毛乌素沙地根茎禾草拂子茅对异质性水分供应的表型可塑性

拂子茅(Calamagrostis epigejos（L.)Roth)为根茎型多年生禾草,具细长根茎。为了探讨拂子茅在异质性水分环境中的表型差异,在内蒙古鄂尔多斯高原的毛乌素沙地对拂子茅由母株、子株组成的分株对给予了高水、低水两种不同的异质性土壤水分处理。实验结果表明：土壤水分状况显著地影响着拂子茅分株的生长表型。在高土壤水分条件下,拂子茅的分株产生的根茎、新生后代分株较多,并使生物量主要分配于地上部分,地上生物量积累多;在低土壤水分条件下,拂子茅分株产生较少的根茎与新生后代分株,并且分配到根系的生物量明显增大。在具有一定对比度的异质性土壤水分环境中,拂子茅分株并不因相连的其他分株所处的土壤水分状况而在根茎生长、新生后代分株的产生和生物量分配等特征上,与同质环境中的具有相同土壤水分状况的分株相比,有明显差异。这些结果揭示：拂子茅仅以分株的形式对异质性水分供应发生表型反应;相连的克隆分株在向顶向和向基向这两个基本方向上,不能对另一分株的土壤水分状况在生K表型上发生反应,它们在水分关系上可能是相互相对独立的。分株的相对独立可能有利于在气候干旱、扰动强烈的沙地环境中实现风险分摊,提高基株的存活几率。     

Effects of different planting methods on the early establishment of two introduced tree species in the Mu Us Sandy Land of China

We investigated the effects of planting density and relative ground height (distance from the water table) on the early establishment of two introduced tree species [Mongolian pine (Pinus sylvestris var. mongolica) and white poplar (Populus alba var. pyramidalis)] in the Mu Us Sandy Land of China; we used GLMM to analyze experimental effects. In total, 14 afforestation plots (seven plots per species) with variable relative ground heights were established on a shifting sand dune. Trees were planted at intervals of 3, 5, and 7 m, and the distances between neighboring trees were fixed within plots. Planting intervals and numbers of neighboring trees were treated as measures of planting density, and relative ground height was treated as an indicator of water supply stability. For both species, tree survival rates decreased with increasing planting interval; the number of neighboring trees had a positive effect on survival. The effect of relative ground height differed between species. Pine tree survival rates decreased with increased relative ground height, while the survival rates of poplar trees were unaffected. We recommend that pine trees be planted at high density on lower sectors of sand dunes to prevent wind erosion in early spring. Poplar trees should be planted at high density without reference to relative ground height for the provision of fuelwood.     

Effects of sand burial depth on the root system of Salix cheilophila seedlings in Mu Us Sandy Land, Inner Mongolia, China

Salix cheilophila Schneid. is a naturally occurring Salix species in Mu Us Sandy Land, Inner Mongolia, China. We focused on the morphological adaptability of S. cheilophila to sand dune burial. For morphological measurements, 32 S. cheilophila seedlings were removed from a community which was in the process of being buried by a shifting sand dune. Each seedling collected included the entire root system. We measured the number, length, and biomass of the adventitious roots, primary lateral roots, and taproot, and compared the morphological characteristics of the root system, including adventitious roots, for seedlings buried to various levels in the sand. The growth range of adventitious roots increased as the length of the buried portion of the main shoot increased. In addition, the total dry weight of all current-year shoots tended to increase gradually with increasing total dry weight of the adventitious roots. These results suggest that S. cheilophila tends to make use of the sedimentary sand layer that accompanies shifting sand dunes. However, there was no correlation between biomass or number of adventitious roots and the length of the buried part of the main shoot. Thus, S. cheilophila does not grow adventitious roots proportional to the buried part. These morphological characteristics of the root system, including the adventitious roots, may indicate that S. cheilophila has poor morphological adaptability to sand dune burial.     

Life history of Juniperus sabina L. adapted to the sand shifting environment in the Mu Us Sandy Land,China: A review

We have reviewed publications on the physiological and ecological features of the growth and regeneration processes of Juniperus sabina L. which grows in semiarid sandy land in the Ordos plateau in northern China where desertification has progressed over time. J. sabina is a key native plant species used for ecological restoration in this region. The life history of J. sabina in this sandy land that has been revealed through this review includes several unique features: (1) both vegetative and seed propagations are observed, but seed propagation is not successful in the location where the mature J. sabina stands. Instead, seed propagation can occur at a different place with different landscapes from the mature stands. (2) Nurse plants play an important role in providing the microclimatic environment necessary for the growth of J. sabina seedlings and young plants. (3) During the horizontal and vertical growth processes of the J. sabina patch, the root system was affected by burial in shifting sand and consequently acquired greater access to the water supply in deeper soil horizons, which could support larger growth. These characteristics suggested that the regeneration by seed propagation and growth strategy of J. sabina in this region was strongly affected by sand movement and the landscape that is generated by sand movement.

     

毛乌素沙地南缘沙柳灌丛土壤水分及水量平衡

以毛乌素沙地南缘沙柳人工固沙灌丛为研究对象,对不同栽植密度(0.2、0.6和0.8株·m-2)沙柳灌丛生长季土壤水分动态和蒸散量变化进行研究.结果表明:不同栽植密度沙柳灌丛区土壤水分动态和蒸散量存在明显差异,土壤含水量随着栽植密度增加呈单峰型曲线;生长季内沙柳灌丛土壤含水量变化呈“S”形曲线,并与降雨存在密切的关系.蒸散量以栽植密度0.8株·m-2的沙柳灌丛最高(114.5 mm),占同期降雨量的90.8％;以0.6株·m-2的沙柳灌丛最低(109.7 mm).根据生长季土壤水分动态和水分平衡特征,毛乌素沙地南缘沙柳灌丛适种密度为0.6株·m-2.     

Exclusion effects on vegetation characteristics and their correlation to soil factors in the semi-arid rangeland of Mu Us Sandland,China

Exclusion has been applied as a main measure for re-vegetation all over the world.This paper,by comparing the results of year-round exclusion,seasonal exclusion,and non-exclusion,quantified the vegetation variations under three different exclusion measures and their correlation to soil factors.The analysis results for community species component and plant diversity using multi-response permutation procedures (MRPPs)showed that exclusion did change the species component and increase plant diversity remarkably,while the period of exclusion had no significant influence on these two community features.The indicator species analysis and calculation of similarity indices indicated that community for year-round exclusion were becoming xerophytization and unpalatability,and showed highly spatial heterogeneity of plant species distribution,whereas community for seasonal exclusion was under stable non-equilibrium condition.Detrended correspondence analysis (DCA)and detrend canonical correspondence analysis (DCCA)results of relationship between plant species and soil variables demonstrated that soil moisture was a controlling factor for plant species component,microbiotic soil crust cover,soil organic matter,and soil bulk density had significant effects on soil moisture,among which microbiotic soil crust was a leading factor owing to its limitation to rainfall infiltration on the one hand,and its constraints to entrance of herbaceous seeds into soil or to germination of soil seeds on the other hand.As a result of long-term removal of animal grazing,crust kept intact in year-round exclusion community,which was a main reason of community xerophytization.It was also obvious from ordination results that some important environmental factors,such as tempo-spatial change of rainfall and corresponding tempo-spatial change of soil moisture,were neglected during direct gradient analysis.In addition,biodiversity was close related to soil nutrients as well as to soil moisture condition (soil water content and crust cover),and it had positive relation to available N,and negative relation to available P.Higher soil N had advantage to non-leguminous plants growth on nutrition-poor sand land definitely.The impact of P to community component was unclear and should be studied from plant physiology.Further researches on nonequilibrium theory in semi-arid rangeland will provide a scientific and flexible animal development paradigm for being implementing livestock fen-raising and grazing-forbidden policies in China.     

Exclusion effects on vegetation characteristics and their correlation to soil factors in the semi-arid rangeland of Mu Us Sandland, China

Exclusion has been applied as a main measure for re-vegetation all over the world. This paper, by comparing the results of year-round exclusion, seasonal exclusion, and non-exclusion, quantified the vegetation variations under three different exclusion measures and their correlation to soil factors. The analysis results for community species component and plant diversity using multi-response permutation procedures (MRPPs) showed that exclusion did change the species component and increase plant diversity remarkably, while the period of exclusion had no significant influence on these two community features. The indicator species analysis and calculation of similarity indices indicated that community for year-round exclusion were becoming xerophytization and unpalatability, and showed highly spatial heterogeneity of plant species distribution, whereas community for seasonal exclusion was under stable non-equilibrium condition. Detrended correspondence analysis (DCA) and detrend canonical correspondence analysis (DCCA) results of relationship between plant species and soil variables demonstrated that soil moisture was a controlling factor for plant species component, microbiotic soil crust cover, soil organic matter, and soil bulk density had significant effects on soil moisture, among which microbiotic soil crust was a leading factor owing to its limitation to rainfall infiltration on the one hand, and its constraints to entrance of herbaceous seeds into soil or to germination of soil seeds on the other hand. As a result of long-term removal of animal grazing, crust kept intact in year-round exclusion community, which was a main reason of community xerophytization. It was also obvious from ordination results that some important environmental factors, such as tempo-spatial change of rainfall and corresponding tempo-spatial change of soil moisture, were neglected during direct gradient analysis. In addition, biodiversity was close related to soil nutrients as well as to soil moisture condition (soil water content and crust cover), and it had positive relation to available N, and negative relation to available P. Higher soil N had advantage to non-leguminous plants growth on nutrition-poor sand land definitely. The impact of P to community component was unclear and should be studied from plant physiology. Further researches on non-equilibrium theory in semi-arid rangeland will provide a scientific and flexible animal development paradigm for being implementing livestock fen-raising and grazing-forbidden policies in China. __________ Translated from Acta Ecologica Sinica, 2005, 25(12): 3212–3219 [译自: 生态学报]     

Phenology of nine common woody species in semi-arid,deciduous Kalahari Sand vegetation

The phenological patterns of 9 woody species that are common components of Kalahari Sand communities were observed over a period of 32 months. The observations were made on plants adjacent to the soil moisture study sites which have been described earlier (Childes & Walker 1987). A pre-rain flush was noted in the 2 shrub/small tree species Ochna pulchra and Terminalia sericea. Leaf fall in all species was related to a decrease in soil moisture and minimum temperature. The rooting habits and other adaptations of the species resulted in a sequential leaf fall in the communities. Open woodland and scrub species such as Pterocarpus angolensis showed a generally synchronised pre-rain flowering, while the closed woodland species e.g. Baikiaea plurijuga had protracted asynchronous flowering periods. Fruit ripening generally occurred in the dry season when conditions were ideal for fruit and seed dispersal.     

Different Patterns of Gas Exchange and Photochemical Efficiency in Three Desert Shrub Species Under Two Natural Temperatures and Irradiances in Mu Us Sandy Area of China

Field studies of gas exchange and chlorophyll fluorescence of three desert shrub species, Hedysarum fruticosum var. mongolicum, Artemisia ordosia, and Salix pasmmophylla, showed different patterns under different leaf temperature (T₁) and incident photosynthetic photon flux density (PPFD). H. fruticosum var. mongolicum and A. ordosia exhibited higher P _N and g _s than S. pasmmophylla, especially under very high T₁ (>46 °C) and high PPFD (>2 100 µmol m^–2 s^–1) in hot summer. The decreases of P _N with the diurnal course were due mainly to stomata closure. However, P _N of S. pasmmophylla was seriously depressed by very high temperature from midday to evening as shown by the negative P _N in hot summer, whereas none of such depression was found in spring. Maximal spring photochemical efficiency of photosystem 2 (PS2), i.e, F_v/F_m, was the lowest at 16:00, indicating the injury of PS2 by heat at this stage. In hot summer again, all the three shrubs underwent pronounced midday depression of P _N and g _s, while in spring they showed a one-peak response. And the first peak appeared 2 h earlier in hot summer than in spring for all the three shrubs. It was the high temperature that led to the different patterns of gas exchange and the serious depression of P _N in S. pasmmophylla. H. fruticosum var. mongolicum and A. ordosia were much more tolerant to heat and high irradiance than S. pasmmophylla, which fixed most of CO₂ at the fast growing stage in spring. Nevertheless, in hot summer it had to survive the severe hot environment through strong respiration and storage of CO₂ only in the early morning.     

Effects of Sand Dune Stabilization on the Spatial Pattern of Artemisia ordosica Population in Mu Us Desert,Northwest China

Vegetation patterns are strongly influenced by sand mobility in desert ecosystems. However, little is known about the spatial patterns of Artemisia ordosica, a dominant shrub in the Mu Us desert of Northwest China, in relation to sand fixation. The aim of this study was to investigate and contrast the effects of sand dune stabilization on the population and spatial distribution of this desert shrub. Spatial autocorrelation, semi-variance analysis, and point-pattern analysis were used jointly in this study to investigate the spatial patterns of A. ordosica populations on dunes in Yanchi County of Ningxia, China. The results showed that the spatial autocorrelation and spatial heterogeneity declined gradually, and the distance between the clustered individuals shortened following sand dune fixation. Seedlings were more aggregated than adults in all stage of dune stabilization, and both were more aggregated on shifting sand dunes separately. Spatial associations of the seedlings with the adults were mostly positive at distances of 0–5 m in shifting sand dunes, and the spatial association changed from positive to neutral in semi-fixed sand dunes. The seedlings were spaced in an almost random pattern around the adults, and their distances from the adults did not seem to affect their locations in semi-fixed sand dunes. Furthermore, spatial associations of the seedlings with the adults were negative in the fixed sand dune. These findings demonstrate that sand stabilization is an important factor affecting the spatial patterns of A. ordosica populations in the Mu Us desert. These findings suggest that, strong association between individuals may be the mechanism to explain the spatial pattern formation at preliminary stage of dune fixation. Sand dune stabilization can change the spatial pattern of shrub population by weakening the spatial association between native shrub individuals, which may affect the development direction of desert shrubs.     

Efficiency and regulation of water transport in some woody and herbaceous species

The efficiency with which plants transport water is related to the water potential differences required to drive water fluxes from the soil to the leaf. A comparative study of two woody and three herbaceous species (Citrus sinensis L. cv. Koethen, Pyrus kawakami L., Helianthus annuus L. cv. Mammoth Russian, Capsicum frutescens L. cv. Yolo Wonder, and Sesamum indicum L. cv. Glauca) indicated contrasts in water transport efficiency. Depression of leaf water potential in response to transpiration increases was found in the woody species; the herbaceous species, however, had more efficient water transport systems and presented no measurable response of leaf water potential to transpiration changes. Different maximum transpiration rates under the same climatic conditions were observed with different species and may be accounted for by stomatal response to humidity gradients between leaf and air. Leaf diffusion resistance in sesame increased markedly as the humidity gradient was increased, while leaf resistance of sunflower responded less to humidity. Stomata appeared to respond directly to the humidity gradient because changes in leaf water potential were not detected when leaf resistance increased or decreased.     

翅果油树及其群落中7种优势木本种类的叶性特征比较

Taking Elaeagnus mollis Diels and seven dominant woody species in its community from Yicheng County of Shanxi Province as research objects, leaf traits including specific leaf area (SLA), nitrogen content in leaf per unit area ( Narea ) , leaf dry matter content ( LDMC ) and photosynthetic nitrogen use efficiency ( PNUE ) were compared, and correlations of SLA value with LDMC and PNUE values were analyzed. The results show that there are different degree variations in four indexes of leaf traits of E. mollis, Vitex negundo var. heterophylla ( Franch.) Rehd., Broussonetia papyrifera ( Linn.) L' Hér. ex Vent., Lespedeza bicolor Turcz., Caragana microphylla Lam., Rosa xanthina Lindl., Amygdalus davidiana ( Carrière) de Vos ex Henry and Periploca sepium Bunge, in which, SLA value with the largest coefficient of variation ( 404%) , and LDMC value with the lowest coefficient of variation ( 103%) . Compared with other tested species, SLA and PNUE values of E. mollis are the lowest ( 103 cm-2 · g-1 and 108 μmol · mol-1 · s-1 , respectively) , while its Narea value is the highest ( 0243 g · m-2 ) , and its LDMC value is also relatively high ( 0380 g·g-1 ) . SLA value of eight tested species show an extremely significant positive correlation ( P<001) with PNUE value, and a significant negative correlation ( P<005 ) with LDMC value, correlation coefficient are 0923 and -0718, respectively, indicating that SLA value is an important parameter of leaf photosynthetic capacity and resource utilization ability. It is suggested that compared with other dominant woody species, E. mollis is more sensitive to environmental change, and has a poor environmental adaptability.     

Seedlings of the semi-shrub Artemisia ordosica are resistant to moderate wind denudation and sand burial in Mu Us sandland, China

Sand movement is a common stress for plants in dune ecosystems. Seedlings in such an environment often experience various degrees of denudation or burial. A field experiment was conducted with Artemisia ordosica, a dominant semi-shrub species in Mu Us sandland, China, to test seedling survival and growth under different degrees of denudation and burial. Seedlings from two cohorts with height of 5.0 ± 0.02 cm (S1) and 9.3 ± 0.09 cm (S2) were selected and randomly subjected to three denudation treatments (2.5, 5, and 10 cm), five burial treatments (2.5, 5, 7.5, 10, and 15 cm), or a control. S2 seedlings had a higher survivorship than S1 seedlings, especially under severe denudation (10 cm) and complete burial (5 cm in S1; 10 cm in S2). Seedling survivorship was unaffected by moderate burial (<5 cm in S1; <10 cm in S2) or denudation (<10 cm), but it was significantly reduced under complete burial or severe denudation. Seedling growth in leaf area, height, and biomass only declined in severe denudation or complete burial. Seedling burial led to higher biomass investment in shoots, while the reverse was the case in denudation. The results indicate A. ordosica is highly tolerant to moderate burial and denudation, showing adaptive responses that likely increase survival. Differences in responses between seedling cohorts suggest that large seedling size is beneficial for successful establishment in sandy environments and measures to prevent severe denudation and burial of recently germinated seedlings are necessary in attempts to restore steppe vegetations.     

New species and records of Paliphora from the Brazilian semi-arid region

In the course of studies about conidial fungi that grow on plant debris in the semi-arid region of Brazil, four species of Paliphora were found on unidentified dicotyledonous plants. Paliphora intermedia and P. porosa are recorded for the first time for South America and the neotropics respectively. Paliphora inflata and P. multiseptata are proposed as new species. A key and synoptic table of characters of the five known species of Paliphora are provided.     

Taxonomy of the genus Peyerimhoffia Kieffer from Mainland China,with a description of seven new species (Diptera,Sciaridae)

The taxonomy of the genus Peyerimhoffia Kieffer in China was studied. Eight species were recognized, including seven new species that are herein described and illustrated: P. hamatasp. n., P. obesasp. n., P. sparsulasp. n., P. longiprojectasp. n., P. brachypoduasp. n., P. yunnanasp. n., and P. shennongjianasp. n. In addition, P. vagabunda (Winnertz, 1867) is reported for the first time from China. A key to these Chinese species is provided.     

Attenuation of UV radiation by plant cuticles from woody species

Transmittance spectra of isolated plant cuticles were measured in the wavelength range from 270 to 600 nm. The cuticles were enzymatically isolated from the leaves of 27 species (26 evergreen or deciduous woody, one succulent herbaceous) and from four species of fruits. With the exception of subtropical and tropical species all plants were cultivated in the field. The cuticles of the species studied strongly attenuated ultraviolet (UV) radiation at wavelengths < 400 nm while they were practically translucent in the visible range. Relatively broad transmittance minima occurred at wavelengths from 280 to 320 nm (UV-B). Spectral transmittances at 300 nm ranged from 0.004 (Ilex aquifolium) to 0.50 (Prunus avium) for leaf cuticles and from 0.00023 (Cydonia oblonga) to 0.005 (Mains domestica) for fruit cuticles. The constitutive UV protection by cuticular pigments may be supplemented, to varying degrees, by pigments located in the epidermal cell wall and protoplast. Thus, it is concluded that only a small fraction of incident UV-B radiation may actually reach the sensitive tissues of the leaves of non-herbaceous species and of fruits.