Changes in soil phosphorus fractions under different land uses in desert grasslands in northwestern China

?

?

論文類型：研究型論文

作者單位：1State Key Laboratory of Grassland Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, Engineering Research Center of Grassland Industry, Ministry of Education, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China

2Laboratory of Ecology and Agriculture, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China

引用文本：Wang, Z. R., Li, F. R., Liu, L. L., & Yang, K. (2022). Changes in soil phosphorus fractions under different land uses in desert grasslands in northwestern China.?European Journal of Soil Science, e13255.

?

摘要

人類通過將原生植被轉(zhuǎn)化為農(nóng)業(yè)用地和非農(nóng)用地，影響荒漠生態(tài)系統(tǒng)的結(jié)構(gòu)和功能。然而，荒漠草地上不同的土地利用如何通過創(chuàng)造不同的土壤理化和微生物特性來影響土壤中具有不同穩(wěn)定性的磷（P）組分，目前還知之甚少。為了解決這個問題，在中國西北干旱區(qū)進行了一項實地研究，選擇了一個包含天然荒漠草地的區(qū)域和三個相鄰的不同管理方式的荒漠草地利用轉(zhuǎn)化：即28年的雨養(yǎng)灌木-梭梭（Haloxylon ammodendron）人工林、35年的灌溉喬木-楊樹（Populus gansuensis）人工林，以及33-40年的灌溉與施肥農(nóng)田。本研究收集了4種土地利用類型的土壤無機磷和有機磷（Pi和Po）（不穩(wěn)定P：即樹脂和NaHCO3可提取P；中度不穩(wěn)定P：即NaOH-可提取P；頑固性P：即HCl-可提取P和殘留P)，并利用土壤變量作為預測因子。使用增強回歸樹分析（boosted regression tree analysis）來評估個體預測因子對P組分變化的相對貢獻。結(jié)果表明，與天然荒漠草地相比，（1）農(nóng)田全磷組分（77%–418%）中樹脂P增幅最大；（2）除樹脂P外，其余各磷組分均在人工林中（52%–367%），不穩(wěn)定Po含量增幅最大；（3）灌叢人工林NaHCO3-P和HCl-Pi含量(14%–134%)均高于天然荒漠草地，其中不穩(wěn)定Pi含量增幅最大。土壤性質(zhì)對不同P組分的變化具有顯著的控制作用，可解釋51%–93%的磷組分變化，但各P組分間的主要影響因素存在差異。研究結(jié)果表明，不同土地利用方式對荒漠草地土壤中磷的組分組成和有效性存在顯著差異，土壤磷循環(huán)可通過改變土地利用方式和管理水平來調(diào)節(jié)。

?

2. 試驗方法

2.1 試驗地點

Figure 1 The study area in the western Gansu Province in northwestern China. The four studied land-use types included (a) natural desert grassland (NG), (b) shrub plantation (SP), (c) poplar tree plantation (TP), and (d) cropland (CL)

圖1研究區(qū)位于中國甘肅省西部。研究的4種土地利用類型包括（a）天然荒漠草地（NG）、（b）灌木人工林（SP）、（c）楊樹人工林（TP）和（d）農(nóng)田（CL）。

?

2.3. 土壤取樣

2017年八月中旬。

2.4. 土壤理化性質(zhì)測定

土壤含水量，pH，有機碳，全氮，全磷，微生物量碳，堿性磷酸酶。

2.5. 土壤磷組分測定

(1) the most available P (resin-Pi);

(2) labile P (Pi and Po extracted by NaHCO3; Olsen P);

(3) moderately labile P (Fe and Al associated Pi and Po extracted by NaOH);

(4) poorly soluble P (Ca associated Pi and Po extracted by dHCl and cHCl);

(5) the most resistant and insoluble P (residual-P, which was calculated as the difference between soil total P and the sum of the first eight extracted P fractions).

(6) dHCl-Pi and cHCl-Pi into a single HCl-Pi fraction.

2.6.1. 數(shù)據(jù)分析

增強回歸樹（boosted regression trees，BRT）分析，以量化單個預測變量的相對重要性（RI）來解釋每個P組分的方差。

3. 結(jié)果

3.1. 土壤P組分絕對和相對濃度變化

Table 1 Changes in absolute concentrations (mg kg-1) of measured soil inorganic and organic phosphorus (Pi and Po) fractions of decreasing lability (labile, moderately labile, and recalcitrant P) after conversion of natural desert grassland to rainfed shrub (Haloxylon ammodendron) plantation, irrigated poplar tree (Populus gansuensis) plantation, and irrigated and fertilized cropland

3.2. 土壤理化和微生物特性的變化

TABLE 2 Changes in the proportions (%) of measured soil inorganic and organic phosphorus (Pi and Po) fractions in the soil total P content after conversion of natural desert grassland to rainfed shrub (Haloxylon ammodendron) plantation, irrigated poplar tree (Populus gansuensis) plantation, and irrigated and fertilized cropland. Soil Pi and Po fractions were grouped into three pools of decreasing lability (labile, moderately labile, and recalcitrant P)

TABLE 3 Changes in measured soil physicochemical and biological properties as predictors after conversion of natural desert grassland to rainfed shrub (Haloxylon ammodendron) plantation, irrigated poplar tree (Populus gansuensis) plantation, and irrigated and fertilized cropland

?

3.3. 土壤磷組分和預測變量的關(guān)系

FIGURE 2 RDA (redundancy analysis) two-dimensional ordination diagram of the first two axes showing sites (land use types), soil P fractions, and soil predictor variables. Circles represent natural desert grasslands, rhombuses represent shrub plantations, triangles represent tree plantations, and asterisks represent croplands. Soil predictor variables are soil pH (pH), soil bulk density (SBD), soil water content (SWC), soil organic carbon (SOC), soil total nitrogen (TN), soil N:P ratio (N:P), soil C:P ratio (C:P), soil microbial biomass carbon (MBC), and soil alkaline phosphatase activity (ALP). Vector overlays present the direction (arrow) and strength (length) corresponding to the variance that can be explained by the predictor variables

?

Table 4 The results of linear regression analyses for quantifying the relationships between changes in concentrations of eight measured soil inorganic and organic phosphorus (Pi and Po) fractions and changes in soil predictor variables after conversion of natural desert grassland to differently managed land-use systems (shrub plantation, tree plantation, and cropland)

3.4. 預測變量在調(diào)節(jié)土壤P動態(tài)的相對重要性

FIGURE 3 The relative influences of the predictor variables on the patterns of soil total P and eight measured soil inorganic and organic phosphorus (Pi and Po) fractions. The predictor variables included soil pH (pH), soil bulk density (SBD), soil water content (SWC), soil organic carbon (SOC), soil total nitrogen (TN), soil N:P ratio (N:P), soil C:P ratio (C:P), soil microbial biomass carbon (MBC), and soil alkaline phosphatase activity (ALP). R2 denotes the proportion of the variation in each P fraction explained by the BRT models. The statistical significance of the BRT model is tested using the Monte Carlo permutation test (*p < 0.05, **p < 0.01, ***p < 0.001)

?

4. 討論

4.1. 荒漠土壤P組分對不同土地利用方式的差異響應(yīng)

4.2. 不同P組分對土地利用變化響應(yīng)的關(guān)鍵預測因子

?

5. 結(jié)論

這項研究解決了關(guān)于三種不同的人為利用石灰性荒漠土壤對土壤P組分的去向以及干旱氣候下土壤P變化的主要原因的長期（>28年）后果的關(guān)鍵認識差距。本研究證明，三種不同的沙漠土壤利用和管理策略導致了不同的磷獲取、循環(huán)和積累模式，導致三種土地利用系統(tǒng)之間土壤P組分組成和有效性存在顯著差異。自然荒漠草地向灌溉和施肥農(nóng)田的轉(zhuǎn)變導致表層土壤全磷、不穩(wěn)定和中度不穩(wěn)定磷含量的增加最大，其次是自然荒漠草地向灌溉和不施肥的喬木種植園的轉(zhuǎn)變，然后是不灌溉和不施肥的灌木種植園。8個磷組分對土地利用變化的響應(yīng)主要受土壤水分、pH、有機碳、全氮、微生物量C和堿性磷活性的調(diào)節(jié)，但各磷組分的主導影響因素存在差異。

土地利用變化對特定P組分的影響可以通過改變相應(yīng)P組分變化的關(guān)鍵決定因素的值來調(diào)節(jié)。這些發(fā)現(xiàn)有幾個重要的啟示。土地利用變化對特定P組分的影響可以通過改變相應(yīng)P組分變化的關(guān)鍵決定因素的值來調(diào)節(jié)。這些發(fā)現(xiàn)有幾個重要的啟示。首先，本研究的結(jié)果有助于更準確地理解人為土地利用和管理變化在調(diào)節(jié)土壤磷循環(huán)和生態(tài)系統(tǒng)磷有效性方面所起的關(guān)鍵作用。其次，本研究的結(jié)果強調(diào)了在未來的磷循環(huán)模型中納入不同磷組分的土地利用變化驅(qū)動的響應(yīng)以及不同的磷組分-土壤環(huán)境關(guān)系的重要性，以提高模型預測的可靠性。最后，也是最重要的是，本研究的研究結(jié)果為通過調(diào)整土地利用類型和管理強度來管理旱地石灰性土壤中的磷循環(huán)提供了重要的見解。