Support vector machines for tree species identification using LiDAR-derived structure and intensity variables

Tree species identification and forest type classification are critical for sustainable forest management and native forest conservation. Recent success in forest classification and tree species identification using LiDAR (light detection and ranging)-derived variables has been reported in many studies. However, there is still considerable scope for further improvement in classification accuracy. It has driven research into more efficient classifiers such as support vector machines (SVMs) to take maximum advantage of the information extracted from LiDAR data for potential increases in the accuracy of tree species classification. This study demonstrated the success of the SVMs for the identification of the Myrtle Beech (the dominant species of the Australian cool temperate rainforest in the study area) and adjacent tree species – notably, the Silver Wattle at individual tree level using LiDAR-derived structure and intensity variables. An overall accuracy of 92.8% was achieved from the SVM approach, showing significant advantages of the SVMs over the traditional classification methods such as linear discriminant analysis in terms of classification accuracy.     

Throughfall and its spatial variability in a temperate rainforest of simple structure

There are few throughfall data from southern hemisphere closed-forest, and none from Tasmanian callidendrous cool-temperate rainforest, which has a simpler structure than most primary rainforests. We determined throughfall, measured its local spatial variation, and tested its relationships with rainfall, rainfall intensity, wind speed, canopy dryness, canopy cover, and other structural variables in a cool-temperate callidendrous rainforest in Tasmania. Eighty-two percent of the precipitation was measured as throughfall, which occurred after 2.3 mm of rain fell on dry canopies. The cumulative rainfall in 25 randomly located funnel rain gauges on the forest floor varied from 160 to 567 mm. Canopy cover and other structural variables did not predict the spatial pattern of throughfall. While throughfall in rainfall events was related to rainfall amount and intensity, wind speed did not affect throughfall as a percentage of rainfall. Percentages of throughfall to rainfall over 100 for many low rainfall events may indicate a contribution of fog drip to precipitation on the forest floor. The high local spatial variability in throughfall indicates the mean moisture conditions on the forest floor may not be a good indicator of the potential for localised fire damage.     

利用GLASS LAI数据分析1982-2012年亚马逊热带雨林变化

利用1982-2012年的GLASS LAI数据,结合世界粮农组织(FAO)2000年发布的全球生态环境分类图,对亚马逊热带雨林31年的植被变化进行了综合分析,采用点与面相结合的分析方法,全面地反映雨林植被的变化情况。不同于过去研究中固定研究范围或直接研究整个南美洲区域,本文采用动态静态边界相结合的方法,在考虑热带雨林动态范围变化的同时也强调研究区域的内部变化。结果显示,亚马逊热带雨林叶面积指数在31年中整体呈现波动变化,进入2000年以后,热带雨林范围内平均叶面积指数先下降后增加,整体相对稳定。在空间分布上,由于人类毁林开荒,巴西境内的热带雨林以及热带雨林部分边缘地带的叶面积指数在31年中明显下降,热带雨林东南边界持续收缩;除此之外,雨林内部的叶面积指数波动上升,这是受到全球气候变暖的影响。结果与过去的研究进行对比,具有较好的一致性。研究论证了利用具有中国自主知识产权的GLASS LAI数据可以进行长时间序列大尺度的地表植被状况监测。     

Amazon Fan biomarker evidence against the Pleistocene rainforest refuge hypothesis?

Ocean Drilling Program Leg 155 Site 942 on the Amazon Fan is an ideal location for monitoring palaeoclimatic changes within a significant proportion of the Amazon Basin. We present n‐alkane δ¹³C and taraxerol and laevoglucosan concentration records from this site covering the last 38 ka. The entire n‐alkane δ¹³C record is constrained between ?31‰ and ?34‰, which is well within the isotopic range occupied by C₃ vegetation. The concentration and relative abundance of taraxerol, a mangrove indicator, varies by over an order of magnitude, but seems to have had no effect on the n‐alkane δ¹³C record. The laevoglucosan concentrations are extremely low during the last glacial period, suggesting a relatively low occurrence of forest fires. Laevoglucosan concentrations are highest between 13.5 and 12.5 ka, suggesting an increased incidence of Amazon forest fires at the very end of the Younger Dryas. These records, combined with previously published pollen records from Site 932, reveal no evidence for massive incursions of grasslands into Amazonia during the last glacial period, despite evidence of reduced outflow of the Amazon River indicating more arid conditions. We therefore suggest that savannah encroachment, as proposed by the Pleistocene refuge hypothesis, can be refuted as an explanation for high species endemism within the Amazon Basin, and alternative explanations are required. Copyright © 2012 John Wiley & Sons, Ltd.     

Streamflow response to native forest restoration in former Eucalyptus plantations in south central Chile

Global increases in intensive forestry have raised concerns about forest plantation effects on water, but few studies have tested the effects of plantation forest removal and native forest restoration on catchment hydrology. We describe results of a 14-year paired watershed experiment on ecological restoration in south central Chile which documents streamflow response to the early stages of native forest restoration, after clearcutting of plantations of exotic fast-growing Eucalyptus, planting of native trees, and fostering natural regeneration of native temperate rainforest species. Precipitation, streamflow, and vegetation were measured starting in 2006 in four small (3 to 5 ha) catchments with Eucalyptus globulus plantations and native riparian buffers in the Valdivian Coastal Reserve. Mean annual precipitation is 2500 mm, of which 11% occurs in summer. Streamflow increased, and increases persisted, throughout the first 9 years of vigorous native forest regeneration (2011 to 2019). Annual streamflow increased by 40% to >100% in most years and >150% in fall and summer of some years. Streamflow was 50% to 100% lower than before treatment in two dry summers. Base flow increased by 28% to 87% during the restoration period compared to pre-treatment, and remained elevated in later years despite low summer precipitation. Overall, these findings indicate that removal of Eucalyptus plantations immediately increased streamflow, and native forest restoration gradually restored deep soil moisture reservoirs that sustain base flow during dry periods, increasing water ecosystem services. To our knowledge this is the first study to assess catchment streamflow response to native forest restoration in former forest plantations. Therefore, the results of this study are relevant to global efforts to restore native forest ecosystems on land currently intensively managed with fast-growing forest plantations and may inform policy and decision-making in areas experiencing a drying trend associated with climate change.     

Rainfall interception from a lowland tropical rainforest in Brunei

Results from a programme of throughfall measurements in a lowland tropical rainforest in Brunei, northwest Borneo, indicate that interception losses amount to 18% of the gross incident rainfall. The high annual rainfall experienced by the study area results in annual interception losses of around 800 mm, which may result in total annual evapotranspiration losses significantly higher than in other rainforest locations. An improved version of Gash's analytical interception model is tested on the available data using assumed values for the “forest” parameters, and is found to predict interception losses extremely well. The model predictions are based on an estimated evaporation rate during rainfall of 0.71 mm h⁻¹. This is significantly higher than has been reported in other tropical studies. It is concluded that these results are distinctive when compared with previous results from rainforests, and that further, detailed work is required to establish whether the enhanced evaporation rate is due to advective effects associated with the maritime setting of the study area.     

Groundwater fluctuations and footslope ferricrete soils in the humid tropical zone of southern Cameroon

This paper discusses the relationship between the differentiation of ferruginous accumulations and the variable water saturation of footslope soil patterns. An analysis of the slope morphology of a typical hill in the forest zone of southern Cameroon and a seasonal survey of the levels of groundwaters, springs and rivers were considered in relation to the petrology of different soil patterns. The study site is a tabular hillock whose slopes present a progressive development from steep to gentle slopes. The variable residence time of water within the soil, creating an alternation of reducing and oxidizing conditions, affects soil chemistry, structure and lateral extension of the soil patterns. The ferruginous soil patterns, being formed on the footslopes, gradually increase in extent with decreasing slope angle and the relative rise of the groundwater level. The steep footslopes, where groundwater has a shorter residence time, show a soft mottled clay pattern, restricted to the bottom part of the slope. The moderate footslopes exhibit a deep permanent and a temporary perched groundwater table. The latter, with its regular capillary fringe, contributes to more reducing conditions within isolated domains in the soil patterns, and thus to the alternation with oxidizing conditions, generating a continuous hard soil pattern (massive carapace). The more gently dipping footslopes exhibit groundwater levels near the surface and also a significant amplitude of groundwater fluctuation. Iron, previously accumulated in moderate footslope patterns, is reduced, remobilized, and leached. The soil patterns formed develop into a variegated carapace, more extended along the slope, containing less iron, but nevertheless more hardened, due to the important fluctuations of the groundwater table. These patterns are limited to the zone of groundwater fluctuation and deteriorate as the water fluctuation zone recedes. Copyright © 2005 John Wiley & Sons, Ltd.     

Precipitation interception in Australian tropical rainforests: I. Measurement of stemflow,throughfall and cloud interception

Methods for measuring throughfall, stemflow and, hence, interception in the tropical rainforests of the Wet Tropics region of North Queensland, Australia, were tested at three sites for between 581 and 787 days. The throughfall system design was based on long troughs mounted beneath the canopy and worked successfully under a range of rainfall conditions. Comparison of replicated systems demonstrated that the methodology is capable of capturing the variability in throughfall exhibited beneath our tropical rainforest canopies. Similarly, the stemflow system design which used spiral collars attached to sample trees worked well under a range of rainfall conditions and also produced similar estimates of stemflow in replicated systems. Higher altitude rainforests (>1000 m) in North Queensland can receive significant extra inputs of water as the canopy intercepts passing cloud droplets. This additional source of water is referred to as ‘cloud interception’ and an instrument for detecting this is described. The results obtained from this gauge are compared with cloud interception estimates made using a canopy water balance method. This method is based on stemflow and throughfall measurements and provides an alternative means to fog or cloud interception gauge calibration techniques used in the literature. Copyright © 2007 John Wiley & Sons, Ltd.     

THE FLORISTIC CHARACTERISTICS OF THE TROPICAL RAINFOREST IN XISHUANGBANNA

ＴＨＥ ＦＬＯＲＩＳＴＩＣ ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳ ＯＦ ＴＨＥ ＴＲＯＰＩＣＡＬ ＲＡＩＮＦＯＲＥＳＴ ＩＮ ＸＩＳＨＵＡＮＧＢＡＮＮＡ ＺｈｕＨｕａ（朱华）（ＸｉｓｈｕａｎｇｂａｎｎａＴｒｏｐｉｃａｌＢｏｔａｎｉｃａｌＧａｒｄｅｎ，ｔｈｅ...     

A 23,000-yr pollen record from Lake Euramoo, Wet Tropics of NE Queensland, Australia

A new extended pollen and charcoal record is presented from Lake Euramoo, Wet Tropics World Heritage rainforest of northeast Queensland, Australia. The 8.4-m sediment core taken from the center of Lake Euramoo incorporates a complete record of vegetation change and fire history spanning the period from 23,000 cal yr B.P. to present. The pollen record is divided into five significant zones; 23,000–16,800 cal yr B.P., dry sclerophyll woodland; 16,800–8600 cal yr B.P., wet sclerophyll woodland with marginal rainforest in protected pockets; 8600–5000 cal yr B.P., warm temperate rainforest; 5000–70 cal yr B.P., dry subtropical rainforest; 70 cal yr B.P.–AD 1999, degraded dry subtropical rainforest with increasing influence of invasive species and fire.The process of rainforest development appears to be at least partly controlled by orbital forcing (precession), though more local environmental variables and human activity are also significant factors. This new record provides the opportunity to explore the relationship between fire, drought and rainforest dynamics in a significant World Heritage rainforest region.