Assessing the Effects of Plant Roots on Soil Water Infiltration Using Dyes and Hydrus-1D

Forestry eco-hydrology is closely related to root architecture, and soil water infiltration has been always associated with root architecture. In this study, dye infiltration experiments and HYDRUS-1D were used to quantify the effects of different root architectures on the dynamics of soil water infiltration, volumetric water content, and soil water pressure head. The results provide evidence that root channels acted as preferential flow paths for water infiltration and percolation into the soil. Maize fibrous roots, rubber trees fine roots, and Spartina alterniflora smooth roots easily penetrated the plough layer of an agriculture site, the hard soil layer of a forest site, and the alternating sandy and mud layers of an intertidal zone, respectively. The initial and final infiltration rates were significantly different between the rooted and rootless soil profiles. The root-induced infiltration events lowered the propagation time of the wetting front across the rooted soil profile by 33%–113% than the rootless soil (p p S. alterniflora smooth roots. The results indicate that the downward movement, volumetric water content, and soil water pressure head were higher in soil profiles having plant roots than the rootless soil, and the degree of roots effects depended on roots architectures, soil hardness, and soil layer configuration. The findings provide evidence that root channels can act as preferential flow paths for water infiltration and percolation into the soil

Socioeconomic and Cultural Importance of The Yellow-Fronted Canary (Serinus Mozambicus) in Northern Benin

The species yellow-fronted canary undergoes a real traffic due to its song and medico-magical properties in order to supply local commercial networks. This study aims to assess the socioeconomic and cultural importance of this bird in order to identify the cohorts of actors involved along this activity chain. In this context a survey was carried out among 400 breeders in four agroecological zones of Benin (ZAE II; ZAE III, ZAE IV and ZAE V). The questionnaire also focused on general characteristics of the respondents on aspects related to general knowledge of the bird, its social importance, purchase and sale price, cultural importance and breeders’ perceptions. Canary traders, mostly with primary education level (63.25%) and Muslim (97.5%), were on average 44 years old and an average experience of 27 years. They exercised this activity in part-time (96.5%). The knowledge about canary is shared is different depending on the ethnic group. The activity was profitable for all of them (100%) with 128,624 FCFA (233.18 USD) net profit per month. The trader's education level, whether or not he belonged to ZAE II, the number of birds he had in his possession, the daily amount he invested in their food, their selling price, the number of years he made the activity, his experience in the business were the factors that determine the net profit of the canary’s trader. However, canaries' breeding in north-Benin is based on a complex system with actors who develop many myths around medico-magical practices. This study was necessary to better assess the pressure on the species in order to anticipate its conservation

Hill-placement of manure and fertilizer for improving maize nutrient- and water-use efficiencies in the northern Benin

Optimizing the use of organic and mineral fertilizer in rain-fed maize production is crucial for sustainable food production in sub-Saharan Africa. This study investigates the effect of hill-placement of two nutrient sources (farmyard manure and synthetic fertilizer) on nutrient- and water-use efficiencies of maize crops i.e. recovery efficiency (NUEre), internal utilization efficiency (NUEie) and water use efficiency (WUE). A four-year trial was conducted in the tropical sub-humid zone of the northern Benin with a factorial combination of farmyard manure at three levels (0, 3 and 6 t ha−1, hereafter NM, 3M and 6M, respectively) and three levels of fertilizer [0% (NF), 50% (50F) and 100% (100F) of the recommended rate (76 kg N + 13.1 kg P + 24.9 kg K ha−1) by the national center for agricultural research. The NUEre decreased with increasing rate of manure and/or fertilizer, but the decreasing rate was lower under combined manure and fertilizer application. However, the NUEie increased with the increasing manure and fertilizer amounts. The WUE was significantly higher in 3M and 6M treatments than in NM treatment, and higher in 50F and in 100F than in NF treatments. The combination of 3000 kg ha−1 farmyard manure with half recommended fertilizer rate (100 kg ha−1) could be suggested as an optimal nutrient management practice for maize production in the Northern Benin. Future studies should target the other agro-ecological zones in Benin, and also consider other widely cultivated crops in the study area for reducing yield gaps and promote food security

Assessing the impact of forest conversion to plantations on soil degradation and forest water conservation in the humid tropical region of Southeast Asia: Implications for forest restoration

The deterioration of soil and water resources resulting from tropical rainforest (TR) conversion to monoculture plantations (e.g., rubber monoculture; RM) could be restrained and restored through intercropping. However, the response of soil properties and forest water conservation function to forest conversion, i.e., the conversion of RM to rubber rainforest (RR: derived from the invasion of wild native plants in abandoned RM), is still unclear. We involved four forests types, TR, RM, rubber-tea agroforestry (RTA), and RR, as transitional steps of forest conversion through a space-for-time substitution approach to examine the dynamic of soil physical, hydrological and chemical properties during the forest conversion (from TR to RM, RM to RTA, RTA to RR, and retransformation into TR). The results show that SOC, TN, TP, and TK decreased in the order of TR > RR > RTA > RM, which was followed by the trend of soil hydrological and physical properties among these forest types. The interrelation between soil physical and chemical properties was mediated by water flow behaviours. High macroporosity and related low Ks in TR favoured the occurrence of water flow behaviours. Water flow behaviours not only influenced the distribution of soil chemical elements but also played a crucial role in forming appropriate conditions for nutrient turnover. The co-occurrence of preferential and matrix flow was more prevalent in the rainy season than dry season due to the higher frequency and higher amount of rainwater. The preferential flow promoted the soil water flow in the water flow paths and enhanced water storage in the soil pores. In short, the soil properties and soil water supply decreased in the following order: TR > RR > RTA > RM, suggesting that the severe soil degradation that occurred after TR conversion to RM can be restored back to the extent of TR after a period of succession. The results provided new insights for understanding the forest water conservation function and soil properties in response to forest conversion and highlighted that the RR appeared as a transitional stage during the course of forest restoration from RM to TR under low rubber demand. These findings improve the current knowledge of the relationship among soil physical, hydrological and chemical properties in the rubber-growing humid tropical region of Southeast Asia

Simulated high-intensity phorophyte removal mitigates the robustness of epiphyte community and destroys commensal network structure

peer reviewedInterspecies interactions deserve more attention in biodiversity conservation since the elimination of only one species can indirectly impede the dependent species through ecological networks. Phorophytes, which provide physical support, constitute the basis for the occurrence of epiphytes. Epiphytes and their host phorophytes thus form a typical commensal interaction network. However, the impacts of phorophyte removals on the diversity and stability of epiphyte communities are poorly understood. Such understanding may illuminate guidance on forest protection and management. In this study, two species-based networks (raw species-based network and standardized species-based network) and one raw individual-based network between vascular epiphytes and phorophytes were analyzed in a tropical rainforest in Southwest China. Based on the construction of second extinction models, the robustness of epiphyte community and the dynamic of network structure were calculated for raw species-based network and individual-based network under different phorophyte removal scenarios. As a result, all three epiphyte-phorophyte networks exhibited low connectivity and moderate modularity; the nestedness of the standardized species-based network was lower than that of the raw species-based network, but remained higher than that of the raw individual-based network. The removal of the strongest interactor could lead to the rapid collapse of epiphytic communities, while the reverse order increased community robustness. Most importantly, for raw species-based and individual-based networks, we found the curves of modularity and nestedness started changing drastically and fluctuated frequently when the phorophytes’ removal rate approaches 80%. Our results suggest that the keystone phorophytes (such as generalists, large individuals and abundant species) should receive special attention in conservation efforts to sustain tropical epiphytic systems; and when subject to removal, the intensity of phorophyte removal should be kept below certain threshold to achieve long-term stability of epiphytic communities

Uncorrected soil water isotopes through cryogenic vacuum distillation may lead to a false estimation on plant water sources

Abstract Successful use of stable isotopes (δ2H and δ18O) in ecohydrological studies relies on the accurate extraction of unfractionated water from different types of soil samples. Cryogenic vacuum distillation (CVD) is a common laboratory‐based technique used for soil water extraction; however, the reliability of this technique in reflecting soil water δ2H and δ18O is still of concern. This study examines the reliability of a newly developed automatic cryogenic vacuum distillation (ACVD) system. We further assessed the impacts of extraction parameters (i.e. extraction time, temperature and vacuum) and soil properties on the recovery of soil water δ2H and δ18O for the ACVD and traditional cryogenic vacuum distillation (TCVD) systems. Finally, we investigated the potential influence of CVD (ACVD and TCVD) technique on the prediction of plant water uptake through a sensitivity analysis. Both ACVD and TCVD similarly extracted water from the rewetted soils, but none of the CVD systems successfully recovered the isotopic signatures of doped water from soil materials. Mean δ2H offsets of extracted soil water were −2.6 ± 1.3‰ and −2.4 ± 1.7‰ for ACVD and TCVD, respectively, while mean δ18O offsets were −0.16 ± 0.14‰ and −0.39 ± 0.37‰. The isotopic offsets of CVD systems were positively correlated with soil clay content, and negatively correlated with soil water content. Using corrected soil data (with CVD offsets) could improve the prediction of plant water uptake based on its high correlation with the environmental factors. This study identifies the isotopic offsets of CVD systems (i.e. ACVD and TCVD) and provides possible solutions for better predicting plant water sources. Even though, the wide use of CVD techniques probably induce noticeable uncertainties in the prediction of plants water uptake depths. The dataset of soil water extraction in this study will have implications for the technological development of CVD techniques

Cerium-manganese oxide as catalyst for transesterification of soybean oil with subcritical methanol

A heterogeneous cerium-manganese oxide catalyst was synthesized by a co-precipitation method, characterized and tested in soybean oil transesterification with methanol under subcritical condition for methanol. Conversion of triglycerides after 40 min of transesterification in a batch process was over 99% with a fatty acid methyl ester (FAME) yield of 91.6% when 3 wt.% of catalyst based on oil, and 18:1 methanol/oil molar ratio were applied. The same amount of catalyst was used in 12 cycles of transesterification with catalyst regeneration performed only after the 7th cycle. The catalyst exhibited good tolerance toward soybean oil containing below 1.5 wt.% of water or 4 wt.% of free fatty acids. The mechanisms of Ce/Mn catalytic activity and its deactivation were discussed according to the characterization of the fresh and used catalyst according to results of different analytical methods: the Hammett titration, BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), FTIR, X-ray diffraction (XRD), ICP-MS and TG-DSC. It was assumed that deactivation of catalyst was mainly a consequence of manganese solubility in methanol and glycerol