Plant Population Structure and Species Diversity Status atTwo DisturbanceRegimes Within Mixed Forests and Sal Forests of Gorakhpur, India

摘要

This study of plant population structure and regeneration strategy of various woody species of mixed forests and sal forestscompares the effect of disturbance on the status of species population especially with reference to ramet vs. genet. The lessdisturbed forests were more dominated by sprouters and ramet producing species as compared to highly disturbed ones. Analysisof variance among the number of species falling under different regeneration categories, i.e., OS (Regenerating only through seeds),FS (Facultative sprouters), OR (Obligate sprouter), RP (Ramet producers) and SR (Storage roots) showed significant differences4, 3(F = 5.31) at p < 0.01.A total of 166 species was recorded in less disturbed mixed forest and only 48 species in highly disturbed sal forest stand. Atlow disturbance, the trees like Mallotus philippensis, Holarrhena antidysenterica, Ficus glomerulata, Careya arborea andPongamia pinnata showed quite stable population structure. On the other hand, trees like Flacourtia indica, Carissa spinarum,Casearia tomentosa, Putranjiva roxburghii, Antidesma ghaesembilla and Cassia fistula, at high disturbance, were quite frequentas sprouts in mixed forests as compared to sal stands. In presence of recurrent disturbance, the common undertrees and lianasreadily acquired shrubby habit. Most of the obligate sprouter and ramet producers formed several sub-populations or metapopulations(patronized by a single genet).Population structure for tree species was stable in less disturbed forest stands having large number of individuals of lower girthclasses. Except for sal, most of the tree species showed reverse J-shaped population structure. The ramet and genet density, alongthe age series, was positively correlated in sal forests and negatively correlated in mixed forests. Proportion of obligate sprouterswas quite similar for less disturbed sal and mixed forests when the whole complex of a single genet was treated as only oneindividual. The diversity index (H) was always greater when a genet complex was treated as single individual than in case wheneach ramet, distinct at soil surface, were treated as separate individuals irrespective of the forest type and degree of disturbance.Further, this index was always greater for forest communities facing low disturbance. The similarity index values ranged between0.46 to 0.84 for any two forest stands. The information on the impact of disturbance and heat stress of different degrees on theregeneration strategy and population structure of woody plants maybe helpful for adapting conservation and diversitymaintenancestrategy within the regional tropical forest ecosystem.