Ecological Response Of Bryophytes To Rocky Desertification And Different Land Uses

Salahxi,located in the southwest of Bijie City,Guizhou Province,with a karst area propotion of 74%,is a typical landform of karst.For a long time,anthropic factors have led to rocky desertification in different degrees,such as vegetation reduction,soil erosion and frequent geological disasters,which have seriously hindered the sustainable development of local socioeconomic.Although some achievements have been made in the theoretical research of rocky desertification control in China,the theory still lags behind the practice in general,which may lead to blindness and uncertainty of the results,and even may cause irreversible negative impact on the local ecological environment.In recent years,the prevention and control of rocky desertification has been raised to the level of national strategy.The theory of rocky desertification control also needs to be further improved and enriched from the ecological level.Current studies have shown that some bryophytes in rocky desertification areas have special drought resistance,which enable them to grow in the harsh rocky desertification environment.It laid a foundation for the positive succession of vegetation communities in rocky desertification area.However,it is noteworthy that previous studies neglected the sensitivity of bryophyte's characteristics to environmental changes,which is not conducive to revealing the succession mechanism of plant communities in rocky desertification areas and formulating effective and reasonable ecological control measures.In this paper,the response of bryophyte characteristics and communities to rocky desertification process and different land use patterns in Salaxi rocky desertification area of Bijie City,Guizhou Province,was investigated by means of field investigation,laboratory experiments and statistics.The interaction between bryophytes and rocky desertification environment was discussed.The results show that:(1)There are 65 species of bryophytes belonging to 43 genera and 27 families in Salaxi research area,of which 6 species belong to 6 genera and 5 families are liverwort taxa;59 species belong to 37 genera and 22 families are moss taxa.Pottiaceae,Brachytheciaceae and Hypnaceae are dominant families.The dominant genera are Brachythecium,Didymodon,Hypnum,Plagiothecium,Hyophila and Bryum.There are 6 bryophyte life forms in the study area,including mats,Short tufts,Tall turfs,Wefts,Cushion and Fans;(2)It was found that there were 45 species of bryophytes belonging to 33 genera and 20 families in the rocky desertification environment,of which 2 species belong to 2 genera and 2 families are liverwort taxa;43 species belong to 31 genera and 18 families are moss taxa..The number of bryophyte families,genera and species decreased significantly during the succession from non-rocky desertification to intensive rocky desertification.Various diversity indices are closely related to the process of rocky desertification,which indicates that the species diversity of bryophytes decreases continuously during the succession process from non-rocky desertification to intensive rocky desertification;(3)A total of 90 bryophyte communities were found in rocky desertification areas of different grades,including 63 mixed communities and 27 pure communities.The number of bryophyte mixed communities decreased with the increase of rocky desertification,while the number of pure communities increased.Through PCA,the succession law of constructive population was constructed,which presented three stages of succession: no-rocky desertification(Metzgeria consanguinea,Lepidozia subtransveersa,Bryum dichotomum),potential to moderate rocky desertification(Didymodon constrictus,Thuidium tamariscinum,Bryum algovicum,Entodon concinnus,Trichostomum brachydontium)and intensive rocky desertification(Bryum argenteum,Didymodon fallax);(4)Bryophytes of wefts dominate in rocky desertification areas.With the intensification of rocky desertification,the proportion of short turfs bryophytes increases first and then decreases.Generally speaking,wefts and short turfs bryophytes are more suitable for karst rocky desertification environment.Among the seven bryophytes,widely growing in the rocky desertification area of Salahixi,they all have their own characteristics of adaptation to rocky desertification and drought environment.These characteristics include: Leaves bordered with special cells,Leaves with hyaline hair-points,nerve enlargement,concave leaves,involuted leaf margins,papillose or mamillose leaves,etc.;(5)During the succession of rocky desertification,the mean values of chlorophyll a,chlorophyll b and total chlorophyll content of Didymodon constrictus and Erythrodontium julaceum showed a significant downward trend.In addition,Bryophytes tended to increase the value of chlorophyll a/b in order to improve the efficiency of light capture when rocky desertification was intensified;(6)A total of 27 species of bryophytes belonging to 20 genera and 12 families were found in 5 land use types,including 1 family,1 genera and 1 species of liverwort taxa,11 families,19 genera and 26 species of moss taxa.By comparing the diversity indices of bryophytes in different land use types,it was found that the diversity of bryophytes in abandoned wasteland was the highest and that in quarries was the lowest.This indicates that frequent human production activities have a negative impact on bryophyte diversity;(7)Wefts bryophytes were dominant,followed by short turfs,Tall turfs,cushion and mats,and no fans-type bryophytes were found.Wefts bryophytes occupy a large proportion in grazing land,quarry and abandoned land,while short turfs bryophytes occupy an absolute advantage in thorn pear plantation and maize land;(8)There are 59 communities in different land use types(thorn pear plantation,maize land,grazing land,quarry and abandoned wasteland),including 29 mixed communities and 30 pure communities.Except for thorn pear plantation and abandoned land,pure community dominated the other three plots,which indicated that thorn pear planting and abandoned cultivation have a certain reference value for ecological environment restoration in rocky desertification area.