Study On Distribution Patterns And Accumulating Differentiation Behavior Of Mineral Elements In Grassland On The North Bank Of Qinghai Lake

The aims of this study were to get to know the characteristics of mineral elements accumulationdifferentiation and to investigate their distribution pattern in grassland plants on the north bank of Qinghai Lakeand to find out the possible mechanism for their accumulating differentiation and the distribution patternscaused by the succession of grassland ecosystem. It can be defined as a “stress” response to the changes ofenvironmental conditions especially the influence of human activities, such as overgrazing and grasslandenclosure. Four investigation sites were selected based on grassland types and altitude: Hebiantandi (Elymusnutans, alpine meadow), Naren Railway Station (Achnatherum splendens, temperate steppe), Lanniwan (Stipapurpurea, alpine mountaine meadow) and the top of Beishanjiayanggou (Kobresia pygmaea, alpine meadow).The main results are as follows:1）The mineral elements in plants showed four characteristics and two distribution patternsThe mineral elements in grassland plants showed a characteristic spectrum, a vertical-banded spectrum, anegative correlation with plant height and aboveground biomass.The spatial distribution of mineral elements in grassland plants showed a pattern of increasing with alongwith the altitude. In which, the contents of B in degraded grassland in Hebiantandi, Naren Railway Station,Lanniwan and Beishanjiayanggou were14.24mg/kg,15.48mg/kg,16.25mg/kg and19.84mg/kg and the relatedaltitude were3209m,3216m,3291m and3462m respectively；The time distribution pattern of mineralelements in grassland plants was that the content of mineral element decreased with the time of enclosure. Inwhich, the Zn contents of grassland plants in the area of Naren Railway Station were77.01mg/kg and55.46mg/kg after enclosure for5and20years respectively（P＜0.05）.2）Accumulating differentiation behavior of mineral elements in grassland and its kinetic mechanismsThe mineral elements in plants of degraded grassland showed a characteristic of accumulatingdifferentiation. The content of Cu in degraded grassland in Lanniwan, increased from7.275mg/kg to10.48mg/kg (44.1%, P＜0.05) compared with that in enclosed grassland; The content of Pb in enclosed grassland inLanniwan, increased from3.915mg/kg to5.125mg/kg (30.9%, P＜0.05) compared with that in degradedgrassland. In order to find out the possible mechanism for their accumulating differentiation behavior of mineralelements, we proposed a hypothesis to explain the supply-demand balance of mineral element nutrition in thebody of organisms. When the mineral elements supply is relatively insufficient but still in the tolerant range oforganisms, they would fall into a “hungry” state for this element, in order to grow well the organisms wouldadjust their demand for mineral elements timely and begin to store them accumulating in their body. We call thisphenomenon “Starvation Effect”.“Starvation Effect” hypothesis theory has answered the question why mineral elements accumulatedifferently in plants and it can scientifically explain why the correlation between mineral elements content andplant height is negative. It also can be applied to some phenomena such as the spatial distribution patterns of mineral elements in plants.“Starvation Effect” might be the endogenetic force for the mineral elements to accumulate in plants and theclimate change and human activity’s interference as the main exogenetic force.3）Mathematical models of mineral elements in accumulating differentiation in the process of grasslandecosystem succession were established.The mathematical model for mineral elements accumulating differentiation of grassland plants in thedegradation succession: Cde(t)=Cb(1-exp(-αt)) and for that in the enclosed grassland: Cen(t)=Cbexp(-βt).4）Crops cultivation experiments and anti-hypoxic function of high iron contentThe crops cultivation experiments in Dabanshan-mountain, Lajishan-mountain and Xining well verify thespatial distribution pattern and the characteristic of vertical-banded spectrum of mineral elements in plants onthe north blank of Qinghai Lake. Meanwhile，these experiments provide some evidence for the “StarvationEffect” hypothesis.The distribution pattern of iron in barley and carrot in grassland plants on the north bank of Qinghai Lakeand Dabanshan-mountain and Lajishan-mountain area shows that high iron content in plants probably hasanti-hypoxic effect. For example, the content of Fe in the cultured highland barley in Dabanshan-mountain on2009are respectively93.60mg/kg,609.9mg/kg,799.1mg/kg,1360mg/kg and of which the altitude arerespectively2817m,2920m,3562m and3574m (P<0.05). Plants require more iron to increase theirrespiration in order to adapt the high altitude and the low oxygen levels which makes plants “hungry” for iron,under such circumstance, the iron accumulates. So, from this we come to a conclusion that low oxygen level inplateau air makes iron accumulate in plants.5）Characteristics of mineral elements in cultivation grassland on the north bank of Qinghai LakeThe characteristics of mineral elements in cultivation grassland are the same as that in natural grassland onthe north bank of Qinghai Lake. Each cultivation plant has a characteristic spectrum of mineral element andspatial distribution patterns of the content increases with altitude increase. For example, the content of Zn inplants of Elymus nutans in such places as Railway Side Slope, Sanjiaocheng Sheep Stud, West Town arerespectively30.07mg/kg,37.96mg/kg and42.01mg/kg and of which the altitude are respectively3216m,3220m and3287m (P<0.05).The content of mineral element in plants is lower on cultivation grassland than that on natural grassland.We use the “Starvation Effect” theory to explain this phenomenon; the “hungry” state is the endogenetic forcefor the accumulation of the mineral element on natural grassland.6）Cycles of mineral elements and its directive function of in production practiceThrough the biogeochemical cycle the mineral elements in soil can be taken up by grassland plants andaccumulate in their body forming the vertical-banded spectrum and the spatial distribution pattern which isconsistent with geomorphology and topography; then the mineral elements are transferred into human bodiesthrough food chain via plants and products from grassland animal husbandry. The mineral elements not onlyplay an important role in maintaining the balance of grassland ecosystem and the livestock-pasture system interms of their sustainable development but also have significant influence on the quality of livestock products.According to its characteristics and distribution patterns in space-time, we divide different grassland into different types. We also establish a mathmatical model for mineral elements in plants in grassland successionprocess. We can apply this theory to monitoring the supply of mineral elements in prataculture productionpractice so as to facilitate high-yield, high-quality produce. Consequently, meet the demands of sustainabledevelopment of prataculture and grassland animal husbandry. We should pay more attention on the“StarvationEffect”phenomenon when apply it in practice to avoid the illusion caused by mineral elements accumulationand differentiation behavior and provides mineral nutrition to plants scientifically.