Determining the susceptibility of Eucalyptus nitens forests to Coryphodema tristis (cossid moth) occurrence in Mpumalanga,South Africa

The cossid moth, Coryphodema tristis was first noted on Eucalyptus nitens trees in Mpumalanga province, South Africa during July 2004. Currently, the moth poses a major threat to commercial forestry in the country. In this study, selected climatic and topographical variables were used to model the susceptibility of E. nitens forests to cossid moth occurrence, thereby providing insight into the variables that may influence the occurrence and spread of the moth. A zigzag sampling technique was used to survey 5316 ha of E. nitens forests for the presence or absence of the moth. The random forest classification algorithm was then used to model the relationship between the climatic and topographical variables and the occurrence of the cossid moth. Results indicate that four variables that included elevation, maximum temperature for September, maximum temperature for April and the median rainfall for April best explained the presence or absence of C. tristis with an overall accuracy of 82% and a kappa value of 0.63. Partial dependence plots indicated that the areas that have a maximum temperature greater than 23°C in September and 22°C in April are likely to be infested by the cossid moth. The results from this study provide a robust and accurate spatial framework to assist forest managers in focussing their existing monitoring and control efforts to specific E. nitens forested areas that are highly susceptible to C. tristis infestations.     

米草属植物在中国海岸带的分布现状

结合遥感调查、现场定位,辅以文献检索、函调、电子邮件、电话等调查方式分析了4种米草属植物自引种以来在我国海岸带分布的历史及现状,结果表明,因人类围垦活动、大米草(Spartina anglica)的自身退化以及与互花米草存在生态位竞争关系,大米草在全国海岸带的分布面积不足16hm2,呈退化趋势。大绳草(Spartina cynosuriodes)尚未在实验地种植,狐米草(Spartina patens)仅在苏北、天津市的部分区域有少量种植。这两种米草没有对本土生态系统造成入侵威胁。互花米草(Spartina alterniflora)自1979年引种以来在全国海岸带被广泛种植,后经自然扩散,目前面积已达34451 hm2。结合我国的海岸带特征与互花米草的生态位,可以把其生长区域明显分为三部分:一是福建省福鼎市以南的海岸带滩涂,可能与红树林潜在的生态位竞争有关系;二是河口区域,如在长江口的崇明东滩,互花米草与本土植物表现出明显的竞争关系;三是在其他滩涂区域,该物种可能对本土生态系统造成一定程度的影响,在某些区域可能已经表现出一定的入侵性,但是其带来的促淤造陆、保滩护岸等巨大的生态效益也不应忽视。由于我国海岸带地质地貌类型复杂,互花米草在不同区域表现出不同的定植和扩散能力,与本土植被的竞争关系也明显不同。因此,在评价互花米草所造成的生态后果时,应从不同的角度出发进行全面、系统、客观、公正地评价。     

基于CRNBR物候算法的西双版纳橡胶成林提取及时空变化研究

基于西双版纳2014年和2018年旱季Landsat-8 OLI遥感影像,利用橡胶林落叶-新叶萌生期内归一化焚烧指数变化率（CR_NBR）算法,运用当年新叶萌生期植被分布（NDVI）与海拔数据（ASTER GDEM）进行掩膜提取,分别获取了2014年和2018年西双版纳橡胶成林种植面积,基于ArcGIS 10.5平台分析了橡胶成林时空格局和种植面积增减变化。结果表明： ① 西双版纳橡胶林主要分布于南部水热条件较好、中低海拔的橡胶种植适宜区。景洪市的橡胶林面积最大,其次是勐腊县,勐海县最小。集中分布于景洪市的勐龙镇、允景洪街道和嘎洒镇;勐腊县的关累镇、勐棒镇和勐满镇;② 西双版纳及其下辖一市两县2014-2018年橡胶林种植面积总体呈现下降趋势,减幅为17.27%。其中,勐腊县的减幅最大为19.10%,勐海县减幅最小,仅2.70%。③ 橡胶林持续种植区主要在景洪市勐龙镇、嘎洒镇和景哈镇等,勐腊县的关累镇、勐棒镇和勐腊镇等;橡胶林种植增加区主要集中在景洪市勐龙镇、嘎洒镇和允景洪街道,勐腊县关累镇、勐腊镇和勐伴镇,勐海县打洛镇;橡胶林种植减少区主要在景洪市勐养镇、嘎洒镇和勐龙镇,勐腊县勐棒镇、勐腊镇和勐伴镇,本研究可为西双版纳橡胶林种植现状特征提供了新的认识。     

An updated delineation of stand ages of deciduous rubber plantations during 1987-2018 using Landsat-derived bi-temporal thresholds method in an anti-chronological strategy

Timely and accurately monitoring stand ages of deciduous rubber plantations is of great importance for ecological studies and plantations management. The re-establishment of rubber plantations usually experiences a short period (several years) of land clearance and transplantation of rubber seedlings, along with a noticeable landscape change from well-grown forest to bare land and sparse vegetation in situ. With Landsat times series (LTS) data of four commonly-used vegetation indices (VIs), namely the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Normalized Difference Moisture Index (NDMI), and Normalized Burn Ratio (NBR), and three non-visible spectral bands, i.e. the near-infrared (NIR) and shortwave-infrared (SWIR1/2), in this study, an approach by combining the inter-annual defoliating and foliating features of rubber trees and the intra-annual landscape changes of rubber plantations was presented to detect and map stand ages of deciduous rubber plantations in an anti-chronological manner across Xishuangbanna between 1987 and 2018, one of the most intensive regions of deciduous rubber plantations within the tropics. The approach highlighted the repeated distribution of newly-cleared and replanted plot (NCRP) of rubber seedlings due to rubber management. It applied the bi-temporal VIs thresholds of zero of NBR and NDMI during the defoliation to foliation phases to delineate the stand ages of deciduous rubber plantations at an interval of five years, by combining a Landsat-based rubber map in 2018 and 32-year NCRPs as well as quadri-classified age-groups and seven sub-categories (i.e. ≤5 as infantile rubber plantations (IRP), 6–10 as young rubber plantations (YRP), 11–15 and 16–20 as mature rubber plantations (MRP), 21–25, 26–30, and ≥31 years as old rubber plantations (ORP)). The results showed that the areas of IRP, YRP, MRP, and ORP were 19.1 km², 817.1 km², 1681.7 km², and 573.7 km² in 2018, respectively. Spatially, the YRP are mainly around the outskirts of two county-level administrative centers (Jinghong and Mengla), while ORP primarily distributed along main roads. Nearly 53.9% of ORP, 51.8% of IRP, 47.3% of MRP and 46.3% of YRP were in Jinghong City, and Mengla County had 50.5% of YRP, 48.8% of MRP, 42.4% of IRP and 36.3% of ORP. This study demonstrates that the bi-temporal VIs thresholds method (i.e. NBR_defoliation <0, NDMI_defoliation <0, NBR_foliation <0, and NDMI_foliation <0) have great potential for detecting stand ages of deciduous rubber plantations.     

Converting tropical rainforest to forest plantation in sabah,malaysia. Part II. Effects on nutrient dynamics and net losses in streamwater

Streamwater chemistry was monitored for five years in six streams in a paired catchment experiment in Mendolong, Sabah, Malaysia, comparing the effects of different ways to establish forest plantations with Acacia mangium. At the start of the monitoring in 1985 three catchments were covered with selectively logged rain forest (W4-W6) and three with secondary vegetation after forest fire (W1-W3). The treatments were: (1) clearing of secondary vegetation, burning and planting (W1 and W2); (2) clear-felling, crawler tractor extraction, burning and planting (W5); and (3) clear-felling, manual extraction, no burning and planting (W4). W3 and W6, with no treatment, were monitored as control catchments. Reference monitoring at all streams was for two years and was followed by treatments which lasted for nine months before the full establishment of a new vegetation cover. This paper covers monitoring for a further 2.5 years. The soil types of the catchments were Orthic Acrisol in W3, Gleyic Podsol in W6 and a mix of both soil types in the other catchments. The effect of treatments on streamwater chemistry was clear at both base- and stormflows. Concentrations of major plant nutrients (N, P and K.) became positively correlated to streamflow during treatments. The response of leaching from slash at clear-felling was fast and larger from the clear-felling residues (W4 and W5) than the cleared secondary vegetation (W1 and W2). The intense response to burning was more marked. The stormflow period mean nutrient concentrations were approximately 10-fold for N and K and 10-100 fold for P after burning compared with baseflow mean concentrations over the same period. Significant differences in baseflow concentrations in treated streams generally lasted one year for most elements, but elevated concentrations were still detectable after three years. The first large pulse of leaching was related to mineralization after tree-felling and particularly burning. The longer lasting elevated concentrations in baseflow were associated with the loss of weathering products. The amounts of nutrients lost, calculated by regression analysis as the effect of treatment compared with control, were found to be higher with the degree of vegetation killed and with increased soil disturbance. Consequently, normal forestry practices, with crawler tractor extraction and burning before planting, created the largest leaching losses. The total calculated effect of losses in total N, P and K were (i) W1 + W2 0.5, 1.8, 83.9; (ii) W4 0.8, 0.8, 105.6; and (iii) W5 1.3, 1.3, 189.4 kg ha^?1 for the period of 33 months during and after treatment. With normal forestry practice using crawler tractors and with burning before planting (W5), the treatment-induced loss of K was equivalent to 86% of the content of easily decomposed parts of the biomass (leaves, twigs, fine roots and ground vegetation) of the old forest, or larger than K removed by harvest. Exhaustion effects of lowered leaching after repeated burning (forest fire and pre-planting fire) was observed for several elements, indicating possible nutrient deficiencies.     

川西亚高山人工针叶林生态恢复过程的种群结构

研究了川西米亚罗亚高山人工针叶林70a恢复过程中不同恢复级段云杉种群结构的变化并比较了与原始林的差异。研究结果表明，所调查的人工云杉林有两个快速生长(平均高度和胸径)时期：一是20～30林龄人工林，年均高生长量达到0．428m，年均胸径增长量为0．57cm；二是50～70林龄人工林，年均高生长量达到0．364m，年均胸径增长量为0．431Cln。与天然原始林相比，人工林苗木的高度级宽幅(10／21)和胸径宽幅(20／36)都较小，下层更新苗木少。50林龄以前的人工林年龄均为同一龄级，70林龄后才有少量的更新幼苗，种群的年龄结构很不合理，说明人工云杉林生态功能的恢复是一个十分漫长的过程，需要对其采取相应的调控措施。     

桉树人工林与杉木林、毛竹林土壤理化性质对比研究

在对永安市尾巨桉人工林、杉木林、毛竹林野外调查取样和室内实验分析基础上,对11年生尾巨桉林、3年生尾巨桉林与杉木林和毛竹林的土壤理化性质进行全面比较．结果表明,3年生尾巨桉林各层土壤中的土壤有机质、全氮和碱解氮、全磷和速效磷、全钾和速效钾含量大多低于其他3种林地,反映了处于速生期的桉树对养分的旺盛需求和消耗;并且,速生期桉树还会造成一定程度的土壤表层粘粒下移和酸化;但随着桉树种植年限的增加,这种状况有所改善．在此基础上,提出变炼山全垦为块状整地,速生期人工施肥,延长轮伐期,实行间种、轮栽并适当休闲养地,提高桉树人工林生物多样性等措施,以实现桉树人工林土壤养分平衡与生态系统的良性循环．     

Soil Carbon and Nutrient Accumulation under Forest Plantations in Jharkhand State of India

The decrease and degradation of the tropical forests affect not only the production of timber but also the global environment in a large scale. The ability of soil to sustain and its supply of nutrients to a growing forest are controlled by a complex of biogeochemical processes. The purpose of the present study aims to assess the degraded forest fringe areas, to promote plantations of various types and to evaluate their impacts on the soil nutrients and carbon content accumulation. The soil organic carbon (SOC) and nutrient content were evaluated and compared between plantations of mixed native species (MNS), some native tree species as Shorea robusta, Dalbergia sissoo, Dendrocalamus spp., certain agro‐forestry species and some exotic varieties. The impacts of the plantations on the SOC and the nutrients were firstly analyzed through comprehensive chemical analyses and the results were compared with the soil samples collected prior to plantation forestry. Significant changes were observed in SOC content, in nutrients, and in amounts of exchangeable cations. Soil carbon levels were highest under the MNS, Dendrocalamus and Tectona grandis stands and lowest under D. sissoo and Terminalia arjuna. Total N showed highest levels under Dendrocalamus and Pongamia pinnata and significantly higher in stands of native species; lowest total N level was observed in D. sissoo plantations. The C/N ratios of the soil varied between 9.2 and 13.5 among the exchangeable cations. Ca²⁺ recorded the maximum levels and Na⁺ showed the lowest levels.     

地缘政治经济背景下中老-中越边境地区橡胶林时空扩展特征研究

国家间地缘政治经济关系正在驱动区域土地利用变化,边境地区首当其冲。20世纪90年代以来,全球橡胶市场的强劲需求以及中南半岛与域外国家40多个地缘经济合作机制的实施,引起了包括中国与老挝(以下称“中老”)-中国与越南(以下称“中越”)边境地区橡胶林扩展种植在内的显著土地利用变化。基于此,利用Landsat影像构建的橡胶林落叶-新叶萌生期内植被-水分指数(Renormalized Vegetation Index, RNVI)组合算法,获取中老-中越边境地区1990年代以来中老、中越地缘政治经济关键节点的橡胶林种植信息,进而揭示中老、中越地缘政治经济关系对其边境地区橡胶林扩展的影响及其国别差异。结果表明:(1)在“替代种植”与边境农林合作等地缘政治经济影响下,中老-中越边境地区橡胶林种植面积由1992年的995.5 km²增加至2018年的5537.7 km²,增长近4.6倍,且呈明显的沿边性和跨境性;(2)随着中老磨憨-磨丁口岸开通、中老北部九省合作机制构建等,1992—2018年,中老边境沿线30 km缓冲区内橡胶林种植面积从244.7 km...