nginx系统挂网站，为何我的conf文件没有logformat？

server {
        listen       80;
        server_name  localhost;
        index index.html index.htm index.php;
        root /alidata/www/default;
        location ~ .*\.(php|php5)?$
        {
                #fastcgi_pass  unix:/tmp/php-cgi.sock;
                fastcgi_pass  127.0.0.1:9000;
                fastcgi_index index.php;
                include fastcgi.conf;
        }
        location ~ .*\.(gif|jpg|jpeg|png|bmp|swf)$
        {
                expires 30d;
        }
        location ~ .*\.(js|css)?$
        {
                expires 1h;
        }
        #α¾²Ì¬¹æÔò
        include /alidata/server/nginx/conf/rewrite/default.conf;
        access_log  /alidata/log/nginx/access/default.log;
}

以上copy了default.conf后的，没有log_format;为什么呢呢？