新疆表土松科花粉分布的探讨

根据新疆94个表土中松科(包括云杉属和松属,下同)花粉含量讨论其散布规律。在远离林区的荒漠、荒漠草原表土中、松科花粉普遍出现,含量较稳定。小于5%。在沙漠荒漠中,松科花粉的百分含量不稳定。在距林地10～0.5km处,松科花粉含量随近林地而明显增长。平原河谷林及低地草甸中松科花粉含量变幅较大、在高山、亚高山草甸中含量偏高,主因流水作用和地形风作用。     

Seasonal Variation in Amount and Composition of Monoterpenes Emitted by Young Pinus pinea Trees – Implications for Emission Modeling

Current inventories of terpenes released from vegetation consider only the short-term influences of light and temperature on emissions to simulate temporal variation during the year. We studied whole canopy emissions from young Pinus pinea during a 15-month enclosure in greenhouse chambers and examined data for other long-term influences. Mean daytime emission rates strongly increased during spring, reached an annual maximum of 200 pmol m^–2 total needle area s^–1 (1.1 g g^–1 leaf dry weight h^–1) between mid June and mid August, strongly declined in fall and reached an annual minimum of 1 pmol m^–2 s^–1 (0.006 g g^–1 h^–1) between January and February. Normalization to standard temperature and light conditions did not change the annual time course of emissions, but reduced summer to winter ratio from a factor of 200 to about 45. Seasonal variation was characterized also by changes in terpene composition: among the six main compounds, three (t--ocimene, linalool, 1.8-cineol) were exclusively emitted during sunlit hours in the main vegetation period, whereas the other (limonene, -pinene, myrcene) were emitted day and night and throughout the seasons. The results suggest that different terpene sources in P. pinea foliage exist and that a great part of the annual emission course observed here results from seasonal influences on these sources. A global model to simulate plant emissions is proposed, which accounts for seasonal influences on emissions in addition to the short-term effects of temperature and light. The model is tested on field data and discussed for its general application.     

Tree-ring record of hillslope erosion and valley floor dynamics: Landscape responses to climate variation during the last 400 yr in the Colorado Plateau, northeastern Arizona

Dendrogeomorphologic approaches were used to study hillslope erosion and valley floor dynamics in a small drainage basin in the Colorado Plateau of northeastern Arizona, U.S.A. Root exposure in pinyon pines indicated hillslope erosion averaged 1.9 mm/yr over the last 400 yr, but erosion has been highly episodic. Negative increment growth anomalies in hillslope trees are interpreted as the consequence of rapid aerial exposure of roots by erosion. During the last 300 yr, two of three major episodes of these growth anomalies occurred after abrupt transitions from prolonged, multi-year droughts to sustained, lengthy periods of above-average precipitation. The most recent episode of these growth anomalies began within a few years after 1905 and was associated with the largest precipitation shift (drought to wet interval) in the last 400 yr. In contrast to trees on eroding hillslopes, increment growth of trees in more geomorphically stable landscape positions closely tracked the regional precipitation signal. Two major alluvial fills on the adjacent valley floor are also linked to the abrupt changes in precipitation regimes and the associated increases in delivery of runoff and sediments from slopes. The clay-cemented sandstones weather rapidly; rapid weathering and sediment production make slopes highly responsive to decadal precipitation changes. Significant vegetation declines on slopes during extreme drought make hillslope soils more prone to erosion if heavy precipitation follows soon thereafter.     

Estimate of productivity in ecosystem of the broad-leaved Korean pine mixed forest in Changbai Mountain

We measured soil, stem and branch respiration of trees and shrubs, foliage photosynthesis and respiration in ecosystem of the needle and broad-leaved Korean pine forest in Changbai Mountain by LI-6400 CO2 analysis system. Measurement of forest microclimate was conducted simultaneously and a model was found for the relationship of soil, stem, leaf and climate factors. CO2 flux of different components in ecosystem of the broad-leaved Korean pine forest was estimated based on vegetation characteristics. The net ecosystem exchange was measured by eddy covariance technique. And we studied the effect of temperature and photosynthetic active radiation on ecosystem CO2 flux. Through analysis we found that the net ecosystem exchange was affected mainly by soil respiration and leaf photosynthesis. Annual net ecosystem exchange ranged from a minimum of about -4.671μmol·m-2·s-1 to a maximum of 13.80μmol·m-2·s-1, mean net ecosystem exchange of CO2 flux was -2.0μmol·m-2·s-1 and 3.9μmol·m-2·s-1 in winter and summer respectively (mean value during 24 h). Primary productivity of tree, shrub and herbage contributed about 89.7%, 3.5% and 6.8% to the gross primary productivity of the broad-leaved Korean pine forest respectively. Soil respiration contributed about 69.7% CO2 to the broad-leaved Korean pine forest ecosystem, comprising about 15.2% from tree leaves and 15.1% from branches. The net ecosystem exchange in growing season and non-growing season contributed 56.8% and 43.2% to the annual CO2 efflux respectively. The ratio of autotrophic respiration to gross primary productivity (Ra:GPP) was 0.52 (NPP:GPP=0.48). Annual carbon accumulation underground accounted for 52% of the gross primary productivity, and soil respiration contributed 60% to gross primary productivity. The NPP of the needle and broad-leaved Korean pine forest was 769.3 gC·m-2·a-1. The net ecosystem exchange of this forest ecosystem (NEE) was 229.51 gC·m-2·a-1. The NEE of this forest ecosystem acquired by eddy covariance technique was lower than chamber estimates by 19.8%.     

Are There Differences in the Response of Natural Stand and Plantation Biomass to Changes in Temperature and Precipitation? A Case for Two-needled Pines in Eurasia

A comparative discussion of the advantages and disadvantages of natural stands and plantations, including in terms of their productivity and stability, began from the moment of the first forest plantings and continues to this day. In the context of the progressive replacement of natural forests by plantations due to deforestation, the question of how will change the carbon storage capacity of forest cover when replacing natural forests with artificial ones in a changing climate becomes extremely relevant. This article presents the first attempt to answer this question at the transcontinental level on a special case for two-needled pine trees (subgenus Pinus L.). The research was carried out using the database compiled by the authors on the single-tree biomass structure of forest-forming species of Eurasia, in particular, data of 1880 and 1967 of natural and plantation trees, respectively. Multi-factor regression models are calculated after combining the matrix of initial data on the structure of tree biomass with the mean January temperature and mean annual precipitation, and their adequacy indices allow us to consider them reproducible. It is found that the aboveground and stem biomass of equal-sized and equal-aged natural and plantation trees increases as the January temperature and precipitation rise. This pattern is only partially valid for the branches biomass, and it has a specific character for the foliage one. The biomass of all components of plantation trees is higher than that of natural trees, but the percent of this excess varies among different components and depends on the level of January temperatures, but does not depend at all on the level of annual precipitation. A number of uncertainties that arose during the modeling process, as well as the preliminary nature of the obtained regularities, are noted.     

基于哨兵2A数据的北京松柏分布及花粉致敏风险评估初步研究

开展北京松柏植被的高分辨率空间信息提取及其花粉致敏风险评估对花粉浓度监测及预报具有重要意义。本文利用2019—2020年冬季304景高分辨率哨兵2A号（Sentinel 2A）卫星影像,引入新型增强型归一化植被指数（Enhanced normalized Vegetation Index,EVI）和地表水分指数（Land Surface Water Index,LSWI）,开展了10 m空间分辨率的北京松柏植被分布制图研究;同时依据风险评估原理,结合2020年北京松柏花粉浓度观测数据,建立了基于松柏植被分布的花粉致敏风险空间评估方法,并初步开展了影响松柏花粉浓度范围与花粉致敏风险空间评估研究。结果表明：①基于冬季合成晴空Sentinel 2A卫星影像,利用EVI和LSWI可有效提取北京10 m空间分辨率的松柏植被分布,用户精度可达80%以上;②松柏花粉观测站14 km范围内松柏植被对该站花粉浓度具有正贡献,其中6 km范围内的松柏植被贡献最大;③松柏花粉致敏相对高风险区主要分布在西北部山区、昌平北部以及门头沟东部、石景山西北和海淀西南等地区。     

Climatic significance of the stable carbon isotope composition of tree-ring cellulose: Comparison of Chinese hemlock (<Emphasis Type="Italic">Tsuga chinensis</Emphasis> Pritz) and alpine pine (<Emphasis Type="Italic">Pinus densata</Emphasis> Mast) in a temperate-moist region of China

In the reconstruction of past climate using stable carbon isotope composition (δ13C) in tree ring, the responses of the stable carbon composition (δ13C) of multiple tree species to environmental factors must be known detailedly. This study presented two δ13C series in annual tree rings for Chinese hemlock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast), and investigated the relationships between climatic parameters and stable carbon discrimination (Δ13C) series, and evaluated the potential of climatic reconstruction using Δ13C in both species, in a temperate-moist region of Chuanxi Plateau, China. The raw δ13C series of the two species was inconsistent, which may be a result of different responses caused by tree's inherent physiological differences. After removing the low-frequency effects of CO2 concentration, the high-frequency (year-to-year) inter-series correlation of Δ13C was strong, indicating that Δ13C of the two tree species were controlled by common environmental conditions. The Δ13C series of the species were most significantly correlated with temperature and moisture stress, but in different periods and intensity between the species. During the physiological year, the impacts of temperature and moisture stress on Δ13C occur earlier for Chinese hemlock (previous December to February for moisture stress and February to April for temperature, respectively) than for alpine pine (March to May for moisture stress and April to July for temperature, respectively). In addition, in temperatemoist regions, the control on Δ13C of single climatic parameter was not strongly dominant and the optimal multiple regressions functions just explained the 38.5% variance of the total. Therefore, there is limited potential for using δ13C alone to identify clear, reliable climatic signals from two species.     

松粉热解脂肪酸生物标志物的特征及其地球化学意义

现代松粉的温－压热模拟实验中，产出的轻质烃和氯仿抽提物芳烃馏份的GC－MS分析均检出大量偶数碳优势明显的脂肪酸类分子生物标志物，轻烃主要为C16，C18烷酸及其甲，乙酯，芳烃组分相对比较复杂，包括饱和脂肪酸（酯），不饱和脂肪酸（酯）和脂肪酸内酯，前者碳数分布为C15－，C30，C16，C18碳酸（酯）相对丰度占绝对优势为特征，后者碳数分布为C20-C30,以C26，C28和C30脂肪酸内酯为主，在250℃以下样品中检测出相对丰度较高的不饱和C18碳酸（酯），脂肪酸酯化合物在极低的温度条件下便可排出，并分别在200－300℃和300－400℃之间形成两次产出高峰；花粉内质体中的游离态脂肪酸及不饱和脂肪酸形成低温阶段的第一次高峰；花粉壁脂质结构中的脂肪酸及饱和脂肪酸在较高温度阶段形成第二次高峰，原样及低温样品以脂肪酸酯为主，250℃及其以上温度条件下因水解产生较多的脂肪酸，随温率继续升高，脂肪酸酯易发生脱羰反应而生成链烷烃。400℃以后因强烈降解脂肪酸酯含量大大降低，这与350－450℃之间奇数碳优势正构烷烃在轻质烃和饱和烃中的大量产出相吻合，研究表明，植物花粉是沉积有机质中饱和及不饱和C16，C18脂肪酸酯的重要母源之一。     

长白山区天然红松阔叶林乔木种多样性变化

以长白山区红松阔叶林为研究对象,采用空间代替时间的方法,对于不同年度进行中度择伐后形成的天然次生林,进行群落学调查,并根据树高划分为主林层、中林层、更新层,分析和探讨了经过人为干扰以后的28年恢复期间乔木种多样性的变化动态。研究结果表明,经人为干扰后,天然次生林内林分的乔木种丰富度和Shannon多样性指数变化均较小,林分均匀度指数在择伐后的5年间迅速减小,直至第28年为止始终小于原始林;在28年恢复期间物种丰富度指数、Shannon指数、Pielou指数、Simpson指数在不同高度层的分布格局变化均较大,且同原始林相比相差较大;林分不同层内乔木树种的多样性变化动态较复杂。     

LAND‐USE CHANGE IN THE ATLANTIC COASTAL PINE BARRENS ECOREGION

Information on the rates, characteristics, and drivers of land‐use change are vital for addressing the impacts and feedbacks of change on environmental processes. The U.S. Geological Survey's Land Cover Trends project is conducting a consistent, national analysis of the rates, causes, and consequences of land‐use change. In this article we assess change in the Atlantic Coastal Pine Barrens ecoregion from 1973 to 2000. Urban lands expanded by more than 900 square kilometers during the study period. Land‐use change in the ecoregion followed the tenets of “Forest Transition Theory” (ftt ) prior to the study period, but forest lands experienced consistent declines from 1973 to 2000. Increasing government regulation during the study period, consistent with concept of the “Quiet Revolution” (qr ), mitigated forest loss during the latter half of the study period. Generalized theories, including ftt and the qr , are valuable, but local and regional determinants of comparative land rents ultimately drive land‐use change at this scale.