0
76 Tolerable

7 0
78 High 1
26 High 0
88 High

8 0
88 High 0
73 Tolerable 0
91 High

9 0
66 Tolerable 0
74 Tolerable 0
78 High

10 0
78 High 0
84 High 0
9 High

11 1
18 High 1
48 Tolerable 1
42 High

12 0
95 High 0
96 High 1
05 High

13 1
22 High 1
33 High 1
38 High

14 0
75 Tolerable 0
85 High 0
95 High

15 – – – – 1
03 High

16 – – – – 2
712 Very high

Mean 0
98 High 1
05 High 1
2 High

Table VII. Soil loss prediction for the next 50 years Scenario 2034, C1(Moderate erosion), horizon A0–221
50 mm Scenario 2059, C1(Severe erosion), horizon A0–39
48 mm Y (mm y1) Y (mm y1) 268
52 450
52

reliable index, inasmuch as the Red Ferralitic soils are still generally‘deep’, even when the loss tolerances reported by the specialized international literature are exceeded.

For lack of concrete experience and own data, the forecasted soil losses found for the next 50 years must be interpreted as a first estimate for designing climate change adaptation strategies in scenarios at risk in the Llanura Cársica Meridional Habana–Matanzas.

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