Understanding forest transition in the Philippines: main farm-level factors influencing smallholder’s capacity and intention to plant native timber trees

The ‘when, where and how’ of decisions by smallholder upland farmers to plant trees as part of their use of natural, human and capital resources needs to be understood if policy support is to result in actual recovery of tree cover as part of a ‘forest transition’ trajectory. In large parts of the Philippines the turning point may be close. Data on resource access and tree planting decisions were gathered from a household survey, with a total of 148 respondents in four rural communities in Leyte Province in Central Philippines. Data were analysed using logistic regression analysis. Household-level results reveal that the outcomes of the decision-making processes primarily depend on the availability of land and access to remaining forest resources rather than socio-cultural or economic factors. The total area of land and number of parcels managed by the household plus security of land tenure through ownership was found to have a statistically significant effect on farmers’ decision to plant native timber trees. Access to surrounding natural forest is negatively associated with farmer tree planting.     

Variation in the radial patterns of sap flux density in pubescent oak (Quercus pubescens) and its implications for tree and stand transpiration measurements

Radial variation in sap flux density across the sapwood was assessed by the heat field deformation method in several trees of Quercus pubescens Wild., a ring-porous species. Sapwood depths were delimited by identifying the point of zero flow in radial patterns of sap flow, yielding tree sapwood areas that were 1.5-2 times larger than assumed based on visual examinations of wood cores. The patterns of sap flow varied both among trees and diurnally. Rates of sap flow were higher close to the cambium, although there was a significant contribution from the inner sapwood, which was greater (up to 60% of total flow) during the early morning and late in the day. Accordingly, the normalized difference between outer and inner sapwood flow was stable during the middle of the day, but showed a general decline in the afternoon. The distribution of sap flux density across the sapwood allowed us to derive correction coefficients for single-point heat dissipation sap flow measurements. We used daytime-averaged coefficients that depended on the particular shape of the radial profile and ranged between 0.45 and 1.28. Stand transpiration calculated using the new method of estimating sapwood areas and the radial correction coefficients was similar to (Year 2003), or about 25% higher than (Year 2004), previous uncorrected values, and was 20-30% of reference evapotranspiration. We demonstrated how inaccuracies in determining sapwood depths and mean sap flux density across the sapwood of ring-porous species could affect tree and stand transpiration estimates.     

Hypoglycemic effect of lupin seed γ-conglutin in experimental animals and healthy human subjects

A lupin seed γ-conglutin-enriched preparation was tested in a glucose overload trial with both murine models and adult healthy volunteers. The results with rats showed a dose-dependent significant decrease of blood glucose concentration, which confirmed previous findings obtained with the purified protein. Moreover, three test-product doses equivalent to 630, 315, and 157.5 mg γ-conglutin, orally administered 30 min before the carbohydrate supply, showed a relevant hypoglycemic effect in human trials. Insulin concentrations were not significantly affected. The general hematic parameters did not change at all.This is the first report on the glucose-lowering effect of lupin γ-conglutin in human subjects.     

Species distribution models applied to plant species selection in forest restoration: are model predictions comparable to expert opinion?

An expert on local flora usually is the best option for plant species selection in most ecological restoration projects; although species selection often needs to be dealt with swiftly as well as on a limited budget, and obtaining the opinion of a local expert may not always be an economically viable alternative. In such cases, species distribution models (SDM) may offer a faster and more cost effective alternative. We asked six experts to rank native tree species according to their suitability at 24 forest sites. The predictive performance of the suitability rankings was evaluated by assessing their ability to discriminate present from absent species in the observed tree assemblages at each evaluation site. We used the area under the receiver operating characteristic curve to calculate the probability that the estimated suitability for a species present at a particular evaluation site is greater than the estimate for an absent species (both picked at random). Suitability rankings were also obtained from the predictions of SDM and the same procedure was used to estimate the predictive performance of the set of models at each site. The experts offered concordant suitability rankings at almost every evaluation site. There were no significant differences in the predictive performance of the SDM and four of the experts, although the SDM performed slightly better than the other two experts. Our results point to the suitability of the proposed species distribution modeling approach to obtain fast and cost effective recommendations for species selection in forest restoration projects.     

‘Climatic factors control rodent seed predation in Pinus pinea L. stands in Central Spain’

? Context

Pinus pinea L. presents serious problems of natural regeneration in managed forest of Central Spain. The species exhibits specific traits linked to frugivore activity. Therefore, information on plant–animal interactions may be crucial to understand regeneration failure.

? Aims

Determining the spatio-temporal pattern of P. pinea seed predation by Apodemus sylvaticus L. and the factors involved. Exploring the importance of A. sylvaticus L. as a disperser of P. pinea. Identifying other frugivores and their seasonal patterns.

? Methods

An intensive 24-month seed predation trial was carried out. The probability of seeds escaping predation was modelled through a zero-inflated binomial mixed model. Experiments on seed dispersal by A. sylvaticus were conducted. Cameras were set up to identify other potential frugivores.

? Results

Decreasing rodent population in summer and masting enhances seed survival. Seeds were exploited more rapidly nearby parent trees and shelters. A. sylvaticus dispersal activity was found to be scarce. Corvids marginally preyed upon P. pinea seeds.

? Conclusions

Survival of P. pinea seeds is climate-controlled through the timing of the dry period together with masting occurrence. Should germination not take place during the survival period, establishment may be limited. A. sylvaticus-mediated dispersal does not modify the seed shadow. Seasonality of corvid activity points to a role of corvids in dispersal.     

Enhanced Tolerance to Mercury in a Streptomycin-Resistant Strain of Euglena gracilis

Toxicity of Hg²⁺ was determined in two strains of Euglena gracilis var. bacillaris: the wild-type (B) and a streptomycin-resistant strain (Sm^r). Cells were cultured under 12-h dark/12-h light regime or under continuous darkness. In the dark/light cultures, cellular growth was severely diminished in the B strain by Hg²⁺, whereas only a slight decrease was attained in the Sm^r strain; Hg²⁺ also affected the photosynthetic and respiratory activities of the B strain, but not those of Sm^r strain. Under continuous darkness, cellular growth of both strains was lower than under dark/light cycles, but it was inhibited by Hg²⁺ to a much lesser extent. Cell culture by 5 days under continuous dark or by 8 days of dark/light cycles resulted in a higher intracellular content of mercury in B strain than in Sm^r strain. In contrast, in both culture conditions, the fraction of mercury removed from medium by B strain was lower than that attained by Sm^r strain, whereas the ability to bio-transform (reduce) Hg²⁺ was two times higher in the mutant strain. The results suggested that Sm^r strain cells acquired an ability to remove Hg²⁺ from the medium, which was not associated to accumulation and which conferred protection against mercury.     

Agronomic response and water productivity of almond trees under contrasted deficit irrigation regimes

We investigated the long-term effects of different deficit irrigation (DI) options on tree growth, shoot and leaf attributes, yield determinants and water productivity of almond trees (Prunus dulcis, cv. Marta) grown in a semiarid climate in SE Spain. Three partial root-zone drying (PRD) irrigation treatments encompassing a wide range of water restriction (30%, 50% and 70% of full crop requirements, ET_c) and a regulated deficit irrigation treatment (RDI, at 50% ET_c during kernel-filling) were compared over three consecutive growth seasons (2004–2006) to full irrigation (FI). The results showed that all deficit irrigation treatments have a negative impact on trunk growth parameters. The magnitude of the reduction in trunk growth rate was strongly correlated through a linear relationship with the annual volume of water applied (WA) per tree. Similarly, a significant relationship was found between WA and the increase in crown volume. In contrast, leaf-related attributes and some yield-related parameters (e.g., kernel fraction) were not significantly affected by the irrigation treatments. Except in PRD₇₀, individual kernel weight was significantly reduced in the deficit irrigated treatments. Kernel yield, expressed in percent of the maximum yield observed in the FI treatment, showed a linear decrease with decreasing WA and a slope of 0.43, which implies that a 1% decrease in water application would lead to a reduction of 0.43% in yield. Water productivity increased drastically with the reduction of water application, reaching 123% in the case of PRD₃₀. Overall, our results demonstrate the prevalence of direct and strong links between the intensity of the water restriction under PRD – i.e., the total water supply during the growing season – and the main parameters related to tree growth, yield and water productivity. Noteworthy, the treatments that received similar annual water volumes under contrasted deficit irrigation strategies (i.e., PRD₇₀ and RDI) presented a similar tree performance.     

Sodicity and salinity in a Brazilian Oxisol cultivated with sugarcane irrigated with wastewater

Changes in soil sodicity-salinity parameters are one of the most characteristic alterations after treated sewage effluent (TSE) irrigation in agro-systems. Considering the importance of these parameters for agricultural management, as well as the economical value of sugarcane for Brazil, the present study aimed at evaluating effects on soil sodicity and salinity under tropical conditions over 16 months of TSE irrigation in a sugarcane plantation at Lins, São Paulo State, Brazil. Soil samplings were carried out in February 2005 (before planting), December 2005 (after 8 months of TSE irrigation) and September 2006 (after 16 months of TSE irrigation) following a complete block design with four treatments and four replicates. Treatments consisted of: (i) control, without TSE irrigation; (ii) T100, T150 and T200, with TSE irrigation supplying 100% (0% surplus, total of 2524 mm), 150% (50% surplus, total of 3832 mm) and 200% (100% surplus, total of 5092 mm) of crop water demand, respectively. Compared to initial soil conditions, at the end of the experiment increases of exchangeable sodium (from 2.4 to 5.9 mmol_c kg⁻¹), exchangeable sodium percentage (ESP) (from 8 to 18%), soluble Na (from 1.4 to 4.7 mmol L⁻¹) and sodium adsorption ratio (SAR) of soil solution (from 3.6 to 12.6 (mmol L⁻¹)^0.5) were found in the soil profile (0-100 cm) as an average for the irrigated plots due to high SAR of TSE. Associated with the increments were mostly significant increases in clay dispersion rates at depths 0-10, 10-20 and 20-40 cm. Electrical conductivity (EC) of soil solution increased during the TSE irrigation period whereas at the end of the experiment, after short term discontinuation of irrigation and harvest, EC in the topsoil (0-10 and 10-20 cm) decreased compared to the previous samplings. Moreover, despite increasing sodicity over time mainly insignificant differences within the different irrigated treatments were found in December 2005 and September 2006. This suggests that independent of varying irrigation amounts the increasing soil sodicity over time were rather caused by the continuous use of TSE than by its quantity applied. Moreover, also plant productivity showed no significant differences within the TSE irrigated plots. The study indicates that monitoring as well as remediation of soil after TSE irrigation is required for a sustainable TSE use in order to maintain agricultural quality parameters.     

Layered double hydroxides as supports for the slow release of acid herbicides

A Mg/Al layered double hydroxide (LDH) was intercalated with the anionic herbicides 2,4-D, MCPA, and picloram by using three different methodologies: (i) direct synthesis (DS), (ii) regeneration (RE), and (iii) ion exchange (IE). The resulting complexes were characterized and assayed by batch release and column leaching tests, aiming at the controlled release of these herbicides. All the tested LDH-herbicide complexes displayed similar slow herbicide release properties in water, although the IE method seemed to result in complexes with a greater fraction of herbicide in a readily available form. Apparently, the LDH-herbicide complexes released most of the active ingredient present in the complexes at the end of the batch release experiment. This was attributed to the replacement of the intercalated herbicide by carbonate and hydroxyl anions from the aqueous solution. Compared to the free herbicides, the application of the three LDH-herbicide complexes (RE) to soil columns resulted in reduction in the maximum herbicide concentration in leachates and led to the retardation of herbicide leaching through the soil. All LDH-herbicide complexes presented an herbicidal efficacy similar to that of the free (technical) herbicides. Our results indicated the potential applicability of LDHs as supports for the preparation of slow release formulations of acid herbicides such as 2,4-D, MCPA, or picloram.