McBroom Matthew W, Beasley R Scott, Chang Mingteh, Ice George G
Arthur Temple College of Forestry and Agriculture, Stephen F. Austin State University, Box 6109 SFA Station, Nacogdoches, TX 75962, USA.
J Environ Qual. 2008 Jan 4;37(1):114-24. doi: 10.2134/jeq2006.0552. Print 2008 Jan-Feb.
Nine small (2.5 ha) and four large (70-135 ha) watersheds were instrumented in 1999 to evaluate the effects of silvicultural practices with application of best management practices (BMPs) on stream water quality in East Texas, USA. Two management regimes were implemented in 2002: (i) conventional, with clearcutting, herbicide site preparation, and BMPs and (ii) intensive, which added subsoiling, aerial broadcast fertilization, and an additional herbicide application. Watershed effects were compared with results from a study on the same small watersheds in 1981, in which two combinations of harvesting and mechanical site preparation without BMPs or fertilization were evaluated. Clearcutting with conventional site preparation resulted in increased nitrogen losses on the small watersheds by about 1 additional kg ha(-1) each of total Kjeldahl nitrogen (TKN) and nitrate-nitrogen (NO(3)-N) in 2003. First-year losses were not significantly increased on the large watershed with a conventional site preparation with BMPs. Fertilization resulted in increased runoff losses in 2003 on the intensive small watersheds by an additional 0.77, 2.33, and 0.36 kg ha(-1) for NO(3)-N, TKN, and total phosphorus, respectively. Total loss rates of ammonia nitrogen (NH(4)-N) and NO(3)-N were low overall and accounted for only approximately 7% of the applied N. Mean loss rates from treated watersheds were much lower than rainfall inputs of about 5 kg ha(-1) TKN and NO(3)-N in 2003. Aerial fertilization of the 5-yr-old stand on another large watershed did not increase nutrient losses. Intensive silvicultural practices with BMPs did not significantly impair surface water quality with N and P.
1999年，对9个小流域（2.5公顷）和4个大流域（70 - 135公顷）进行了监测，以评估在美国得克萨斯州东部实施森林经营措施并应用最佳管理措施（BMPs）对溪水水质的影响。2002年实施了两种管理方式：（i）传统方式，包括皆伐、除草剂整地以及BMPs；（ii）集约方式，增加了深松、空中撒播施肥以及额外的除草剂施用。将流域的影响与1981年对相同小流域的一项研究结果进行了比较，在该研究中评估了不使用BMPs或施肥的采伐和机械整地的两种组合。2003年，传统整地的皆伐导致小流域的氮损失增加，总凯氏氮（TKN）和硝态氮（NO₃ - N）分别额外增加约1千克/公顷。在采用BMPs进行传统整地的大流域，第一年的损失没有显著增加。施肥导致2003年集约经营的小流域径流损失增加，硝态氮、总凯氏氮和总磷分别额外增加0.77、2.33和0.36千克/公顷。氨氮（NH₄ - N）和硝态氮的总损失率总体较低，仅占施用氮的约7%。2003年，处理过的流域的平均损失率远低于约5千克/公顷的总凯氏氮和硝态氮的降雨输入量。在另一个大流域对5年生林分进行空中施肥并没有增加养分损失。采用BMPs的集约森林经营措施对地表水的氮和磷质量没有显著损害。
