A system-wide assessment of forest biomass production,markets, and carbon

This study examines the effects of supplying forest biomass on forest ecosystem services and goods with a dynamic systems model. This unique analysis models dynamic trade and investments in forestry, thereby capturing price changes from increased forest biomass demand on current and future flows of forest ecosystem services and natural capital stocks. Forests across the globe are interconnected through timber and forest biomass markets, which influence forest management decisions, land rents, and policy responses. Results indicate that expanding forest biomass consumption, even at relatively low levels, will have important impacts on ecosystem services, particularly the benefits of terrestrial carbon sequestration and timber outputs. Increased forest biomass production can be achieved with smaller impacts on ecosystem services through policies targeting natural forest preservation. However, policies that encourage residual biomass use for energy or discourage forest plantation expansion could potentially compromise carbon benefits.     

Site and temporal variation of soil respiration in European beech, Norway spruce, and Scots pine forests

Global warming and changes in rainfall amount and distribution may affect soil respiration as a major carbon flux between the biosphere and the atmosphere. The objectives of this study were to investigate the site to site and interannual variation in soil respiration of six temperate forest sites. Soil respiration was measured using closed chambers over 2 years under mature beech, spruce and pine stands at both Solling and Unterlüß, Germany, which have distinct climates and soils. Cumulative annual CO₂ fluxes varied from 4.9 to 5.4 Mg C ha^?1 yr^?1 at Solling with silty soils and from 4.0 to 5.9 Mg C ha^?1 yr^?1 at Unterlüß with sandy soils. With one exception soil respiration rates were not significantly different among the six forest sites (site to site variation) and between the years within the same forest site (interannual variation). Only the respiration rate in the spruce stand at Unterlüß was significant lower than the beech stand at Unterlüß in both years. Soil respiration rates of the sandy sites at Unterlüß were limited by soil moisture during the rather dry and warm summer 1999 while soil respiration at the silty Solling site tended to increase. We found a threshold of ?80 kPa at 10 cm depth below which soil respiration decreased with increasing drought. Subsequent wetting of sandy soils revealed high CO₂ effluxes in the stands at Unterlüß. However, dry periods were infrequent, and our results suggest that temporal variation in soil moisture generally had little effect on annual soil respiration rates. Soil temperature at 5 cm and 10 cm depth explained 83% of the temporal variation in soil respiration using the Arrhenius function. The correlations were weaker using temperature at 0 cm (r² = 0.63) and 2.5 cm depth (r² = 0.81). Mean Q₁₀ values for the range from 5 to 15 °C increased asymptotically with soil depth from 1.87 at 0 cm to 3.46 at 10 cm depth, indicating a large uncertainty in the prediction of the temperature dependency of soil respiration. Comparing the fitted Arrhenius curves for same tree species from Solling and Unterlüß revealed higher soil respiration rates for the stands at Solling than in the respective stands at Unterlüß at the same temperature. A significant positive correlation across all sites between predicted soil respiration rates at 10 °C and total phosphorus content and C‐to‐N ratio of the upper mineral soil indicate a possible effect of nutrients on soil respiration.     

Forest Structure and Biomass of a Tropical Seasonal Rain Forest in Xishuangbanna,Southwest China1

Xishuangbanna is a region located at the northern edge of tropical Asia. Biomass estimates of its tropical rain forest have not been published in English literature. We estimated forest biomass and its allocation patterns in five 0.185–1.0 ha plots in tropical seasonal rain forests of Xishuangbanna. Forest biomass ranged from 362.1 to 692.6 Mg/ha. Biomass of trees with diameter at 1.3 m breast height (DBH) ≥ 5 cm accounted for 98.2 percent of the rain forest biomass, followed by shrubs (0.9%), woody lianas (0.8%), and herbs (0.2%). Biomass allocation to different tree components was 68.4–70.0 percent to stems, 19.8–21.8 percent to roots, 7.4–10.6 percent to branches, and 0.7–1.3 percent to leaves. Biomass allocation to the tree sublayers was 55.3–62.2 percent to the A layer (upper layer), 30.6–37.1 percent to the B layer (middle), and 2.7–7.6 percent to the C layer (lower). Biomass of Pometia tomentosa, a dominant species, accounted for 19.7–21.1 percent of the total tree biomass. The average density of large trees (DBH ≥100 cm) was 9.4 stems/ha on two small plots and 3.5 stems/ha on two large plots, illustrating the potential to overestimate biomass on a landscape scale if only small plots are sampled. Biomass estimations are similar to typical tropical rain forests in Southeast Asia and the Neotropics.     

泉州针叶林的特征与分布

泉州的针叶林以马尾松林最为普遍,广泛分布于海拔1300 m以下的山地,有天然林和人工林。杉木林主要为人工林,也分布子海拔1300 m以下。黄山松林均为天然林,分布于海拔1100~1300 m的山地,与马尾松林交叉生长,在海拔1300 m以上成为纯林,直至近戴云山山顶(海拔1856 m)。福建柏林仅在一些林场有人工栽种。对以上群落类型的区系成份、生活型、叶特征以及群落结构的分析,表明它们具有亚热带常绿针叶林的群落特征。     

The impacts of increasing drought on forest dynamics,structure, and biodiversity in the United States

We synthesize insights from current understanding of drought impacts at stand‐to‐biogeographic scales, including management options, and we identify challenges to be addressed with new research. Large stand‐level shifts underway in western forests already are showing the importance of interactions involving drought, insects, and fire. Diebacks, changes in composition and structure, and shifting range limits are widely observed. In the eastern US, the effects of increasing drought are becoming better understood at the level of individual trees, but this knowledge cannot yet be confidently translated to predictions of changing structure and diversity of forest stands. While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought. Throughout the continental United States, the combination of projected large climate‐induced shifts in suitable habitat from modeling studies and limited potential for the rapid migration of tree populations suggests that changing tree and forest biogeography could substantially lag habitat shifts already underway. Forest management practices can partially ameliorate drought impacts through reductions in stand density, selection of drought‐tolerant species and genotypes, artificial regeneration, and the development of multistructured stands. However, silvicultural treatments also could exacerbate drought impacts unless implemented with careful attention to site and stand characteristics. Gaps in our understanding should motivate new research on the effects of interactions involving climate and other species at the stand scale and how interactions and multiple responses are represented in models. This assessment indicates that, without a stronger empirical basis for drought impacts at the stand scale, more complex models may provide limited guidance.     

Habitat,Climate, and Fisher and Marten Distributions

Since the mid-twentieth century, fisher populations (Pekania pennanti) increased in several eastern jurisdictions of North America, particularly in the northern part of the species’ range. Changes in fisher distribution have led to increased overlap with the southern portion of the range of American marten (Martes americana), whose populations may be locally declining. This overlap occurs particularly in habitats undergoing natural and anthropogenic modification. The objective of our study was to determine the respective effects of habitat changes and climatic conditions on fisher and marten populations in Quebec, Canada, based on trapper knowledge. We analyzed annual fisher and marten harvest (number of pelts sold/100 km²) between the 1984–1985 and 2014–2015 trapping seasons using linear mixed models. Fisher harvest increased with the increased abundance of mixed forests >12 m tall, resulting from decades of forest harvesting. Fisher harvest decreased with increasing spring rains, which can affect survival when rearing young. Marten harvest decreased with increasing winter rains, which lower thermoregulation capacity and hamper movements by creating an ice crust on the snowpack, reducing access to subnivean areas. Decline in marten harvest during the 30-year study period coincided with an increase in fisher harvest, suggesting possible interspecific competition. Results highlight that managers should strive to maintain mixedwood stands taller than 12 m to maintain high quality habitat for fishers. Our study confirms the importance of working with trappers to assess furbearing population trends in response to habitat changes and climatic conditions. © 2019 The Wildlife Society.     

西双版纳不同森林类型的树洞密度及其特征

树洞是森林生态系统的重要组成部分,它能为许多动物提供栖息、筑巢、繁殖和躲避天敌的场所。因而,树洞的密度和特征通常被认为是限制树洞巢居动物多样性和丰富度的主要因子,然而目前国内外对热带森林的树洞密度和洞口特征研究较少。选取西双版纳20 hm~2热带森林动态监测样地(包括热带季节雨林和热带山地常绿阔叶林)为研究对象,采用地面观测法调查了所有胸径≥5 cm的活体乔木上的树洞,分析其树洞密度和特征(高度、洞口大小、类型和洞口方位,并探讨树洞在不同森林类型间的差异)。结果表明:(1)热带季节雨林和热带山地常绿阔叶林的树洞密度不存在显著差异;(2)两种森林类型的树洞均以高度较低、洞口较小、干中部洞口为主,受盛行风的影响洞口朝向主要集中在东北方向;(3)树洞高度、类型和洞口方位在两种森林间的分布差异显著(P0.01),而洞口大小不存在明显差异。结果表明森林类型会影响树洞的特征,因而加强森林生境异质性的保护对维持树洞巢居动物的需要具有重要意义。     

Assessing onset and length of greening period in six vegetation types in Oaxaca,Mexico, using NDVI-precipitation relationships

Variations in the normalized vegetation index (NDVI) for the state of Oaxaca, in southern Mexico, were analyzed in terms of precipitation anomalies for the period 1997-2003. Using 10-day averages in NDVI data, obtained from AVHRR satellite information, the response of six types of vegetation to intra-annual and inter-annual fluctuations in precipitation were examined. The onset and temporal evolution of the greening period were studied in terms of precipitation variations through spectral analysis (coherence and phase). The results indicate that extremely dry periods, such as those observed in 1997 and 2001, resulted in low values of NDVI for much of Oaxaca, while good precipitation periods produced a rapid response (20-30 days of delay) from a stressed to a non-stressed condition in most vegetation types. One of these rapid changes occurred during the transition from dry to wet conditions during the summer of 1998. As in many parts of the tropics and subtropics, the NDVI reflects low frequency variations in precipitation on several spatial scales. Even after long dry periods (2001-2002), the various regional vegetation types are capable of recovering when a good rainy season takes place, indicating that vegetation types such as the evergreen forests in the high parts of Oaxaca respond better to rainfall characteristics (timing, amount) than to temperature changes, as is the case in most mid-latitudes. This finding may be relevant to prepare climate change scenarios for forests, where increases in surface temperature and precipitation anomalies are expected.     

50年来山东塔山植被与物种多样性的变化

为分析塔山植被与物种多样性50a自然演替和动态变化,2009-2010年,采用系统勘踏法和典型取样法进行了调查。当前塔山主要植被类型为"黑松林-赤松林-栓皮栎林"。50a间,该区针叶林从黑松(Pinus thunbergii)林演替为黑松林、赤松(P. densiflora)林和油松林(P. tabulaeformis)为主的混合针叶林,但针叶林的整体优势度下降,以栓皮栎(Quercus variabilis)和麻栎(Q. acutissima)为建群种的阔叶林面积明显增大,由针叶林向阔叶林的演替趋势明朗。物种丰富度为草本层>灌木层>乔木层,Shannon-wiener指数和Simpson指数为灌木层>草本层>乔木层,物种多样性较低,处于森林演替初期。     

热带、亚热带典型森林-土壤系统植硅体碳演变规律

分别选取中国亚热带毛竹林、马尾松林、青冈林、杉木林和热带青梅林、芭蕉林、橡胶林、马占相思林8种森林类型,采集其鲜叶、凋落叶以及0～10和10～30 cm土层土壤,通过微波消解法提取其中的植硅体,并采用碱溶法测定植硅体中碳含量.结果表明: 4种亚热带森林类型鲜叶、凋落叶和0～10 cm土层中植硅体碳含量均以马尾松林(230.24、229.17、20.87 g·kg^-1)最高,毛竹林(30.55、37.37、3.38 g·kg^-1)最低,10～30 cm土层则以青冈林(18.54 g·kg^-1)最高,毛竹林(2.90 g·kg^-1)最低.热带森林鲜叶中植硅体碳含量以马占相思林(377.66 g·kg^-1)最高,青梅林(46.83 g·kg^-1)最低,凋落叶中则是橡胶林(218.23 g·kg^-1)最高,芭蕉林(27.66 g·kg^-1)最低,而0～10和10～30 cm土层土壤中均以马占相思林(23.84、24.90 g·kg^-1)最高,芭蕉林(3.89、3.93 g·kg^-1)最低.与0～10 cm表层土相比,杉木林、青冈林、马尾松林、毛竹林、橡胶林、马占相思林、芭蕉林和青梅林鲜叶植硅体碳含量分别下降97.4%、94.9%、90.9%、88.9%、95.9%、93.7%、93.3%和63.7%.青冈林、芭蕉林和马占相思林鲜叶植硅体碳含量显著高于凋落叶,而毛竹林、马尾松林、杉木林、青梅林和橡胶林之间无显著差异.8种森林类型土壤植硅体碳含量均显著低于鲜叶和凋落叶,表明植硅体在通过凋落物释放到土壤的过程中是不稳定的.     

Spatial hints of forest ecotone indicating forest succession, a case of larch forests in Baihuashan Reserve, north China

In cold or alpine areas of northern China, birch forests and larch forests are the two primary forest types. These forests are also characteristic of a south branch of boreal forests in Asia. Some ecologists argue that larch forests can replace birch forests, but this still remains a question due to fragmentary or short observations. The ecotone between a larch forest patch and a birch forest patch is the arena in which the two species interplay and compete with each other, and studies of these areas are meaningful to understanding forest succession. In the alpine area of the Baihuashan Reserve, northern China, we sampled a larch-birch forest ecotone with eight plots in four transects and then analyzed population structures of larches and birches. The results show that the edges of the larch forest patch are composed of many larch saplings or young trees, but the edges of the birch forest patch are mainly composed of old birches. Across the ecotone, the larches, on average, are taller than the birches. These facts suggest that larch saplings can permeate into birch forest patches, probably by seed dispersal, germination, success-ful competition and growth, but birch saplings cannot permeate into larch forest patches. Therefore, on the ecotone, larch forest patches can steadily expand by unceasing permeation into birch forest patches, whereas birch forest patches progressively recede due to ultimate death of the old and poor recruitment of the young. Larch forest patches replace birch forest patches in a stepwise manner, causing succession from birch forests to larch forests. This study not only confirms that larch forests can naturally replace birch forests, but also introduces a simple and reliable method, employing spatial hints, to study forest succession. Additionally, the findings are of benefit to cultivation or development of larch forests in cold or alpine areas of the North Temperate Zone, which can be a huge carbon sink.     

海南霸王岭山地原始林与伐后林中木质藤本对支持木的选择

通过对海南霸王岭热带山地原始林与伐后林中树木及其攀附木质藤本的调查,研究原始林与伐后林中木质藤本对支持木的选择性。结果表明:1)6科优势树木中附藤率最高的是野牡丹科(Melastomataceae),附藤率最低的科,原始林中是山矾科(Symplocaceae),伐后林中是茜草科(Rubiaceae)。2)原始林中,谷木(Memecylon ligustrifolium)与线枝蒲桃(Syzygiumaraiocladum)的附藤比率和每木藤本数均高于样地平均水平;三角瓣花(Prismatomeris tetrandra)和龟背灰木(Symplocosandenophylla)的附藤比率均低于样地平均水平,而每木藤本数与样地平均水平之间没有显著差异。伐后林中,谷木的附藤比率和每木藤本数高于样地平均水平;九节(Psychotria rubra)的附藤比率和每木藤本数低于样地平均水平。3)杜仲藤(Parabariummicranthum)的主要支持木是谷木,夜花藤(Hypserpa nitida)的主要支持木是线枝蒲桃。研究表明,木质藤本对支持木在科和种水平上都具有选择性,因此木质藤本会对树木造成不对称影响,进而影响森林的结构和动态。     

Leaf domatia in Korean plants: floristics,frequency, and biogeography

Leaf domatia, specialized structures on the undersides of leaves, appear to promote mutualism between plants and those mites that protect leaves from pathogenic fungi and small herbivorous arthropods. Their occurrence was surveyed on 425 plant species (368 native species and 57 species introduced from other regions of northeastern Asia), comprising 177 genera and 59 families of woody Dicotyledonae in the Korean flora. Domatia, primarily of tuft or pocket forms (84% of species), were present in vein axils on leaves of 152 species (36%) within 66 genera (37%) and 39 families (66%). Overall, we report leaf domatia in nine new families and 25 additional genera. Mites, primarily from families or suborders (e.g., Acaridida, Phytoseiidae, Tydeidae) in which arboreal representatives are primarily fungivorous or predaceous, were found in domatia on leaves of 78% of all species sampled. Domatia frequency depended upon both growth form and habit of species. They were especially common among tree species (55%), but less so on shrubs (20%) and woody vines (22%). Domatia were much more frequent on species of deciduous plants (40% of those sampled) than on evergreen species, of which only 10% had leaf domatia. This difference was consistent across a number of local deciduous and broadleaf evergreen forests in South Korea. The high frequency of leaf domatia in this survey indicates that plant-mite mutualism may be widespread in Korean plant communities. The floristic affinities of plants with domatia in Korea to those in other regions of East Asia, eastern North America, and Europe suggest that these plant-mite associations characterize the temperate broadleaf deciduous forest biome in the Northern Hemisphere.     

Forest elephant group composition, frugivory and coastal use in the Réserve de Faune du Petit Loango, Gabon

Results of a 16‐month study of forest elephant (Loxodonta africana cyclotis Matschie) group size and composition, coastal use and frugivory are presented from the Réserve de Faune du Petit Loango, Gabon (now the Parc National de Loango). Mean forest elephant group size was 2.2 (n = 140) including solitary animals, and 3.1 excluding solitaries. Elephants consumed fruits of at least 49 species, and of the 220 elephant dungpiles examined, 185 (84.1%) contained seeds and 203 (92.3%) contained the remains of fruits (seeds and/or pulp). The mean number of seed species per dungpile (±SD) was 2.01 ± 1.49, and the mean number of fruit species was 2.28 ± 1.43. Elephants used the coastal habitat more during warmer months, and during the afternoon than the morning. It is hypothesized that coastal habitat use is related to sodium intake through consumption of salt‐coated vegetation.     

Seasonally flooded,and terra firme in northern Congo: Insights on their structure,diversity and biomass

In the Congo basin, considerable uncertainty remains about the amount and spatial variation of carbon stocks. We studied two types of seasonally flooded forests (dominated by Guibourtia demeusei and Lophira alata) and nearby terra firme forests in northern Congo. We sampled 1.25 ha per forest type and a total of 1,400 trees ≥5 cm diameter. AGB ranged from 207–343 Mg/ha, with no significant differences between forest types. Few significant differences were observed in vegetation structure or tree diversity between forest types. Species richness and stem density of small trees were lower, and dominance was higher in Guibourtia plots, which are subject to greater flooding than Lophira plots. Guibourtia was absent from smaller diameter class in Guibourtia forests; and Uapaca spp. were more abundant in terra firme than in seasonally flooded plots. We show that both types of seasonally flooded forests store important quantities of AGB and should also be considered in forest conservation programmes. We recommend more research on seasonally flooded forests, on larger geographical extent, which assesses flood depth and duration, and measures tree height in the field, as we took a conservative approach to AGB estimates, and AGB could be even greater than we report here.