中国热带次生林分布、类型与面积研究

热带林的保护问题已受到世界各国的高度重视,由于占世界热带林面积约三分之一的热带次生林,其经济和生态效益通常较差,处于相对被忽视的状态,因此也往往被进一步破坏。将次生林经营纳入可持续经营的轨道,是实现热带林可持续经营目标的重要战略。通过对中国热带森林研究、经营和统计资料的分析,结合本项目实施过程的实地调研取得的结果,文章对中国热带地区次生林分布、面积和类型作了阐述。热带森林主要分布在海南、广东、广西、云南、台湾,以及福建和西藏的部分地区,包括124个县市的全部和50个县市的部分地区。据可认可的资料统计,中国热带林地面积（不含台湾省）约1125．66万hm^2。其中有林地面积1074．49万hm^2,次生林面积544万hm^2。次生林占热带地区林地面积的48．33％,占有林地总面积的50．63％。中国热带林地和次生林的实际数字估计要比这一数值大6％以上,因为中国这几年高度重视林业建设,森林植被特别是热带森林植被恢复得很快,林地和次生林一直在不断增加。热带森林类型主要有：热带雨林（包括湿润雨林、山地雨林）;热带季雨林（包括半常绿季雨林、落叶季雨林、石灰岩季雨林）;南海珊瑚岛植被;海岸红树林等。从森林经理的角度,中国热带次生林的类型可分为：（1）次生阔叶林,包括次生常绿阔叶雨林、次生季雨林和次生季风常绿阔叶林;（2）次生灌木林;（3）次生针叶林;（4）次生红树林及次生珊瑚岛林等四大类型。     

湖北木林子自然保护区常绿落叶阔叶混交林干扰特征

常绿落叶阔叶混交林是木林子自然保护区的1种主要植被类型。在各种自然干扰和人为干扰的协同作用下,形成了木林子常绿落叶阔叶混交林特有的干扰体系。在常绿落叶阔叶混交林的保护和经营中,要利用封山育林、森林抚育、合理择伐和人工促进天然更新等增益性人工干扰,坚决阻止过渡的森林采伐和毁林开荒等破坏性人工干扰。应参照以自然林窗干扰,采用择伐方式经营常绿落叶阔叶混交林。     

Effects of fuel treatments on fire severity in an area of wildland–urban interface,Angora Fire,Lake Tahoe Basin,California

The Angora Fire burned 1243 ha of Jeffrey pine and mixed conifer forest in the Lake Tahoe Basin between June 24 and July 2, 2007. The Angora Fire burned at unusually high severity due to heavy fuels; strong winds; warm, dry weather; and unseasonably low fuel moistures. The fire destroyed 254 homes, and final loss and suppression cost estimates of $160,000,000 make the Angora Fire one of the ten costliest wildfires in US history. The Angora Fire burned into 194 ha of fuel treatments intended to modify fire behavior and protect private and public assets in the Angora Creek watershed. The fire thus provides a unique opportunity to quantitatively assess the effects of fuel treatments on wildfire severity in an area of wildland–urban interface. We measured fire effects on vegetation in treated and adjacent untreated areas within the Angora Fire perimeter, immediately after and one year after the fire. Our measures of fire severity included tree mortality; height of bole char, crown scorch, and crown torch; and percent crown scorch and torch. Unlike most studies of fuel treatment effectiveness, our study design included replication and implicitly controlled for variation in topography and weather. Our results show that fuel treatments generally performed as designed and substantially changed fire behavior and subsequent fire effects to forest vegetation. Exceptions include two treatment units where slope steepness led to lower levels of fuels removal due to local standards for erosion prevention. Hand-piled fuels in one of these two units had also not yet been burned. Excepting these units, bole char height and fire effects to the forest canopy (measured by crown scorching and torching) were significantly lower, and tree survival significantly higher, within sampled treatments than outside them. In most cases, crown fire behavior changed to surface fire within 50 m of encountering a fuel treatment. The Angora Fire underlines the important role that properly implemented fuel treatments can play in protecting assets, reducing fire severity and increasing forest resilience.     

常绿落叶阔叶混交林恢复过程中林分生长动态

以鄂西南木林子自然保护区山地常绿落叶阔叶混交林不同恢复时期群落为对象,研究了常绿落叶阔叶混交林恢复过程中林分生长动态。结果表明：随着群落的恢复,林分蓄积量随着群落的恢复不断增加,当恢复到60a时,林分中落叶阔叶用材树种蓄积量最高。生物量随着群落的恢复逐渐增加,但恢复过程中生物量的发展速率不是均匀的,在群落恢复前期发展较快,在后期则发展较慢。     

鄂西南常绿落叶阔叶混交林生态恢复技术研究

常绿落叶阔叶混交林是我国特有的自然植被类型和天然林类型,也是鄂西南武陵山区中山地带最典型、最重要的天然林类型.由于长期过度采伐利用,退化严重.采取全面禁伐的强制性保护措施,恢复进程缓慢,一些严重退化群落甚至难以恢复.遵循常绿落叶阔叶混交林演替规律,借助自然力,通过以积极的人为干预措施,可以快速恢复与重建鄂西南武陵山区常绿落叶阔叶混交林.本文在调查研究的基础上,论述了鄂西南武陵山区常绿落叶阔叶混交林的演替动态和恢复的可能性,分析了常绿落叶阔叶混交林恢复的制约因素,提出了常绿落叶阔叶混交林的恢复的3种方式即人工恢复、人工促进天然恢复和人工重建,以及封禁保护、抚育间伐、补植（播）、封山育林、林分改造和人工重建等恢复技术要点.     

Forest fire effects in beech dominated mountain forest of Iran

Most of world's forests of different climates have a history of fire, but with different severities. Fire regimes for broadleaf deciduous forests have return intervals that vary from many decades (or less) to centuries (or more). Iran has a total of 1.2 million ha of temperate forest in the north, where fires burn about 300–400 ha annually. This study focused on the impact of fire on forest structure, tree species quality, and regeneration composition (specially beech) in the Chelir forest of northern Iran. The results showed that forest fires changed the structure and had different effects on tree species composition between burned and control areas. Thin barked species such as oriental beech (Fagus orientalis Lipsky) and coliseum maple (Acer cappadocicum Gled.) have been affected more than those with thick bark, like hornbeam (Carpinus betulus L.) and chestnut-leaved oak (Quercus castaneifolia C.A. Mey). The density of oriental beech regeneration in the unburned area was greater than in the burned area, while the quantity of regeneration of hornbeam, coliseum maple and velvet maple (Acer velutinum Boiss) was higher in burned area. Forest fire had a greater effect on oriental beech quality, and changed regeneration composition in the burned area. Fire prevention activities should be considered as a silvicultural treatment for preserving these valuable forests.     

Relationship between annual rainfall and tree mortality in a tropical dry forest: Results of a 19-year study at Mudumalai,southern India

Variability in rainfall is known to be a major influence on the dynamics of tropical forests, especially rates and patterns of tree mortality. In tropical dry forests a number of contributing factors to tree mortality, including dry season fire and herbivory by large herbivorous mammals, could be related to rainfall patterns, while loss of water potential in trees during the dry season or a wet season drought could also result in enhanced rates of death. While tree mortality as influenced by severe drought has been examined in tropical wet forests there is insufficient understanding of this process in tropical dry forests. We examined these causal factors in relation to inter-annual differences in rainfall in causing tree mortality within a 50-ha Forest Dynamics Plot located in the tropical dry deciduous forests of Mudumalai, southern India, that has been monitored annually since 1988. Over a 19-year period (1988–2007) mean annual mortality rate of all stems >1 cm dbh was 6.9 ± 4.6% (range = 1.5–17.5%); mortality rates broadly declined from the smaller to the larger size classes with the rates in stems >30 cm dbh being among the lowest recorded in tropical forest globally. Fire was the main agent of mortality in stems 1–5 cm dbh, elephant-herbivory in stems 5–10 cm dbh, and other natural causes in stems >10 cm dbh. Elephant-related mortality did not show any relationship to rainfall. On the other hand, fire-related mortality was significantly negatively correlated to quantity of rainfall during the preceding year. Mortality due to other causes in the larger stem sizes was significantly negatively correlated to rainfall with a 2–3-year lag, suggesting that water deficit from mild or prolonged drought enhanced the risk of death but only with a time lag that was greater than similar lags in tree mortality observed in other forest types. In this respect, tropical dry forests growing in regions of high rainfall variability may have evolved greater resistance to rainfall deficit as compared to tropical moist or temperate forests but are still vulnerable to drought-related mortality.     

Vegetation and weather explain variation in crown damage within a large mixed-severity wildfire

The 2002 Biscuit Fire burned through more than 200,000 ha of mixed-conifer/evergreen hardwood forests in southwestern Oregon and northwestern California. The size of the fire and the diversity of conditions through which it burned provided an opportunity to analyze relationships between crown damage and vegetation type, recent fire history, geology, topography, and regional weather conditions on the day of burning. We measured pre- and post-fire vegetation cover and crown damage on 761 digital aerial photo-plots (6.25 ha) within the unmanaged portion of the burn and used random forest and regression tree models to relate patterns of damage to a suite of 20 predictor variables. Ninety-eight percent of plots experienced some level of crown damage, but only 10% experienced complete crown damage. The median level of total crown damage was 74%; median damage to conifer crowns was 52%. The most important predictors of total crown damage were the percentage of pre-fire shrub-stratum vegetation cover and average daily temperature. The most important predictors of conifer damage were average daily temperature and “burn period,” an index of fire weather and fire suppression effort. The median level of damage was 32% within large conifer cover and 62% within small conifer cover. Open tree canopies with high levels of shrub-stratum cover were associated with the highest levels of tree crown damage, while closed canopy forests with high levels of large conifer cover were associated with the lowest levels of tree crown damage. Patterns of damage were similar within the area that burned previously in the 1987 Silver Fire and edaphically similar areas without a recent history of fire. Low-productivity sites on ultramafic soils had 92% median crown damage compared to 59% on non-ultramafic sites; the proportion of conifer cover damaged was also higher on ultramafic sites. We conclude that weather and vegetation conditions — not topography — were the primary determinants of Biscuit Fire crown damage.     

深圳市主要植被群落类型划分及物种多样性研究

采用组间平均联结法对深圳市主要植被群落进行划分,并应用Gleason丰富度指数、Shannon-Wiener指数、Simpson指数和Pielou指数对主要植被群落的物种多样性水平进行比较分析。结果表明:深圳市城市森林可以划分为5个群系组和31个群落类型;各群落类型的物种多样性均表现为灌木层>乔木层,常绿阔叶人工林的乔木层和灌木层的生物多样性指数均最低,常绿落叶阔叶人工林乔木层丰富度指数、Shannon-Wiener指数、均匀度指数均最高,常绿阔叶人工林的乔木层优势种比较明显。     

陕西省长江流域生态地貌功能分区与评价

采用１０个主要生物气候指标，结合地形地貌及相的地带性植被和地带性土壤，对陕西省长江流域３１个县（市）进行动态聚类综合分析，本区可归并为２个森林植物气候带，５个生态地貌功能区。即：低山丘陵区北亚热带常绿落叶阔叶林生物气候区，包括安康盆地，汉中盆地，热暖温带针阔混交林、针叶林生物气候区；包括秦岭南坡东部中山，低山区，秦岭南坡中、西部中、高山区和巴山北坡中山、低山。各生态地貌功能区的生物气候特征明显，符     

Controls of litter quality on the carbon sink in soils through partitioning the products of decomposing litter in a forest succession series in South China

Through the long-term measurement and development of a method for partitioning the products of decomposing litter, the impact of chemical components of forest debris on soil organic carbon (SOC) accumulation was studied in a forest succession series in South China. We quantified how litter quality is strongly correlated with the partitioning of respiration, dissolved organic carbon (DOC) and fragments of decomposing litter. In the succession sequence of 60-year-old pine forest (PF), to 80-year-old mixed pine and evergreen broadleaved forest (MF) to more than 400-year-old monsoon evergreen broadleaved forest (MEBF), the litter C/N ratios and lignin contents were gradually decreasing, which in turn were correlated with increasing litter decomposition constants (k-values), gradually shortening residence times of standing litter pool. And, 53.5%, 65.6% and 76.2% of the gravimetric litter mass losses were going belowground through both DOC and fragmentation. Correspondingly, the SOC accumulation rates in the top 20 cm of mineral soils for the three forests from 1978 to 2008 were 26 ± 4, 33 ± 5 and 67 ± 5 g C m⁻² yr⁻¹, respectively. Results of the study support the idea that in order to increase carbon sequestration in soils and long-term functional ability of forest ecosystems to act as carbon sinks, “Kyoto Forests” should be designed and reconstructed with a high diversity of broadleaved species, especially containing nitrogen-fixing trees.     

Comparison of soil depths between evergreen and deciduous forests as a determinant of their distribution, Northeast Thailand

In several areas in Northeast Thailand, evergreen and deciduous forests coexist under uniform terrain and climatic conditions. We compared depth and physical properties of soils between evergreen and deciduous forests in the Sakaerat Environmental Research Station to clarify what factor determines their distribution. The averaged soil depths were 79 ± 27 cm and 135 ± 58 cm in the deciduous and evergreen forests, respectively. The soils in the deciduous forests were relatively coarser in soil texture than those in the evergreen forests, particularly in the surface layers. The average available water capacity of the solum was lower in the deciduous forest soils (78 mm) than in the evergreen forest soils (123 mm). Compared with the evapotranspiration from the evergreen forest in the study area, the available water capacity of the evergreen forest soil was almost the same as the water deficit during the dry season (November–February), while that of the deciduous forest soil was lower and insufficient to maintain the evapotranspiration. These results suggest that the distribution of deciduous and evergreen forests in the study area was associated with soil water availability, which mainly depends on soil depth.     

小陇山林区蕙兰生境调查

以小陇山林区蕙兰为研究对象,通过野外调查观测,分析了蕙兰在小陇山林区的分布情况及群落结构特征。结果表明:1)蕙兰分布于106°10′169″~106°21′643″E、33°44′526″~34°08′903″N范围内,海拔925~1 350 m之间;2)蕙兰多生于次生阔叶林,常绿、落叶阔叶混交林或常绿针阔混交林下,坡度17°~47°之间;3)蕙兰呈团块状不连续分布。     

长三角城市乡土树种的天然林木群落分析与应用

长三角城市群园林绿化程度很高,但一些城市仍缺少乡土树种特色,危及生态系统稳定。长三角地跨北、中两个亚热带,有三类林木群落组成,即含有常绿阔叶树种的落叶阔叶林、落叶常绿阔叶混交林、常绿阔叶林。长三角范围乡土树种丰富,城市绿化以乡土树种为主,应大力推广应用。     

江苏虞山国家森林公园的天然植被

江苏虞山国家森林公园的森林覆盖率达96%以上.根据样地调查研究,将虞山国家森林公园约占山地面积为74.8%的天然林依群落优势种划分14类群系,为7类植被型.虞山天然林以马尾松林和马尾松、阔叶树混交林为主,山麓有落叶阔叶林和小面积的常绿、落叶阔叶林.论述虞山天然植被的组成、结构、演替和多样性指数,分析虞山天然林顺向演替的稳定性群落.结果表明:依立地环境可分3种不同类型.从演替规律来研究分析虞山植被,从而提出保护和可持续发展该森林公园植被的建议,并从旅游观光角度提出虞山部分森林类型改造的原则和方法.     

An assessment of Hawaiian dry forest condition with fine resolution remote sensing

Remote sensing offers the potential to spatially map forest cover quickly and reliably for inventory purposes. We developed a new image analysis approach using an integrated methodology of “object-based” image classification techniques and field-based measurements to quantify forest cover in a degraded dry forest ecosystem on the leeward side of the Island of Hawaii. This new approach explicitly recognized the transitional areas between tree crowns and tree shades (tree shadows) as a unique class and fully utilized them for the quantification of canopy cover. Object-oriented classification of Ikonos-2 satellite images allowed delineation of tree shades and crowns and the transitional areas between them from objects with similar reflectance and size that were surrounding the trees. These included patches of fountain (Pennisetum setaceum) and kikuyu (Pennisetum clandestinum) grass, lava outcrops and lava–grass mixtures. Crown-shade transitions were clearly differentiated in spite of their wide range of spectral values and reflectance similarities with areas of lava–grass mixture. Segments representing tree shades and dark lava outcrops were also classified into their respective classes even if they were contiguous. The image estimates of canopy cover using the tree shade plus transition classes were linearly related with field estimates of canopy cover (R² = 0.86 and slope = 0.976). Based on this relationship, dry forest cover throughout the 2627-ha area was estimated at 7.7 ± 1.9%. An immediate application of this new approach is to select and delineate areas with higher canopy cover in order to concentrate ecological restoration and conservation efforts.     

Stand structure, fuel loads, and fire behavior in riparian and upland forests, Sierra Nevada Mountains, USA; a comparison of current and reconstructed conditions

Fire plays an important role in shaping many Sierran coniferous forests, but longer fire return intervals and reductions in area burned have altered forest conditions. Productive, mesic riparian forests can accumulate high stem densities and fuel loads, making them susceptible to high-severity fire. Fuels treatments applied to upland forests, however, are often excluded from riparian areas due to concerns about degrading streamside and aquatic habitat and water quality. Objectives of this study were to compare stand structure, fuel loads, and potential fire behavior between adjacent riparian and upland forests under current and reconstructed active-fire regime conditions. Current fuel loads, tree diameters, heights, and height to live crown were measured in 36 paired riparian and upland plots. Historic estimates of these metrics were reconstructed using equations derived from fuel accumulation rates, current tree data, and increment cores. Fire behavior variables were modeled using Forest Vegetation Simulator Fire/Fuels Extension.Riparian forests were significantly more fire prone under current than reconstructed conditions, with greater basal area (BA) (means are 87 vs. 29 m²/ha), stand density (635 vs. 208 stems/ha), snag volume (37 vs. 2 m³/ha), duff loads (69 vs. 3 Mg/ha), total fuel loads (93 vs. 28 Mg/ha), canopy bulk density (CBD) (0.12 vs. 0.04 kg/m³), surface flame length (0.6 vs. 0.4 m), crown flame length (0.9 vs. 0.4 m), probability of torching (0.45 vs. 0.03), predicted mortality (31% vs. 17% BA), and lower torching (20 vs. 176 km/h) and crowning indices (28 vs. 62 km/h). Upland forests were also significantly more fire prone under current than reconstructed conditions, yet changes in fuels and potential fire behavior were not as large. Under current conditions, riparian forests were significantly more fire prone than upland forests, with greater stand density (635 vs. 401 stems/ha), probability of torching (0.45 vs. 0.22), predicted mortality (31% vs. 16% BA), and lower quadratic mean diameter (46 vs. 55 cm), canopy base height (6.7 vs. 9.4 m), and frequency of fire tolerant species (13% vs. 36% BA). Reconstructed riparian and upland forests were not significantly different. Our reconstruction results suggest that historic fuels and forest structure may not have differed significantly between many riparian and upland forests, consistent with earlier research suggesting similar historic fire return intervals. Under current conditions, however, modeled severity is much greater in riparian forests, suggesting forest habitat and ecosystem function may be more severely impacted by wildfire than in upland forests.     

Disturbance history affects lightning fire initiation in the mixedwood boreal forest: Observations and simulations

The emulation of natural disturbances such as fire is a prominent harvest management strategy for ecosystems in Canada's boreal forest region, but the effect of harvesting on subsequent lightning fire occurrence has not been studied systematically in the mixedwood boreal forest. We quantified the relationship between annual patterns of lightning fire initiation, forest composition, lightning, and fire weather conditions over eight years (1994–2001) in a 60,000 km² region of actively harvested mixedwood boreal forest in western Canada. Our analyses illustrated that forest harvesting and burning had opposite effects on subsequent fire initiation, so harvest was not a surrogate for fire. Fire initiation increased in landscapes with more area harvested and decreased with area recently burned. Our data suggested that increased fire initiation was most pronounced in harvested stands up to a decade old, and there was some evidence that the effect might last as long as 30 years. We then used a dynamic fire-succession simulation model to quantify the long-term effects of these fuel-based relationships using two metrics. As expected, the first metric demonstrated that the number of years between disturbances was significantly less in stands that were harvested and then burned, than those that were burned and then burned again. However, the more revealing component of the simulations was an illustration that despite the strong, positive relationship between harvested areas and fire initiation, the area affected over the long-term by a reduced disturbance interval was relatively small. Accordingly, our study shows that spatiotemporal regulation of lightning fire initiation through harvesting activity results in a systematic accelerated frequency of disturbance that is novel to the mixedwood boreal system, but the area affected by these events amount to local peculiarities rather than broad-scaled regularities.