Cho \u0111\u1ebfn nay, r\u1eebng nhi\u1ec7t \u0111\u1edbi ch\u00e2u Phi m\u1edbi ch\u1ec9 l\u00e0 \u0111\u1ed1i t\u01b0\u1ee3ng khai th\u00e1c v\u1eeba v\u00e0 nh\u1ecf, theo th\u1ee9 t\u1ef1 t\u1eebng c\u00e2y\/ ha. Ki\u1ec3u khai th\u00e1c ch\u1ecdn n\u00e0y n\u00e0y kh\u00f4ng thay \u0111\u1ed5i c\u1ea5u tr\u00fac r\u1eebng n\u1ebfu kh\u00f4ng l\u1eb7p l\u1ea1i trong th\u1eddi gian qu\u00e1 ng\u1eafn. Tuy nhi\u00ean, vi\u1ec7c khai th\u00e1c qu\u00e1 m\u1ee9c l\u00e0m thi\u1ec7t h\u1ea1i nghi\u00eam tr\u1ecdng \u0111\u1ebfn l\u00e2m ph\u1ea7n. \u0110i\u1ec1u quan tr\u1ecdng l\u00e0 gi\u1edbi h\u1ea1n s\u1ed1 c\u00e2y c\u00f3 th\u1ec3 khai th\u00e1c\/ ha \u0111\u1ec1 ph\u00f2ng s\u1ef1 suy tho\u00e1i v\u1ec1 l\u00e2u d\u00e0i c\u1ee7a l\u00e2m ph\u1ea7n. M\u1eb7t kh\u00e1c ph\u1ea3i d\u1ef1 \u0111o\u00e1n \u0111\u01b0\u1ee3c s\u1ed1 l\u01b0\u1ee3ng c\u00e2y d\u01b0 c\u00f2n nguy\u00ean v\u1eb9n sau m\u1ed9t \u0111\u1ee3t khai th\u00e1c v\u1edbi c\u01b0\u1eddng \u0111\u1ed9 cho ph\u00e9p, l\u00e0m c\u01a1 s\u1edf t\u00ednh to\u00e1n vi\u1ec7c tu b\u1ed5 v\u1ed1n r\u1eebng. C\u1ea7n x\u00e1c \u0111\u1ecbnh c\u00e1c th\u00f4ng s\u1ed1 \u0111i\u1ec1u ch\u1ebf r\u1eebng nh\u01b0: chu k\u1ef3, \u0111\u01b0\u1eddng k\u00ednh khai th\u00e1c t\u1ed1i thi\u1ec3u.<\/p>\n
B\u1ea3n ghi ch\u00e9p n\u00e0y ghi l\u1ea1i nh\u1eefng s\u1ef1 li\u00ean quan gi\u1eefa nh\u1eefng thi\u1ec7t h\u1ea1i do khai th\u00e1c v\u00e0 s\u1ed1 c\u00e2y ch\u1eb7t h\u1ea1\/ ha. S\u1ef1 li\u00ean quan n\u00e0y \u0111\u00e3 \u0111\u01b0\u1ee3c t\u00ednh to\u00e1n theo c\u00e1c s\u1ed1 li\u1ec7u v\u1ec1 \u0111\u1ea5t c\u1ee7a d\u1ef1 \u00e1n ECOFAC \u1edf r\u1eebng N\u01a1-g\u00f4-t\u00f4 (C\u1ed9ng ho\u00e0 Trung Phi).<\/p>\n
C\u1ea3nh quan r\u1eebng N\u01a1-g\u00f4- t\u00f4<\/p>\n
Trong gi\u1ea5y ph\u00e9p khai th\u00e1c, r\u1eebng r\u1eadm \u1ea9m gi\u00e0u M\u00e9liacees kh\u00f4ng \u0111\u01b0\u1ee3c khai th\u00e1c, tr\u1eeb m\u1ed9t ph\u1ea7n nh\u1ecf c\u1ee7a di\u1ec7n t\u00edch. \u0110i\u1ec1u cho ph\u00e9p n\u00e0y l\u00e0 ti\u1ec1n \u0111\u1ec1 c\u1ee7a m\u1ed9t k\u1ebf ho\u1ea1ch \u0111i\u1ec1u ch\u1ebf r\u1eebng, \u0111\u01b0\u1ee3c ti\u1ebfn h\u00e0nh v\u00e0o n\u0103m 1997. Nh\u1eefng k\u1ebft qu\u1ea3 d\u01b0\u1edbi \u0111\u00e2y \u0111\u01b0\u1ee3c r\u00fat ra t\u1eeb m\u1ed9t v\u00f9ng \u0111\u1eb7c bi\u1ec7t gi\u00e0u r\u1eebng, \u1edf \u0111\u00e2y ng\u01b0\u1eddi khai th\u00e1c c\u00f3 th\u1ec3 l\u1ea5y ra t\u1eeb 0,4 – 3,3 c\u00e2y\/ ha (95% sapellis). \u0110\u01b0\u1eddng k\u00ednh trung b\u00ecnh c\u00e1c c\u00e2y ch\u1eb7t h\u1ea1 l\u00e0 118cm. \u0110\u01b0\u1eddng k\u00ednh t\u1ed1i thi\u1ec3u \u0111\u01b0\u1ee3c ph\u00e9p khai th\u00e1c l\u00e0 80cm, trong khi \u0111\u00f3 r\u1ea5t \u00edt c\u00e2y ch\u1eb7t h\u1ea1 c\u00f3 \u0111\u01b0\u1eddng k\u00ednh d\u01b0\u1edbi 90 cm.<\/p>\n
Ph\u01b0\u01a1ng ph\u00e1p th\u1ef1c hi\u1ec7n:<\/p>\n
D\u1ef1 \u00e1n ECOFAC \u0111\u00e3 ti\u1ebfn h\u00e0nh v\u1ebd b\u1ea3n \u0111\u1ed3 c\u00e1c v\u1ecb tr\u00ed ch\u1eb7t h\u1ea1 v\u00e0 c\u00e1c con \u0111\u01b0\u1eddng v\u1eadn xu\u1ea5t tr\u00ean 8 kho\u1ea3nh r\u1eebng r\u1ed9ng 25ha v\u00e0 tr\u00ean 6 kho\u1ea3nh r\u1eebng r\u1ed9ng 12,5ha. Trong d\u1ef1 \u00e1n, ng\u01b0\u1eddi ta tr\u00ecnh b\u00e0y 14 \u0111i\u1ec3m kh\u00e1c nhau xu\u1ea5t x\u1ee9 t\u1eeb m\u1ed9t l\u00e2m ph\u1ea7n \u0111\u1ed3ng nh\u1ea5t v\u1ec1 ph\u01b0\u01a1ng di\u1ec7n th\u00e0nh ph\u1ea7n th\u1ef1c v\u1eadt ch\u00ed.<\/p>\n
K\u1ef9 thu\u1eadt v\u1eadn xu\u1ea5t, k\u1ef9 thu\u1eadt t\u1ec9a th\u01b0a c\u00e2y( c\u0169ng nh\u01b0 lo\u00e0i) t\u01b0\u01a1ng t\u1ef1 nh\u01b0 nhau.<\/p>\n
K\u1ebft qu\u1ea3<\/p>\n
B\u1eb1ng m\u1ed9t \u0111\u1ed3 th\u1ecb \u0111\u01b0\u1eddng cong v\u1edbi hai th\u00f4ng s\u1ed1 c\u00f3 th\u1ec3 quan s\u00e1t \u0111\u01b0\u1ee3c s\u1ed1 ph\u1ea7n tr\u0103m di\u1ec7n t\u00edch thi\u1ec7t h\u1ea1i do ch\u1eb7t h\u1ea1 v\u00e0 v\u1eadn xu\u1ea5t li\u00ean quan \u0111\u1ebfn s\u1ed1 c\u00e2y ch\u1eb7t h\u1ea1.<\/p>\n
Di\u1ec7n t\u00edch \u1ea3nh h\u01b0\u1edfng do khai th\u00e1c:<\/p>\n
S(%)= 100(1 – 1\/[ 1 + 0,186N ]0,465 <\/sup>), v\u1edbi N = s\u1ed1 c\u00e2y ch\u1eb7t h\u1ea1\/ ha.<\/p>\n Nh\u01b0 v\u1eady, s\u1ed1 c\u00e2y khai th\u00e1c c\u00e0ng nhi\u1ec1u th\u00ec ph\u1ea7n tr\u0103m di\u1ec7n t\u00edch bi\u1ebfn \u0111\u1ed9ng c\u00e0ng t\u0103ng. D\u00e1ng c\u1ee7a \u0111\u01b0\u1eddng cong \u0111\u1ed3 th\u1ecb cho th\u1ea5y r\u1eb1ng khi s\u1ed1 c\u00e2y ch\u1eb7t h\u1ea1\/ ha t\u0103ng, c\u00e1c l\u1ed7 th\u1ee7ng c\u00f3 xu h\u01b0\u1edbng t\u0103ng l\u00ean v\u00e0 di\u1ec7n t\u00edch c\u1ee7a m\u1ed9t l\u1ed7 th\u1ee7ng do c\u00e2y b\u1ecb ch\u1eb7t h\u1ea1 gi\u1ea3m \u0111i theo c\u01b0\u1eddng \u0111\u1ed9 khai th\u00e1c.<\/p>\n Ng\u01b0\u1eddi ta c\u00f3 th\u1ec3 nh\u1eadn th\u1ea5y tr\u00ean th\u1ef1c \u0111\u1ecba trong m\u1ed9t \u0111\u1ee3t khai th\u00e1c c\u01b0\u1eddng \u0111\u1ecd cao \u0111\u00e3 t\u1ea1o ra nh\u1eefng kho\u1ea3nh r\u1eebng th\u01b0a l\u1edbn do ch\u1eb7t h\u1ea1 nhi\u1ec1u c\u00e2y g\u1ea7n nhau. Theo s\u1ed1 li\u1ec7u th\u1ef1c hi\u1ec7n tr\u00ean 100 ha, di\u1ec7n t\u00edch trung b\u00ecnh c\u00e1c l\u1ed7 th\u1ee7ng t\u0103ng theo c\u01b0\u1eddng \u0111\u1ed9 khai th\u00e1c.<\/p>\n K\u1ebft lu\u1eadn<\/p>\n Bi\u1ec3u \u0111\u1ed3 n\u00e0y \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u0111\u1ec3 t\u00ednh to\u00e1n th\u1eddi gian chu k\u1ef3 gi\u1eefa hai \u0111\u1ee3t khai th\u00e1c. K\u1ebft qu\u1ea3 l\u00e0 ng\u01b0\u1eddi \u0111i\u1ec1u ch\u1ebf r\u1eebng ph\u1ea3i \u01b0\u1edbc t\u00ednh \u0111\u01b0\u1ee3c s\u1ed1 c\u00e2y d\u01b0 c\u00f2n nguy\u00ean sau m\u1ed9t \u0111\u1ee3t khai th\u00e1c nh\u1eb1m t\u00ednh to\u00e1n \u0111\u01b0\u1ee3c vi\u1ec7c c\u1ea3i t\u1ea1o v\u1ed1n r\u1eebng. \u0110\u00e2y l\u00e0 m\u1ed9t trong nh\u1eefng y\u1ebfu t\u1ed1 c\u01a1 b\u1ea3n \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh nh\u1eefng th\u00f4ng s\u1ed1 \u0111i\u1ec1u ch\u1ebf r\u1eebng. H\u01a1n n\u1eefa, s\u1ef1 hi\u1ec3u bi\u1ebft v\u1ec1 nh\u1eefng thi\u1ec7t h\u1ea1i do s\u1ed1 c\u00e2y ch\u1eb7t h\u1ea1 cung c\u1ea5p m\u1ed9t s\u1ed1 li\u1ec7u quan tr\u1ecdng \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh s\u1ed1 c\u00e2y t\u1ed1i \u0111a c\u00f3 th\u1ec3 khai th\u00e1c\/ ha \u0111\u1ec3 \u0111\u1ec1 ph\u00f2ng s\u1ef1 t\u1ed5n th\u1ea5t v\u1ec1 l\u00e2u d\u00e0i c\u1ee7a l\u00e2m ph\u1ea7n.<\/p>\n Mai Th\u00e0nh<\/p>\n (L\u01b0\u1ee3c d\u1ecbch t\u1eeb ” Bois et For\u00eats des Tropipues<\/em>” No 264\/ 2000).****************************************<\/p>\n","protected":false},"excerpt":{"rendered":" Cho \u0111\u1ebfn nay, r\u1eebng nhi\u1ec7t \u0111\u1edbi châu Phi m\u1edbi ch\u1ec9 là \u0111\u1ed1i t\u01b0\u1ee3ng khai thác v\u1eeba và nh\u1ecf, theo th\u1ee9 t\u1ef1 t\u1eebng cây\/ ha. Ki\u1ec3u khai thác ch\u1ecdn này này không thay \u0111\u1ed5i c\u1ea5u trúc r\u1eebng n\u1ebfu không l\u1eb7p l\u1ea1i trong th\u1eddi gian quá ng\u1eafn. Tuy nhiên, vi\u1ec7c khai thác quá m\u1ee9c làm thi\u1ec7t h\u1ea1i nghiêm tr\u1ecdng \u0111\u1ebfn lâm ph\u1ea7n. \u0110i\u1ec1u quan tr\u1ecdng là gi\u1edbi h\u1ea1n s\u1ed1 cây có th\u1ec3 khai thác\/ ha \u0111\u1ec1 phòng s\u1ef1 suy thoái v\u1ec1 lâu dài c\u1ee7a lâm ph\u1ea7n.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[18],"tags":[],"_links":{"self":[{"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/posts\/8554"}],"collection":[{"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/comments?post=8554"}],"version-history":[{"count":2,"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/posts\/8554\/revisions"}],"predecessor-version":[{"id":19343,"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/posts\/8554\/revisions\/19343"}],"wp:attachment":[{"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/media?parent=8554"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/categories?post=8554"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/vafs.gov.vn\/vn\/wp-json\/wp\/v2\/tags?post=8554"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}