浅谈沙地种草

本文从奈曼旗的草地现状出发 ,从干旱缺水、风沙袭击、低温灾害 3个方面论述了影响沙地种草的主要因素 ,针对这些不利因素 ,提出了补播。

六种蒿属沙生半灌木染色体核型分析

采用常规细胞遗传学方法和Motic-BA200数码显微摄影系统、Karyo3.1染色体分析软件,对分布于我国北方的蒿属6种沙生半灌木进行了染色体数目及核型分析.结果表明:差不嘎蒿A.halodendron、褐沙蒿A.intramongolica、黑沙蒿A.ordosica、准噶尔沙蒿A.songarica的染色体数目为36条,核型公式为2n=4x=36m;白沙蒿A.sphaerocephala和乌丹蒿A.wudanica的染色体数目为18条,核型公式为2n=2x=18m;6种蒿属植物的核型均属于1A.除黑沙蒿、准噶尔沙蒿外,其他4种植物的染色体数目及倍性与已报道的结果相同.

Concentrations of foliar and surface soil in nutrients Pinus spp. plantations in relation to species and stand age in Zhanggutai sandy land, northeast China

The concentrations of the foliar and surface soil nutrients and the variation with species and stand age were studied inPinus spp. plantations in Zhanggutai area, northeast China. The results showed that the total N, total P and C: N ratio of the soil inP. sylvestris var.mongolica stands were significantly higher in comparison with those inP. tabulaeformis andP. densiflora stands. ForP. sylvestris var.mongolica, the foliar P concentration appeared to decrease with age, and the foliar N and K concentrations did not show a consistent change with age. As for the different tree species of the similar age, the foliar N and P concentrations were significantly different (p<0.05), being withP. sylvestris var.mongolica>P. densiflora>P. tabulaeformis. The foliar N: P ratio ofP. densiflora significantly was higher thanP. sylvestris var.mongolica andP. tabulaeformis, while the foliar K was no obvious difference between the three tree species. There were significant correlation (p<0.05) between soil total N and P, soil organic matter and total P, foliar N and P, but it did not show significant correlations between soil and foliar nutrient concentrations, which might attribute to the excessive litter raking, overgrazing and low soil moisture in this area. Based on the foliar N: P ratio, we introduced a combination threshold index of N: P ratio with their absolute foliar nutrient concentrations to determine the possible limiting nutrient. According to the critical N: P ratio and their absolute foliar N, P concentrations, theP. sylvestris var.mongolica stands showed a decreased N limitation degree with age, theP. densiflora stands showed unlimited by N and P in the whole, and theP. tabulaeformis stands showed co-limited by N and P. No significant difference in soil nutrient concentrations of the surface soils was found between 45, 29, 20-yr-oldPinus sylvestris var.mongolica plantation stands. Keywords coniferous trees - foliar nutrient concentration - limiting nutrients - N - P ratio - Zhanggutai sandy land CLC number S718.55 Document code A Article ID 1007-662X(2004)01-0011-08 Foundation item: This research was supported by Key Knowledge Innovation Project (KZCX3-SW-418) of Chinese Academy of Sciences.Biography: CHEN Guang-sheng (1978-), male, master candidate in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. ChinaResponsible editor: Song Funan

Comparing the model forms estimating generalised diameter-height re-lationships in Tecomella undulata plantations in hot arid region of India

Four generalised diameter-height equations were developed and compared for pure and even-aged stands of Tecomella undulata in hot arid region of Rajasthan State in India. The data used to fit the equations consisted of 1 540 diameter-height observations collected from the plots laid out in uniformly stocked stands of varying age and density. The performance of four equations was tested by non-linear least squares regression and evaluated using different statistical criteria. Finally, these equations, with the same values of coefficients ob- tained during the fitting phase, were validated by an independent data set consisting of 854 diameter-height observations. Overall, equation （4） （Hui and Gadow function） was found to perform best for both the fitting data set as well as validation data set.

Availability and Use of Willow Species in Representative Cold Desert Areas of Northwestern Himalaya,India

Willow species （Salix fragilis L. and S. alba L.） are important elements of cold desert agroforestry systems in the Lahaul valley, north- western Himalaya. Their ability to grow through shoot-cuttings plantations under extreme and xeric climatic conditions of cold deserts, makes them ecologically suited and socially accepted for forestry programmes. Willow species in cold deserts may combat desertification and can thrive well in these areas as compared to any other species. Salixfragilis L. and S. alba L. are under cultivation in the Lahaul valley. However, S. fragilis is widely cultivated under the agroforestry and plantation forestry systems. In the Lahaul valley, willow species are used as subsistence resources and for socio-religious purposes. The present study was carried out to examine the vegetation analysis, density, diversity and distribution of willow species, present status and potential willow plantation sites and uses. The results of present study revealed that a higher species density was recorded at middle altitude villages （Jahlma-3,ooo m asl and Hinsa-2,7oo m asl）, except, a higher density of S. fragilis was at Khoksar （3,200 m asl） in plantation forestry on south-facing slopes. In forests, S. fragilis was planted mainly along the water channels, resulted a low density. The shrubby willow species occurred naturally in the entire Lahaul valley up to an altitude of 3,850 m asl. 81% of households felt the scarcity of willow trees, whereas, 19% of households were satisfied with the willow trees they owned. The majority of willow species were planted in middle altitudes on privately owned irrigated lands. It was rated most potential prospective willow planting siteby the farmers. Small size of land-holdings was one of the main constraints for establishing a large number of willow plantations. Commercial aspects of willow species need to be investigated to encourage the farmers to plant more willows further.

Recent Data on Birds of Kinshasa in Democratic Republic of Congo

The study aimed at understanding the current avifauna characteristics, like composition, species diversity and evolution, in the city of Kinshasa. The study was conducted from 2006 to 2014, using observation, photography and Japanese nets. Results of the study indicate that there are 131 species of birds, which represents 40 families and 16 orders. Avifauna of Kinshasa represents 11% of species of the all country. Among those species, 12 are new. Passerines are the most, representing 86 species and 21 families, and are the most diversified. Few species have extended their geographical distribution and some are migratory. Overtime, avian fauna of Kinshasa region has undergone a lot of changes in its composition and diversity. Horizontal extension of the city associated with the consecutive various changes of the habitats seems to be the principal factors which modulate those characteristics. However, the study found that the majority of these species were under precarious statute of conservation.

Water use strategy of Ammopiptanthus mongolicus community in a drought year on the Mongolian Plateau

Aims In desert ecosystems,water is a restricting factor for plant growth and vegetation dynamics.The relatively stable water source from deep soil profile or groundwater is important for plant survival during drought.Understanding water use strategy of endangered species,in desert ecosystem is essential for their conservation and restoration such as Ammopiptanthus mongolicus on the Mongolian Plateau.Methods The stable isotope method ofδD andδ^(18)O was used to examine the main water sources of A.mongolicus and two companion shrubs,e.g.Artemisia ordosica and Artemisia xerophytica.The contribution of different water sources to each species was calculated by IsoSource model.Leafδ13C was used to compare long-term water use efficiency of three shrubs.Soil moisture and root distribution of three shrubs was measured to explain plant water use strategy.Important Findings The results showed that A.mongolicus relied on groundwater and 150–200 cm deep soil water,with the former contributing to almost half of its total water source.Artemisia ordosica mainly used 150–200 cm deep soil water,but also used shallow soil water within 100 cm in summer and autumn.Artemisia xerophytica mainly used 150–200 cm deep soil water and groundwater,with the latter contributing to about 30%–60%of its total water source.The three shrubs had dimorphic or deep root systems,which are in accord with their water sources.The WUE in the evergreen shrub A.mongolicus was higher than in two deciduous Artemisia shrubs,which may be an adaptive advantage in desert ecosystem.Therefore,groundwater is an important water source for the endangered shrub A.mongolicus in a drought year on Mongolian Plateau.Ammopiptanthus mongolicus and two Artemisia shrubs competed for deep soil water and groundwater.

Germination strategies under climate change scenarios along an aridity gradient

Aims Climate change in the eastern Mediterranean region will have a strong impact on ecosystem functioning and plant community dynamics due to a reduction in annual rainfall and increased variability.We aim to understand the role of seed banks as potential buffers against climatic uncertainty determined by climate change.Methods We examined germination strategies of 18 common species present along an aridity gradient.Data were obtained from soil seed banks germinated during nine consecutive years from arid,semi-arid,Mediterranean and mesic Mediterranean ecosystems.At the semi-arid and Mediterranean sites,rainfall manipulations simulating 30%drought and 30%rainfall increase were applied.Germination strategies were tested under optimal irrigation conditions during three consecutive germination seasons to determine overall seed germinability in each soil sample.Changes in germination strategy were examined using a novel statistical approach that considers the climatic and biotic factors that may affect seed germinability.Important Findings The results showed that dominant species controlled their germination fractions by producing seeds with a different yearly germination fraction probability.The amount of rainfall under which the seeds were produced led to two major seed types with respect to germinability:high germinability,seeds leading to transient seed banks,and low germinability,seeds leading to persistent seed banks.We conclude that differential seed production among wet and dry years of both seed types creates a stable balance along the aridity gradient,enabling the soil seed bank to serve as a stabilizing mechanism buffering against rainfall unpredictability.Additionally,we present a general model of germination strategies of dominant annual species in Mediterranean and arid ecosystems that strengthens the notion of soil seed banks as buffers against climatic uncertainty induced by climate change in the region.