Spatial heterogeneity of factors influencing forest fires size in northern Mexico

In Mexico, forest fires are strongly influenced by environmental, topographic, and anthropogenic factors. A government-based database covering the period 2000-2011 was used to analyze the spatial heterogeneity of the factors influencing forest fire size in the state of Durango, Mexico. Ordinary least squares and geographically weighted regression models were fit to identify the main factors as well as their spatial influence on fire size. Results indicate that fire size is greatly affected by distance to roads, distance to towns, precipitation, temperature, and a population gravity index. The geographically weighted model was better than the ordinary least squares model. The improvement of the former is due to the influence of factors that were found to be non-stationary. These results suggest that geographic location determines the influence of a factor on fire size. While the models can be greatly improved with additional information, the study suggests the need to adopt fire management policies to more efficiently reduce the effect of anthropogenic factors. These policies may include more training for landowners who use fire for clearing, closure of roads, application of thinning, prescribed burning, and fire breaks in perimeters adjacent to roads.     

Hydrology-oriented (adaptive) silviculture in a semiarid pine plantation: How much can be modified the water cycle through forest management?

Hydrology-oriented silviculture might adapt Mediterranean forests to climatic changes, although its implementation demands a better understanding and quantification on the water fluxes. The influence of thinning intensity (high, medium, low and a control) and its effect on the mid-term (thinned plots in 1998 and 2008) on the water cycle (transpiration, soil water and interception) and growth [basal area increment (BAI)] were investigated in 55-year-old Aleppo pine trees. Thinning enhanced a lower dependence of growth on climate fluctuations. The high-intensity treatment showed significant increases in the mean annual BAI (from 4.1 to 17.3 cm²) that was maintained in the mid-term. Thinning intensity progressively increased the sap flow velocity (v _s) in all cases with respect to the control. In the mid-term, an increased functionality of the inner sapwood was also observed. Mean daily tree water use ranged from 5 (control) to 18 (high intensity) l tree^?1. However, when expressed on an area basis, daily transpiration ranged from 0.18 (medium) to 0.30 mm (control), meaning that in spite of the higher transpiration rates in the remaining trees, stand transpiration was reduced with thinning. Deep infiltration of water was also enhanced with thinning (about 30 % of rainfall) and did not compete with transpiration, as both presented opposite seasonal patterns. The changes in the stand water relationships after 10 years were well explained by the forest cover metric. The blue to green water ratio changed from 0.15 in the control to 0.72 in the high-intensity treatment, with the remaining treatments in the 0.34–0.48 range.     

Nitrogen dynamics during ecosystem development in tropical forest restoration

We considered whether ecological restoration using high diversity of native tree species serves to restore nitrogen dynamics in the Brazilian Atlantic Forest. We measured δ¹⁵N and N content in green foliage and soil; vegetation N:P ratio; and soil N mineralization in a preserved natural forest and restored forests of ages 21 and 52 years. Green foliage δ¹⁵N values, N content, N:P ratio, inorganic N and net mineralization and nitrification rates were all higher, the older the forest. Our findings indicate that the recuperation of N cycling has not been achieved yet in the restored forests even after 52 years, but show that they are following a trajectory of development that is characterized by their N cycling intensity becoming similar to a natural mature forest of the same original forest formation. This study demonstrated that some young restored forests are more limited by N compared to mature natural forests. We document that the recuperation of N cycling in tropical forests can be achieved through ecological restoration actions.     

Influence of water-stress acclimation and <Emphasis Type="Italic">Tuber melanosporum</Emphasis> mycorrhization on <Emphasis Type="Italic">Quercus ilex</Emphasis> seedlings

Mycorrhizal and non-mycorrhizal holm oak (Quercus ilex L.) seedlings inoculated with black truffle (Tuber melanosporum) were grown under nursery conditions and subjected to drought hardening for 4 months in autumn and winter followed by irrigation for 10 days. Leaf water potential and stomatal conductance were monitored during the 4 months of drought. When the test was completed (March), measurements were made for each treatment (inoculated or non-inoculated), and watering regime (watered and water-stressed). Pressure–volume curves, osmotic potential at full turgor, osmotic potential at zero turgor and the tissue modulus of elasticity near full turgor were calculated. Mycorrhizal colonization and growth, and the content of the main mineral nutrients N, P, K, Ca and Mg were measured. Water stress affected plant growth, caused an elastic adjustment of the plant tissues, and decreased the P and K content, and inoculation improved the nitrogen content. Drought acclimation apparently achieved the goal of improving the drought tolerance of holm oak seedlings, without depressing ectomycorrhizal root colonization by T. melanosporum. José Antonio Rodríguez Barreal—Deceased     

The interspecific variation of plant traits in brassicas engenders stronger aphid suppression than the intraspecific variation of single plant trait

Journal of Pest Science - Increasing either inter- or intraspecific plant diversity has shown the potential to engender bottom-up and top-down effects upon herbivorous pests. Nonetheless, because...     

Intestinal antiinflammatory activity of a lyophilized infusion of Turnera ulmifolia in TNBS rat colitis

Turnera ulmifolia is a plant popularly known in Brazil and South America as chanana. Some species of Turnera are widely used in folk medicine for different types of inflammatory diseases. In this study, the preventive intestinal antiinflammatory activity of a lyophilized infusion obtained from the aerial parts of T. ulmifolia was tested in the trinitrobenzenesulphonic acid (TNBS) model of rat colitis. The results obtained revealed that pretreatment to colitic rats with the extract, at 250 and 500 mg/kg, significantly attenuated the colonic damage induced by TNBS. This beneficial effect was associated with an improvement in the colonic oxidative status, since the infusion prevented the glutathione depletion that occurred as a consequence of the colonic inflammation. On the other hand, this antioxidant activity was confirmed in in vitro studies. In conclusion, the preventive effect exerted by the lyophilized infusion of T. ulmifolia in the TNBS model of rat colitis is probably related to its antioxidant properties, due to its flavonoids content.     

The power of discourse: Hard lessons for traditional forest communities in the Amazon

In the contemporary Amazon, ‘discourse’ is increasingly a new means of exercising power, influencing local society and the ways in which natural resources are managed. As society becomes ever more complex, direct means of exercising power no longer enjoy the same legitimacy and efficacy. Discourses are instead now assuming a dominant role in defining governance regimes; the sense of what is correct and socially acceptable, and what is not. This is particularly relevant for the rapidly advancing development frontiers in the Amazon region, where local communities are coming into contact with external players highly interested in their forest resources. This study focuses on understanding how external discourses can restrict the Amazonian communities' options for using their forests, but also how communities can harness these discourses to achieve their own claims and objectives. Empirical evidence from four study areas in the Bolivian, Brazilian and Peruvian Amazon regions is used to show how discourses on sustainable forest management are moulding forestry governance. The conclusion shows that while the discourses used by loggers and development organisations are strongly influencing the way communities manage their forests, some communities are also successfully using these discourses in alliances with environmental organisations to achieve acknowledgment of their demands.     

The effect of Tuber melanosporum Vitt. mycorrhization on growth, nutrition, and water relations of Quercus petraea Liebl., Quercus faginea Lamk., and Pinus halepensis Mill. seedlings

Mycorrhizal and nonmycorrhizal Quercus faginea Lamk., Quercus petraea Liebl., and Pinus halepensis Mill. one-year-old seedlings inoculated with Tuber melanosporum Vitt. have been analyzed with the purpose of studying the influence of mycorrhization on their growth, water relations, and mineral nutrition. The mycorrhization improved Q. petraea and P. halepensis seedling growth. In addition, the mycorrhization created an elastic adjustment in P. halepensis, although it did not cause any osmotic adjustment. Additionally, the mycorrhization increased phosphorus uptake in Q. faginea and P. halepensis, content of all nutrients in P. halepensis, and N content in Q. petraea.