The Mechanical Properties Of Plant In Resisting Soil Erosion In The Hilly-gullied Loess Plateau

Vegetation plays an important role in soil erosion resistance, and its effectiveness inresistant soil erosion is related to the mechanical properties of plant. So, in the Yanhe riverbasin, we take the plant in different erosion environments of hilly and gully slope (sunnygully slope, sunny hilly slope, hilltop, shady hilly slope, shady gully slope) in the differentvegetation belts as the research object, make investigations on plant roots parameters (rootbiomass, specific root length, root length density) and root tensile resistance, plant stemdensity and its mechanical indicators (elastic modulus, bending strength and bendingstiffness), and plant intercept ability of sediment and litter, then discuss the plant mechanicalcharacteristics in resistanting soil erosion. Basically have the following results:(1) In the same erosion environment of hilly and gully slope, root biomass, the specificroot length and root length density are bigger than the other two belts in forest belt, and theroot parameters in three vegetation belts have different changes except the hilltop. In differenterosion environments of hilly and gully slope, the specific root length changes the same as thetrend of root biomass.Except forest belt, root biomass in the other two vegetation belts bothare in sunny slope greater than the shady slope, and root length density have different changes.In different plant communities, root biomass changes with vegetation coverage and thecommunity composition and its ratio; the specific root length and root length density arebigger in the community with Bothriochloa ischcemum, Stipa bungeana, Carex lanceolatathan the others. In different soil layer, root biomass and specific root length are highlyvariable in different soil layer of each vegetation belt, and the root length density in3vegetation belts of the erosion environment are all in0-10cm soil layer significantly greaterthan10-20cm soil layer. And in the same soil layer, the root proportionof <1mm is thelargest in the root parameters of each diameter class.(2) Single root tensile experiments indicate that: the relationship between root tensileresistance and root diameter accords with exponential function significantly. In the differenterosion environments, there is no significant difference between root tensile resistant in thesame species. Order of the tensile resistance in species is Lespedeza davurica＞Artemisiagmelinii, Artemisia giraldii, Artemisia scoparia＞Heteropappus altaicus＞Artemisia mongolica＞Stipa bungeana＞Carex lanceolata, Cleistogenes squarrosa, Bothriochloaischaemum＞Leymus scalinus. Root tensile resistance of species inthe same familiy have nosignificant difference, but in different famlies have reached significant difference (P <0.05).(3) In different erosion environments, the order of plant stem density is gramineousplants> compositae plants> leguminous plants. And in the same erosion environment ofdifferent vegetation belts, there has otherness among species in the same family. It show thatCarex lanceolata in forest belt, Bothriochloa ischaemum in forest steppe belt, Stipa bungeanain steppe belt and Artemisia gmelinii, Artemisia giraldii and Lespedeza davurica in each belthave larger plant stem density than other species in the same family.(4) In the same erosion environment of hilly and gully slope, the overall trend of thestem elastic modulus, bending strength and bending stiffness about the same species is foreststeppe belt＞steppe belt＞forest belt, but has no significant difference. As for the samespecies, its stem mechanical index had no significant difference in different erosionenvironments (P>0.05), but it varies in species. The order of plant stem mechanics index ofthese species is Lespedeza davurica＞Artemisia gmelinii, Artemisia giraldii, Artemisiascoparia＞Heteropappus altaicus＞Artemisia mongolica, and the mechanical indexes ofLespedeza davurica has significant difference with other five species (P <0.05), this indicatethat Lespedeza davurica stalks have the largest capacity in bear external force. But in theactual cases, we should combine with plant stem density factors to comprehensive estimatethe erosion resistance ability of plant.(5) With the influence of vegetation coverage, plant stem density and plant community,litter interception ability of plant is different in each erosion environment. No matter howchanges in vegetation coverage and plant stem density, the overall trend of litter interceptionamount is characterized by forest belt> steppe belt> forest steppe belt, and also (excepthilltop) have reached significant difference (P <0.05) among the5erosion environments inforest belt, while the other two belts did not reach significant difference.(6) Mound height of different species is in a growing trend with the increase of slopegradient, there has significant correlation (P <0.05) between the mound height and slopegradient within the gamineous and compositae plants. Among the gamineous plants,Cleistogenes chinensis has larger mound height and volume under different slope, and Stipabungeana has minimal. In the compositae plants, the area and volume of mound of Artemisiagmelinii and Artemisia giraldii is largest, but its mound height is small. The plants roundnessindex showed a negative correlation with mound area, height and volume, and there have apositive correlation relationship among plant length, mound height, mound area, mound volume and tiller or stem numbers, but have different significance. The tiller number ofgramineous plants was significantly positively related to mound height, mound area andmound volume, and the non-gramineous plants has no significant correlation. There is nosignificant correlation among the height, area and volume of mound about each species.