REGULAR ARTICLE

Effects of artificial grassland establishment on soil nutrientsand carbon properties in a black-soil-type degradedgrassland

Gao-Lin Wu & Zhen-Heng Liu & Lei Zhang &

Tian-Ming Hu & Ji-Min Chen

Received: 12 October 2009 /Accepted: 22 March 2010 /Published online: 23 April 2010# Springer Science+Business Media B.V. 2010

Abstract Disturbance and management approachescan contribute significantly to restoration of degradedgrassland ecosystems. This study has examined there-establishment of artificial grassland to renewextremely degraded black-soils in an alpine area ofthe Qinghai-Tibetan Plateau, in China. We evaluatedthis method for which grassland ecosystem responses

to this restoration approach are needed. Here, weevaluated the response of aboveground plant commu-nities and belowground soil nutrient and soil carbonstorage to the establishment of artificial grassland ingrasslands on black-soils in the eastern Qinghai-Tibetan Plateau. Three grasslands sites were selected:a degraded grassland on an original black-soil, and 3-and 6-year-old Elymus nutans artificial grasslands.Artificial grassland establishment significantly im-proved aboveground biomass, but also significantlydecreased species richness, diversity and evenness forblack-soil-type degraded grassland. Artificial grass-land establishment resulted in significantly improvedsoil total nitrogen and phosphorus, and decreased soilorganic matter, available nitrogen, and phosphorus,especially in the depth of 20–30 cm soil layer.Although artificial grassland establishment signifi-cantly improved soil organic carbon in the topsoil(0–10 cm), it decreased at depths of 10–20 and 20–30 cm. Six-year artificial grassland significantlyincreased soil carbon storage compared with black-soil-type degraded grasslands. Accordingly, artificialgrassland can be used as effective restoration andrehabilitation approach to improve productivity andregulate community and soil properties in black-soil-type degraded grasslands. Our results suggest thatecosystem functions such as production of above-ground biomass, the provision of soil surface cover,and nutrient accumulation may be provided byartificial grassland. However, more time is needed

Plant Soil (2010) 333:469–479DOI 10.1007/s11104-010-0363-9

Responsible Editor: Tibor Kalapos.

G.-L. Wu : L. Zhang : J.-M. ChenState Key Laboratory of Soil Erosion and Dryland Farmingon the Loess Plateau of Northwest A&F University,Yangling 712100 Shaanxi, People’s Republic of China

G.-L. Wu : T.-M. Hu (*) : J.-M. Chen (*)College of Animal Science & Technologyof Northwest A&F University,Yangling, Shaanxi 712100, People’s Republic of Chinae-mail: hutianming@126.come-mail: gyzcjm@ms.iswc.ac.cn

Z.-H. LiuMaqu Alpine Grassland Workstation,Maqu, Gansu 747300, People’s Republic of China

G.-L. Wu (*) : J.-M. ChenState Key Laboratory of Soil Erosion and Dryland Farmingon the Loess Plateau, Institute of Soil and WaterConservation of CAS&MWR,No. 26 Xinong Road,Yangling, Shaanxi 712100, People’s Republic of Chinae-mail: gaolinwu@gmail.com

for plant diversity and soil carbon storage functions torecover fully from degradation.

Keywords Alpine grassland . Artificial grasslandestablishment . Community . Soil carbon storage . Soilproperties . Succession

Introduction

Restoration of degraded grassland ecosystems hasbecome an increasingly important research subject,not at least due to increasing problems associatedwith ecosystem functioning, e.g., maintenance ofbiodiversity and carbon sequestration (Tiessen et al.1994; Neill et al. 1997). In China, 90% of grasslands(3.99 billion ha) are degraded (Ren et al. 2007a), andin recent years, alpine grasslands on the TibetanPlateau have also suffered from quite severe degra-dation. This has resulted in both a decline in herbageyields and ecological quality of the environment,with severe pest damage, species loss, desertifica-tion, wetland degradation, soil erosion, etc. (Hao2008). Globally, grassland ecosystems play impor-tant roles both as sinks and sources of atmosphericcarbon with soils being the largest source ofuncertainty in the terrestrial carbon balance (Piao etal. 2009). Grassland ecosystems can influence globalenvironmental change through their strong potentialfor carbon and nitrogen sequestration (Wright et al.2004). An important component of “disturbance”,restoration and rehabilitation modes of naturaldegraded grassland ecosystems has a potential toalter not only the aboveground community, but alsobelowground soil properties and the soil carbon-sinkfunction (Lal 2004; Wright et al. 2004; Piao et al.2009). Wang et al. (2005) found that artificialgrassland establishment followed by fencing couldsignificantly enhance soil C and N concentrations inalpine grassland. External disturbance can not onlyaccelerate succession of vegetation, but also renewsoil nutrient cycling and carbon storage (Schippersand Joenje 2002). Accordingly, to counteract degra-dation, approaches, such as fencing, reseeding and/or the use of fertilizers, control of rats, wereconducted to accelerate the restoration and rehabil-itation process of degraded grassland ecosystems(Akiyama and Kawamura 2007; Choi 2007; Wu etal. 2009).

However, none of these restoration and rehabilita-tion approaches have shown significant positiveeffects on degraded grassland black-soils in alpineareas of the Qinghai-Tibetan Plateau (Shang and Long2007). This is largely a consequence of the specialand extremely degraded conditions of these soils(Shang and Long 2007; Shang et al. 2008). Favorablenatural restoration approaches have been found to bedifficult to establish. Black-soil-type degraded grass-lands, which range from 10 to 15 cm in depth, occurafter complete removal of surface layer by intensivegrazing and activities of rodents leaving the sub-soiluncovered (Shang and Long 2007). In the cold seasonespecially, it is not covered with vegetation, whichleaves the soil bare and prone to erosion, while in thewarm season grasslands are covered by toxic weeds,inedible for livestock (Shang and Long 2007). This notonly leads to ecological problems, but also greatlyreduces the productivity of those grasslands. Thecommon restoration and rehabilitation approach to thisdegradation is an establishment of artificial and semi-artificial grassland (Shang and Long 2007; Shang et al.2008). Although more recent studies focus on effectsof different restoration and management on plantspecies composition and diversity, soil properties andsoil carbon and nitrogen dynamics (Smith et al. 2000;Burke 2001; Wright et al. 2004; Shang et al. 2008; Wuet al. 2009), relatively little information is available onartificial grassland establishment, which may be seenas a stronger disturbance on natural grassland, affectingsoil properties and the soil carbon-sink function in ablack-soil-type degraded grassland ecosystem of theQinghai-Tibetan Plateau.

The present study, within the Maqu-pilot-project“Returning to Grassland by Excluding Grazing”,analyzed effects of artificial grassland establishmenton aboveground community properties, and below-ground soil nutrient properties and soil carbon storagewere examined. Elymus nutans-grassland was themost representative artificially established grasslandin the whole Qinghai-Tibetan Plateau. In this study,we selected a black-soil-type degraded grassland anda 3-year and 6-year artificial Elymus nutans-grass-land. We hypothesized that establishment of artificialgrassland increases soil carbon storage. This study isrelevant to the restoration and rehabilitation of black-soil-type degraded grassland, and is broadly relevantto studies of plant community and soils in response toecosystem disturbance.

470 Plant Soil (2010) 333:469–479

Materials and methods

Study sites

This experiment was conducted in alpine meadow at3,500 m a.s.l. at Manrima (33°42′21″N, 102°07′02″E) in Gansu Province, PR China, which is located atthe eastern Qinghai-Tibetan Plateau. The meanannual temperature is 1.2°C, ranging from −10°Cin January to 11.7°C in July, with about 270 frostdays. The mean annual precipitation is 620 mm,with a main rain period during a short, cool summer.The annual cloud-free solar radiation was about2,580 h (Wu et al. 2009). The vegetation is typicalalpine meadow and is dominated by clonal grasses(Festuca ovina, Poa poophagorum, Roegnerianutans, Agrostis sp., Kobresia sp., grasses andsedges) and forbs (Saussurea sp., Asteraceae andAnemone rivularis, Ranunculaceae).

In this study, we selected a highly degraded black-soil-type grassland, in the alpine area of the Qinghai-Tibetan Plateau, which was dominated by Potentillaanserina L. and Helenia corniculata (L.) Cornaz andsome other subordinate species.

Experimental design

In this study, we compared three grasslands: a black-soil-type degraded, and 3-year and 6-year artificial

establishment of Elymus nutans. Each grassland plotwas about 0.5 ha and comprised five sampling plots(30 m×30 m) (Fig. 1). Plots were separated by fenceswith a partition section of 20 m. Artificial grasslandplots were excluded from livestock grazing withfencing during the plant growth seasons from Aprilto October, and slight grazing was provided forTibetan sheep and yaks (1.3 individuals per hectarewith a ratio sheep vs yaks of 2:1) only during the hay-stage in winter. In each of the five sampling plots ofthe three grassland types, we established five diagonalsampling quadrats (1 m×1 m) (Fig. 1).

Vegetation sampling

All plant species composition samples were takenfrom five quadrats from every sampling plot, whenpeak biomass was reached (early September 2008).The experiment contained a total of 75 quadrats. Thedensity, frequency and biomass of each species ineach quadrat were counted separately. Total above-ground biomass, species richness, and abundance ofeach quadrat in three grassland types were measured.Every shoot was counted for each species, clippedand put in marked paper bags per species per quadrat.We determined the total dry biomass in every quadratby weighing the plants after drying at 80°C for 48 hto a constant weight. The mean number of shoots insampling plots represented the abundance of the

Fig. 1 Field experiment setup and sampling arrangement.Three grassland types were contained (black-soil-type degradedgrassland CK, 3-year artificial grassland 3-y AG, and 6-yearartificial grassland 6-y AG) and five sampling plots (30 m×

30 m) were selected , respectively, in each type, and fivequadrats (1 m×1 m) were determined for community investi-gation and soil sampling collection in each sampling plot. Atotal of 75 quadrats were included in this study

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community. Shannon-Wiener diversity index (H) andEvenness index (E) of the three grassland typescommunities were calculated as:

Richness index (R): R=S

Shannon-Wiener diversity index (H):

H ¼ −Ps

i¼1Pi lnPiÞ;ð

Evenness index (E): E ¼ Hln S ;

where S is the total species numbers of meadowcommunity, H is the Shannon-Wiener diversity indexand Pi is the abundance proportion of i species.

Soil sampling

We collected five soil samples at different soil depths(from 0∼10 cm, 10∼20 cm and 20∼30 cm respective-ly) using a bucket auger from each quadrat and everysampling plot in the three grassland types in adiagonal pattern. Soil samples at the same depths ineach sampling quadrat were mixed. Then, 25 mixedsoil samples from each soil depth in each plot wereused to analyze soil properties and soil carbonstorage. All soil samples were air-dried and thenpassed through a 0.14-mm sieve. Soil pH wasdetermined using a soil–water ratio of 1:5. Soilorganic matter was measured using the Walkley-Black acid digestion method by K2Cr2O7 (SoilScience Society of China 1983). Soil total nitrogen,available nitrogen, total phosphorus and availablephosphorus were measured by the methods of Millerand Keeney (1982) in the laboratory. The organiccarbon content in the soil samples were determined bywet oxidation with potassium dichromate (K2Cr2O7)and dry combustion with a carbon analyzer using aMebius method by the Walkley-Black acid digestion(Nelson and Sommers 1982). We calculated the totalsoil organic carbon storage density (TSOC, g cm−2)by the method of He et al. (2008) on a ground areabasis up to a 30-cm depth as follows:

TSOC ¼�

XDi � Pi � OMi � S

where Di, Pi, OMi, and S represent, respectively, thesoil thickness (cm), bulk density (g cm−3), organiccarbon concentration (%), and cross-sectional area(cm-2) of the ith layer; i=1, 2, and 3.

The content of each nutrient trait calculated by theproportions of soil organic matter, total nitrogen,available nitrogen, total phosphorus and availablephosphorus account for air-dry weight of soil samplings.

Data analysis

Data is expressed as mean±standard error of mean.The soil sample data for the 0–10-cm, 10–20-cm and20–30-cm soil layers were used to analyze the soilproperties and soil organic carbon storage potentialsof the three grassland types. To assess the effects ofestablishment time of artificial grassland on soil depthand their interaction on soil properties and soilorganic carbon, an LSD tests for significance (P<0.05) of between-subjects effects were conducted withtwo-way ANOVA of General Linear Model (GLM)for soil properties and soil organic carbon amongthree grassland types and three soil depths. To assessthe effect of establishment time of artificial grasslandon community properties and soil carbon storage,one-way ANOVA analyses were conducted forvegetation community characteristics and soil carbonstorage among three grassland types. All statisticalanalyses were performed using the software programSPSS, ver. 13.0 (SPSS, Chicago, IL, USA).

Results

Response of plant community and soil nutrientproperties

Artificial grassland establishment significantly in-creased aboveground biomass, but also significantlydecreased species richness, diversity and evenness forblack-soil-type degraded grassland (Fig. 2; Table 1).As for soil nutrient properties among black-soil-typegrassland, 3-year and 6-year artificial grasslands,there were significant effects of grassland type, soildepth and their interaction on soil pH, soil organicmatter, soil total nitrogen, soil available nitrogen, soiltotal phosphorus, and soil available phosphorus in thisstudy (Table 1). Artificial grassland had a lower soilpH, soil available phosphorus and higher soil totalnitrogen than black-soil-type grassland throughoutdifferent soil depths in this study (Fig. 3a, d, f). Forsoil organic matter and soil total nitrogen, 3-year and6-year artificial grasslands were both significantly

472 Plant Soil (2010) 333:469–479

greater than black-soil-type grassland at depths of 0–10 and 10–20 cm, but opposite results were shown ata depth of 20–30 cm (Fig. 3b,c). The soil availablenitrogen at depths of 0–10 and 20–30 cm in the 3-yearand 6-year artificial grasslands were lower than thosefor black-soil-type grassland, but increased at depthsof 10–20 cm (Fig. 3e).

In two different growth periods, the 6-year artifi-cial grassland had higher pH, total soil nitrogen andphosphorus throughout the soil profile. The organicmatter concentrations were higher in the 0–10 and10–20 cm layers, but lower at 20–30 cm than the 3-year artificial grassland. Additionally, 6-year artificialgrassland had lower soil available phosphorusthroughout the profile and lower soil available

nitrogen at depths of 0–10 and 10–20 cm, but greaterat 20–30 cm than the 3-year artificial grassland(Fig. 3).

Response of soil carbon properties

There was a significant effect of grassland type, soildepth and their interaction on soil organic carbon(Table 1). Three-year and 6-year artificial grasslandsboth showed a significant increase in soil organiccarbon content at a depth of 0–10 cm, but there werelower concentrations between 10–20 and 20–30 cm.Meanwhile, 6-year artificial grassland had a highersoil organic carbon content than the 3-year artificialgrassland (Fig. 4a).

Fig. 2 Effect of artificial grassland planting on abovegroundbiomass (a), species richness index (b), Shannon-Wienerdiversity index (c) and Evenness index (d) of grasslandcommunity. Values (±SE) are means of 25 quadrates for

black-soil-type degraded grassland (CK), 3-year artificialgrassland (3-y AG) and 6-year artificial grassland (6-y AG).Different letters indicate significant differences at P<0·05

Plant Soil (2010) 333:469–479 473

For soil carbon storage, the three grassland typesshowed significant differences (Table 1). The amountof C in 6-year artificial grassland was greater than thatin black-soil-type degraded grassland, which was inturn greater than that in 3-year artificial grassland(Fig. 4b).

Correlation analyses showed that soil carbonstorage was significant positively related to richnessindex (R=0.660, P<0.01). There was also a non-significant positive correlation between soil carbonstorage and the diversity index (R=0.420, P>0.05).Meanwhile, soil organic carbon was significantlypositively related to diversity index (R=0.440, P<0.01) and richness index (R=0.323, P<0.05), but wassignificantly negatively related to aboveground bio-mass (R=-0.322, P<0.05; Table 2).

Discussion

Rebuilding of artificial grassland of Elymus nutansis central for restoration of vegetation productivityin black-soil-type degraded grassland. Six-yearartificial grassland showed significantly less above-ground biomass than 3-year artificial grassland. Itwas consistent with the results of Ma et al. (2002)and Kanda et al. (2002), who have demonstratedthat artificial grassland establishment in black-soillands can slow the pace of grassland degradation

and, concomitantly, can produce more feed forlivestock.

Establishment of artificial grassland significantlyreduced plant diversity and evenness of black-soil-type degraded grassland at 3 years. But, at 6 years,plant diversity and evenness had rebounded andbegan increasing relative to that at 3 years. Thisresult was consistent with a study in ‘black-soil land’grassland in the headwaters of the Yangtze and theYellow Rivers of the Qinghai-Tibetan Plateau byShang et al. (2008). They had found that speciesrichness of forbs decreased but grass species in-creased in re-established artificial grassland more thanin black-soil-type degraded grassland. Meanwhile,reseeding grasses could significantly change the plantcomposition of black-soil-type degraded grassland inthe short-term, and increase the proportion of thefunctional group of grasses (Shang et al. 2008). Thisis also related to a stronger growth and competitiveadvantage shown by Elymus nutans. Previous re-search has reported that palatable grasses have greatercompetitive ability and show a greater increase inabundance in grasslands than unpalatable grasseswhere livestock are excluded (Distel and Boo 1996;Moretto and Distel 1997; Gallego et al. 2004).Furthermore, palatable grasses which had higherproductivity and quality can lock abundant nutrientswithin their tissues from the soil (Moretto and Distel1997; Harris et al. 2007). Additionally, the Elymus

Table 1 Results of ANOVA tests for the effects of grassland type (GT) on aboveground biomass, species richness, diversity, evennessand soil carbon storage over the depth of 0∼30 cm, and effects of grassland type (GT), soil depth (SD), and their interaction (GT×SD)on pH value, soil organic matter (SOM), total nitrogen, available nitrogen, total phosphorus, available phosphorus and soil organiccarbon

df F P F P F P F P

Sources Aboveground biomass Richness index Diversity index Evenness index

GT 2 16.47 <0·001 1.45 <0·01 1.68 <0·01 12.07 <0·001

Sources pH SOM Total nitrogen Available nitrogen

GT 2 22.69 <0·001 5.07 <0·001 3.13 <0·001 4.33 <0·001

SD 2 3.47 <0·01 7.41 <0·001 3.63 <0·001 3.72 <0·001

GT×SD 4 5.15 <0·001 3.02 <0·001 2.51 <0·001 2.42 <0·001

Sources Total phosphorus Available phosphorus Soil organic carbon Soil carbon storage

GT 2 3.925 <0·01 5.16 <0·01 7.01 <0·001 6.17 <0·001

SD 2 2.082 <0·001 4.28 <0·001 6.74 <0·001

GT×SD 4 1.463 <0·01 2.81 <0·001 3.464 <0·001

All values show significance at P<0·05

df Degrees of freedom

Table 1 Results of ANOVA tests for the effects of grasslandtype (GT) on aboveground biomass, species richness, diversity,evenness and soil carbon storage over the depth of 0∼30 cm, andeffects of grassland type (GT), soil depth (SD), and their

interaction (GT×SD) on pH value, soil organic matter (SOM),total nitrogen, available nitrogen, total phosphorus, availablephosphorus and soil organic carbon

474 Plant Soil (2010) 333:469–479

Fig. 3 Changes (mean±SE) in soil pH value (a), soil organicmatter (b), soil total nitrogen (c), soil total phosphorus (d), soilavailable nitrogen (e) and soil available phosphorus (f) under

three soil depths for three grassland types. Significant differ-ences among three grassland types and soil depths are indicatedin Table 1

Plant Soil (2010) 333:469–479 475

nutans population is taller than other native speciesand produced shading effects on growth and recruit-ment of some other species. Some species with lowercompetitive ability reduce their density or disappearin plant communities because of competition for lightresources (Grime 1998) or nutrient availability (Vander Wal et al. 2004). So, plant diversity loss in high-productivity artificial grassland of Elymus nutans mayresult from greater competition for canopy resources

(i.e. light and soil nutrient availability) (Grime 1979;Huston 1994). But, with the passage of time, someaboveground biomass was transferred by animalforaging. It resulted in nutrient outflow from theplant–soil system and a decrease in soil nutrientavailability. The growth and competitive advantage ofElymus nutans population performed declined as aconsequence and other species took this opportunityto invade the community. The rebuilding of artificialgrassland in black-soil-type degraded grassland canbe considered as an effective restoration and rehabil-itation approach to improve productivity and regulatecommunity structure. Succession and maintenance ofplant diversity needs a long time. Additionally,reasonable grazing or mowing may be integrated intothis restoration process. Further studies are required todetermine the point where artificial grasslands keeprelatively higher productivity and plant diversity atthe same time.

Our study found that rehabilitation by rebuildingartificial grassland in black-soil-type degraded grass-land generally had significantly favorable effects onsoil nutrient properties and soil carbon storage.Nutrient availability of topsoil significantly increasedand soil carbon also showed a significant increase in6-year artificial grassland. This result may reflect apositive response for black-soil-type degraded grass-land to establishment of artificial grassland. It was

Table 2 Pearson’s correlation coefficients (R) among soilcarbon storage over the depth of 0∼30 cm, soil organic carbon,diversity index, richness index and aboveground biomass ofthree type grasslands (n=45)

Pearson’scorrelationcoefficients (R)

Soilorganiccarbon

Diversityindex

Richnessindex

Abovegroundbiomass

Soil carbonstorage

0.404 ns 0.420 ns 0.660** −0.464 ns

Soil organiccarbon

0.440** 0.323* −0.322*

Diversity index 0.755** −0.806**Richness index −0.713**

ns Not significant

*Correlation significant at the 0.05 level

**Correlation significant at the 0.01 level (2-tailed)

Fig. 4 Changes (mean±SE) in soil organic carbon (a) underthree soil depths for three grassland types and soil carbonstorage (b) over the depth of 0∼30 cm in three grassland types.Significant differences of soil organic carbon among three

grassland types and soil depths are indicated in Table 1.Different letters indicate significant differences at P<0·05 insoil carbon storage among three grassland types

476 Plant Soil (2010) 333:469–479

consistent with the proposal of Ren et al. (2007b) thatnutrient cycling of degraded ecosystem recoveredvery slowly by natural restoration and artificialplantation may be necessary to accelerate the restora-tion process. But, after a period of time, much of thelitter produced by Elymus nutans population wasdecomposed and translated into nutrient and carbonreserves in the topsoil. So, soil nutrient properties allpresented a significant increase for 3-year and 6-yearartificial grassland in topsoil (0–10 and 10–20 cm),except available nitrogen and phosphorus which canbe used directly by plants. Secondly, Elymus nutanspopulation as palatable grasses had higher productiv-ity and quality and locked the abundant nutrientswithin their tissues (Moretto and Distel 1997; Harriset al. 2007).

Our study has shown that the soil C storagedecreased substantially with grassland degradation(He et al. 2008). We also found that artificialgrassland establishment, as an improved managementpractice that includes fertilization, promotion ofnative vegetation, and sowing of legumes, canincrease soil C content and concentration (Conant etal. 2001). In addition, our results showed that theaboveground biomass was greater in 3-year artificialgrassland, but carbon storage was higher in 6-yearartificial grassland. It may be resulted from muchcarbon biomass was locked in plant tissues in the first3 years, which was performed as higher abovegroundbiomass, but the decomposition of its leaf and stemlitter also returned much carbon biomass to soil afterseveral years. There was more carbon storage in 6-year artificial grassland than in 3-year artificialgrassland. Our study suggests that practice of artificialgrassland establishment is a good approach to controlblack-soil-type degraded grassland to increase soilfertility and reduce grazing pressure; additionally, it isa valuable mechanism of sequestering C in the topsoil of black-soil-type degraded grasslands, similar tograzing exclusion (He et al. 2008)

Additionally, farming practices as a soil distur-bance approach (ploughing) can decrease soil bulkdensity and improve soil respiration. Grassland whichpreviously adapted to a high disturbance regimeusually had lower soil carbon storage than thatadapted to a low disturbance level (Klumpp et al.2007). In addition, artificial plantation of Elymusnutans grassland decreased soil pH and the acidiccondition was favorable for litter decomposition. Our

result showed that soil carbon storage was significantpositively related to richness index. It suggested thatsoil carbon storage may be related to speciesdiversity in grassland community. Disturbanceapproaches may affect soil nutrient and carbonstorage both directly (e.g., defoliation) and indirectlyby altering plant community structure in grassland(Klumpp et al. 2007).

Our results suggest that part of the ecosystemfunctions such as aboveground biomass, coverage andsoil nutrients recovered after rebuilding artificialgrasslands. But, more time is needed for recovery ofplant diversity and soil carbon storage functions.There is a pressing need to understand the short-term and long-term effects of rebuilding artificialgrassland on degraded grassland ecosystems to reneweffectively its yielding and ecosystem functions, andto keep its positive succession both in abovegroundand belowground properties. Therefore, from arestoration perspective, Elymus nutans artificial grass-land can be used an effective restoration approach inblack-soil-type degraded grassland by grassland man-agers because it had significantly positive effects onboth aboveground and belowground restoration ofblack-soil-type degraded grassland.

This research also lends support for increasing ourfocus on grassland restoration to affect plant commu-nity succession. All the above-mentioned resultsindicated that artificial grassland establishment as asevere disturbance brought on two phases of succes-sion for vegetation and soil properties of black-soil-type degraded grasslands. The first-phase successionis the initial stage of plant community restorationfollowing a severe disturbance that is accompanied byhigher aboveground biomass, lower species diversityand depressed soil nutrient and soil carbon storage.Elymus nutans artificial grassland, as pioneer specieswhich lead to a new community succession, estab-lished themselves rapidly during the preliminaryyears, providing cover and minimizing soil bare.Only some species that can tolerate a wide varietyof conditions including the scarcity of light andnutrients were involved in first-phase succession.Second-phase succession begins either after the plantcommunity of the first-phase successional phase hasbecome established or following other mild distur-bance which leaves some of the pre-disturbancehabitat intact. Plants involved in second-phase suc-cession are generally longer lived and require some-

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what more developed soil conditions to survive. Theyare often fast-growing forbs and weeds and serve tofurther stabilize the community and amend the soilnutrients and soil carbon storage. Managers maytherefore include grazing or mowing utilization asan opposite disturbance factor to artificial grasslandestablishment. Because moderate grazing can favorvegetation transition from communities dominated byhighly competitive sown species to more diversespecies communities (Moreno-de las Heras et al.2008; Wu et al. 2009), it can reduce negative effectsof artificial grassland on species diversity coexistenceand soil nutrient consumption.

Acknowledgements We thank Prof. Eugene David UNGARand Prof. Simon Thirgood and two anonymous referees fortheir valuable comments on this manuscript and Prof. Bob Reesfor supporting in English writing revision and thank colleaguesof Maqu Grassland Station for valuable assistance with fieldwork. The study was supported by Projects of Natural ScienceFoundation of China (NSFC30900177), State Key Laboratoryof Soil Erosion and Dryland Farming on the Loess Plateau(10502-Q5, 10502-Z8), “Hundred Talents Program” to Shi ZHof CAS, and frontier research fund of NWSUAF (Z111020903)China and Special Research Funds for Public Service of Ministryof Agriculture China (200903060).

References

Akiyama T, Kawamura K (2007) Grassland degradation inChina: methods of monitoring, management and restora-tion. Grassland Sci 53:1–17

Burke A (2001) Determining landscape function and ecosystemdynamics: contribution to ecological restoration in thesouthern Namib Desert. Ambio 30:29–36

Choi YD (2007) Restoration ecology to the future: a call fornew paradigm. Restoration Ecol 15:351–353

Conant RT, Paustian K, Elliott ET (2001) Grassland manage-ment and conversion into grassland: effects on soil carbon.Ecol Appl 11:343–355

Distel RA, Boo RM (1996) Vegetation states and transitions intemperate semiarid rangelands of Argentina. In: West NE(ed), Rangelands in a sustainable biosphere. Society forRange Management, pp.117–118

Gallego L, Distel RA, Camina R, Rodrı’guez Iglesias RM (2004)Soil phytoliths as evidence for species replacement in grazedrangelands of central Argentina. Ecography 27:725–732

Grime JP (1979) Plant strategies and vegetation processes.Wiley, Chichester

Grime JP (1998) Benefits of plant diversity to ecosystems:immediate, filter and founder effects. J Ecol 86:902–910

Hao X (2008) A green fervor sweeps the Qinghai-TibetanPlateau. Science 321:633–635

Harris WN, Moretto AS, Distel RA, Boutton TW, Boo RM(2007) Fire and grazing in grasslands of the Argentine

Caldenal: effects on plant and soil carbon and nitrogen.Acta Oecol 32:207–214

He NP, Yu Q, Wu L, Wang YS, Han XG (2008) Carbon andnitrogen store and storage potential as affected by land-usein a Leymus chinensis grassland of northern China. SoilBiol Biochem 40:2952–2959

Huston MA (1994) Biological diversity, the coexistence ofspecies on changing landscapes. Cambridge UniversityPress, New York

Kanda K, Miranda CHB, Macedo MCM (2002) Carbon andnitrogen mineralization in soils under agro-pastoral sys-tems in subtropical central Brazil. Soil Sci Plant Nutr48:179–184

Klumpp K, Soussanaa JF, Falcimagnea R (2007) Effects of pastand current disturbance on carbon cycling in grasslandmesocosms. Agric Ecosyst and Environ 121:59–73

Lal R (2004) Soil carbon sequestration impacts on globalclimate change and food security. Sciences 304:1623–1627

Ma YS, Lang BN, Li QY, Shi JJ, Dong QM (2002) Study onrehabilitating and rebuilding technologies for degeneratedalpine meadow in the Changjiang and Yellow river sourceregion. Pratacultural Sci 19:1–4 (in Chinese with Englishabstract)

Miller RH, Keeney DR (1982) Methods of soil analysis, 2ndedn. American Society of Agronomy, Soil Science Societyof America, Madison

Moreno-de las Heras M, Nicolau JM, Espigares T (2008)Vegetation succession in reclaimed coal-mining slopes in aMediterranean-dry environment. Ecol Engine 34:168–178

Moretto AS, Distel RA (1997) Competitive interactionsbetween palatable and unpalatable grasses native to atemperate semiarid grassland of Argentina. Plant Ecol130:155–161

Neill C, Melillo JM, Steudler PA, Cerri CC, Moraes JFL,Piccolo MC, Brito M (1997) Soil carbon and nitrogenstocks following forest clearing for pasture in thesouthwestern Brazilian Amazon. Ecol Appl 7:1216–1225

Nelson DW, Sommers LE (1982) Total carbon, organic carbon,and organic matter. In: Page AL, Miller RH, Keeney DR(eds) Methods of soil analysis. American Society ofAgronomy and Soil Science Society of American,Madison, pp 1–129

Piao SL, Fang JY, Ciais P, Peylin P, Huang Y, Sitch S, Wang T(2009) The carbon balance of terrestrial ecosystems inChina. Nature 458:1009–1013

Ren H, Du WB, Wang J, Yu ZY, Guo QF (2007a) Naturalrestoration of degraded rangeland ecosystem in Heshanhilly land. Acta Ecol Sin 27:3593–3600

Ren H, Shen WJ, Lu HF, Wen XY, Jian SG (2007b) Degradedecosystems in China: status, causes, and restorationefforts. Landscape Ecol Engine 3:1–3

Schippers P, Joenje W (2002) Modelling the effect of fertiliser,mowing, disturbance and width on the biodiversity ofplant communities of field boundaries. Agric EcosystEnviron 93:351–365

Shang ZH, Long RJ (2007) Formation causes and recovery ofthe “Black Soil Type” degraded alpine grassland inQinghai-Tibetan Plateau. Frontiers Agric China 1:197–202

Shang ZH, Ma YS, Long RJ, Ding LM (2008) Effect offencing, artificial seeding and abandonment on vegetation

478 Plant Soil (2010) 333:469–479

composition and dynamics of ‘black soil land’ in theheadwaters of the Yangtze and the Yellow Rivers of theQinghai-Tibetan plateau. Land Degrad Develop 19:554–563

Smith RS, Shiel RS, Millward D, Corkhill P (2000) Theinteractive effects of management on the productivity andplant community structure of an upland meadow: an 8-year field trial. J Appl Ecol 37:1029–1043

Soil Science Society of China, Agriculture Chemistry Council(1983) General analysis methods of soil agriculturechemistry. Science Press, Beijing

Tiessen H, Cuevas E, Chacon P (1994) The role of soilorganic matter in sustaining soil fertility. Nature 371:783–785

Van der Wal R, Bardgett RD, Harrison KA, Stien A (2004)Vertebrate herbivores and ecosystem control: cascadingeffects on tundra ecosystems. Ecography 27:242–252

Wang WY, Wang QJ, Wang CT, Shi HL, Li Y, Wang G (2005)The effect of land management on carbon and nitrogenstatus in plants and soil of alpine meadows on the Tibetanplateau. Land Degrad Dev 16:405–415

Wright AL, Hons FM, Rouquette FM Jr (2004) Long-termmanagement impacts on soil carbon and nitrogen dynamicsof grazed bermudagrass pastures. Soil Biol Biochem36:1809–1816

Wu GL, Du GZ, Liu ZH, Thirgood S (2009) Effect of fencingand grazing on a Kobresia-dominated meadow in theQinghai-Tibetan plateau. Plant Soil 319:115–126

Plant Soil (2010) 333:469–479 479