How do reformed theologians reconcile John 15:2 with “once saved always saved"?

> Every branch in me (εν έμοι ) that beareth not fruit, he taketh it away: and every branch that beareth fruit, he [the Father, v1] cleanseth it, that it may bear more fruit. (John 15:2, ASV) Some reformed like James White say that once someone is “in Christ” they are eternally saved. But Jesus said that some branches in him that don't bear fruit will be removed from him and burned. (15:5) How do reformed theologians reconcile John 15:2 with the doctrine of “once saved always saved"? ----- 3) the phrase en Christo (in Christ) or its equivalent in Him, is central to Paul’s thought. All of salvation takes place only “in Christ.” (https://reformedspirit.blogspot.com/2015/08/god-is-redeeming-for-himself-people-and.html?m=1)