Noelia Garcia Franco | Universidad de Murcia (original) (raw)

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Papers by Noelia Garcia Franco

Research paper thumbnail of Carbon dynamics after afforestation of semiarid shrublands: Implications of site preparation techniques

Climate change is a potential threat to soil organic carbon (SOC) in semiarid ecosystems. Several... more Climate change is a potential threat to soil organic carbon (SOC) in semiarid ecosystems. Several studies advocated afforestation as an important way to achieve soil C accumulation, but few deal with the mechanisms of C stabilization. The knowledge of these mechanisms is a key aspect in the preservation of SOC in the face of climate change. In a long-term experiment in southeast Spain, we analyzed the effect on C
sequestration and stabilization mechanisms of two Pinus halepensis afforestation treatments: (a) terracing (T) and (b) terracing with soil amendment (AT). Twenty years after installing the pine plantations, changes were measured in: (a) chemical, physical, and biological soil properties, (b) ecosystem C stocks, and (c) three functional SOC pools: particulate organic matter (POM), sand and stable aggregates (S+A), and silt plus clay (S+C). The results show that the afforestation treatment had a distinct impact on soil
properties. Compared with the adjacent native shrubland, the AT treatment led to improved soil fertility, while the T treatment had a negative impact on soil properties. In turn, AT led to a C gain in the ecosystem of 1.3 kg C m�2, while with T there was a decline of 0.60 kg C m�2 over 20 years. This decline was due to the impact of the terracing work. The potential ecosystem C sequestration capacity of the afforestation was 160 and 65 g C m�2 year�1 in AT and T, respectively. Focusing on sequestration in the mineral soil, the average annual sequestration rate was 28 g C m�2 year�1 in AT and 17 g C m�2 year�1 in T. In relation to the functional SOC pools, the C sequestered showed the following distribution: 30% POM, 46% (S+A), and 24% (S+C). The results show that C sequestration, through afforestation of semiarid areas, can be increased by using suitable afforestation techniques. Site preparation involving large soil disturbance
is not recommended. Twenty years after planting, the potential capacity for C sequestration of the afforested ecosystems is far from being saturated and they will continue sequestering C as they reach maturity.

Research paper thumbnail of Sustainable land management practices as providers of several ecosystem services under rainfed Mediterranean agroecosystems

Little is known about the multiple impacts of sustainable land management practices on soil and w... more Little is known about the multiple impacts of sustainable land management practices on soil and water conservation, carbon sequestration, mitigation of global change and crop yield productivity in semiarid Mediterranean agroecosystems. We hypothesized that a shift from intensive tillage to more conservative tillage management practices (reduced tillage optionally combined with green manure) leads to an improvement in soil structure and quality and will reduce soil erosion and enhance carbon sequestration in semiarid Mediterranean rainfed agroecosystems. To test the hypothesis, we assessed the effects of different tillage
treatments (conventional (CT), reduced (RT), reduced tillage combined with green manure (RTG), and no tillage (NT)) on soil structure and soil water content, runoff and erosion control, soil carbon dioxide (CO2) emissions, crop yield and carbon sequestration in two semiarid agroecosystems with organic rainfed almond (Prunus dulcis Mill) in the Murcia Region (southeast Spain). It was found that reduction and suppression of tillage under almonds led to an increase in soil water content in both agroecosystems. Crop yields ranged from 775 to 1,766 kg ha−1 between tillage treatments, but we did not find a clear relation between soil water
content and crop yield. RT and RTG treatments showed lower soil erosion rates and higher crop yields of almonds than under CT treatment. Overall, higher soil organic carbon contents and aggregate stability were observed under RTG treatment than under RT or CT treatment. It is concluded that conversion from CT to RTG is suitable to increase carbon inputs without enhancing soil CO2 emissions in semiarid Mediterranean agroecosystems.
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Research paper thumbnail of Changes in soil aggregation and microbial community structure control carbon sequestration after afforestation of semiarid shrublands

Changes in plant cover after afforestation induce variations in litter inputs and soil microbial ... more Changes in plant cover after afforestation induce variations in litter inputs and soil microbial community structure and activity, which may promote the accrual and physical-chemical protection of soil organic carbon (SOC) within soil aggregates. In a long-term experiment (20 years) we have studied the effects, on soil aggregation and SOC stabilization, of two afforestation techniques: a) amended terraces with organic refuse (AT), and b) terraces without organic amendment (T). We used the adjacent shrubland (S) as control. Twenty years after stand establishment, aggregate distribution (including microaggregates within larger aggregates), sensitive and slow organic carbon (OC) fractions, basal respiration in macroaggregates, and microbial community structure were measured. The main changes occurred in the top layer (0–5 cm), where: i) both the sensitive and slow OC fractions were increased in AT compared to S and T, ii) the percentage and OC content of microaggregates within macroaggregates (Mm) were higher in AT than in S and T, iii) basal respiration in macroaggregates was also higher in AT, and iv) significant changes in the fungal (rather than bacterial) community structure were observed in the afforested soils (AT and T) – compared to the shrubland soil. These results suggest that the increase in OC pools linked to the changes in microbial activity and fungal community structure, after afforestation, promoted the formation of macroaggregates – which acted as the nucleus for the formation and stabilization of OC-enriched microaggregates.

Research paper thumbnail of Beneficial effects of reduced tillage and green manure on soil aggregation and stabilization of organic carbon in a Mediterranean agroecosystem

Abstract Keywords: Rain-fed almond orchard Sustainable land management Semiarid agroecosystems S... more Abstract

Keywords: Rain-fed almond orchard Sustainable land management Semiarid agroecosystems Soil organic carbon fractionation Carbon sequestration Soil aggregation A B S T R A C T Semiarid Mediterranean agroecosystems need the implementation of sustainable land management (SLM) practices in order to maintain acceptable levels of soil organic matter (SOM). The application of SLM practices helps to maintain soil structure and physical-chemical protection of soil organic carbon (SOC), hence improving soil carbon sequestration and mitigating CO 2 emissions to the atmosphere. In an organic, rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard under reduced tillage (RT), as the habitual management practice during the 14 years immediately preceding the experiment, we studied the effect of two agricultural management practices on soil aggregate distribution and SOC stabilization after four years of implementation. The implemented practices were (1) reduced tillage with a mix of Vicia sativa L. and Avena sativa L. as green manure (RTG) and (2) no-tillage (NT). Four aggregate size classes were differentiated by wet sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, three organic C fractions were separated within the small macroaggregates and micro-aggregates, using a density fractionation method: free light fraction (free LF-C), intra-aggregate particulate OM (iPOM-C), and organic C associated with the mineral fraction (mineral-C). The results show that the combination of reduced tillage plus green manure (RTG) was the most-efficient SLM practice for SOC sequestration. The total SOC increased by about 14% in the surface layer (0–5 cm depth) when compared to RT. Furthermore, green manure counteracted the effect of tillage on soil aggregate rupture. The plant residue inputs from green manure and their incorporation into the soil by reduced tillage promoted the formation of new aggregates and activated the subsequent physical-chemical protection of OC. The latter mechanism occurred mainly in the fine iPOM-C occluded within microaggregates and mineral-C occluded within small macroaggregates fractions, which together contributed to an increase of up to 30% in the OC concentration in the bulk soil. No-tillage favored the OC accumulation in the mineral-C within the small macroaggregates and in the fine iPOM-C occluded within microaggregates in the surface layer, and in the mineral-C occluded within the small macroaggregates and microaggregates at 5–15 cm depth, but four years of cessation of tillage were not enough to significantly increase the total OC in the bulk soil.

Research paper thumbnail of Carbon dynamics after afforestation of semiarid shrublands: Implications of site preparation techniques

Climate change is a potential threat to soil organic carbon (SOC) in semiarid ecosystems. Several... more Climate change is a potential threat to soil organic carbon (SOC) in semiarid ecosystems. Several studies advocated afforestation as an important way to achieve soil C accumulation, but few deal with the mechanisms of C stabilization. The knowledge of these mechanisms is a key aspect in the preservation of SOC in the face of climate change. In a long-term experiment in southeast Spain, we analyzed the effect on C
sequestration and stabilization mechanisms of two Pinus halepensis afforestation treatments: (a) terracing (T) and (b) terracing with soil amendment (AT). Twenty years after installing the pine plantations, changes were measured in: (a) chemical, physical, and biological soil properties, (b) ecosystem C stocks, and (c) three functional SOC pools: particulate organic matter (POM), sand and stable aggregates (S+A), and silt plus clay (S+C). The results show that the afforestation treatment had a distinct impact on soil
properties. Compared with the adjacent native shrubland, the AT treatment led to improved soil fertility, while the T treatment had a negative impact on soil properties. In turn, AT led to a C gain in the ecosystem of 1.3 kg C m�2, while with T there was a decline of 0.60 kg C m�2 over 20 years. This decline was due to the impact of the terracing work. The potential ecosystem C sequestration capacity of the afforestation was 160 and 65 g C m�2 year�1 in AT and T, respectively. Focusing on sequestration in the mineral soil, the average annual sequestration rate was 28 g C m�2 year�1 in AT and 17 g C m�2 year�1 in T. In relation to the functional SOC pools, the C sequestered showed the following distribution: 30% POM, 46% (S+A), and 24% (S+C). The results show that C sequestration, through afforestation of semiarid areas, can be increased by using suitable afforestation techniques. Site preparation involving large soil disturbance
is not recommended. Twenty years after planting, the potential capacity for C sequestration of the afforested ecosystems is far from being saturated and they will continue sequestering C as they reach maturity.

Research paper thumbnail of Sustainable land management practices as providers of several ecosystem services under rainfed Mediterranean agroecosystems

Little is known about the multiple impacts of sustainable land management practices on soil and w... more Little is known about the multiple impacts of sustainable land management practices on soil and water conservation, carbon sequestration, mitigation of global change and crop yield productivity in semiarid Mediterranean agroecosystems. We hypothesized that a shift from intensive tillage to more conservative tillage management practices (reduced tillage optionally combined with green manure) leads to an improvement in soil structure and quality and will reduce soil erosion and enhance carbon sequestration in semiarid Mediterranean rainfed agroecosystems. To test the hypothesis, we assessed the effects of different tillage
treatments (conventional (CT), reduced (RT), reduced tillage combined with green manure (RTG), and no tillage (NT)) on soil structure and soil water content, runoff and erosion control, soil carbon dioxide (CO2) emissions, crop yield and carbon sequestration in two semiarid agroecosystems with organic rainfed almond (Prunus dulcis Mill) in the Murcia Region (southeast Spain). It was found that reduction and suppression of tillage under almonds led to an increase in soil water content in both agroecosystems. Crop yields ranged from 775 to 1,766 kg ha−1 between tillage treatments, but we did not find a clear relation between soil water
content and crop yield. RT and RTG treatments showed lower soil erosion rates and higher crop yields of almonds than under CT treatment. Overall, higher soil organic carbon contents and aggregate stability were observed under RTG treatment than under RT or CT treatment. It is concluded that conversion from CT to RTG is suitable to increase carbon inputs without enhancing soil CO2 emissions in semiarid Mediterranean agroecosystems.
PAGE 1

Research paper thumbnail of Changes in soil aggregation and microbial community structure control carbon sequestration after afforestation of semiarid shrublands

Changes in plant cover after afforestation induce variations in litter inputs and soil microbial ... more Changes in plant cover after afforestation induce variations in litter inputs and soil microbial community structure and activity, which may promote the accrual and physical-chemical protection of soil organic carbon (SOC) within soil aggregates. In a long-term experiment (20 years) we have studied the effects, on soil aggregation and SOC stabilization, of two afforestation techniques: a) amended terraces with organic refuse (AT), and b) terraces without organic amendment (T). We used the adjacent shrubland (S) as control. Twenty years after stand establishment, aggregate distribution (including microaggregates within larger aggregates), sensitive and slow organic carbon (OC) fractions, basal respiration in macroaggregates, and microbial community structure were measured. The main changes occurred in the top layer (0–5 cm), where: i) both the sensitive and slow OC fractions were increased in AT compared to S and T, ii) the percentage and OC content of microaggregates within macroaggregates (Mm) were higher in AT than in S and T, iii) basal respiration in macroaggregates was also higher in AT, and iv) significant changes in the fungal (rather than bacterial) community structure were observed in the afforested soils (AT and T) – compared to the shrubland soil. These results suggest that the increase in OC pools linked to the changes in microbial activity and fungal community structure, after afforestation, promoted the formation of macroaggregates – which acted as the nucleus for the formation and stabilization of OC-enriched microaggregates.

Research paper thumbnail of Beneficial effects of reduced tillage and green manure on soil aggregation and stabilization of organic carbon in a Mediterranean agroecosystem

Abstract Keywords: Rain-fed almond orchard Sustainable land management Semiarid agroecosystems S... more Abstract

Keywords: Rain-fed almond orchard Sustainable land management Semiarid agroecosystems Soil organic carbon fractionation Carbon sequestration Soil aggregation A B S T R A C T Semiarid Mediterranean agroecosystems need the implementation of sustainable land management (SLM) practices in order to maintain acceptable levels of soil organic matter (SOM). The application of SLM practices helps to maintain soil structure and physical-chemical protection of soil organic carbon (SOC), hence improving soil carbon sequestration and mitigating CO 2 emissions to the atmosphere. In an organic, rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard under reduced tillage (RT), as the habitual management practice during the 14 years immediately preceding the experiment, we studied the effect of two agricultural management practices on soil aggregate distribution and SOC stabilization after four years of implementation. The implemented practices were (1) reduced tillage with a mix of Vicia sativa L. and Avena sativa L. as green manure (RTG) and (2) no-tillage (NT). Four aggregate size classes were differentiated by wet sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, three organic C fractions were separated within the small macroaggregates and micro-aggregates, using a density fractionation method: free light fraction (free LF-C), intra-aggregate particulate OM (iPOM-C), and organic C associated with the mineral fraction (mineral-C). The results show that the combination of reduced tillage plus green manure (RTG) was the most-efficient SLM practice for SOC sequestration. The total SOC increased by about 14% in the surface layer (0–5 cm depth) when compared to RT. Furthermore, green manure counteracted the effect of tillage on soil aggregate rupture. The plant residue inputs from green manure and their incorporation into the soil by reduced tillage promoted the formation of new aggregates and activated the subsequent physical-chemical protection of OC. The latter mechanism occurred mainly in the fine iPOM-C occluded within microaggregates and mineral-C occluded within small macroaggregates fractions, which together contributed to an increase of up to 30% in the OC concentration in the bulk soil. No-tillage favored the OC accumulation in the mineral-C within the small macroaggregates and in the fine iPOM-C occluded within microaggregates in the surface layer, and in the mineral-C occluded within the small macroaggregates and microaggregates at 5–15 cm depth, but four years of cessation of tillage were not enough to significantly increase the total OC in the bulk soil.