Trends and variability of water balance components over a tropical savanna and Eucalyptus forest in Australia

In this paper, the long-term dynamics of water balance components in two different contrasting ecosystems in Australia were simulated with an ecohydrological model (WAter Vegetation Energy and Solute modelling (WAVES)) over the period 1950–2015. The selected two ecosystems are woodland savanna in Daly River and Eucalyptus forest in Tumbarumba. The WAVES model was first manually calibrated and validated against soil water content measured by cosmic-ray probe and evapotranspiration measured with eddy flux techniques. The calibrated model was then used to simulate long-term water balance components with observed climate data at two sites. Analyzing the trends and variabilities of potential evapotranspiration and precipitation is used to interpret the climate change impacts on ecosystem water balance. The results showed that the WAVES model can accurately simulate soil water content and evapotranspiration at two study sites. Over the period of 1950–2015, annual evapotranspiration at both sites showed decreasing trends (−1.988 mm year−1 in Daly and −0.381 mm year−1 in Tumbarumba), whereas annual runoff in Daly increased significantly (5.870 mm year−1) and decreased in Tumbarumba (–0.886 mm year−1). It can be concluded that the annual runoff trends are consistent with the rainfall trends, whereas trends in annual evapotranspiration are influenced by both rainfall and potential evapotranspiration. The results can provide evidence for controlling the impacting factors for different ecosystems under climate change.

Eucalyptus forest plantation assessment of vegetation health using satellite remote sensing techniques

Early examination of the water condition of the plants utilizing remote sensing technology can be used to assess the health of the vegetation in the Eucalyptus forest plantation. To preserve a sustainable wood supply and wooded region that is necessary to human life and vital wood supplies, the forested region should be protected from disease and environmental damage. Disease and environmental impacts are two of the most critical challenges in Eucalyptus forest management. To calculate the vegetation index and identify land cover in the research region, remote sensing with Catalyst Professional software based on Object Analyst (OBIA) tools was utilized. The NDVI (Normalized Difference Vegetation Index) is a valuable index for assessing early vegetation health. For atmospheric correction and haze removal, the image was first pre-processed with ATCOR tools. Second, the image was converted to NDVI using algorithm library tools. In addition, for land cover classification in the area, an OBIA based on Support Vector Machine (SVM) was utilized, followed by an accuracy assessment. Using ArcGIS software, zonal statistics were used to calculate the NDVI value for each land cover category. According to the method, the map produced roads, plantations, buildings, low-density vegetation, oil palm, and open area classifications. Based on accuracy assessment in OBIA, plantation, oil palm, and open area were all 100% accurate, whereas low-density vegetation and oil palm were 100% accurate according to the user. Producer accuracy was lowest on roads, whereas user accuracy was lowest in open areas. Non-vegetated land is difficult to classify at this site, according to the accuracy assessment results. The map improved accuracy since the study used a lower segmentation scale factor of 50, which produced fine vectors ascribed for classification. The average NDVI for oil palm area was 0.71, and 0.69 for plantation. Because it was difficult to classify open areas and roads, the NDVI for the class was low, at 0.37 and 0.22, respectively. From land use classification, the plantation was classified (37%), low-density vegetation area (28%), and oil palm (21%). Others make up only 2 to 7% of the site’s overall area. According to the study, NDVI is a useful indicator for assessing the health of vegetation in areas where NDVI values are larger than 0.70 and presents pf mixed landscape and non-vegetated features. A higher NDVI value implies that the plant is in good enough shape to conduct photosynthetic activities thus producing biomass for sustaining vegetation health. This type of inquiry can forecast more indices to produce higher accuracy of land use maps for the Eucalyptus plantation. At the same time, this type of research can assist forest managers in detecting large areas in their plantation for vegetation health assessment such as for early disease detection.

Effect of Feller-Buncher Model, Slope Class and Cutting Area on the Productivity and Costs of Whole Tree Harvesting in Brazilian Eucalyptus Stands

The operational productivity and costs of tree felling operations can be influenced by several factors, among which, the machine characteristics, slope class, the cutting area and the individual volume of the trees stand out. Thus, the main objective of the present study was to analyze the productivity and production cost for two feller-bunchers with different technical characteristics operating in a eucalyptus forest. The productivity was calculated from a time study and the factors analyzed were two feller-buncher models, two slope classes, and two cutting areas. The machine cost per scheduled hour was based on the methodology of the Food and Agriculture Organization of the United Nations. Analysis of the results showed that the felling and turn operational elements occupied the most time in the operational cycle of feller-bunchers. The machine cost per scheduled hour was USD 69.69 h−1 for feller-buncher 1 and USD 102.03 h−1 for feller-buncher 2. In conclusion, the distinct technical characteristics of feller-bunchers were found to influence the productivity and, consequently, the cost, of the felling operation during the harvesting of whole eucalyptus trees.

Effect of Field Sample Size on Large-Scale Subtropic Forest Inventory Attribute Estimation Based on Airborne Laser Scanner Data

Exploring the effect of the sample size on the estimation accuracy of airborne LiDAR forest attributes in a large-scale area can help in optimizing the technical application scheme of operational ALS-based large-scale forest stand inventories. In our study, sample datasets composed of different sample plots were constructed by repeated sampling from 1003 sample plots in a subtropical study area covering 2376 × 103 km2. Sixteen multiplicative power models were built in each forest type consisting of four forest attributes. Through these models, the variations of standard deviation (SD) and coefficient of variation (CV) of R2 and rRMSE of forest attribute estimation models for different quantity levels of sample plots were also analyzed. The results showed that, first, when the sample size increased from 30 to the top limit, the SD of the forest attributes and LiDAR variables showed a decreasing trend. Second, as the sample size increased, the rRMSE of the 16 forest attribute estimation models gradually decreased, while the R2 gradually increased. Third, when the sample size was small, both the SD of R2 and rRMSE of the models were large, and the SD of R2 and rRMSE gradually decreased as the sample size increased. In 50 models conducted for each attribute at the same sample size, for the mean standard deviations of forest attributes, the ten best performing models were lower than those of the total 50 models, and the worst ten models were the opposite. When the sample size increased, the accuracy of each forest attribute estimation model for each forest type gradually improved. The variation of forest attributes and the LiDAR variable of the construction model are critical factors that affect the model’s accuracy. To efficiently apply airborne LiDAR in order to survey large-scale subtropical forest resources, the sample size of the Chinese fir forest, pine forest, eucalyptus forest, and broad-leaved forest should be 110, 80, 85, and 70, respectively.

What if the best option for managing burnt forest areas was not managing them at all? A modelling approach to evaluate different post-fire management scenarios

<p>Scars left by wildfires are easily noticeable in the Mediterranean landscape, turning these events a major issue for forest management. Like any wound, even those left by fires must be treated to properly regenerate.</p><p>In a burned area the vegetation cover is often destroyed by the fire, leaving the soil unprotected and vulnerable to erosion. The alterations of soil properties induced by fires lead to an increase in surface runoff, promoting the detachment of sediments and consequently endangering the water quality of downstream aquatic systems. If left unmanaged, the spontaneous regeneration of vegetation will eventually cover the affected area, restoring its natural hydrological cycle. After a wildfire, in Portugal, following an economical based perspective, the burned areas are normally reforested with selected plants species, namely Eucalypt and Maritime Pine, not infrequently by resorting to the implementation of bench terraces.</p><p>To define the best management strategy to adopt after a fire, the scientific community is continuously assessing the effects of these forestry practices on soils and the downstream water bodies. In this study, the Soil and Water Assessment Tool (SWAT) was used to simulate three different post-fire land management scenarios for a small catchment (21.9 ha) in central Portugal. The choice of this basin relates to the implementation of terraces to create a eucalyptus forest production area, 6 months after a fire burned the catchment completely. The model was calibrated for streamflow and water quality at the catchment outlet, both for the short post-fire period and the following eucalyptus cycle. In this study two post-fire scenarios were created, one with the recovery of the vegetation, and another in which a highly effective erosion mitigation measure (mulching) was applied to the high and moderate fire severity burned areas. The third scenario corresponded to the implementation of the terraces and the actual eucalyptus cycle.</p><p>Both the mulch application and the eucalyptus cycle scenario showed an important reduction in soil loss and sediment transport when compared with the post-fire spontaneous recovery scenario. A smaller reduction in the total runoff, as well as a negligible change in total flow, was found in the mulching scenario when compared with the spontaneous recovery one. Despite the eucalyptus cycle presented the highest flow discharge for the overall period, it presents smaller discharge peaks when compared with the two post-fire management scenarios.</p>

Determination of field capacity in the Chibunga and Guano rivers micro-basins

Background: The micro-basins of the Chibunga and Guano rivers are located within the sub-basin of the Chambo River, which starts at the thaw of the Chimborazo, crosses the cities of Guano and Riobamba, and ends in the Chambo River. These rivers are considered fluvial hydrological forces and geological limits of the aquifer, located in this sub-basin. For this reason, our investigation addressed the field capacity in the micro-basins of Chibunga and Guano rivers, to determine the maximum retention potential, i.e., the saturation of water in the soil. Methods: We investigated the change of precipitation to runoff through the correlations between the characteristics of the soil and its vegetation. We applied the Curve Number (CN) method introduced by the United States Soil Conservation Service (USSCS); this represents an empirical model, which relates the vegetation cover to the geological and topographic conditions of the soil. Along with the geographic information system, the model allows to represent the variation of runoffs for each micro-basin, according to the different land use categories, over the time frame from 2010 to 2014. Results: We found that the maximum retention potential is directly affected by CN values, representing the runoff potential. Highest values of 100 belong to the wetlands, urban area, snow, and water, as rain is converted directly into runoff, being impervious areas. The Guano river micro-basin possesses clay soil with CN of 78, the soil texture for eucalyptus forest is clay loam, and its CN value, 46, is the lowest of the data set. Knowledge of field capacity allows to properly evaluate the storage capacity of soil and water conservation. Conclusions: Results of this work will be useful in the quantification of the water balance, to determine the water supply and demand.

Stand Stability of Pure and Mixed Eucalyptus Forests of Different tree Species in a Typhoon-prone Area

Background: Stable stand structure of mixed plantations is the basis of giving full play to forest ecological function and benefit, and the pure Eucalyptus plantations with large-area and successive planting have presented to be unstable and vulnerable in typhoon-prone area. In this study, we investigated eight 30 m × 30 m plots randomly in pure and mixed eucalyptus forests on growth status, characterized and compared the distribution of non-spatial structure of mixtures with that of mono-species plantation, and evaluated the stand quality and stability from eight indexes including preservation rate, stand density, height, diameter, stem form, degree of slant, tree species composition and age structure, so as to find out the best mixed composition and pattern of eucalyptus and other tree species in typhoon-prone area. Results: Eucalyptus surviving in the mixed forest of Eucalyptus and A. mangium (EA) and the mixed forest of Eucalyptus and P. elliottii × P. caribaea (EP) were 5.0% and 7.6% greater than those in pure Eucalyptus forest (E) respectively, while only the stand preservation rate of EA was greater (+2.9%) than that of pure Eucalyptus forest. The proportions of all mixtures on the height class that greater than 7 m were fewer than that of monoculture. The proportion of EA and EN (mixed forest of Eucalyptus and N.cadamba) on the diameter class that greater than 7 m were 10.6% and 7.8% respectively more than that of monoculture. EN got a highest ratio of branching visibly (41%), EA got a highest ratio of slant stems (8.1%) and EP got a most straight and complete stem form (68.7%). The stand stability of the mixed forest of Eucalyptus and A. mangium presents to be optimal for its subordinate function value (0.76) and status value (ω = 0.607) of real stand were the largest. Conclusion: A. mangium is a most superior tree specie to mix with Eucalyptus for a more stable stand structure in the early growth stage to approach an evident and immense stability and resistance, which is of great significance for the forest restoration of Eucalyptus in response to extreme climate and on the forest management.