A geospatial model of forest dynamics with controlled trend surface

This paper proposes a method of controlled trend surface to simultaneously account for large-scale spatial trends and non-spatial local effects. With this method, a geospatial model of forest dynamics was developed for the Alaska boreal forest from 446 constantly monitored permanent sample plots. The geospatial component of this model represented large-scale spatial trends in recruitment, diameter growth, and mortality. The model was tested on two sets of validation plots which represented temporal and spatial extensions of the current sample coverage. The results suggest that the controlled trend surface model was generally more accurate than both the non-spatial and conventional trend surface models. With this model, we mapped the forest dynamics of the entire Alaska boreal region by aggregating predicted stand states across the region. It was predicted that under current conditions of climate and natural disturbances, most of the Alaska boreal forest region may undergo a major shift from deciduous-dominant to conifer-dominant, with an average increase of 0.33 m² ha year⁻¹ in basal area over the Twenty-First Century.     

森林凋落物分解研究进展

森林凋落物是指森林生态系统内由生物组分产生,然后归还到林地表面的所有有机物质的总称。森林凋落物在促进森林生态系统正常的物质循环和养分平衡,维持生态系统功能中具有重要作用,其分解受多因素影响,且各因素之间相互交错。不同情况下,各因子的重要性可能不同。温度和湿度被认为是影响凋落物分解主要的气候因子。凋落物随着温度升高分解速率加快,增加土壤湿度对凋落物分解有积极作用。凋落物的化学性质中,C、N比和木质素含量被认为是最重要的指标。凋落物分解前期的分解速率受到养分含量、水溶性碳化合物和结构碳化合物含量的强烈影响,而后期则更多地受到木质索及纤维素／木质素比值的支配。土壤动物可以粉碎凋落物,土壤微生物也是促进凋落物分解的重要因素,人为活动也影响凋落物分解。N沉降、全球变暖和臭氧层破坏等全球变化对森林凋落物分解的影响已逐渐成为研究热点。未来凋落物分解的研究方向是统一研究方法,开展长期定位监测,加强对分解过程中有机碳含量和释放量的研究,以及N沉降对凋落物分解作用机理的研究。     

密云水库上游流域不同林分土壤有机碳分布特征

在全球气候变化背景下,森林土壤有机碳库作为全球土壤碳库的重要组成部分,已成为全球碳循环研究的重点之一。以密云水库上游流域天然次生山杨（Populus davidiana Dode）、白桦（Betula platyphylla Suk.）混交林、天然次生辽东栎（Quercus wutaishanica Blume）林、人工华北落叶松（Larix principis-rupprechtii Mayr.）林、人工油松（Pinus tabulaeformis Carr.）林和灌丛等5种典型林分为研究对象,选取典型样区,进行密集采样和试验分析,探讨了不同林分土壤有机碳质量分数和密度的分布特征。结果表明：在整个土壤剖面上（0~40 cm）,不同林分土壤有机碳质量分数和密度大小顺序均为：杨桦林〉辽东栎林〉灌丛〉落叶松林〉油松林,总体上呈现出随土地利用强度和人为干扰程度增加而降低的变化趋势,即天然次生林比人工林更有利于土壤有机碳的储存和积累;不同林分类型土壤有机碳质量分数和密度均在表层（0~10 cm）最大,并随着土层深度的增加呈下降趋势,剖面分布差异明显;此外,不同林分在0~20 cm土层中的单位面积土壤有机碳储量均占其剖面总储量的57%以上,即土壤有机碳富集在0~20 cm深的表层土体中。因此,为增加森林土壤固碳,应加强对天然次生林的保护,减少人类活动对森林及其表土层的干扰。     

马鬃岭自然保护区土壤碳蓄积的研究

以金寨马鬃岭自然保护区为研究对象,布置56个采样点,分析该区森林土壤有机碳质量分数时空分布特征和碳储量。结果表明：研究区有机碳含量丰富,随着土壤深度、植被类型、海拔高度的变化而变化。0~20cm土层有机碳质量分数最高为90.88 g·kg-1,平均为32.47 g·kg-1,土壤有机碳质量分数随着深度的增加而递减,表层有机碳变化幅度高于深层土壤,不同测点递减的程度不同;有机碳质量分数随海拔高度的增加呈递增趋势;土壤有机碳质量分数存在明显的季节变化,表层土壤秋季有机碳质量分数最高,冬春季次之,夏季最低,越往表层季节变化越明显。0~20 cm土层有机碳密度平均为6.52 kg.m-2,0~100 cm土层有机碳平均密度为23.26 kg.m-2,有机碳密度分布与有机碳质量分数分布基本一致。0~20 cm土层土壤碳储量为2.258×105~2.265×105 t,0~100 cm土层土壤碳储量为6.91×105~8.76×105 t,碳储量丰富。最后提出该自然保护区封山育林,对温室气体减排意义重大。     

森林生态系统恢复力评价——以江西省莲花县为例

生态系统恢复力是森林资源可持续发展的中心目标之一。在明确生态系统恢复力定义和尺度的基础上,分析了森林生态系统恢复力的影响因素,从生境条件和生态存储两方面遴选出26个指标,建立了森林生态系统恢复力评价指标体系,并以江西省莲花县为案例区,采用组合赋权法确定了指标权重,通过空间叠加计算了莲花县森林生态系统恢复力。结果表明:森林生态系统恢复力主要受内部存储的影响,其权重达到0.554。莲花县森林生态系统恢复力在0.103到0.464之间,平均值为0.268,恢复力达到或超过平均水平的森林面积为37 907 hm²,占森林总面积的49.2%,整体处于较低水平;分级结果表明仅48.16%的森林达到高或较高恢复力水平;在空间分布上,莲花县森林生态系统恢复力为南高北低,南部和中部的森林大多处于高或较高恢复力水平,北部地区大部分森林处于中等、较低或低恢复力水平。此外,恢复力高的森林沿乡镇边界线分布的特点非常明显。该研究结果可为森林资源管理提供重要科学依据。     

山西省永定河流域林草植被生态需水研究

以山西永定河流域及周边17 个气象站点1957—2000 年的气象资料为依据,在GIS支持下,从时空角度定量分析了山西永定河流域林草植被生态需水及其在不同植被类型、流域不同地区及植被生长期内的分配。研究结果表明: 山西永定河流域植被建设最小生态需水量为1 628.5×10⁶ m³,对应的盈余水量为653.5×10⁶ m³,适宜生态需水量为2 709.5×10⁶ m³,对应的生态缺水量为427.5×10⁶ m³;降雨总体上能满足相应面积草、灌、乔植被生长期最小生态需水及草地适宜生态需水,基本满足灌木植被的适宜生态需水,不能满足乔木植被适宜生态需水;生态缺水较多的区域主要是大同、怀仁和左云等地,缺水时段集中在4—6 月。关键词:生态需水;林草植被;GIS;山西永定河流域     

北方地区典型天气对城市森林内大气颗粒物的影响

以北京西山几种游憩型城市森林为例,在一年四季选择典型天气条件,对4种粒径的大气颗粒物浓度进行全天24h监测,研究北方地区不同季节典型天气因素白昼不同时段对不同结构的城市森林内不同粗细粒径的大气颗粒物浓度变化的影响.结果发现:降雨使大气颗粒物浓度减少,尤其粗颗粒物(TSP只为连续晴天的0.58~0.68),所以雨后晴天粒径较小的颗粒物所占比例会增加.不过,有时在雨后的夜间由于空气湿度大大气颗粒物浓度也会增加.雪能够降低大气颗粒物浓度,“雪后晴天”4种粒径颗粒物浓度均只有连续晴天的0.2倍.多云和雾霾天气使大气颗粒物污染加重,尤其在夜间;雾霾和多云对小粒径颗粒物浓度的增加效果明显.夏季高温高湿静风、闷热的“桑拿天”能使郁闭度较大的林地内大气颗粒物特别是细颗粒物浓度及其所占的比例显著增加,PM2.5的浓度是“连续晴天”的2.53倍.风在雨后能使大气颗粒物在一定程度上扩散减少,而在天气干燥时刮风会增加城市森林内大气颗粒物的浓度,且多云会加重干燥天气刮风后大气颗粒物的污染程度.春、冬季林地裸露的落叶阔叶树在刮风时大气颗粒物浓度较四季常绿、地表覆盖物多的针叶林高,夏、秋季桑拿天和雾霾天郁闭度大的侧柏林大气颗粒物浓度较林地结构开阔的黄栌林高.     

林下凋落物去除与施氮对针叶林和阔叶林土壤氮的影响

通过野外模拟试验,选择中亚热带针叶林(杉木林)和阔叶林(浙江桂林和罗浮栲林)森林生态系统,设3个施氮水平CK(对照)、低氮〔30kg/(hm2·a) 〕和高氮〔100kg/(hm2·a)〕及2个凋落物处理,研究施氮对土壤主要形态氮质量分数的影响、动态变化及凋落物在其中的作用. 结果表明:与CK相比,高氮处理可瞬时(3d)提高森林土壤氮质量分数,但施氮后持续效应的影响降低. 与保留凋落物相比,去除凋落物在施氮的持续效应中,可降低阔叶林土壤w(铵态氮)18.2%,而杉木林土壤的氮质量分数则略有升高.去除凋落物下施氮的持续和瞬时效应可增加各种林下土壤的w(硝态氮),其中浙江桂林土壤w(硝态氮)分别增加58.9%和38.2%,罗浮栲林土壤分别增加7.0%和30.0%,杉木林土壤分别增加-17.1%和9.0%. 可见凋落物在施氮连续事件中存在复杂的短期和长期相互影响. 阔叶林土壤w(SON)(SON为可溶性有机氮)较高,并且其微生物w(SON)及其占微生物w(TN)的比例高于杉木林土壤,而杉木林土壤微生物w(铵态氮)及其占微生物w(TN)的比例高于阔叶林土壤.      

Lignin and its effects on litter decomposition in forest ecosystems

Lignin is a major component of plant litter. In this review, we found lignin comprises a complex class of organic compounds whose concentration differs greatly both between and within plant species. There are many analytical methods for detecting the composition and structure of lignins. As lignins are enormously complex compounds, chemical assay is difficult and different methods vary with the results. Lignin plays a significant role in the carbon cycle, sequestering atmospheric carbon into the living tissues of woody perennial vegetation. It has also great effects on nitrogen dynamics of forest ecosystems as well as other ecological processes. Lignin is one of the most slowly decomposing components of dead vegetation, contributing a major fraction of the material that becomes humus as it decomposes. Lignin is highly correlated with decomposition of litter. Thus, there is evidence that the lignin concentration is a more influential factor than the other chemical concentrations, in determining the rate of leaf litter decomposition of different forest ecosystems. Although a great number of researchers have addressed lignin's role in litter decomposition, still there are many aspects of lignin biogeochemistry that are not known. This lack of information hinders complete amalgam of lignin effects on litter decomposition processes and dynamics of nutrient cycling.     

Concentrations of polycyclic aromatic hydrocarbons in soils of a mangrove forest affected by forest fire

Surface soils affected by forest fires from Igbanko mangrove forest in Nigeria were analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs) using gas chromatography–mass spectrometry (GC–MS). The total PAHs concentrations in the soils ranged from 63 to 188?µg?kg^?1 dry weight (average: 108?µg?kg^?1). The three predominant PAHs in the soils were naphthalene (Na), fluoranthene (Flu), and benzo(b)fluoranthene (BbF). Compared to the control sample (19?µg?kg^?1), elevated PAHs concentrations were observed in the soils, an indication of some level of PAHs contamination. PAHs source diagnostic ratios of Flu/(Flu?+?Pyr) and Ant/(Ant?+?Phe) indicated that the PAHs have a pyrogenic origin which may have resulted from combustion of grass, wood, or coal. An assessment based on Canadian soil quality guidelines indicated that the studied locations do not pose any serious adverse risk on human health.