Riparian plant composition in an urbanizing landscape in southern California,U.S.A.

In coastal southern California, natural riparian corridors occur in a landscape mosaic comprised of human land uses (mainly urban and suburban development) interspersed among undeveloped areas, primarily native shrublands. We asked, does the composition of the landscape surrounding a riparian survey point influence plant species distribution, community composition, or habitat structure? We expected, for example, that invasive non-native species might be more abundant as the amount of surrounding urbanization increased. We surveyed 137 points in riparian vegetation in Orange County, California, along an urbanization gradient. Using logistic regression we analyzed 79 individual plant species’ distributions, finding 20 negatively associated and 12 positively associated with the amount of development within a 1-km radius around the survey points, even after accounting for the effects of elevation. However, after summarizing plant community composition with Detrended Correspondence Analysis we observed that, overall, community composition was not statistically correlated with the amount of development surrounding a survey point once the association between development and elevation was taken into account. Non-native species were not particularly associated with increasing development, but instead were distributed throughout vegetation and urbanization gradients. However, the extent of the tree and herb layers (structural attributes) was associated with development, with the tree layer increasing and the herb layer decreasing as urbanization increased. Thus, although the degree of surrounding urbanization appears to influence the distribution of a number of individual plant species, overall composition of the community in our study system seemed relatively unaffected. Instead, we suggest that community composition reflected larger-scale environmental conditions, such as stream order and other variables associated with elevation, and/or regional-scale disturbances, such as historic grazing or enhanced atmospheric deposition of nitrogen.     

Post Hoc Assessment of Stand Structure Across European Wood-Pastures: Implications for Land Use Policy

Europe’s woodland and savanna rangelands, often part of silvopastoral systems known as wood-pastures, are deteriorating because of abandonment that leads to return to a forested state or lack of tree regeneration from overgrazing or tree and shrub removal. Despite numerous local studies, there has been no broader survey of the stand structure of European wood-pastures showing which systems are at risk of losing their semiopen character. This overview aims to 1) show some of the differences and similarities in wood-pastures from landscapes across Europe and 2) identify which of these wood-pastures are at risk of losing their semiopen character. We collated a dataset of 13 693 trees from 390 plots in wood-pastures from eight different European regions (western Estonia, eastern Greece, northern Germany, Hungary, northern Italy, southern Portugal, central Romania, and southern Sweden), including tree diameters at breast height, tree density, management type, and tree species composition. On the basis of their structural characteristics, we classified wood-pastures using principal component analysis (PCA) and cluster analysis. The PCA showed a gradient from dense wood-pastures with high levels of regeneration (e.g., in Estonia) to sparse wood-pastures with large trees but a lack of regeneration (e.g., in Romania). Along this gradient, we identified three main groups of wood-pastures: 1) sparse wood-pastures with mostly big trees; 2) dense wood-pastures composed of small trees, and 3) wood-pastures containing a wide range of tree ages. Our results show a large structural gradient in European wood-pastures, as well as regeneration problems varying in their severity, highlighting the importance of social-ecological context for wood-pasture conditions. To maintain the ecological and cultural integrity of European wood-pastures, we suggest 1) more comprehensively considering them in European policies such as the Common Agricultural Policy and EU Habitats Directive, while 2) taking into account their structural characteristics and social-ecological backgrounds.     

Deciduous woodland exposed to elevated atmospheric CO2 has species-specific impacts on anecic earthworms

Elevated atmospheric CO₂ induced reductions in litter quality can adversely affect earthworms. However, this understanding is based on laboratory rather than field research and relates to single earthworm and tree species. Here earthworm populations were investigated under Alnus glutinosa, Betula pendula, and Fagus sylvatica in a Free Air Carbon dioxide Enrichment field experiment. Litters from this experiment were also fed to Lumbricus terrestris L. at two rates with live weight change and cast properties assessed. Elevated CO₂ (580 ppmv) reduced litter N (−12%) with a corresponding increase in C:N ratio, especially for A. glutinosa. In the field, elevated CO₂ caused a shift in overall population composition, mainly characterised by reduced anecic biomass (–25%); endogeic and epigeic species were less affected. CO₂ effects on total biomass were most pronounced for A. glutinosa (e.g. field total biomass −47% vs. −11% overall). Growth of L. terrestris was lower when fed elevated CO₂ litter (−18%), although increased inputs of A. glutinosa litter mitigated this effect. In mesocosms, fresh cast respiration was lower (−14%) for elevated CO₂ litter, an effect more pronounced for A. glutinosa (−24%). When normalised for C content, elevated CO₂ effects on cast respiration were again negative and most marked for A. glutinosa litter. Litter N concentration, and possibly ease of litter mineralisation were factors affecting litter resource quality Litter N and P concentrations varied with A. glutinosa > B. pendula > F. sylvatica; F. sylvatica had the highest cellulose content. Field earthworm biomass was higher under A. glutinosa compared with B. pendula and F. sylvatica (+17 and +70%, respectively); live weight increased with A. glutinosa litter in the feeding trial almost three times more than for B. pendula, whereas it decreased for F. sylvatica. Cast respiration was highest for A. glutinosa, intermediate for B. pendula (ca. −36%) and lowest for F. sylvatica (ca. −78%). Earthworm responses to elevated CO₂ were complex, being characteristic of individual tree and earthworm species; responses were more adverse for trees with higher quality litter and for anecic earthworms.     

黄土高原天然山杨林地产流产沙研究

研究了天然山杨林地的产流产沙,结果表明:与采伐林木辟为农地比较,天然山杨林和采伐林木保护草灌层林地径流高度各降低62.5% 和51.1%;产流总时间各滞后90和10min;混水量各降低92.8% 和92.9%,含沙量降低99.1% 和99.2%;侵蚀模数降低99.9% 和99.9%;前者径流曲线陡峭、起伏程度大,后者平缓、起伏程度小。     

内蒙古自治区多伦县不同林地枯落物持水性能研究

[目的]探讨多伦县不同林分类型的枯落物持水性能差异,为该区森林土壤持水性能提供基础数据理论。[方法]以内蒙古自治区锡林浩特市多伦县为研究区,选取代表性的10块林地,收集林地地表枯落物,测定其现存量、持水性能及拦蓄能力等,旨在分析不同林分类型下枯落物持水性能的差异及其对表层土壤(0—20cm)含水率的影响。[结果](1)乔木林的枯落物现存量、持水能力和拦蓄能力均高于灌木林。(2)天然林的枯落物现存量、持水能力和拦蓄能力均高于人工林。(3)各林地枯落物厚度显著影响表层土壤的含水率,即枯落层越厚,表层土壤含水率越高。[结论]由于树种组成、年龄、林分密度及立地条件的影响,不同林分类型的持水能力差异较大,但变化规律为基本一致,同时,林地对土壤水分的影响高于草地。     

内蒙古大兴安岭林区发展非公有制林业探讨

发展非公有制林业对我国生态建设、林业产业发展具有重要意义.针对内蒙古大兴安岭林区的现实,提出国有林区发展非公有制林业必须解放思想、科学规划,遵守国家法律,建立相应的服务体系,遵守相关原则.     

The Function of Plant Patches and Woodland Ecosystem in Utilized and Un-Utilized Sites (Case Study: Forest Region of Aloostan,Golestan Province)

Functional and structural features of plant patches in different ecological sites are used as ecological threshold predictors in natural ecosystems. This study aimed to: (i) find the effect of types of plant patches (based on live form) on potential and function of woodland ecosystems and (ii) compare plant patches function in utilized and un-utilized sites on the south slope of Alborz Mountain, Golestan Province. For this purpose, eleven parameters of the soil surface attributes of each plant patches were assessed using the Landscape Function Analysis methodology across four transects of 100 meters located at the highest slope. Then stability, nutrient cycle, and infiltration indicators of each plant patches were calculated using Excel software. These indicators were tested between two sites and within the plant patch groups using Student t-test and Duncan comparison of means analysis, respectively, by SPSS (Statistical Package for the Social Sciences) software. The study did not find a significant difference between the two sites and the plant patches, except for the stability indicator between the sites. Also, results showed different functions within the groups of the sites, especially in the woody plant patches with the highest function in all the indicators in both sites. Woody and woody-grass were the most important ecological indicators at utilized and un-utilized sites. The results of this study suggest that the use of Landscape Function Analysis provides a simple, rapid and consistent method in assessment of the forest ecosystems health.     

陆良县林地功能分区保护利用措施探讨

根据陆良县森林资源现状以及生态建设和林业产业发展布局,将陆良县林地划分为4个功能区,阐述各功能区范围及特点,提出各功能区的保护利用措施。     

新疆甘家湖梭梭林林地土壤养分、盐分的累积特征

以新疆甘家湖梭梭林自然保护区植被盖度C≥70％（ HC）、50％≤C＜70％（ MC）、30％≤C＜50％（ LC）和无林地（ NL）4种林地类型土壤为研究对象,分析测定了土壤养分和盐分在0～100 cm空间上的分布特征。结果显示：4种盖度林地土壤有机质质量分数均不高,仅有2．70～6．90 g· kg-1。土壤中全效氮、磷和速效氮、磷、钾质量分数与有机质质量分数呈极显著正相关（ P＜0．001）,且全氮、全磷质量分数与有机质质量分数的比值相近（0．0330、0．0332）。 HC、MC、LC和NL林地土壤的速效磷和速效钾表聚现象明显,其中,土层深（H）0＜H≤20 cm中速效磷质量分数分别占其他土壤剖面的28．2％、40．5％、40．5％和33．2％,速效钾分别占41．8％、30．1％、34．2％和40．6％。4种类型梭梭林林地土壤剖面pH值均大于8．00,0＜H≤10 cm和60 cm＜H≤100 cm土层中总盐的质量分数较大。土壤中阴离子以Cl-和SO2-4为主,阳离子主要为Na＋和Ca2＋。综上所述,有林地土壤质量比裸地好,主要表现为有林地的有机质及速效养分质量分数较大,土壤盐度低。     

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.