Growth differential related to wood structure and function of Eucalyptus spp. clones adapted to seasonal drought stress

Aim of the study: To evaluate the growth performance, wood density and anatomical features of four drought-tolerant Eucalyptus spp. clones, at 4 years, and to examine the relationships between these characteristics and some functional parameters. Area of study: The analyzed trees were from a clonal test installed in a region characterized by seasonal drought stress in central-western Brazil. Methods: Trees were felled, followed by obtaining dendrometric parameters and wood disk sampling to determine wood bulk density by x-ray densitometry, and morphometric parameters of fibers and vessels in order to evaluate the xylem hydraulic architecture. Lumen fraction (F), vessel composition (S) and hydraulic conductivity (Ks) were estimated. Results: Clone D (E. urophylla x E grandis) presented the highest growth rates, which was related to anatomical characteristics such as low relative frequency of wide vessels. High theoretical Ks does not necessarily imply higher growth rates and were related to lower wood densities. It is possible to infer that the better xylem adjustability of Eucalyptus trees in response to drought stress conditions is associated with increased vessel composition to the detriment of higher hydraulic conductivity. Research highlights: Vessel composition showed a greater variation among Eucalyptus genotypes and was positively associated with growth performance.

Drought responsiveness in two Mexican conifer species forming young stands at high elevations

Aim of study: To determine the response of high-altitudinal forests to seasonal drought. Area of study: Monte Tláloc, Estado de México and Rancho Joyas del Durazno, Municipality of Río Verde, San Luis Potosí, México. Materials and methods: In this study, we evaluate the response to drought and hydroclimate in two young Mexican conifers sampled at high elevation, correlating records of tree-ring growth and the Normalized Difference Vegetation Index (NDVI). Main results: The results show that Pinus teocote and Abies religiosa are vulnerable to the precipitation regime and warm conditions of winter-spring. The physiological response mechanisms seem to be differentiated between the species, according to the effects of drought stress. The NDVI demonstrated the different temporal responses of the species according to their inherent physiological mechanisms in response to hydroclimatic limitations. This differentiation can be attributed to the spatial variation present in the particular physical and geographic conditions of each area. The dry and warm seasonal climates reveal P. teocote and A. religiosa to be species that are vulnerable to drought conditions. However, further evaluation of the resistance and resilience of these species is necessary, as well as disentanglement of the effects of associated mechanisms that can influence the predicted processes of extinction or migration. Research highlights: Pinus teocote and Abies religiosa are vulnerable to the seasonal drought conditions. These results are of particular importance given the climatic scenarios predicted for elevated ecotones. Tree-ring widths and NDVI improved the response of radial growth to the climate, enhancing our understanding of forest growth dynamics. The response to climatic variability depends on the particular species.

Logistic Regression Analysis for Spatial Patterns of Drought Persistence

Drought is one of the natural hazards with potentially significant impacts on society, economy, and other natural resources over the globe. However, the understanding of drought characteristics and its persistence can significantly help to reduce the potential impacts of drought. Moreover, the knowledge about the spatiotemporal pattern of seasonal drought frequency and drought persistence is important for water resource management, agricultural development, energy consumption, and crop yields. Therefore, the present study is employed to examine the seasonal drought frequency and drought persistence in the region. In this regard, the standardized precipitation index (SPI) at the three-month time scale was used to determine meteorological drought. Furthermore, the logistic regression model is used to calculate the odds and probability of drought persistence from one season to the next for the selected stations by identifying the spatial pattern of seasonal drought frequency and persistence. The potential of the current analysis is validated on six selected stations of the northern area of Pakistan. The outcomes related to the current analysis provide the basis for taking more considerations on early warning systems and help to make the valuable decision for water resource management and agriculture sectors in Pakistan.