Artificial canopy gaps accelerate restoration within an exotic Pinus radiata plantation

We created small‐scale artificial canopy gaps to accelerate the growth of mature indigenous forest canopy species for restoration of an 18‐year‐old exotic Pinus radiata plantation forest, in the Marlborough Sounds, New Zealand. Small and large circular gaps were formed by felling. Seedlings of two indigenous forest canopy species, Podocarpus totara (Podocarpaceae) and Beilschmiedia tawa (Lauraceae), were planted within artificial gaps and undisturbed plantation canopy. Seedling height growth, mortality, and occurrence of animal browse were monitored at approximately 6‐month intervals over 17 months. Both P. totara and B. tawa differed significantly in height growth and in animal browse occurrence among artificial gap treatments. Growth of the light‐demanding P. totara was better under large canopy gaps, whereas growth of the shade‐tolerant B. tawa increased under gaps of any size but was most consistent under small gaps. For P. totara, any significant restoration benefit of gap formation on height growth was lost when browsed seedlings were taken into account. Animal browse significantly limited B. tawa height growth in large but not in small gaps. Small‐scale canopy gap creation is an effective method of modifying light transmission to the plantation understorey and accelerating seedling growth rates. Canopy gap size can be used to optimize understorey illumination according to species‐specific light requirements. The increased occurrence of animal browse in gaps requires consideration. Artificial canopy gaps within planted monocultures create structural heterogeneity that would otherwise take an extended period of time to develop. These results further support the role of plantations as indigenous forest restoration sites.     

Canopy manipulations of exotic Bitter Willow (Salix elaeagnos) forest for indigenous seedling recruitment: A pilot study

The invasive exotic tree species Bitter Willow (Salix elaeagnos; Salicaceae) has colonised areas of rank exotic grassland and has been found to contain indigenous seed, dispersed by frugivorous birds into the monospecific stands. This small pilot study examined whether indigenous seedlings that have germinated in the understorey of exotic Bitter Willow stands could be stimulated to establish through the creation of small‐scale canopy gaps. In Bitter Willow forest, four single Bitter Willow trees were poisoned to create canopy gaps. Light transmission and seedling regeneration of tree and shrub species were assessed beneath both the four manipulated and three comparable intact Bitter Willow canopies. Over 3 years, seedling height and density increased more beneath opened compared to intact Bitter Willow canopies. These results suggest that Bitter Willow can fill the roles of both a facilitative nurse and a perch tree. Larger‐scale canopy manipulation experiments of both Bitter Willow and other Salix species are needed to determine the full potential of canopy manipulations for forest restoration.     

退化森林生态系统恢复评价研究综述

森林退化是一个世界性的问题,对退化的森林进行恢复评价是合理地进行森林生态系统管理的基础。介绍了森林退化的概念,综述了退化森林生态系统恢复评价的一般程序,主要包括恢复目标的确定、参照系的选择、评价指标体系的构建及定量评价等几个方面。目前,大多数退化森林恢复评价主要包括物种多样性、植被结构和生态学过程3个方面。其中,物种多样性包括物种丰富度和多度等;植被结构包括植被盖度、乔木密度、高度、胸高断面积、生物量和凋落物结构等;生态学过程包括养分库、土壤有机质以及生物间的相互关系等。不同的研究者或管理者由于对恢复其生态系统服务功能的需求存在差异,评价退化生态系统恢复的角度也不一样。恢复评价可以从特殊种群到整个生态系统的不同层次进行。在深刻理解森林退化定义的基础上,建立现实的目标和正确地选择参照系是恢复评价的前提。     

Relationships between the density of two potential restoration tree species and plant species abundance and richness in a degraded Afromontane forest of Kenya

In recent years, there have been considerable efforts to restore degraded tropical montane forests through active restoration using indigenous tree species. However, little is known about how these species used for restoration influence other species. In this study, two potential restoration species, Albizia gummifera and Neoboutonia macrocalyx, are investigated with regard to the relationship between their density and the abundance and richness of other plant species. The study was conducted in a degraded forest consisting of disturbed transition zones and secondary forest. Our results show positive relationships between the density of A. gummifera and the abundance of tree seedling and sapling richness in the transition zones and in the secondary forest. Shrub richness was negatively related to the density of A. gummifera. Abundance and richness of tree saplings and shrubs were positively related to N. macrocalyx density both in the transition zones and in the secondary forest. Herb species richness declined with N. macrocalyx density in the transition zones but increased with N. macrocalyx density in the secondary forest. The positive relationships between the density of the two tree species and species richness of other woody species suggest that both A. gummifera and N. macrocalyx can be suitable for active restoration of degraded mountain forests within their natural range.     

Measuring progress in status of land under forest landscape restoration using abiotic and biotic indicators

The paper suggests a minimum set of abiotic and biotic threshold indicators and progress indicators for forest landscape restoration (FLR), then also briefly discusses progress indicators of pressures and project outputs. FLR aims to restore multiple functions of forests at a landscape scale. It is predicated on the hypothesis that restoration produces enabling conditions for ecosystem services, including regulating services such as carbon sequestration and pollination, and provisioning services such as food and energy. As FLR gains greater uptake, it is increasingly important to monitor progress. The types of indicators required are influenced by the degree of forest loss and degradation. To measure the status of land under restoration, one or more abiotic and biotic threshold indicators are required, measuring the return of enabling conditions for restoration (soil quality, water, etc.), along with progress indicators measuring the reemergence of the ecosystem services. Although all elements of the proposed monitoring framework are well known, compiling them into a coherent system, suitable for application in a wide range of conditions, will take much further development.     

长江上游退化森林生态系统恢复与重建刍议

通过对国内外生态系统恢复与重建研究进展的综述,论述了我国长江上游森林生态系统退化的主要特征和森林生态系统退化的现状,分析了长江上游生态环境建设存在的主要问题,并提出相应对策。在此基础上,针对退化森林生态系统提出恢复和重建的基本思路和建议。     

Towards more effective integration of tropical forest restoration and conservation

Conservation and restoration interventions can be mutually reinforcing and are converging through an increased focus on social dimensions. This paper examines how to more effectively integrate the complementary goals of conservation and restoration of tropical forests. Forest conservation and restoration interventions are integral components of a broad approach to forest ecosystem and landscape management that aims to maintain and restore key ecological processes and enhance human well‐being, while minimizing biodiversity loss. The forest transition model provides a useful framework for understanding the relative importance of forest conservation and restoration interventions in different regions. Harmonizing conservation and restoration presents serious challenges for forest policy in tropical countries, particularly regarding the use and management of secondary forests, fallow vegetation, and forests degraded by logging and fire. Research to implement restoration more effectively in tropical regions can be stimulated by transforming questions that initially focused on conservation issues. Examination of papers published in Biotropica from 2000–2018 shows that most studies relevant to tropical forest conservation do not address forest restoration issues. Forest restoration studies, on the other hand, show a consistent association with conservation issues. There is much scope for further integration of conservation and restoration in research, practice, and policy. Securing a sustainable future for tropical forests requires developing and applying integrated approaches to landscape management that effectively combine knowledge and tools from multiple disciplines with practical experience and engagement of local stakeholders. Abstract in Portuguese is available with online material.     

油松水源保护林人工诱导更新与定向恢复机理

以油松水源保护林为对象,进行人工诱导更新与定向恢复机理研究。结果表明,在郁闭林分内油松更新苗密度平均为5 375株.hm-2,更新苗年龄为1~2年,而在人工Gap“效应岛”样地内,更新苗密度平均为17 062.5株.hm-2,其中1~2年、3~4年、5~6年生更新苗分别占73.44%,13.97%和12.59%;生长季光照强度在0、1.5和2.0 m三个不同高度梯度上,在Gap内部的平均值分别为289.0×100、542.0×100和589.0×100 lux,在对照林分内分别为139.0×100、146.0×100和246.0×100lux;从夏季观测到的空气温度平均值日变化分析,在白天Gap内的温度高于郁闭林分内部,温差可差2~3℃,在夜间Gap内的温度低于郁闭林分内,温差可差0.5~1℃;在白天6:00~11:00,人工Gap“效应岛”内空气湿度明显低于郁闭林分内,在其它时间段大致相当;对于同一层次土壤而言,Gap内的土壤温度明显高于郁闭林分内且变化幅度大,在0、10和20 cm三个梯度上Gap与郁闭林分相比土壤温度最大差值分别可达10、5和2℃;0~10、10~20和20~30 cm三个层次平均土壤含水量在Gap内分别为16.9%1、5.1%和12.3%,在郁闭林分内分别为14.6%、12.5%和9.9%。总体上比较二者的光照强度、空气温度、空气湿度、土壤温度、土壤水分等有显著差异,因此人工Gap“效应岛”的创建是诱导其内部微环境因子变化的基础,也是油松水源保护林定向恢复更新的机理之所在。     

Undertaking large‐scale forest restoration to generate ecosystem services

The global community is seeking to substantially restore the world's forest cover to improve the supply of ecosystem services. However, it is not clear what type of reforestation must be used and there is a risk that the techniques used in industrial timber plantations will become the default methodology. This is unlikely to be sufficient because of the well‐known relationship between biodiversity and ecological functioning. Restoration may be achieved through natural regeneration but this may not always occur at critical locations. Ecological restoration involving species‐rich plantings might also be used but can be difficult to implement at landscape scales. I review here the consequence of planting more limited numbers of species and the effects of this on the delivery of ecosystem services. Evidence suggests many commonly sought ecosystem services—though not all—may be generated by the modest levels of species richness provided these species have appropriate traits. The literature also shows that the alpha diversity of restored forests is not the only driver of functionality and that the location and extent of any reforestation are significant as well; beta and gamma diversity may also affect functionality but these relationships remain unclear. Encouraging the adoption of even moderately diverse plantings at landscape scales and at key locations will require policies and institutions to balance the type, location, and scale of restoration and make the necessary trade‐offs between national and local aspirations. New approaches and metrics will have to be developed to monitor and assess restoration success at these larger scales.     

Time,space, place,and the Bonn Challenge global forest restoration target

The Bonn Challenge, a global effort to begin restoring 350 million hectares of degraded forest landscapes by 2030, was launched in 2011. To date countries have committed to restore more than 60 million hectares as part of the Bonn Challenge. As global decision‐makers, governments, and communities join the effort to restore degraded land, new questions about the economics of restoration have emerged. Critics argue that restoration takes too long, costs too much, and produces too few benefits to justify public or private expenditures. This paper addresses these concerns by presenting a methodology for valuing the net benefits of large‐scale ecosystem restoration initiatives by estimating the net benefit of achieving the Bonn Challenge. This paper also estimates the net benefit of achieving the Bonn Challenge restoration target under different social discounting regimes, different valuations of public goods, and different time horizons to see how they affect the argument for investing society's scarce resources in restoration. The results suggest that achieving the Bonn Challenge would generate a net benefit of between U.S.$0.7 and U.S.$9 trillion. The results show that restoration can create benefits that exceed its costs and that the value of these benefits might differ depending on the discount rate. The results show that lower social discount rates correspond to higher restoration rates. This suggests that the Bonn Challenge target is more likely to be met when a low social discount rate is used to discount the benefits and costs of restoration.     

Evidence for species‐specific plant responses to soil microbial communities from remnant and degraded land provides promise for restoration

Below‐ground interactions between soil microbial communities and plants play important roles in shaping plant community structure, but are currently poorly understood. Understanding these processes has important practical implications, including for restoration. In this study, we investigated whether soil microbes from remnant areas can aid the restoration of old‐fields, and whether soil microbes from an old‐field encourages further invasive establishment. In a glasshouse experiment, we measured growth and survival of two native grasses (Austrostipa nodosa and Rytidosperma auriculatum) and an invasive grass (Lolium rigidum) grown in sterile soil inoculated with whole soil from three locations: an old‐field, a remnant grassland, and a seed orchard planted with native grasses 7 years ago. Plants grown in sterile, non‐inoculated soil acted as controls. The orchard inoculant was included to test whether soil microbes from an area cultivated with native grasses induced plant responses similar to remnant areas. The remnant treatment resulted in the highest biomass and no mortality for R. auriculatum. All inoculant types increased the biomass of the invasive species equally. The native grass, A. nodosa, was the most sensitive to the addition of inoculum, whereas the invasive L. rigidum suffered very low mortality across all treatments. Overall, mortality was highest in the old‐field treatment at 42.9%. These results give insights into how soil microbes can affect community structure and dynamics, e.g. the high mortality of natives with old‐field inoculant may be one mechanism that allows invasive species to dominate. Poorer performance of native species with the orchard inoculant suggests it would not make a suitable replacement for remnant soil; therefore, more work is needed to understand the requirements of target species and their interactions before this technique can be exploited to maximum benefit.     

Chemotaxonomic Considerations of the n‐Alkane Composition in Pinus heldreichii,P. nigra,and P. peuce

The n‐alkane composition in the leaf cuticular waxes of natural populations of Bosnian pine (Pinus heldreichii), Austrian pine (P. nigra), and Macedonian pine (P. peuce) was compared for the first time. The range of n‐alkanes was wider in P. nigra (C₁₆ – C₃₃) than in P. heldreichii and P. peuce (C₁₈ – C₃₃). Species also diverged in abundance and range of dominant n‐alkanes (P. heldreichii: C₂₃, C₂₇, and C₂₅; P. nigra: C₂₅, C₂₇, C₂₉, and C₂₃; P. peuce: C₂₉, C₂₅, C₂₇, and C₂₃). Multivariate statistical analyses (PCA, DA, and CA) generally pointed out separation of populations of P. nigra from populations of P. heldreichii and P. peuce (which were, to a greater or lesser extent, separated too). However, position of these species on the basis of n‐alkane composition was in accordance neither with infrageneric classification nor with recent molecular and terpene investigations.     

Substrate modification for enhanced native forest restoration,Reefton

Restoration of postmining substrates to native forest is a standard requirement of resource consents for mine sites located within areas of native forest in New Zealand. Unweathered waste rock presents significant challenges for plant growth, and past research highlights the importance of replacing soil as part of restoration. However, replacing soil with its horizon structure intact or even obtaining sufficient soil for restoration can be a challenge in some situations. In this paper, we describe the results of two trials undertaken at the OceanaGold Ltd. open‐cast gold mine in Reefton to explore the influence of substrate conditions on the growth of native forest seedlings. We show that beech (Nothofagus) seedlings grown on A‐horizon soil grew significantly better than those grown on soil mixed with waste rock, and both grew significantly better than plants grown just on waste rock. In the second trial, we show that bark chips are not a good substitute for soil. These results confirm the importance of having the correct substrate for successful native forest restoration.     

Contributions of long‐distance dispersal to population growth in colonising Pinus ponderosa populations

Long‐distance dispersal is an integral part of plant species migration and population development. We aged and genotyped 1125 individuals in four disjunct populations of Pinus ponderosa that were initially established by long‐distance dispersal in the 16th and 17th centuries. Parentage analysis was used to determine if individuals were the product of local reproductive events (two parents present), long‐distance pollen dispersal (one parent present) or long‐distance seed dispersal (no parents present). All individuals established in the first century at each site were the result of long‐distance dispersal. Individuals reproduced at younger ages with increasing age of the overall population. These results suggest Allee effects, where populations were initially unable to expand on their own, and were dependent on long‐distance dispersal to overcome a minimum‐size threshold. Our results demonstrate that long‐distance dispersal was not only necessary for initial colonisation but also to sustain subsequent population growth during early phases of expansion.     

茂兰退化喀斯特森林植被自然恢复中生态系统碳吸存特征

为了了解退化喀斯特森林自然恢复中生态系统碳吸存趋势, 采用空间代替时间的方法, 研究了茂兰退化喀斯特森林自然恢复中生态系统碳吸存特征。结果表明: 总体上植被生物量随恢复进程递增, 其中乔木层与其变化一致, 草本层、灌木层则相反; 喀斯特植被的地上与地下生物量之比较低, 尤其灌木层的地上与地下生物量之比最低; 加权平均含碳率随恢复进展递增; 随恢复进程, 植被乔木层碳密度递增, 草本层、灌木层碳密度递减; 总体上生态系统及其植被、土壤的碳密度由恢复早期(草本阶段、草灌阶段)经中期(灌木阶段、灌乔阶段)至后期(乔木阶段、顶极阶段)呈增加趋势, 而凋落物的相反。在贵州茂兰国家级自然保护区喀斯特森林的恢复进程中, 植被对生态系统碳库的影响最大, 尤其是木本植被, 而土壤的影响较小, 因此, 加强植被恢复对喀斯特地区生态系统碳汇具有极重要的意义。     

Future wood productivity of Pinus radiata in New Zealand under expected climatic changes

The physiologically based growth model CenW was used to simulate wood‐productivity responses of Pinus radiata forests to climate change in New Zealand. The model was tested under current climatic conditions against a comprehensive set of observations from growth plots located throughout the country. Climate change simulations were based on monthly climate change fields of 12 GCMs forced by the SRES B1, A1B and A2 emission scenarios for 2040 and 2090. Simulations used either constant or increasing CO₂ concentrations corresponding to the different emission scenarios. With constant CO₂, there were only slight growth responses to climate change across the country as a whole. More specifically, there were slight growth reductions in the warmer north but gains in the cooler south, especially at higher altitudes. For sites where P. radiata is currently grown, and across the full suite of GCMs and emission scenarios, changes in wood productivity averaged +3% for both 2040 and 2090. When increasing CO₂ concentration was also included, responses of wood productivity were generally positive, with average increases of 19% by 2040 and 37% by 2090. These responses varied regionally, ranging from relatively minor changes in the north of the country to very significant increases in the south, where the beneficial effect of increasing CO₂ combined with the beneficial effect of increasing temperatures. These relatively large responses to CO₂ depend on maintenance of the current adequate fertility levels in most commercial plantations. Productivity enhancements came at the expense of some soil‐carbon losses. Average losses for the country were simulated to average 3.5% under constant CO₂ and 1.5% with increasing CO₂ concentration. Again, there were regional differences, with larger losses for regions with lesser growth enhancements, and lesser reductions in regions where greater productivity enhancements could partly balance the effect of faster decomposition activity.