Effect of tree-level airborne laser-scanning measurement accuracy on the timing and expected value of harvest decisions

The objective was to compare tree-level airborne laser-scanning (ALS) data accuracy with standwise estimation data accuracy as input data for forest planning, using tree- and stand-level simulators. The influence of the input data accuracy was studied with respect to (1) timing of the next thinning or clear-cutting and (2) the relative variation in the predicted income of the next logging expressed as the net present value (NPV). The timing and predicted NPV of thinning and clear-cutting operations were considered separately. The research was based on Monte Carlo simulations carried out with the tree- and stand-level simulators using a simulation and optimisation (SIMO) framework. The simulations used treewise measurements taken on 270 circular plots measured at the Evo Field Station, Finland, as input data. Deviations in the tree data measured were generated according to the mean standard errors found in standwise field estimation and tree-level ALS. The accuracy factors of ALS individual tree detection were based on the EUROSDR/ISPRS Tree Extraction Project. The results show that input data accuracy significantly affects both the timing and relative NPV of loggings. Tree-level ALS produces more accurate simulation results than standwise estimation with the error levels assumed. Diameter-based characteristics are the most important input data in all simulations. Accurate tree height estimates cannot be fully utilised in current simulators.     

Influence of improved fallow systems and phosphorus application on arbuscular mycorrhizal fungi symbiosis in maize grown in western Kenya

A field study was carried out on a six-year-old on-farm field trial during long-rains season (April–August) 2003 to investigate the effect of improved fallow systems and phosphorus application on arbuscular mycorrhiza fungi (AMF) symbiosis in maize. The trial comprised of maize rotated with a fast growing leguminous Crotalaria grahamiana fallow and a non-leguminous Tithonia diversifolia fallow for 3 years followed by continuous maize. The experiment was randomized complete block design with three cropping (continuous maize, Crotalaria fallow and Tithonia fallow) systems and two phosphorus levels (0 and 50 kg P/ha). AMF colonization in maize roots, maize yield and macro-nutrients uptake were recorded. Phosphorus applications improved (P < 0.05) early (<8 weeks old maize) AMF colonization, nutrient uptake and maize yield in improved fallow systems. Greater differences due to phosphorus application were noted in maize in Tithonia fallow than in Crotalaria fallow. Following phosphorus application, a positive relationship existed between early AMF colonization and maize yield (r = 0.38), and phosphorus and nitrogen uptake (r = 0.40 and r = 0.43, respectively), demonstrating the importance of phosphorus fertilization in enhancing low-input technologies (improved fallows systems) in phosphorus deficient and acidic soils of western Kenya.     

Establishment of cryopreserved gene banks of European chestnut and cork oak

Cryopreservation of selected genotypes of European chestnut and cork oak was carried out in two laboratories in a project involving conservation of field collections. Plant material was selected on the basis of disease resistance (chestnut), growth habit, phytosanitary performance and cork quality (cork oak). The cryopreservation technique comprised of vitrification of shoot apices isolated from in vitro stock shoot cultures (chestnut) and somatic embryos (cork oak). Forty-three out of 46 chestnut genotypes assayed survived the freezing process, but only 63% recovered their capacity to produce new shoots. After completion of multiplication and rooting steps, the surviving shoots produced plants that were morphologically identical to those derived from non-supercooled material. All 51 cork oak genotypes withstood freezing and were able to produce new somatic embryos through a process of secondary embryogenesis. Multiplication and germination of the recovered embryos enabled production of plants that were morphologically identical to those derived from non-supercooled material. In light of the results obtained, long-term cryopreservation of these species is feasible, thereby ensuring conservation of valuable genotypes during field evaluation.     

Nutritional evaluation of “Braquiarão” grass in association with “Aroeira” trees in a silvopastoral system

This study aimed at evaluating the influence of a silvopastoral system (SPS) composed of “Aroeira” trees (Myracrodruon urundeuva) on the nutritional value of Brachiaria brizantha cv. Marandu forage grass over the rainy season. The experiment was conducted in the SPS located in the “Cerrado” biome in Lagoa Santa County, Minas Gerais state, Brazil, in the agricultural year of 2004–2005. It was evaluated the influence of “Aroeira”, whose density in the area was 140 trees/ha, on the following parameters of the B. brizantha cv. Marandu forage grass: forage mass harvest above stubble height, morphogenic attributes, bromatological composition and nutritional value. The effects of “Aroeira” trees on the micro-climatic conditions were also evaluated. The experiment adopted a randomized block design with five blocks (cutting seasons), two treatments (a shaded pasture—B. brizantha cv. Marandu shaded by M. urundeuva—and a pasture in full sun—B. brizantha cv. Marandu in full sun), and three replicates. The tree component, composed of the tree species M. urundeuva in the experimental density adopted, increased dry matter and crude protein of the forage mass harvest above stubble height, without affecting the concentration of neutral detergent fibre or acid detergent fibre, thus causing dry matter and organic matter in vitro degradability as well as effective degradability of the forage grass to remain the same as those obtained in full sun. Therefore, the results of this study show the possibility of using trees and grass to increase both animal production and environmental services.     

Site preference and occurrence patterns of <Emphasis Type="Italic">Picea jezoensis</Emphasis> and <Emphasis Type="Italic">Abies sachalinensis</Emphasis> on decayed logs in natural coniferous forests in Hokkaido,northern Japan

The objectives of this study were to investigate differences in the site preferences of seedlings of Picea jezoensis and Abies sachalinensis on decayed logs, and to examine the occurrence patterns of seedlings and saplings of the two species and whether they occur together or separately on logs. We characterized the habitats of 1–2-year-old seedlings of the two species on logs and examined the relationship of the two species on logs by growth stages in two plots. One plot had been disturbed about 50 years ago whereas the other had not for a long time. Although the thickness of moss and the litter layer in the habitats of 1–2-year-old seedlings were significantly different between the two species, the two species could occur together. In one study plot, seedlings and saplings of the two species occurred together. The initial occurrence pattern of the seedlings affected the occurrence patterns of the saplings on logs. The occurrence patterns of the seedlings and saplings of the two species on logs seemed to be affected by the abundance of seed trees. In the other study plot saplings of the two species occurred separately, but one species was not always competitively superior to the other species. Disturbance history affected the occurrence patterns of the saplings of the two species on decayed logs at the two study plots. Consequently, it is concluded that seed dispersal and the abundance of available logs, which are usually affected by disturbance, are significant factors in the natural regeneration of conifers in Hokkaido.     

Effects of water stress induced by sodium chloride and mannitol on proline accumulation,photosynthetic abilities and growth characters of eucalyptus (<Emphasis Type="Italic">Eucalyptus camaldulensis</Emphasis> Dehnh.)

The aim of this study was to investigate the biochemical, physiological and morphological responses of eucalypts to iso-osmotic salt and water deficit stress. Chlorophyll a, chlorophyll b, total chlorophyll (TC), total carotenoids, maximum quantum yield of PSII (F _v /F _m ), photon yield of PSII and non-photochemical quenching, in severely osmotic-stressed plantlets (−1.20 MPa) decreased significantly when compared to control plantlets, leading to low net photosynthetic rate (P _n ) and growth reduction. In addition, the photosynthesis and growth parameters of salt stressed plantlets declined to a greater degree than those cultivated in water-deficit conditions. On the other hand, the proline content of the osmotic-stressed leaves increased significantly, especially under iso-osmotic salt stress conditions. The TC content of iso-osmotic stressed leaves was significantly degraded, with low F _v /F _m , leading to P _n reduction and growth inhibition. Those parameters in salt stressed plantlets were significantly lower and to a greater degree than in plantlets subjected to water-deficit. The basic knowledge of biochemical, physiological and morphological changes in responses to iso-osmotic salt and water-deficit stresses will be further applied as effective indices for salt and water-deficit tolerant screening in large population of eucalyptus breeding program.     

Evapotranspiration estimation of <Emphasis Type="Italic">Platycladus orientalis</Emphasis> in Northern China based on various models

Platycladus orientalis is one of the most popular afforestation species and greening species for water management in arid and semi-arid regions of northern China. We applied various models to estimate and validate artificial P. orientalis forest evapotranspiration features with the goal of accurately estimating the water use of a P.orientalis plantation. The American Society of Civil Engineers Evapotranspiration–Penman–Monteith model(APM) and FAO56–Penman–Monteith model(FPM) are extensively applied for vegetation evapotranspiration estimation because their reliability has been validated by many scholars. The Priestley–Taylor model(PT) and Hargreaves model(HS) require only the daily maximum temperature,daily minimum temperature and solar radiation to estimate evapotranspiration and are thus widely applied to grasslands but not to forests. We used the Energy Balance Bowen Ratio(EBBR) system to validate the accuracy of the four models. The results indicated that:(1) Compared to the EBBR measurement annual value, APM was the most accurate, followed by FPM, and PT;(2) During the year, the accuracies of the four models varied. APM and FPM underestimated evapotranspiration during June, July and August, whereas PT and HS overestimated evapotranspiration during this period. In the rest of the year, the estimation accuracies were reversed;(3) An analysis of the possible reasons indicated that wind speed, air temperature and precipitation were the most important contributors.High temperatures were measured in June, July and August, which led to an overestimation by PT and HS because these two models only calculated the temperature and radiation without vegetation information. Underestimation also occurred when a low temperature was recorded. Though APM and FPM addressed both meteorological and vegetation factors, slight deviations still existed; and(4) The two models were modified based on EBBR-measured data. Relative humidity was introduced into PT, and parameter ‘‘A’’ in the HS estimation model was amended to1.41. The accuracy of the modified models significantly increased. The study highlighted the application, comparison and improvement of four models in estimating evapotranspiration and offers more approaches to assess forest hydrological functions.     

Integrated watershed management: evolution,development and emerging trends

Watershed management is an ever-evolving practice involving the management of land,water,biota,and other resources in a defined area for ecological,social,and economic purposes.In this paper,we explore the following questions:How has watershed management evolved? What new tools are available and how can they be integrated into sustainable watershed management? To address these questions,we discuss the process of developing integrated watershed management strategies for sustainable management through the incorporation of adaptive management techniques and traditional ecological knowledge.We address the numerous benefits from integration across disciplines and jurisdictional boundaries,as well as the incorporation of technological advancements,such as remote sensing,GIS,big data,and multi-level social-ecological systems analysis,into watershed management strategies.We use three case studies from China,Europe,and Canada to review the success and failure of integrated watershed management in addressing different ecological,social,and economic dilemmas in geographically diverse locations.Although progress has been made in watershed management strategies,there are still numerous issues impeding successful management outcomes;many of which can be remedied through holistic management approaches,incorporation of cutting-edge science and technology,and cross-jurisdictional coordination.We conclude by highlighting that future watershed management will need to account for climate change impacts by employing technological advancements and holistic,cross-disciplinary approaches to ensure watersheds continue to serve their ecological,social,and economic functions.We present three case studies in this paper as a valuable resource for scientists,resource managers,government agencies,and other stakeholders aiming to improve integrated watershed management strategies and more efficiently and successfully achieve ecological and socio-economic management objectives.     

A variance-covariance structure to take into account repeated measurements and heteroscedasticity in growth modeling

This study proposes a within-subject variance-covariance (VC) structure to take into account repeated measurements and heteroscedasticity in a context of growth modeling. The VC structure integrates a variance function and a continuous autoregressive covariance structure. It was tested on a nonlinear growth model parameterized with data from permanent sample plots. Using a stand-level approach, basal area growth was independently modeled for red spruce (Picea rubens Sarg.) and balsam fir [Abies balsamea (L.) Mill.] in mixed stands. For both species, the implementation of the VC structure significantly improved the maximum likelihood of the model. In both cases, it efficiently accounted for heteroscedasticity and autocorrelation, since the normalized residuals no longer exhibited departures from the assumptions of independent error terms with homogeneous variances. Moreover, compared with traditional nonlinear least squares (NLS) models, models parameterized with this VC structure may generate more accurate predictions when prior information is available. This case study demonstrates that the implementation of a VC structure may provide parameter estimates that are consistent with asymptotically unbiased variances in a context of nonlinear growth modeling using a stand-level approach. Since the variances are no longer biased, the hypothesis tests performed on the estimates are valid when the number of observations is large.     

Fatigue of structural plywood under cyclic shear through thickness I: fatigue process and failure criterion based on strain energy

The fatigue behavior of plywood specimens under shear through thickness was examined on the basis of strain energy to obtain common empirical equations for the fatigue process and failure criterion under various loading conditions. Specimens were cut from commercial plywood panels of 9-mm thickness. Loading conditions were set as follows: a square waveform at a loading frequency of 0.5 Hz, a triangular waveform at 0.5 Hz, and a triangular waveform at 5.0 Hz. Peak stress applied was determined to be 0.5, 0.7, and 0.9 of static strength, that is, stress levels of 0.5, 0.7, and 0.9. The stress-strain relationships were measured throughout the fatigue test, and the strain energy was obtained at each loading cycle. Loading conditions apparently affected the relationship between stress level and fatigue life. On the other hand, the relationship between mean strain energy per cycle and fatigue life was found to be independent of loading conditions. Mean strain energy per cycle obtained as the fatigue limit was 5.85 kJ/m³ per cycle. Assuming that the accumulation of strain energy is a fatigue indicator, the fatigue process and failure criterion for the plywood specimens under the three loading conditions were commonly expressed by the relationship between cumulative strain energy and loading cycles.