昆嵛山赤松纯林赤枯病特征及与林分因子的关系

【目的】解析和定量评价林分因子对赤松赤枯病发生(发病率和病情指数)的影响,为昆嵛山赤松纯林的营林措施和赤枯病的预防提供理论指导。【方法】在昆嵛山区域选取林龄相对一致(约34年)的赤松纯林为研究对象,调查林分密度、郁闭度、树高、枝下高、胸径和冠幅6个林分因子及赤枯病的发病率和病情指数,采用方差分析、相关性分析和多重比较分析各项林分因子与赤松赤枯病之间的关系,并通过冗余分析得影响赤枯病发生的关键因子。【结果】赤枯病在赤松林中普遍发生,发病样地占调查样地的96.3%。整体上,高密度林( 2 956 ~4 089株·hm -2 )的发病率和病情指数显著高于低密度林(688~1 822株·hm -2 )和中密度林(1 823~2 955株·hm -2 )的发病率和病情指数;疏林(郁闭度<30%)的发病率和病情指数显著低于中疏林(郁闭度30%~70%)和密林(郁闭度> 70%)的发病率和病情指数;在不同的树高、枝下高、冠幅和胸径分组中,发病率和病情指数均随着分组值的增大而减小。相关性分析表明:林分密度对赤枯病发病率和病情指数的影响均达到极显著正相关水平( r =0.761, P < 0.01;r =0.748, P < 0.01);赤枯病的发病率和病情指数也均受到郁闭度的极显著影响( r =0.509, P < 0.01;r =0.442, P < 0.01);二者与树高均呈极显著正相关( r =-0.443, P < 0.01;r =-0.362, P < 0.01);赤枯病的发病率和病情指数均随枝下高的增大而极显著减小( r =-0.460, P < 0.01;r =-0.419, P < 0.01);二者与胸径均呈负相关关系,且相关性极显著( r =-0.425, P < 0.01;r =-0.373, P < 0.01);随着冠幅的增大,林木发病率和病情指数均极显著降低( r =-0.345, P < 0.01;r =-0.381, P < 0.01)。冗余分析证明林分密度和枝下高对赤枯病发生的贡献最大。【结论】松赤枯病在昆嵛山区域发生较普遍但不严重,其发病率和病情指数在不同林分因子分组中均有差异,且均受各林分因子极显著影响。RDA分析证明,林分密度和枝下高对松赤枯病影响最显著,建议对昆嵛山区域赤松纯林赤枯病的防治工作要以重要因子为主要调控对象,进行合理修剪和间伐。     

东祁连山不同退化草地植物群落特征与土壤养分特性

为探究东祁连山不同退化草地植物群落特征、土壤养分特性及其相关性,以轻度退化草地、中度退化草地和重度退化草地为研究对象,采用野外调查、室内测定和数据统计分析相结合的方法,分析了不同退化草地植被特征、土壤养分特性及其之间的相关性。结果表明:(1)从轻度退化草地-重度退化草地,植物群落特征(地上生物量、高度、密度、频度和总盖度)整体呈现降低趋势,且差异显著(P<0.05),中度退化草地Margalef指数、Shannon指数和Evenness指数最高,Dominance指数最低;(2)研究区植物共有19科38属41种,生态适应性较强的植物主要集中在豆科、禾本科、菊科和蔷薇科,不同退化草地植被型分别为矮生嵩草(K.humilis)+赖草(Leymus secalinus)、矮生嵩草+高山唐松草(Thalictrum alpinum)、矮生嵩草+赖草,其中矮生嵩草是各退化草地的优势种,不同退化草地的功能群以杂类草占优势,其次是禾草类,毒草类所占的比例最少;(3)随草地退化程度加重,土壤速效氮、有效磷、有机碳和含水量呈降低的趋势,而pH整体呈现升高的趋势;(4)不同退化草地土壤因子对植被生长贡献率最高分别为速效氮、有效磷和含水量。综上,随着草地退化程度加重,植物群落结构向单一趋势过渡,土壤养分含量减少,且土壤因子对植物贡献率也相应发生变化。     

小兴安岭林区松针资源的开发和利用

阐述了小兴安岭国有林区松针资源概述及用途,并分析了松针资源的开发和利用前景。     

1960-2015年秦岭地区极端降水的时空变化特征

极端降水是气候变化的重要研究内容之一。在全球气候变化背景下,探究秦岭地区的极端降水变化,对于明确区域极端气候差异及探究其机理具有重要的意义。基于秦岭地区1960-2015年29个气象站点降水数据以及秦岭25 m×25 m分辨率的DEM数据集,选取6个极端降水指数,运用最小二乘回归法、Man-Kendall突变检验法、5年滑动趋势法和克里金插值法研究了56年来秦岭地区极端降水的时空变化特征。结果表明:（1）秦岭地区极端降水分布存在明显空间差异性,西北部是年均连续无雨日数高值区,中西部为连续降水日数高值区;强降水日数、强降水量、5日最大降水量和降水强度等指数呈"南高北低"的分布格局,位于秦岭最南端的紫阳县是各个极端降水指数极大值区。（2）56年来,秦岭地区极端降水的持续性整体呈减少趋势;强度呈增加趋势。秦岭山地降水时间短、强度大,尤其是在秦岭南部地区,应加强防备,以免引起洪水灾害造成的重大破坏。     

Incorporating spatial non-stationarity of regression coefficients into predictive vegetation models

The results of predictive vegetation models are often presented spatially as GIS-derived surfaces of vegetation attributes across a landscape or region, but spatial information is rarely included in the model itself. Geographically weighted regression (GWR), which extends the traditional regression framework by allowing regression coefficients to vary for individual locations (‘spatial non-stationarity’), is one method of utilizing spatial information to improve the predictive power of such models. In this paper, we compare the ability of GWR, a local model, with that of ordinary least-squares (OLS) regression, a global model, to predict patterns of montane ponderosa pine (Pinus ponderosa) basal area in Saguaro National Park, AZ, USA on the basis of variables related to topography (elevation, slope steepness, aspect) and fire history (fire frequency, time since fire). The localized regression coefficients exhibited significant non-stationarity for four of the five environmental variables, and the GWR model consequently described the vegetation-environment data significantly better, even after accounting for differences in model complexity. GWR also reduced observed spatial autocorrelation of the model residuals. When applied to independent data locations not used in model development, basal areas predicted by GWR had a closer fit to observed values with lower residuals than those from the optimal OLS regression model. GWR also provided insights into fine-scale controls of ponderosa pine pattern that were missed by the global model. For example, the relationship between ponderosa pine basal area and aspect, which was obscured in the OLS regression model due to non-stationarity, was clearly demonstrated by the GWR model. We thus see GWR as a valuable complement to the many other global methods currently in use for predictive vegetation modeling.     

Reconstructing Landscape-scale Tree Invasion Using Survey Notes in the Medicine Bow Mountains, Wyoming, USA

We assessed landscape-scale invasions of openings in mountain forests by native tree species since EuroAmerican settlement (ca. 1870–1899). We reconstructed historical openings across a 250,240 ha area in the Medicine Bow Mountains, Wyoming, using notes from the original General Land Office (GLO) surveys, and compared historical openings to modern openings interpreted from digital aerial photography. We constructed logistic regression models to describe and predict tree invasion, based on a set of environmental and land use predictors. Openings have decreased by about 7.3% in the last ca. 110 years. Invasion was more likely to occur on moister sites, indicated by high values for steady-state wetness, low values for evaporative demand, proximity to streams, and topographic settings in basins or channels. More invasion also occurred on unprotected public land, in openings surrounded by lodgepole pine and aspen, and on mesic soils. The relatively slow rates of invasion in the study area may be driven by climate and land use.     

天山河谷地貌特征及其与河流产砂段关系的分析

天山河谷形态可分横向谷和纵向谷两大类,其河流长度,河谷纵坡,地貌形态各具特征。再加上新构造运动强烈程度,出露的地层岩性,大气降水和植被诸因素的差异,河流的侵蚀搬运能力迥然不同。因而致使它们的产砂地段和输砂量也大不一样。在影响因素大致相似的情况下,河谷输砂模数总的特点是:横向谷大于纵向谷;新构造运动强烈上升地段大于新构造运动较稳定地段,植被度差的地区大于植被度高的地区。     

中国天山山区药用植物资源及其保护与利用

天山山区得天独厚的自然条件孕育了丰富的药用植物资源，加上多民族聚居，三大医药体系交融等人文条件，使这些药用植物长期以来在当地居民与疾病作斗争中发挥了重要作用，据估算，整个天山山区有药用植物200多种，依功能，疗效可分为16类，在对这些资源的开发，利用与保护上，仍存在众多的问题，本文对存在的问题予以分析并提出了相应的对策；指导思想上，阐述了利用与保护的关系；利用方面，提出了加速升值研究；保护方面，提出了变消极保护为积极保护。     

天山野生果树主要病害及其分布

在对新疆天山山区的野生果树资源进行研究的同时，根据资料和野外调查，报道了在新疆野苹果（Malus sieuersii)，野杏（Armeniaca vulgaris)、野扁桃（Amygdatus ledebouriana)、野核桃（Juglans regia)、野生樱桃李（Prunus cerasifera)、野欧洲李（Prunus domestica)、稠李（Padus racemosa)、欧荚Mi(Viburnum opulus)、准噶尔山楂（Grataegus songarica)、茶蔗子（Ribes spp.)、黑果悬钩子（Rubus caesius)、黑果小檗(Berberis heteropoda)等十余种主要野生果树中常发生的29种病害以及分布等特征。     

Induction of vertical zones in sub-alpine valley forests by avalanche-formed fuel breaks

Vertical zonation of forests in high mountains is normally explained in terms of climatic variation, but avalanche tracks can act as fuel-breaks in southern Alberta Rocky Mountain forests. This is an additional way of explaining the spruce-fir (Picea engelmannii (Parry) Engelm. - Abies lascioparpa (Hook.) Nutt.) and lodgepole pine (Pinus contorta Dougl. var. latifolia Wats.) communities of the upper and lower sub-alpine zones. The hypotheses are that: 1) Fires start more often at lower than high altitude and that, as they spread into high valleys, 2) they are halted where avalanche tracks reach the valley bottom from both slopes. Also, (3) the average return interval of fires will be greater above this avalanche block, and 4) vegetation above the block will consist primarily of near-climax, fire-intolerant communities. These hypotheses were tested using the Highwood Pass (50 °21 N, 114 °26W) in the Rocky Mountains of southern Alberta, Canada. Maps of avalanche tracks and past fires, a point-centered quarter survey of forest stands, and disturbance histories established by increment coring were used to test the hypotheses which were all upheld. Thus avalanche tracks are one of the complex of factors limiting fires in the sub-alpine zone of the Alberta Rocky Mountains. The results, additionally, imply that vertical vegetation zones in temperate high mountains are influenced, not only by climatic factors, but also by avalanches and other landforms.