Inter-cluster competition and resource partitioning may govern the ecology of Frankia

Microbes live in a complex communal ecosystem. The structural complexity of microbial community reflects diversity, functionality, as well as habitat type. Delineation of ecologically important microbial populations along with exploration of their roles in environmental adaptation or host-microbe interaction has a crucial role in modern microbiology. In this scenario, reverse ecology (the use of genomics to study ecology) plays a pivotal role. Since the co-existence of two different genera in one small niche should maintain a strict direct interaction, it will be interesting to utilize the concept of reverse ecology in this scenario. Here, we exploited an 'R' package, the RevEcoR, to resolve the issue of co-existing microbes which are proven to be a crucial tool for identifying the nature of their relationship (competition or complementation) persisting among them. Our target organism here is Frankia, a nitrogen-fixing actinobacterium popular for its genetic and host-specific nature. According to their plant host, Frankia has already been sub-divided into four clusters C-I, C-II, C-III, and C-IV. Our results revealed a strong competing nature of CI Frankia. Among the clusters of Frankia studied, the competition index between C-I and C-III was the largest. The other interesting result was the co-occurrence of C-II and C-IV groups. It was revealed that these two groups follow the theory of resource partitioning in their lifestyle. Metabolic analysis along with their differential transporter machinery validated our hypothesis of resource partitioning among C-II and C-IV groups.

Individual tree basal area increment model for sessile oak (Quercus petraea (Matt.) Liebl.) in coppice-originated stands

In this study, the basal area increment models were developed to be both age dependent and independent with a stepwise multiple regression analysis for coppice-originated pure sessile oak stands in the Marmara region, which is located in north-western Turkey. Data was obtained from a total of 73 sample trees, which were sampled from coppice-originated pure sessile oak stands over different growth periods and in different site conditions. The most suitable competition variable was determined by examining the correlations between the 24 competition index values and calculated using different approaches and the basal area increment. The individual tree basal area increment models were obtained as functions of tree size, competition, age, and site characteristics. The most important variables that affect the basal area increment in the age-dependent model were the diameter at breast height (DBH) (36.1%), competition index (26.4%), and age (10%). For the age-independent model, the variables are the competition index (32.6%), DBH (30.3%), and the site index (3%), according to the relative importance values. The age-dependent model explained the increased variation of 10% and predicted a 13% decrease in error in the basal area increment than the age-independent model.

Influence of interspecies competition on beech (Fagus orientalis Lipsky) trees and some features of stand in mixed broad-leaved forest

Oriental beech (Fagus orientalis Lipsky) is one of the most important commercial tree species in the Hyrcanian region. This species is known to suffer from strong intra- and interspecific competition for above- and below-ground resources in temperate mixed stands. In the present study, a total of 26 beech trees and their surroundings trees as well as stand characteristics were evaluated for determining the interactions between them and competition index (CI) in mixed beech stand. The results showed that in mixed beech stand, there were positive correlation between CI and crown ratio and height/diameter (HD) ratio of target beech trees, but negatively correlated to crown length, crown width, crown area, and crown volume. Total height, DBH, and bole of target beech trees were decreased with increasing CI. Regression analysis showed that CI had positive significant correlation with functional group of forb richness. The target beech trees characteristics including HD ratio and crown ratio showed contrasting responses to some variables which were related to their known specific ecological strategies. This study demonstrates the different responses of target beech trees in overstory to competition in neighborhood conditions which are an important factor in retaining species coexistence and planning mixtures in temperate broad-leaved forests.