干旱区对降水变化响应的研究进展

水分是干旱区的主要限制因子之一,降水是干旱区最重要的水分来源。根据气候变化研究的预测,未来我国干旱区的降水格局会改变,包括降水量、降水频率和降水强度等。降水变化会影响干旱区的土壤变化,植被变化,土地荒漠化和水文变化等方面。我国极端干旱区和干旱区的降水有总体增加趋势,而部分半干旱区和亚湿润干旱区的降水则出现减少趋势。降水的增加能够促进生物土壤结皮的发育,改善土壤水分状况,促进植物生长,提高植被盖度,促使荒漠植被向草原植被方向发展,有利于土地荒漠化的逆转;另外,降水增加会增加河流的径流量和湖泊水量,促进洪水的发生,降水减少则具有相反的效应。这些研究有助于人们预测干旱区在未来降水格局改变之后可能发生的变化,对于天然植被保育以及荒漠化防治等实践工作等具有重要的理论指导意义。未来的研究需要加强实验,如增雨、升温、模拟氮沉降和CO₂浓度增加等对干旱区的土壤、植被、荒漠化和水文等方面的影响,才能获得更有说服力的结果。     

松华坝水源区迤者小流域径流和泥沙变化特征

通过实地观测、实验分析及数据处理,对松花坝水源区迤者小流域的径流和泥沙进行了初步研究,通过探究径流和泥沙变化特征来揭示该区水土流失的原因,以采用合理的方法治理该区水体流失。结果表明：松花坝水源区迤者小流域5～10月的降雨量最大,降雨是产生径流和泥沙的主要因素,但不是唯一因素,降雨、径流、泥沙之间存在着正相关的关系,如8月4日降雨深度达到39．4mm,径流总量达到88．12m^3,产沙量达到150．68kg。又如9月19日降雨深度只有0．2mm,径流总量只有0．22m^3,产沙量也只有0．01kg。降雨具有周期性和随机性,而径流和泥沙的日变化规律和降雨历时、采样时间及土地利用类型有很大的关系。我们只能分析径流和泥沙的大致变化趋势,而无具体的变化规律。     

成都市土地利用时空结构变化研究

随着经济的高速发展,城市化对土地利用结构变化的影响较大,土地利用时空结构变化研究对土地规划及可持续发展具有重要意义.本文对成都市2000—2020年的土地利用数据进行处理,计算土地利用年变化率(R)、土地利用程度综合指数和土地利用变化量(S),得出以下结论:(1)耕地和建设用地变化幅度较大,总体呈增大的趋势;林地和其他...     

大桂山林场的生态环境与林木速生丰产

文章通过林场的长期实践,观察了森林植被的形成,林区气温、湿度、土壤、水分等生态因子相继发生了变化,这些因子的变化有利于防火、防虫,促进林木生长。     

苦楝花粉飘散对林内空气颗粒物浓度的影响

针对城市绿化建设中气传花粉导致的植源污染，开展气传致敏花粉传播的时空变化规律及其对林内空气颗粒物浓度的影响研究，为防控城市气传致敏花粉污染提供依据。以成都市绿化使用频率较大、典型气传致敏花粉植物-苦楝为研究对象，选择苦楝的盛花期，开展气传致敏花粉的日变化飘散规律和水平空间传播规律研究，结果表明：(1)苦楝花粉浓度的日变化呈单峰曲线，即花粉浓度从6:00—14:00持续上升，并在14:00达到峰值；14:00—20:00则持续下降；12:00—15:00的花粉飘散浓度显著性高于其余时段。(2)苦楝花粉浓度的水平方向上，顺风方向花粉浓度高于逆风方向；顺风方向花粉浓度变化呈单峰曲线，随着距离的增加而增加，并在20 m处达到峰值；逆风方向花粉的飘散浓度呈双峰曲线，峰值出现在9 m和20 m。(3)受苦楝花粉飘散的影响，香樟林内空气颗粒物浓度在水平空间上的含量分布趋势与花粉浓度变化趋势大致相同，也表现为顺风方向高于逆风方向；在水平距离上，苦楝花粉对空气颗粒物的影响主要在0—30 m范围。     

3种薯蓣植物珠芽休眠过程中糖类和可溶性蛋白质含量及淀粉酶活性的变化规律

经作相关的试验研究了山药、日本薯蓣、黄独3种薯蓣植物的珠芽休眠过程中淀粉、可溶性糖、还原糖、可溶性蛋白质含量和淀粉酶活性的变化规律.结果表明,在其休眠过程中3种薯蓣植物珠芽的淀粉含量均呈上升趋势,休眠结束时与休眠初期相比,珠芽休眠期最长的山药其淀粉含量极显著增加,珠芽休眠期较长的日本薯蓣其淀粉含量显著增加,仅珠芽休眠期最短的黄独其淀粉含量上升不大;3种薯蓣植物珠芽休眠过程中其可溶性糖含量呈下降趋势,可溶性糖含量的降低与淀粉含量的升高相关;3种薯蓣植物珠芽休眠过程中其还原糖含量呈上升趋势,与淀粉含量变化相似,其中山药珠芽的还原糖含量极显著增加,日本薯蓣珠芽的还原糖含量显著增加,黄独珠芽的还原糖含量增加不显著,还原糖含量的升高促进了珠芽的发芽;3种薯蓣植物珠芽休眠过程中其可溶性蛋白质含量均呈上升趋势;3种薯蓣植物珠芽休眠过程中的淀粉酶都以α-淀粉酶为主,珠芽休眠期短的黄独其α-淀粉酶活性一直保持较高水平,而珠芽休眠期长的山药在休眠初期其淀粉酶活性显著低于其他两种薯蓣植物.     

2013～2020年湖南省大气二氧化硫浓度变化特征分析

利用湖南省区域内14个城市2013～2020年二氧化硫日浓度资料及相关参数,对湖南省环境空气中的二氧化硫浓度变化特征进行了综合分析和评价。结果表明：在2013～2020年,全省二氧化硫排放总量的下降与全省城市空气质量中二氧化硫的浓度下降密切相关;城市环境空气中的二氧化硫浓度逐年降低,下降幅度最大的城市是张家界市、湘西州和益阳市;二氧化硫浓度整体呈湖南中南部较高,西部和北部较低;冬季对二氧化硫浓度贡献大,夏季贡献小。近年来湖南省二氧化硫污染控制成效显著,可为其他大气污染因子的防治和管控提供参考。     

人工杨树林空气负离子浓度时间变化规律研究

通过全年12个月对人工杨树林内空气负离子浓度的连续观测,结果表明:林内空气负离子浓度日变化在不同季节均表现为单峰型变化,即夜间数值最低,最低值出现在凌晨前后,最高值出现在下午13-16时。1年中林内空气负离子浓度春夏较高,秋冬较低,夏季高温期6、7月有所降低。从1年的时间段来看,林内空气负离子浓度与温度有显著正相关,与湿度相关性不显著。     

南方型和北方型美洲黑杨幼苗光合作用的日季节变化

在自然条件下,采用Li-6400便携式光合作用测定系统研究了南方型和北方型美洲黑杨在5、7、9月的光合日变化。结果表明:南方型美洲黑杨在5月和9月的净光合速率日变化为单峰曲线,峰值分别为15.79、14.13 μmol·m^-2·s^-1,在7月为双峰曲线,最高峰值为22.03 μmol·m^-2·s^-1;北方型美洲黑杨在5、7、9月的净光合速率日变化一直为双峰曲线,最高峰值分别为13.46、18.08、12.91 μmol·m^-2·s^-1。南方型美洲黑杨仅在生长旺盛的7月存在光合"午休"现象;北方型美洲黑杨在整个生长季均存在光合"午休"现象;南北方型美洲黑杨净光合速率季节变化特点为:夏季(7月)>春季(5月)>秋季(9月);10月份,南方型美洲黑杨净光合速率达到12.70 μmol·m^-2·s^-1,北方型美洲黑杨已落叶。分别对南方型和北方型美洲黑杨5、7、9月的光合有效辐射、气温、空气相对湿度、空气CO₂浓度与净光合速率进行逐步多元回归、偏相关及通径分析,影响净光合速率的主要生态因子是光合有效辐射。     

Progress in Study on Response of Arid Zones to Precipitation Change

The pattern of precipitation,including precipitation amount,frequency and intensity,may change in the future according to the prediction of climate change.In arid zones,the soil dynamics, plant growth and vegetation change,desertification and hydrology might be affected by precipitation change.In general,the precipitation in extreme arid zone and arid zone showed an increase tendency whereas the precipitation in some area in semi-arid zone and sub-humid arid zone showed a decrease tendency.The increase of precipitation could enhance the growth of biological soil crust,improve soil water status,promote plant growth,increase vegetation coverage,facilitate the change from desert vegetation to grassland vegetation,and it is benefit to the reversion of land desertification.In addition,the increase of precipitation could also increase the river runoff,lake storage and promote the occurrence of flood,while the decrease of precipitation has the adverse effect.These studies will benefit the prediction of the possible response of ecosystem processes to the potential change of precipitation pattern in arid zones in the future,and it is important to the conservation of natural vegetation and the control of desertification.More field experiments and studies should be conducted in the future,including the effect of increased precipitation or temperature,nitrogen deposition and CO₂ on soil,vegetation,desertification and hydrology of arid zones,so as the more persuasive results could be obtained from these experiments and studies.     

Effect of climate change and land use on stream flow in the upper and middle reaches of the Taoer River,northeastern China

The upper and middle reaches of the Taoer River, a representative ecologically sensitive area, has experienced great climate     

云南省沙化土地现状及治理对策

云南省虽无沙漠和大面积集中连片的沙地,但也是水土流失、山体滑坡、泥石流等导致土地沙化较严重的省份之一。通过沙化监测,定期掌握云南省沙化土地的现状、动态变化信息,为国家和云南省制定防沙治沙的政策和长远发展规划,为保护、改良和合理利用国土资源和云南省生态文明建设考核目标体系提供依据,实现可持续发展战略提供基础资料;通过分析云南省沙化土地变化原因及治理情况,为下一步云南省防沙治沙提供意见建议。     

Greenhouse gas emissions between 1993 and 2002 from land-use change and forestry in Mexico

In this paper we present the Mexican inventory of greenhouse gas (GHG) emissions from the land-use sector. It involved integration of forest inventory, land-use and soil data in a GIS to estimate the net flux of GHG between 1993 and 2002.     

山西省森林资源消长分析

以森林资源一类清查数据为基础,对建国50多年来山西省森林资源的变化进行了分析,重点论述了建国后森林资源的消长动态及当前森林结构严重失调的状况。     

The Spring Change in Hydraulic Architecture Characteristics in Some Woody Plants

Ten healthy tree species with regular management were selected on the campus of Beijing Forestry University, and they belong to tall tree, shrub and liana, respectively. Water potential and hydraulic architecture parameters of one-year-old twigs were measured in sunny day in the last ten days of March to the middle ten days of May in 2002. The results show that the daily change in water potential of tree species examined appears convex, i.e. the water potential is higher in the morning and evening, and lower in the midday. The change trend of water potential is consistent among different months. The seasonal change trend of water potential appears lower in March than that in April and May. There is a similar relationship between the daily change trend of water potential and special conductivity in spring, i.e. the higher the water potential, the higher the special conductivity, but this trend of change is not entirely synchronic. The seasonal change of special conductivity of conifer species is not obvi     

鄂尔多斯耕地变化及其驱动因子分析

利用1947-2008年的近61年序列统计数据,通过分析总体耕地面积变化及其区域差异特征,得出了以下结果:鄂尔多斯市耕地总面积变化呈波动后缓慢下降再上升之势.从1947年到1961年耕地面积变化呈波动状态,1961-1987年耕地面积缓慢减少,1987-2008年耕地面积变化呈上升之势.其耕地总量变化状态主要有3个增长...     

Avian population and community processes in forest ecosystems: Long-term research in the Hubbard Brook Experimental Forest

Long-term studies in relatively undisturbed forest ecosystems, such as occur in many of the USFS’ Experimental Forests, provide valuable insight into bird population and community processes, information pertinent to forest management and bird conservation. Major findings from 40 years of research in the Hubbard Brook Experimental Forest in north-central New Hampshire reviewed here show that the distributions and abundances of bird species are dynamic, even within well-developed and mature forests, and that species respond differently to habitat (vegetation) structure, food availability, and other features of the forest environment. At the local scale, bird population demography is most affected by factors that influence fecundity and recruitment, mainly food availability, weather, nest predators, and density dependent processes. Fecundity is strongly correlated with subsequent recruitment and is critical for maintaining breeding population size. Events in the non-breeding season, however, also influence the abundance and demography of breeding populations, indicating the need to assess factors operating throughout the species’ annual cycle. At the landscape scale, populations in temperate forests are spatially structured by each species’ response to habitat and environmental patterns, but also by social interactions such as competition and conspecific attraction. Settlement patterns and ultimately reproductive performance depend on habitat quality, based on vegetation structure, food availability and nest predator effects that vary across the landscape. Results from these long-term studies centered at Hubbard Brook provide a mechanistic understanding of avian population dynamics and community responses. The results provide a framework for predicting how future changes in habitat quality, climate, and other environmental threats may influence bird populations and communities in north-temperate forests.