There are many things you can do to help your forest respond to dry times. The combination of warmer than normal temperatures and less precipitation contribute to low soil moisture—which is a major cause of water stress in trees and forests. Being aware of the signs of drought stress, managing tree density, and managing and planting appropriate species for site conditions can go a long way in improving a forest’s resilience to climate change.
It’s also important to maintain a diversity of tree species and age classes, retain large woody debris, and encourage a rich understory of native shrubs and flowers to contribute to soil moisture retention and overall forest ecosystem health. Below are some tips for helping trees and the entire forest adapt to drier, warmer times.
Recognizing drought stress in trees
- Broadleaf trees will display obvious signs of water deficit and drought stress. Keep in mind that drought stress from the previous year may have effects that continue on into the following years. During dry periods, you may see:
- Wilting of leaves, which may become permanent and eventually kill the tree
- Warped, scorched (brown), or curled leaves that fall excessively from the tree
- Die-back or decline, or death of the crown of the tree
- Conifers do not display wilting in the same way hardwoods do. Common symptoms for conifers include:
- Yellowing/red second-year needles that drop prematurely (though yellowing needles indicate drought stress, this does not necessarily indicate mortality)
- Bark beetle infestations, which prey on weakened trees
- Die-back or decline, or death of the crown of the tree
Understand the effects of drought stress on trees
- In normal conditions, plants release water through the stomata, small holes located on the leaf of the plant. This process, called transpiration, will occur during the day and eventually cease at night. During drought, however, the plant closes the stomata and ceases transpiration in an effort to retain the now-limited water in the soil. After prolonged periods of drought and no transpiration, photosynthesis eventually stops, which causes energy loss and eventual death among trees. For more information on transpiration, click here.
- Diameter growth is affected by yearly water availability as well. The season’s tree rings will vary depending on water, and a drought can almost completely halt width-wise growth during the dry period and perhaps a few years beyond.
During prolonged drought, trees that experience die-back may either become dormant or die. It can be difficult to tell the difference visually, but two tests can be implemented to assist in differentiating a dead tree from one that is simply dormant:
- Collect some small twigs about one-eighth inch in diameter and try to break the individual twigs. If the twigs snap easily and appear dry, the tree may be dead. If the twigs bend and don’t break with a snap, the tree may still be alive.
- Use your fingernail to scrape bark from a small twig or branch. If the tissue under the bark is green and moist, the tree may still be alive. If you are unsure of these results, you should wait until the drought ends, and the tree may sprout a new crop of leaves. (Source)
What you can do for your forest during a drought
- Watering: Watering trees, especially younger trees and saplings planted in the last 2 years, is an optional treatment for drought stress. Obviously, acres of forestland cannot be watered, but if you are especially concerned about a small grouping of trees or young saplings, watering may be a good option for you. Note: trees do not grow well in constantly wet soil, so make sure to let the earth dry out in-between waterings. Here are some considerations and observations from a project Amy Grotta of OSU Extension carried out last year on Douglas-fir seedlings.
- Mulch: Leaves or chipped wood can be used as mulch and will help retain soil moisture. Mulch can also regulate soil temperature, which is essential for root-growth. Make sure to place the mulch 4-6″ deep and at least 4″ away from the base of the tree.
- Reduce competition: Removing weeds, invasive species, and other competing vegetation will increase the amount of nutrients available to trees, thereby increasing the likelihood of tree survival, especially for seedlings.
- Pruning, perhaps: If disease has stricken your trees already due to drought stress, prune limbs of trees where obvious cankers are present to prevent further spreading of the pathogen.
What you can do for your forest in the future
- Plant in the fall: In the Pacific Northwest, planting in the fall as opposed to the spring is particularly advantageous. The main reason for this is due to the extended growing period for sapling roots. The deeper and wider a tree’s root system, the better water uptake it will have. This increases its chance for survival through water-limited periods. If a seedling is planted in the fall, this gives the tree time to adjust from transplant shock and put energy into root growth. If a tree is planted in spring, growth efforts are directed to leaf area, and it is less-prepared for dry summer weather.
- Consider your soil temperatures: Although ground temperatures can get too low for saplings to survive, temperatures in excess of 85 degrees F are too high for many species of trees such Douglas-fir, and this will inhibit growth. In general, most PNW species do best in temperatures of 68-70 degrees, although Ponderosa pines may prefer the temperature slightly warmer (source). In very dry times, it is probably best for seedlings if they have some cover provided by mature trees to ensure that the soil does not get too hot and/or too dry. Different soil types also have different capacities to retain moisture and nutrients. For example, soil filled with clay has the best ability to hold water, but it is slow to drain and air cannot access the roots well, whereas sandy soil does not retain moisture well but has good aeration.
- Right tree, right site: Knowing the environments in which individual species grow best is vital to success of the tree in general. This guide provided by WSU Extension provides incredibly useful information on the environments in which individual native species thrive and the identification of these species. Planting drought-tolerant tree species—especially on fast-draining soils and south-facing aspects—is an important strategy. Talk to your nursery about the appropriate seed zone for your seedlings.
- Thin highly stocked stands to reduce water stress: Denser forests are more prone to drought stress. As forest ecologist, Derek Churchill noted recently: Thinning stands reduces competition for water and nutrients, and thus the remaining trees have more resources to withstand drought, insects, and root rot. Thinning also benefits wildlife habitat by increasing non-tree plant diversity and abundance-
More resources on climate and drought adaptation and your forest
NW Climate Hub – https://www.climatehubs.oce.usda.gov/hubs/northwest
USDA portal for science-based Northwest-specific information and technologies to assist with climate-informed decision making.
Seedlot Selection Tool – https://seedlotselectiontool.org/sst/
Web-based mapping application that can be used to map current or future climates based on different climate change scenarios to inform the selection of seedlings for tree planting as part of reforestation and restoration efforts.
NW Climate Toolbox – https://climatetoolbox.org/
Suite of online tools to put a variety of climate data and information in reach of organizations and people for site specific locations – including: historical climate variability, temperature and precipitation normal, streamflow projections, climate projections, and data for Tribal Lands.
Adaptation Partners – http://adaptationpartners.org/
Researchers and resource managers provide scientific information on climate change effects and adaptation for specific regions in the Northwest and Intermountain West.
Climate Mapper – http://www.climatemapper.org/
The Nature’s Stage Climate Mapper allows users to explore the geoclimatic stability of HUC5 watersheds within the Pacific Northwest.
AdaptWest – https://adaptwest.databasin.org/
AdaptWest is a spatial database designed to help land management agencies and other organizations implement strategies that promote resilience, protect biodiversity, and conserve and enhance the adaptation potential of natural systems in the face of a changing climate.
Climate Impact Groups at UW – https://cig.uw.edu/
Providers of primary science and decision making tools.
Climate Impact Research Consortium at OSU – https://pnwcirc.org/
Primary science provider and resource tool developer.
Adaptation Workbook – https://adaptationworkbook.org/
Adaptation Clearinghouse – https://www.adaptationclearinghouse.org/
Brooks, R., Meinzer, F., Coulombe, R., & Gregg, J. (2002, October 1). Hydraulic redistribution of soil water during summer drought in two contrasting Pacific Northwest coniferous forests.
Fair, Barbara (March 2013). Coping With Drought.
Lopushinsky, W., & Max, A. (1990, May 10). Effect of soil temperature on root and shoot growth and on budburst timing in conifer seedling transplants.
Texas A&M Forest Service (n.d.). Effects of Drought Stress on Trees and Landscape Plants.
Header image by Matt Freeman-Gleason
Icons by xnimrodx via flaticon.com
Kuna mambo mengi unayoweza kufanya ili kusaidia msitu wako kukabiliana na majira ya ukame. Mchanganyiko wa joto kuliko kawaida na mvua kidogo huchangia unyevu wa chini wa udongo - ambayo ni sababu kuu ya shida ya maji katika miti na misitu. Kujua ishara za ukame, kudhibiti unene wa miti, na kusimamia na kupanda spishi zinazofaa kwa hali ya eneo inaweza kwenda mbali katika kuboresha upinzani wa msitu kwa mabadiliko ya hali ya hewa. Pia ni muhimu kudumisha utofauti wa spishi za miti na madarasa ya umri, kudumisha mabaki makubwa ya mbao, na kuhamasisha chini ya matawi ya mimea ya asili na maua ili kuchangia kuhifadhi unyevu wa udongo na afya ya mazingira ya msitu kwa ujumla. Hapa chini kuna vidokezo kadhaa vya kusaidia miti na msitu wote kukabiliana na nyakati kavu, zenye joto. Kutambua mvua msongamano katika miti - Broadleaf miti itaonyesha ishara dhahiri ya upungufu wa maji na mvua msongamano. Kumbuka kwamba ukame wa mwaka uliopita unaweza kuwa na athari ambazo huendelea katika miaka inayofuata. Katika kipindi cha ukame, unaweza kuona: - Kufifia kwa majani, ambayo yanaweza kuwa ya kudumu na hatimaye kuua mti - Majani yaliyopindika, yaliyochomwa (kahawia), au yaliyopindika ambayo huanguka kupita kiasi kutoka kwenye mti - Kufa nyuma au kupungua, au kifo cha taji la mti - Miti ya koni haionyeshi kuoza kwa njia ileile ambayo miti ngumu hufanya. Mimea ya coniferous ina dalili za kawaida kama vile: - Yellowing au nyekundu, na kuanguka kabla ya wakati (ingawa nyuzi ya manjano inaonyesha ukame, hii haimaanishi kifo) - Bark beetle infestations, ambayo hunyanyua miti dhaifu - Kufa nyuma au kupungua, au kifo cha taji la mti - Kuelewa athari za ukame juu ya miti - Katika hali ya kawaida, mimea kutoa maji kupitia stomata, mashimo madogo iko juu ya majani. Utaratibu huo, unaoitwa transpiration, utatokea mchana na hatimaye utasimama usiku. Wakati wa ukame, mmea hufunga stomata na kuacha kupumua ili kuhifadhi maji yaliyopo katika udongo. Baada ya kipindi kirefu cha ukame na kutokuwa na mvua, photosynthesis hatimaye huacha, na hilo husababisha kupoteza nishati na hatimaye kifo cha miti. Kwa habari zaidi juu ya transpiration, bonyeza hapa. - Ukuaji wa kipenyo huathiriwa na upatikanaji wa maji ya kila mwaka pia. Mzunguko wa miti wa msimu utabadilika kulingana na maji, na ukame unaweza karibu kabisa kusimamisha ukuaji wa upana wakati wa kipindi cha ukame na labda miaka michache baadaye. Wakati wa ukame wa muda mrefu, miti inayokufa inaweza kuwa imezimia au kufa. Ni vigumu kugundua tofauti ya mti huo, lakini kuna njia mbili za kuutambua: kukusanya matawi madogo yenye kipenyo cha sentimeta moja na kujaribu kuuvunja. Ikiwa matawi hayo huvunjika kwa urahisi na kuonekana kuwa kavu, huenda mti huo ukafa. Ikiwa matawi hayo yanainama na hayavunjiki kwa ghafula, huenda mti huo ukaendelea kuishi. - Tumia kucha yako kukata magamba kutoka kwenye tawi dogo au tawi. Ikiwa tishu iliyo chini ya ganda ni ya kijani-kibichi na yenye unyevunyevu, huenda mti huo bado uko hai. Ikiwa una shaka juu ya matokeo haya, unapaswa kusubiri mpaka ukame ukamalizike, na mti unaweza kuchipua mazao mapya ya majani. "Kama vile ilivyoelezwa katika makala hii, ""Kinywaji cha maji: Miti ya maji, hasa miti ya vijana na miche iliyopandwa katika miaka miwili iliyopita, ni matibabu ya hiari ya mkazo wa ukame.""" Kwa kweli, hekta za misitu haziwezi kunyunyizia maji, lakini ikiwa una wasiwasi hasa kuhusu kikundi kidogo cha miti au vichaka vidogo, kunyunyizia maji huenda ikawa chaguo zuri kwako. Kwa sababu miti haikua vizuri katika udongo wenye unyevunyevu, hakikisha kwamba ardhi imekauka kati ya maji. "Hii ni moja ya ""mfano"" wa utafiti uliofanywa na Amy Grotta, Mkurugenzi wa Uendelezaji wa Chuo Kikuu cha Ohio, juu ya mimea ya Douglas fir." - Mulch: Majani au mbao zilizokatwa zinaweza kutumiwa kama mulch na itasaidia kuhifadhi unyevu wa udongo. Mulch pia inaweza kudhibiti joto la udongo, ambalo ni muhimu kwa ukuzi wa mizizi. Kuhifadhi mchanga kwa kina cha 4-6′′ na angalau 4′′ kutoka chini ya mti. - Kupunguza ushindani: Kuondoa magugu, spishi za uvamizi, na mimea mingine inayoshindana itaongeza kiasi cha virutubisho vinavyopatikana kwa miti, na hivyo kuongeza uwezekano wa mti kuishi, haswa kwa ajili ya miche. - Kupunguza, labda: Ikiwa ugonjwa umepiga miti yako tayari kwa sababu ya mkazo wa ukame, kupunguza matawi ya miti ambapo cankers dhahiri zipo ili kuzuia kuenea zaidi kwa vimelea. Kwa nini mimea ya msitu inapaswa kupandwa katika majira ya baridi kali? Sababu kuu ya jambo hilo ni kwa sababu ya muda mrefu wa kukua kwa mizizi ya mti. Kadiri mfumo wa mizizi ya mti ulivyo wa kina na mpana, ndivyo utakavyopokea maji vizuri zaidi. Hilo huongeza uwezekano wake wa kuishi katika vipindi visivyo na maji mengi. Mti huo unapoanza kupandwa wakati wa vuli, unapata muda wa kurekebisha hali yake na kuongeza nguvu zake. Mti unaopandwa wakati wa majira ya kuchipua, unakuwa na majani mengi na haujakabili hali ya hewa ya kiangazi. "Hata hivyo, "" ingawa joto la ardhi linaweza kuwa la chini sana hivi kwamba miche haiwezi kuishi, joto la zaidi ya nyuzi 85 F ni la juu sana kwa spishi nyingi za miti kama vile Douglas fir, na hilo litazuia ukuzi." Kwa ujumla, aina nyingi za PNW hufanya vizuri katika joto la digrii 68-70, ingawa Ponderosa pines inaweza kupendelea joto la joto zaidi. Katika nyakati kavu sana, ni uwezekano bora kwa ajili ya seedlings kama wao kuwa na baadhi ya kifuniko zinazotolewa na miti kukomaa kuhakikisha kwamba udongo haina kupata joto sana na au kavu sana. Aina tofauti-tofauti za udongo pia zina uwezo tofauti wa kuhifadhi unyevu na virutubisho. Kwa mfano, udongo uliojaa udongo una uwezo mkubwa wa kuhifadhi maji, lakini ni polepole kuondoa maji na hewa haiwezi kufikia mizizi vizuri, wakati udongo wenye mchanga hauzuii unyevu vizuri lakini una hewa nzuri. - Mti sahihi, mahali sahihi: Kujua mazingira ambayo spishi za mtu binafsi hukua vizuri ni muhimu kwa mafanikio ya mti kwa ujumla. Mwongozo huu uliotolewa na WSU Extension hutoa habari muhimu sana juu ya mazingira ambayo spishi za asili zinafanikiwa na utambulisho wa spishi hizi. Kupanda aina za miti sugu kwa ukame - hasa kwenye udongo unaotiririka haraka na sehemu zinazokabili kusini - ni mkakati muhimu. Zungumza na mzazi wako kuhusu eneo linalofaa la kupanda mbegu kwa ajili ya miche yako. - Mimea nyembamba yenye idadi kubwa ya wanyama ili kupunguza mkazo wa maji: Misitu mikubwa zaidi huwa na mkazo wa ukame. "Mtaalamu wa mazingira Derek Churchill alisema hivi hivi hivi hivi karibuni: ""Kupungua kwa miti hupunguza ushindani wa maji na virutubisho, na hivyo miti iliyobaki ina rasilimali zaidi za kukabiliana na ukame, wadudu, na kuoza kwa mizizi." "Kupunguza kwa idadi ya miti na mimea ya asili ni muhimu kwa ajili ya maendeleo ya mazingira ya mazingira na mazingira ya mazingira ya mazingira, na ""Nordwest Climate Hub"" ni tovuti ya USDA ya habari na teknolojia ya Northwest-specific kusaidia na maamuzi ya hali ya hewa." Seedlot Selection Tool (SEL) ni programu ya ramani ya mtandao ambayo inaweza kutumika kwa ramani ya hali ya hewa ya sasa au ya baadaye kulingana na matukio tofauti ya mabadiliko ya hali ya hewa ili kuelezea uteuzi wa mbegu kwa ajili ya kupanda miti kama sehemu ya juhudi za ukarabati na ukarabati. "Kifaa cha ""NW Climate Toolbox"" ni seti ya zana za mtandaoni za kuweka data mbalimbali za hali ya hewa na habari katika kufikia mashirika na watu kwa maeneo maalum ya tovuti, ikiwa ni pamoja na: mabadiliko ya hali ya hewa ya kihistoria, joto na mvua ya kawaida, makadirio ya mtiririko, makadirio ya hali ya hewa, na data kwa ajili ya ardhi ya kikabila." "Mashirika ya Adaptation: ""Wanafunzi na wasimamizi wa rasilimali hutoa habari za kisayansi juu ya athari za mabadiliko ya hali ya hewa na marekebisho kwa mikoa maalum katika Kaskazini Magharibi na Magharibi ya Intermountain." "Kama ilivyoelezwa hapo juu, ""Mapper ya hali ya hewa ya asili"" inatoa fursa kwa watumiaji kuchunguza utulivu wa hali ya hewa ya maji ya HUC5 katika Kaskazini Magharibi mwa Pasifiki." AdaptWest ni hifadhidata ya kijiografia iliyoundwa kusaidia mashirika ya usimamizi wa ardhi na mashirika mengine kutekeleza mikakati ambayo huendeleza upinzani, kulinda utofauti wa kibiolojia, na kuhifadhi na kuboresha uwezo wa marekebisho ya mifumo ya asili katika uso wa hali ya hewa inayobadilika. Kikundi cha Athari za Hali ya Hewa katika UW <unk> https: cig.uw.edu <unk> Watoaji wa sayansi ya msingi na zana za kufanya maamuzi. Utafiti wa Athari za Hali ya Hewa katika OSU (Climate Impact Research Consortium) ni shirika la utafiti wa hali ya hewa la Marekani (CIRC) ambalo linashirikiana na Chuo Kikuu cha Ohio (OSU) na shirika la utafiti wa hali ya hewa (CIRC) katika Chuo Kikuu cha Ohio (OSU). "Kama ilivyoelezwa katika kitabu cha Adaptation Workbook, ""Adaptation Clearinghouse"" ni ""Mfumo wa Uhakiki wa Uhakiki wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika wa Uhakika.""" (Mwanzo 1, 2002) Ugawaji wa maji ya udongo wakati wa ukame wa majira ya joto katika misitu miwili ya coniferous ya Kaskazini Magharibi mwa Pasifiki. "Barbara, ""Mwanamke wa Haki"" (Mashariki ya Kati, 2013) " Kushinda Ukame. Lopushinsky, W., na Max, A. (Mwezi wa 5, 1990) Athari ya joto la udongo juu ya mzizi na kupanda kwa shina na juu ya wakati wa budburst katika kupandikiza mbegu za conifer. Huduma ya Misitu ya Texas A&M Athari za Ukame juu ya Miti na Mimea ya Mazingira. Picha ya kichwa na Matt Freeman-Gleason Icons na xnimrodx kupitia flaticon.com