毛乌素沙地天然臭柏群落有性更新的微生境特征

在毛乌素沙地天然臭柏(Sabina vulgaris)群落内,按群落外貌特征设置5类样地,分别定义为乌柳灌丛林地(A)、乌柳+臭柏灌丛林地(B)、臭柏+乌柳灌丛林地(C)、臭柏灌丛林地(D)和乌柳被伐区(E),采用样方调查法对其有性更新微生境特征进行了调查。结果表明:臭柏幼苗的空间分布为非均匀式,幼苗多出现在乌柳灌林地下,并且呈现愈靠近树干基部幼苗数量愈多的空间格局。5类样地中共出现67种植物,并呈现从A样地向D样地植物种数量逐渐下降的趋势。A类立地内植物种类数最多,达到50种,其中喜湿的植物占2.7%,而D类立地最少,并且喜湿的植物退出,旱生植物占到50%。从A样方到D样方长达1.5 km的样带上,乌柳的株数依次减少,并在D样地完全消失。臭柏有性更新幼苗数从A样方的17.4株/m2下降到D样方的0株/m2。环境变量的测定表明,地表温度、光照强度和土壤表层含水量是影响臭柏天然更新的主要环境因子。E样地内的光照强度明显增强,臭柏有性更新幼苗株数从采伐前的17.4株/m2急剧下降到0.2株/m2,并且从采伐后每年没有新的更新幼苗出现。A样地与其它样地相比具有光照强度、气温和地温低,空气相对湿度、表土含水量、浅层地下水位高的特征,是臭柏有性更新最适宜的微生境。保护毛乌素沙地天然乌柳灌丛地是维持天然臭柏种群稳定,促进其恢复的重要措施。

Microhabitat Characteristics of Natural Regeneration ofSabina vulgaris Community in Mu Us Sandland

The sexual regeneration microhabitat characteristics of natural Sabina vulgaris community were investigated by random sampling in Mu Us Sandland,and community was classified 5 types according to their appearance characteristics,which were Salix cheilophila(A),Salix cheilophila Sabina vulgaris(B),Sabina vulgaris Salix cheilophila(C),Sabina vulgaris(D) and cuned Salix cheilophila plot(E).Results showed that: Non-uniform spatial distribution pattern presented that Sabina vulgaris seedlings were mainly distributed under the Salix cheilophila canopies,and the closer to the base of the tree stems,the more the Sabina vulgaris seedlings existed.There were 67 plant species in 5 plots in all,and the number of plant species decreased from plot A to plot D.The number of plant species under Salix cheilophila shrubs(site A) was the largest and reached 50 kinds,among which 2.7 percent was hygrophytia plant.However,on dunes fixed by Sabina vulgaris shrubs(site D) the number of plant species was the least,among which xerophil accounted 50 percent and hygrophytia plant disappeared.Along 1.5km transect from sampling A to sampling D,Salix cheilophila decreased gradually and at last disappeared on site D.The number of sexual regeneration seedlings of Sabina vulgaris decreaced from 17.4 per square meter on site A to 0 per square meter on site D.Determination on environmental variable indicated that the main environmental factors effecting natural regeneration of Sabina vulgaris included land surface temperature,irradiation and water content.After deforestation irradiation in Salix cheilophila shrubs(site E) was enhanced obviously,however,the number of sexual regeneration seedlings of Sabina vulgaris,especially the number of plantlets,sharp decreased from 17.4 per square meter in site A to 0.2 per square meter,and there was no sexual regeneration seedling appeared.Comparing with other plots,Salix cheilophila shrubs had the flowing predominance,such as well irradiation,lower air and ground temperature,higher air relative humidity,higher moisture content in surface soil and higher shallow groundwater level,which was the most feasible microenvironment for sexual regeneration of Sabina vulgaris.Protecting natural Salix cheilophila shrubs in Mu Us Sandland was the important measure to maintain population stability of natural Sabina vulgaris and promote its restoration.