張建鋒,孫保平,郭虎波,何艷,張麗,申豪杰

(北京林業(yè)大學(xué)水土保持與荒漠化防治教育部重點(diǎn)實(shí)驗(yàn)室,100083,北京)

干熱河谷區(qū)6種典型林型土壤改良效應(yīng)評(píng)價(jià)

張建鋒,孫保平?,郭虎波,何艷,張麗,申豪杰

(北京林業(yè)大學(xué)水土保持與荒漠化防治教育部重點(diǎn)實(shí)驗(yàn)室,100083,北京)

采用野外調(diào)查和室內(nèi)分析相結(jié)合的方法,測(cè)定巧家縣境內(nèi)干熱河谷區(qū)6種典型林型(華山松+馬桑+黑麥草、華山松+興安落葉松、核桃、華山松、花椒、桑樹(shù))林地和對(duì)照(農(nóng)田)的主要理化性質(zhì),并利用隸屬函數(shù)評(píng)價(jià)法,評(píng)價(jià)6種林型的土壤改良效應(yīng),旨在為退耕還林篩選理想的林型提供科學(xué)依據(jù)和實(shí)踐參考。研究結(jié)果表明:1)退耕后,不同林型林地土壤物理結(jié)構(gòu)得到不同程度改善,土壤養(yǎng)分狀況進(jìn)一步好轉(zhuǎn),土壤密度、土壤含水量、有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)、土壤全量養(yǎng)分和速效養(yǎng)分的質(zhì)量分?jǐn)?shù)均表現(xiàn)為喬灌草混交林＞喬木混交林＞純林;2)不同林型土壤改良效應(yīng)綜合評(píng)價(jià)結(jié)果為華山松+馬桑+黑麥草＞華山松+興安落葉松＞華山松＞農(nóng)田＞桑樹(shù)＞核桃＞花椒,華山松+馬桑+黑麥草喬灌草混交模式土壤改良綜合效應(yīng)最佳,其次是華山松+興安落葉松:在不同樹(shù)種的純林之間,華山松土壤改良效應(yīng)綜合評(píng)價(jià)最高,核桃和桑樹(shù)土壤改良效應(yīng)綜合評(píng)價(jià)相當(dāng),花椒最差。可見(jiàn),華山松+馬桑+黑麥草喬灌草混交是當(dāng)?shù)赝寥栏牧嫉睦硐肽Ｊ?適宜大力推廣。

土壤質(zhì)量;土壤改良效應(yīng);退耕林地;干熱河谷區(qū);巧家縣

退耕還林是一項(xiàng)長(zhǎng)期而復(fù)雜的生態(tài)工程,目的是恢復(fù)植被,減少水土流失,防沙治沙,改善日益惡化的生態(tài)環(huán)境[1]。土壤退化是目前全球最嚴(yán)重的環(huán)境問(wèn)題之一,土壤是氣候、母質(zhì)、生物、地形、人類活動(dòng)等因子影響下的綜合體,退耕還林后土壤密度、孔隙度、有機(jī)質(zhì)、土壤全量養(yǎng)分和速效養(yǎng)分等含量發(fā)生明顯變化[2-8]。當(dāng)前,學(xué)術(shù)界主要研究退耕林地的生態(tài)效應(yīng),且不同林型林地對(duì)改良土壤理化性質(zhì)方面的作用是研究的重要內(nèi)容。學(xué)者們?cè)诓煌脖粚?duì)土壤物理性質(zhì)的作用、不同干擾對(duì)土壤物理性質(zhì)的影響、不同治理模式對(duì)土壤物理特性變化等方面進(jìn)行了大量的研究,取得了卓越成果[9-10];但研究集中于黃土高原、東北丘陵漫崗區(qū)、西南紫色土區(qū)以及南方紅壤丘陵區(qū),針對(duì)干熱河谷區(qū)不同林型林地的土壤改良效應(yīng)研究偏少[11-15]。筆者通過(guò)干熱河谷區(qū)退耕還林后6種林型林地土壤理化性質(zhì)變化的定量研究,旨在探明干熱河谷區(qū)不同林型的土壤改良效應(yīng),以期為退耕還林工程和生態(tài)修復(fù)規(guī)劃實(shí)施者篩選理想林型提供科學(xué)依據(jù)和實(shí)踐參考。

1 研究區(qū)概況

巧家縣地處金沙江與牛欄江交匯的三角地帶,位于E 102°53＇～103°27＇,N 26°32＇～27°25＇之間,海拔517.0～4 041.6m,不同海拔地帶跨越亞熱帶、溫帶和寒溫帶3種地帶性氣候,極端最高氣溫42.7℃,極端最低氣溫-8℃,年均氣溫17℃,≥10℃的多年平均積溫為7 299.4℃。金沙江由南向北流經(jīng)巧家縣,因?yàn)樗闹芫鶠楦叽蟮纳襟w遮擋,形成一個(gè)狹窄封閉的干熱河谷,金沙江干熱河谷區(qū)位于E100°18＇～103°36＇,N26.6°～28.0°之間。研究區(qū)位于巧家縣干熱河谷區(qū),海拔940.0～2 870.0m,根據(jù)多年氣象資料,極端最高氣溫42℃,極端最低氣溫-2℃,全年降水700～1 000 mm,土壤典型代表為燥紅土或褐紅壤亞類,具有自干熱河谷至亞高山的完整植被垂直帶和西南山地植被與華中、華南丘陵山地植被交匯過(guò)渡的特征。

研究區(qū)所處地實(shí)施退耕還林以來(lái),當(dāng)?shù)乇局耙藛虅t喬、宜灌則灌、宜草則草、喬灌結(jié)合”的原則,重點(diǎn)安排在生態(tài)環(huán)境比較脆弱帶造林,重點(diǎn)栽植了華山松(Pinus armandii)、馬桑(Coriaria nepalensis)、興安落葉松(Larix gmelinii)、核桃(Juglans regia)、板栗(Castanea mollissima)、花椒(Zanthoxylum bungeanum)、云杉(Picea asperata)、車桑子(Dodonaea viscosa.)、膏桐(Jatropha carcass)等樹(shù)種。干熱河谷是我國(guó)典型的生態(tài)脆弱區(qū)和植被恢復(fù)困難地帶,是全國(guó)生態(tài)環(huán)境建設(shè)的重點(diǎn)地區(qū),如何能進(jìn)一步鞏固退耕還林工程建設(shè),積極合理開(kāi)展生態(tài)建設(shè)工作,是干熱河谷地區(qū)的當(dāng)務(wù)之急[16-17]。

2 材料與方法

2.1樣地調(diào)查

2014年4—9月在研究區(qū)選取6種典型林型(華山松+馬桑+黑麥草(Lolium prenne)、華山松+興安落葉松、核桃、華山松、花椒和桑樹(shù)(Morus alba))的退耕還林地為研究對(duì)象,并以1塊農(nóng)田(玉米(Zea mays)地)作為對(duì)照。記錄樣地的海拔、坡位、坡度、坡向、植被覆蓋度等指標(biāo),各林型所在樣地土壤類型均為紅壤,其他基本概況見(jiàn)表1。

表1　各林型所在地基本情況Tab.1 Basic situation of research plots

2.2試驗(yàn)設(shè)計(jì)與方法

在試驗(yàn)區(qū)6種林型的林地中建立6塊標(biāo)準(zhǔn)樣地,每塊標(biāo)準(zhǔn)樣地里選擇3個(gè)25 m×25 m樣方進(jìn)行調(diào)查。在每個(gè)樣方布設(shè)6個(gè)有代表性的樣點(diǎn),按“S”形布點(diǎn),用土鉆分層采集0～20 cm(表層)、20～40 cm(亞表層)和40～60 cm(下層)的土樣,把采集的分析樣品袋裝后帶回實(shí)驗(yàn)室分析測(cè)定[11]90。樣地的土壤密度和孔隙度采用環(huán)刀法測(cè)定;土壤含水量采用烘干法測(cè)定;采用重鉻酸鉀氧化法測(cè)定有機(jī)質(zhì),全氮采用凱氏定氮法,全磷采用氫氟酸-高氯酸消化比色法,全鉀采用氫氧化鈉熔融-火焰光度法;速效氮測(cè)定用擴(kuò)散吸收法,速效磷測(cè)定用碳酸氫鈉-鉬銻抗比色法,速效鉀測(cè)定用1mol/L 醋酸銨-火焰光度法[18-19]。采用Excel 2007和SPSS13.0統(tǒng)計(jì)分析軟件進(jìn)行數(shù)據(jù)處理。

采用隸屬函數(shù)評(píng)分法[20],從土壤密度、土壤含水量、孔隙度、有機(jī)質(zhì)、全量養(yǎng)分和速效養(yǎng)分共10個(gè)指標(biāo),對(duì)巧家干熱河谷區(qū)的6種林型土壤改良效應(yīng)進(jìn)行了評(píng)價(jià)。

1)如果指標(biāo)與土壤質(zhì)量呈正相關(guān),則

2)如果指標(biāo)與土壤質(zhì)量呈負(fù)相關(guān),則

式中:x(μ)為土壤質(zhì)量隸屬函數(shù)值;x為0～60 cm 3個(gè)土層各指標(biāo)實(shí)測(cè)值的平均值;xmax和xmin分別為不同樣地中土壤指標(biāo)的最大值和最小值。將各指標(biāo)的土壤質(zhì)量隸屬函數(shù)值累加起來(lái)求平均值,平均數(shù)越大,土壤質(zhì)量越好,土壤改良效果就越好。

3 結(jié)果與分析

3.1土壤密度和土壤含水量的變化

土壤密度反映土壤的松緊程度,密度越小,土壤越疏松,密度越大,土壤越緊實(shí),易板結(jié)[19]。從圖1得出,6種林型林地的土壤密度大小為PCL＜PL＜P＜M＜J＜CK＜Z,且不同林地的3個(gè)土壤剖面(0～20、20～40、40～60 cm)的排序與總體排序相同,喬灌草混交林地的土壤最疏松,其次是喬木林混交,M、J和Z的土壤密度與CK土壤密度大小相當(dāng)。

同時(shí),不同樣地的土壤密度隨土壤深度的增加而增大,不同土壤剖面密度差異不太明顯。與土壤密度變化相反,不同林型林地土壤含水量隨土壤深度的增加而逐漸減少,不同林型林地0～20 cm土層土壤含水量差異明顯;PCL混交林地的3個(gè)土壤剖面的土壤含水量均最高,因?yàn)閱坦嗖莼旖桓牧剂送寥澜Y(jié)構(gòu),增強(qiáng)了土壤的保水能力;純林的保水能力為P＞M＞J＞CK＞Z,除Z外,均高于CK。

3.2土壤孔隙度和有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)的變化

圖1　不同林型土壤剖面0～60 cm土層土壤密度、土壤含水量的變化Fig.1Soil density and moisture content in 0-60 cm soil layer of different forest types

土壤孔隙組成是土壤水分、養(yǎng)分、空氣、微生物和植物根系等的通道或儲(chǔ)存庫(kù),土壤孔隙直接反映整個(gè)土體構(gòu)造狀況,是衡量土壤質(zhì)量?jī)?yōu)劣的重要指標(biāo)[20]。如圖2所示,土壤總孔隙、毛管孔隙隨土壤深度的增加而減少;不同林地土壤孔隙度排序?yàn)? PCL＞PL＞P＞M＞J＞Z;非毛管孔隙表層明顯高于其他土層,但不同林地土壤的亞表層和下層趨勢(shì)不明顯,J和CK在40～60 cm之間的非毛管孔隙度高于20～40 cm,可能是由于人為活動(dòng)對(duì)土壤表面反復(fù)踐踏,使得土壤堅(jiān)實(shí)而致;6種林型林地0～20 cm土層的土壤孔隙度是CK的0.96～1.24倍,喬灌草混交林地最高。

圖2　不同林型林地土壤剖面0～60 cm土層總孔隙度、毛管、非毛管孔隙的變化Fig.2 Total porosity,capillary porosity,and non-capillary porosity of soil in 0-60 cm soil layer of different forest types

由圖3可知,喬灌草混交林地與喬木混交林地有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)明顯比其他林地高,其中:PCL＞PL＞P＞J＞M＞Z＞CK,分別比CK增加了3.84、2.89、1.94、1.74、1.67、1.49倍;喬灌草混交林地0～20 cm土層的有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)最高,為31.79 g/ kg;不同林型林地有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)隨土壤深度的增加而減少。土壤有機(jī)質(zhì)源于土壤微生物對(duì)凋落物和根系的分解及其根系與微生物共生體的分泌物,有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)越高說(shuō)明植被改良土壤的效果就越好[8]48。

3.3土壤全氮、全磷、全鉀質(zhì)量分?jǐn)?shù)的變化

土壤全量養(yǎng)分由成土礦物風(fēng)化而生成,是產(chǎn)生速效養(yǎng)分的基礎(chǔ),可以間接反映土壤養(yǎng)分的高低。氮、磷、鉀是植物生長(zhǎng)所必需的3大養(yǎng)分,植物積累的氮素有50%左右來(lái)自土壤,植物所需的磷幾乎全由土壤提供,磷素多以遲效性狀態(tài)存在于土壤中,鉀的多少直接影響作物的生長(zhǎng)量。植被的恢復(fù)過(guò)程能夠促進(jìn)土壤全量養(yǎng)分的積累[21-22]。

圖3　不同林型土層剖面0～60 cm土壤有機(jī)質(zhì)含量的變化Fig.3Organic content of soil in 0-60 cm soil layer of different forest types

如圖4所示,不同林地的全氮、全磷、全鉀質(zhì)量分?jǐn)?shù)在0～20 cm和20～40 cm之間的差異變化明顯,特別是全氮質(zhì)量分?jǐn)?shù)的變化:PCL全氮質(zhì)量分?jǐn)?shù)增幅最明顯,相比CK,0～20 cm和20～40 cm土層全氮質(zhì)量分?jǐn)?shù)增加了178%和120%,0～20 cm土層的全氮質(zhì)量分?jǐn)?shù)排序?yàn)?PCL＞PL＞P＞Z＞J＞M＞CK;0～20 cm土層的全鉀質(zhì)量分?jǐn)?shù)排序?yàn)?PCL＞PL＞CK＞P＞Z＞M＞J;不同林型林地土壤全氮、全鉀質(zhì)量分?jǐn)?shù)隨土壤深度增加而減少,而全磷質(zhì)量分?jǐn)?shù)變化趨勢(shì)不明顯,20～40 cm土層全磷質(zhì)量分?jǐn)?shù)較其他2個(gè)土層大,PCL全磷質(zhì)量分?jǐn)?shù)最大(1.06 g/kg),Z最小(0.326 g/kg)。從圖4還可以看出,CK全鉀質(zhì)量分?jǐn)?shù)在3個(gè)土層均較高,這可能是過(guò)多施用鉀肥或者土壤翻耕導(dǎo)致,需進(jìn)一步研究可能的原因。

圖4　不同林型林地土壤剖面0～60 cm土層全氮、全磷、全鉀質(zhì)量分?jǐn)?shù)的變化Fig.4 Total N,total K and total P content of soil in 0-60 cm soil layer of different forest types

3.4土壤速效氮、速效磷、速效鉀質(zhì)量分?jǐn)?shù)的變化

如圖5所示,除Z(花椒)外,不同林地的速效氮質(zhì)量分?jǐn)?shù)隨土壤深度增加呈減少的趨勢(shì),0～20 cm層不同林地速效氮質(zhì)量分?jǐn)?shù)明顯不同,在0～20 cm層速效氮質(zhì)量分?jǐn)?shù)排序?yàn)?PCL＞CK＞PL＞P＞M＞J＞Z;PCL混交林地比Z速效氮質(zhì)量分?jǐn)?shù)提高了1.48～2.54倍;純林方面,M和J不同土層的氮質(zhì)量分?jǐn)?shù)大體相當(dāng),而P的土壤氮質(zhì)量分?jǐn)?shù)明顯高于M和J。如圖5所示,P、M和J與CK的土壤速效磷質(zhì)量分?jǐn)?shù)隨土壤深度增加而減少,喬灌草混交林地和喬木混交林地20～40 cm層大于其他2個(gè)土層。0～20 cm層土壤速效磷質(zhì)量分?jǐn)?shù)排序?yàn)?PCL＞PL＞M＞P＞J＞CK＞Z。0～20 cm的速效鉀質(zhì)量分?jǐn)?shù)排序?yàn)?PCL＞PL＞P＞CK＞J＞M＞Z,PCL速效鉀質(zhì)量分?jǐn)?shù)比CK增加了2.94倍,M和J大體接近,Z最小,為83.32mg/kg,不同林地速效鉀質(zhì)量分?jǐn)?shù)隨土層深度增加而較少,且不同土層速效鉀質(zhì)量分?jǐn)?shù)變化大。

圖5　不同林型林地土壤剖面0～60 cm速效氮、速效磷、速效鉀質(zhì)量分?jǐn)?shù)的變化Fig.5 Available N,available P and available K of soil in 0-60 cm soil layer of different forest types

3.5土壤改良效應(yīng)評(píng)價(jià)

隸屬函數(shù)評(píng)分法(表2)表明,不同林型林地土壤質(zhì)量綜合得分由高到低順序?yàn)?PCL＞PL＞P＞CK＞M＞J＞Z?？傮w來(lái)看,喬灌草混交林地的土壤改良效果最好,純林林地土壤改良效果較低。另外,本文僅從土壤密度、孔隙度、土壤含水量、有機(jī)質(zhì)、土壤全量養(yǎng)分、速效養(yǎng)分幾個(gè)土壤理化性質(zhì)研究了6種林型的土壤改良情況,缺乏對(duì)土壤理化性質(zhì)影響較大的土壤機(jī)械組成、pH、生物量等數(shù)據(jù),需要進(jìn)一步進(jìn)行監(jiān)測(cè)和研究。

表2　不同林型土壤改良效應(yīng)評(píng)價(jià)Tab.2 Evaluation on effect of soil improvement

4 結(jié)論與建議

1)不同林型林地土壤物理結(jié)構(gòu)得到不同程度改善,土壤養(yǎng)分狀況進(jìn)一步好轉(zhuǎn)。土壤密度、土壤含水量、有機(jī)質(zhì)質(zhì)量分?jǐn)?shù)、土壤全量養(yǎng)分和速效養(yǎng)分的質(zhì)量分?jǐn)?shù)表現(xiàn)為喬灌草混交林＞喬木混交林＞純林;不同林型土壤改良效應(yīng)評(píng)價(jià)綜合得分由高到低順序?yàn)?華山松+馬桑+黑麥草混交林＞華山松+興安落葉松混交林＞華山松純林＞農(nóng)田＞桑樹(shù)純林＞核桃純林＞花椒純林。華山松+馬桑+黑麥草混交林是當(dāng)?shù)赝寥栏牧嫉睦硐肽Ｊ健?/p>

2)建議當(dāng)?shù)厣鷳B(tài)修復(fù)實(shí)施者加大喬灌草混交林營(yíng)造,不定期開(kāi)展林地土壤改良效應(yīng)評(píng)價(jià),同時(shí)針對(duì)不同林型適當(dāng)控制鉀肥的使用,適當(dāng)增加土壤氮素和磷素的攝入,以更好地改善當(dāng)?shù)氐纳鷳B(tài)環(huán)境。

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Evaluation on effects of soil im provement for six typical forest types in dry-hot valley

Zhang Jianfeng,Sun Baoping,Guo Hubo,He Yan,Zhang Li,Shen Haojie

(Key Lab.of Soil&Water Conservation and Desertification Combating,Ministry of Education,Beijing Forestry University, 100083,Beijing,China)

[Background]Dry-hot valley is one of ecologically fragile areas and it is also a difficult strip for vegetation recovery.Forest vegetation plays an important role in reducing water loss and soil erosion, sand prevention,and improving the deteriorating ecological environment.[M ethods]We combined the method of the field investigation and indoor analysis tomeasure themain physical and chemical properties of six types of differentwoodlands(Pinusarmandii+Coriaria nepalensis+Lolium prenne,P.armandii+ Larix gmelinii,Juglansregia,P.armandii,Zanthoxylum bungeanum,and Morusalba)and farmland in the dry-hot valley of Qiaojia County.The study also used amethod of the subordinate function evaluation to evaluate the effects of the soil improvement for six kinds of forests,which aimed to provide scientific basis and practical reference for the selection of ideal forest types for the project of returning farmland to forest.[Results]The results showed:1)Soil structure of different woodlands was improved to some degree and soil nutrientswere further improved,and moisture content,total porosity,capillary porosity, organic matter,total N,total K and available K decreased with the increase of soil depth between differentwoodlands,while the soil density showed an opposite trend.In addition,soil density,moisture,organic matter,soil total nutrient and available nutrient all showed an order of mixed forest of trees, shrubs and grasses＞mixed trees forest＞pure forest.2)The evaluation on effects of the soil improvement of six kinds of typical forests showed:Pinus armandii+C.nepalensi+L.prenne＞P. armandii+L.gmelinii＞P.armandii＞farmland＞M.alba＞J.regia＞Zanthoxylum bungeanum. [Conclusions]On the whole,the effects of soil improvementwere obvious since the project of returning farmland to forest.P.armandii+C.nepalensis+L.prenne had the besteffects of soil improvementwhile P.armandii+Larix gmelinii ranked the second.Among the pure forests,P.armandii had the highest effect of soil improvement,J.regia and M.alba were roughly the same,and Z.bungeanum was the lowest.P.armandii+C.nepalensis+L.prenne(mixed forestof trees,shrubs and grasses)was an ideal model for soil improvement in the local area,which was suitable for promotion in the dry-hot valley area. We suggest that evaluation of the effects of soil improvement should be carried out from time to time so as to increase the soil uptake of N and P to improve the local ecological environment.

soil quality;soil improvement effect;restored forest;dry-hot valley;Qiaojia County

S714.6

A

1672-3007(2016)02-0095-08

10.16843/j.sswc.2016.02.013

2015-04-21

2015-10-26

項(xiàng)目名稱:國(guó)家林業(yè)局公益性行業(yè)科研專項(xiàng)“南方退耕還林工程建設(shè)效益監(jiān)測(cè)評(píng)價(jià)研究”(201004018)

張建鋒(1986—),男,碩士研究生。主要研究方向:水土保持與荒漠化防治。E-mail:zhangjf0501@163.com

簡(jiǎn)介:孫保平(1956—),男,教授,博士生導(dǎo)師。主要研究方向:水土保持與工程綠化。E-mail:sunbp@163.com