林地覆盖对雷竹林土壤微生物特征及其与土壤养分制约性关系的影响

为了探讨林地覆盖雷竹林退化机理,给退化雷竹林恢复提供理论参考,对不同覆盖年限(CK、1、3 a 和6 a) 雷竹林土壤微生物区系组成和生物量碳(C_mic)、氮(N_mic)、磷(P_mic)等特征因子进行了测定,并分析了其与土壤养分的制约性关系。结果表明:(1) 雷竹林土壤微生物以细菌为主,真菌次之,放线菌最少,分别占土壤微生物总量的90.11%-98.03%、1.04%-9.22%和0.67%-1.37%。随覆盖年限增加,细菌、放线菌比率呈下降趋势,真菌比率呈上升趋势;土壤微生物总数、细菌和放线菌数量及C_mic、N_mic、P_mic均呈先升高后降低的变化趋势,试验雷竹林间差异极显著,真菌数量总体呈极显著升高趋势。(2)雷竹林土壤微生物特征因子与土壤有机质(SOM)、全氮(TN)、全磷(TP)、碱解氮(Available nitrogen, AN)和pH均呈显著或极显著相关,其中,CK和覆盖1 a、3 a雷竹林土壤微生物特征因子与土壤养分主要呈正相关,与pH呈负相关,而覆盖6 a雷竹林则相反。(3)不同覆盖年限雷竹林土壤养分与土壤微生物的制约性关系存在一定的差异,CK雷竹林土壤SOM、TN、AN、速效钾(AK)和pH主要影响土壤C_mic、N_mic和细菌,覆盖1 a雷竹林土壤SOM、TN、TP和AK主要影响土壤P_mic、放线菌和细菌,覆盖3 a雷竹林土壤SOM、TN、速效磷(AP)和AN主要影响土壤N_mic、放线菌和真菌,覆盖6 a雷竹林土壤SOM、TN和pH主要影响土壤N_mic、真菌。研究表明:长期覆盖雷竹林土壤细菌、放线菌数量与比例明显降低,真菌数量与比例明显提高,土壤养分与土壤微生物的制约性作用关系会发生较为明显变化,产生土壤障害,这是覆盖雷竹林退化的主要原因之一。

Influence of mulching management on soil microbe and its relationship with soil nutrient in Phyllostachys praecox stand

Soil microbe is the major component of soil throghout the whole process of soil development, and plays a key role in material recycling and energy conversion in soil ecosystem.The living environment for soil microbe is a very sensitive early-warning indicator of changes in soil ecosystem.To approach the impact of intensive and mulching management on soil microbial biomass populations and biomass and to clarify the degradation mechanism of Phyllostachys praecox stand, the test plot was established.With the experiment, microbial composition, microbial biomass carbon (C_mic), microbial biomass nitrogen(N_mic), microbial biomass phosphorus (P_mic) from bamboo stand with different mulching management treatments(6a, 3a, 1a and CK stand) were determined, meanwhile the relationship between soil microbe and soil organic matter(SOM), total nitrogen(TN), total phosphorus(TP), total potassium(TK), available nitrogen(AN), available phosphorus(AP), available potassium(AK) and pH was analyzed, too, and this research will provide theoretical guidance for regeneration of degraded bamboo plantations. The results showed that: (1) Among the microble in Ph.praeox stand soil, bacteria was the dominant, fungi was the next and actinomycete was the least, and accounted for 90.11%-98.03%, 1.04%-9.22% and 0.67%-1.37% of total number for soil microble, respectively.With the time of mulching management extending, the percentage of soil bacteria and actinomycete descended, while the percentage of fungi ascended.Moreover, the quantity of microbe, bacteria, actinomycete, and C_mic, N_mic, P_mic increased firstly then fell, and the difference among all treatments were highly significant, while the number of fungi increased significantly.(2) There were highly significant or significant correlation between soil microbial factors and SOM, TN, TP, AN and pH, and the correlation among soil nutrients and soil microbial factors were positive for CK, 1a and 3a stands, while that was negative for 6a stand.(3) There were different restrictive relationship between soil microbe factors and soil nutrient for CK, 1a, 3a and 6a stand.In the CK stand, SOM, TN, pH, AN and AK played a greater role and mainly affected on C_mic, N_mic and bacteria.While for the 1a stand, SOM, TN, TP and AK had a greater effect on soil P_mic, actinomycete and bacteria.And in the 3a stand, SOM, TN, AP and AN mainly influenced soil N_mic, actinomycete and fungi.Moreover for the 6a stand, SOM, TN and pH proudly affected on soil N_mic and fungi.It could be concluded that based on the results soil obstacle caused by inhibition of actinomycete and bacteria, in addition to promotion of fungi, and changed restrictive relationship between soil microbial factors and soil nutrients were main cause leading to soil degradation for mulching bamboo stand.