Nurse Trees as a Forest Restoration Tool for Mixed Plantations: Effects on Competing Vegetation and Performance in Target Tree Species

Multi‐species mixed plantations can be designed to meet social, economic, and environmental objectives during forest restoration. This paper reports results from an experiment in southern Sweden concerning the influence of three different fast growing nurse tree species on the cover of herbaceous vegetation and on the performance of several target tree species. After 10 years, the nurse trees had reduced the competing herbaceous vegetation but the effect was weak and it may take more than a decade to achieve effective vegetation control. The nurse tree species Betula pendula and Larix x eurolepis did improve stem form in some target tree species, but had a minor effect on survival and growth. The open conditions before crown closure of nurse trees strongly influence seedling performance and so delayed planting of target tree species may provide a means to avoid those conditions. Survival and growth differed greatly among the tree species. Besides the two nurse tree species mentioned above, high survival was found in Picea abies and Quercus robur and intermediate survival in Fagus sylvatica, Tilia cordata, and in the N‐fixing nurse tree Alnus glutinosa. Survival was low in the target tree species Fraxinus excelsior L. and Prunus avium. For restoration practitioners, our results illustrate the potential of using nurse trees for rapidly building a new forest structure and simultaneously increase productivity, which might be a cost‐effective strategy for forest restoration.     

不同生态条件下松栎混交林3种优势乔木种群的更新规律

为探究秦岭林区松栎混交林群落乔木优势种的更新规律,通过典型样地调查,对油松(Pinus tabulifor-mis)、锐齿槲栎(Quercus aliena var.acuteserrata)和华山松(Pinus armandii)等3种优势乔木种群更新随林分密度、海拔、坡向、坡位等生态因子的变化规律进行了分析。结果表明:(1)林分密度、海拔、坡向、坡位等生态因子对3种乔木的天然更新均具显著影响;3种优势乔木树种幼苗密度均随林分密度增加而显著增加,林分密度从850株.hm-2增加到1 525株.hm-2时,3种幼树密度也逐渐增加,但林分密度为1 900株.hm-2时,3种幼树密度均显著降低;从海拔1 283m增至1 665m,锐齿槲栎和油松幼苗幼树密度均随海拔增加而显著增加,但海拔增至1 835m时,这两种幼苗幼树密度均显著降低。(2)华山松幼苗幼树密度一直随海拔升高而增加;从南偏西20°到75°,锐齿槲栎和华山松幼树密度逐渐降低,至北偏东40°(阴坡)时又显著增加,但3种乔木幼苗及油松幼树密度一直随坡向变化而增加;锐齿槲栎幼苗密度在下坡位显著高于中坡位和上坡位,但油松和华山松幼苗幼树随坡位由下到上逐渐增加。结果提示,处于中海拔、阴坡且密度适中的林分3种优势乔木更新最佳,对这类林分实施封禁将有助于松栎混交林优势乔木的天然更新。     

云南紫溪山巨春季觅食树种选择

2010年3～5月在云南省楚雄市紫溪山省级自然保护区采用所有事件取样法(all-occurrencerecording),对巨(Sitta magna)觅食树种、觅食树干大小和觅食部位选择进行了观察。采用中心象限法(point-quarter technique)对研究区域的植物重要值进行了测定,用以计算觅食树种的选择系数。结果表明:巨对觅食树种具有明显的选择性,主要选择在云南松(Pinus yunnanensis)觅食,觅食时间占97.46%,觅食次数占96.54%,两者均极显著多于其他树种(P0.01),选择系数为43.89;巨对云南松的树干大小也有选择性,主要在胸径大于15 cm的大树(云南松中、成林)觅食,觅食次数占95.60%;在云南松的树干、枯树枝、活树枝和针叶丛4个部位中,巨偏爱在树干觅食,觅食时间占61.32%,觅食次数占57.02%,两者同样极显著多于其他部位(P0.01)。食物种类及丰富度、种间竞争和巨自身的形态特征等可能是影响巨对觅食树种、觅食树干大小和觅食部位选择的原因。     

子午岭天然林与人工林群落特征比较研究

采用标准样地调查法对比研究了黄土高原子午岭地区人工刺槐林、人工油松林与天然林山杨林、白桦林与辽东栎林的群落特征。结果表明,人工林与天然演替森林（山杨林与自桦林）均具有较丰富的物种组成,为62种左右,而天然顶极森林（辽东栎林）的物种数量则相对较少,为48种。人工林与天然林空间层次分化明显,而且还有一定数量的层间藤本植物。从群落结构的空间格局来看,人工油松林与天然林乔木层与灌木层发育较好,但人工刺槐林的草本层发育较好。人工林的植物多样性主要体现在草本层,而天然林乔木层与灌木层也具有相对较高的多样性。以天然辽东栎林为参照,群落物种组成相似性的比较结果表明,人工刺槐林与天然林的相似性较低,其相似性指数（IS）为19．4,而人工油松林与天然林的相似性则较高,IS值为43．4,甚至高于天然白桦林（33．3）与山杨林（42．9）。因此,相比较而言,油松比刺槐更适合作为黄土高原子午岭地区的人工造林树种。     

阔叶红松林树种间竞争关系及其营林意义

竞争是森林生态系统中的普遍现象 ,其结果是一个有机体阻碍另一个有机体的正常生长和发育[9] 。在生态学上 ,多年来对树种间竞争的研究一直局限于实验的方法 ,而在竞争强度上缺乏数量指标[2 ] 。 2 0世纪 60年代以来 ,很多学者为了更准确地预测林木生长 ,相继提出了许多描述林木间竞争强度的数量指标 ,即竞争指数系统 ,从而形成了用单木生长模型来预测林木生长的方法[2 ,3 ] 。特别是Ｈｅｇｙｉ提出的竞争指数模型对于定量描述树种间的竞争强度有着十分重要的意义。在长白山地区 ,从海拔 5 0 0～ 110 0ｍ分布有温带地区的地带性顶极植被阔叶…     

Host Specificity of Pathogenic Pythium Species: Implications for Tree Species Diversity

In the Janzen–Connell hypothesis, host-specific natural enemies enhance species diversity and influence the structure of plant communities. This study tests the explicit assumption of host specificity for soil pathogens of the genus Pythium that cause damping-off disease of germinating seeds and seedlings. We isolated Pythium spp. from soil of a tropical forest in Panama. Then, in an inoculation experiment, we determined the pathogenicity of 75 tropical isolates of unknown pathogenicity and seven pathogenic temperate isolates of Pythium on seeds and/or seedlings of eight tropical tree species. Only three tropical isolates, one identified as P. ultimum and two as P. aphanidermatum , were pathogenic. Tropical pathogenic isolates were pathogenic on 4–6 of eight tree species. Temperate isolates were pathogenic on 0–4 of eight species, indicating that some tropical tree species are susceptible to novel isolates of Pythium . No tree species was susceptible to all isolates and two species were not susceptible to any isolate. Collectively, these results indicate that these Pythium isolates vary widely in their pathogenicity, causing differential mortality of potential host species; likewise, the tree species vary in their susceptibility to a given Pythium isolate. These differences in pathogenicity and susceptibility indicate some support for the Janzen–Connell assumption of host specificity. While they are not restricted to a single species, their intermediate level of specificity suggests that Pythium spp. have the potential to have some effect on forest community structure and diversity.     

Natural Advance Regeneration of Native Tree Species in Pinus radiata Plantations of South-Central Chile Suggests Potential for a Passive Restoration Approach

Ecosystems - Restoration of natural forests previously replaced by plantations is a widespread challenge for forestry in Chile and elsewhere. However, there is little documented evidence for...     

Early Woody Invasion Under Tree Plantations in Costa Rica: Implications for Forest Restoration

The role of tree plantations as facilitators of tropical forest restoration in degraded lands has been explored recently, but there are few data on the effect of different tree species on invasion of the plant understory. We evaluated early patterns of understory composition in three-year-old native tree plantations in lowland Costa Rica using two pure-species treatment (Jacaranda copaia and Vochysia guatemalensis) and one mixed-species treatment (J. copaia, V. guatemalensis, Stryphnodendron microstachyum, and Calophyllum brasiliense). We also monitored woody invasion in unplanted control areas dominated by grasses. The understory of the different plantation treatments differed in light environment, woody-plant growth and recruitment, and quantity and quality of woody regeneration. Forest tree invasion appeared to be enhanced under Vochysia, while shrubs were more abundant under the Jacaranda and mixed-species treatments. Woody plant growth, herbaceous cover, and understory light availability were highest under Jacaranda, intermediate under mixed species, and lowest under Vochysia. Soil-stored seeds seemed an important source for woody plant recruitment in Jacaranda and mixed species and of minimal importance under Vochysia, probably due to light suppression. It appears that competition from grasses is a major factor influencing early woody invasion in our study area. We found no woody recruitment after one year in the unplanted controls. We suggest that to promote the use of plantations as tools of forest restoration, there is a need to gather basic ecological information on how different tree species may influence patterns of plant understory colonization.     

The Geographical and Institutional Distribution of Ecological Research in the Tropics

We reviewed 1333 papers published in Biotropica and the Journal of Tropical Ecology from 1995 to 2004. Only 62 percent of tropical countries were represented in our survey, with 62 percent of the publications based on research conducted in only ten countries. Sixty-two percent of papers had lead authors that were based at institutions outside the country where the research was conducted. Cross-national collaboration was limited, accounting for only 28 percent of papers with multiple authors. To evaluate if our choice of focal journals could have biased our results, we also reviewed 652 papers published in Ecology , Oecologia , Conservation Biology , and Biological Conservation for five randomly selected years from the same time period. While some differences in authorship and the geographic distribution of research existed, the results from these journals generally mirrored patterns observed in the two focal ones—almost 54 percent of publications were based on research conducted in only ten countries, and most studies had lead authors from a developed country. The results of our review suggest that the geographical distribution of research in the tropics is unequal, and that some important regions remain understudied. The results also suggest a need for a greater focus on establishing collaborative relationships with scientists from tropical countries.     

神农架地区常绿落叶阔叶混交林树种更新研究

神农架山区山体的中部,选取代表性的常绿落叶阎叶混交林样地,总面积为２．４ｈｍ＾２。在样地中对出现的林窗斑块以及相邻的对照的非林窗宙样方进行群落学调查。记录乔木树种的种类、胸径和高度以及它的幼苗和幼树的高度、数量。按照树种在林宙内外重要值的位序差值将群落出现的乔木层树种划分为４类生态种组,其中,对林窗强烈正更新反应的树种有６种,强烈负更新反应的树种９种,中等更新反应的９种,不明显更新反应的１０种。林窗内外乔木树种生态种组的组成明显不同。不同生态种组树种的幼苗在林宙与非林窗斑块中的更新表现出显著的差别。对神农架地区常绿落叶阎叶混交林树种更新的反应和过程的研究结果支持了林窗—分享假说的观点。     

Establishment and Growth of Living Fence Species: An Overlooked Tool for the Restoration of Degraded Areas in the Tropics

Numerous tree species can establish by vegetative means in the tropics. Many are used in agriculture as living fences and in alley cropping and could also be used in a restorational setting. However, little is known about their establishment ability. This study evaluated the establishment ability and cover development of multiple species in three separate field trials in northern Honduras. First, 11 species were evaluated for their ability to establish in a common garden experiment. Second, of the former species, Bursera simaruba and Gliricidia sepium were evaluated for 2 years for their ability to establish vegetatively and develop cover at three deforested sites. Lastly, a study examined whether greater initial stake height and diameter at breast height increased the establishment success and crown development of G. sepium stakes. First, five species, Erythrina berteroana, Erythrina fusca, Jatropha curcas, G. sepium, and B. simaruba, had high establishment success. Others showed promise but may have been planted in the wrong season. Second, establishment for G. sepium was nearly 100% at all sites, whereas B. simaruba ranged from 30–50%. Gliricidia sepium stakes developed more rapidly and attained greater cover than B. simaruba. Dry season planting may increase the establishment success of both species. Lastly, greater initial stake height and diameter at breast height each resulted in greater crown development for G. sepium. The use of living fence species as a restorational tool has been overlooked. Aside from the advantages of planting tree species vegetatively, species can act as seed recruitment foci by attracting seed dispersers and provide shade to improve microclimatic conditions for seedling establishment. The technique described is simple and could have broad application throughout tropical regions.     

Rice Grain Quality and Consumer Preferences: A Case Study of Two Rural Towns in the Philippines

Hedonic pricing analysis is conducted to determine the implicit values of various attributes in the market value of a good. In this study, hedonic pricing analysis was applied to measure the contribution of grain quality search and experience attributes to the price of rice in two rural towns in the Philippines. Rice samples from respondents underwent quantitative routine assessments of grain quality. In particular, gelatinization temperature and chalkiness, two parameters that are normally assessed through visual scores, were evaluated by purely quantitative means (differential scanning calorimetry and by digital image analysis). Results indicate that rice consumed by respondents had mainly similar physical and chemical grain quality attributes. The respondents’ revealed preferences were typical of what has been previously reported for Filipino rice consumers. Hedonic regression analyses showed that grain quality characteristics that affected price varied by income class. Some of the traits or socioeconomic factors that affected price were percent broken grains, gel consistency, and household per capita rice consumption. There is an income effect on rice price and the characteristics that affect price vary between income classes.     

生态控制茶园内害虫、天敌种类及数量的季节变化规律

对衡山生态控制茶园内害虫,天敌种类及数量季节变化的系统调查与排序分析表明,生态控制茶园由于生态环境优良,长期不使用化学农药,使得害虫,天敌种类多,数量少,群落间处于较好的平衡状态,群落的季节变化明显受到气候条件、茶树生育期和茶园采摘的影响,害虫、天敌的年消长规律与茶树的生长规律基本相同,即每年的11月份至翌年的3月份为茶树,害虫与天敌的越冬期;5至9月份为活动高峰期,茶树旺盛生长,害虫,天敌大量繁衍活动;4和10月份是过渡期,茶树,害虫与天敌均由越冬转入活动或由活动转入越冬,体现了天敌－害虫－茶树之间的追随与平衡状态,根据各个时期群落的特点可以采取相应的综合治理措施,因此,改善茶园生态环境,加强茶园管理,减少化学农药的使用是茶园害虫生态控制的基础和保护。     

Ecological Risk Assessment of a Metal-Contaminated Area in the Tropics. Tier II: Detailed Assessment

This study presents data on the detailed evaluation (tier 2) of a site-specific ecological risk assessment (ssERA) in a former smelter area contaminated with metals (Santo Amaro, Bahia, Brazil). Combining information from three lines of evidence (LoE), chemical (ChemLoE), ecotoxicological (EcotoxLoE) and ecological (EcoLoE), in the Triad approach, integrated risk values were calculated to rank sites and confirm the potential risk disclosed with tier 1. Risk values were calculated for the habitat and for the retention functions in each sampling point. Habitat function included the ChemLoE calculated from total metal concentrations. The EcotoxLoE was based on reproduction tests with terrestrial invertebrates (Folsomia candida, Enchytraeus crypticus, Eisenia andrei), shoot length and plant biomass (Avena sativa, Brassica rapa). For the EcoLoE, ecological parameters (microbial parameters, soil invertebrate community, litter breakdown) were used to derive risk values. Retention function included the ChemLoE, calculated from extractable metal concentrations, and the EcotoxLoE based on eluate tests with aquatic organisms (Daphnia magna reproduction and Pseudokirchneriella subcapitata growth). Results related to the habitat function indicated that the metal residues are sufficient to cause risk to biota, while the low metal levels in extracts and the general lack of toxicity in aquatic tests indicated a high soil retention capacity in most sampling points. Integrated risk of tier 2 showed the same trend of tier 1, suggesting the need to proceed with remediation actions. The high risk levels were related to direct toxicity to organisms and indirect effects, such as failure in the establishment of vegetation and the consequent loss of habitat quality for microorganisms and soil fauna. This study shed some light on the selection of tools for the tier 2 of an ssERA in tropical metal-contaminated sites, focusing on ecological receptors at risk and using available chemical methods, ecological surveys and ecotoxicity tests.     

马尾松与乡土阔叶树种凋落叶木质素降解的混合效应

为了解森林凋落叶分解过程中木质素的释放规律,对马尾松(Pinus massoniana,P)、檫木(Sassafras tzumu,S)、香樟(Cinnamomum camphora, C)和香椿(Toona sinensis, T)凋落叶分解过程中的木质素降解率进行了研究。结果表明,大部分混合凋落叶的木质素在分解过程中出现富集现象,PT和PC组合的木质素含量在第1年较高,之后降低。而PS、PST、PSC、PCT和PSCT组合在0～6、0～9和15～18个月表现出富集现象,其余时期降低。在不同分解时期,部分混合凋落叶组合的木质素降解率表现出非加和效应,呈协同效应,以春季和夏季的协同效应较强,秋冬季较弱。此外,PSCT6121、PSC622、PS64和PC64的木质素降解率在大部分分解时期(≥6/8)表现出协同效应。因此,马尾松与乡土阔叶树种凋落叶混合后促进了木质素的降解,在马尾松人工林改造过程中,与乡土阔叶树种适当混种,可促进凋落叶中木质素的降解。     

树种组成对北亚热带11年生常绿阔叶人工林碳储量的影响

以中国北亚热带退化灌木林改造而来的木荷-青冈栎混交林和杜英纯林为对象,研究树种组成对常绿阔叶人工林生态系统碳储量的影响。结果表明:(1)退化灌木林改造成两种人工林生长11年后,生态系统植被、土壤碳储量均显著增加;植被碳储量的增加主要来自乔木层。(2)两种人工林碳积累能力有差异。杜英林植被碳储量比木荷-青冈栎林高99.4%,其中杜英林的乔木层碳储量比木荷-青冈栎林高27.75t·hm-2,是后者的2倍;杜英林土壤有机碳储量(0~50cm)显著高于木荷-青冈栎林10.17t·hm-2,其中在0~10、20~30cm土层杜英林均显著高于木荷-青冈栎林。研究表明,退化灌木林人工改造成常绿阔叶林后生态系统碳储量显著增加,杜英纯林碳蓄积能力明显高于木荷-青冈栎混交林,说明在以增加碳储量为目的的退化生态系统改造过程中,树种选择非常重要。     

氟污染区绿化树种的选择

前言凡使用含氟矿石(如冰晶石、磷矿石等)作原料的工厂,在碾磨、加热、酸化等过程中,以及利用含氟化合物作为接触剂、助熔剂的各种工艺过程的生产中,都会散发出大量的含氟废气与粉尘污染环境,给农林业生产及人