水保所知识产出(1956---)知识库

土壤无机氮的可利用性是影响植物生长发育和植被演替进程的关键因子之一，尤其在生态
系统十分脆弱的黄土丘陵沟壑区更为重要。因此，采用时空代换法，通过选取不同退耕年限(10 a、
20 a、30 a、40 a)的刺槐林地及相邻对照草地为研究对象，系统研究刺槐林在生长季(4 ～9 月)土壤
无机氮净转化速率的变化情况。结果表明:(1)刺槐林地土壤 NO
－
3
－ N 平均含量约是对照草地的
4． 57 倍，而 NH
+
4
－ N 在两个样地之间没有显著差异。(2)刺槐林地及对照草地土壤在7 ～8 月以硝
化作用为主，在 4 ～ 5 月和 8 ～ 9 月以氨化过程为主，且刺槐林地氮素净转化速率大于对照样地。
(3)刺槐林地土壤 NO
－
3
－ N 在前30 a 处于积累状态，随后呈现消耗趋势。总而言之，退耕地刺槐林
营造可以减少土壤 NO
－
3
－ N 的淋失，提高 NO
－
3
－ N 净转化速率，但刺槐林 NO
－
3
－ N 的累积状态在
30 a 后变为消耗状态。所以要采取应对 30 a 以上林龄的刺槐林采取间伐措施，以促进刺槐林的健
康发展。

Inorganic nitrogen is one of the major nutrients in plant growth，especially in artificial revegetation． Ro-
binia pseudoacacia plantation were considered one of the primary and promising trees of artificial revegetation in the
Loess Plateau due to its fast growth and ability of fixing atmospheric nitrogen． However，the main form，net transfor-
mation rates and dynamics of inorganic nitrogen of Robinia pseudoacacia in the Loess Plateau were still unknown． In
this study，we aimed to expose the capability of offering nitrogen through inorganic nitrogen． A chronosequence from
10 ～40 year-old plantations and adjacent contrasting grasslands in natural control with similar age were selected．
The result showed as follows: (1) the average content of NO
－
3
－ N was the 4． 57 times in Robinia pseudoacacia
plantation than that in the contrasting grasslands，but no influence on NH
+
4
－ N． (2) compared with lands and a-
bandoned years，the soil moisture and temperature were the major effects on net transformation rates，showing nitrifi-
cation was the prominent nitrogen transformation processes on July-August，while ammonization was the key nitrogen
transformation processes on April-May and August-September，and Robinia pseudoacacia plantations had faster net
nitrogen transformation rates than the contrasting grasslands． (3) Robinia pseudoacacia plantations can accelerate
the accumulation of NO
－
3
－ N compared with the grasslands，but a consumption was occurred exceeding 30 year-old．
Overall，Robinia pseudoacacia plantation can reduce NO
－
3
－ N leaching，but no influence on NH
+
4
－ N，and Robinia
pseudoacacia plantation had a consumption trend of NO
－
3
－ N after 30 years． So，some management，such as
thinning，should be taken to accelerate the healthy development of Robinia pseudoacacia plantation in the Loess
Plateau．