Soil CO2 efflux in a temperate deciduous forest: Environmental drivers and component contributions

Soil CO₂ efflux is a large component of total respiration in many ecosystems. It is important to understand the environmental controls on soil CO₂ efflux, in order to evaluate potential responses of ecosystems to climate change. This study investigated the relationship between total soil CO₂ efflux and soil temperature, soil moisture and solar radiation on an interannual basis for a plot of temperate deciduous ancient semi-natural woodland at Wytham Woods in central southern England. We also aimed to quantify the contribution of soil organic matter decomposition (SOM), root-and-rhizosphere respiration, and mycorrhizal respiration components to total soil CO₂ efflux, and determine their environmental correlates. Total soil CO₂ efflux was measured regularly from April 2006 to December 2008 and found to average 4.1 Mg C ha⁻¹ yr⁻¹ in both 2007 and 2008. In addition, we applied a recently developed approach to partition the efflux into SOM, root-and-rhizosphere, and mycorrhizal components in situ using mesh bags. SOM decomposition, root-and-rhizosphere, and mycorrhizal respiration were estimated to contribute 70 ± 6%, 22 ± 6% and 8 ± 3% of total soil CO₂ efflux respectively, equating to 3.0 ± 0.3, 0.9 ± 0.2 and 0.3 ± 0.1 Mg C ha⁻¹ yr⁻¹. In order to avoid the effect of temporal correlation between variables caused by seasonality, we investigated interannual variability by examining the relationship between CO₂ flux anomalies and anomalies in environmental variables. Variation in soil temperature explained 50% of the interannual variance in soil CO₂ efflux, and soil moisture a further 18% of the residual variance. Solar radiation, as a proxy for plant photosynthesis, had no significant effect on total soil CO₂ efflux, but was positively correlated with root-and-rhizosphere respiration, and mycorrhizal respiration. The relationship between anomalies in soil CO₂ efflux and soil temperature was highly significant, with a sensitivity of 0.164 ± 0.023 μmol CO₂ m⁻² s⁻¹ °C⁻¹. For mean peak summer efflux rates (2.03 μmol CO₂ m² s⁻¹), this is equivalent to 8% per °C, or a Q₁₀ temperature sensitivity of 2.2 ± 0.2. We demonstrate the utility of an anomaly analysis approach and conclude that soil temperature is the key driver of total soil CO₂ efflux primarily through its positive relationship with SOM-decomposition rate.     

基于3S技术的黄龙山林地时空动态变化及驱动力分析

利用黄龙山林区1986年、1997年、2008年3期Landsat TM遥感影像,在"3S"技术支持下分析了黄龙山近20a林地变化的时空特性。同时,结合国民经济统计资料及其他相关资料,对黄龙山林地变化的驱动力进行分析,并建立了各类林地的社会经济驱动力模型。结果表明:1986-2008年黄龙山林地经历了较大幅度的波动变化。主要表现为有林地和其他林地面积持续增加;灌木林地、疏林地面积逐年减少。林地内部存在相互转化,主要转化方向为灌木林、疏林地向有林地转化。相比于1986-1997年、1997-2008年黄龙山林区林地的转化速率在逐渐减缓,有趋于向稳定状态发展。同时,驱动力模型揭示,国民生产总值与黄龙山林区有林地及其他林地变化有较大相关性,灌木林地面积变化主要受社会固定资产总投入影响,农业人口比重是黄龙山林区疏林地变化的重要影响因素。     

半干旱农牧交错区人工林退化:概化模型和现状评价

在干旱半干旱地区,造林通常被作为荒漠化防治最为有效的措施之一,然而这一区域人工林退化也是不可回避的事实。本文以半干旱农牧交错区的内蒙古伊金霍洛旗为例,对其林地退化状况进行评价。根据野外调查结果我们建立了一个林地退化概化模型,据此筛选出湿润指数、植被指数、土壤类型和土壤侵蚀模数4个评价指标,并采用GIS对该区人工林退化状况进行评价。结果表明,在336.09km2人工林中,退化面积达311.35km2,其中轻度、中度和重度退化面积分别为78.97,119.73和112.65km2。退化人工林的防治重点应放在现有林的改良和造林植物种特别是灌木种的选择上。图4参15。     

大理州集体林权制度改革研究

在林业"三定"和分类经营的基础上,阐述大理州集体林权制度改革的主要做法和取得的初步成效,分析现阶段集体林权制度改革面临的问题:规模化、集体化经营困难,林木采伐管理难度加大,农村烧材矛盾凸现等.探索下一步工作思路:进一步落实完善集体林经营体制、积极探索林改配套措施、调整完善林木采伐政策等.     

基于QuickBird影像的退耕地林分类型识别方法研究

[目的]减少遥感数据的噪声影响,提高光谱信息的传统林分类识别方法的提取精度。[方法]在MNF变换融合处理的基础上,采用一种基于光谱和空间信息相结合的分类方法,融入空间信息对研究区不同林分遥感信息进行提取。[结果]该方法可以有效地抑制分类结果的"麻点"现象,对各类型林分信息的平均提取精度达83.6%,高于传统最大似然法11.6%。[结论]融入空间信息的林分信息提取方法可以有效地改善分类效果,能够提高分类精度,在退耕地林分信息提取和变化监测等方面具有一定的实际意义。     

Metal concentrations in agricultural and forestry soils in northwest Spain: implications for disposal of organic wastes on acid soils

Abstract In Galicia (northwest Spain) the application of organic wastes to agricultural land is a common practice, which may increase total and bioavailable metal contents in the soil. In this study, total metal concentrations were determined in acid soils under different use (pasture, cropland, woodland) in an agricultural area where agro-industrial sludges are frequently recycled as manure. The aim was to establish baseline metal levels which could be used to determine the capacity of soils to absorb organic wastes. The estimation of baseline metal concentrations was carried out by two methods, one based on the analysis of means and geometric deviations, and another based on a modal analysis. Results suggested that the modal analysis procedure might be preferable when analysing data sets with a heterogeneous frequency distribution. In general, there was no significant difference in total metal concentrations when comparing soils from different land uses. Baseline levels for each metal indicated that all soils were suitable for organic waste application under current European Union (EU) legislation. From 2015, more restrictive metal limit values have been proposed by the EU, potentially preventing the addition of metal-containing wastes to pasture, cropland and woodland soils. The dissolved metal values in each soil were also estimated by empirical equations relating total metal concentrations, pH and organic matter content. Results showed that only the pasture soils would be suitable for organic waste disposal under the proposed EU metal limits for 2015, due to liming and substantial organic matter content. Total metal concentrations were insufficient to discriminate environmental risk in acid soils of different land use. The determination of baseline levels in reference areas and the estimation of soil metal bioavailability are suggested to define permissible values in the developing legislation.     

Regional diversity of mycetophilids (Diptera: Sciaroidea) in Scandinavian oak-dominated forests

Mycetophilids is a species-rich insect group for which the ecological requirements in temperate forests are poorly understood. This study of mycetophilids was based on trap samples from 15 oak-dominated sites in the boreonemoral zone of southern Sweden. Species richness and composition were analysed in relation to environmental variables at a local and at larger scales (multiple regression), and compared to results from similar studies in spruce-dominated sites in the boreal zone of Norway (PCA and two-sample t tests). Regressions showing a dominance of regional factors over local in-site variables agree with species-richness models assuming that local communities most often are unsaturated. Precipitation (inter-correlated with elevation) was the strongest factor for explaining the variation in species-richness, which is consistent with previous results indicating that mycetophilids are disfavoured by drought. In addition to precipitation, the area of mixed forest with high biodiversity values (woodland key habitats and protected areas) was a positive factor for species-richness, probably because such habitats combine elements of both coniferous and deciduous forests. PCA ordination revealed a clear separation of the species composition between boreal and boreonemoral forests. Species-richness in boreal forest was significantly higher than in boreonemoral forest, indicating a preference for boreal habitats in many of the species. For mycetophilids and other drought-sensitive insects, it is suggested that (partial) cutting in some dense successional oak stands should be avoided, and that some invading spruces should be tolerated.     

农业生态环境恢复重建的模式与对策--以陕北吴旗县为例

在分析吴旗县农业生态环境概况和退耕还林还草下生态经济系统演变特征的基础上,提出吴旗应根据其区位特征,构建4种类型的系统循环链网为主的生态农业模式,以调整优化产业结构,改善农田生态环境建设。并进一步提出了农业生态环境恢复和重建的对策。     

Fluctuations of carabid populations inhabiting an ancient woodland (Coleoptera, Carabidae)

The changes in population size of carabid beetles inhabiting an ancient woodland were analysed in a long-term investigation covering a period of nine years (1994–2002). The amplitude of fluctuations of the relative density of these species was estimated and compared with those of carabid beetles inhabiting recent woodlands and more unstable habitats in open landscapes. To analyse this, 8 pitfall traps were set in an ancient beech and oak woodland in the nature reserve “Lüneburger Heide” in northern Germany and were emptied every fortnight the whole year round.Catching rates for some species (e.g. Carabus problematicus and Abax parallelepipedus) fluctuated only slightly, whereas those of other species (e.g. C. violaceus and C. auronitens) varied as much as ten-fold. Comparison of these results with those of other long-term investigations of recent woodlands and also of more open habitats showed that in each of the three habitat types some species varied very little in abundance and others, very widely. So it seems that the amplitude of fluctuations in abundance is a feature of each single species rather than a special attribute of their habitats.     

Species presence in fragmented landscapes: modelling of species requirements at the national level

The fragmentation of ancient woodland has been identified as a cause of decline in biodiversity in the UK. Current policy advocates the targeting of resources to mitigate its effects. In this study a number of patch and landscape scale measures of ancient woodland distribution were derived from national data sets. These measures were translated into independent variables representing patterns of woodland cover using principal component analysis (PCA). Key species were selected according to differing sensitivities to fragmentation of ancient woodland. Logistic regression models of species distributions were constructed.A range of bird and mammal distributions were found to be correlated to landscape scale measures of fragment distribution, in contrast to butterfly and plant species, which exhibited a stronger correlation to patch-scale measures. The national distribution of a range of woodland species is predicted. New information is presented on the landscape requirements of woodland species, particularly those that enable them to persist in fragmented woodland landscapes. The different scales at which species show a sensitivity to fragment distribution are discussed. The results confirm the association between species and different aspects of the structure of the wooded landscape, and provide information of value in targeting national conservation expenditure in England.