Distribution patterns of planted-shrubs of different restoration ages in artificial sand-fixing regions in the southeastern Tengger Desert

Plant density and spatial distribution in artificial vegetation is obviously initialized at the planting stage. Plant dynamics and spatial pattern may change over time as the result of interactions between individual plants and habitats, but whether it’s applied for desert shrubs in artificial sand-fixing regions remains unknown. Here we examined changes in plant density and distribution patterns of three shrubs(Artemisia ordosica Krasch, Caragana korshinskii Kom, and Hedysarum scoparium Fisch.) in different regions, which have been restored for 27, 32 and 50 years(R27, R32, R50), respectively. The vegetation analysis shows that A. ordosica was the dominated species across the 3 restoration regions. The density of A. ordosica and H. scoparium show a significant increase from R27 to R32, then decreased in R50. The density of C. korshinskii was low in R32 and R50, lower in R27. The variance-to-mean ratio(VMR) was used to characterize spatial distribution patterns to fit the observed densities of the three shrubs by frequency. A. ordosica and C. korshinskii both show significantly clumped distributions in three restoration regions. H. scoparium show a uniform distribution in R27 and R50, but a clumped distribution in R32. These results show that A. ordosica seems to be more adaptable in revegetated desert areas compared to C. korshinskii and H. scoparium. Pattern analysis suggests a successive replacement of C. korshinskii, which had low proportions of survived shrubs, by the dominant A. ordosica. This study contributes to the understanding of the distribution patterns of shrubs plants in revegetation projects in arid desert areas.

Shrubs proliferated within a six-year exclosure in a temperate grassland—Spatiotemporal relationships between vegetation and soil variables

Overgrazing has been considered one of the maj or causes that trigger shrub encroachment of grassland. Proliferation of shrubs in grassland is recognized as an important indicator of grassland degradation and desertification. In China, various conservation measures, including enclosures to reduce livestock grazing, have been taken to reverse the trend of grassland desertification, yet shrubs have been reported to increase in the grasslands over the past decades. In late 2007, we set up a 400-m-by-50-m exclosure in a long-term overgrazed temperate grassland in Inner Mongolia, with the ob- jective to quantify the spatiotemporal relationship between vegetation dynamics, soil variables, and grazing exclusion. Soil moisture was continuously monitored within the exclosure, and cover and aboveground biomass of the shrubs were measured inside the exclosure in 2007, 2009, 2010, 2012, and 2013, and outside the exclosure in 2012 and 2013. We found the average shrub cover and biomass significantly increased in the six years by 103 % and 120%, respectively. The result supported the hypothesis that releasing grazing pressure following long-term overgrazing tends to trigger shrub invasion into grassland. Our results, limited to a single gradient, suggest that any conservation measures with quick release of overgrazing pressure by enclosure or other similar means might do just the opposite to accelerate shrub en- croachment in grassland. The changes in vegetation cover and biomass were regressed on the temporal average of the soil moisture content by means of the generalized least square technique to quantify the effect of the spatial autocor- relation. The result indicates that the grass cover and biomass significantly increased with the top, but decreased with the bottom layer soil moisture. The shrub cover and biomass, on the other hand, decreased with the top, but increased with bottom soil moisture, although the regression coefficients for the shrubs were not statistically significant. Hence this study supports the two-layered soil model which assumes grasses and shrubs use belowground resources in dif- ferent depths.

Effects of sand-fixing and windbreak forests on wind flow:a synthesis of results from field experiments and numerical simulations

Sand-fixing and windbreak forests are widely used to protect or/and improve the ecological environments in arid and semi-arid regions. A full understanding of wind flow characteristics is essential to arranging the patterns of these protective forests for enhancing the effectiveness. In this study, the wind velocity over the underlying surface with sand-fixing forests and windbreak forests at the heights of 1–49 m was monitored from two 50-m high observation towers in an oasis of Minqin, Gansu Province of China. The wind velocities were simulated at different locations over these protective forests between those two towers by a two-dimensional Computational Fluid Dynamics（CFD） model. The results showed that at the heights of 1–49 m, the wind velocity profiles followed a classical logarithm law at the edge of the oasis and a multilayer structure inside the oasis. With increasing number of sand-fixing forest and windbreak forest arrays, the wind velocity at the heights of 1–49 m generally decreased along the downstream direction of the prevailing wind. Specifically, below the height of windbreak forests, the wind velocity decelerates as the airflow approaches to the windbreak forests and then accelerates as the airflow passes over the windbreak forests. In contrast, above the height of windbreak forests, the wind velocity accelerates as the airflow approaches to the windbreak forests and then generally decelerates as the airflow passes over the windbreak forests. Both the array number and array spacing of sand-fixing and windbreak forests could influence the wind velocity. The wind protection effects of sand-fixing forests were closely related to the array spacing of windbreak forests and increased with the addition of sand-fixing forests when the array of the forests was adequately spaced. However, if the array spacing of windbreak forests was smaller than seven times of the heights of windbreak forests, the effects were reduced or completely masked by the effects of windbreak forests. The results could offer theoretical guidelines on how to systematically arrange the patterns of sand-fixing and windbreak forests for preventing wind erosion in the most convenient and the cheapest ways.

Drought Resistance of Twelve Desert Shrubs at Seedling Stage of Ulan Buh Desert Ecosystem

[Objective] To establish drought resistance evaluation index system of desert shrubs,and provide scientific support for selecting quality tree species.[Method] Taking 2-year-old seedlings of 12 desert shrubs in Ulan Buh Desert ecosystem as the test materials,7 water physiological indexes were tested,principal component analysis and cluster analysis were applied to explore drought resistance of the shrubs.[Results](a) Water potential of Ephedra distachya Linn.,Nitraia tangutorum Bobr.,Caragana korshinski Kom.was lower than that of the other 9 species;bound water content(V_a) and bound water/free water ratio(V_a/V_s) of Zygophyl um xanthoxylon Maxim.was 64.20% and 3.3,higher than the others';transpiration rate of Atraphaxis bracteata A.Los.,Nitraia tangutorum Bobr.and Tamarix elongata Ldb.was significantly lower than the others';constant weight time of Haloxylon ammodendron(C.A.Mey.) Bunge and Ephedra distachya Linn.was the longest(144 h);residual moisture content of Ammopiptanthus mongolicus Maxim.was the highest(44.80%).(b) Water potential,bound water/free water(V_a/V_s),residual moisture content,bound water,constant weight time,and transpiration rate had great impact on drought resistance of plant,and the accumulative variance contribution rate achieved 87.59%.[Conclusion] According to the drought resistance,the 12 species were classified into 3 categories,namely shrubs with strong drought resistance(Ephedra distachya Linn.),shrubs with moderate drought resistance(Haloxylon ammodendron(C.A.Mey.) Bunge,Nitraia tangutorum Bobr.,and Zygophyllum xanthoxylon Maxim.);shrubs with poor drought resistance(Hedysarunn scoparium Fisch,Hedysarum mongolicum Turcz.,Tamarix elongata Ldb.,Caragana korshinskii Kom.,Ammopiptanthus mongolicus Maxim.,Atraphaxis bracteata A.Los.,Cal igonum mongolicum Mattei.,and Caragana microphylla Lam.).

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land,northern China

Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur frequently.Vegetation plays a significant role in controlling wind erosion.Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land.It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land.This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019.The coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,respectively.The annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,respectively.The annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,respectively.The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,respectively.Site A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were minimal.The results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface changes.The higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and sand-fixing.Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.

Liquefaction and FTIR analysis of two desert shrubs Salix psammophila and Caragana intermedia

In order to extend the investigation of the characteristics of desert shrub liquefaction and the structure of liquefied desert shrubs, we studied the liquefaction of Salixpsammophila and Caragana intermedia in the presence of phenol and used FTIR analysis on unliquefied and liquefied S. psammophila and C. intermedia. The results showed that the liquefaction effects are enhanced with an increase in temperature, catalyst content and liquid ratio. FTIR analysis proved that more active functional groups appeared after S. psammophila and C. intermedia were liquefied in the presence of phenol. These results can provide a theoretical basis for the further utilization of liquefied S. psammophila and C. intermedia and the development of desert shrubs in a new utilization field.

Rainfall partitioning by desert shrubs in arid regions

We measured the rainfall partitioning among throughfall, stemflow, and interception by desert shrubs in an arid region of China, and analyzed the influence of rainfall and canopy characteristics on this partitioning and its ecohydrological effects. The percent-ages of total rainfall accounted for by throughfall, stemflow, and interception ranged from 78.85±2.78 percent to 86.29±5.07 per-cent, from 5.50±3.73 percent to 8.47±4.19 percent, and from 7.54±2.36 percent to 15.95±4.70 percent, respectively, for the four shrubs in our study (Haloxylon ammodendron, Elaeagnus angustifolia, Tamarix ramosissima, and Nitraria sphaerocarpa). Rain-fall was significantly linearly correlated with throughfall, stemflow, and interception (P < 0.0001). The throughfall, stemflow, and interception percentages were logarithmically related to total rainfall (P < 0.01), but were quadratically related to the maximum 1-hour rainfall intensity (P < 0.01). The throughfall and stemflow percentages increased significantly with increasing values of the rainfall characteristics, whereas the interception percentage generally decreased (except for average wind speed, air temperature, and canopy evaporation). Regression analysis suggested that the stemflow percentage increased significantly with increasing crown length, number of branches, and branch angle (R2 = 0.92, P < 0.001). The interception percentage increased significantly with increasing LAI (leaf area index) and crown length, but decreased with increasing branch angle (R2 = 0.96, P < 0.001). The mean funnelling percentages for the four shrubs ranged from 30.27±4.86 percent to 164.37±6.41 percent of the bulk precipitation. Much of the precipitation was funnelled toward the basal area of the stem, confirming that shrub stemflow conserved in deep soil layers may be an available moisture source to support plant survival and growth under arid conditions.

Preparation and Water Retention Properties of Clay-based Sand-fixing and Grass-planting Materials

Targeting the problem of available water conservation in sand fixation, the sand-fixing and grass-planting materials were prepared with clay modified by emulsifying vegetable waxes and octylphenol polyoxyethylene ether （OP4）. The water retention property was studied in simulating desertification environmental climate and the materials were characterized by means of UV-Vis, SEM, FTIR, XRD and TGA measurements. The experimental result showed that the materials had excellent water retention properties, due to that vegetable waxes adhered evenly to clay particle surfaces, made the clay pores changing from hydrophilic to hydrophobic and so inhibited the water evaporation. Grass-planting experiment showed that, with reasonable mass ratio of clay, vegetable waxes and surfactant, the materials not only inhibited water evaporation but also maintained sound air permeability so shat the germination rate and survival rate of grass were significantly improved.

Allometric models for aboveground biomass of six common subtropical shrubs and small trees

The aboveground biomass(AGB)of shrubs and small trees is the main component for the productivity and carbon storage of understory vegetation in subtropical secondary forests.However,few allometric models exist to accurately evaluate understory biomass.To estimate the AGB of five common shrub(diameter at base<5 cm,<5 m high)and one small tree species(<8 m high,trees’s seedling),206 individuals were harvested and species-specific and multi-species allometric models developed based on four predictors,height(H),stem diameter(D),crown area(Ca),and wood density(ρ).As expected,the six species possessed greater biomass in their stems compared with branches,with the lowest biomass in the leaves.Species-specific allometric models that employed stem diameter and the combined variables of D~2H andρDH as predictors accurately estimated the components and total AGB,with R^(2) values from 0.602 and 0.971.A multi-species shrub allometric model revealed that wood density×diameter×height(ρDH)was the best predictor,with R^(2) values ranging from between 0.81 and 0.89 for the components and total AGB,respectively.These results indicated that height(H)and diameter(D)were effective predictors for the models to estimate the AGB of the six species,and the introduction of wood density(ρ)improved their accuracy.The optimal models selected in this study could be applied to estimate the biomass of shrubs and small trees in subtropical regions.

Distribution and Estimation of Aboveground Biomass of Alpine Shrubs along an Altitudinal Gradient in a Small Watershed of the Qilian Mountains, China

Shrublands serve as an important component of terrestrial ecosystems, and play an important role in structure and functions of alpine ecosystem.Accurate estimation of biomass is critical to examination of the productivity of alpine ecosystems, due to shrubification under climate change in past decades.In this study, 14 experimental plots and 42 quadrates of the shrubs Potentilla fruticosa and Caragana jubata were selected along altitudes gradients from 3220 to 3650 m a.s.l.(above sea level) on semi-sunny and semi-shady slope in Hulu watershed of Qilian Mountains, China.The foliage, woody component and total aboveground biomass per quadrate were examined using a selective destructive method, then the biomass were estimated via allometric equations based on measured parameters for two shrub species.The results showed that C.jubata accounted for 1–3 times more biomass(480.98 g/m2) than P.fruticosa(191.21 g/m2).The aboveground biomass of both the shrubs varied significantly with altitudinal gradient(P<0.05).Woody component accounted for the larger proportion than foliage component in the total aboveground biomass.The biomass on semi-sunnyslopes(200.27 g/m2 and 509.07 g/m2) was greater than on semi-shady slopes(182.14 g/m2 and 452.89g/m2) at the same altitude band for P.fruticosa and C.jubata.In contrast, the foliage biomass on semi-shady slopes(30.50 g/m2) was greater than on semi-sunny slopes(27.51 g/m2) for two shrubs.Biomass deceased with increasing altitude for P.fruticosa, whereas C.jubata showed a hump-shaped pattern with altitude.Allometric equations were obtained from the easily descriptive parameters of height(H), basal diameter(D) and crown area(C) for biomass of C.jubata and P.fruticosa.Although the equations type and variables comprising of the best model varied among the species, all equations related to biomass were significant(P < 0.005), with determination coefficients(R2) ranging from 0.81 to 0.96.The allometric equations satisfied the requirements of the model, and can be used to estimate the regional scale biomass of P.fruticosa and C.jubata in alpine ecosystems of the Qilian Mountains.

Sand-fixing characteristics of Carex brunnescens and its application with straw checkerboard technique in restoration of degraded alpine meadows

Carex brunnescens（Pers.）, a typical clonal species, is considered to be the only herb found to date that can develop on sand dunes in Maqu alpine region of northwestern China. However, the characteristics that C. brunnescens resists to harsh alpine environment have not been documented. In this study, we conducted a field investigation to determine the morphological, reproductive, and sand-fixing characteristics of C. brunnescens. Concomitantly, we transplanted the belowground rhizomes of C. brunnescens to sand dunes and compared the abilities to restore degraded alpine meadows among sand dunes that had no further treatment（SD＋N）, sand dunes that had straw checkerboard technique but no transplanted rhizomes of C. brunnescens（SD＋SCT）, and sand dunes that had both SCT and transplanted rhizomes of C. brunnescens（SD＋SCT＋P）. We found that belowground vertical rhizomes and horizontal rhizomes（including branching rhizomes and main rhizomes） of C. brunnescens were highly developed and that population reproduction was dominated by horizontal rhizomes. C. brunnescens exhibited a significant sand-fixation effect under following conditions： population density was 145–156 ramets/m^2, vegetation cover was 31.2%–39.3%, total length of belowground rhizomes was 11,223 cm/m^2, total length of belowground first-order roots was 9161–10,524 cm/m^2, fresh weight of aboveground part was 198.5–212.6 g/m^2, and fresh weight of belowground part was 578.8–612.4 g/m^2. It should be particularly noted that SD＋SCT＋P treatment（sand dunes that had both straw checkerboard technique and transplanted rhizomes of C. brunnescens） was the best and SD＋N（sand dunes that had no further treatment） was the worst in terms of following biotic indicators： total number of reproductive ramets, total number of belowground rhizomes, and fresh weight of aboveground and belowground parts of C. brunnescens, contents of soil organic carbon, available nitrogen, microbial biomass carbon, and microbial biomass nitrogen. It implies that applying SCT in sand dunes and transplanting belowground rhizomes to sand dunes with SCT could improve both soil fertility and growth of C. brunnescens. These results suggest that the SCT-promoted high reproductive abilities of belowground rhizomes of C. brunnescens can successfully facilitate the establishment of ramets and can thus be an effective strategy to restore degraded vegetation in Maqu alpine region of northwestern China.

Aboveground Biomass and Water Storage Allocation in Alpine Willow Shrubs in the Qilian Mountains in China

The aboveground biomass allocation and water relations in alpine shrubs can provide useful information on analyzing their ecological and hydrological functions in alpine regions. The objectives of this study were to compare the aboveground biomass allocation, water storage ratio and distribution between foliage/woody components,and to investigate factors affecting aboveground biomass allocation and water storage ratio in alpine willow shrubs in the Qilian Mountains, China. Three experimental sites were selected along distance gradients from the riverside in the Hulu watershed in the Qilian Mountains. The foliage, woody component biomass, and water allocation of Salix cupularis Rehd.and Salix oritrepha Schneid. shrubs were measured using the selective destructive method. The results indicated that the foliage component had higher relative water and biomass storage than the woody component in the upper part of the crown in individual shrubs. However, the woody component was the major biomass and water storage component in the whole shrub level for S. cupularis and S.oritrepha. Moreover, the foliage/woody component biomass ratio decreased from the top to the basal level of shrubs. The relative water storage allocation was significantly affected by species types, but was not affected by sites and interaction between species and sites. Meanwhile, relative water storage was affectedby sites as well as by interaction between sites and species type.

Effects of shrubs and precipitation on spatial-temporal variability of soil temperature in microhabitats induced by desert shrubs

Soil temperatures at 0, 5, 10 and 20 cm depths were monitored cominuously at different microhabitats （beneath shrub canopy （BSC）; bare intershrub spaces （BIS）） induced by xerophytic shrub （Caragana korshinskii Kom.） canopy, respectively. We mainly aimed to assess the effects of shrub canopy and precipitation on the spatial-temporal variability of soil temperature. Results indi- cate that both precipitation and vegetation canopy significantly affect soil temperature. In clear days, soil temperatures within the BSC area were significantly lower than in the BIS at the same soil depth due to shading effects of shrub canopy. Diurnal variations of soil temperature show a unimoclal sinusoidal curve. The amplitude of soil temperature tended to decrease and a hysteresis of di- urnal maximum soil temperature existed at deeper soil layers. Vertical fluctuations of soil temperature displayed four typical curves. In the nighttime （approximately from sunset to sunrise）, surface temperature within the BSC area was higher than in the BIS. In rainy days, however, soil temperatures were affected mainly by precipitation and the shrub canopy had a negligible effect on soil temperature, and little difference in soil temperature at the same soil depth was found between the BSC area and in the BIS. Diurnal variations in soil temperature decreased exclusively as rainfall continued and the vertical fluctuations of soil tempera~＇e show an increased tendency with increasing soil depth.

Studies on the Traditional Uses of Some Medicinal Shrubs of Swat Kohistan,Pakistan

This paper is based on an ethnobotanical project carried out in the remote Hindukush mountain region of Swat Kohistan.Most of the local people still rely on medicinal plants for curing different diseases.However,the traditional use and pertinent knowledge of medicinal plants are on decline with the introduction of allopathic drugs in the study area.During present study,an effort was made to document the traditional knowledge of some important medicinal shrubs of Swat Kohistan.The traditional uses of 18 frequently used shrubs belonging to 12 different families were thus documented.The Kohistani people use these medicinal shrubs for curing multiple ailments and some of these are also exported to other parts of Pakistan.

Arid Agroecosystem Shrubs Enhance Enzyme Activities during the Dry Season

In Senegal, in the Sahel region, the agroecosystem is dominated by two Sahelian shrubs able to redistribute water from deep soil to the surface. This study was carried out to determine the impact of these shrubs on soil microbial activity. A 2 × 3 factorial design was set up during the dry and wet season with three soil treatments: rhizospheric, bulk and non-rhizospheric soil. During the dry season, the presence of shrubs resulted in significantly higher phosphatase acid activity for Guiera senegalensis (p < 0.001), respectively, 717 μg pNP/h/g of dry soil in the rhizosphere soil, 333 μg pNP/h/g in the bulk soil and 193 μg pNP/h/g in the non-rhizosphere soil. The same trend was observed for all other enzyme activities and MBC during both seasons except for mineral N. Mineral N was not statistically different between the rhizospheric and bulk soil during the dry season. β-glucosidase and phosphatase acid had the highest correlation with the rhizospheric soil during the dry season respectively 98% and 97%. Soil moisture content was highly correlated with the rhizospheric soil (85%), chitinase activity (99%) and β-glucosidase (97%). Shrubs maintained a moister environment during the dry season which was critical in stimulating microbial activities;this has significant implications for agroecosystem management in the Sahel.

Bio-Mechanical Investigation on the Physical Resilience of Selected Dominating Shrubs in Semi-Arid Region of Dodoma

Physical and mechanical disturbances which interfere with shrubs survival are very common in semi-arid regions. Biomechanical adoptive features of these shrubs therefore account for their competitive and survival possibilities. Current study investigated physico-ecological properties of five stem cuttings of selected dominating shrubs from Dodoma Municipal that explain their physical resilience. Experimental findings revealed that Acacia nilotica (AN) had the best mechanical adaptations by having the highest values of Young’s modulus of elasticity (E) 332.61 kPa, percentage critical height (PCH) 6.00, whole stem flexibility (WSF) 0.1, flexural stiffness (FS) 7.46 Nm2 as well as angle of deflection (AD). Ziziphus mucronata (ZM) was next to AN, followed by Grewia bicolor (GB) then Acacia tortilis (AT). Boscia grandiflora (BG) had the least mechanical adaptations with the lowest E of 20.94 kPa, PCH of 4.00, WSF of 0.09 as well as FS of 2.90 Nm2. This implied Acacia nilotica having the best ecological adaptations in the semi-arid region while Boscia grandiflora had the least adaptive feature compared to the rest.

Fuzzy comprehensive evaluation of five forage shrubs in Mu Us sandland, China

Chemical compositions during different growing periods, preference and in vitro digestibility at the post-fruiting period of five psammophyte shrubs, which include Caragana intermedia, Caragana korshinskii, Hedysarum scoparium, Hedysarum laeve, Salix psammophylla were determined. The nutritive values were synthetically evaluated in terms of chemical composition, preference and in vitro digestibility through fuzzy multifactorial model. The crude protein (CP) concentrations of the five shrubs had the tendency to decrease with growing stage, the peak values of C. intermedia, C. korshinskii and S. psammophylla appeared at blooming period and those of H. scoparium and H. laeve appeared at vegetative period. The neutral-detergent fiber (NDF), acid-detergent fiber (ADF) and lignin concentrations of C. intermedia, C. korshinskii and S. psammophylla were all decreased before post-fruiting period and then increased significantly;while the variation tendency of those of H. scoparium and H. leave were alike, and the lowest NDF, ADF and lignin concentrations were at vegetative period or post-fruiting period. The five shrubs can be used as feedstuffs, the synthetical nutritive value at the post-fruiting period were high in order of C. intermedia, H. scoparium, H. laeve, C. korshinskii and S. psammophylla. Considering the characteristics of growth and nutritive value, the optimum time to use these shrubs as feedstuffs is the post-fruiting period in autumn. Among the five shrubs, C. intermedia is the best as feed-stuff for raising the production of livestock.

Thirteen-year growth response of ponderosa pine plantations to dominant shrubs(Arctostaphylos and Ceanothus)

Thirteen-year growth response of ponderosa pine to various manipulations of understory vegetation was studied to determine if a threshold of understory cover can be established for plantation productivity and whether nitrogen-fixing Ceanothus species benefit plantation growth compared to non N-fixing Arctostaphylos species,given their ability to improve site fertility.Results showed that completely controlling competing vegetation increased plantation growth,as was universally expected,but the effects of partial shrub control on plantation performance was inconsistent.We did not find a benefit of nitrogenfixing shrubs on tree growth,as young plantation growth was slightly better in the non N-fixing plots compared to the N-fixing plots due to differences in shrub cover.An understory cover threshold for tree growth was not observed.Due to the overriding effect of shrub competition,controlling herbaceous species had little effect on plantation growth even though it benefited tree seedling survival.A long-term value of N-fixing shrubs at these sites,if there is one,must be balanced by successful plantation establishment and rapid early growth.

Landscape Pattern and Tourism Aesthetic Value of Shrubs in the Mountainous Area of West Sichuan, China

Shrubs is one of the major types of natural terrestrial ecosystems.China is one of the largest shrubs distribution countries in the world,and the mountainous area of west Sichuan in the southwest region is one of the key distribution sections.Nevertheless,the basic data of shrubs has long been unexplored.This study was designed to document and map the landscape pattern of the shrubs by using land use data with the help of field survey data and well-established landscape metrics.The study area was classifi ed into 7 fi rst-class land cover types and 19 second-class shrubs types.The results showed that grassland,forest,and shrubs landscapes are 3 dominant types.Shrubs landscape showed high quality,fragmentation,aggregation and diversity,richness of resources.Based on these,this paper also presented an outspread discussion on the tourism aesthetic value of shrubs.The conclusion is that the aesthetic value and tourism resources value of shrubs are both considerable,especially for Rhododendron L.shrubs.And ecotourism is suitable for shrubs’exploration and environmental education.Analyzing distribution of shrubs landscape and discussing its tourism aesthetic value can provide a reference and idea for future research.