Comparative assessment of goods and services provided by grazing regulation and reforestation in degraded Mediterranean rangelands

Several management actions are applied to restore ecosystem services in degraded Mediterranean rangelands, which range from adjusting the grazing pressure to the removal of grazers and pine plantations. Four such actions were assessed in Quercus coccifera L. shrublands in northern Greece: (i) moderate grazing by goats and sheep; (ii) no grazing; (iii) no grazing plus pine (Pinus pinaster Aiton) plantation in forest gaps (gap reforestation); and (iv) no grazing plus full reforestation of shrubland areas, also with P. pinaster. In addition, heavy grazing was also assessed to serve as a control action. We comparatively assessed the impact of these actions on key provisioning, regulating and supporting ecosystem services by using ground‐based indicators. Depending on the ecosystem service considered, the management actions were ranked differently. However, the overall provision of services was particularly favoured under moderate and no grazing management options, with moderate grazing outranking any other action in provisioning services and the no grazing action presenting the most balanced provision of services. Pine reforestations largely contributed to water and soil conservation and C sequestration but had a negative impact on plant diversity when implemented at the expense of removing natural vegetation in the area. Heavy grazing had the lowest provision of ecosystem services. It is concluded that degraded rangelands can be restored by moderating the grazing pressure rather than completely banning livestock grazing or converting them into pine plantations

Agroforestry

Agroforestry is the practice of deliberately integrating woody vegetation (trees or shrubs) with crops and/or animal systems to benefit from the resulting ecological and economic interactions. Existing research indicates that appropriate application of agroforestry principles and practices is a key means by which the European Union might achieve more sustainable methods of food and fibre production whilst producing both profits for farmers and environmental benefits for society

Long term evolution of tree growth, understorey vegetation and soil properties in a silvopastoral system of northern Greece

Tree growth, understorey characteristics and soil parameters were evaluated in a silvopastoral system in northern Greece at seven and twelve years after its establishment. The experiment was laid out in 1992 and included three understorey treatments (grass, legume and control- unsown), two tree species - sycamore (Acer pseudoplatanus L.) and Scots pine (Pinus sylvestris L.) and two tree spacings (2.5 x 2.5 m and 3.5 x 3.5 m). Tree height was taller in the control and in the dense stands while Scots pine had better growth but, higher mortality than sycamore in the both periods. In 2004, understorey vegetation was uniform under the three understorey treatments and a significant decrease in sward above ground biomass was recorded under the dense treatment, compared with the open stand. In the same year, organic C and N, Mg and K concentrations as well as arbuscular mycorrhizal fungi spore numbers were found significantly higher under sycamore than Scots pine plots in the 0-20 cm soil depth. The results show that, although understorey vegetation became uniform over time, the initial plant composition of the understorey treatments continued to affect tree growth, indicating the importance of the understorey vegetation at the establishment stage of silvopastoral systems. However, as time passed initial tree spacing started to affect tree growth and tree species, particularly sycamore to improve soil properties. These results indicate an evolution of the initial silvopastoral system to a forest.</p

Change in plant spatial patterns and diversity along the successional gradient of Mediterranean grazing ecosystems

In this study, we analyze the complexity of plant spatial patterns and diversity along a successional gradient resulting from grazing disturbance in four characteristic ecosystems of the Mediterranean region. Grazing disturbance include not only defoliation by animals, but also associated disturbances as animal trampling, soil compaction, and mineralization by deposition of urine and feces. The results show that woodland and dense matorral are more resistant to species loss than middle dense and scattered matorral, or grassland. Information fractal dimension declined as we moved from a dense to a discontinuous matorral, increasing as we moved to a more scattered matorral and a grassland. In all studied cases, the characteristic species of the natural vegetation declined in frequency and organization with grazing disturbance. Heliophyllous species and others with postrate or rosette twigs increased with grazing pressure, particularly in dense matorral. In the more degraded ecosystem, only species with well-adapted traits, e.g., buried buds or unpalatable qualities showed a clear increase with grazing. Indeed, the homogeneity of species distribution within the plant community declined monotonically with grazing impact. Conversely, the spatial organization of the characteristic plants of each community increased in the better-preserved areas, being also related to the sensitivity of the species to grazing impact. The degree of autocorrelation of plant spatial distribution at the species level and the information fractal dimension at the community level allow us to quantify the degree of degradation of natural communities and to determine the sensitivity of key species to disturbance. © 2004 Elsevier B.V. All rights reserved.Comisión Interministerial de Ciencia y Tecnología: AMB1998-1017 European Commission: ERBIC18-CT98-0392The work was performed under the DRASME (Desertification Risk Assessment in Silvopastoral Mediterranean Ecosystems) collaborative research project and CICYT (Evaluación de la presión ganadera para la conservación de las estepas y matorrales Mediterráneos, project number AMB1998-1017). DRASME is funded by the EC under its INCO-DC programme, contract number ERBIC18-CT98-0392. The support from both programs is gratefully acknowledged. We are grateful to John Emlen, Carl Freeman and Bai-Lian Li for critically reading and helpful suggestions on the manuscript. Software for data analysis was developed by Juan Escós. Appendix

Spatial vegetation patterns and imminent desertification in Mediterranean arid ecosystems

Humans and climate affect ecosystems and their services(1), which may involve continuous and discontinuous transitions from one stable state to another(2). Discontinuous transitions are abrupt, irreversible and among the most catastrophic changes of ecosystems identified(1). For terrestrial ecosystems, it has been hypothesized that vegetation patchiness could be used as a signature of imminent transitions(3,4). Here, we analyse how vegetation patchiness changes in arid ecosystems with different grazing pressures, using both field data and a modelling approach. In the modelling approach, we extrapolated our analysis to even higher grazing pressures to investigate the vegetation patchiness when desertification is imminent. In three arid Mediterranean ecosystems in Spain, Greece and Morocco, we found that the patch-size distribution of the vegetation follows a power law. Using a stochastic cellular automaton model, we show that local positive interactions among plants can explain such power-law distributions. Furthermore, with increasing grazing pressure, the field data revealed consistent deviations from power laws. Increased grazing pressure leads to similar deviations in the model. When grazing was further increased in the model, we found that these deviations always and only occurred close to transition to desert, independent of the type of transition, and regardless of the vegetation cover. Therefore, we propose that patch-size distributions may be a warning signal for the onset of desertification

Comparative assessment of goods and services provided by grazing regulation and reforestation in degraded Mediterranean rangelands

Several management actions are applied to restore ecosystem services in degraded Mediterranean rangelands, which range from adjusting the grazing pressure to the removal of grazers and pine plantations. Four such actions were assessed in Quercus coccifera L. shrublands in northern Greece: (i) moderate grazing by goats and sheep; (ii) no grazing; (iii) no grazing plus pine (Pinus pinaster Aiton) plantation in forest gaps (gap reforestation); and (iv) no grazing plus full reforestation of shrubland areas, also with P. pinaster. In addition, heavy grazing was also assessed to serve as a control action. We comparatively assessed the impact of these actions on key provisioning, regulating and supporting ecosystem services by using ground‐based indicators. Depending on the ecosystem service considered, the management actions were ranked differently. However, the overall provision of services was particularly favoured under moderate and no grazing management options, with moderate grazing outranking any other action in provisioning services and the no grazing action presenting the most balanced provision of services. Pine reforestations largely contributed to water and soil conservation and C sequestration but had a negative impact on plant diversity when implemented at the expense of removing natural vegetation in the area. Heavy grazing had the lowest provision of ecosystem services. It is concluded that degraded rangelands can be restored by moderating the grazing pressure rather than completely banning livestock grazing or converting them into pine plantations

Productivity and canopy modification of Medicago arborea as affected by defoliation management and genotype in a Mediterranean environment

Medicago arborea is one of the most potentially valuable fodder shrubs in a Mediterranean environment because of its high preference by small ruminants and its nutritive value. Edible biomass production is affected by agronomic and environmental factors. A study, carried out in an inland area of Sicily in the growing seasons of 1994/95, 1995/96 and 1996/97, evaluated the forage production and canopy modification in a M. arborea plantation after (i) commencing defoliation 1 or 2 years after transplanting and (ii) defoliating only in autumn (A), only in early summer (S) or in both seasons (A and S). Six clones derived from five different Mediterranean populations were used. Plant age at the first defoliation did not significantly influence forage production. The genotypes differed in growth rate and forage production. The season and frequency of defoliation markedly influenced forage production and canopy size. The highest annual production was obtained by defoliating once a year in early summer (on average, 1Æ65, 2Æ85 and 4Æ50 tonnes ha)1 respectively in the three growing seasons). With the A and S, and A defoliation treatments, production decreased over 3 years by, on average, 0Æ19 and 0Æ57 respectively, but the differences became more marked over a 3-year period. Defoliating only in early summer, however, resulted in an excessive shrub height (>120 cm, 3 years after transplanting), thereby increasing problems of accessibility to small grazing ruminants, and possibly necessitating cutting. On the contrary, the A and S defoliation made it possible to limit the height to <90 cm