The phrase "addition a significant proportion" is not correct in English.
It seems to be missing a word, likely "of" after "addition." You can use a corrected version of this phrase when discussing the contribution or inclusion of a notable amount of something in a particular context.
Example: "In addition to the main findings, a significant proportion of the data supports our hypothesis."
Alternatives: "in addition to a considerable amount" or "along with a substantial portion."
In addition, a significant proportion of removed stem number may comprise broadleaved tree species, especially on fertile sites, but the dynamics of these mixed stands is beyond the scope of the present study of even-aged stand management.
In addition, a significant proportion of patients (40%) were documented to have cardiovascular co-morbidity, a group in which anaemia has been shown to be associated with worse survival and major adverse cardiovascular events.
In addition, a significant proportion of double-labeled neurons were counted in lamina I, representing 15±4% (n = 3 rats) of retrogradely labeled neurons in lamina I (Figure 5C).
In addition, a significant proportion of peritoneal macrophages and macrophages in local tissue appear to undergo mitosis in vivo, especially during inflammatory conditions [9], [10], [11], [12], [13], [14], [15], [16], [17], [18].
In addition, a significant proportion of urban dwellers also have access to smaller garden plots.
In addition, a significant proportion of them worked outside the nutrition sector.
In addition, for a significant proportion of students it was their first exposure to the deceased.
In addition to having a significant proportion of cold-adapted proteins encoded within its genome, P. halocryophilus Or1 also actively employs protein turnover at −15 °C likely to increase the conservation of biosynthetic precursors during slower growth rates.
On the other hand, with food intake, in addition to vegetables, a significant proportion is represented by dairy products, meat and bread, water and other beverages, which may contribute to increase values of metals intakes and THQ.
In addition to this, a significant proportion of the patients (68%) in the Dapueto study required assistance when completing the questionnaire.
In addition, we found a significant proportion of κ light chain restricted disease among MM patients with familial coaggregation of any hematologic malignancy.
