Modelling forest management within a global vegetation model—Part 1: Model structure and general behaviour

This article describes a new forest management module (FMM) that explicitly simulates forest stand growth and management within a process-based global vegetation model (GVM) called ORCHIDEE. The net primary productivity simulated by ORCHIDEE is used as an input to the FMM. The FMM then calculates stand and management characteristics such as stand density, tree size distribution, tree growth, the timing and intensity of thinnings and clear-cuts, wood extraction and litter generated after thinning. Some of these variables are then fed back to ORCHIDEE. These computations are made possible with a distribution-based modelling of individual tree size. The model derives natural mortality from the relative density index (rdi), a competition index based on tree size and stand density. Based on the common forestry management principle of avoiding natural mortality, a set of rules is defined to calculate the recurrent intensity and frequency of forestry operations during the stand lifetime. The new-coupled model is called ORCHIDEE-FM (forest management).The general behaviour of ORCHIDEE-FM is analysed for a broadleaf forest in north-eastern France. Flux simulation throughout a forest rotation compare well with the literature values, both in absolute values and dynamics.Results from ORCHIDEE-FM highlight the impact of forest management on ecosystem C-cycling, both in terms of carbon fluxes and stocks. In particular, the average net ecosystem productivity (NEP) of 225 gC m⁻² year⁻¹ is close to the biome average of 311 gC m⁻² year⁻¹. The NEP of the “unmanaged” case is 40% lower, leading us to conclude that management explains 40% of the cumulated carbon sink over 150 years. A sensitivity analysis reveals 4 major avenues for improvement: a better determination of initial conditions, an improved allocation scheme to explain age-related decline in productivity, and an increased specificity of both the self-thinning curve and the biomass-diameter allometry.     

Habitat Split as a Cause of Local Population Declines of Amphibians with Aquatic Larvae

Abstract:  Most amphibian species have biphasic life histories and undergo an ontogenetic shift from aquatic to terrestrial habitats. In deforested landscapes, streams and forest fragments are frequently disjunct, jeopardizing the life cycle of forest-associated amphibians with aquatic larvae. We tested the impact of habitat split—defined as human-induced disconnection between habitats used by different life-history stages of a species—on four forest-associated amphibian species in a severely fragmented landscape of the Brazilian Atlantic Forest. We surveyed amphibians in forest fragments with and without streams (referred to as wet and dry fragments, respectively), including the adjacent grass-field matrix. Our comparison of capture rates in dry fragments and nearby streams in the matrix allowed us to evaluate the number of individuals that engaged in high-risk migrations through nonforested habitats. Adult amphibians moved from dry fragments to matrix streams at the beginning of the rainy season, reproduced, and returned at the end of the breeding period. Juveniles of the year moved to dry fragments along with adults. These risky reproductive migrations through nonforested habitats that expose individuals to dehydration, predation, and other hazards may cause population declines in dry fragments. Indeed, capture rates were significantly lower in dry fragments compared with wet fragments. Declining amphibians would strongly benefit from investments in the conservation and restoration of riparian vegetation and corridors linking breeding and nonbreeding areas.     

滨海盐田建设对周边土壤及植被的影响

随着滨海盐业的迅猛发展,盐田的急剧扩张已经对周边环境产生了影响。通过调查盐田周边植被分布特征,分析与植被带对应的典型样地土壤理化性质的空间异质性,研究了盐田对周边土壤及植被的影响。结果表明：盐田周边的植被分布存在明显的空间异质性,在盐田周边呈带状分布,且距盐田越近,植被盖度、物种丰富度越低。土壤含盐量的空间分布在宏观上表现为距盐田越近,含盐量越高,土壤盐渍化越重。距离盐田20m处土壤含盐量平均值达8.22g·kg-1,距离盐田1000m处,土壤含盐量平均值为1.84g·kg-1,土壤含盐量显著降低,且表层土壤含盐量与采样地距盐田间的距离之间呈显著相关关系。由此可见,盐田的扩建已经显著加重了周边土壤的盐渍化程度。     

密云水库流域植被覆盖度变化对输沙量的影响

封闭流域中,泥沙的产生是多种因素相互作用,相互制约的结果,而在这些众多的环境影响因素中,植被是土壤侵蚀中最重要的环境控制因子,目前,植被覆盖度变化对输沙量的影响一直是区域生态环境研究中比较热门的话题。文章使用遥感（Remote Sensing（RS））、地理信息系统（Geographic In formmionSystem（GIS））与统计分析相结合的方法评价了密云水库流域内2个子流域出口处2002年至2005年植被覆盖度变化对输沙量的影响。密云水库流域多为山地,其降雨具有明显的季节性。本文的主要目的在于分析2002年至2005年植被覆盖度变化对流域输沙量的影响,并分析了植被覆盖度变化对气候改变及人类活动的综合影响,结果表明：在密云水库流域内,输沙量是降雨情况和人为因素引起的地表植被覆盖度变化情况的综合反映,人口增长、经济发展和城市化是密云水库流域内引起土地利用变化和地表植被覆盖度变化的主要驱动力。并且,输沙量可以被看作是一个很好的指标来定量分离出生物生理和人为的影响,并从中能够找出在流域生态系统中获得显著结果关键的临界点。研究结果对制定流域的合理开发和管理计划将有所帮助。     

基于地理探测器的区域植被覆盖度的定量影响——以京津风沙源区为例

植被覆盖度（FVC）是衡量生态环境优秀的重要指标.本文基于MODIS NDVI数据,运用像元二分法模型,估算了2000~2018年京津风沙源区FVC,分析了其时空变化特征.在此基础上,基于地理探测器模型,定量分析了自然因素和人类活动因素等12个因子对京津风沙源区FVC空间分布的影响.结果表明,近20a来京津风沙源区FVC整体上呈增加趋势,增加率为8.2%.空间上,研究区73.7%的区域FVC在增加,其中显著增加的区域主要集中在晋北山地丘陵亚区、燕山丘陵山地水源保护亚区、大兴安岭南部亚区和科尔沁沙地亚区的南部.2000~2018年,降水是影响京津风沙源区FVC空间分布的主要自然因子,解释力为63.3%;年末大牲畜头数是影响FVC空间分布的主要人为因子,解释力为34.8%.自然因素和人类活动之间的双因子交互作用以双协同作用和非线性协同作用为主,表明相对于单因子,自然因素和人类活动间的交互作用对FVC的解释力更强.其中,降水与其他11个因子的交互作用对研究区FVC起主导作用,解释力超过60%.     

改性植被混凝土基材力学与植生试验研究

为探明羧甲基纤维素钠(CMC)与麦秸秆纤维对植被混凝土基材力学与植生性能的影响,通过直剪试验、植生试验研究了改性后植被混凝土基材(简称改性基材)的抗剪性能与黑麦草生长性能.结果 表明:①改性基材的剪切强度随CMC掺量的增加呈先增后减的变化趋势,0.5％CMC掺量时基材的剪切强度出现峰值,而随纤维掺量的增加改性基材剪切强...     

Uneven distribution of urban green spaces in a coastal city in northwest Mexico

ABSTRACT

Extent and distribution of urban green spaces (UGS) in Mazatlan (Mexico) are analysed using remote sensing and GIS techniques. Vegetated areas (2,270?ha), a third of the urban area in 2015, were reclassified into green spaces (GS), urban tree (UT) and open spaces (OS), based in the normalised difference vegetation index, relating them with demographic and socioeconomic data. UGS allocation per capita amount 55?m², mainly represented by the UT class, with the largest patches associated with low developed and very high marginalised areas, and also with very low marginalised sectors, while the lowest allocation correspond to medium and low marginalisation, highly populated sector, without significant correlations. Despite the USG allocation, it is required a better urban planning to maintain public UGS and to protect the local flora, threatened by the introduction of exotic, ornamental species (64% of UT), to guarantee the provision of ecosystem services to the population.     

Natural recovery of different areas of a deserted quarry in South China

A quarry is a surface mining operated place, which produces enormous quantities of gravel, limestone, and other materials for industrial and construction applications. Restoration and revegetation of deserted quarries are becoming increasingly important. Three areas of a typical quarry in South China: terrace for crushed materials (terrace), spoiled mound, and remaining side slope, were investigated, to compare the existing plant species and to study the relationship between environmental factors and revegetation. The plant species composition of these three areas was found to differ significantly after eight years of natural recovery. The typical plant communities found over them were composed of gramineous herbs, fems, and shrubs. Soil organic matter, soil moisture, and soil bulk density were considered to be the major determining factors for vegetation succession. There existed abiotic and biotic thresholds during quarrying restoration. Suggestions had been presented that could have accelerated the process of natural recovery in quarries.     

Spectral characteristics of plant communities from salt marshes:A case study from Chongming Dongtan,Yangtzeestuary,China

The spectral reflectance of recently formed salt marshes at the mouth of the Yangtze River, which are undergoing invasion by Spartina alterniflora, were assessed to determine the potential utility of remotely sensed data in assessing future invasion and changes in species composition. Following a review of published research on remote sensing of salt marshes, 53 locations along three transects were sampled for paired data on plant species composition and spectral reflectance using a FieldSpec™ Pro JR Field Portable Spectroradiometer. Spectral data were processed concerning reflectance, and the averaged reflectance values for each sample were reanalysed to correspond to a 12-waveband bandset of the Compact Airborne Spectral Imager. The spectral data were summarised using principal components analysis (PCA) and the relationships between the vegetation composition, and the PCA axes of spectral data were examined. The first PCA axis of the reflectance data showed a strong correlation with variability in near infrared reflectance and ‘brightness’, while the second axis was correlated with visible reflectance and ‘greenness’. Total vegetation cover, vegetation height, and mudflat cover were all significantly related to the first axis. The implications of this in terms of the ability of remote sensing to distinguish the various salt marsh species and in particular the invasive species S. alterniflora were discussed. Major differences in species with various physiognomies could be recognised but problems occurred in separating early colonising S. alterniflora from other species at that stage. Further work using multi-seasonal hyperspectral data might assist in solving these problems.     

林(竹)草不同植被恢复模式下的土壤物理特性

利用建立生态定位观测场,对华西雨屏区洪雅县低山区退耕还林中的桦木+扁穗牛鞭草、苦竹+扁穗牛鞭草、纯扁穗牛鞭草和撑绿杂交竹＋扁穗牛鞭草4种林（竹）草植被类型进行定位观测,研究不同植被恢复类型对土壤物理特性的改良。试验结果表明：林（竹）草不同植被类型植被恢复5年后,土壤0～40 cm土层的砂粒和粗粉粒百分含量均有一定的下降,在一定程度上逆转了原坡耕地土壤继续“粗化”的趋势;4种植被恢复类型土壤0～40 cm土层的物理性粘粒含量与农耕地相比均有一定提高,在一定程度上增强了固持土壤养分的能力,以苦竹＋扁穗牛鞭草改良效果最好;与农耕地相比,4种植被恢复类型土壤0～40 cm土层土壤容重有增有减,以苦竹＋扁穗牛鞭草和撑绿杂交竹＋扁穗牛鞭草植被恢复类型改良效果相对较优;虽然除纯牛鞭草地外其它3种植被恢复类型土壤0～40 cm的总孔隙度与农耕地相比都有一定程度的增加,但土壤总孔隙度都偏小,非毛管孔隙/毛管孔隙值也不合理。可见土壤结构的改良并非退耕后植被恢复短期内就能实现的,还需长时间的植被保护、合理的经营。〖