退化草地恢复过程中群落物种多样性及生产力对氮磷养分的响应

doi:10.3864/j.issn.0578-1752.2020.13.009

摘要/Abstract

摘要：

【目的】 北方草地过度放牧和刈割造成植被严重退化和土壤养分缺乏。本研究探讨施用氮、磷肥料对退化草地植物群落多样性和生产力的影响。【方法】 在呼伦贝尔退化草地连续进行4年氮、磷添加试验,设置2个施氮水平（0、10 g N·m^-2·a^-1）和6个施磷水平（0、2、4、6、8和10 g P·m^-2·a^-1）,共计12个处理,5次重复。每年5月下旬返青时施肥,8月中旬生物量最大时期进行群落调查,主要进行群落生产力、物种多样性及4种功能群相对生物量的分析。【结果】 2014—2017年物种丰富度降低明显,完全对照处理（既不施氮也不施磷）4年的物种丰富度平均分别是20.2、17.1、14.7、15.2种;对植物群落α多样性（丰富度和优势度指数）研究表明,氮添加降低了群落物种多样性,而磷添加及磷的累积效应均对群落物种多样性无影响。多样性指数年际间差异显著,氮和年交互作用对其具有显著影响。草地群落地上生产力（ANPP）年际间变化显著,2014年最高,2015年最低,变化范围从400 g·m^-2降到100 g·m^-2左右,干旱年份显著低于正常降水年份,磷对群落生产力影响较小,氮添加显著提高了群落地上生产力,而且氮和磷共同添加的影响大于磷单独添加;生长季正常降水年份,氮素是草甸草原植物生长的主要限制因子。氮添加显著影响了各功能群相对生物量,磷添加对各功能群相对生物量影响较小,各功能群相对生物量年际间具有显著差异。氮单独添加显著增加根茎型禾草的相对生物量,但降低了多年生杂类草和丛生禾草的相对生物量,而磷单独添加增加了多年生杂类草和豆科植物功能群的相对生物量,但没有影响根茎型禾草和丛生禾草的相对生物量;氮磷复合添加显著增加了多年生根茎型禾草的相对生物量,但显著降低了其他功能群的相对生物量。此外,氮、磷添加在一定程度上降低植物群落的稳定性。【结论】 氮、磷添加引起不同功能群植物的差异化响应导致群落间原有的等级关系发生变化,尤其是氮添加引起喜氮的根茎型禾草相对生物量迅速增加,最终导致植物群落组成向着根茎型禾草优势度增加的方向发展,物种多样性降低,导致群落稳定性下降。

关键词: 退化草地, 相对生物量, 物种多样性, 功能群, 初级生产力, 呼伦贝尔

Abstract:

【Objective】 Overgrazing and mowing of grassland in north China caused serious vegetation degradation and soil nutrient deficiency. The purpose of this study was to investigate the effects of nitrogen and phosphorus fertilizers on plant community diversity and productivity in the degraded grassland. 【Method】 A four-year nitrogen and phosphorus addition experiment was conducted with two kinds of fertilizers, including calcium superphosphate and ammonium nitrate, scheduled 2 nitrogen rates (0, and 10 g N·m^-2·a^-1) and 6 phosphorus rates (0, 2, 4, 6, 8 and 10 g P·m^-2·a^-1) with interaction between the both, a total of 12 treatments, and each treatment repeated 5 times. Fertilizers were applied when grassland was turning green in late May, and the community was investigated in the period of maximum biomass in the middle of August every year. In the process of research, the community productivity, species diversity and relative biomass of four functional groups were analyzed. 【Result】 From 2014 to 2017, it was found that the species richness decreased by year, and the average species of the control treatment (neither nitrogen nor phosphorus) was 20.2, 17.1, 14.7 and 15.2, respectively. Based on plant community α diversity index (richness and Simpson dominance index) , the study showed that nitrogen addition significantly decreased the species diversity of the community, but phosphorus addition and cumulative effects of phosphorus did not affect the species diversity of the community. There was a significant difference in diversity index among years, and the interaction between nitrogen and year had a significant effect on it. The aboveground net primary productivity (ANPP) of grassland community varied significantly among years, with the highest in 2014 and the lowest in 2015, the range was from 400 g·m ^-2 to 100 g·m^-2, and which in dry years was significantly lower than that in normal precipitation years. Phosphorus addition had little effect on ANPP, while nitrogen addition significantly increased ANPP, and the effect of nitrogen and phosphorus addition together was greater than that of phosphorus alone. In the normal precipitation growing season, nitrogen was the main limiting factor of Hulunber meadow steppe. Nitrogen addition significantly affected the relative biomass of functional groups, while phosphorus addition had little effect on it, and there was a significant difference in the relative biomass of each functional group between years. Nitrogen addition alone significantly increased the relative biomass of the perennial rhizomatous grass (PR), but reduced the relative biomass of the perennial fobs (PF) and perennial bunch grass (PB). Phosphorus addition alone increased relative biomass of PB and perennial leguminous (LE), while had no effect on relative biomass of PR and PB. Combined addition of nitrogen and phosphorus significantly increased the relative biomass of PR, but significantly decreased the relative biomass of the other functional groups. In addition, the nitrogen and phosphorus combined addition partly reduced the plant community stability. 【Conclusion】 The differentiation of different functional types’ responses caused by nitrogen and phosphorus addition led to the changes of the original hierarchical level between different functional groups, especially nitrogen addition could cause a rapid increase in PR relative biomass, and thus led to the plant community structure developing towards the direction of increasing dominance of PR, and decreasing species diversity and community stability.

Key words: degraded grassland, relative biomass, species diversity, functional groups, ANPP, Hulunber

王洪义, 常继方, 王正文. 退化草地恢复过程中群落物种多样性及生产力对氮磷养分的响应[J]. 中国农业科学, 2020, 53(13): 2604-2613.

WANG HongYi, CHANG JiFang, WANG ZhengWen. Responses of Community Species Diversity and Productivity to Nitrogen and Phosphorus Addition During Restoration of Degraded Grassland[J]. Scientia Agricultura Sinica, 2020, 53(13): 2604-2613.

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	自由度Df	丰富度 Species richness	优势度指数 Simpson	地上初级生产力 ANPP
氮N	1	49.471***	128.848***	630.909***
磷Pr	5	0.988	0.666	4.292*
年份Y	3	143.588***	163.980***	956.638***
N×Pr	5	0.184	0.882	1.198
N×Y	3	4.398*	8.801***	81.531***
Pr×Y	15	0.505	1.567	2.756***
N×Pr×Y	15	0.150	0.285	0.782

	自由度 Df	根茎型禾草 Perennial rhizomatous grass, PR	杂类草 Perennial fobs, PF	丛生禾草 Perennial bunch grass, PB	豆科植物 Perennial leguminous plant, LE
氮N	1	214.7331***	178.276***	11.265**	35.081***
磷Pr	5	0.588	1.571	1.292	1.789
年份Y	3	51.790***	6.393***	27.297***	42.878***
N×Pr	5	1.061	2.724*	2.071	0.834
N×Y	3	21.779***	36.254**	1.876	4.135**
Pr×Y	15	0.948	0.997	0.960	0.819
N×Pr×Y	15	1.182	0.653	0.577	0.624