利用生物地球化学模型研究草地生态系统土地变化对生态环境的影响

分析了生物地球化学循环中植物—土壤生态系统的有机物动态,土壤有机质(SOM)主要库类——土壤C,N,P,S循环特点;阐述了土壤有机质的生物地球化学循环模型CENTURY结构。利用CENTURY模型模拟土地利用变化情形下内蒙古草原生态典型区土壤有机质动态。由数值模拟结果分析看,CENTURY对自然和人为活动影响下生态系统的土壤有机质动态有良好的模拟能力,同时又可有效地反映土地利用类型变化对生态环境和土壤侵蚀的影响。     

甘肃环县天然草地植被近40年演变的研究

环县地处陇东黄土高原北部,面积9 326 km2,其天然植被为森林草原与荒漠草原过渡地带.通过对40年前后天然草地植被的比较研究,得出40年来在自然和人类共同作用下,天然草地植被演变的结果是:天然分布的原生植被基本被天然次生植被所替代,植被组成更趋于简单化,天然生长的乔木和灌木群系消失,地带性顶极植被类型短花针茅、长芒草和大针茅群系消失,小面积分布的部分群系消失,各群系中次优势种发生了改变,植被的生态学特征发生变化,生态功能显著降低,天然草地植被严重退化,造成这一结果的主要原因是人类的垦荒、砍伐和过度放牧,而非自然因素的作用.     

The effect of water table depth on emissions of N2O from a grassland soil

Nitrous oxide (N₂O) emissions were measured by the closed chamber technique from five plots along a transect in a nitrogen‐fertilised grassland, together with soil water content, soil temperature and water table depth, to investigate the effect of water table depth on N₂O emissions. N₂O fluxes varied from <1 g N₂O‐N ha^?1 day^?1 to peaks of around 500–1200 g N₂O‐N ha^?1 day^?1 after N fertiliser applications. There was no significant difference in overall average water table depth between four of the five plots, but significant short‐term temporal variations in water table depth did occur. Rises in the water table were accompanied by exponential increases in N₂O emissions, through the associated increases in the water‐filled pore space of the topsoil. Modelling predicted that if the water table could be managed such that it was kept to no less than 35 cm below the ground surface, fluxes during the growing season would be reduced by 50%, while lowering to 45 cm would reduce them by over 80%. The strong implication of these results is that draining grasslands, so that the water tables are only rarely nearer to the surface than 35 cm when N is available for denitrification, would substantially reduce N₂O emissions.     

寒区旱区间歇性干旱对接种根瘤菌苜蓿草地土壤养分动态的影响

通过盆栽法模拟田间土壤的干湿交替变化过程和强度,研究了寒区旱区间歇性干旱条件对接种根瘤菌(Rhizobia)苜蓿(Medicago sativa L.)草地土壤养分的影响。结果表明:1年龄苜蓿接种根瘤菌能显著提高土壤全N、有机质、速效N、速效K和速效P含量,而对土壤pH和全P含量影响不大,间歇性干旱处理能显著降低土壤全N、有机质、全P、速效N、速效P和速效K含量,且土壤养分下降量总体上为有机质>全P>全N>速效K>速效N>速效P;通过相关和回归分析,土壤全P和有机质含量的下降量与干湿交替间隔周期呈显著直线正相关(P<0.05),土壤速效K和速效P含量的下降量与干湿交替间隔周期呈显著直线负相关(P<0.05);当干湿交替间隔周期相同时,土壤全N、全P、速效N和有机质含量的下降量,50%田间持水量的处理大于80%田间持水量的处理,而土壤速效K和速效P含量的下降量,50%田间持水量的处理小于80%田间持水量的处理。     

半干旱黄土丘陵区不同整地方式下退化草地植物群落恢复特征

[目的]对比分析2种造林整地措施处理后的草地植物群落特征,为宁南半干旱黄土丘陵区植被恢复和建设提供理论依据。[方法]以固定样地与群落样方调查数据为基础,对比了"88542"水平沟、鱼鳞坑2种不同整地方式下群落动态特征。[结果](1)在一定的时间尺度上,生境的异质性对鱼鳞坑整地植物群落的结构影响较大,整地方式对植物群落结构特征的影响不明显。(2)生境条件的不同影响了群落的多样性。鱼鳞坑整地的植物群落由于生境的异质性较大,促成了较高的多样性。植物群落物种多样性由高到低的顺序为:鱼鳞坑整地"88542"水平沟整地天然封育草地。(3)植物群落多样性总体表现出随着年限的延伸,整个示范区的植物群落物种的多样性开始下降。[结论]不同人为干扰方式和不同生境对植物群落多样性有明显影响。     

Experimental determination of climate‐change effects on above‐ground and below‐ground organic matter in alpine grasslands by translocation of soil cores

We used the soil‐core translocation method to investigate the effect of increased temperature on above‐ and below‐ground phytomass and organic matter in cool alpine areas. The translocation of undisturbed soil cores from a high alpine site (2525 m a.s.l.) to an alpine site near the timberline (1895 m a.s.l.) achieved an effective artificial warming of 3.3 K. From a methodological point of view, the translocation of soil cores was performed successfully. Soil cores moved to a new site at the same altitude showed no change in above‐ and below‐ground vegetation, bulk density, and soil skeleton. At both sites, soils were Haplic Podzols with a similar chemistry and clay mineralogy. At the lower elevation site, however, podzolization processes seemed to be more pronounced. As a consequence, the translocation of the soil cores probably led to a disturbance of the actual steady state that had been established after about 10,000–13,000 years of soil formation. This might have affected the adaptability of the vegetation system. Therefore, it cannot be fully excluded that the experimental design influenced the results. Translocation of soil cores from a very cool to a warmer site led to a distinct decrease in above‐ground phytomass (about –45%) over the experimental period of two years. Below‐ground phytomass significantly decreased (up to –50%) in the topsoil (0–5 cm) after artificial warming. Possible mechanisms are that roots reduced photosynthesis and hence C flow below‐ground, a reduction of soil moisture that would have led to root death (not a very probable cause, however) or an abrupt change in the radiation duration and flux which affected root growth (also not very probable). Fast climate change exceeded the ability of the above‐ground and below‐ground phytomass to adapt quickly. Whether the decrease in phytomass was a short‐term or a long‐term response to climate warming remains uncertain. Based on a gradient study (climosequence at the same locality), we hypothesize that the decreased plant productivity might be a short‐term effect.     

陕西黄土高原地区退耕与粮食补助模式研究

在陕西黄土高原地区分区基础上 ,对各区未来 2 0年粮食供需状况进行预测 ,并根据未来粮食供需形势 ,选择了陕西黄土高原地区最优的退耕和粮食补助模式     

宁夏南部黄土丘陵区退化天然草地改良效果综合评价

采用多层次模糊综合评判法,综合分析了宁夏南部黄土丘陵区不同改良措施下的改良效果,结果表明：“88542”整地＋播种综合评判值最高,达到5.9188,改良效果最好,施肥和封育的综合评判值其次,带状翻耕＋播种的综合评判值最低,仅为2.7750,远低于对照。     

黄土丘陵区退耕地生物结皮影响下的土壤腐殖质分异特征

本文对黄土丘陵区退耕地生物结皮影响下的土壤腐殖质分异特征进行了研究。结果表明,①该区生物结皮影响下的土壤腐殖质组分HA、FA和HM含量均有明显的分层特征,土层间均表现出:结皮层0～2cm土层2～5cm土层;不同年限生物结皮土壤腐殖质含量总体表现出:16年8年32年12年,表明退耕地生物结皮影响下的土壤腐殖质含量随时间变化呈非线性变化趋势;HA/FA平均值变化范围为0.34～0.70,低于1,该区生物结皮影响下的土壤腐殖质胡敏酸含量不高,腐殖酸以富啡酸为主;②结皮层土壤腐殖酸E4/E6值随时间变化总体上呈"抛物线"型变化趋势;而0～2cm和2～5cm土层土壤腐殖酸E4/E6值呈缓慢增长的趋势;③腐殖质组分与土壤养分因子的全N、NO3--N、NH4+-N和有效Zn之间存在极显著的线性相关关系(p0.01);④土壤腐殖质组分含量的变化与全N、NO3--N、NH4+-N和有效Zn含量间存在满足二项式的函数回归关系(p0.01),表明生物结皮对土壤C素与N素和有效Zn的影响密切相关。     

Grassland nature reserves for breeding wading birds in England and the implications for the ESA agri-environment scheme

The two principal mechanisms available to conserve breeding wading birds on lowland wet grassland in England are nature reserves and agri-environment schemes, particularly the Environmentally Sensitive Area (ESA) scheme. ESAs offer payments to landowners in return for maintaining (‘low tiers’) or enhancing (‘high tiers’) the landscape, biodiversity and historic value of the land. Lowland wet grassland nature reserves managed by the Royal Society for the Protection of Birds (RSPB) have been successful at conserving breeding lapwings and redshank but habitat management usually only results in short-term increases in numbers of breeding snipe. Within ESAs, populations of breeding wading birds fare better on land managed under high tiers than on land managed under low tiers. Land managed under high tiers also supports more pairs of breeding wading birds per £ of ESA grant received than land managed under low tiers. Means of increasing the cost-effectiveness of the ESA scheme in conserving breeding wading birds are discussed in the light of these results.