Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China

Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon (MBC) and nitrogen (MBN) contents and their seasonal dynamics in five forest types (a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon (TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.     

小陇山国家级自然保护区油松种群更新及生存

以种群生命表及生存分析理论为基础,以林木径级结构代表年龄结构,采用分段匀滑技术,编制小陇山自然保护区油松种群特定时间生命表,绘制死亡率曲线、消失率曲线、存活曲线、生存函数曲线,分析种群数量动态特征,并对其年龄跟胸径进行线性回归。结果表明:1.油松种群年龄结构表现为稳定型。2.油松种群死亡率和消失率曲线变化趋势基本一致,存活曲线趋于Deevey-Ⅱ型。4个生存函数曲线表明,油松种群具有前期稳定、中后期锐减和末期衰退的特点。3.油松年龄与其胸径线性相关。     

A laboratorial study on influence of alkaline and oxidative environment on preservation of Pinus tabulaeformis pollen

Different sedimentary settings can influence preservation of pollens, which would lead to misinterpretation of fossil pollen spectrum. This study investigates the influence on the preservation of Pinus tabulaeformis pollen by simulating alkaline and oxidative environment in the laboratory. There was no obvious change in the content of Pinus tabulaeformis pollen while comparing the original with the ones that were immersed with 10% NaOH liquor for ten days, or boiled for five hours, and or boiled with 20%–30% NaOH for one hour, respectively. However, the pollen fossils were obviously corroded and eroded after being boiled with 40% NaOH for one hour and were seriously corroded after five hours. The result indicates that Pinus tabulaeformis pollen is quite durable in alkaline environment and heating condition within a shorter period of time, although alkaline environment has a disadvantage for its preservation. We also tested the influence of oxidation on Pinus tabulaeformis pollen preservation with KMnO₄ as oxidant. The result presents that the number of remaining Pinus tabulaeformis pollen grains decreased quickly after being dipped in KMnO₄ along with extending the reaction time and reinforcing oxidant. The rate of remnant pollen grains was less than 1% after being dipped with 2% KMnO₄ for one hour. It is suggested that oxidative environment has stronger influence on Pinus tabulaeformis pollen preservation than alkaline environment.     

Reconstructing a cultural fire regime in the Pennsylvania Anthracite Region

Abstract

Fire history reconstructions provide fire managers with valuable information regarding historical fire regime dynamics. Yet, in the Central Hardwood Forest Region (CHF), there is an absence of dendroecological studies where frequent wildfires have persisted into the twenty-first century. This study presents the first documented tree-ring reconstruction of fire history in the Pennsylvania anthracite coal-producing region. An approximately 150-year fire chronology was developed from fire-scarred pitch pine (Pinus rigida) and sassafras (Sassafras albidum) collected on Spring Mountain in Schuylkill County. Principal component analysis and k-means cluster analysis were used to identify four fire regime clusters based on interacting fire and non-fire parameters. Results indicate that fires occurred under a variety of moisture conditions and that a mid-twentieth century increase in fire activity on Spring Mountain was associated with the collapse of the regional anthracite industry and possibly amplified by the 1960s drought. Fires continue to burn on Spring Mountain in the twenty-first century, contrary to the dominant pattern of fire exclusion across the CHF. Future research needs are highlighted regarding historical fire regime dynamics and cultural ties to landscape burning in the Pennsylvania Anthracite Region.     

Effects on catchment water balance from the management of Pinus plantations on the coastal lowlands of south‐east Queensland,Australia

A paired catchment study was conducted over a 10‐year period on the hydrology of an exotic Pinus plantation in the coastal lowlands of south‐east Queensland, Australia. Each catchment was instrumented with a stream monitoring station, tipping bucket rain gauge, and a network of piezometers to monitor the shallow perched water table. After a 6‐year calibration period a harvest treatment was imposed on one catchment (Review): clearfelling approximately 90% of the catchment area, which contained a mature (44‐year‐old) Pinus elliottii plantation. This subsequently was re‐established with a second rotation plantation of a hybrid of P.elliottii × P.caribaea var. hondurensis. The control catchment (Crayfish) contained a P. elliottii plantation similar to that clearfelled at Review. The post‐harvest period was monitored for a further 4 years. Evapotranspiration was found to be the major output flux, with stream flow only a minor component of the study catchments' water budget. Areas with gleyed podzolic soils were found to remain waterlogged for periods up to 7 months following the seasonally high summer rainfall period, with other soils having water logging periods of only a few months. Little change was observed in waterlogging characteristics following harvesting, in contrast to stream flow which increased for 3 years but with evidence of a decline after 5 years. The perched‐watertable piezometric surface indicated that its lateral drainage differs from that of surface flows; the perched‐watertable drainage fluxes from the study catchments seem minor and off‐site movement of solutes (e.g. nutrients and contaminants) via them would be limited. It was identified that the interaction between the perched and deep aquifers was poorly understood, as well as the relative importance of the soil moisture storage of the aquitard clay layer between them. It was concluded that there is a need to undertake more detailed analysis using modelling, and to obtain additional field data on soil‐layer properties and piezometric levels of the deep aquifer. Copyright © 2002 John Wiley & Sons, Ltd.     

Development of a Neolithic pine tree‐ring chronology for northern Scotland

The peatlands of northern Scotland (one of the largest and most intact areas of blanket bog in the world) contain a rare widespread horizon of subfossil pine in stratigraphic context. Eighteen bog pine from three new sites are incorporated into a mean Neolithic pine chronology now composed of subfossil pine from 12 sites, which is tree‐ring‐dated against Irish bog pine chronologies to span 3198–2757 BC. Germination and peaks of radial growth infer drier conditions between 3199 and 3130 BC. Dying‐off phases and depression of growth reflect a change to wetter conditions between 3023 and 3002 BC and a terminal decline of pine between 2809 and 2782 BC. The close synchronization of germination/die‐off phases and major ring‐width variations between sites across this region indicates that the environmental changes are probably triggered by climate change. Twenty‐four bog pine samples remain unmatched. Future multi‐discipline research into this important example of climatic change at the Neolithic/Bronze Age transition is recommended. Copyright © 2012 John Wiley & Sons, Ltd.     

秦巴山区马尾松林和油松林的空间分布及亚热带与暖温带界线划分

秦岭不仅是中国南北的地理分界线,也是中国亚热带和暖温带的气候分界线,在中国地理生态格局中占有重要的地位和作用。由于过渡带的复杂性、过渡性和异质性以及划分指标、研究目的的不同,学术界关于这一南北地理—生态分界线的具体位置一直有争论。为了进一步揭示秦巴山区过渡带的特征,明确中国南北地理—生态分界线的位置,本文选择马尾松（Pinus massoniana）林和油松（Pinus tabulaeformis）林这两类分别代表中国南方亚热带针叶林和北方温带针叶林的植被,结合研究区SRTM地形数据、气温和降水数据等,以年降水、最冷月（1月）气温、最热月（7月）气温和年均温为气候指标,详细分析了这两类植被在秦巴山区的空间分布及二者分界线处的气候条件。结果表明：① 马尾松林和油松林的分界线及相应位置的气候指标可以作为亚热带与暖温带界线划分的植被—气候指标之一。秦巴山区亚热带针叶林（马尾松林）与温带针叶林（油松林）的分界线位于伏牛山南坡至汉中盆地北缘一线（秦岭南坡）海拔1000~1200 m处;分界线处气候指标稳定：年降水750~1000 mm,年均温12~14 ℃,最冷月气温0~4 ℃,最热月气温22~26 ℃。② 通过综合的植被—气候指标来划分秦巴山区亚热带和暖温带的界线,能更科学地确定气候带分界线的位置及过渡带的特征,更全面地反映地表植被—气候格局的变化。此外,秦巴山区亚热带与暖温带的界线应该是由亚热带与暖温带针叶林分界线、阔叶林分界线、灌丛分界线等组成的一个过渡带。本文的研究结果为亚热带与暖温带划分指标的选取提供了一定的科学依据。     

Solutes in overland flow following fire in eucalyptus and pine forests,northern Portugal

Small bounded plots were used to investigate dissolved nutrient losses in overland flow in eucalyptus and pine forests in northern Portugal following understorey fires. Losses of NON, POCa²⁺, Mg²⁺ and K⁺ were measured over 19 months during the first 2–3 years after fire. Solute losses in overland flow increased after fire in eucalyptus and pine terrain due to the mineralization of litter and vegetation and increased overland flow. The data suggest that (i) elevated losses persist for at least 2 and 3 years at the pine and eucalyptus sites respectively and (ii) soluble losses of POK⁺ in a post‐fire cycle may exceed those adsorbed to eroded material. Losses of POalthough relatively small, are potentially the most detrimental to soil fertility and forest productivity because of the limited opportunity for P replenishment and correspondingly high P losses adsorbed to eroded sediment. Copyright © 2000 John Wiley & Sons, Ltd.     

武夷山黄山松林主要种群的地形格局

根据样地调查所获得的基本数据,探讨了武夷山黄山松林8个主要种群沿小地形梯度的格局特征。结果显示：黄山松种群重要值随海拔梯度的增加呈上升趋势,在〉1550m海拔梯度上显示出明显的优势地位,其在各坡度梯度和坡向梯度上优势地位都很明显;揭示了黄山松林8个主要种群沿山地地形梯度的数量变化特征及其分布的间断状况,显示了彼此之间鲜明的地形格局差异,反映出各主要种群对地形环境的适应力及其差异。