The production of lumber using chainsaws in Guyana

SUMMARY

The structure, conduct and performance, and the environmental impacts of the chainsaw lumber production sector in Guyana are investigated. Chainsaws are a highly mobile lumber technology that is used to rip or produce lumber within the forest. Chainsaw lumbering operations have become the dominant lumber producer for the domestic market. Production costs are only 53% of wholesale lumber prices. On a ms basis, chainsaw operations' net profit is 80% of the gross price paid for logs at sawmills and more than twice the profit of firms engaged in the harvesting and transportation of logs to sawmills. Sawmills recognize this cost advantage and are increasingly using chainsaws in the production of lumber.

The handling and transportation of chainsawn lumber within the forest is environmentally less damaging than log production. The log recovery rate is 10–15% for chainsaw operations, as compared to the sawmill average of 40–45%. Log residue from chainsaw operations is left within the forest which promotes faster forest regrowth, while that at sawmills is wasted. Chainsaw operations harvest immature trees, engage in the harvesting of selective species, over-harvest trees per unit area of land, and engage in frequent reentry of the forest. Because of these practices, the chainsaw lumber sector is not environmentally sustainable and will require regulation. Policies that follow a non-market solution will be required in regulation.     

On the gains of committing to inefficiency: Corruption, deforestation and low land productivity in Latin America

We present a new explanation and empirical evidence showing that rural subsidies to large farmers tend to be associated with low land productivity and excessive deforestation. We develop a lobbying model where wealthy farmers trade bribes or political contributions to government politicians in exchange for subsidies; farmers are able to tilt the terms of the bargaining game with policy makers in their favor by pre-committing to an inefficient choice of semi-fixed inputs. Government proneness to accept political contributions or bribes and its willingness to provide subsidies cause farmers to adopt inefficient modes of production as a mechanism to capture such subsidies. Our predictions are consistent with stylized facts on land use in Latin America, and suggest that subsidy schemes have been counterproductive—distorting and constraining development, and triggering excessive depletion of natural resources. We validate some of the predictions of the model through econometric analyses using a new data set for nine countries in Latin America.     

华南滨海小流域降雨入渗对地下水的补给分析

以华南滨海小流域——中山大学滨海水循环试验基地(试验基地)作为研究区,在对该流域地下水和雨水分别进行采样、实验分析的基础上,利用氯量平衡法(CMB)与地下水动态法计算了该流域的降雨入渗补给系数与给水度。研究发现,试验基地地下水主要受降雨补给,地下水埋深在雨季(4—9月)、旱季(10—3月)的变动范围大致为0～1.5 m与0～0.5 m。根据CMB计算结果,补给区、中间区雨季降雨入渗补给系数分别为旱季的1.3～1.6倍和1.3～2.0倍,且补给区大于中间区(M5井除外)。利用地下水动态法计算次降雨入渗补给系数,所得雨季、旱季的均值(7.6%和4.6%)与CMB计算结果(7.7%和5.3%)较为接近。给水度、雨强与入渗补给系数均存在一定的线性关系。将地下水埋深分别与降雨入渗补给量及潜水蒸发量进行多项式拟合对比,发现降雨入渗对地下水的最大入渗补给埋深约为2.3 m,当埋深为3.1 m时,地下水可获得最大净补给量。     

华南滨海小流域降雨入渗对地下水的补给分析

以华南滨海小流域——中山大学滨海水循环试验基地（试验基地）作为研究区,在对该流域地下水和雨水分别进行采样、实验分析的基础上,利用氯量平衡法（CMB）与地下水动态法计算了该流域的降雨入渗补给系数与给水度。研究发现,试验基地地下水主要受降雨补给,地下水埋深在雨季（4—9月）、旱季（10—3月）的变动范围大致为0～1.5 m与0～0.5 m。根据CMB计算结果,补给区、中间区雨季降雨入渗补给系数分别为旱季的1.3～1.6倍和1.3～2.0倍,且补给区大于中间区（M5井除外）。利用地下水动态法计算次降雨入渗补给系数,所得雨季、旱季的均值（7.6%和4.6%）与CMB计算结果（7.7%和5.3%）较为接近。给水度、雨强与入渗补给系数均存在一定的线性关系。将地下水埋深分别与降雨入渗补给量及潜水蒸发量进行多项式拟合对比,发现降雨入渗对地下水的最大入渗补给埋深约为2.3 m,当埋深为3.1 m时,地下水可获得最大净补给量。     

The role of the rural settlements in the Brazilian savanna deforesting process

Although the drivers of deforestation in Brazil are relatively well known, there is still limited understanding of the role of family farm-based rural settlements in land cover changes, particularly in the Brazilian savanna. This research aims to identify land use patterns within rural settlements and examine how they are influenced by regional dynamics. The study is based on GIS techniques and satellite image classification (Landsat 5-TM and RapidEye imagery), combined with geo-referenced fieldwork data in three different regions of the State of Goiás. The results reveal that the deforestation arrangement within the studied rural settlements is very similar to the deforestation found in the surrounding regions. As a positive outcome, the rural settlements have a higher share of remnant vegetation when compared to the surrounding areas, but this is still concentrated within legal reserves. We conclude that the changing patterns of rural settlement land cover are highly influenced by regional dynamics.     

Contamination of lead (Pb) in the coastal sediments of north and south of Iran: a review study

Coastal areas of Iran are heavily affected by urbanisation, industrialisation, and maritime activities. One consequence of this environmental pressure is the contaminants accumulation, as heavy metals, into the marine ecosystem. In this review, the coastal areas in the north and south of the country were assessed for lead (Pb) contamination of, one of the most toxic metals found in the environment. All studies conducted during 2006–2016 with at least 10 specimens that reported the mean and standard deviation of Pb were considered in this review. Heterogeneity between studies was assessed using the Q and I² statistics. The Pb mean concentration overall studies was estimated to be 21.88?µg/g (95% CIs: 16.25–27.50). Random effect model showed no statistical difference in mean Pb concentration levels between south and north coasts. However, the variability in Pb mean concentrations within southern coasts was considerable and statistically significant. Moreover, the Pb concentrations in the northern coasts of Persian Gulf and Oman Sea, in south of Iran, decreased in the following order Hormozgan > Khuzestan > Sistan-VA-Balluchestan > Bushehr while in the southern coasts of Caspian Sea, in north of Iran, decreased in the order Guilan > Mazandaran > Golestan.     

上海市沿海防护林下土壤养分、微生物及酶的典型相关关系

以上海市沿海防护林为研究对象,选择6种不同树种的防护林带,采集0～10、10～20、20～40、40～60cm四层土样为研究材料,运用典型相关分析法,对防护林地土壤养分因子、微生物因子和酶活性因子中每两组变量间的相关性进行了分析。结果表明：三组变量土壤养分、微生物、酶活性中,每两者之间均有显著的典型相关变量存在,而且基本能够代表变量总体相关信息;土壤养分和土壤微生物间的相关主要由全氮、速效磷含量与微生物生物量氮、微生物生物量碳和微生物生物量磷引起;土壤养分与土壤酶活性间的相关性主要由全氮、有效磷、水解氮含量与脲酶、蛋白酶活性的相关性引起;土壤微生物与土壤酶活性间的相关性主要是由微生物生物量氮、微生物生物量磷与脲酶、蛋白酶、碱性磷酸酶活性的相关性引起;不同林地不同土壤层次的养分、微生物及酶活性在各对典型变量上的聚集趋势可为防护林建设过程中的树种选择与土壤健康诊提供一定的依据。     

大兴安岭火烧迹地土壤动物的群落多样行

以大兴安岭地区不同年份火烧迹地土壤动物为研究对象,对火烧后不同恢复时间土壤动物群落多样性及相关指数的变化进行分析.结果表明,大型土壤动物的个体数、DIC指数、丰富度指数及优势度指数变化趋势均表现为火烧恢复初期迅速增加,然后缓慢增加并逐渐接近对比样地值;如果不考虑8 a迹地数据极大值的影响,中小型土壤动物的个体数、DIC指数、丰富度指数及优势度指数也大致呈现火烧恢复初期迅速增加,然后缓慢增长的趋势;在垂直方向上,大型土壤动物DIC指数、个体数及丰富度指数在0～5 cm最大,向上、向下减少,而中小型土壤动物的各项指数都是凋落物层最大,向下迅速减小;相关分析表明,大型和中小型土壤动物的个体数和丰富度指数与DIC指数都具有极高的相关性;群落相似性分析显示,各火烧迹地间土壤动物群落具有较高的相似性.图1表3参26     

The practice of coastal zone management in Portugal

The practice of coastal zone management in Portugal is very recent. Key issues and considerations about natural shoreline dynamics, main policy instruments, and lessons learned from the EU Demonstration Programmes on Integrated Coastal Zone Management in Portugal will be outlined in this paper in an attempt to understand how the practice of ICZM and its prospects are. Coastal zone management problems and their associated side effects, as well as national and international evolution patterns will be drawn. Some means of achieving better coastal zone management practices and ways of addressing some of its forefront issues are also identified. Special attention will go to erosion problems. The pressure induced by urban development and economic activities on coastal areas is increasing. Poor sediment availability combined with years of neglected management and over-exploitation of resources have had a negative impact, and there are many areas showing evidence of coastal erosion. There is a need to improve policies and instruments of coastal planning and management. Coastal zone management plans are being developed for the nine sectors of the continental Portuguese coast, providing a full analysis of coastal systems and a delimitation of uses in relation to the carrying capacity of the shoreline.     

Ten years of contested enforcement of the Forest Law in Salta,Argentina. The role of land-change science and political ecology

ABSTRACT

In this study, we present a critical account of the enforcement of the Forest Law in the Province of Salta, Argentina. We discuss whether the objectives of this law were accomplished and we analyze the role that some technical tools, coupled with specific theoretical approaches, could play in its future enforcement. We illustrate our analysis with data from a case study in the Chaco region of this Province. We identified, mapped and analyzed land claims by indigenous communities and small-scale agricultural producers, and large-scale land acquisitions, and we discuss how these two variables could be used to improve the technical accuracy and the social legitimacy of the zoning map required by the Forest Law. We conclude that a balanced combination of land-change science methods and political ecology can be useful to improve the fairness of decision-making processes and the sustainability of social-environmental governance in agricultural frontiers.     

A Contemporary Assessment of Change in Humid Tropical Forests

Abstract: In recent decades the rate and geographic extent of land‐use and land‐cover change has increased throughout the world's humid tropical forests. The pan‐tropical geography of forest change is a challenge to assess, and improved estimates of the human footprint in the tropics are critical to understanding potential changes in biodiversity. We combined recently published and new satellite observations, along with images from Google Earth and a literature review, to estimate the contemporary global extent of deforestation, selective logging, and secondary regrowth in humid tropical forests. Roughly 1.4% of the biome was deforested between 2000 and 2005. As of 2005, about half of the humid tropical forest biome contained 50% or less tree cover. Although not directly comparable to deforestation, geographic estimates of selective logging indicate that at least 20% of the humid tropical forest biome was undergoing some level of timber harvesting between 2000 and 2005. Forest recovery estimates are even less certain, but a compilation of available reports suggests that at least 1.2% of the humid tropical forest biome was in some stage of long‐term secondary regrowth in 2000. Nearly 70% of the regrowth reports indicate forest regeneration in hilly, upland, and mountainous environments considered marginal for large‐scale agriculture and ranching. Our estimates of the human footprint are conservative because they do not resolve very small‐scale deforestation, low‐intensity logging, and unreported secondary regrowth, nor do they incorporate other impacts on tropical forest ecosystems, such as fire and hunting. Our results highlight the enormous geographic extent of forest change throughout the humid tropics and the considerable limitations of the science and technology available for such a synthesis.     

Constructing change: The evolution of land and resource management in Alberta,Canada

Recognizing the limitations common to both centralized and privatized management regimes, institutionalized resource management is beginning to incorporate the knowledge and skills of local resource users, coupled with the enabling policies and legislation of state systems, to arrive at cooperative approaches to resource management. These varying and dynamic approaches to resource management have been compelled largely through the recognition of the limited capabilities of existing management systems to adapt effectively to ecosystem change and the evolving needs of resource users. These cooperative approaches to management should not, however, be considered an institutional end-point, but rather a phase in the perpetual transition of a social system; each unique in character and individually variable depending on the resource being managed, the political climate in which management occurs, as well as the differing strategies employed by resource users to enact institutional change. Drawing from the experiences of the Whitefish Lake First Nation of Alberta, Canada, this paper presents a brief overview of the evolution of resource management theory, grounded in the real-world formation of the Whitefish Lake First Nation — Province of Alberta Cooperative Management Agreement.     

Climate change and the cost of conserving species in Madagascar

We examined the cost of conserving species as climate changes. We used a Maxent species distribution model to predict the ranges from 2000 to 2080 of 74 plant species endemic to the forests of Madagascar under 3 climate scenarios. We set a conservation target of achieving 10,000 ha of forest cover for each species and calculated the cost of achieving this target under each scenario. We interviewed managers of projects to restore native forests and conducted a literature review to obtain the net present cost per hectare of management actions to maintain or establish forest cover. For each species, we added hectares of land from lowest to highest cost per additional year of forest cover until the conservation target was achieved throughout the time period. Climate change was predicted to reduce the size of species' ranges, the overlap between species' ranges and existing or planned protected areas, and the overlap between species' ranges and existing forest. As a result, climate change increased the cost of achieving the conservation target by necessitating successively more costly management actions: additional management within existing protected areas (US$0-60/ha); avoidance of forest degradation (i.e., loss of biomass) in community-managed areas ($160-576/ha); avoidance of deforestation in unprotected areas ($252-1069/ha); and establishment of forest on nonforested land within protected areas ($802-2710/ha), in community-managed areas ($962-3226/ha), and in unprotected areas ($1054-3719/ha). Our results suggest that although forest restoration may be required for the conservation of some species as climate changes, it is more cost-effective to maintain existing forest wherever possible.     

Developing indicators for assessing land-use sustainability in a tropical agro-ecosystem: The case of Sakaekrang watershed,Thailand

While the concept of sustainable land management is now widely accepted, there remains considerable scope for developing location-specific land-use indicators for sustainability evaluation. A study was conducted to investigate the indicators of land-use sustainability in the context of tropical agro-ecosystems using the case of Sakaekrang watershed, Thailand. The biophysical data were generated from Geographic Information Systems (GIs) and the socioeconomic data were collected through a field survey. In the light of sustainable land management objectives, a total of 32 criteria were considered in the analysis to determine land-use sustainability and identify indicators that best explain the sustainability level. About one quarter of the agricultural area in the watershed meets the sustainability threshold, indicating a substantial unstable area in the watershed. Among 11 indicators that showed a significant relationship with the computed land-use sustainability, land quality, source of farm income, and evapo transpiration were the most important.     

至2050年中国生态高值农业体系建设特征与目标

2010年6月7日,国家主席胡锦涛在两院（中国科学院、中国工程院）院士大会上针对农业科技明确指出：构建我国生态高值农业和生物产业体系,建成农业高值转化的产业体系。本文对＂生态高值农业＂进行论述。所谓生态,就是要体现农业既能为社会提供安全优质的农产品又能实现农业资源的永续利用,将农业纳入可持续发展的道路;所谓高值,就是要体现农业有很高的土地产出率、投入产出率、劳动生产率。因此,＂生态高值农业＂是集约化经营与生态化生产有机结合的现代农业。它以健康消费需求为导向,以提高农业市场竞争力和可持续发展能力为核心,兼有高投入、高产出、高效益与可持续发展的双重特性,是转变农业增长方式、提高农业综合生产能力的集中体现。     

渤海湾海岸带表层沉积物中黑碳的分布特征

在渤海湾西海岸潮间带、近海和主要河流采集了85个表层沉积物样品,对黑碳（BC）的质量分数及其分布规律进行了研究,并探讨了BC与沉积物粒度的关系。结果表明：（1）渤海湾海岸带表层沉积物中BC的平均质量分数为（0.65±0.42）mg·g^-1,占总有机碳的比例为16.8%±7.5%,均高于我国其它海岸带;（2）潮间带沉积物中BC的质量分数存在明显的南北分区差异（以天津港码头为界）,北区（0.92mg·g^-1）比南区（0.22mg·g^-1）平均高4倍以上;近海和河流样品BC的质量分数也有一定程度的＂北高南低＂趋势,表明BC在海岸带运移扩散的继承性,河流输入可能是主要途径;（3）潮间带沉积物粒度表现为＂北区细＂（以粘土质粉砂主）而＂南区粗＂（以砂为主）,反映两个区域的水动力条件和沉积环境不同,是造成BC质量分数区域差异的主要原因。     

三丁基锡对中国近海常见海洋微藻的毒性效应

研究三丁基氯化锡（TBT）对中国近海常见5种硅藻和甲藻（硅藻中丹麦细柱藻（Leptocylindrus danicus）、派格棍形藻（Bacilaria paxillifera）、聚生角毛藻（Chaetoceros socialis）,甲藻中微型原甲藻（Prorocentrum minimum）、简裸甲藻（Gymnodinium simplex））的毒性效应,考察了有机锡对浮游藻光合活性（Fv/Fm）、粒径、生长的影响。结果表明：派格棍形藻、聚生角毛藻、简裸甲藻的光合活性（Fv/Fm）受TBT影响较显著;微型原甲藻、丹麦细柱藻的光合活性受TBT影响较小。高质量浓度TBT胁迫下海洋微藻峰值粒径显著减小,低质量浓度TBT对峰值粒径影响不显著。低质量浓度TBT对派格棍形藻、聚生角毛藻、简裸甲藻、微型原甲藻均有较强的毒性作用,非检测毒性浓度（NDEC）分别为1.17、1.07、0.23、3.73μg.L-1,丹麦细柱藻对TBT具有很强耐受性,NDEC为112.62μg.L-1。     

鼎湖山针阔叶混交林生态系统水文过程研究

以鼎湖山针阔叶混交林（以下简称混交林）生态系统为研究对象，探讨了不同降水特征下森林生态系统水文过程，主要研究结果如下：（1）不同的降雨特征决定了不同的降雨过程和穿透雨过程，混交林生态系统穿透雨累积增加曲线与降水量的累积增加曲线变化是同步的；（2）2002年7月27日-28日特大暴雨最大降水量、最大穿透雨量分别为122．8nn和104．9mm,且穿透雨最大值出现的时间滞后于降水强度最大值出现的时间1h；（3）8月18日-20日特大暴雨，穿透雨量累积增加曲线与大气降水的累积增加曲线非常相似，且穿透雨最大值出现的时间略滞后与大气降水最大值出现的时间；（4）中雨时降水累积量达到最大值（59．6mm）与穿透雨累积量达到最大值（43．6mm）的时间一致；（5）树干流和地表径流量与大气降水量的累积变化曲线并不是完全同步的，在一定的降水量范围内，树干流量和地表径流量随着大气降水量的增加而增加；（6）无论是特大暴雨还是中雨发生时，即使在特大暴雨影响下，树干流（2．3～16．4mm）和地表径流（1．6～8．8mm）量都很小，系统具有很强的保水保墒能力；（7）混交林穿透雨强度变化过程基本取决于大气降水强度变化，树干流强度和地表径流强度数值很小且变化过程不明显。     

不同林龄马尾松（Pinus massoniana）人工林碳氮磷分配格局及化学计量特征

为了解长江上游低山丘陵区马尾松（Pinus massoniana）人工林生态系统的C、N、P分配格局及化学计量特征,本文采用时空互代的方法,在宜宾高县来复林区选取三种不同林龄（5年生幼龄林、14年生中龄林、39年生成熟林）,但立地条件相近、样地情况基本一致的马尾松（Pinus massoniana）人工林作为研究对象,对马尾松针叶、凋落物及土壤中的C、N、P含量及 w（C）？w（N）？w（P）化学计量特征进行测定和分析。结果表明,（1）C、N、P 含量均表现为针叶〉凋落物〉土壤,且在三个库之间差异显著;（2）林龄对针叶、凋落物、土壤的 C、N、P 及 w（C）？w（N）、w（C）？w（P）计量比均有显著影响。（3）土壤 C、N、P含量在成熟林中最高;针叶和凋落物的C含量在成熟林中最低,N、P含量则在中龄林中最高。（4）随林龄增加马尾松对N、P的利用效率降低,针叶、凋落物及土壤的w（C）？w（N）与 w（C）？w（P）均表现为下降。（5）马尾松针叶w（N）？w（P）比值在14.37~15.53之间,说明该地区马尾松人工林受N和P的共同限制,但林龄对N、P养分限制的影响不显著。为提高该区马尾松人工林的生产力,建议在人工林的抚育管理中要适当增加N肥和P肥,同时也可在马尾松人工林引入豆科固氮植物以提高地力。该研究将马尾松针叶、凋落物及土壤结合起来探究随林龄增长C、N、P养分元素的分配格局及化学计量特征的变化,有助于全面、系统地揭示马尾松人工林生态系统的养分循环,对指导马尾松人工林生产,调节和改善林木生长环境,提高系统的养分利用效率及林地生产力具有重要意义。     

粤北天井山国家森林公园三种林木在2008年特大冰雪灾害后的恢复

自2008年5月至2009年8月（共480 d）,对遭受2008年特大冰雪灾害的广东省北部天井山国家森林公园中受灾点（海拔700 m）和未受灾点（海拔550 m）的3种植物：樟树（Cinnamomum camphora）、荷木（Schima superba）和罗浮栲（CastanopsisFagaceae）进行对比实验。选择生理指标为：光系统II最大光化学量子效率（Fv/Fm）、比叶面积（SLA）、叶干物质重（LDMC）、单位叶面积氮含量（Na）、单位叶面积多酚含量（Phena）。研究结果显示：3受灾种Fv/Fm均无下降;受灾罗浮栲、荷木的其他各指标在300 d后已恢复至正常水平,而受灾樟树的各生理指标在300 d后仍显著低于正常（p〈0.1）;受灾樟树的生长模式由快速生长型改变为积累营养型。研究表明：（1）雪灾损伤对光系统II没有累积效果;（2）雪灾造成的冠层改变对中下林层的营养物质分配有影响;（3）作为人工栽培种的樟树,较自然生长种需要更长的灾后恢复期。