APPENDIX S3: Dryland Ecosystem Services

Introduction

Dryland livelihoods rely on dryland ecosystem goods and services, whose delivery is fundamentally constrained by water scarcity thereby limiting primary productivity and nutrient cycling and all deriving services [1, 2l].

Supporting Services in Drylands:

The low basal vegetation cover typically found in drylands contributes little biomass to the overall small soil organic matter (SOM) pool [3]. It also favors wind and laminar water erosion causing loss of SOM. Low SOM reduces soil fertility and the soil’s potential to retain soil moisture and mineral nutrients in the soil solution (low cation exchange capacity); this in turn triggers nutrient loss and a slowdown in soil nutrient cycling resulting in low primary production and slow plant growth. Since most global drylands are rangelands, most aboveground primary production that is consumed by livestock is recycled as milk, meet, wool, feces and urine (figure 2).

Regulating Services in Drylands

Dryland soils play an important role in climate regulation. First, they are important sinks of organic and inorganic carbon, thus, considering the wide global extension of dryland ecosystems [1], they contribute substantially to mitigating regional and global scale greenhouse gas effects on climate. Secondly, low or degraded vegetation cover changes the local energy-water balance, ultimately leading to less precipitation [4] (figure 2).

Cultural services in Drylands

Peoples living in different drylands around the world have established strong identity, connections to and knowledge of their lands and resources. Examples include the development of genuine traditional water conservation and appropriation techniques [5]. Hence, when introducing new management technologies, infrastructure, government programs (subsidies) or other incentives, or imposing new governance structures or institutions, it is fundamental to consider and integrate existing cultural connections to the land and the diversity of cultural services. Alternatively, it is important to ensure that any of these changes considers the establishment and cultivation of new connections between cultural values and innovations [6, 7] (figure 2).

Provisioning Services of Drylands

With an increasing loss in vegetation cover and infiltration of precipitation water (see above), people retain and store run-off water in earthen ponds and dams. This spatial redistribution of water favors livestock and agricultural production.

Current status of different ecosystem services in Amapola DSES

Provisioning Services - Pine oak forests dominated by Pinus cembroides provide fuel wood, construction material and piñon (pine seeds) for household use in both farming livelihood types and as rangeland for extensive livestock production. Piñon production mast years are every five years. In those years, the inhabitants of Amapola and many people from nearby San Luis Potosi collect seeds en masse, because they sell well ($10 per kg) at local markets. Pine seed harvest, deforestation and seedling herbivory on pine seedlings increasingly cause a decline in pine tree abundance (figure 4; figure S4.1).

Secondary grasslands offer forage for livestock production. High stocking rates have triggered severe land degradation and gully formation in this land cover type in the alluvial fans. Agricultural land offers diverse annual cereals and vegetable crops for farmer use and more recently for animal production. Abandoned croplands have been increasingly used to raise livestock. Gullies originating in the upper parts of the alluvial fans connect secondary grasslands with croplands which when unplanted (nine months of the year) are highly vulnerable to erosion, exacerbating the process of degradation and soil loss.

Amapola has eight surface wells, all located in communal lands and with open access and use rights by all community members. This freshwater is used as drinking water and for household use. However, a detailed analysis of water quality indicates that, though none of them was naturally enriched with or contaminated by heavy metals from mining activities, 90% of the wells were contaminated with pathogenic microbes.

Between 1960 and 2006, 16 earthen dams were constructed in the Amapola watershed area to enhance livestock production as drinking water for animals and occasionally for crop forage production. The dams were established at the base of gullies. According to detailed household surveys, 73% of the population perceive that the water level of the surface wells has decreased over the last 10 years. This is probably the consequence of an increase in runoff and a simultaneous decline in water infiltration rates and groundwater recharge.

Supporting and regulating services - Regarding variables regulating hydrological processes, soil depth in grasslands in the alluvial fans was only a third of the soil depth in the forest on rocky substrate. Active croplands had the highest soil depth with almost 0.5 m (Appendix S3; Table S3.2). Soil bulk density was significantly higher in grasslands compared to forest soils, at both soil depths. In croplands the top 15 cm were more compacted than soil at 15-30 cm. Soil depth and soil compaction affected water infiltration rate, which was three to four times greater in forest soils compared to soils of grassland and abandoned agriculture. However, in active agriculture plots, infiltration rate was almost twice as high as in forests (Appendix S3; Table S3.2). Annual surface runoff was similar in forest and active agriculture sites; however, it was two to three times higher in grasslands (Appendix S3; Table S3.2).

Table S3.1: Supporting ecosystem services: soil depth, soil organic matter (SOM), soil organic carbon (SOC), total nitrogen and potential nitrogen mineralization (slow variables) at two soil depths, associated with management and land use types in Amapola, Sierra San Miguelito.

Land use / Soil depth
(cm) / SOM
(t/ha) / SOC
(t/ha) / Total Nitrogen
(t/ha) / Potential N
mineralization rate
(mg NH4+/kg soil/day)
Pine-Oak Forest / 0-15
15-30 / 92.3±0.8a
80.6±0.96b / 54.3±6.5ª
55.7±4.7a / 3.2±0.40ª
2.9±1.2ª / 0.97±0.10
Grassland / 0-15
15-30 / 68.1±1.49c
46.4±1.33c / 13.7±0.94d
6.4±1.0e / 1.8±0.8d
1.0±0.5e / 0.20±0.06
Crop land / 0-15
15-30 / 61.6±1.05c
51.3±0.93c / 18.0±2.0c
24.4±2.1b / 2.0±1.1c
2.1±0.3c / 0.22±0.07
Abandoned crop land / 0-15
15-30 / 28.3±2.4b
19.1±1.7c / 2.5±0.9b
2.1±0.2c

Different letters indicate statistical difference among values in a column at P<0.05 (Tukey test), n=5.

Table S3.2. Regulating services: soil and vegetation characteristics influencing hydrological processes, associated with management and land use types in Amapola, Sierra San Miguelito, Mexico.

Land use / Observed soil depth (cm) / Soil bulk density
(g/cm3) / Plant cover (%) / Infiltration rate
(mm/hr) / Total annual runoff
(mm)
Pine-Oak Forest / 34 b / 0.80 ± 0.1c
0.96±0.2 c / 18.2±2.5a / 350 ± 10.8b / 33.4 b
Grassland / 19 c / 1.49±0.8 a
1.33±0.5 a / 7.2±3.5b / 95 ± 6.9c / 96.2 a
Crop land / 49 a / 1.05±0.3 b
0.93±0.12 c / Seasonal / 660 ± 15a / 36.2 b
Abandoned crop land / 24 c / annuals / 80 ± 2.4d

Different letters indicate statistical difference among values in a column at P<0.05 (Tukey test), n=5.

Table S3.3. Supporting and regulating services in two cropland types (subsidy, no-subsidy): soil depth, soil organic matter (SOM), soil organic carbon (SOC), total nitrogen, soil bulk density and potential nitrogen mineralization rate observed at two soil depths related to different crop management types (with and without subsidy).

Land use / Soil depth (cm) / SOM (t/ha) / SOC
(t/ha) / Total Nitrogen
(t/ha) / Soil bulk density
(g/cm3) / Potential N mineralization rate
(mg NH4+/kg soil/day)
Subsidy agriculture / 0-15
15-30 / 3.1 ± 0.9b
3.0 ± 0.8b / 23.2±2.1a
13.5±2.9b / 1.9±1.3a
1.5±0.4b / 1.3±0.2a
1.1±0.1b / 25.4±0.6b
No subsidy agriculture / 0-15
15-30 / 4.2 ± 1.2a
3.6 ± 0.9a / 25.5±1.7a
22.4±3.1a / 2.6±0.9a
2.0±0.2a / 1.0±0.5b
0.9±0.2b / 41.2±1.1a

Different letters among values in a column indicate statistical difference at P<0.05 (Tukey test), n=5.


REFERENCES APPENDIX S3

[1] Safreil, U. Adeel, Z. Niemeijer, D. Puigdefabregas, J. White, R. Lal, R. Winslow, M. Ziedler, J. Prince, S. Archer, E. & King, C. 2005 Dryland systems. In Ecosystems and human well-being: current state and trends (ed. R. Hassan, R. Scholes, N. Ash) Millenium Ecosystem Assessment, pp. 623-662. Island Press. Washington, D.C.

[2] Dougill, A. J. Lindsay, C. Stringer, J. L. Riddell, M. Rueff, H. Dominick, V. S. & Butt, E. Lessons from Community-based payment for ecosystem service schemes: from forest to grasslands. Phil. Trans. R. Soc. B, this issue.

[3] Lal, R. 2001 Soil carbon sequestration impacts on global climate change and food security. Science 304, 1623-1627.

[4] Bonan, G. B. 2008 Ecological climatology: principles and applications. 2nd edition. Cambridge University Press.

[5] Food and Agriculture Organization (FAO). 2009 Livestock keepers – guardians of biodiversity. Animal Production and Health Paper. No. 167. Rome

[6] Chapin III, F. S., Folke, C. & Kofinas, G. P. 2009 A framework for understanding change. In Principles of ecosystem stewardship (ed. F.S. Chapin, III, Kofinas, G.P. & Folke, C.), pp 3-28. Springer, New York, N.Y.

[7] Berkes, F. Kofinas, G. O. & Stuart Chapin, F.S. III. 2009 Conservation, community, and livelihoods: sustaining, renewing, and adapting cultural connections to the land. In Principles of Ecosystem Stewardship (ed. F.S. Chapin III, G.P. Kofinas, C. Folke,), pp 129-147. Springer, New York, N.Y.