發(fā)布時間：2018-05-26 09:26

  本文選題：人工林 + 退耕年限　； 參考：《西北農(nóng)林科技大學》2017年博士論文

【摘要】：明確退耕還林下土壤氮庫的動態(tài)變化特征以及與土壤碳庫的關系對于認知植被恢復下土壤氮素固存、提升土壤質(zhì)量以及改良生態(tài)環(huán)境效應有重要意義。本研究在退耕還林工程背景下,以黃土丘陵區(qū)主要人工林和不同退耕年限刺槐、檸條和荒草作為研究對象,采用時空替代法,通過野外試驗與室內(nèi)分析相結合的方法研究了不同人工林土壤氮組分積累、轉(zhuǎn)化特征以及隨退耕年限的演變規(guī)律,并結合室內(nèi)培養(yǎng)試驗,分析了凋落物種類、水分和溫度對土壤氮素轉(zhuǎn)化的影響,通過比較不同人工林以及不同退耕年限下刺槐、檸條和荒草土壤碳庫,明確了土壤氮素積累、轉(zhuǎn)化與土壤碳庫的關系。取得以下主要結論:(1)退耕植被恢復對于不同人工林0-200 cm土層氮組分含量、儲量和積累量有著明顯影響。不同人工林土壤全氮、硝態(tài)氮和無機氮含量隨土層深度的變化規(guī)律基本相似,淺層(0-40 cm)變化大于深層(40-200 cm);銨態(tài)氮、可溶性全氮和可溶性有機氮含量隨土層深度的變化不明顯。與耕地相比,側(cè)柏和刺槐+側(cè)柏土壤硝態(tài)氮、無機氮、可溶性全氮和可溶性有機氮儲量明顯下降,但檸條全氮、銨態(tài)氮、硝態(tài)氮、無機氮、可溶性全氮和可溶性有機氮儲量明顯提高,0-200 cm土層氮組分儲量分別比耕地高2.24 Mg/ha、8.49 kg/ha、15.00 kg/ha、23.54 kg/ha、429.63 kg/ha和406.44 kg/ha,氮組分積累效果顯著。說明植被恢復是影響土壤氮素積累的重要因素,不同人工林土壤氮組分積累效應差異較大。(2)不同退耕年限刺槐、檸條和荒草土壤氮組分儲量和積累量不同,深層土壤占據(jù)重要地位。不同退耕年限刺槐、檸條和荒草土壤全氮、銨態(tài)氮、硝態(tài)氮、無機氮、可溶性全氮和可溶性有機氮儲量隨退耕年限的變化規(guī)律不一致,且表層與深層土壤隨退耕年限的變化也不同。不同土層氮組分儲量分布比例差異顯著,深層土壤占據(jù)很大比例;100-200 cm土層氮組分儲量分布比例最大,為34.18%-57.47%;40-100 cm土層分布比例為20.11%-37.03%。大部分情況下,不同退耕年限刺槐、檸條和荒草土壤全氮和硝態(tài)氮積累量隨土層0-10 cm、10-40 cm、40-100 cm和100-200 cm呈下降趨勢,而銨態(tài)氮積累量呈升高趨勢。(3)凋落物種類和溫度是影響土壤氮素轉(zhuǎn)化的主要因素,對土壤氮素轉(zhuǎn)化起重要作用。不同凋落物處理下土壤硝態(tài)氮含量、硝化速率、礦化氮含量和礦化速率差異顯著,均表現(xiàn)為檸條凋落物處理最高,其次是刺槐、9:1刺槐+山桃凋落物處理和對照,荒草和1:1刺槐+側(cè)柏凋落物處理最低。不同田間持水量處理下土壤銨態(tài)氮含量、氨化速率、硝態(tài)氮含量、硝化速率、礦化氮含量和礦化速率差異不顯著。不同溫度處理下土壤銨態(tài)氮含量、硝態(tài)氮含量和礦化氮含量有顯著差異;38℃處理下土壤銨態(tài)氮含量均值為5.87 mg/kg,顯著高于12℃和25℃處理;38℃處理下土壤硝態(tài)氮和礦化氮含量分別比12℃和25℃處理高11.87mg/kg和2.67 mg/kg(硝態(tài)氮)、11.35 mg/kg和7.57 mg/kg(礦化氮)。在同一溫度和田間持水量條件下不同凋落物處理土壤硝態(tài)氮含量和礦化氮含量差異達極顯著水平。在培養(yǎng)過程中,不同凋落物處理土壤硝態(tài)氮和礦化氮含量最高的處理是在25℃60%田間持水量條件下檸條凋落物處理,其他凋落物處理最高值出現(xiàn)在38℃60%田間持水量條件下。(4)植被類型、退耕年限以及土層深度是影響土壤碳庫的主要因素,三者共同調(diào)控土壤碳庫變化。不同人工林土壤有機碳、可溶性有機碳、可溶性無機碳和可溶性總碳庫存在極顯著差異。檸條0-10 cm、0-40 cm、0-100 cm和0-200cm土層有機碳庫最高,分別比耕地高2.41 Mg/ha、2.64 Mg/ha、3.12Mg/ha和5.99 Mg/ha;荒草土壤可溶性有機碳、可溶性無機碳和可溶性總碳庫最高,0-200 cm土層碳庫分別比耕地高10.20%、8.34%和8.62%。不同退耕年限刺槐、檸條和荒草土壤碳庫隨退耕年限的變化趨勢各不相同。(5)植被類型、退耕年限和土層深度是影響土壤氮素積累、轉(zhuǎn)化與土壤碳庫關系的重要因素,共同調(diào)控土壤碳氮關系。不同人工林各土層氮組分積累量對土壤碳庫的影響具有相似性,即0-10 cm和0-40 cm土層表現(xiàn)較為一致,0-100cm和0-200 cm土層較為一致,但不同土層氮組分轉(zhuǎn)化速率對土壤碳庫的影響差異較大;所有人工林各土層全氮積累、轉(zhuǎn)化對土壤有機碳影響均為最敏感。不同退耕年限刺槐、檸條和荒草各土層氮組分積累量對土壤碳庫的影響差異較大。不同退耕年限刺槐土壤可溶性有機氮和可溶性全氮積累量對土壤可溶性有機碳和可溶性總碳庫影響較敏感,可溶性有機氮和可溶性全氮轉(zhuǎn)化速率對土壤可溶性總碳庫影響較大。不同退耕年限檸條0-200 cm土層氮組分積累量對土壤碳庫的影響較其他土層更明顯;土壤銨態(tài)氮、硝態(tài)氮和無機氮轉(zhuǎn)化速率對土壤可溶性無機碳庫影響較大。不同退耕年限荒草土壤氮組分積累、轉(zhuǎn)化對土壤碳庫的影響隨土層不同差異較大。
[Abstract]:The dynamic change characteristics of soil nitrogen pool under returning farmland to forest and the relationship with soil carbon pool are of great significance to soil nitrogen retention, improving soil quality and improving ecological environment effect under cognitive vegetation restoration. Under the background of returning farmland to forest project, the main artificial forests in loess hilly area and different years of cultivated locust, lime, lime, and lime With the method of space-time substitution, the accumulation of nitrogen components, transformation characteristics and the evolution regularity with the years of returning cultivated land in different plantations were studied by the method of space-time substitution. The effects of litter species, water and temperature on soil nitrogen transformation were analyzed. The relationship between soil nitrogen accumulation and soil carbon storage was clarified by comparing different artificial forests and different cultivated years of Caragana korshinskii and wasteland soil. The following main conclusions were obtained: (1) the restoration of cultivated vegetation has a significant influence on the contents, reserves and accumulation of nitrogen components in 0-200 cm soil layers of different plantation. The soil total nitrogen, nitrate and inorganic nitrogen content was similar to the soil depth, and the change of the shallow layer (0-40 cm) was greater than that in the deep layer (40-200 cm), and the content of ammonium nitrogen, soluble total nitrogen and soluble organic nitrogen were not obvious with the depth of the soil. The reserves of soluble organic nitrogen were obviously decreased, but the reserves of Caragana total nitrogen, ammonium nitrogen, nitrate nitrogen, inorganic nitrogen, soluble total nitrogen and soluble organic nitrogen were obviously improved. The reserves of nitrogen components in the 0-200 cm soil layer were 2.24 Mg/ha, 8.49 kg/ha, 15 kg/ha, 23.54 kg/ha, 429.63 kg/ha and 406.44 kg/ha, respectively. The accumulation effect of soil nitrogen accumulation in soil and soil of different artificial forests has great difference. (2) the reserves and accumulation of nitrogen components of Caragana korshinskii and barren grass soil are different, and the deep soil occupies an important position. The reserves of soluble total nitrogen and soluble organic nitrogen are not consistent with the years of tillage, and the change of surface and deep soil varies with the years of returning farmland. The distribution ratio of nitrogen components in different soil layers is significant, and the deep soil occupies a large proportion; the largest distribution ratio of nitrogen component in 100-200 cm soil layer is 34.18%-57.47%; 40-100 cm The soil layer distribution ratio is 20.11%-37.03%., the accumulation of total nitrogen and nitrate nitrogen in soil of Caragana Caragana and barren grass with different years of tillage is decreased with 0-10 cm, 10-40 cm, 40-100 cm and 100-200 cm, while the accumulation of ammonium nitrogen is increasing. (3) the species and temperature of litter are the main factors affecting the soil nitrogen transformation. The content of nitrate nitrogen, nitrification rate, mineralized nitrogen content and mineralization rate of soil under different litter treatments were significantly different, all of which showed the highest treatment for Caragana litter, followed by Robinia pseudoacacia, 9:1 pseudoacacia + peach litter treatment and control, and the least treatment of wild grass and 1:1 Robinia pseudoacacia + Platycladus orientalis. The soil ammonium nitrogen content, ammoniation rate, nitrate nitrogen content, nitrification rate, mineralized nitrogen content and mineralization rate have no significant difference under water treatment. The soil ammonium nitrogen content, nitrate nitrogen content and mineralized nitrogen content under different temperature treatments are significantly different. The mean value of ammonium nitrogen in soil under 38 centigrade is 5.87 mg/kg, significantly higher than that of 12 and 25. The content of nitrate nitrogen and mineralized nitrogen in soil treated at 38 degrees centigrade was higher 11.87mg/kg and 2.67 mg/kg (nitrate nitrogen), 11.35 mg/kg and 7.57 mg/kg (mineralized nitrogen) respectively. The difference of nitrate nitrogen content and mineralized nitrogen content in soil treated with different litter under the same temperature and field water content was very significant. The highest concentration of nitrate and mineralized nitrogen in soil with different litter treatment was treated with Caragana litter under the condition of 60% field water holding at 25 C. The highest value of other litter treatment appeared under the condition of 38 C 60% field water capacity. (4) the vegetation type, the year of returning farmland and the depth of soil layer were the main factors affecting the soil carbon pool, and the three were the main factors. The soil organic carbon, soluble organic carbon, soluble inorganic carbon and total soluble total carbon pool in different plantations have very significant differences. 0-10 cm, 0-40 cm, 0-100 cm and 0-200cm soil organic carbon pools of Caragana Caragana, 2.41 Mg/ha, 2.64 Mg/ha, 3.12Mg/ha and 5.99 Mg/ha higher than that of cultivated land; Soluble inorganic carbon and soluble total carbon pool are the highest, 0-200 cm soil layer carbon storage is 10.20%, 8.34% and 8.62%., respectively, different years of cultivated locust, Caragana Caragana and grass soil carbon pool changes with the years of conversion of cultivated land. (5) vegetation type, soil depth is the influence of soil nitrogen accumulation, transformation and soil carbon storage relationship. The influence of the accumulation of nitrogen components in different soil layers on soil carbon pool is similar, that is, 0-10 cm and 0-40 cm soil layers are more consistent, 0-100cm and 0-200 cm soil layers are more consistent, but the effect of nitrogen component transformation rate on soil carbon pool in different soil layers is more different; all artificial forests are different. The effects of total nitrogen accumulation and transformation on soil organic carbon were the most sensitive. The effects of nitrogen accumulation on soil carbon pool in Robinia pseudoacacia, Caragana korshinskii and barren grass with different years of tillage, soluble organic nitrogen and total soluble total nitrogen accumulation on soil soluble organic carbon and total soluble carbon pool in different years of cultivated land The effect of soluble organic nitrogen and total nitrogen conversion rate on soluble total carbon pool of soil was greater. The accumulation of nitrogen component in 0-200 cm soil layer of Caragana Caragana was more obvious than that of other soil layers, and the soil ammonium nitrogen, nitrate nitrogen and inorganic nitrogen conversion rate had great influence on the soil soluble inorganic carbon pool. The effects of accumulation and transformation of nitrogen components on soil carbon storage in different soil types were different with different soil layers.
【學位授予單位】：西北農(nóng)林科技大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：S714.2

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