Modelling biome shifts and tree cover change for 2050 in West Africa

Aim Africa is expected to face severe changes in climatic conditions. Our objectives are: (1) to model trends and the extent of future biome shifts that may occur by 2050, (2) to model a trend in tree cover change, while accounting for human impact, and (3) to evaluate uncertainty in future climate projections. Location West Africa. Methods We modelled the potential future spatial distribution of desert, grassland, savanna, deciduous and evergreen forest in West Africa using six bioclimatic models. Future tree cover change was analysed with generalized additive models (GAMs). We used climate data from 17 general circulation models (GCMs) and included human population density and fire intensity to model tree cover. Consensus projections were derived via weighted averages to: (1) reduce inter‐model variability, and (2) describe trends extracted from different GCM projections. Results The strongest predicted effect of climate change was on desert and grasslands, where the bioclimatic envelope of grassland is projected to expand into the desert by an area of 2 million km². While savannas are predicted to contract in the south (by 54 ± 22 × 10⁴ km²), deciduous and evergreen forest biomes are expected to expand (64 ± 13 × 10⁴ km² and 77 ± 26 × 10⁴ km²). However, uncertainty due to different GCMs was particularly high for the grassland and the evergreen biome shift. Increasing tree cover (1–10%) was projected for large parts of Benin, Burkina Faso, Côte d’Ivoire, Ghana and Togo, but a decrease was projected for coastal areas (1–20%). Furthermore, human impact negatively affected tree cover and partly changed the direction of the projected change from increase to decrease. Main conclusions Considering climate change alone, the model results of potential vegetation (biomes) show a ‘greening’ trend by 2050. However, the modelled effects of human impact suggest future forest degradation. Thus, it is essential to consider both climate change and human impact in order to generate realistic future tree cover projections.     

Single point mutation on the gene encoding dysbindin results in recognition deficits

The dystrobrevin‐binding protein 1 (DTNBP1) gene is a candidate risk factor for schizophrenia and has been associated with cognitive ability in both patient populations and healthy controls. DTNBP1 encodes dysbindin protein, which is localized to synaptic sites and is reduced in the prefrontal cortex and hippocampus of patients with schizophrenia, indicating a potential role in schizophrenia etiology. Most studies of dysbindin function have focused on the sandy (sdy) mice that lack dysbindin protein and have a wide range of abnormalities. In this study, we examined dysbindin salt and pepper (spp) mice that possess a single point mutation on the Dtnbp1 gene predicted to reduce, but not eliminate, dysbindin expression. By western blot analysis, we found that spp homozygous (spp ?/?) mutants had reduced dysbindin and synaptosomal‐associated protein 25 (SNAP‐25) in the prefrontal cortex, but unaltered levels in hippocampus. Behaviorally, spp mutants performed comparably to controls on a wide range of tasks assessing locomotion, anxiety, spatial recognition and working memory. However, spp ?/? mice had selective deficits in tasks measuring novel object recognition and social novelty recognition. Our results indicate that reduced dysbindin and SNAP‐25 protein in the prefrontal cortex of spp ?/? is associated with selective impairments in recognition processing. These spp mice may prove useful as a novel mouse model to study cognitive deficits linked to dysbindin alterations. Our findings also suggest that aspects of recognition memory may be specifically influenced by DTNBP1 single nucleotide polymorphisms or risk haplotypes in humans and this connection should be further investigated.     

Locomotor activity rhythm of Talitrus saltator (Crustacea,Amphipoda) on a progradating sandy beach

In the Maremma Natural Park (Grosseto, Italy), the Collelungo beach exhibits a clear morphodynamics gradient, resulting in a severe erosion to a gradual accretion along the shoreline. Here, three sub-populations of the sandhopper Talitrus saltator (Montagu) (Crustacea, Amphipoda) were studied to highlight eventual intra- and inter-population variation of the endogenous locomotor rhythm. Individual activity recordings were carried out for 21 days in constant darkness and controlled temperature and humidity conditions. The variation of the free-running period was analysed at individual and sub-population levels, and the dependence on intrinsic (individual features) and extrinsic (habitat of origin and season) factors was analysed. A seasonal variation was highlighted, related to the seasonal spontaneous activity of the species. In summer and autumn, a significant correlation between the behavioural variation in the sub-populations (period and definition of the period) and beach physical parameters (slope and width) defined the dependence of the behavioural gradient on the environmental gradient. The observed relationship may represent an adaptation to the local coastline dynamics, suggesting the importance of a plastic behaviour as adaptive response to a variable environment.     

Patchwork, Pastoralists, and Perception: Dune Sand as a Valued Resource Among Herders of Inner Mongolia

Scholars have rarely reflected upon dune sand in any context other than that of environmental hazard. Yet recent anthropological research conducted among ethnic Mongol herders in the Keerqin Sandy Lands of Northeast China indicates that native inhabitants exhibit a surprising degree of tolerance, appreciation, and even preference for dune sand at specific spatio-temporal scales. Survey data, gathered primarily through the use of photographic prompts and pile sort exercises during household interviews, reveal that many residents even regard dune sand as the constituent element of a distinctive home environment and cherished way of life. This research underscores the relevance of perception to the policies and practices of human resource management. It also calls into question the authority with which officials and scholars in China and elsewhere indiscriminantly depreciate the various social utilities of dune sand in stock-herding populations.     

氮添加对沙质草地微生物呼吸与根系呼吸的影响

土壤呼吸可以细化为根系呼吸和微生物呼吸,二者对氮添加的响应有所不同.本文以科尔沁沙质草地为研究对象,探讨氮添加对土壤CO₂排放的影响,并细化为微生物呼吸和根系呼吸的响应特征.结果表明: 在观测期(5—10月),土壤呼吸、微生物呼吸月动态均呈先升高后降低的趋势;微生物呼吸是土壤呼吸的主要贡献者,占82.6%;观测期内根系呼吸贡献率随月份而变化,根系呼吸贡献率两个峰值分别出现在5月(占49.4%)和8月(占41.9%),6个月的平均贡献率为17.4%;在10 ℃条件下,根系呼吸较微生物呼吸对氮添加的响应更为敏感,微生物呼吸速率在氮添加后降低了3.9%,而根系呼吸降低了17.7%;氮添加提高了土壤呼吸、微生物呼吸温度敏感性Q₁₀值,也提高了二者对土壤水分变化的敏感程度.     

Deep placement of Mn fertiliser on a sandy soil increased grain yield and reduced split seed in Lupinus angustifolius

Experiments were conducted over two years with Lupinus angustifolius L. on a site with acid sandy soil near Esperance, Western Australia to determine if deep placed manganese fertilizer increases lupin grain yield. Manganese at 4 and 8 kg ha⁻¹ was placed below the surface immediately before sowing at 4, 20 and 30 cm and 4, 8, 12, 16 and 20 cm in 1987 and 1988 respectively. Foliar Mn applied at 1 kg ha⁻¹ when the first order laterals were in mid-flowering stage, was also compared. Increasing the depth of Mn placement increased grain yield in both years. The deepest placed Mn increased grain yields by 255 kg ha⁻¹ (10%) and 430 kg ha⁻¹ (106%) in year 1 and year 2 over the shallow (4 cm) placed Mn. The higher responses to deep placed Mn occurred in year 2, the year with the driest spring and most intense aphid infestations. Foliar applied Mn was as effective as most deep placed Mn treatments, except for the highest rate (8 kg ha⁻¹) at the greatest depth (20 cm) in year 2. The higher rate of applied Mn gave the best grain yields. This revised version was published online in June 2006 with corrections to the Cover Date.     

不同抚育措施对闽西毛竹林碳密度、碳贮量与碳格局的影响

以闽西永安市Ⅰ（挖笋+劈草+施肥+灌水)、Ⅱ(挖笋+劈草+施肥)、Ⅲ（挖笋+劈草)3种不同抚育措施的毛竹林为对象,对其碳密度、碳贮量及碳格局进行了研究。结果表明：毛竹各器官碳密度变动范围为0.3947～0.5619 g·g^-1,碳密度高低排序为竹鞭＞竹秆＞竹枝＞竹蔸＞竹叶＞竹根＞鞭根;不同竹龄间竹秆、竹枝、竹叶、竹根碳密度存在极显著差异（P<0.01）,而竹蔸碳密度差异不显著（P＞0.1）;随着竹龄增加,毛竹平均碳密度有下降趋势,1～6年毛竹平均碳密度为0.4579～0.4957 g·g^-1。Ⅰ、Ⅱ和Ⅲ类毛竹林毛竹层碳贮量分别为76.74、64.30和55.91 t·hm^-2;凋落物层碳贮量分别为2.59、3.01和4.88 t·hm^-2;土壤层碳贮量分别为150.64、197.36和232.56 t·hm^-2;总碳贮量分别为227.37、261.66和288.47 t·hm^-2,其中土壤层碳贮量所占比例最高,分别为66.25%、75.43%和80.62%,毛竹层碳贮量比例分别为32.61%、23.43%和17.69%,凋落物层碳贮量比例分别为1.14%、1.15%和1.69%。毛竹生物器官中,竹秆固碳能力最强,占年总固碳量比例为56.47%～59.66%,鞭根的固碳能力最弱,占年总固碳量的比例仅为2.52%～2.83%;毛竹林年固碳量排序为Ⅰ类型＞Ⅱ类型＞Ⅲ类型。     

Sheep Grazing Decreases Organic Carbon and Nitrogen Pools in the Patagonian Steppe: Combination of Direct and Indirect Effects

We explored the net effects of grazing on soil C and N pools in a Patagonian shrub–grass steppe (temperate South America). Net effects result from the combination of direct impacts of grazing on biogeochemical characteristics of microsites with indirect effects on relative cover of vegetated and unvegetated microsites. Within five independent areas, we sampled surface soils in sites subjected to three grazing intensities: (1) ungrazed sites inside grazing exclosures, (2) moderately grazed sites adjacent to them, and (3) intensely grazed sites within the same paddock. Grazing significantly reduced soil C and N pools, although this pattern was clearest in intensely grazed sites. This net effect was due to the combination of a direct reduction of soil N content in bare soil patches, and indirect effects mediated by the increase of the cover of bare soil microsites, with lower C and N content than either grass or shrub microsites. This increase in bare soil cover was accompanied by a reduction in cover of preferred grass species and standing dead material. Finally, stable isotope signatures varied significantly among grazed and ungrazed sites, with δ¹⁵N and δ¹³C significantly depleted in intensely grazed sites, suggesting reduced mineralization with increased grazing intensity. In the Patagonian steppe, grazing appears to exert a negative effect on soil C and N cycles; sound management practices must incorporate the importance of species shifts within life form, and the critical role of standing dead material in maintaining soil C and N stocks and biogeochemical processes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author Contributions  RAG designed study, performed research, analyzed data, wrote the paper; ATA designed study, wrote the paper; CGGM designed study, performed research, analyzed data; MGP performed research; OES designed study; RBJ designed study, contributed new methods.