Carbon pools and flux of global forest ecosystems

Forest systems cover more than 4.1 x 10(9) hectares of the Earth's land area. Globally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent at high latitudes. Over two-thirds of the carbon in forest ecosystems is contained in soils and associated peat deposits. In 1990, deforestation in the low latitudes emitted 1.6 +/- 0.4 petagrams of carbon per year, whereas forest area expansion and growth in mid- and high-latitude forest sequestered 0.7 +/- 0.2 petagrams of carbon per year, for a net flux to the atmosphere of 0.9 +/- 0.4 petagrams of carbon per year. Slowing deforestation, combined with an increase in forestation and other management measures to improve forest ecosystem productivity, could conserve or sequester significant quantities of carbon. Future forest carbon cycling trends attributable to losses and regrowth associated with global climate and land-use change are uncertain. Model projections and some results suggest that forests could be carbon sinks or sources in the future.     

江西农业生产中的伏秋干旱及其对策

本文就江西农业生产中伏秋干旱的危害，时空分布规律，成因及对策进行了初步探讨。全省伏旱、秋旱、伏秋连旱的频率分别为１０％、１６．７％和１３．３％。１９５０～１９９４年全省因伏秋干旱累计受灾面积１９３７．４万ｈｍ２，成灾面积９５６．６万ｈｍ２，累计损失粮食９５．６６亿千克；降水时空分布不均，７～９月高温少雨、水热不同步，蒸发量大于降水量１倍以上，红壤调控力弱，有效水少，是形成伏秋干旱的主因；注重蓄水、科学节水、巧种避旱是综合配套的有效抗旱途径     

Economic incentives for rain forest conservation across scales

Globally, tropical deforestation releases 20 to 30% of anthropogenic greenhouse gases. Conserving forests could reduce emissions, but the cost-effectiveness of this mechanism for mitigation depends on the associated opportunity costs. We estimated these costs from local, national, and global perspectives using a case study from Madagascar. Conservation generated significant benefits over logging and agriculture locally and globally. Nationally, however, financial benefits from industrial logging were larger than conservation benefits. Such differing economic signals across scales may exacerbate tropical deforestation. The Kyoto Protocol could potentially overcome this obstacle to conservation by creating markets for protection of tropical forests to mitigate climate change.     

Land-use allocation protects the Peruvian Amazon

Disturbance and deforestation have profound ecological and socioeconomic effects on tropical forests, but their diffuse patterns are difficult to detect and quantify at regional scales. We expanded the Carnegie forest damage detection system to show that, between 1999 and 2005, disturbance and deforestation rates throughout the Peruvian Amazon averaged 632 square kilometers per year and 645 square kilometers per year, respectively. However, only 1 to 2% occurred within natural protected areas, indigenous territories contained only 11% of the forest disturbances and 9% of the deforestation, and recent forest concessions effectively protected against clear-cutting. Although the region shows recent increases in disturbance and deforestation rates and leakage into forests surrounding concession areas, land-use policy and remoteness are serving to protect the Peruvian Amazon.     

Carbon budget of the southeastern u.s. Biota: analysis of historical change in trend from source to sink

Documentation of settlement patterns and deforestation in the southeastern United States allows evaluation of regional carbon dynamics since A.D. 1750. From 1750 to 1950, the Southeast was a net source for carbon at an average rate of 0.13 gigaton per year. Only in the past 20 to 30 years has increased productivity of commercial forests resulted in a sink for atmospheric carbon dioxide of 0.07 gigaton per year.     

地膜覆盖对半干旱地区土壤环境及作物产量的影响研究综述

地膜覆盖作为半干旱地区一项重大的旱作农业技术,具有保墒、增温、增产作用,截至2005年,已推广超过1 300万hm2。综述了覆膜对土壤水分、温度、养分、微生物及作物产量的影响。     

Global deforestation: contribution to atmospheric carbon dioxide

A study of effects of terrestrial biota on the amount of carbon dioxide in the atmosphere suggests that the global net release of carbon due to forest clearing between 1860 and 1980 was between 135 x 10(15) and 228 x 10(15) grams. Between 1.8 x 10(15) and 4.7 x 10(15) grams of carbon were released in 1980, of which nearly 80 percent was due to deforestation, principally in the tropics. The annual release of carbon from the biota and soils exceeded the release from fossil fuels until about 1960. Because the biotic release has been and remains much larger than is commonly assumed, the airborne fraction, usually considered to be about 50 percent of the release from fossil fuels, was probably between 22 and 43 percent of the total carbon released in 1980. The increase in carbon dioxide in the atmosphere is thought by some to be increasing the storage of carbon in the earth's remaining forests sufficiently to offset the release from deforestation. The interpretation of the evidence presented here suggests no such effect; deforestation appears to be the dominant biotic effect on atmospheric carbon dioxide. If deforestation increases in proportion to population, the biotic release of carbon will reach 9 x 10(15) grams per year before forests are exhausted early in the next century. The possibilities for limiting the accumulation of carbon dioxide in the atmosphere through reduction in use of fossil fuels and through management of forests may be greater than is commonly assumed.     

溪县天然常绿阔叶林研究Ⅰ.面积动态和转型

以明溪县森林资源清查体系的天然常绿阔叶林固定样地的初查、复查资料为基础，对间隔11 a的天然常绿阔叶林的变化和转型进行分析.结果表明：1985年的天然常绿阔叶林，在11 a中转型率达到37.4%，年均转型率为4.2%；其它林型(人工林、针叶林等)和地类(采伐迹地和宜林地等)转型和新增的天然常绿阔叶林占现有(1996年)阔叶林的27.8%.由于马尾松成为首选的择伐木，天然阔叶林中的针叶树大量减少，天然阔叶林趋于纯林化，1985年留存下的天然常绿阔叶林中近、成过熟林人为干扰为轻度、中度和严重的各占1/3左右，至少要禁伐11～13 a才可以恢复到1985年的森林景观水平.     

福建省沿海城市城区和郊区酸雨观测的对比分析

以2002-2003年福建省沿海11个城市的酸雨监测数据为基础,结合850 hPa高度上的风场资料,探讨各个沿海城市城郊两地酸雨的时空分布及差异.2002-2003年,福建省多数沿海城市城郊两地酸雨污染程度有一定差异,城区降水酸度主要由局地污染物的化学属性所决定,郊区酸雨污染则受外来污染物的影响;四季气象条件和850 hPa高空风向的变化都对沿海城市城郊两地酸雨污染产生一定程度的影响,并影响降水的酸性.     

2012年黑龙江省大豆市场行情分析及后市展望

在大豆生产方面,受种植效益低、农民种豆积极性低等因素影响,2012年黑龙江省大豆播种面积下降260万hm2,较2011年下降25．5％,同时播种面积的下降导致大豆产量预计为450万t,较2011年下降16．6％。2012年黑龙江省大豆市场价格总体呈现逐步上行走势。新季大豆上市后,农民惜售,企业观望,虽然在国储政策支撑下大豆价格保持4．60元／kg左右的高位,但市场持续购销不旺。     

明溪县天然常绿阔叶林研究Ⅰ.面积动态和转型

以明溪县森林资源清查体系的天然常绿阔叶林固定样地的初查、复查资料为基础 ,对间隔1 1 a的天然常绿阔叶林的变化和转型进行分析 .结果表明 :1 985年的天然常绿阔叶林 ,在 1 1 a中转型率达到 37.4% ,年均转型率为 4.2 % ;其它林型 (人工林、针叶林等 )和地类 (采伐迹地和宜林地等 )转型和新增的天然常绿阔叶林占现有 (1 996年 )阔叶林的 2 7.8% .由于马尾松成为首选的择伐木 ,天然阔叶林中的针叶树大量减少 ,天然阔叶林趋于纯林化 ,1 985年留存下的天然常绿阔叶林中近、成过熟林人为干扰为轻度、中度和严重的各占 1 /3左右 ,至少要禁伐 1 1～ 1 3a才可以恢复到 1 985年的森林景观水平     

我国80年代杉木林资源动态及营林对策的思考

本文概述了80年代我国杉木林资源动态,特点是面积、蓄积有所增加,单产下降,中幼林比重大,成熟林少,青黄不接的现象严重,后备资源比较乐观。杉木林面积在人工林总面积中比重偏大,产区森林组成针叶化趋势严重。指出营林对策是明确指导思想,集约经营,提高单产,提倡生态营林,注意林地的持续利用。     

中国油菜生产与品种改良

９０年代,中国油菜生产发展很快,面积在５３０×１０＾４（１９９３年）～６９０（１９９５年）×１０＾４ｈｍ＾２,单产１２００～１４００ｋｇ／ｈｍ＾２。１９８５～１９９８年,中国共审定优质常规品种８８个,其中双低品种４３个,单低品种４５个;最近两年,中国双低品种的种植面积占２７％～３４％。１９８９～１９９８年,中国共审定油菜单、双低杂交种３０个,其中双低杂种１３个,单低杂种１７个;杂 交油菜的种植面积     

Determination of deforestation rates of the world's humid tropical forests

A recently completed research program (TREES) employing the global imaging capabilities of Earth-observing satellites provides updated information on the status of the world's humid tropical forest cover. Between 1990 and 1997, 5.8 +/- 1.4 million hectares of humid tropical forest were lost each year, with a further 2.3 +/- 0.7 million hectares of forest visibly degraded. These figures indicate that the global net rate of change in forest cover for the humid tropics is 23% lower than the generally accepted rate. This result affects the calculation of carbon fluxes in the global budget and means that the terrestrial sink is smaller than previously inferred.     

飞播云南松林下真菌的时空分布特征

人造飞播云南松,是建国以后50年代利用飞机营造的最成功的人工林区,云南松是四川省凉山州的优势树种,占所有树种的90%,分布面积大,林下的真菌分布种类较多.为了对保护飞播云南松林下的真菌资源提供基础数据,于2004-2006年对四川省凉山州人造云南松野生真菌的生态分布进行了调查.结果表明:凉山州飞播云南松的林下共计生长有23科25属189种(含变种)真菌,其生长与分布主要受到气候、海拔高度、植被、地形特征、土壤条件、光的辐射和人为干扰的影响而发生变化,真菌生长的黄金时期为7-9月的高温多雨季节;人类的干扰作用是影响真菌生长最直接的负面因素,是加剧真菌资源枯竭的主要原因.     

海南中部山区天然林物种组成与群落特征变化

为了揭示受20世纪50年代砍伐影响的热带天然林在自然恢复过程中物种组成与群落特征变化趋势,以海南中部山区山地雨林原始林、低地雨林次生林、山地雨林次生林、云雾林次生林4个森林动态样地为对象,基于2012—2020年2次植被调查,从物种组成、区系组成、群落外貌特征等方面分析群落动态特点。结果表明：2012—2020年,（1）山地雨林原始林S?rensen群落相似度为0.960,物种组成最稳定;低地雨林次生林为0.921;山地雨林次生林为0.889;云雾林次生林为0.794,物种更替最明显。随着短期演替进行,各群落间S?rensen群落相似度升高,多年来有更多相同的物种。（2）各群落排名第1的优势种重要值均降低,云雾林次生林优势种重要值下降明显,向更为混合的多优势种群落发展。（3）随着短期演替进行,群落郁闭度增加,喜阳的前中期树种逐渐被耐荫的演替中后期种替代,分布区窄的海南特有种作为补员树种进入群落。（4）各群落均以热带区分布为绝对优势,并以热带亚洲（印度-马来西亚）分布为主。随海拔升高,温度降低,呈现出热带性减弱、温带性加强的特点。8年间,植物区系地理成分更加复杂。（5）叶性质呈现出以中型...     

模拟酸雨淋溶对缙云山针阔混交林与常绿阔叶林凋落物分解的影响

【目的】探讨缙云山针阔混交林与常绿阔叶林凋落物分解在酸雨过程中的特点和规律,为优化缙云山森林管理,指导林分配置提供科学依据。【方法】以重庆缙云山2种典型林分为研究对象,进行4个不同酸碱度：pH 4.50(对照)、pH 4.00、pH 3.25和pH 2.50的酸雨模拟实验,结合Olson负指数衰减模型,分析针阔混交林与常绿阔叶林的凋落物分解速率并计算分解系数,定量分析模拟酸雨下2种典型林分的凋落物分解变化规律。【结果】(1)经过0.5 a的分解,对照、pH 4.00、pH 3.25和pH 2.50处理下针阔混交林质量残留率均高于常绿阔叶林,分别高4.60%、3.78%、4.22%和5.39%。其中,对照针阔混交林凋落物损失率达到半衰期与全衰期的时间为1.62、6.98 a,常绿阔叶林为1.29和5.56 a;不同酸碱度酸雨淋溶下针阔混交林凋落物损失率达50%和95%的时间分别为1.47～2.00和6.35～8.43 a,常绿阔叶林分别为1.23～1.50和5.33～6.48 a。(2)对照、pH 4.00、pH 3.25和pH 2.50各处理下针阔混交林的分解常数k值分别为0.43、0...     

Selective logging in the Brazilian Amazon

Amazon deforestation has been measured by remote sensing for three decades. In comparison, selective logging has been mostly invisible to satellites. We developed a large-scale, high-resolution, automated remote-sensing analysis of selective logging in the top five timber-producing states of the Brazilian Amazon. Logged areas ranged from 12,075 to 19,823 square kilometers per year (+/-14%) between 1999 and 2002, equivalent to 60 to 123% of previously reported deforestation area. Up to 1200 square kilometers per year of logging were observed on conservation lands. Each year, 27 million to 50 million cubic meters of wood were extracted, and a gross flux of approximately 0.1 billion metric tons of carbon was destined for release to the atmosphere by logging.     

马达加斯加的热带森林

马达加斯加是非洲大陆的离岛。天然森林类型复杂多样。原生性的森林群落主要为常绿林，落叶林以及多刺、肉质的落叶灌木丛。在不同类型的岩石露头发育着岩生矮林；高山上可见山顶矮林，滨海湿地则为红树林。马达加斯加的森林有着独特的植物和动物种类，有着巨大的生物多样性。但由于人类长期对其生境的破坏，不少动物种类已处于濒危状态。到目前为止，60％－85％的森林植被已遭到破坏。非持续的农业轮作是森林植被完整性的主要威胁。在某些地区，火烧林地建立牧场业是引起森林面积减少的主要因素。     

按植物群落生态学特性,加速恢复大兴安岭火烧迹地的森林

1987年5月份,在我国大兴安岭北部发生了特大森林火灾,过火面积达100万ha以上,引起国内外高度重视。为了尽快恢复大兴安岭北部火烧迹地的森林,提出按植物群落生态学特性,依据其森林的组成、分布、生长和更新规律,加速恢复火烧迹地森林的建议。为不同类型落叶松林火烧迹地的迅速恢复,以及合理经营、利用与保护提供了理论依据及途径。