Ancient forests are known to host a biodiversity of high ecological distinctiveness and are likely to provide habitat for red-listed species. Yet, few studies have investigated the role of forest ...continuity for the conservation of threatened species. We used species-presence data on red-listed species from 12 taxonomic groups (Spermatophyta, Pteridophyta, Bryophyta, Lichens, Chiroptera, Aves, Squamata, Amphibia, Coleoptera, Lepidoptera, Odonata and Orthoptera) to ascertain if ancient forests are an important habitat for threatened species in five mountain and subalpine protected areas in France. We compared the effect of the amount of historical forest (1853–1860) with the effect of the amount of current forest on the distribution of red-listed species in six circular landscape buffers ranging in radius from 100 to 1500 m. We showed that the amount of historical forest in the landscape had a positive effect on forest Spermatophyta, Bryophyta, Coleoptera and edge forest Pteridophyta with a better predictive power than current forest area, highlighting a colonization credit in recent forests. Conversely, edge-forest lepidopterans were more negatively affected by historical than by current forest area, highlighting an extinction debt in recent forests. Our findings underline that implementing protective measures of ancient forests would be a better strategy than afforestation to preserve threatened forest species in mountain and subalpine forest landscapes.
Abstract
Key message
Metabarcoding analysis of soil fungal communities in French mountain forests revealed that harvesting intensity, time since last harvest and former land use had no effect on ...fungal community composition compared to key abiotic factors. Low-intensity management in these uneven-aged mountain forests therefore has limited effects on soil fungal community composition which is mainly driven by elevation and edaphic properties.
Context
Past and current human activities are known to affect forest biodiversity. However, the effects of former land use and forest management have been studied much more extensively on higher plants than on fungi.
Aims
Our objectives were to assess the effects of harvesting intensity, duration since last harvest and former land use on soil fungal communities in uneven-aged mountain high forests.
Methods
On the basis of historical land-use maps drawn between 1862 and 1864 and on historical forest management archives, we selected 62 sites in the French Alps with contrasting land-use histories (ancient forests, which were already forested on historical maps
vs
recent forests, which have recovered following abandonment of pastures) and different durations since last harvest (from 1 to over 50 years). We carried out soil sampling and assessed fungal diversity by metabarcoding analysis. We analysed soil fungal molecular operational taxonomic units (MOTU) diversity as a whole and for the main lifestyle groups (such as wood saprotrophic or ectomycorrhizal fungi) using multiple linear regressions on Shannon’s diversity index and fungal taxonomic composition using canonical correlation analysis.
Results
We found no significant effect of harvesting intensity, time since last harvest or land-use history on total fungal MOTU diversity, fungal lifestyle diversity or taxonomic composition. In contrast, we observed significant effects of elevation, pH, organic carbon and available phosphorus content on the taxonomic and functional composition of soil fungal communities.
Conclusions
The structure of soil fungal communities (i.e. diversity and species composition) was mainly determined by elevation and edaphic factors, indicating a high-context dependency, as previously found in similar studies. Our study in mountain forests shows that recent forests established on former pastures had no legacy effect on soil conditions and fungal communities, in contrast to previous results in lowland areas, where recent forests were mainly established on former cropland. Uneven-aged forest management had no effect on fungal diversity, in contrast to previous results observed in even-aged high forests.
Question
Differences in understorey vegetation between ancient and recent forests have been thoroughly explored; however, few studies have investigated the legacies of different former land uses in ...recent forests. Indeed, due to more intense agricultural practices (tillage and fertilisation), legacy effects are expected to be stronger in former cropland or meadows than in former pastures. Our objectives were to compare soil conditions, taxonomic composition and functional composition of understorey plant communities in recent forests located on former pastures, meadows or cropland, with ancient forests as a reference.
Location
Tarentaise Valley, Savoy, France.
Methods
Based on land‐use maps surveyed between 1862 and 1864, we selected 82 forest sites with different former land uses in mountain forests in the French Alps and carried out soil sampling and botanical surveys. To account for potential confounding factors (altitude, canopy cover, tree species composition), we applied multiple linear regressions to analyse soil properties, canonical correspondence analysis to analyse plant taxonomic composition and multispecies generalised linear mixed‐effects models to analyse relationships between plant functional composition and former land uses.
Results
The soils of former cropland were richer in nutrients and more alkaline compared to other past land uses, while soils on former pastures and meadows differed only slightly from ancient forests. Ancient forests were characterised by acidophilic, shade‐tolerant, low‐stature, forest‐dependent species, whereas former cropland was characterised by calcicolous non‐forest species. Former pasture and meadow communities displayed a distinct taxonomic composition compared to other past land uses, but a functional composition closer to ancient forest than to former cropland.
Conclusion
Former cropland has a stronger legacy effect than former pastures or meadows. This could explain small differences between ancient and recent forests observed in previous studies conducted in mountain landscapes where former cropland was rare.
The analyses of soils and understorey plant communities in French mountain forests with different past land uses (forest, pasture, meadow or cropland in the mid‐19th century) revealed that the legacy effects of past agricultural activities on current soil conditions and plant communities are stronger in former croplands than in former pastures or meadows.
Global biogeochemical cycles have been deeply modified by human activities in recent decades. But detailed studies analyzing the influence of current economic and social organizations on global ...biogeochemical cycles within a system perspective are still required. Country level offers a relevant scale for assessing nutrient management and identifying key driving forces and possible leaks in the nutrient cycle. Conceptual modeling helps to quantify nutrient flows within the country and we developed such an approach for France. France is a typical Western European country with intensive agriculture, trade and an affluent diet, all of which may increase internal and external P flows. Phosphorus (P) was taken as a case study because phosphate rock is a non‐renewable resource which future availability is becoming increasingly bleak. A conceptual model of major P flows at the country scale was designed. France was divided into agriculture, industry, domestic, import and export sectors, and each of these sectors was further divided into compartments. A total of 25 internal and eight external P flows were identified and quantified on a yearly basis for a period of 16 years (from 1990 to 2006) in order to understand long‐term P flows. All the P flows were quantified using the substance flow analysis principle. The results showed that the industrial sector remained the largest contributor to P flows in France, followed by the agriculture and domestic sectors. Soil P balance was positive. However, a positive P balance of 18 kg P ha−1 in 1990 was reduced to 4 kg P ha−1 in 2006, mainly due to the reduced application of inorganic P fertilizer. The overall country scale P balance was positive, whereas half of this additional P was lost to the environment mainly through the landfilling of municipal and industrial waste, disposal of treated wastewater from which P was partially removed, and P losses from agricultural soils though erosion and leaching. Consequences for global P resources and soil and water compartments are discussed. Some opportunities to more effectively close the P cycle in France by both improving the intensity of P recycling and decreasing losses are quantified.
Key Points
French soil P balance reduced from 18 kg per ha in 1990 to 4 kg per ha in 2006
The ratio between national soil P input and P in food products was only 10%
Half of the net P import in France was lost to the environment
Adequate phosphorus (P) nutritiion during early stages is critical for maize growth. Our objective was to evaluate the relative contribution of seed P reserves and exogenous P to maize nutrition ...during early growth stages. Seedlings were grown with labeled nutrient solution (32P). Seedlings were harvested periodically over the course of the three-week study. Initially, 87% and 77% of the total C and N in seeds were located in the endosperm, whereas 86% of seed P was located in the scutellum as phytate. Up to the 7th day after sowing, 96% of phytate was hydrolyzed. Hydrolyzed forms of P were temporarily stored in the seed before being translocated to growing organs, suggesting that the hydrolysis of phytate was not a limiting step for P supply to seedlings. Significant P uptake by roots was observed from the 5th day after sowing on. Both sources of P supplied roots and leaves, with a slightly higher proportion of P from seed reserves going to leaves rather than to roots. Of total seed P, 60% and 92% was exported toward newly growing seedlings till 7th and 17th days after sowing and ceased to be a significant source of P for growth thereafter. We conclude that although both P supply processes overlap in time, seed P was the main P source during early growth stages.
Large-scale studies at the regional, national and global scales are increasingly needed to assess nutrient flows in agroecoystems and to identify their drivers. In this study, we aimed to quantify ...the extent to which regional phosphorus (P) flows and soil P budget depend on agricultural production systems. Phosphorus was taken as a case study due to its sorbing properties in soil and to the many questions concerning its future availability. The issue was studied from two different stages: (1) for the 21 administrative regions of France; and (2) by selecting four contrasting French regions—the Centre region (a crop farming region), Brittany (an animal farming region) and Lorraine and Aquitaine (mixed farming regions). Phosphorus flows and soil P budgets were quantified on a yearly basis for the 21 regions from 1990 to 2006, whereas a 5-year average was calculated for the years 2002–2006 to compare the four selected regions. At the beginning of the study (1990), the calculated P budget was positive for all regions averaging 17.5 kg P ha
−1
year
−1
which declined over years to 4.4 kg P ha
−1
year
−1
in 2006, but huge differences between the 21 regions were observed, confirming the heterogeneity of the regional P flows. Agricultural production systems strongly influenced the P flows through feed, fodder and animal excretion, while P fertiliser consumption was only partially influenced. As a consequence, both the regional soil P budgets and the magnitude of soil P inflows and outflows were strongly dependent on the regional agricultural production systems. A balanced soil P budget could be obtained in crop farming regions, but it strongly relied on P fertiliser use. The animal farming regions continued to accumulate P in the soil, and further use of P fertilisers in these regions is questionable. Finally, there was no simple rule between the mixed farming systems and the soil P budget. This study offers some initial elements for understanding the drivers of mineral P fertiliser use, i.e. the factors governing P fertiliser use by the farmers. It may also contribute to the redesign of regional farming systems oriented towards more effective use of nutrients at the global scale.
•Crop–livestock segregation fosters mineral fertiliser use at the local scale.•Mineral fertiliser use decreases when stocking rate increases at the local scale.•Mineral fertiliser substitution with ...animal manure plateaus for high stocking rate.•We confirmed the benefits of mixed farming systems for resource conservation.
The integration of crops and animals is an option to reduce mineral fertiliser use through the recycling of nutrients in animal manure on croplands. But the increasing specialisation and spatial segregation of crop and livestock production systems both at the farm and the district scale may hamper the proper recycling of nutrients between these two activities. However, the effect of such segregation has only been investigated on some case-studies – mostly at the regional and the local scale – while we still lack of systematic assessment of this segregation in terms of mineral fertiliser use on a range of scales. In this paper, we estimated the effect of this segregation on nutrient resource use at the district scale. Phosphorus (P) fertiliser was considered since it is produced from a finite resource that needs to be more efficiently recycled in agriculture and France was chosen as a case study, representative of industrial countries with a wide range of variations in crop and livestock segregation. We quantified the effect of livestock density on mineral P fertiliser use and the effect of crop and livestock spatial segregation on P fertiliser use and its substitution with P in animal manure. Our results showed that P fertiliser use decreased with increasing livestock density at the district scale. However, the substitution of P fertiliser with P in animal manure was only partial (probably due to more N- than P-oriented decision making by farmers and low N:P ratio of organic manure), leading to large nutrient surpluses in districts with high livestock densities (>1.1 livestock unit per agricultural area). Finally, P fertiliser use increased with the spatial segregation of crops and livestock. Overall, our results demonstrated that lower segregation of crops and animals could help to save non-renewable resources, and that improvements in manure management are required.
•P flows and P recycling efficiencies along the waste systems quantified for France.•P recovery was high from most waste systems but the P recycling efficiency was low.•Overall, the P recycling ...efficiency from waste was 51% in France.•Options exist for improving P recycling but they appear to be less promising.•Reducing food waste and redesigning agricultural systems could economize P use.
Phosphate rocks, used for phosphorus (P) fertilizer production, are a non-renewable resource at the human time scale. Their depletion at the global scale may threaten global food and feed security. To prevent this depletion, improved P resource recycling from food chain waste to agricultural soils and to the food and feed industry is often presented as a serious option. However, waste streams are often complex and their recycling efficiency is poorly characterized. The aim of this paper is to estimate the P recovery and recycling potential from waste, considering France as a case study. We assessed the P flows in food processing waste, household wastewater and municipal waste at the country scale using a substance flow analysis for the year 2006. We also quantified the P recycling efficiency as the fraction of P in waste that ultimately reached agricultural soils or was recycled in the food and feed industry. Efforts were made to limit data uncertainty by cross-checking multiple data sources concerning P content in waste materials. Results showed that, in general, P recovery in waste was high but that the overall P recycling efficiency was only 51% at the country scale. In particular, P recycling efficiency was 75% for industrial waste, 43% for household wastewater and 47% for municipal waste. The remaining P was discharged into water bodies or landfilled, causing P-induced environmental problems as well as losses of nutrient resources. Major P losses were through food waste (which amounted to 39% of P in available food) and treated wastewater, and the findings were confirmed through cross-checking with alternative data sources. Options for improving P resource recycling and, thereby, reducing P fertilizer use were quantified but appeared to be less promising than scenarios based on reduced food waste or redesigned agricultural systems.
Phosphorus (P) is the second most important nutrient after nitrogen (N) and can greatly diminish plant productivity if P supply is not adequate. Plants respond to soil P availability by adjusting ...root biomass to maintain uptake and productivity due to P use. In spite of our vast knowledge on P effects on plant growth, how to functionally model enhanced root biomass allocation in low P environments is not fully explored. We develop a dynamic plant model based on the principle of optimal carbon (C) and P allocation to investigate growth and functional response to contrasting levels of soil P availability. By describing plant growth as a balance of growth and respiration processes, we optimize C and P allocation in order to maximize leaf productivity and drive plant response. We compare our model to a field trial and a set of hydroponic experiments which describe plant response at varying P availabilities. The model is able to reproduce long-term plant functional response to different P levels like change in root-shoot ratio (RSR), total biomass and organ P concentration. But it is not capable of fully describing the time evolution of organ P uptake and cycling within the plant. Most notable is the underestimation of organ P uptake during the vegetative growth stage which is due to the model's leaf productivity formalism. In spite of the model's parsimonious nature, which optimizes for and predicts whole plant response through leaf productivity alone, the optimal growth hypothesis can provide a reasonable framework for modelling plant response to environmental change that can be used in more physically driven vegetation models.
PDF
