勐海热带雨林地区土壤侵蚀动态变化研究

为了探究滇南热带雨林区土壤侵蚀状况,以勐海县为研究区,基于2009年和2016年Landsat影像数据、DEM、降雨、土壤等数据,利用通用土壤侵蚀方程（USLE）对勐海县土壤侵蚀动态变化进行定量分析。结果表明：2009年、2016年勐海县土壤侵蚀模数分别为812 t/（km²·a）和783 t/（km²·a）,土壤侵蚀主要以微度和轻度侵蚀为主,土壤侵蚀向两极化发展;从区域空间分布来看,土壤侵蚀呈现东南、西北高,东北、西南、中部低的分布状态;不同土地利用类型水土保持效益顺序为建设用地>林地>水域>水田>旱地>园地。     

榕树在西双版纳热带雨林中的地位和综合利用价值

对榕树在热带雨林生态系统中的地位进行了研究和分析 ,并对聚果榕、鸡嗉果榕的成熟果实进行了成分分析。结果表明 :除糖、脂肪、蛋白质等营养成分外 ,聚果榕、鸡嗉果榕的榕果均含有丰富的矿质元素和多种人体必需氨基酸 ,维生素 C的含量特别丰富 ,分别为 0 .68mg· g-1和 0 .2 8mg· g-1。矿质元素中 ,以钾、钙、镁的含量最为丰富。榕果能为食果动物提供全面而均衡的营养成分 ,榕果具有数量多、产量高、一年四季均挂果的特点 ,是热带雨林生态系统食物链的重要组成部分。     

Influence of forest clearing methods on nutrient uptake of some tropical food crops

The adverse effects of forest clearing on crop yield have often been directly ascribed to decline in soil fertility. However, the effect of various forest clearing methods on crop nutrient uptake as reflected by the content in the leaf tissues has been the subject of few scientific investigations. A study to determine the effect of forest clearing on nutrient content of some arable crops was, therefore, carried out in the tropical rainforest of south-western Nigeria. Three forest clearing methods—mechanical, semi-mechanical and manual clearing—were used, while maize, cowpea, and cassava were the test crops. Nutrient content in the tissues of these crops was assessed by sampling maize ear leaves at silking, youngest mature leaves (YML) of cowpea at flowering and YML of 3-month-old cassava for analysis. Correlation analysis was carried out to establish the relationship between nutrient content and crop yield. The method of forest clearing had no significant effect on the nutrient content of maize and cowpea during the first cropping cycle. However, nutrient content of maize in the manually cleared plots was higher than those in the semi- and mechanically cleared plots for all elements analyzed except Mg. Nitrogen content of cowpea was much higher than that of maize. Except for P and K, the nutrient content of cassava was not markedly different among the forest clearing methods. Calcium and P content in the leaves of maize and cassava varied inversely with their levels in the soil, implying that crop uptake could have accounted for the differences in their availability within the soil. Nitrogen, P and K had significant positive correlations with maize yield (r = 0.77, 0.89, and 0.71). Potassium content also had significant positive correlation with cassava root yield (r = 0.69). This is not surprising because compared with other crops, cassava requires large amounts of K for starch formation and root development. It is concluded that differences observed in crop yields under different forest clearing methods are a function of nutrient uptake and availability within the soil. However, the uptake of some nutrients does not seem to be determined by the level of soil availability alone. This study was supported with a research grant from the International Foundation for Science (IFS), Sweden.     

Deadwood in New Zealand's indigenous forests

We present the results of a systematic, unbiased national survey of deadwood volume and biomass in New Zealand's remaining indigenous forests based on an 8-km grid of 894 permanent plots. New Zealand's old growth evergreen temperate forests are largely comprised of long-lived, slow-growing tree species typically growing in cool, humid conditions; collectively these conditions are thought to promote accumulation of high deadwood stocks. We estimated deadwood biomass and volume in New Zealand's forests and compared these stocks with published values from other broadleaved evergreen temperate forests. Mean deadwood biomass in New Zealand was 54 Mg ha⁻¹ but ranged across plots from 0 to 550 Mg ha⁻¹. Mean deadwood volume was 158 m³ ha⁻¹ and ranged across plots from 0 to 1890 m³ ha⁻¹. Fallen logs accounted for 63% of total deadwood volume and 65% of total deadwood biomass, with standing dead trees being the remainder. Each piece of deadwood was classified into one of three broad decay classes and >40% of deadwood was fallen logs of the intermediate decay class. Deadwood biomass and volume varied 1.8- and 1.9-fold, respectively, among forest types and was greatest in broadleaved forests, dominated by Weinmannia racemosa (Cunoniaceae), Metrosideros umbellata (Myrtaceae) and Metrosideros robusta, and broadleaf-Nothofagus (Nothofagaceae) forests supporting the large tree species Nothofagus fusca. Deadwood biomass and volume were least in broadleaf-conifer admixtures. We used structural equation models to determine whether deadwood biomass could be predicted from climate and environment (vapor pressure deficit, elevation and slope), live tree biomass, forest composition (captured by two ordination axes), wood density of live trees, and tree size (a proxy for stand age). The model that best fit the data retained only vapor pressure deficit, live tree biomass and the first ordination axis as predictors of deadwood biomass. However, this model predicted just 2.4% of the variation in deadwood biomass, suggesting that additional factors not captured by this dataset, such as disturbance dynamics, may control deadwood abundance. Comparisons with other temperate and tropical forests did not support the hypothesis that New Zealand's cool temperate rainforests support higher than expected biomass or volume of deadwood.     

热带雨林林冠层和林下层生物捕食水平的调查

指出了热带雨林作为地球上生物多样性最为丰富的生态系统,有着复杂的物理结构和生物交互。林冠层和林下层由于接受光照等条件不同,造成了不同的微环境。在不同的微环境里,蚂蚁和鸟类等捕食者对植食性昆虫的捕食水平可能有所差异。利用绿色橡皮泥制作模拟自然状态下的毛毛虫,探究了其在热带雨林林冠和林下层的被捕食的水平的差异。结果显示:林下层的捕食水平显著高于林冠层,并且蚂蚁有着显著高于鸟类的捕食水平。这说明热带雨林的林冠层资源丰富、结构复杂,在为植食性昆虫提供大量食物资源的同时也能为其提供庇护从而躲避天敌,尤其是鸟类的捕食。     

尖峰岭热带山地雨林林窗土壤甲烷通量研究

以海南岛尖峰岭热带山地雨林因2012年左右台风干扰形成的林窗样地为研究对象,开展土壤甲烷通量的原位观测试验,测定林窗和林下凋落物质量、土壤温度、土壤含水量、酶活性及其他土壤理化指标,运用最佳结构模型研究土壤甲烷通量与环境因子的关系,分析林窗土壤甲烷通量变化特征、影响因素及其与林下的差异。结果表明:海南岛尖峰岭热带山地雨林表现为甲烷吸收,林窗和林下的年平均甲烷通量分别为(-0.37±0.26)和(-0.36±0.24)nmol·m^-2·s^-1,林窗和林下的土壤甲烷通量月变化特征无显著差异(P>0.05),呈现旱季高雨季低的特征。土壤甲烷通量的最佳结构模型表明,全年和旱季的林窗与林下土壤甲烷的主要调控因子均为土壤含水量,但雨季土壤甲烷调控作用最强的因子是土壤温度。结果表明,因台风形成的6个林窗短期对土壤甲烷通量没有显著影响,但林窗和林下的土壤甲烷通量具有旱季大于雨季的季节变化特征。     

近自然雨林植物景观营造模式

基于华南地区城市环境及丰富的植物资源,在遵循天然雨林环境因子及群落结构的基础上,以多层次的植物群落、特殊叶形、特化根系、茎花茎果现象和层间植物的利用等方面为切入点,分类归整具有典型雨林特色的植物资源,从植物群落营造,雨林特色挖掘等层面总结近自然雨林景观营造的基本方法,并针对营造及维护过程中的技术问题提出建议。     

Trema micrantha (L.) Blume (Ulmaceae): A promising neotropical tree for site amelioration of deforested land

The genus Trema includes many species that are fast growing, short living pioneer trees common in early successional vegetation and large recent gaps of many tropical moist forests. They establish themselves and grow in open sites with microclimatic and soil conditions which are contrasting to those prevailing in dense forests. With time they change the environmental conditions by attenuating the wide alternations of soil temperature and lower midday air relative humidity characteristic of open places. At the same time, soil moisture and organic matter content, as well as nutrient levels increase due to the reestablishment of an organic cycle in the soil. Consequently they help generating an environment that permits the establishment of mature forest species that often do not survive under the environmental conditions of open places. The propagules of mature forest trees can be reintroduced from conserved areas nearby. The biological and ecological traits related to the potential use of T. micrantha for site amelioration previous to the reintroduction of mature forest trees are presented in this paper. Furthermore, some preliminary experiences in the field are cited. The same use may apply to other fast growing short living pioneers.This revised version was published online in November 2005 with corrections to the Cover Date.     

Forest Grabbing Through Forest Concession Practices: The Case of Guyana

Colonial governments asserted sovereignty and property rights gradually over the territory of Guyana, disregarding preexisting Indigenous Rights. Although a Forest Department modeled on the Indian Forest Service was established, there was no equivalent settlement process to determine the rights of forest peoples. State Forest area is declared by administrative fiat. These two elements have enabled State-endorsed forestland grabbing. Logging was scattered and selective until the early 1980s. A neoliberal economic program from the 1980s has allowed Asian companies to gain control over at least 80% of large-scale forestry concessions, equivalent to one-third of the 15.8 million hectares (Mha) of State-administered public forests. The relative success of the Asian companies can be understood in terms of available capital, willingness to invest, knowledge of markets, and willingness to corrupt. The relative failure of the preexisting Guyanese-owned businesses can be understood in terms of lack of capital, inability to save and unwillingness to invest, lack of knowledge of marketing, and lack of cooperation within the sector. Some conclusions from the Guyana story are relevant to other countries related to resource-hungry transnational enterprises.     

Ecosystem-based management in the Great Bear Rainforest

Ecosystem-based management is the management system being applied to 6.4 million hectares of the coast of British Columbia, Canada, an area referred to as the Great Bear Rainforest. This approach, intended to manage for ecosystem integrity and community wellbeing, is similar in many respects to ecosystem management approaches elsewhere. However, several novel elements are involved in application of ecosystem-based management on British Columbia's coast: shifts in power that have led to increased aboriginal control and the formation of coalitions between groups that were formerly in opposition; development of explicit models relating management strategies to land-use objectives and separating knowledge from values; use of ecological thresholds and natural variability to establish management targets. Current management is based on transitional targets that differ from science-based targets. Many challenges remain in moving to full implementation of ecosystem-based management, including the difficulties involved in moving from one management model to a fundamentally different one, limited resources for implementation, dealing with complex systems, the lack of freely available multi-disciplinary data, and the difficulty of bringing concepts of uncertainty and risk into public policy discussions in a transparent manner.